Differentiation and Homing of Transplanted Bone Marrow Cells in Livers of Murine Schistosomiasis: Pilot Study

Recent reports have demonstrated the capacity of bone marrow (BM) stem cells to transdifferentiate into hepatocytes. The efficiency of differentiation of bone marrow cells (BMC's) into hepatocytes in vivo and its importance in physiopathologic processes is still debated. The present study was designed to highlight part of the potential capabilities of bone marrow cells and their role in cell based therapy in hepatic diseases, we used the murine model of schistosomiasis. Using the murine model of schistosomiasis as a chronic liver injury, unfractionated male mice (BMC's) were transplanted through intravenous (IV) injection into tail vein of non irradiated gender mismatched Schistosoma mansoni (S. mansoni) infected female mice on their 16 week post infection (PI). Two th weeks after BM transplantation, the sacrification schedule started: Mice were sacrificed at one week interval for a period of 10 weeks (from 18 28 week post infection) and their livers were fixed th th in standard buffered formalin and processed for both the light, electron and immunoflurescenc (IF) microscopic studies .The morphological changes of the liver tissue were studied by light and electron microscopes (EM). Tracing of male donor derived cells was done by the detection of Y chromosome by FISH and also Y-chrosome protein (CDYL) by indirect immunoflourescence (IF) in female injured livers. Transformation into hepatocytes was studied by indirect IF using antibodies directed against mouse albumin within BM cells in a test vitro culture for 7 days. Histopathological and electron microscopic examinations of the liver sections of infected female recipients; transplanted (Tx) with BMC's, revealed focal appearance of small scattered hepatocyte like cells exhibiting small rounded centrally located nuclei as well as oval cells with relatively large nuclei facing the sinusoids and scattered in hepatic parenchyma. A marked proliferation of primitive and incomplete small groups of bile ductules lined by epithelial cells with abundant effaced faint pink cytoplasm and central small nuclei at the perigranulomatous areas at the portal tracts were also observed. A relative increase in the newly formed small blood vessels especially surrounding the periovular schistosomal granulomas was seen. These cells were only observed in the infected Tx female mice group. They were neither observed in the non Tx schistosoma mansoni infected control mice group, nor in the other control group which was Tx with BMC's without being infected. With increased post transplantation time; starting from 4 week, post transplantation, an increase in the number of these newly formed bile th ductules and small hepatocyte like cells and blood vessels was noticed. Donor derived cells showing Y chromosome by FISH and also CDYL protein by IF were recovered in the female infected Tx with male BMC's livers. Cells were mainly localized in the periphery of schistosoma granuloma, hepatic parenchyma and periportal areas. Most of the donor derived engrafted cells seemed to be vascular, inflammatory cells and bile ductules together with few hepatic like cells. Only few donor derived cells appeared within the hepatic parenchymal tissue, and showed positivity for Y chromosome and Y protein and for albumin secretion by IF. Unfractionated BMC's can repopulate the injured schistosomiasis liver without immuno suppression. The extent of liver injury, the timing of cell administration, the threshold number of transplanted cells and the interplay of cytokines in the liver pathology are all important variables in the process of engraftment and differentiation that still need to be further defined. However, the transformation of bone marrow derived stem cells into viable hepatocytes sustains the idea of in vivo cell transplantation to be a successful therapeutic approach.