4.2 MSCs
Until now, the only legal clinical stem-cell therapy was hematopoietic
stem-cell therapy for childhood leukemia. Other therapies remain
controversial because they are often related to abortion politics and
human cloning. However, the research field of stem-cell therapy is
constantly expanding, and scientists now have applied stem cells in
neurodegeneration, brain and spinal cord injury, frailty syndrome,
pancreatic beta cells, orthopedics, and other uses(Gazdic et al., 2018;
Golpanian et al., 2017; R. Li et al., 2018; Lyon, 2018; Memon &
Abdelalim, 2020). The significant difference between EPCs and MSCs is
that a lower immunogenicity is associated with MSCs. However, if low
immunogenicity leads to lengthy transplantation time and excessive
allogeneic cells in the circulation of patients, this may lead to
graft-versus-host disease (GVHD), which is the most severe side effect
of stem cell therapy(Malard & Mohty, 2014).
Ethical issues continue to cause problems with allografts because
embryonic stem cells are derived from human embryos, but this process
will kill the embryo. A key issue is the voluntary actions of donors,
and therefore, the choice of donation must be later than the choice of
abortion, so as to avoid involuntary activities caused by monetary
temptation or other factors. In addition to ethical issues, there are
also many criticisms of the experimental procedures. Some critics report
that only five basic trials seem to be used in 48 reports, and many
trials contradict each other. Therefore, research into clinical stem
cell therapy requires further development and stricter standards to
limit disordered behavior and prevent damage to the reputation of
scientists and the field of stem cell therapy(Heo, Choi, Kim, & Kim,
2016). He identity of patients after allogeneic stem cell
transplantation is another inevitable problem. Because allogeneic stem
cells can differentiate into allogeneic mature cells, the identity of
patients still needs to be further discussed and confirmed. It is
advantageous that the new technology of inducing pluripotent stem cells
avoids this ethical tissue, and another benefit is that it provides even
more convenient access as compared to autologous stem cells(Y. Y. Shi,
R. P. Nacamuli, A. Salim, & M. T. Longaker, 2005).