Breakthroughs in Stem Cell Research

THE SCIENTIFIC and medical communities are optimistic about recent breakthroughs in stem cell research that position them much closer to realizing the benefits of regenerative medicine. Regenerative medicine includes gene therapies, cell therapies and tissue-engineered products intended to augment, repair, replace or regenerate organs, tissues, cells, genes and metabolic processes in the body. It aims to alter the current practice of medicine by treating the root causes of disease and disorders.¹

During the last 40 years, there have been three major breakthroughs in stem cell research. In 1981, Sir Martin Evans, thenchancellor of Cardiff University in Wales, was the first to identify embryonic stem cells (ESCs) in mice. In 1998, James Thomson, a biologist at the University of Wisconsin, and John Gearhart, PhD, of Johns Hopkins University isolated human ESCs and grew them in a lab. And in 2006, Shinya Yamanaka, PhD, at Kyoto University in Japan revealed a way of making embryonic-like cells from adult stem cells, avoiding the need to destroy an embryo. Dr. Yamanaka’s team reprogrammed ordinary adult stem cells by inserting four key genes forming induced pluripotent stem cells (iPSCs).²

Since then, scientists have been studying how to use iPSCs for cell-based therapies in regenerative medicine, to screen new drugs and to study disease modeling. They hope this understanding will give them insight into the normal growth of a human body and identify the causes of birth defects so stem cells can be used as a renewable source of replacement cells, tissues and organs to treat myriad diseases and disorders.

The Promise of Stem Cell Research

The Alliance for Regenerative Medicine (ARM) is a U.S.-based international advocate for regenerative medicine that fosters investment research and development and the successful commercialization of safe, effective and transformational therapies for patients around the world. According to ARM’s Director of Science and Industry Affairs Michael Lehmicke, “Stem cells have extraordinary potential to durably treat a number of serious diseases and disorders, including neurodegenerative disorders, cardiovascular disease, diabetes, macular degeneration and other prevalent and orphan indications. As of the end of 2019, ARM is tracking 169 clinical trials worldwide utilizing stem cells, including 25 in Phase III. More recently, we’ve seen a number of therapeutic developers establish clinical and preclinical programs to investigate the therapeutic potential of stem cells to treat acute respiratory distress syndrome associated with COVID-19.”

Kevin McCormack, senior director of public communications at the California Institute for Regenerative Medicine (CIRM), says the potential results of research involving the transplant of stem cells, drug discovery and diagnostics are nothing short of revolutionary: “These treatments are reshaping the way we see disease and the way we treat disease. Instead of using conventional therapies that were good at trying to keep the condition under control, stem cell therapies have the potential to rewind the clock and restore function to diseased or damaged organs and tissues. Transplanting cells can help repair and replace tissues damaged by disease. One day, we hope they will be able to help organs regenerate so that patients won’t need to get a transplant; instead, they will be able to regrow a damaged organ.”

Current Stem Cell Research

CIRM. Although there are approved marketed regenerative medicine products in specific regions/countries for specific indications that are listed on ARM’s website, stem cell research is ongoing in the United States and around the world. For instance, CIRM, which funds clinical trials that test promising stem cellbased treatments for currently incurable diseases or disorders, has funded 63 clinical trials, and another 25 projects in clinical trials have received crucial early support from the institute. In addition to working on stem cell research for blindness, blood cancers, blood disorders, diabetes and sickle cell disease, CIRM is studying how to use stem cells to treat neurodegenerative diseases such as Parkinson’s disease (including one in a clinical trial) and amyotrophic lateral sclerosis or Lou Gehrig’s disease (two of which are in clinical trials).

To deliver stem cell treatments to patients, CIRM developed the Alpha Stem Cell Clinics Network (ASCCN), an infrastructure comprised of six world-class medical facilities that have the expertise to deliver proven stem cell treatments and U.S. Food and Drug Association (FDA)-sanctioned clinical trial therapies to patients. To date, ASCCN has supported more than 130 clinical trials, targeting more than 40 different diseases and enrolling more than 750 patients.

CIRM also created the iPSC Repository, the world’s largest induced pluripotent stem cell bank established to harness the power of iPSCs as tools for disease modeling and drug discovery. The iPSC Repository houses a collection of stem cells from thousands of individuals, some of which are healthy but others that have heart, lung, liver or other diseases or disorders.³

In 2017, FDA created the Regenerative Medicine Advanced Therapy (RMAT) designation to fast-track therapeutic tissueengineered products, cell therapies, human cell and tissue products or any combination product that may save people from serious or life-threatening conditions or diseases that would otherwise be incurable. Of the 25 RMAT programs to date, six are funded by CIRM.

