Experimental studies on malignant transformation of bone marrow mesenchymal stem cells induced by glioma stem cells

Abstract

Objective Both human glioma stem cell line SU3 transfected with red fluorescent protein(SU3-RFP)and bone marrow cells from green fluorescence protein(GFP)transgenic athymic nude mice were transplanted into bone marrow damage-reconstitution Balb/c nude mice to investigate the mutual interactions between bone marrow mesenchymal stem cells(BMSCs)and SU3-RFP in vivo. Methods After irradiation of bone marrow in Balb/c nude mice, allogeneic transplantation with GFP+ bone marrow cells was performed via caudal vein to establish bone marrow damage-reconstitution models. SU3-RFP cells were transplanted subcutaneously to the models and xenograft tumors were harvested; HE staining was performed and observation under laser scanning confocal microscope was performed. Primary culture of the xenograft tumors was performed to sort and clone the high proliferative GFP+ cells. Immunocytochemical staining was employed to detect the expressions of CD44, Sca1, CD90 and CD45 in BMSCs; proliferation, clone formation rate and invasive ability of GFP+ cells, BMSCs and SU3-RFP were detected by CCK-8 method, cell clone formation experiment and Transwell invasion assay, respectively. Karyotype analysis was used to analyze the chromosome morphology of BMSCs. High proliferative GFP+ cells were inoculated into the subcutaneous of Balb/c nude mice, and the tumor tissues were harvested to perform HE staining. Results The tumor formation rate of SU3-RFP cells in the bone marrow reconstitution models was 100%(7/7). HE staining indicated that the tumors were rich in blood vessels and erythrocytes in the lumen. Active interaction was noted between BMSCs and SU3-RFP. The high proliferative GFP+ cells and BMSCs both had strong CD44 expression, Sca1 and CD90 weakly positive expression, and CD45 negative expression, and these cells were named transformational BMSCs(tBMSCs). The proliferation and clone formation rate and invasive ability of tBMSCs and SU3-RFP were significantly higher than those of BMSCs(P< 0.05). The number of mitosis phase chromosome in tBMSCs was obviously larger than that in BMSCs. High proliferative ability, telocentric(murine)chromosome with ultra-pentaploid and 100% tumorigenicity rate(5/5)in Balb/c nude mice were observed. Conclusion Malignant transformation of BMSCs induced by glioma stem cells could occur in the bone marrow damage-reconstitution nude mice xenograft tumor models, and participate in the remodeling of tumorigenesis and development. Key words: Glioma stem cell; Bone marrow damage-reconstitution model; Bone marrow mesenchymal stem cell; Malignant transformation