In medical science, few advancements have held as much more promise as stem cell therapy. Researchers aim to restore and repair damaged tissues and organs by using the body’s natural regenerative capacities and combining them with technological tools. Stem cells are immature cells that can differentiate into specific cells such as blood cells to replace damaged ones and ensure proper body function. This occurs naturally in humans, for example, olfactory stem cells in the olfactory epithelium are induced to differentiate into olfactory sensory neurones, which are responsible for the processing of smell. These cells are integrated into the system and have a turnover rate of 40 days (Shipley et al., 2004).
There are different classifications of stem cells depending on their degree of potency. Early embryos contain totipotent stem cells, which have the remarkable potential to develop into any type of cell. On the other hand, pluripotent stem cells are present in the blastocyst’s inner cell mass and can differentiate into any type of cell in the human body (apart from placental cells). Multipotent stem cells have a more limited regeneration capacity, and their differentiation range is dependent on their tissue of origin. Lastly, unipotent stem cells only give rise to one specific cell type but have the power to renew which distinguishes them from non-stem cells. Induced pluripotent stem cells (iPSCs) also exhibit pluripotency but they are artificially generated from adult cells, which bypasses ethical concerns associated with embryonic stem cells.
Researchers are working on ways to enhance these cells’ regenerative properties in response to injury and ageing, in which cases the number of available stem cells decreases, implying that the natural process of regeneration is insufficient. Nevertheless, great advancements have been made in this field, such as the use of haematopoietic stem cell transplantation to treat blood disorders and the development in the understanding of using neural stem cells to treat neurodegenerative diseases.
In Parkinson’s disease (PD), there have been significant advancements in therapy by using dopaminergic neurones derived from stem cells to restore motor functions in animal models. It has been suggested as an alternative to deep brain stimulation, this refers to the current popular therapy option for PD which involves making small holes in the skull and implanting electrodes into the brain that activate an area called the subthalamic nucleus or globus pallidus internus in the basal ganglia circuitry, this treatment stops most symptoms like involuntary tremor. There are still a lot of trials, experiments and problems to explore until we see a common usage of stem cell treatment in PD but so far there has been promising evidence for example patients have been restored to pre-diagnosis levels of motor control in the absence of dopaminergic drugs, with the effects maintained for over a decade (Kefalopoulou et al., 2014).
Another neurodegenerative disease is multiple sclerosis, it is an autoimmune central nervous system condition that affects the brain and nerves characterised by damage to the myelin sheath with no current cure. In recent years, there have been many clinical trials investigating the use of stem cells, one of the latest publications describes a Phase I trial using allogenic stem cell-based therapy in people with progressive multiple sclerosis this year which marks an important milestone in the search for a suitable therapy (Fossati, Peruzzobtti-Jametti and Pluchino, 2023).
Even the field of cardiovascular disease, the leading cause of morbidity and mortality worldwide, has been a focal point in stem cell research. There have been trials that utilise intravenous mesenchymal stem cells to improve function after heart failure, Chung et al., 2017 produced a review that describes 11 clinical trials with a total of 647 patients and claimed these stem cells significantly improved heart function and reduced incidence of major adverse cardiovascular events. It has also been shown to stimulate the growth of new blood vessels through the release of angiogenic factors (Hou et al., 2016).
In the field of cancer, stem cells have also been a focus of treatment research. An example is haematopoietic stem cell transplantation, also known as bone marrow transplantation. These have been successfully used to treat blood disorders like leukaemia and lymphomas. These stem cells are obtained from a compatible donor or the patient’s bone marrow and then infused into the patient’s bloodstream. Once engrafted, these stem cells repopulate the bone marrow, replacing the damaged or cancerous cells with healthy ones (Khaddour, Hana and Mewawalla, 2023).
Diabetes is a global epidemic with increasing incidences and great burdens on healthcare systems. Type 1 is characterised by an autoimmune dysfunction that attacks insulin-producing beta cells meaning that the body cannot produce insulin and currently relies on life-long injections of insulin. In type 2, the pancreas makes less insulin and the body becomes resistant to it. Stem cell therapy offers a pioneering approach to restoring pancreatic function. Results from recent clinical trials concerning type-1 diabetic patients showed that the transplantation of stem cells has improved blood sugar control and combining exercise with the treatment has improved glycemic and immunologic indices (Izadi et al., 2022).
It is also important to consider the ethics of this technology. Embryonic stem cells are obtained from early-stage embryos and thus pose an important ethical debate. An alternative widely used is to induce pluripotent stem cells as those are derived from adult cells. Scientists are also developing standardised protocols to ensure the safety and efficacy of the research, which should be tightly adhered to. Furthermore, despite the achievements and promises shown so far, there are still many challenges. These include the need for standardised protocols for stem cell isolation, expansion, and transplantation, as well as the development of personalised approaches to optimise patient outcomes.
With the potential to transform healthcare by presenting cutting-edge therapy options for diseases that are now incurable, stem cells are at the forefront of regenerative medicine. Stem cell therapies are becoming more conceivable as a result of continued research, technological advancements, and adherence to ethical standards. The future of regenerative medicine appears more promising than ever as we realise the full potential of stem cells, giving hope to many patients worldwide.
References
- Chung, W.S., Lee, H.J., Cho, J.H., et al. (2017). Mesenchymal stem cells for the treatment of cardiovascular diseases: A systematic review. Stem Cell Research & Therapy, 8(1), 48.
- Hou, L., Kim, J. J., Woo, Y. J., & Huang, N. F. (2016). Stem cell-based therapies to promote angiogenesis in ischemic cardiovascular disease. American Journal of Physiology-Heart and Circulatory Physiology. https://doi.org/10.1152/ajpheart.00726.2015
- Izadi, M., Sadr Hashemi Nejad, A., Moazenchi, M. et al. Mesenchymal stem cell transplantation in newly diagnosed type-1 diabetes patients: a phase I/II randomized placebo-controlled clinical trial. Stem Cell Res Ther 13, 264 (2022).
- Kefalopoulou Z, Politis M, Piccini P, Mencacci N, Bhatia K, Jahanshahi M, Widner H, Rehncrona S, Brundin P, Björklund A, Lindvall O, Limousin P, Quinn N, Foltynie T. Long-term clinical outcome of fetal cell transplantation for Parkinson disease: two case reports. JAMA Neurol. 2014 Jan;71(1):83-7. doi: 10.1001/jamaneurol.2013.4749. PMID: 24217017; PMCID: PMC4235249.
- Khaddour K, Hana CK, Mewawalla P. Hematopoietic Stem Cell Transplantation.
- Fossati, V., Peruzzotti-Jametti, L. & Pluchino, S. A neural stem-cell treatment for progressive multiple sclerosis. Nat Med 29, 27–28 (2023).
- Michael T. Shipley, Matthew Ennis, Adam C. Puche, CHAPTER 29 – Olfactory System, Editor(s): George Paxinos, The Rat Nervous System (Third Edition), Academic Press, 2004, Pages 923-964, ISBN 9780125476386, https://doi.org/10.1016/B978-012547638-6/50030-4