Inhibition of Methyltransferase Setd7 Allows the In Vitro Expansion of Myogenic Stem Cells with Improved Therapeutic Potential

Abstract

The development of cell therapy for repairing damaged or diseased skeletal muscle has been hindered by the inability to significantly expand immature, transplantable myogenic stem cells (MuSCs) in culture. To overcome this limitation, a deeper understanding of the mechanisms regulating the transition between activated, proliferating MuSCs and differentiation-primed, poorly engrafting progenitors is needed. Here, we show that methyltransferase Setd7 facilitates such transition by regulating the nuclear accumulation of β-catenin in proliferating MuSCs. Genetic or pharmacological inhibition of Setd7 promotes in vitro expansion of MuSCs and increases the yield of primary myogenic cell cultures. Upon transplantation, both mouse and human MuSCs expanded with a Setd7 small-molecule inhibitor are better able to repopulate the satellite cell niche, and treated mouse MuSCs show enhanced therapeutic potential in preclinical models of muscular dystrophy. Thus, Setd7 inhibition may help bypass a key obstacle in the translation of cell therapy for muscle disease.

Metabolic reprogramming of fibro/adipogenic progenitors facilitates muscle regeneration

“…Importantly, our network analysis revealed that the crucial hub β-catenin is also positively modulated by the diet in dystrophic FAPs. The transcriptional coactivator β-catenin plays a key role in controlling several biological processes in mesenchymal cells, including adipogenesis and fibrogenesis (Rudolf et al, 2016;Judson et al, 2018). Interestingly, HFD was already shown to regulate the expression of members of the Wnt signaling pathway in rodent models of diabetes and obesity (Chen et al, 2015).…”

“…FAPs were isolated from 49-d-old mdx mice fed with LFD or HFD (n = 3) and transduced through spinoculation (Judson et al, 2018) with one MOI of pLenti CMV GFP Hygro (Addgene). Briefly, 1.0 × 10 5 cells were plated in serum-free medium (DMEM GlutaMax) in six-well plate and one MOI of virus was administered dropwise.…”

Efficient engraftment of pluripotent stem cell-derived myogenic progenitors in a novel immunodeficient mouse model of limb girdle muscular dystrophy 2I

“…Due to the relatively low turnover in skeletal muscle, strategies to induce muscle injury prior to transplantation, such as CTX, barium chloride, cryoinjury, or irradiation, are commonly used to enhance the muscle regenerative response and therefore, better assessment of the repopulation potential of a given cell population [24,39,40]. This applies not only to non-disease mice but also to mouse models of MDs, such as the mdx for Duchenne MD [24,[41][42][43] and the α-sarcoglycan null for LGMD2D [44], among others. Attesting this, Vallese and colleagues have shown superior muscle engraftment following the transplantation of human myoblasts in cryoinjured recipient muscles when compared to non-injured counterparts [45].…”

Pim1 kinase positively regulates myoblast behaviors and skeletal muscle regeneration

“…Skeletal muscle has an ability of regeneration after injury due to its intrinsic stem cell reserve 1 . Skeletal muscle stem cells, also known as muscle satellite cells (SCs), reside between the plasma membrane and basal lamina in a quiescent state 2 . Once the skeletal muscle is damaged, the quiescent SCs are immediately activated to generate transient amplifying precursors called myoblasts 3 , which further differentiate and fuse either to form new multinucleated muscle fibers or to repair damaged parts of existing muscle fibers 1 .…”

“…So that in some special cases, such as extensive muscle trauma and severe myopathies, skeletal muscle will have difficulty initiating the regeneration program due to the exhaustion or functional defect of muscle SCs. Although some experimental studies and clinical trials based upon intramuscular myoblasts transplantation have shown encouraging results [6][7][8][9] , these outcomes are still of limited benefit ascribing to the poor ability of transplanted myoblasts to survival, expansion, and migrate 2,[10][11][12] . Therefore, exploring the intrinsic mechanisms of SCs self-renewal, proliferation, differentiation, and fusion has vital application value for the manipulation of SCs behaviors in vitro, as well as the restart of muscle regeneration program in vivo.…”