Mesenchymal stem cells (MSC) are isolated from bone marrow or other tissues, and have properties of self renewal and multilineage differentiation ability. The current study investigated the in vitro differentiation potential of porcine bone marrow derived MSCs into hepatocyte-like cells. The MSC were isolated from the bone marrow of adult miniature pigs (7 months old, T-type, PWG Micro-pig®, PWG Genetics, Seoul, Korea) and adherent cells with fibroblast-like morphology were cultured on plastic. Isolated MSCs were positive for CD29, CD44, CD73, CD90, and vimentin, and negative for CD34, CD45, major histocompatibility complex-class II (MHC-class II), and swine leukocyte antigen-DR (SLA-DR) by flow cytometry analysis. Further, trilineage differentiation of MSC into osteocytes (alkaline phosphatase, von Kossa and Alizarin red), adipocytes (Oil Red O), and chondrocytes (Alcian blue) was confirmed. Differentiation of MSC into hepatocyte-like cells was induced with sequential supplementation of growth factors, cytokines, and hormones for 21 days as described previously (Taléns-Visconti et al. 2006 World J. Gastroenterol. 12, 5834–5845). Morphological analysis, expression of liver-specific markers, and functional assays were performed to evaluate the hepatic differentiation of MSC. Under hepatogenic conditions, MSC acquired cuboidal morphology with cytoplasmic granules. These hepatocyte-like cells expressed α-fetoprotein (AFP), albumin (ALB), cytokeratin 18 (CK18), cytochrome P450 7A1 (CYP7A1), and hepatocyte nuclear factor 1 (HNF-1) markers by immunofluorescence assay. In addition, the expression of selected markers was demonstrated by Western blotting analysis. In accordance with these features, RT-PCR revealed transcripts of AFP, ALB, CK18, CYP7A1, and HNF-1α. Further, the relative expression levels of these transcripts were analysed by quantitative RT-PCR after normalizing to the expression of the endogenous control, glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Data were analysed statistically by one-way ANOVA using PASW statistics 18 (SPSS Inc., Chicago, IL, USA), and significance was considered at P < 0.05. The results showed that the relative expressions of selected marker genes in hepatocyte-like cells were significantly increased compared with that in untreated MSC. The generated hepatocyte-like cells showed glycogen storage as analysed by periodic acid-Schiff (PAS) staining. Moreover, the induced cells produced urea at Day 21 of culture compared with control MSC. In conclusion, our results indicate the potential of porcine MSC to differentiate in vitro into hepatocyte-like cells. Further studies on the functional properties of hepatocyte-like cells are needed to use porcine MSC as an ideal source for liver cell therapy and preclinical drug evaluation.
This work was supported by Basic Science Research Program through the National Research Foundation (NRF), funded by the Ministry of Education, Science and Technology (2010-0010528) and the Next-Generation BioGreen 21 Program (No. PJ009021), Rural Development Administration, Republic of Korea.
In utero xenotransplantation of mice bone marrow-derived stromal/stem cells into fetal rat liver: A preliminary study