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            <italic>β</italic>-cell neogenesis triggers the generation of new <italic>β</italic>-cells
from precursor cells. Neogenesis from duct epithelium is the
most currently described and the best documented process
of differentiation of precursor cells into <italic>β</italic>-cells. It is contributes
not only to <italic>β</italic>-cell mass expansion during fetal and
nonatal life but it is also involved in the maintenance of the
<italic>β</italic>-cell mass in adults. It is also required for the increase in
<italic>β</italic>-cell mass in situations of increase insulin demand (obesity,
pregnancy). A large number of factors controlling the differentiation
of <italic>β</italic>-cells has been identified. They are classified
into the following main categories: growth factors, cytokine
and inflamatory factors, and hormones such as PTHrP and
GLP-1. The fact that intestinal incretin hormone GLP-1
exerts a major trophic role on pancreatic <italic>β</italic>-cells provides
insights into the possibility to pharmacologically stimulate
<italic>β</italic>-cell neogenesis. This could have important implications
for the of treatment of type 1 and type 2 diabetes. Transdifferentiation,
that is, the differentiation of already differentiated
cells into <italic>β</italic>-cells, remains controversial.However, more
and more studies support this concept. The cells, which can
potentially “transdifferentiate” into <italic>β</italic>-cells, can belong to
the pancreas (acinar cells) and even islets, or originate from
extra-pancreatic tissues such as the liver. Neogenesis from intra-islet precursors also have been proposed and subpopulations
of cell precursors inside islets have been described
by some authors. Nestin positive cells, which have been considered
as the main candidates, appear rather as progenitors
of endothelial cells rather than <italic>β</italic>-cells and contribute to
angiogenesis rather than neogenesis. To take advantage of
the different differentiation processes may be a direction for
future cellular therapies. Ultimately, a better understanding
of the molecular mechanisms involved in <italic>β</italic>-cell neogenesis
will allow us to use any type of differentiated and/or undifferentiated
cells as a source of potential cell precursors.</p>
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Exp Diabesity Res. 2004; 5(2):111-121