MicroRNA-128 prevents apoptosis of mesenchymal stem cells by targeting Apaf-1

Abstract

Mesenchymal stem cells (MSCs) are highly specialized cells that can be derived from bone marrow. The unique qualities of differential and regenerative characteristics they possess make them a great tool for heart regeneration after injury. However, numerous barricades are lain ahead to pass preceding the pervasive application of their clinical use. The steep decrease in their viability upon encountering the hostile environment, the abatement of cell proliferation, and the augmentation of cell apoptosis occur and jeopardize the attachment and survival of MSCs after transplantation. Before MSCs can flaunt their regenerative qualities, the guarantee of their survival needs to be ensured. The apoptotic protease activating factor 1 (Apaf-1), a monomer residing in the cytosol in its inactive form, is a molecule that is activated for the assembly of the apoptosome. The apoptosome is known to recruit and cleave the initiator caspase-9 to begin the pro-apoptotic caspase cascade; thus the abatement of the apoptosome formation was hypothesized to be pivotal. To target Apaf-1, we used microRNAs (miRNAs), post-transcriptional regulators that bind to complementary sequences in the 3’UTR of mRNAs typically resulting in inhibition of mRNA translation or the degradation of mRNAs. In vitro results using bone marrow derived human MSCs (hMSCs) showed that when hypoxia-stimulated intrinsic apoptosis occured, expression levels of apoptotic signals amplified despite no change in Apaf-1. Contrastingly, once hMSCs were transfected with specific microRNA-128 (miR-128), expression levels of Apaf-1 and apoptosis declined while survival percentages increased indicating that miR-128 can regulate Apaf-1 to enhance survival. In accordance to the results, decreased detection of Annexin V/PI-labeled cells showed that miR-128 transfected hMSCs had lower apoptotic characters signifying higher survival efficacy. In conclusion, downregulation of Apaf-1 via miR-128 regulation established a significant decrease in apoptosis hence promoted the increase of MSC survival after transplantation.