Tag Archives: #stemcells

Demystifying Healing Potential of Stem Cells (Medicine)

Mayo Clinic research has discovered proteins secreted by human stem cells that act as a “magic potion” to drive healing after a heart attack. The research uncovered that these cell-released regenerative particles harbor a pattern of functions mirrored in repair of the diseased heart, linking stem cell-transmitted information to the beneficial response of the recipient heart.

This proof-of-concept study on how cardiopoietic cells function is published in Stem Cells Translational Medicine.

Andre Terzic, M.D., Ph.D. © Mayo Clinic

“The study results indicate that the protein set that the cells export, known as their secretome, is responsible for providing restorative benefits,” says Andre Terzic, M.D., Ph.D., director of Mayo Clinic’s Center for Regenerative Medicine and senior author on the study. “Mapping the secretome may streamline the process of manufacturing regenerative therapeutics, rendering easier scalability and standardization, ultimately ensuring broader accessibility for patients.”

Hearts damaged by a heart attack have limited means for self-repair, often leading to failure with poor prognosis. Cardiopoietic cells, which are in phase III clinical trials, are a regenerative technology developed at Mayo Clinic showing signs of therapeutic benefit for heart failure patients. This latest research contributes to the understanding of how cardiopoietic stem cell therapy works.

D. Kent Arrell, Ph.D. © Mayo Clinic

“The discovery that the cardiopoietic cell secretome harbors restorative properties may be exploited to assess reparative potential prior to patient delivery. This approach could be extended to evaluate other cell types and their respective therapeutic capacity,” says D. Kent Arrell, Ph.D., first author on the study. “Bringing this new knowledge to the patient and broader clinical care is an ongoing endeavor.”

The research

The research team used state-of-the-art methodology to decode the identity, regulators and functionality of proteins secreted by human cardiopoietic stem cells. By comparing cells derived from responding versus nonresponding heart failure patients, researchers could distinguish between proteins that triggered healing versus those that didn’t. The functional imprint of this set of reparative proteins was echoed in the healing response of damaged hearts.

The functional imprint of this set of reparative proteins was echoed in the healing response of damaged hearts. © Mayo Clinic

Long-term vision

Preparation of stem cell therapies requires a lot of time and resources, with scalability and standardization recognized as major hurdles to clinical-grade supply. Researchers envision the newest discovery to contribute in advancing cell-free biotherapeutics that achieve healing properties in a cost-effective manner, offering ready-to-use solutions at point of care. A priority for the Center for Regenerative Medicine is to accelerate advanced biomanufacturing of innovative regenerative solutions.

Additional research is ongoing building on these findings. The J. Willard and Alice S. Marriott Foundation, the Mayo Clinic Van Cleve Cardiac Regenerative Medicine Program and National Institutes of Health (R01 HL134664) provided the primary funding for this research. Dr. Terzic is the Michael S. and Mary Sue Shannon Director, Mayo Clinic Center for Regenerative Medicine, and the Marriott Family Professor of Cardiovascular Research.

Reference: Arrell, DK, Crespo-Diaz, RJ, Yamada, S, et al. Secretome signature of cardiopoietic cells echoed in rescued infarcted heart proteome. STEM CELLS Transl Med. 2021; 1– 9. https://doi.org/10.1002/sctm.20-0509

Provided by Mayo Clinic

Developing Cancer Therapies With Stem Cells (Medicine)

The Shin Kaneko laboratory uses iPS cells to develop immune cells that attack colorectal cancer.

In recent years, adoptive cell transfer therapies have given cancer patients new hope and, in some cases, even cures. In these therapies, anti-cancer cells are processed and injected into patients. A new study by the Shin Kaneko Laboratory shows how iPS cells can be used to prepare even more potent adoptive cell transfer therapies for colorectal cancers.

In typical adoptive cell transfer therapies, the anti-cancer cells are taken directly from the patient. In all cases of cancer, the patient produces tumor-infiltrating lymphocytes that recognize and kill cancer cells. The problem is that the number of these lymphocytes is not high enough to stop the cancer from spreading.

CiRA Prof. Shin Kaneko explains that because of the recognition, most adoptive cell transfer therapies use these cells.

“The cells are collected and expanded, but the cells lose their potency. The ideal cells for the therapy would have juvenile properties. This means longer persistency and more proliferation. But these conditions are difficult to manufacture if using patient cells,” he said.

Kaneko added that along with these properties is that the lymphocytes target the cancer cells with high specificity. That is, they kill cancer cells but no healthy cells in the patient. iPS cells can provide the juvenile properties, but only certain iPS cells can also provide the specificity.

“Our hypothesis was that we could maintain the cancer specificity if we programmed tumor-infiltrating lymphocytes. Other reprogrammed cells would not have specificity,” said Takeshi Ito, the first author of the study.

Unlike other iPS cells, those made from reprogrammed tumor-infiltrating lymphocytes carried the surface receptors needed to recognize the cancer cells. To test their hypothesis, the researchers collected tumor-infiltrating lymphocytes sensitive for colorectal cancers. These cells were then reprogrammed into iPS cells and then differentiated back into tumor-infiltrating lymphocytes.