International Society for Stem Cell Research (ISSCR). An independent, nonprofit organization that provides a global forum for stem cell research and regenerative medicine, ISSCR provides information about how stem cells are being used to understand several diseases and conditions. Here’s what ISSCR has found:

• Diabetes. Insulin-producing cells derived from ESCs and iPSCs can reverse diabetes in experimental animals. Therefore, the research community is encouraged that cells derived from stem cells may succeed as beta cell replacement therapy and thus essentially cure type 1 diabetes.⁴
• Heart disease. Research is ongoing to test cellular therapies to treat heart attacks by combining different types of stem cells, repeating transplantations or improving stem cell patches. Clinical trials using these improved methods are targeted to begin in 2020.⁵
• Macular degeneration. Stem cell research is helping scientists understand how the different cell types in the retina function together, which has led to exploring ways to replace both rods and cones and the supporting retinal pigment epithelium (RPE) cells. Researchers are making great progress to replace the RPE layer, which they believe will halt or even reverse the vision loss associated with age-related macular degeneration. Some researchers are using iPSCs to grow rods and cones or RPE cells. Other researchers are using ESCs, while others are exploring RPE-specific stem cells that can be grown from the adult RPE (for example, from eyes donated to eye banks). A main goal is to determine the optimal maturation for these cells.

Researchers are also exploring different methods to deliver stem cells to the eye, including creating patches of RPE cells in the lab. Another method showing promise is a suspension of cells, which is injected into the eye under the retina. The cells, derived from iPSCs, RPEs or ESCs, are grown and differentiated in the lab, then placed in a harmless fluid to be injected. For both approaches, a critical question is whether these cells will integrate well with the patient’s own RPE stem cells and perform their job of supporting the rods and cones over the long term.⁶

• Multiple sclerosis (MS). The use of glial progenitor cells, which give rise to new myelin-producing oligodendrocytes, is under development as a potential treatment for MS. The goal is to stabilize disease by preventing further neuronal loss and restoring function by remyelinating the demyelinated neurons. The potential use of stem cell-derived glial cells as cellular therapies for treating progressive MS is under review by FDA. Pending acceptable preclinical safety data and FDA approval, clinical trials are scheduled to begin soon.⁷
• Osteoarthritis (OA). Due to a lack of clear support from high-quality studies, as well as a lack of consensus in the scientific and medical communities concerning many aspects of using cell therapies to treat OA (such as when stem cells should be used, the ideal source of stem cells and how they should be prepared, defined or delivered), the effects and effectiveness of cell therapies for treating OA remain unproven, and the scientific community does not currently recommend them.⁸
• Parkinson’s disease. The first in-human Parkinson’s disease clinical trials using iPSC-derived dopamine-producing cells began in Japan in August 2018, and trials in the U.S. using ESC are underway. In Europe, similar human trials are likely to begin for the first time in 2021. Trials in Australia using a non-ESC source began in 2016, but issues relating to aspects of the trial have been raised, including the origin of the cells, the type of cells transplanted and the availability and transparency of preclinical data.⁹

Harvard Stem Cell Institute (HSCI). Through collaborative research, HSCI seeks to stimulate healing in patients by harnessing the potential of stem cells; create targeted treatments by combining new gene- and cell-based therapies with traditional medicines; and accelerate drug discovery by developing novel stem cell-based tools. HSCI’s research focuses on the following disease areas: blood, cancer, cardiovascular, diabetes, kidney, musculoskeletal, nervous system (including ALS, Alzheimer’s disease, eye diseases, hearing loss, MS and Parkinson’s disease) and skin. HSCI also tackles research areas that span across individual diseases and organ systems, such as aging and fibrosis.

