Isolation and characterization of mesenchymal stem cells from cultured human pancreatic islets of langerhans

Replacement of insulin producing β-cells that reside within pancreatic islets
represents an almost ideal treatment for patients with diabetes mellitus type
1. But, transplantation of pancreatic islets or the entire pancreas is limited by
the lack of donor organs. Stem cell derived insulin producing β-cells represent
an attractive alternative. The major goal of our research project is the ex vivo
generation of insulin producing cells using adult human stem cells that
express nestin. Nestin is an intermediate filament protein that was originally
described as a marker for embryonic and adult stem / progenitor cells of the
central nervous system. Recently it has been also proposed to be a potential
stem cell marker in rodent and human islets of Langerhans. Role and function
of nestin positive pancreatic cells during development or adult life however
are not well defined and matter of controversial debates. The first aim of our
research project was to isolate a pure population of nestin expressing cells
from human pancreatic islets of Langerhans for further characterization. For
this purpose single cell derived colonies were isolated from cultured human
islets. These colonies were immortalized and in a second step selected for cells
with highest nestin promoter activity using promoter targeted selection of
nestin expressing cells. The second aim was to characterize these cell lines
especially their stem cell properties and differentiation potential. We
characterized them finally as potential mesenchymal stem cells (MSC) of
pancreatic origin based on their expression of different stem cell markers
including nestin together with the transcription factor Islet-1 (Isl-1) and their
ability to differentiate in vitro into mesoderm lineages (adipocytes and
osteoblast-like cells). We could also demonstrate that they are multipotential
and capable of differentiation into albumin producing liver-like cells in vivo
and cells with a pancreatic endocrine phenotype in vitro. Based on these
observations, we wanted to test the hypothesis that human nestin expressing
MSC from bone marrow and adipose tissue could equally harbour the
potential to differentiate into insulin producing cells ex vivo. We found that
bone marrow and adipose tissue derived MSC are also able to differentiate
into cells expressing various pancreatic endocrine genes in vitro including
several crucial transcription factors as well as the islet hormones insulin and
glucagon. As a limitation of the presented work, we were not yet able to
generate functional cells that secrete insulin in response to glucose. But, we
can show for the first time that nestin positive MSC isolated from human
adult pancreas, bone marrow and adipose tissue represent stem / progenitor
cells with the potential to induce pancreatic developmental genes. These cells
may have the capacity to become insulin secreting cells if further manipulated
and exposed to appropriate microenvironment.