Notably, in contrast to the original tumor-infiltrating lymphocytes, those differentiated from iPS cells showed longer telomeres and persistency and more proliferation, resulting in superior cytotoxicity against the cancer cells.

“In adoptive cell transfer therapies, patient cells are safest but not always effective at killing the cancer. We are developing safe adoptive cell transfer therapies with iPS cells that have a higher killing effect,” said Kaneko.

Reference: Ito, T., Kawai, Y., Yasui, Y. et al. The therapeutic potential of multiclonal tumoricidal T cells derived from tumor infiltrating lymphocyte-derived iPS cells. Commun Biol 4, 694 (2021). https://doi.org/10.1038/s42003-021-02195-x

Provided by CIRA

Blood Stem Cells Make Brain Tumors More Aggressive (Medicine)

For the first time, scientists from the German Cancer Consortium (DKTK) partner site in Essen/Düsseldorf have discovered stem cells of the hematopoietic system in glioblastomas, the most aggressive form of brain tumor. These hematopoietic stem cells promote division of the cancer cells and at the same time suppress the immune response against the tumor. This surprising discovery might open up new possibilities for developing more effective immunotherapies against these malignant brain tumors.

The DKTK is a consortium centered around the German Cancer Research Center (DKFZ) in Heidelberg, which has long-term collaborative partnerships with specialist oncological centers at universities across Germany.

Glioblastomas are the most common dangerous brain tumor in adults; they grow diffusely into healthy brain tissue and are therefore almost impossible to completely remove by surgery. They defy the combination of surgery, radiotherapy, and chemotherapy and usually continue to grow unchecked. Even immunotherapies, which achieve good results in some cases in other types of cancer, have had no effect on these malignant brain tumors to date.

“Glioblastomas apparently create an environment that actively suppresses the immune response,” explained Björn Scheffler, DKTK Professor of Translational Oncology at the West German Tumor Center in Essen, partner site Essen/Düsseldorf. “They produce immunosuppressive messengers, and in the immediate environment of the tumors we find certain types of immune cells that specifically suppress the immune defense.”

Researchers were not previously aware of the variety of immune cells in the microenvironment of glioblastomas in any detail. Yet Scheffler and his colleagues realized that a precise knowledge of the cellular composition of glioblastomas was necessary in order to be able to overcome tumor-related immunosuppression using appropriate treatments.

In tissue samples of 217 glioblastomas, 86 WHO grade II and III astrocytomas, and 17 samples from healthy brain tissue, the DKTK researchers used computer-assisted transcription analyses to draw up profiles of the cellular composition. The tissue samples were taken directly from the resection margins – where remaining tumor cells and immune cells meet.

The team were able to distinguish between signals from 43 cell types, including 26 different types of immune cells. To their great surprise, the researchers discovered hematopoietic stem and precursor cells in all the malignant tumor samples, while this cell type was not found in healthy tissue samples. “Blood stem cells are actually found in bone marrow, from where they supply the body with all kinds of mature blood cells – obviously including all the different types of immune cells. Blood stem cells of the brain tumor itself have never been described before now,” remarked lead author Celia Dobersalske.

An even more surprising observation was that these blood stem cells seem to have fatal characteristics: They suppress the immune system and at the same time stimulate tumor growth. When the researchers cultured the tumor-associated blood stem cells in the same petri dish as glioblastoma cells, cancer cell division increased. At the same time, the cells produced large amounts of the PD-L1 molecule, known as an “immune brake”, on their surface.

Tumor organoids – tiny tumors grown in a petri dish from the brain tumor cells of individual patients – reacted to the blood stem cells too. In the presence of these cells, the cancer cells formed a network of cell processes that connects them. Only a few years ago, scientists from the DKFZ and Heidelberg University Hospital discovered that glioblastoma cells communicate using these connections and can thus protect themselves against treatment-related damage.

All these observations suggested that the blood stem cells found in glioblastomas have a negative impact on the course of disease. This was confirmed in a study of 159 glioblastoma patients for whom data were available on the clinical course of disease. In this group of patients, it was consistently observed that the more blood stem cells a tumor contained, the more immunosuppressive messengers were released and the more immunosuppressive markers the cancer cells formed – and the lower the overall survival of the patients was.

In order to investigate brain tumor blood stem cells in more detail, the authors teamed up with the Department of Neurosurgery at Essen University Hospital (Director: Ulrich Sure) to extract individual cells from fresh patient tissue. Using gene expression sequencing in 660 individual cells, the researchers created a profile and compared it with cells from healthy bone marrow and blood. Analysis of these data led to several specific new suggestions as to how this tumor-promoting cell population could be made harmless.

It was already known from research reports that the blood stem cells in bone marrow tend to mature into immunosuppressive cell types during differentiation in the course of cancer. It appears that they are programmed by the tumor to do so. Expert and last author Igor Cima suspects that a similar phenomenon might be responsible for the observations in the glioblastoma-associated blood stem cells: “We can now see an opportunity to intervene in order to modify the differentiation process of the glioma-associated blood stem cells, for example through particular cell messengers, and hence prevent the immune system from being blocked as a result of the tumor. Immunotherapies would then have a better chance of being effective against glioblastomas.”

