Abstract
Introduction: Angiogenesis induced by bone marrow mesenchymal stem cells (MSCs) obtained from aged mice is inferior to those obtained from young mice, but is improved following exposure to conditioned media (CM) from young MSCs. To define alterations in gene expression and signaling pathways underlying the observed angiogenic improvement, we characterized differences in cellular mRNA expression between “non-rejuvenated” and “rejuvenated” (exposed to CM from young MSCs) old MSCs. Methods: Replicates of 105 MSCs isolated from old (18-24 months) C57BL mice (n=6) were cultured separately, or in co-culture with MSCs from young (4-6 weeks, n=6) mice using 0.4μm Transwell plates that allow transfer of soluble factors, but not of cells. After 7d in culture, mRNA from old and rejuvenated MSCs was isolated and sequenced. Analysis was performed using open source Galaxy pipeline. Transcription factor (TF) and miRNA target enrichment analyses were performed using ChEA3 and MIENTURNET. Results: Of the 529 unique transcripts involved in angiogenesis (GO-ID 0001525), 98 differentially expressed transcripts (Bonferroni p < 0.0001) were identified. The rejuvenated MSCs showed significantly increased expression of 39 genes. The majority of these involved canonical angiogenic pathways and/or regulation of VEGF: JAK1, LOXL2, KLF4, BMP4, and ADM. Top enriched TFs and miRNAs included EPAS1 and miR-20a, respectively, both directly involved in VEGF signaling, along with SOX18, SNAI1, SOX7, miR-126a, and miR-499 (FDR < 0.05), all of which are known to promote either angiogenesis and/or stemness. Conclusions: Improved angiogenesis by old MSCs exposed to CM from young MSCs is accompanied by significant modulation of angiogenic mediators, crucial in both VEGF and non-VEGF signaling pathways. These changes suggest targets for transcriptional modification to improve angiogenesis and tissue repair in aged patients.
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