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We isolated a population of proliferating cells from cultured human fetal hepatocytes of 16–22 weeks gestational age. The cells shared a similar phenotype to that of mesenchymal stromal cells (MSCs) according to the International Society for Cellular Therapy (ISCT), including plastic adherence,antigen expression profile, and in vitromultilineage differentiation potential. Fetal liver (FL)-MSCs expressed the albumin gene, and harbored a subpopulation of CK18+cells (20–40%), which defined their hepatic origin. However, when subjected to in vitrohepatic differentiation, FL-MSCs did not acquire significant liver functions. Quantitative analysis of conditioned medium (CM) collected from cultured cells revealed the presence of growth factors and chemokines with potential liver regenerative properties, the most relevant of which (concentration ≥3000 pg/ml) were SDF-1 alpha, IL-6, MCP-1, IL-8, MIP-1 beta, VEGF-A, Gro-alpha, and HGF. Culturing of FL-MSCs as spheroids significantly enhanced the secretion of HGF and bFGF (approximately 5-fold) compared with culture monolayers. Moreover, CM assessed in vitroinduced capillary-like organization and migration of human umbilical vein endothelial cells (HUVECs) and fibroblasts as target cells. Interestingly, exosomes isolated from CM induced similar cellular responses in vitrowith high efficiency and in a dose-dependent manner.

This study was designed to assess liver-specific functions of human fetal liver cells proposed as a potential source for hepatocyte transplantation. Fetal liver cells were isolated from livers of different gestational ages (16-22 weeks), and the functions of cell preparations were evaluated by establishing primary cultures. We observed that 20- to 22-week-gestation fetal liver cell cultures contained a predominance of cells with hepatocytic traits that did not divide in vitro but were functionally competent. Fetal hepatocytes performed liver-specific functions at levels comparable to those of their adult counterpart. Moreover, exposure to dexamethasone in combination with oncostatin M promptly induced further maturation of the cells through the acquisition of additional functions (i.e., ability to store glycogen and uptake of indocyanine green). In some cases, particularly in cultures obtained from fetuses of earlier gestational ages (16-18 weeks gestation), cells with mature hepatocytic traits proved to be sporadic, and the primary cultures were mainly populated by clusters of proliferating cells. Consequently, the values of liver-specific functions detected in these cultures were low. We observed that a low cell density culture system rapidly prompted loss of the mature hepatocytic phenotype with downregulations of all the liver-specific functions. We found that human fetal liver cells can be cryopreserved without significant loss of viability and function and evaluated up to 1 year in storage in liquid nitrogen. They might, therefore, be suitable for cell banking and allow for the transplantation of large numbers of cells, thus improving clinical outcomes. Overall, our results indicate that fetal hepatocytes could be used as a cell source for hepatocyte transplantation. Fetal liver cells have been used so far to treat end-stage liver disease. Additional studies are needed to include these cells in cell-based therapies aimed to treat liver failure and inborn errors of metabolism.

We report that cells from human fetal dermis, termed here multipotent fetal dermal cells, can be isolated with high efficiency by using a nonenzymatic, cell outgrowth method. The resulting cell population was consistent with the definition of mesenchymal stromal cells by the International Society for Cellular Therapy. As multipotent fetal dermal cells proliferate extensively, with no loss of multilineage differentiation potential up to passage 25, they may be an ideal source for cell therapy to repair damaged tissues and organs. Multipotent fetal dermal cells were not recognized as targets by T lymphocytes in vitro, thus supporting their feasibility for allogenic transplantation. Moreover, the expansion protocol did not affect the normal phenotype and karyotype of cells. When compared with adult dermal cells, fetal cells displayed several advantages, including a greater cellular yield after isolation, the ability to proliferate longer, and the retention of differentiation potential. Interestingly, multipotent fetal dermal cells expressed the pluripotency marker SSEA4 (90.56 ± 3.15% fetal vs. 10.5 ± 8.5% adult) and coexpressed mesenchymal and epithelial markers (>80% CD90+/CK18+cells), coexpression lacking in the adult counterparts isolated under the same conditions. Multipotent fetal dermal cells were able to form capillary structures, as well as differentiate into a simple epithelium in vitro, indicating skin regeneration capabilities.