Featured image: The image shows a collage of fluorescently labeled tumor organoids grown from patient cells in the Scheffler lab as a “mini brain tumor” for research. © Source: K. Stratmann und C. Dobersalske

Reference: I-Na Lu, Celia Dobersalske, Laurèl Rauschenbach, Sarah Teuber-Hanselmann, Anita Steinbach, Vivien Ullrich, Shruthi Prasad, Tobias Blau, Sied Kebir, Jens T. Siveke, Jürgen C. Becker, Ulrich Sure, Martin Glas, Björn Scheffler and Igor Cima: Tumor-associated hematopoietic stem and progenitor cells positively linked to glioblastoma progression Nature Communications 2021, DOI: 10.1038/s41467-021-23995-z

Provided by DKFZ

Study Uncovers Stem Cells Ability to Restore Immunity And Repair Gut Damage Caused by HIV (Medicine)

In a groundbreaking study, a team of UC Davis researchers has discovered a special type of stem cell that can reduce the amount of the virus causing AIDS, boosting the body’s antiviral immunity and repairing and restoring the gut’s lymphoid follicles damaged by the simian immunodeficiency virus (SIV), the equivalent of the human immunodeficiency virus (HIV) in non-human primates.

The study, published June 22 in JCI Insight, showed the mechanism through which mesenchymal stem/stromal cells (MSCs) enhance the body’s immune response to the virus. It also provides a roadmap for developing multi-pronged HIV eradication strategies.

“Impaired immune functions in HIV infection and incomplete immune recovery pose obstacles for eradicating HIV,” said Satya Dandekar, senior author of this paper. “Our objective was to develop strategies to boost immunity against the virus and empower the host immune system to eradicate the virus. We sought to repair, regenerate and restore the lymphoid follicles that are damaged by the viral infection.”

The lymphoid tissue in the gut is an early site for viral replication and the establishment of viral reservoirs. Dandekar’s group has previously shown that an HIV infection causes severe loss of gut mucosal T immune cells and disrupts the gut epithelial barrier lining, leading to a leaky gut.

“The lymphoid follicles are organized structures where the long-term immune attack is launched against pathogens by generating antibody response targeting the virus. These important regions are functionally impaired very early following HIV infection,” Dandekar said.

While antiretroviral drugs effectively suppress viral replication, they do not repair the damage caused by the virus to the immune system. On their own, these drugs cannot restore the functionality of the lymphoid follicles damaged by HIV infection.

Can stem cells counteract the gut damage caused by HIV?

The researchers administered bone marrow-derived MSC in a rhesus macaque model of AIDS that had impaired immunity and disrupted gut functions due to the viral infection.

“We are starting to recognize the great potential of these stem cells in the context of infectious diseases. We have yet to discover how these stem cells can impact chronic viral infections such as AIDS,” Dandekar said. She is a professor at and the chairperson of the Department of Medical Microbiology and Immunology at UC Davis and affiliated with the California National Primate Research Center.

The study found that the MSCs can modulate, alter and remodel the damaged mucosal site. There were immediate benefits, with a rapid rise in antibodies and T-immune cells targeting the virus. The stem cells were instrumental in the recovery and restoration of these lymphoid follicles.

MSCs also offer an opportunity for an innovative, multi-pronged HIV cure strategy by complementing current HIV treatments.

“Stem cells are good synergistic partner components with drugs. The antiretroviral drugs can stop the fire of the viral infection but cannot restore the forest of the lymphoid tissue compartment. The MSCs would rejuvenate the field and bring back immune vitality,” Dandekar said.

Even without the use of antiviral drugs, MSCs were able to increase the host’s antiviral response by repairing the lymphoid follicles, restoring the mucosal immunity and reviving what has been targeted by the virus very early on.

MSC treatments

MSC treatments require well defined cell quality controls and specific delivery mechanisms. The UC Davis Stem Cell Program, a center for excellence for stem cell research, is leading multiple clinical trials on MSC use in treating diseases such as spina bifida and Huntington’s disease. Findings from this study provide a scientific basis for investigating MSC in treating HIV and other infectious diseases in the clinical setting.

Co-authors on this study are Mariana G. Weber, Chara J. Walters-Laird, Clarissa Santos Rocha, Lauren A. Hirao, Abigail Mende, Juan Arredondo, Amir Kol, Sonny R. Elizaldi, Smita S. Iyer and Alice Tarantal at UC Davis, and Bipin Balan at Università di Palermo, Italy.

This work was supported by National Institutes of Health grants (R01AI 153025, R21 AI 116415, R21AI34368, and OD P51 OD011107) and from the National Council for Scientific and Technological Development (CNPq), Brazil.

Featured image: HIV disrupts the lymphoid immune battleground © UC Davis Health

Article: Weber et al. (2021) Gut germinal center regeneration and enhanced antiviral immunity by mesenchymal stem/stromal cells in SIV infection. JCI Insight. 6(12), Doi:10.1172/jci. insight.149033.