Breakthroughs in the HSCI’s research include:

• Demonstrating gene-editing machinery can be delivered straight to stem cells where they live rather than in a petri dish. The findings have major implications for biotechnology research and the development of therapeutics for genetic diseases.¹⁰
• Discovering how to make beta cells, the cells in the pancreas that measure glucose levels and squirt out insulin as needed.¹¹
• Integrating microfluidics and human insulin-producing beta cells in an islet-on-a-chip. The new device makes it easier for scientists to screen insulin-producing cells before transplanting them into a patient, test insulin-stimulating compounds and study the fundamental biology of diabetes. This automated miniature device gives results in real time, which can speed up clinical decision-making. And, it makes it easier to screen drugs that stimulate insulin secretion, test stem-cell-derived beta cells and study the fundamental biology of islets.¹²
• Identifying a stem cell defect as a possible cause of the chronic skin disease psoriasis.13
• Discovering that fatty acids influence skeletal stem cell development, which led to the discovery that stem cells can repair bone fractures. This study shows for the first time that specific nutrients can inform stem cells of the type of cell they should become, which is an important step forward in stem cell research.¹⁴

The Stanley Center for Psychiatric Research. The Stanley Center at the Broad Institute of MIT and Harvard is focused on better understanding neuropsychiatric disorders using stem cells and related models as one of many research tools into these disorders rather than using stem cells as treatments. Seeking to reduce serious mental illness, the center’s major focus is to clarify the molecular causes of schizophrenia, bipolar disorder and other severe mental illnesses, namely autism and attention deficit hyperactivity disorder, and to translate that knowledge into new therapies and biomarkers for patients.

To study these disorders, the Stanley Center is using human pluripotent stem cells acquired and reprogrammed through a large number of international collaborations, the most notable one the CIRM’s iPSC Repository. The Broad Institute has embarked on whole genome sequencing of hundreds of stem cell lines from the iPSC Repository to identify genes associated with neurological disorders, including autism spectrum disorder, and to use this information as a starting point to find cures.

The Stem Cell groups at the Stanley Center are developing stem cell-derived neuronal models and using genome engineering in iPSCs to investigate in-vitro phenotypes associated with genetic variants underlying psychiatric disease. Specifically, these groups are focused on the following projects: Human EnCELLopedia, stem cell genome engineering, human brain organoid models, neuronal spheroids for screening and therapeutic target studies, the brain interaction network, a human stem cell genome project, and massively mosaic experimental systems.

A unique feature of the stem cell collection efforts at the Stanley Center is its focus on developing a cellular and genetic resource of iPSC lines from patients with a spectrum of psychiatric conditions, as well as from ancestrally matched controls. This is critical for fueling downstream studies that aim to link disease-associated human genetic variation to defined cellular phenotypes.¹⁵

Clustered regularly interspaced short palindromic repeats (CRISPR). The combination of stem cell and gene therapy has the potential to become a game-changer in the field of regenerative medicine. A number of researchers are using CRISPR-Cas9, one of several genome editing techniques that lets scientists rewrite DNA sequences in any cell that could potentially cure genetic disorders and diseases. Genome editing is a technique in which DNA is inserted, replaced or removed at particular locations in the human genome to correct mutations that cause disorders and diseases.¹⁶

According to Kevin Doxzen, PhD, science communication specialist at the Innovative Genomics Institute (IGI) at the University of California (UC) Berkeley, CRISPR “represents a fascinating bacterial immune system that helps microbes defend themselves against viral attack. There are many different types of CRISPR immune systems, and through the process of studying the arms race between bacteria and viruses, scientists realized that some of the CRISPR proteins, known as Cas (CRISPRassociated) proteins, could be used as programmable molecular scissors. CRISPR-Cas9, the most popular Cas protein, uses small molecules of RNA that search and bind with matching sequences of DNA. This simple act allows Cas proteins to find a specific sequence of DNA among the six billion letters of the human genome. Once a matching DNA sequence is located, the DNA double helix is unwound, and Cas9 cuts both strands of DNA, allowing researchers to alter the DNA in a variety of ways. Many of the foundational CRISPR advancements were done on UC Berkeley’s campus.”

In just a few years, scientists at UC Berkeley and across the world have integrated CRISPR technology into their research. Many of these researchers are using genome editing for basic researcher questions such as understanding the molecular mechanisms behind wing pattern development in butterflies or brain function in squid. In addition to fundamental research questions, researchers at UC Berkeley are interested in addressing real-world issues using CRISPR technology. IGI, a research partnership between UC Berkeley and UC San Francisco, is leading this front. “Research teams at the IGI are working to develop CRISPR cures for sickle cell disease, autoimmune diseases and other genetic ailments. In addition to biomedical applications, the IGI is advancing the deployment of CRISPR technology agriculture, including to engineer drought-tolerance, disease-resistance and higher nutrition in a range of crops,” says Dr. Doxzen.

