A Risky Resource?
Stem cells, the foundation of every organ and tissue in human beings, have evolved as a novel therapy since the first bone marrow transplantation of 1957. Stem cells are defined by two attributes:
They can self-renew, i.e., make copies of themselves
They can differentiate, i.e., develop into more specialized cells
Some of the common types of stem cells are: 1) Embryonic stem cells, which are called pluripotent, as they can generate every cell type in a fully formed body except those of the placenta and the umbilical cord. 2) Tissue-specific stem cells are those that can generate cells for specific tissues or organs, e.g., hematopoietic cells 3) Mesenchymal stem cells isolated from stroma – the connective tissue that surrounds other tissues and organs 4) Induced pluripotent stem cells engineered in the lab by converting tissue-specific cells into cells that behave like embryonic stem cells.
Autologous stem cell transplantation is a procedure in which blood-forming stem cells are removed, stored, and later given back to the same person. Allogeneic stem cell transplantation is a procedure in which a person receives blood-forming stem cells from a genetically similar, but not identical, donor.
Stem cell therapy has the potential to repair, restore, replace and regenerate cells, leading to a wide range of potential applications – bone marrow transplant, Alzheimer’s, Parkinson’s, spinal injury, muscular dystrophy, amyotrophic lateral sclerosis, stroke, myocardial infarction, cancer, macular degeneration retinitis pigmentosa, diabetes mellitus, osteoarthritis, rheumatoid arthritis, chronic wound healing, Crohn’s disease etc.. Although 10 stem cell treatments have been approved by international regulatory authorities, only bone marrow transplantation is widely used.
Most stem cell research is still experimental with limited clinical success because of uncertainty about its benefits and risks. Small, uncontrolled, and a few well-controlled clinical trials have not demonstrated effectiveness of stem cell therapy in well-researched indications such as heart failure and graft-versus-host disease. Recently, PreSERVE-AMI, the largest US clinical trial of bone-marrow cells for heart-attack patients, failed to show any benefits.
Safety of stem cell therapy is a major concern, as there are chances of serious adverse events, e.g. infection, immune reaction and tumours. Among the serious adverse events associated with stem cell treatment are – paraplegia caused by development of a glioproliferative lesion, tumours and renal failure leading to nephrectomy and worsening of vision and blindness in macular degeneration. Adverse effects may be more common than discussed in literature, as such events are not reported when stem cell therapy is tried outside a clinical trial, e.g. on individual patients in a clinic. In view of such safety concerns, US Food and Drug Administration issued a warning cautioning patients about the dangers of unapproved and unproven therapies offered by unscrupulous clinicians.
Indian guidance for stem cell therapies mandates that organizations – hospitals,
clinics, companies, research institutes,
university departments, and cell banking centres – involved in the collection, isolation storage, manufacturing, quality control, preclinical studies and clinical trials of stem cell therapy require approval from regulatory authorities International regulators require robust evidence of safety and efficacy to ensure that this emerging field can fulfill its promise to patients.