Characterization of Transplanted GFP⁺ Bone Marrow Cells into Adipose Tissue

¹ Thomas E. Starzl Transplantation Institute, Department of Surgery, University of Pittsburgh, Pittsburgh, PA
² Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA, McGowan Institute for Regenerative Medicine, Pittsburgh, PA
³ Division of Plastic Surgery, Department of Surgery, University of Pittsburgh, Pittsburgh, PA
⁴ McGowan Institute for Regenerative Medicine, Pittsburgh, PA, Division of Plastic Surgery, Department of Surgery, University of Pittsburgh, Pittsburgh, PA
⁵ McGowan Institute for Regenerative Medicine, Pittsburgh, PA, Division of Plastic Surgery, Department of Surgery, University of Pittsburgh, Pittsburgh, PA, Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA

^* To whom correspondence should be addressed. E-mail: marrak{at}upmc.edu.

	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. In order 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 evenly scattered around the adipocytes and blood vessels, while all CD45+ cells within the blood vessels were GFP+. A small fraction of GFP⁺ cells with 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 fat (subcutaneous) pad; a significantly higher number of GFP^-/CD90⁺ cells were isolated from the subcutaneous depot as compared to 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 ASCs generation might be minor.