Dr. Doxzen also says CRISPR is already revolutionizing drug discovery and diagnostics: “In the midst of the COVID-19 pandemic, researchers are using genome editing to study the effect of viral infection on human cells and to design new drug treatments. Scientists are also using CRISPR-Cas proteins as a way to detect the presence of COVID-19 in patient samples.”

In the next few years, Dr. Doxzen says preliminary results will be seen of a wide range of CRISPR clinical trials aimed at curing genetic diseases, including sickle cell disease, genetic forms of blindness, muscular dystrophy and many more. “At the IGI, we are working to ensure that CRISPR therapies are affordable and accessible, especially for those who could most benefit from these innovative cures,” he explains. “As well, in the coming years, society will most likely have the option of buying CRISPR-edited food in their local supermarkets.”

CRISPR Therapeutics is a leading gene-editing company focused on developing transformative gene-based medicines for serious diseases using its proprietary CRISPR/Cas9 platform. The company is pursuing gene-editing approaches to allow allogeneic use of stem cell-derived therapies by enabling immune evasion, improving existing cell function and directing cell fate using CRISPR/Cas9. Its first major effort in this area, together with partner ViaCyte, is with diabetes.¹⁷

Remaining Challenges

According to ISSCR’s report “Stem Cell Facts,” there are several major challenges to address before stem cells can be used as cell therapies to treat a wider range of diseases. “First, we need to identify an abundant source of stem cells. Identifying, isolating and growing the right kind of stem cell, particularly in the case of rare adult stem cells, are painstaking and difficult processes. Pluripotent stem cells such as ESCs can be grown indefinitely in the lab and have the advantage of having the potential to become any cell in the body, but these processes are again very complex and must be tightly controlled. iPS cells, while promising, are also limited by these concerns. In both cases, considerable work remains to be done to ensure that these cells can be isolated and used safely and routinely.

“Second, as with organ transplants, it is very important to have a close match between the donor tissue and the recipient; the more closely the tissue matches the recipient, the lower the risk of rejection. Being able to avoid the lifelong use of immunosuppressants would also be preferable. The discovery of iPS cells has opened the door to developing patient-specific pluripotent stem cell lines that can later be developed into a needed cell type without the problems of rejection and immunosuppression that occur from transplants from unrelated donors.

“Third, a system for delivering the cells to the right part of the body must be developed. Once in the right location, the new cells must then be encouraged to integrate and function together with the body’s other cells.”¹⁸

Future of Stem Cell Research

According to CIRM’s McCormack, the future of stem cell research is very bright: “The last decade has been one of developing a deeper understanding of the science behind stem cells — how to harness their ability to renew and replicate themselves, how to be more effective in turning them into the kinds of cells we want them to be and creating the kind of changes we need. We believe the next decade will see that basic understanding of how the cells grow and help us become ever more effective at using these cells as therapies. Combined with the increased sophistication of our ability to use gene editing, we feel that this ‘one-two punch’ will greatly increase our ability to help patients who are suffering from previously incurable conditions.”

ARM’s Lehmicke agrees: “We expect that stem cell research will continue to grow over the next few years. Sector stakeholders are collaborating to establish best practices that will help to streamline the development and manufacture of these therapies. Additionally, we expect that iPSCs, which are just beginning to enter the clinic, will play a growing role in this area. In particular, we’re seeing a growing interest in utilizing iPSCs to create allogeneic or ‘off-the-shelf’ cell-based immunotherapies to treat cancer. This method may help to alleviate issues of immunogenicity and allow for easier scale up compared to highly personalized autologous therapies, which utilize the patient’s own cells and must be manufactured on a patient-by-patient basis.”

Deepak Srivastava, president of ISSCR and Gladstone Institutes, says, “The stem cell field continues to advance rapidly in both mechanistic understanding of disease and the translation of discovery into new therapies for so many devastating yet unsolved human diseases. Basic science discoveries in this area have matured to gain significant commercial investment in the last year for diabetes, Parkinson’s disease, heart failure, muscular dystrophies and cancer, to name a few. Rigorous clinical and preclinical trials are advancing based on transplanting stem cells, reprogramming resident cells, discovering new drugs using stem cells, and delivering missing genes or gene-editing machinery through novel gene therapy vectors.”¹⁹