Characterization of Transplanted Green Fluorescent Protein+ Bone Marrow Cells into Adipose Tissue

Abstract

Abstract Following transplantation of green fluorescent protein (GFP)-labeled bone marrow (BM) into irradiated, wild-type Sprague-Dawley rats, propagated GFP+ cells migrate to adipose tissue compartments. To determine the relationship between GFP+ BM-derived cells and tissue-resident GFP− cells on the stem cell population of adipose tissue, we conducted detailed immunohistochemical analysis of chimeric whole fat compartments and subsequently isolated and characterized adipose-derived stem cells (ASCs) from GFP+ BM chimeras. In immunohistochemistry, a large fraction of GFP+ cells in adipose tissue were strongly positive for CD45 and smooth muscle actin and were evenly scattered around the adipocytes and blood vessels, whereas all CD45+ cells within the blood vessels were GFP+. A small fraction of GFP+ cells with the mesenchymal marker CD90 also existed in the perivascular area. Flow cytometric and immunocytochemical analyses showed that cultured ASCs were CD45−/CD90+/CD29+. There was a significant difference in both the cell number and phenotype of the GFP+ ASCs in two different adipose compartments, the omental (abdominal) and the inguinal (subcutaneous) fat pads; a significantly higher number of GFP−/CD90+ cells were isolated from the subcutaneous depot as compared with the abdominal depot. The in vitro adipogenic differentiation of the ASCs was achieved; however, all cells that had differentiated were GFP−. Based on phenotypical analysis, GFP+ cells in adipose tissue in this rat model appear to be of both hematopoietic and mesenchymal origin; however, infrequent isolation of GFP+ ASCs and their lack of adipogenic differentiation suggest that the contribution of BM to ASC generation might be minor. Disclosure of potential conflicts of interest is found at the end of this article.