Effects Of Bone Marrow-derived Flk1～+ CD31～-CD34～- Mesenchymal Stem Cells On TNBS-induced Ulcerative Colitis In Mice

Objective It has been shown that mesenchymal stem cells (MSCs) from bone marrow could engraft in the gastrointestine after injury and possess prominent immunosuppressive activity. This study was designed to evaluate the therapeutical effect of Flkl~+CD31~-CD34~-MSCs from enhanced green fluorescent protein (EGFP) mice bone marrow(BM) on ulcerative colitis (UC) model mice.Methods MSCs were isolated and cultured; their phenotype and biological characteristics were studied. Cell cycle and phenotype of MSCs were analyzed by measuring DNA content by flow cytometer. A TNBS-induced UC model was used. Flk1~+CD31~-CD34~-MSCs were systemically infused immediately after mice were challenged with TNBS. Control mice received only saline infusion. UC histopathologic examination was conducted on several time points and donor-cell engraftment was assessed 2 weeks later after Flk1~+CD31~-CD34~-MSCs infusion with immunohistochemical technology.Results MSCs were characterized by a typical fibroblast like morphology. Cell cycle analysis by flow cytometry revealed that more than 94% of cells were in the G0/G1 phases, while a small population of cells were actively engaged in proliferation (S+G2+M=5.8%). We also showed that more than 91% of cells were positive stained by FITC labeled CD29, CD44, CD105, Flk-1, and only about 1-3% of cells positive for CD31, CD34, CD45, HLA-DR. We found that Flk1~+CD31~-CD34~-MSCs transplantation immediately after exposure to TNBS, significantly reduced TNBS-induced UC colon mucosal damage, histologic examination suggested that colon mucosal damage recovery was much better in these Flk1~+CD31~-CD34~-MSCs-treated mice. More importantly, we could...