Provided by UC Davis Health

Human Mesenchymal Stem Cells Show Promise in Treating Chronic Lung Infections (Medicine)

A study released today in STEM CELLS Translational Medicine offers hope for those suffering from a chronic, difficult to treat condition called non-tuberculous mycobacteria (NTM) lung infection. The study describes how researchers at Case Western University developed a new model of NTM lung infection and then used it to show how effective human mesenchymal stem cells (hMSCs) are in treating this condition – and even which donor cells might be best for doing so.

“The potential to use human mesenchymal stem cells to treat difficult lung infections is promising,” said Anthony Atala, M.D., Editor-in-Chief of STEM CELLS Translational Medicine and Director of the Wake Forest Institute for Regenerative Medicine. “This study shows the ability of using optimal donors to obtain maximum treatment success.”

NTMs are naturally occurring, and everyone inhales them into their lungs as part of daily life. For most people, they are harmless. But in a small number of vulnerable individuals, such as older people or those with cystic fibrosis (CF) or COPD, NTM bacteria can settle in the lungs and cause infection. While not contagious, more than 100,000 people are living with NTM lung disease in the U.S. alone, and that rate appears to be increasing.

“NTM infections can be very difficult to resolve,” said Tracey L. Bonfield, Ph.D., the study’s corresponding author. “Treatment typically requires taking multiple antibiotics, often for years. Patients who suffer from chronic NTM infection not only deal with the consequences of the disease, but also the toxicity, as well as inefficiency and side effects of the antibiotics used to treat it.”

In the search for better therapies, some researchers are focusing on hMSCs, which are collected from adults and can be coaxed into becoming a variety of cells types. hMSCs have significant potential for treating infection and inflammation, Dr. Bonfield said. “They are dynamic storehouses of anti-microbial activity. They are unique in their capacity to respond to infection by secreting multiple bioactive factors, contributing to the host environment. That gives hMSCs a clinical advantage over traditional pharmaceuticals.”

Previous studies by the Bonfield team described the potential for hMSCs and their secreted products (“supernatants”) to treat other types of lung infections including Pseudomonas aeruginosa and Staphylococcus aureus, but these studies are the first to describe the ability of hMSCs to manage two of the most problematic groups of NTMs, Mycobacterium avium (M. avium) and Mycobacterium intracellulare (M. intracellulare). Like these current studies, hMSCs demonstrated significant anti-microbial, anti-inflammatory and anti-fibrotic potential, both in culture medium (in vitro) and in animals (in vivo). Further, they also documented that hMSC treatment improves the effectiveness of antibiotics, leading to a decrease in the dose necessary for eradicating bacteria.

At the same time, those studies pointed out that not all hMSC preparations have the same level of potency or sustainability. “This suggested to us that it is essential to identify the appropriate hMSC donor and subsequent preparation for disease specific applications. That was the goal of our current study,” said Dr. Bonfield.

Both M. avium and M. intracellulare are slow growing bacteria, so researchers have found it difficult to study what happens in sustained NTM infections because in small animals the bacteria clear up quickly, while larger animals are too expensive for defining dosing, timing and duration of a new treatment, Dr. Bonfield noted. So, her team first needed to develop new models of M. avium and M. intracellulare lung infections that would effectively allow them to study this issue.

“In the earlier studies we had developed an innovative protocol in which M. avium and M. intracellulare can be evaluated over the course of a week instead of the typical four to six weeks,” Dr. Bonfield explained. To sustain infection in vivo for chronic disease required an additional innovation “We did this by embedding NTMs into beads of a polysaccharide extracted from seaweed called agarose, and then injecting them into mice with CF. The beads degrade gradually, releasing the NTM into the mice and thus extending the time of infection and inflammatory response. This modeling system has been very efficient in generating acute and chronic scenarios of infection in all of our models.”

The researchers then went on to identify donor-specific hMSC potency against M. avium and M. intracellulare, once again in vitro and in vivo using CF mice. “Every donor hMSC preparation has a unique profile in terms of how the cells respond to pathogens, which likely translates into their successful potency and how the patient responds to hMSC treatment,” Dr. Bonfield said.

“Focusing on hMSC response to NTMs and efficiency of in vitro and in vivo anti-NTM activity provides direction for identifying the optimal hMSC signature for anti-NTM therapy. Data gained from our study begins to define this unique hMSC fingerprint.”

The full article, “Donor defined mesenchymal stem cell anti-microbial potency against non-tuberculous mycobacterium,” can be accessed at https://stemcellsjournals.onlinelibrary.wiley.com/doi/abs/10.1002/sctm.20-0521.

