Enhanced proliferation and differentiation of Oct4- and Sox2-overexpressing human adipose tissue mesenchymal stem cells

Abstract

Mesenchymal stem cells (MSCs) are attractive candidates for clinical repair or regeneration of damaged tissues. Oct4 and Sox2, which are essential transcription factors for pluripotency and self-renewal, are naturally expressed in MSCs at low levels in early passages, and their levels gradually decrease as the passage number increases. Therefore, to improve MSC proliferation and stemness, we introduced human Oct4 and Sox2 for conferring higher expansion and differentiation capabilities. The Oct4-IRES-Sox2 vector was transfected into human adipose tissue MSCs (ATMSCs) by liposomal transfection and used directly. Oct4 and Sox2 were successfully transfected into ATMSCs, and we confirmed maintenance of MSC surface markers without alterations in both red fluorescent protein (RFP) (control) and Oct4/Sox2-ATMSCs. Enhanced proliferative activity of Oct4/Sox2-ATMSCs was shown by WST-1 assay, and this result was further confirmed by cell counting using trypan blue exclusion for a long period. In addition, FACs cell cycle analysis showed that there was a reduction in the fraction of Oct4/Sox2-ATMSCs in G1 with a concomitant increase in the fraction of cells in S, compared with RFP-ATMSCs. Increased levels of cyclin D1 were also seen in Oct4/Sox2-ATMSCs, indicating acceleration in the transition of cells from G1 to S phase. Furthermore, Oct4/Sox2-overexpressing ATMSCs showed higher differentiation abilities for adipocytes or osteoblasts than controls. The markers of adipogenic or osteogenic differentiation were also upregulated by Oct4/Sox2 overexpression. The improvement in cell proliferation and differentiation using Oct4/Sox2 expression in ATMSCs may be a useful method for expanding the population and increasing the stemness of ATMSCs.

Cell culture density affects the stemness gene expression of adipose tissue-derived mesenchymal stem cells

“…Another study demonstrated that Oct4/Sox2/Nanog overexpression improves the proliferation and differentiation of AT-MSCs (27,28). The stemness of MSCs following their homing is required for tissue repair.…”

“…Oct4, Sox2 and Klf4, which share many target genes in ESCs, are critical components of the pluripotency circuit to maintain the self-renewal capacity of undifferentiated ESCs. According to previous studies, Oct4, Sox2, Lin28 and Nanog regulate the proliferative capacity, colony formation and lineage differentiation potencies of MSCs (27,28,(30)(31)(32)(33)(34). As a key factor in reprogramming, Klf4 functions as a transcriptional activator and repressor to regulate the proliferation and differentiation of different cell types (35).…”

Correlation between telomere maintenance and stemness of mesenchymal stem/stromal cells

“…Contrary, in previous study, hTERT has been proposed to have a role in the upregulation of pluripotency marker expression in MSCs [35] . Although expression of pluripotency markers in adult stem cells is demonstrated in many studies [33,36] , their role is still not well defined. In some studies, pluripotency marker expression was shown to be related to MSCs stemness and undifferentiated status maintenance [37] , while other studies showed their overexpression was related to enhanced differentiation of MSCs [36,38] .…”

“…Although expression of pluripotency markers in adult stem cells is demonstrated in many studies [33,36] , their role is still not well defined. In some studies, pluripotency marker expression was shown to be related to MSCs stemness and undifferentiated status maintenance [37] , while other studies showed their overexpression was related to enhanced differentiation of MSCs [36,38] . This complexity is probably a consequence of questionable expression of pluripotency markers in MSCs, because these markers, such as Oct4 possess several pseudogenes which share high sequence homology to Oct-4A [39] and have non-pluripotency activities.…”

The effect ofId1gene silencing on the neural differentiation of MSCs

“…At present, stem cell-mediated therapies represent potential clinical treatments for degenerative diseases of the nervous system, including Parkinson's disease and spinal cord injury [8,9]. MSCs have the advantages of easy isolation, self-renewal and low immunogenicity, which facilitate allogenic transplantation without the need for immunosuppressive drugs [10,11]. Therefore, they are attractive candidates for clinical applications in the repair or regeneration of damaged tissues.…”