The enzyme aldehyde dehydrogenase (ALDH) is found in developing and multipotent cell populations, and is important for the production and regulation of retinoic acid, which controls β-cell differentiation in the pancreas. The role of ALDH-expressing cells in the formation of endocrine-like cells and co-localization with the putative stem cell marker CD133 has not been examined during human pancreatic development. This study focuses on the co-expression of CD133 on ALDH+ cells from the human fetal pancreas (18-22 weeks of fetal age) with transcription factors (TFs) central to endocrine cell development. Fluorescence-activated cell sorting demonstrated that cells with high ALDH activity (ALDHhi) had increased co-expression of CD133 and endocrine-lineage TFs when compared with cells with low ALDH (ALDHlo) expression. Hormone-expressing (insulin, somatostatin) and ductal cells (CK19) were noted in the ALDHhi population, while mesenchymal (vimentin) and endothelial (CD31) markers were predominantly found in ALDHlo cells. Culture of sorted ALDHhi or ALDHhi/CD133+ cells resulted in loss of endocrine TF, insulin, and CK19 expression. The formation of cell clusters from cultured ALDHhi or ALDHhi/CD133+ cells led to restored CK19 expression and showed endocrine TFs and insulin expression. In summary, pancreatic ALDHhi cells contain a heterogeneous CD133-enriched population with a subset of β-cell associated markers in the developing human pancreas.
Keywords: ALDH; cell sorting; human fetal pancreas; insulin-expressing cells.