Featured image: MESENCHYMAL STEM CELLS (hMSCs) ANTI-NON-TUBERCULOUS MYCOBACTERIA ACTIVITY: hMSCs have impressive clinical and therapeutic benefits including antimicrobial and antibiotic enhancing potency. hMSC are antimicrobial against Mycobacterium avium and Mycobacteria intracellulare, which complicate a variety of pulmonary diseases. hMSC effects are mediated through altering host immunity and direct production of soluble mediators. Potency is both pathogen and donor hMSC specific. © Alphamed Press

Provided by AlphaMed Press

Scientists Use Nanotechnology to Detect Bone-healing Stem Cells (Nanotechnology)

Researchers at the University of Southampton have developed a new way of using nanomaterials to identify and enrich skeletal stem cells – a discovery which could eventually lead to new treatments for major bone fractures and the repair of lost or damaged bone.

Working together, a team of physicists, chemists and tissue engineering experts used specially designed gold nanoparticles to ‘seek out’ specific human bone stem cells – creating a fluorescent glow to reveal their presence among other types of cells and allow them to be isolated or ‘enriched’.

The researchers concluded their new technique is simpler and quicker than other methods and up to 50-500 times more effective at enriching stem cells.

The study, led by Professor of Musculoskeletal Science, Richard Oreffo and Professor Antonios Kanaras of the Quantum, Light and Matter Group in the School of Physics and Astronomy, is published in ACS Nano – an internationally recognised multidisciplinary journal.

In laboratory tests, the researchers used gold nanoparticles – tiny spherical particles made up of thousands of gold atoms – coated with oligonucleotides (strands of DNA), to optically detect the specific messenger RNA (mRNA) signatures of skeletal stem cells in bone marrow. When detection takes place, the nanoparticles release a fluorescent dye, making the stem cells distinguishable from other surrounding cells, under microscopic observation. The stem cells can then be separated using a sophisticated fluorescence cell sorting process.

Stem cells are cells that are not yet specialised and can develop to perform different functions. Identifying skeletal stems cells allows scientists to grow these cells in defined conditions to enable the growth and formation of bone and cartilage tissue – for example, to help mend broken bones.

Stem cells with release of fluorescent oligonucleotides in red. © University of Southampton

Among the challenges posed by our ageing population is the need for novel and cost-effective approaches to bone repair. With one in three women and one in five men at risk of osteoporotic fractures worldwide, the costs are significant, with bone fractures alone costing the European economy €17 billion and the US economy $20 billion annually.

Within the University of Southampton’s Bone and Joint Research Group, Professor Richard Oreffo and his team have been looking at bone stem cell based therapies for over 15 years to understand bone tissue development and to generate bone and cartilage. Over the same time-period, Professor Antonios Kanaras and his colleagues in the Quantum, Light and Matter Group have been designing novel nanomaterials and studying their applications in the fields of biomedical sciences and energy. This latest study effectively brings these disciplines together and is an exemplar of the impact collaborative, interdisciplinary working can bring.

Professor Oreffo said: “Skeletal stem cell based therapies offer some of the most exciting and promising areas for bone disease treatment and bone regenerative medicine for an aging population. The current studies have harnessed unique DNA sequences from targets we believe would enrich the skeletal stem cell and, using Fluorescence Activated Cell Sorting (FACS) we have been able to enrich bone stem cells from patients. Identification of unique markers is the holy grail in bone stem cell biology and, while we still have some way to go; these studies offer a step change in our ability to target and identify human bone stem cells and the exciting therapeutic potential therein.”

Professor Oreffo added: “Importantly, these studies show the advantages of interdisciplinary research to address a challenging problem with state of the art molecular/cell biology combined with nanomaterials’ chemistry platform technologies.”

Professor Kanaras said: “The appropriate design of materials is essential for their application in complex systems. Customizing the chemistry of nanoparticles we are able to program specific functions in their design.

“In this research project, we designed nanoparticles coated with short sequences of DNA, which are able to sense HSPA8 mRNA and Runx2 mRNA in skeletal stem cells and together with advanced FACS gating strategies, to enable the assortment of the relevant cells from human bone marrow.

“An important aspect of the nanomaterial design involves strategies to regulate the density of oligonucleotides on the surface of the nanoparticles, which help to avoid DNA enzymatic degradation in cells. Fluorescent reporters on the oligonucleotides enable us to observe the status of the nanoparticles at different stages of the experiment, ensuring the quality of the endocellular sensor.”

Both lead researchers also recognise that the accomplishments were possible due to the work of all the experienced research fellows and PhD students involved in this research as well as collaboration with Professor Tom Brown and Dr Afaf E-Sagheer of the University of Oxford, who synthesised a large variety of functional oligonucleotides.

The scientists are currently applying single cell RNA sequencing to the platform technology developed with partners in Oxford and the Institute for Life Sciences (IfLS) at Southampton to further refine and enrich bone stem cells and assess functionality. The team propose to then move to clinical application with preclinical bone formation studies to generate proof of concept studies.

The work has been possible through a BBSRC project grant to Professor Oreffo and Professor Kanaras. 

Featured image: Microscopic image of enriched skeletal stem cells using gold nanoparticles. © University of Southampton

Reference: Miguel Xavier, Maria-Eleni Kyriazi, Stuart Lanham, Konstantina Alexaki, Elloise Matthews, Afaf H. El-Sagheer, Tom Brown, Antonios G. Kanaras, and Richard O. C. Oreffo, “Enrichment of Skeletal Stem Cells from Human Bone Marrow Using Spherical Nucleic Acids”, ACS Nano 2021.

