Glioblastoma-dependent differentiation and angiogenic potential of human mesenchymal stem cells in vitro

Abstract

Tumor angiogenesis is of central importance in the malignancy of glioblastoma multiforme (GBM). As previously shown, human mesenchymal stem cells (hMSC) migrate towards GBM and are incorporated into tumor microvessels. However, phenotype and function of recruited hMSC remain unclear. We evaluated the differentiation and angiogenic potential of hMSC after stimulation with glioblastoma-conditioned medium in vitro. Immunostaining with endothelial, smooth muscle cell and pericyte markers was used to analyze hMSC differentiation in different concentrations of tumor-conditioned medium (CM), and the angiogenic potential was evaluated by matrigel-based tube-formation assay (TFA). Immunofluorescence staining revealed that tumor-conditioned hMSC (CM-hMSC) expressed CD 151, VE-cadherin, desmin, α-smooth muscle actin, nestin, and nerval/glial antigen 2 (NG2) in a CM concentration-dependent manner, whereas no expression of von-Willebrand factor (vWF) and smooth myosin could be detected. These findings are indicative of GBM-dependent differentiation of hMSC into pericyte-like cells, rather than endothelial or smooth muscle cells. Furthermore, TFA of hMSC and CM-hMSC revealed CM-dependent formation of capillary-like networks, which differed substantially from those formed by human endothelial cells (HUVEC), also implying pericyte-like tube formation. These results are indicative of GBM-derived differentiation of hMSC into pericyte-like mural cells, which might contribute to the neovascularization and stabilization of tumor vessels.

Human Glioblastoma-Derived Mesenchymal Stem Cell to Pericytes Transition and Angiogenic Capacity in Glioblastoma Microenvironment

“…It is also well-recognized that bm-MSCs can differentiate to pericytes by the stimulation of glioblastoma-conditioned medium [24]. However, whether and how gb-MSCs can differentiate to pericytes is still unclear.…”

“…Bone marrow mesenchymal stem cells are capable of differentiating into pericytes and participating in angiogenesis during tumor formation; additionally, human malignant gliomas recruit bm-MSCs to the peri-vascular niche [18, 23, 24]. Although glioma-associated mesenchymal stem cells have been reported to be recruited from normal tissue [23], the source of gb-MSCs is still controversial.…”

“…Several studies have demonstrated that MSCs can be recruited to gliomas and transform into pericytes to promote tumor angiogenesis [23, 24]. These reports may be controversial due to the different expression of CD90 between glioblastoma-derived MSCs and bone marrow-derived mesenchymal stem cells (bm-MSCs).…”

Perivascular niches as points of the utmost expression of tumor microenvironment

“…They are mostly absent in LGG or in mild infiltration areas of GB, but they become frequent after BBB disruption and the consequent starting of angiogenesis. Chemokines and their receptors largely take part in this process [27], among which CXCL12 (SDF-1)/ CXCR4, CX3CL1/CX3CR1 and CCL2/CCR2 are mainly involved, also in the niche function [8,38,39]. Of particular significance seems to be the expression of CXCL2 and VEGF in GAMs and of CXCR2 on endothelial cells that would indicate the angiogenic function of GAMs [11].…”

Tumor Microenvironment — Perivascular and Perinecrotic Niches

“…Pericytes are an essential element of the neurovascular unit and contribute to the function of blood-brain-barrier (BBB) [166]. Gliomas can induce the differentiation of MSCs into pericytes [167]. MSCs injected into brain tumors in mouse models have been shown to closely associate with the tumor vasculature and also with up-regulation of the expression of pericyte markers [168].…”