Biomedical Engineering Reference
In-Depth Information
Dental Pulp Stem Cells
Adult multipotent mesenchymal stem cells named as dental pulp stem cells
(DPSCs) have been isolated from human dental pulp tissue or exfoliated teeth
[
148
]. These cells have the capacity of self-renewal and the ability to differentiate
into adipogenic, chondrogenic, and osteogenic lineages and are comparable to the
mesenchymal progenitor cells from the bone marrow. Govindasamy et al. [
149
]
showed that such DPSCs could also be induced to differentiate into cells of the
pancreatic lineage forming islet-like cell aggregates (ICAs) under specified culture
conditions. These ICAs were positive for many endocrine markers and were able
to release insulin in a glucose-dependent manner in vitro. The use of DPSCs for
the generation of b cells can be very useful because it is easier to obtain these cells
from the exfoliated teeth and, at the same time, can also provide an autologous
source of b cells.
Germline Stem Cells
Adult stem cells with multipotent potential also exist in the germline, called
germline stem cells (GSCs). The spermatogonial stem cells (SSCs), that are male
germline stem cells, can acquire embryonic stem cell-like properties under specific
culture conditions and are able to generate derivatives of the three embryonic germ
layers [
150
]. These cells can then be used to obtain many different tissues
including the pancreatic tissue [
151
]. Recently, researchers from Georgetown
University reported the generation of insulin-producing cells from human SSCs.
When transplanted into diabetic mice these cells were able to reduce hypergly-
cemia. This may provide an autologous source of b cells for male diabetics,
generated from their own stem cells. Researchers hope that they would be able to
apply this technique to female germline stem cells too. However, these results are
just preliminary and further work is required to establish the procedure [
152
].
9.5.3 Reprogramming of Adult Cells into b Cells and the Prospects
of Gene Therapy
Another way to generate functional b cells in vitro or in vivo is through trans-
differentiation of mature adult cells that is mostly achieved by forced expression of
certain b cell-associated transcription factors or in some cases by treatment with
various signaling molecules. For this approach, the best starting population
belongs to the pancreatic non-b cells (e.g., acinar cells) or non-pancreatic cells
(like those from liver and intestine). These cells would be comparatively easier to
reprogram because of their related developmental origin, as mentioned in the
previous section.