Provided by University of Southampton

Maletic-Savatic Lab Discovers a Novel Marker of Adult Human Neural Stem Cells (Neuroscience)

 The mammalian center for learning and memory, hippocampus, has a remarkable capacity to generate new neurons throughout life. Newborn neurons are produced by neural stem cells (NSCs) and they are crucial for forming neural circuits required for learning and memory, and mood control. During aging, the number of NSCs declines, leading to decreased neurogenesis and age-associated cognitive decline, anxiety, and depression. Thus, identifying the core molecular machinery responsible for NSC preservation is of fundamental importance if we are to use neurogenesis to halt or reverse hippocampal age-related pathology.  

While there are increasing number of tools available to study NSCs and neurogenesis in mouse models, one of the major hurdles in exploring this fundamental biological process in the human brain is the lack of specific NSCs markers amenable for advanced imaging and in vivo analysis. A team of researchers led by Dr. Mirjana Maletić-Savatić, associate professor at Baylor College of Medicine and investigator at the Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital, and Dr. Louis Manganas, associate professor at the Stony Brook University, decided to tackle this problem in a rather unusual way. They reasoned that if they could find proteins that are present on the surface of NSCs, then they could eventually make agents to “see” NSCs in the human brain.  

“The ultimate goal of our research is to maintain neurogenesis throughout life at the same level as it is in the young brains, to prevent the decline in our cognitive capabilities and reduce the tendency towards mood disorders such as depression, as we age. To do that, however, we first need to better understand this elusive, yet fundamental process in humans. However, we do not have the tools to study this process in live humans and all the knowledge we have gathered so far comes from analyses of the postmortem brains. And we cannot develop tools to detect this process in people because existing NSC markers are present within cells and unreachable for in vivo visualization,” Maletić-Savatić said. “So, in collaboration with our colleagues from New York and Spain, we undertook this study to find surface markers and then develop tools such as ligands for positron emission tomography (PET) to visualize them using advanced real-time in vivo brain imaging.” 

Typically, antibodies are made against known antigens but the team set out to generate antibodies for unknown target proteins, which made their mission rather challenging. They solved this problem by relying on an age-old method of generating antibodies by injecting mice with whole-cell or membrane preparations. This resulted in 1648 clones out of which 39 reacted with NSCs. Upon closer examination, one potential candidate most strongly labeled NSCs. Mass spectrometric analysis of the human hippocampal tissue identified the target protein as the Brain-Abundant Signal Protein 1 (BASP-1), previously shown to be present in the neurons of the mouse brain but not in NSCs. Interestingly, the specific antibody that recognizes BASP-1 in NSCs did not label neurons or any other cells apart from NSCs, indicating that it could be used to visualize these cells in the live mammalian brain.  

“Using our new antibody, we found that BASP-1 is restricted to NSCs in neurogenic niches in the mammalian brains, including humans, during development in utero and after birth. Thus, our work identified membrane-bound BASP-1 protein as a possible biomarker of NSCs that would allow us to examine the mechanisms of adult human neurogenesis as well as to explore its role in the process,” Maletić-Savatić concluded. 

With this newly discovered biomarker, scientists can better understand the relevance and intricate mechanisms of neurogenesis, which may lead to new future therapeutic approaches to treat and manage neurological and neuropsychiatric disorders associated with diminished neurogenesis. The study was published in the journal, Nature Scientific Reports.

Other authors involved in the study include Louis N. Manganas, Irene Durá, Sivan Osenberg, Fatih Semerci, Mehmet Tosun, Rachana Mishra, Luke Parkitny and Juan M. Encinas. They are affiliated with one or more of the following institutions: Baylor College of Medicine (BCM), Texas Children’s Hospital, Jan and Dan Duncan Neurological Research Institute, Achucarro Basque Center for Neuroscience, Stony Brook University Medical Center, and the Basque Foundation for Science. The study was funded by the grants from the National Institutes of Health, U.S. Army Medical Research, Cynthia and Antony Petrello Endowment, and Mark A. Wallace Endowment; the National Institute of Diabetes and Digestive and Kidney Diseases, MINECO, FPI MICINN predoctoral fellowship; the Proteomics Center at Stony Brook University, and the BCM IDDRC.

Featured image: Dr. Mirjana Maletic-Savatic © TCH

Reference: Manganas, L.N., Durá, I., Osenberg, S. et al. BASP1 labels neural stem cells in the neurogenic niches of mammalian brain. Sci Rep 11, 5546 (2021). https://doi.org/10.1038/s41598-021-85129-1

Provided by Texas Children’s Hospital

Induced Pluripotent Stem Cells Reveal Causes of Disease (Biology)

Induced pluripotent stem cells (iPSC) are suitable for discovering the genes that underly complex and also rare genetic diseases. Scientists from the German Cancer Research Center (DKFZ) and the European Molecular Biology Laboratory (EMBL), together with international partners, have studied genotype-phenotype relationships in iPSCs using data from approximately one thousand donors.

