ABSTRACT
As a source of hematopoietic stem cells [HSCs], umbilical cord blood [UCB] has the advantages of speed of availability, tolerance of more than one HLA mismatch, and a low incidence of severe graft-versus-host disease [GVHD]. Hence, it represents a promising, alternative non-costly and non-invasive source for prospective stem cell based therapy. In this study we investigated the angiogenic potential of ex vivo expanded human umbilical cord blood CD 133* stem cells transplanted into mice with chronic hepatic fibrosis induced by Schistosomiasis infection. Histopathological, ultrastructural and immunohistochemical analysis of mice liver sections were done to detect specific human angiogenic markers. Umbilical cord blood was obtained from healthy pregnant females after delivery and mononuclear cells were collected by density gradient using Ficoll Hypaque. Enrichment for the CD 133* stem cells was done by positive selection using the Magnetic Activated Cell Sorting system and magnetic microbeads. Cells were cultured in prirnaly ex vivo expansion medium for three weeks. Flowcytomeric analysis of the cultured cells was done in each step to identify the CD 133* cells. Schistosomiasis was induced in Swiss Albino mice by intradermal injection of schistosoma cercariae. Twenty two weeks post schistosoma infection a total of 0.3 x 106 human CD 133* stem cells were injected intrahepatically in mice. Accordingly, mice were divided into three groups: Group 1 [infected, transplanted]; Group 2 [infected controls] and Group 3 [healthy, transplanted]. All mice were sacrificed 3 wks after cell transplantation was done in groups I and 3. Histopathology and Electron microscopy showed an obvious increase in the capillary network and the small blood vessels and a decrease in the fibrosis known for this stage of the disease. By immunohistochemical analysis the cellular constituents of these newly formed blood vessels showed positive expression of the human-specific angiogenic markers CD31, CD34 and von Willebrand Factor [vWF]. Few hepatocyte like polygonal cells showed positive expression of human Vascular Endothelial Growth Factor [VEGF] and inducible Nitric Oxide Synthase [iNOS]. Ex vivo expanded CD 133* human stem cells incorporate into the liver of schistosoma infected mice enhancing local angiogenesis and hepatic neovascularization. These preliminary results obtained suggest a dual benefit of CD 133* cells in cell therapy in hepatic diseases based on its capability of hematopoietic and endothelial differentiation. We suggest that the CD 133* cells contribute to repair in a paracrine manner by creating a permissive environment that enables rapid proliferation and survival of damaged cells rather than through direct differentiation to hepatocytes