GARP is a key molecule for mesenchymal stromal cell responses to TGF-β and fundamental to control mitochondrial ROS levels

Abstract

Abstract Multipotent mesenchymal stromal cells (MSCs) have emerged as a promising cell therapy in regenerative medicine and for autoimmune/inflammatory diseases. However, a main hurdle for MSCs-based therapies is the loss of their proliferative potential in vitro. Here we report that glycoprotein A repetitions predominant (GARP) is required for the proliferation and survival of adipose-derived MSCs (ASCs) via its regulation of transforming growth factor-β (TGF-β) activation. Silencing of GARP in human ASCs increased their activation of TGF-β which augmented the levels of mitochondrial reactive oxygen species (mtROS), resulting in DNA damage, a block in proliferation and apoptosis. Inhibition of TGF-β signaling reduced the levels of mtROS and DNA damage and restored the ability of GARP−/lowASCs to proliferate. In contrast, overexpression of GARP in ASCs increased their proliferative capacity and rendered them more resistant to etoposide-induced DNA damage and apoptosis, in a TGF-β-dependent manner. In summary, our data show that the presence or absence of GARP on ASCs gives rise to distinct TGF-β responses with diametrically opposing effects on ASC proliferation and survival. Significance statement The expansion of multipotent mesenchymal stromal cells (MSCs) in vitro is associated with a decrease in their proliferative and therapeutic capacity making basic research on factors regulating MSC proliferation of fundamental importance for their successful translation into clinical applications. It is shown that glycoprotein A repetitions predominant (GARP) is critical for the proliferation and survival of adipose-derived MSCs (ASCs) in vitro. GARP prevents an aberrant transforming growth factor-β (TGF-β) response in ASCs, characterized by oxidative DNA damage and cell death, while inducing a productive TGF-β response that increases their proliferation and resistance to DNA damage. The data highlight the importance of GARP in controlling TGF-β activation/signaling in ASCs during in vitro expansion.