Tens of thousands of tiny genetic variations (SNPs, single nucleotide polymorphisms) have been identified in the human genome that are associated with specific diseases. Many of these genetic variants are not located in the protein-coding regions of genes, but affect regulatory sections. Therefore, scientists are trying to find out if and in which tissues these variants can be linked to changes in the activity of specific genes.

Typically, such analyses are performed in blood cells or tissue biopsies, depending on the type of disease. “Pluripotent stem cells, however, might be better suited for this purpose in many cases, as they are undifferentiated and therefore reflect the ancestral state of all cells,” says Oliver Stegle, division head at the German Cancer Research Center and group leader at EMBL. “Stem cells could be particularly relevant when searching for the cause of diseases that occur early in development.” Pluripotent stem cells can be generated in the culture dish from normal body cells obtained from a blood sample, for example. They are referred to as “induced pluripotent stem cells,” or iPSCs for short, since they are not naturally occurring stem cells.

Together with scientists from Stanford University and additional international cooperation partners, Oliver Stegle’s team has compiled sequence and transcriptome data on iPSCs from around 1000 donors. The researchers systematically examined these data to identify correlations between individual genetic variants and altered expression patterns in stem cells. The results have now been published in the journal Nature Genetics.

For more than 67 percent of all genes active in iPSCs, the researchers found differential expression patterns depending on genetic variants. Many of these associations are novel and have not been described in somatic cell types before. For over 4000 of these associations, the genetic variants responsible for the altered expression patterns could be linked to specific diseases. These included, for example, variants associated with coronary heart disease, lipid metabolism disorders or hereditary cancers.

Stegle and colleagues also investigated whether iPS are suitable for identifying the causative genes of rare genetic diseases. They used iPSC lines from 65 patients who suffered from various rare diseases, whose causal gene defects were already known through previous analyses. In the transcriptome data of these iPSC lines, the scientists searched for particularly conspicuous “outliers” in the expression pattern. These analyses reliably led to the trace of the genetic basis of the disease. “Such screenings were previously impossible because there were simply no sufficiently large reference collections of iPS transcriptomes,” explained Marc Jan Bonder, first author of the study.

“We were surprised to find such a large number of disease-associated genetic variants that are already visible in the expression pattern at the earliest time point of cell differentiation, represented by the iPSCs”. Until now, the relevance of iPSCs for such biomedical analyses has been significantly underestimated.

In a companion paper, published in the same issue of Nature Genetics, Stegle and colleagues from EMBL-EBI and the Wellcome Trust Sanger Institute used more than 200 iPSC lines to investigate how genetic variants affect differentiation into neuronal cells.

The scientists performed RNA single-cell sequencing at different time points of neuronal cell differentiation. This allowed them to analyze how genetic variants affect expression patterns in different cellular states, including different neuronal cell types. “The study demonstrates the power of combining single-cell sequencing with iPSC technologies to dissect the effect of genetic variants in cell types that would otherwise be inaccessible,” Stegle explains.

Reference: (1) Bonder, M.J. Smail, C., Gloudemans, M.J., Frésard, L., Jakubosky, D., D’Antonio, M., Li, X., Ferraro, N.M., Carcamo-Orive, I., Mirauta, B., Seaton, D.D., Cai, N., Kilpinen, H., Vakili, D., Horta, D., Wheeler, M.T., Zhao, C., Zastrow, D.B., Bonner, D.E., HipSci Consortium, iPSCORE Consortium, GENESiPS Consortium, PhLiPS Consortium, Undiagnosed Diseases Network, Knowles, J.W., Smith, E.N., Frazer, K.A., Montgomery, S.B., Stegle, O.: Identification of rare and common disease variants using population-scale transcriptomics of pluripotent cells.
Nature Genetics 2021, DOI: https://dx.doi.org/10.1038/s41588-021-00800-7 (2) Jerber, J., Seaton, D.D., Cuomo, A.S.E., Kumasaka, N., Haldane, J., Steer, J., Patel, M., Pearce, D., Andersson, M., Bonder, M.J., Mountjoy, E., Ghoussaini, M., Lancaster, M.A., HipSci Consortium, Marioni, J.C., Merkle, F.T., Gaffney, D.J., Stegle, O: Population-scale single-cell RNA-seq profiling across dopaminergic neuron differentiation
Nature Genetics 2021, DOI: https://dx.doi.org/10.1038/s41588-021-00801-6

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The Key to Proper Muscle Growth (Medicine)

hree oscillating proteins cause new muscle cells to emerge from muscle stem cells in a balanced manner. In a paper being published in the journal “Nature Communications”, a team led by MDC researcher Carmen Birchmeier explains in detail how this process works.

When a muscle grows, because its owner is still growing too or has started exercising regularly, some of the stem cells in this muscle develop into new muscle cells. The same thing happens when an injured muscle starts to heal. At the same time, however, the muscle stem cells must produce further stem cells – i.e., renew themselves – as their supply would otherwise be depleted very quickly. This requires that the cells involved in muscle growth communicate with each other.

