COMMUNICATION 1801326 (1 of 7)

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Adipose-derived stromal/stem cells (ASCs) represent a widely used cell source with multi-lineage differentiation capacity in approaches for tissue engineering and regenerative medicine. Despite the multitude of literature on their differentiation capacity, little is reported about the physiological properties contributing to and controlling the process of lineage differentiation. Direct intercellular communication between adjacent cells via gap junctions has been shown to modulate differentiation processes in other cell types, with connexin 43 (Cx43) being the most abundant isoform of the gap junction-forming connexins. Thus, in the present study we focused on the expression of Cx43 and gap junctional intercellular communication (GJIC) in human ASCs, and its significance for adipogenic differentiation of these cells. Cx43 expression in ASCs was demonstrated histologically and on the gene and protein expression level, and was shown to be greatly positively influenced by cell seeding density. Functionality of gap junctions was proven by dye transfer analysis in growth medium. Adipogenic differentiation of ASCs was shown to be also distinctly elevated at higher cell seeding densities. Inhibition of GJIC by 18α-glycyrrhetinic acid (AGA) significantly compromised adipogenic differentiation, as demonstrated by histology, triglyceride quantification, and adipogenic marker gene expression. Flow cytometry analysis showed a lower proportion of cells undergoing adipogenesis when GJIC was inhibited, further indicating the importance of GJIC in the differentiation process. Altogether, this study demonstrates the impact of direct cell-cell communication via gap junctions on the adipogenic differentiation process of ASCs, and may contribute to further integrate direct intercellular crosstalk in rationales for tissue engineering approaches.

BackgroundThe human endogenous retrovirus K (HERV-K) has been acquired by the genome of human ancestors million years ago. It is the most complete of the HERVs with transcriptionally active gag, pol and env genes. Splice variants of env, which are rec, 1.5 kb transcript and Np9 have been suggested to be tumorigenic. Transcripts of HERV-K have been detected in a multitude of human cancers. However, no such reports are available concerning glioblastomas (GBM), the most common malignant brain tumor in adults. Patients have a limited prognosis of 14.6 months in median, despite standard treatment. Therefore, we elucidated whether HERV-K transcripts could be detected in these tumors and serve as new molecular target for treatment.FindingsWe analyzed human GBM cell lines, tissue samples from patients and primary cell cultures of different passages for HERV-K full length mRNA and env, rec and 1.5 kb transcripts. While the GBM cell lines U138, U251, U343 and GaMG displayed weak and U87 strong expression of the full length HERV-K, the splice products could not be detected, despite a weak expression of env mRNA in U87 cells. Very few tissue samples from patients showed weak expression of env mRNA, but none of the rec or 1.5 kb transcripts. Primary cells expressed the 1.5 kb transcript weakly in early passages, but lost HERV-K expression with extended culture time.ConclusionsThese data suggest that HERV-K splice products do not play a role in human malignant gliomas and therefore, are not suitable as targets for new therapy regimen.

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