With everyone joining the race to develop a Cell Therapy that has great therapeutic potential, the question arises as to which stem cell type will be the most successful in this endeavor. With their capacity to self-renew and proliferate indefinitely as well as differentiate into a multitude of cell lineages, stem cells are an attractive target to exploit as a therapeutic application. However, scientists are still trying to elucidate the fundamental properties of stem cells and whether it translates to a viable treatment option for cancer, degenerative diseases, and repair of damaged tissue.
Stem cell types such as human embryonic stem cells (hESCs), human induced pluripotent stem cells (hiPSCs), hematopoietic stem cells (HSCs), and mesenchymal stem cells (MSCs) are considered the most clinically relevant and are believed to hold the most potential. Yet, there are many issues with the stem cells utilized today that present not only technical and ethical hurdles, but also challenges associated with federal restrictions.
For example, the use of hESCs has always been controversial and it is questionable whether hESCs will have a future within the stem cell and regenerative medicine field with those ethical hurdles looming over them that limit their use. In turn, hiPSCs that are reprogrammed adult cells manipulated to behave like embryonic stem cells bypass the ethical issues and limitations associated with hESCs. However, hiPSC are not without their faults as the next breakthrough technology. With scientists seeking to understand the implications of reprogramming adult cells into an embryonic stem cell like-state, many have begun to question the utility of hiPSCs. It is believed that the different methodologies utilized to generate iPSCs have in turn created new problems, such as epigenetic changes, premature senescence, variation in differentiation capabilities, and immunogenicity, and whether these changes can fuel neoplastic transformation. These are just a few issues which illustrate that we still have much to learn regarding the underlying molecular mechanisms of cellular reprogramming and if the safety of hiPSCs can be guaranteed to have a future as a clinical application.
Some would argue that adult stem cells will be the forerunner as the next Cell Therapy. Despite their limitations to differentiate only into the cell types from which they were derived (i.e. specific tissues), adult stem cells are more readily available, and considered more suitable for clinical purposes in which they can be derived from a patient’s own body and re-administered as such. It is believed that adult stem cells such as HSCs and MSCs require minimal manipulation (depending on the application) and supposedly offer more control in terms of ex vivo expansion and differentiation although the methodology is far from perfect. An important issue with the use of adult stem cells as a therapeutic application is that often these cells are manipulated (e.g. gene-modified) beyond ex vivo expansion and as such, have to meet regulatory compliance.
In short, the best stem cell type will have to provide the ability to translate from the lab to the clinic, practicality in clinical manufacturing, and most importantly, safety and efficacy as a treatment modality.