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IDENTIFICATION OF A MARKER TO ENRICH POPULATIONS OF ENDOCRINE CELL PRECURSORS FROM THE HUMAN FETAL PANCREAS

Isolation of the endocrine cell precursors from the human fetal pancreas is important for the understanding of islet cytodifierentiation. The progenitor cells, from which all four islet endocrine cell types arise, are present within the epithelium ol the fetal pancreatic duct. Following enzymatic digestion and culture of the fetal pancreas WG obtained cell clusters resembling islets but with a high content of undifferentiated cells. Histochemical staining revealed very high acid β-galaclosidase activity in most cells within the clusters. After transplantation into athymic nude mice, the clusters gave rise to tissue rich in differentiated endocrine cells. The histochemical finding of high acid β-galactosidase activity was confirmed by direct measurement of lysosomal enzyme activities. In addition, we found that the expression of acid β-galactosidase was developmentally regulated, peaking at 18-24 weeks gestation and declining to low levels in adult islets. Using a fluorogenic β-galactosidase substrate, we were able to enrich for a subpopulation of cells high in acid β-galactosidase activity with flow cytometry. Evidence identifying these cells as potential islet cell precursors included, besides the transplantation experiments, the colocalization in vitro of lyrosine hydroxylase, a known marker of embryonic islet cells. Thus, our results indicate that high acid β-galactosidase activity serves as a marker to enrich populations of endocrine cell precursors.