الفهرس 
Review of Literature I) Diabetes mellitus (DM)Only 14 pages are availabe for public view
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Abstract
The field of regenerative medicine is rapidly evolving, paving
the way for novel therapeutic interventions through cellular
therapies which are reshaping the biomedical field. As for DM, cell
replacement strategies via islet transplantation offer potential
therapeutic options for diabetic patients. However, the discrepancy
between the limited number of donor islets and the high number of
patients who could benefit from such a treatment reflects the
severe need for renewable sources of high-quality β-cells.
Interestingly, MSCs have made their mark in the evolving field of
regenerative medicine, and have been suggested as a potential
weapon to develop therapies for DM. Furthermore, genetic
manipulation of key transcription factors can serve to promote
trans-differentiation and increase plasticity of MSCs. REST has
been reported as a master negative regulator of neurogenesis.
Furthermore, it has been shown to be associated with the core selfrenewal
genes in ESCs, and also has been reported to play
important roles in β-cells.
Accordingly, in the current study, we sought to further
investigate WJ-MSCs being a readily accessible potential source
for cell therapy of DM together with the genetic manipulation of
the transcription factor REST. In an attempt to gain more insight
into its role to generate functioning IPCs from WJ-MSCs, and also
to study the potential of its modulation as a suggested new
modality to improve the therapeutic outcome of cell therapy for
DM.
To fulfil the aims of the current study, we isolated WJ-MSCs
from human UCs, and further characterized them according to the
defined criteria by ISCT. Afterwards, we induced them to
differentiate to IPCs using various protocols. Meanwhile, we
assessed the levels of both stem cells and β-cells markers side by
Summary and Conclusions
142
side in all the studied differentiation protocols. Finally, we carried
out knock down of REST using specific targeting siRNAs, and
studied the effect of such genetic manipulation on WJ-MSCs under
both control and differentiation conditions. The findings of the
current study are summarized as follows:
The isolation of WJ-MSCs was relatively easy, and provided a
homogenous population, together with large expansion potential,
which come in accordance with all the previous reports
highlighting the importance of WJ-MSCs for regenerative
medicine.
During the induction of differentiation of WJ-MSCs to IPCs,
surprisingly, the expression levels of both stemness and β-cells
markers were induced in the derived IPCs from various
protocols. The sustained expression of these pluripotency
markers might be associated with the incomplete differentiation
and inability of the derived IPCs to attain mature β-cell state.
Nevertheless, Oct-4 and Sox-2 in the current study could play
some unknown important role during the differentiation process.
The current findings imply that the strategy of focusing on the
induction of β-cell markers alone might not be sufficient to
attain complete differentiation of MSCs to mature functioning
IPCs. The pluripotency markers’ levels during the differentiation
process should be considered carefully, and further stem cell
markers directed investigations are warranted to provide more
evidence of this finding.
Various extrinsic inducing factors incorporated in differentiation
protocols like; nicotinamide and exendin-4, besides their
inducing effects on differentiation markers, they are also having
inducing effects on pluripotency markers. That interesting
finding needs much further investigations and unravelling the
mechanism of action of various extrinsic inducing factors is
indeed warranted.
Summary and Conclusions
143
Unfortunately, the IPCs derived from all the studied protocols
could not attain mature glucose-responsive β-cell state, which
reflects their incomplete differentiation. This can be at least
partially explained by the sustained expression of stemness
markers together with the induced expression of β-cells markers.
Besides, the remaining detected levels of REST protein in all the
derived IPCs could also be an important contributing factor to
the impaired GSIS.
The knock down of REST via siREST unexpectedly negatively
affected the differentiation outcome of WJ-MSCs to IPCs. The
existence of a tightly controlled temporal regulation that requires
REST to be present in the initial induction early differentiation
stages, and to be absent in mature functioning β-cells could at
least partially explain such unexpected finding.
The genetic manipulation of REST as a putative new modality to
improve the differentiation outcome of WJ-MSCs to IPCs
appears to be far more complex than what we thought
previously.
Some sort of interplay might exist between REST, Oct-4, Sox-2,
and other unknown factors during the induction of
differentiation of WJ-MSCs to IPCs. That interplay might be
extended to other types of stem cells differentiating to IPCs. The
mechanism of such interplay if unraveled could provide putative
therapeutic targets for DM.
We were unable to find a consistent relation or direct regulation
of Oct-4 or Sox-2 by REST under control conditions, neither
when we used transient knock down via siREST, nor when we
used stable knock down via shREST lentivirus.
Summary and Conclusions
144
In conclusion, our results show that WJ-MSCs represent a
readily available, non-invasive, highly promising source of stem
cells for β-cell regeneration. Although, the abundance of literature
suggests that generation of IPCs from stem cells is feasible,
however many considerations like cells source, induction protocols
and mechanisms of differentiation, should be further explored
before the application of these cells to clinical treatment of DM.
Most importantly, the principal novel finding of the current study
is the co-expression of stem cell/pluripotency markers and β-cell
markers during the differentiation of WJ-MSCs to IPCs. Implying
the possible association of sustained expression of pluripotency
markers with the incomplete differentiation of IPCs obtained from
WJ-MSCs. Furthermore, the findings of the current study shed
lights on the possible interplay between REST and pluripotency
factors like Oct-4 and Sox-2 during the differentiation of WJMSCs
to IPCs. A novel finding which warrants further
investigations.
Finally, those findings open the door for further warranted
investigations to