Muscle growth is regulated by the Notch signaling pathway

We have now provided unequivocal evidence (…) that these rhythmic fluctuations in gene expression are actually crucial for transforming stem cells into muscle cells in a balanced and controlled manner.

— Professor Dr. Carmen Birchmeier, head of Developmental Biology / Signal Transduction Lab

Two years ago, a team of researchers led by Professor Carmen Birchmeier, head of the Developmental Biology/Signal Transduction Lab at the Berlin-based Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), showed that the development of stem cells into muscle cells is regulated with the help of two proteins, Hes1 and MyoD, which are produced in the progenitor cells in an oscillatory manner – i.e., there are periodic fluctuations in the number of cells produced.

Both proteins are involved in the Notch signaling pathway, a widespread mechanism by which cells respond to external stimuli and communicate with other cells. The signaling pathway is named after its receptor “Notch,” onto which the ligand “Delta,” a cell surface protein, latches.

A third protein, Delta-like1, plays a crucial role

“In our current study, we have provided unequivocal evidence that oscillation in muscle tissue is not just some strange phenomenon of the cells involved, but that these rhythmic fluctuations in gene expression are actually crucial for transforming stem cells into muscle cells in a balanced and controlled manner,” says Birchmeier.

Immunofluorescence analysis of a group of proliferating stem cells associated with a muscle fiber (grey). The stem cells produce Dll1 (red) and MyoD (green). Two of the cells produces MyoG (blue): They are differentiating to form a new muscle cell. Note that the overlay of blue, green and red appears as white. © Birchmeier Lab, MDC

Together with researchers from Japan and France, Birchmeier and four other scientists at the MDC also uncovered the crucial role of a third protein that, along with Hes1 and MyoD, forms a dynamic network within the cells. As the team reports in the journal Nature Communications, this protein is the Notch ligand Delta-like1, or Dll1 for short. “It is produced in activated muscle stem cells in a periodically fluctuating manner, with the oscillation period lasting two to three hours,” Birchmeier explains, adding: “Whenever a portion of the stem cells expresses more Dll1, the amount in the other cells is correspondingly lower. This rhythmic signaling determines whether a stem cell becomes a new stem cell or develops into a muscle cell.”

The Hes1 protein sets the pace in the stem cells  

Put simply, Hes1 acts as the oscillatory pacemaker, while MyoD increases Dll1 expression.

— Dr. Ines Lahmann, Lead author of the study

In their experiments with isolated stem cells, individual muscle fibers and mice, Birchmeier and her team further investigated how the Hes1 and MyoD proteins are involved in muscle growth. “Put simply, Hes1 acts as the oscillatory pacemaker, while MyoD increases Dll1 expression,” says Dr. Ines Lahmann, a scientist in Birchmeier’s lab and a lead author of the study along with Yao Zhang from the same team. “These findings were demonstrated not only in our experimental analyses, but also in the mathematical models created by Professor Jana Wolf and Dr. Katharina Baum at the MDC,” Birchmeier says.

Experiments with mutant mice provided the decisive proof

With the help of gene-modified mice, the researchers obtained the most important evidence that Dll1 oscillation plays a critical role in regulating the transformation of stem cells into muscle cells. “In these animals, a specific mutation in the Dll1 gene causes production of the protein to occur with a time delay of a few minutes,” Birchmeier explains. “This disrupts the oscillatory production of Dll1 in cell communities, but does not alter the overall amount of the ligand.”

The mutation has severe consequences on the stem cells, propelling them to prematurely differentiate into muscle cells and fibers.

— Yao Zhang, Lead author of the study

“Nevertheless, the mutation has severe consequences on the stem cells, propelling them to prematurely differentiate into muscle cells and fibers,” reports Zhang, who performed a large portion of the experiments. As a result, he says, the stem cells were depleted very quickly, which resulted, among other things, in an injured muscle in the mice’s hind legs regenerating poorly and remaining smaller than it had been before the injury. “Quite obviously, this minimal genetic change manages to disrupt the successful communication – in the form of oscillation – between stem cells,” Zhang says.

This knowledge could lead to better treatments for muscle diseases

“Only when Dll1 binds to the Notch receptor in an oscillatory manner and thus periodically initiates the signaling cascade in the stem cells is there a good equilibrium between self-renewal and differentiation in the cells,” Birchmeier concludes. The MDC researcher hopes that a better understanding of muscle regeneration and growth may one day help create more effective treatments for muscle injuries and diseases.

Featured image: Immunofluorescence analysis of a group of proliferating stem cells associated with a muscle fiber (grey). The stem cells produce Dll1 (red) and MyoD (green). Two of the cells produces MyoG (blue): They are differentiating to form a new muscle cell. Note that the overlay of blue, green and red appears as white. © Birchmeier Lab, MDC


Yao Zhang et al: “Oscillations of Delta-like1 regulate the balance between differentiation and maintenance of muscle stem cells“, in Nature Communications, DOI: 10.1038/s41467-021-21631-4

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