Hepatocyte-conditioned medium sustains endothelial differentiation of human hematopoietic-endothelial progenitors.

UNLABELLED: Liver neo-angiogenesis plays a fundamental role in physiological and pathological processes such as regeneration, cirrhosis, autoimmune hepatitis, and alcoholic liver disease. How liver parenchymal cells influence angiogenesis is largely unknown. We studied the influence of soluble factors released by hepatocytes on hematopoietic and endothelial cell differentiation. Human CD34+ cells cultured for several weeks in a hepatocyte-conditioned medium gradually decrease the expression of CD34 and CD133 markers (i.e. after 4 weeks from 85% and 69%, respectively, to 6% and 3%, respectively), whereas expression of CD144 and CD14 cell markers increased (from 2% and 8%, respectively, to 54% and 55%, respectively). The cells' capacity to form hematopoietic colonies in methylcellulose declined with time, whereas they acquired endothelial morphology, expressed endothelial markers, and incorporated into newly forming vascular structures both in vitro and in vivo. Cultured single CD34+ cells formed colonies expressing both hematopoietic (CD45+) and endothelial (CD144+) markers, suggesting they constitute a bona fide hemangioblast population. CONCLUSION: This system allowed subsequent stages of differentiation of hematopoietic cells to endothelial cells to be defined, underlining the strict interrelationship between endothelial and hematopoietic cells in a hepatocyte environment.

3,5,3'-Triiodo-L-thyronine enhances the differentiation of a human pancreatic duct cell line (hPANC-1) towards a beta-cell-Like phenotype.

The thyroid hormone, 3,5,3'-Triiodo-L-thyronine (T3), is essential for growth, differentiation, and regulation of metabolic functions in multicellular organisms, although the specific mechanisms of this control are still unknown. In this study, treatment of a human pancreatic duct cell line (hPANC-1) with T3 blocks cell growth by an increase of cells in G(0)/G(1) cell cycle phase and enhances morphological and functional changes as indicated by the marked increase in the synthesis of insulin and the parallel decrease of the ductal differentiation marker cytokeratin19. Expression analysis of some of the genes regulating pancreatic beta-cell differentiation revealed a time-dependent increase in insulin and glut2 mRNA levels in response to T3. As last step of the acquisition of a beta-cell-like phenotype, we present evidence that thyroid hormones are able to increase the release of insulin into the culture medium. In conclusion, our results suggest, for the first time, that thyroid hormones induce cell cycle perturbations and play an important role in the process of transdifferentiation of a human pancreatic duct line (hPANC-1) into pancreatic-beta-cell-like cells. These findings have important implications in cell-therapy based treatment of diabetes and may provide important insights in the designing of novel therapeutic agents to restore normal glycemia in subjects with diabetes.