Mechanisms of action of hESC-secreted proteins that enhance human and mouse myogenesis

Abstract

Adult stem cells grow poorly in vitro compared to embryonic stem cells, and in vivo stem cell maintenance and proliferation by tissue niches progressively deteriorates with age. We previously reported that factors produced by human embryonic stem cells (hESCs) support a robust regenerative capacity for adult and old mouse muscle stem/progenitor cells. Here we extend these findings to human muscle progenitors and investigate underlying molecular mechanisms. Our results demonstrate that hESC-conditioned medium enhanced the proliferation of mouse and human muscle progenitors. Furthermore, hESC-produced factors activated MAPK and Notch signaling in human myogenic progenitors, and Delta/Notch-1 activation was dependent on MAPK/pERK. The Wnt, TGF-β and BMP/pSmad1,5,8 pathways were unresponsive to hESC-produced factors, but BMP signaling was dependent on intact MAPK/pERK. c-Myc, p57, and p18 were key effectors of the enhanced myogenesis promoted by the hECS factors. To define some of the active ingredients of the hESC-secretome which may have therapeutic potential, a comparative proteomic antibody array analysis was performed and identified several putative proteins, including FGF2, 6 and 19 which as ligands for MAPK signaling, were investigated in more detail. These studies emphasize that a “youthful” signaling of multiple signaling pathways is responsible for the pro-regenerative activity of the hESC factors.

Numb Protects Human Renal Tubular Epithelial Cells From Bovine Serum Albumin‐Induced Apoptosis Through Antagonizing CHOP/PERK Pathway

“…Numb and Notch signaling interact with each other in modulating the balance of cell proliferation, differentiation, and apoptosis, affecting the development and function of many organs [McGill and McGlade, 2003]. It has also been found that MAPK/ PERK pathway positively regulates activation of Notch in a variety of cell-fate specification processes [Yousef et al, 2014]. In this study, we show that up-regulation of Numb expression suppressed BSA-induced CHOP, PERK expression, and PERK phosphorylation, while down-regulation of Numb expression increased BSA-induced CHOP, PERK expression, and PERK phosphorylation in HKCs.…”

WFIKKN1 and WFIKKN2: “Companion” proteins regulating TGFB activity

“…The concentration of WFIKKN1 in the serum also decreased with age in a Duchenne muscular dystrophy patient while it increased with age in controls [47]. Further, WFIKKN2 is one of the 32 most highly enriched proteins in human embryonic stem cells-conditioned medium [48] known to enhance the proliferation of mouse and human muscle progenitors.…”

“…The interaction between TGFB and WFIKKN1 could also lead to the enrichment of semi-latent complexes (not represented here). embryonic stem cells-conditioned medium, which is enriched in WFIKKN2, enhanced the proliferation of mouse and human muscle progenitors by activation of MAPK and Notch signaling and not Wnt, TGFB and BMP pathways [48].…”

Rotator cuff tear state modulates self-renewal and differentiation capacity of human skeletal muscle progenitor cells

“…7 While SMPs transition from a quiescent to active state in response to soluble factors released by injured muscle in vivo, 8 their activation can also be modulated by insoluble factors within the niche itself, 9,10 due to their location under the basement membrane surrounding muscle fibers. 11 Niche charac-teristics typically include substrate stiffness, 12 which for healthy muscle can range from 10 to 20 kiloPascals (kPa, a unit of stiffness), 13,14 extracellular matrix (ECM) protein composition, including basement membrane collagens and laminins, 15,16 and soluble growth and signals factors, [17][18][19][20] including Notch regulation, 8 HFG, 18 IGF-1, 19 oxytocin, 20 and p38 MAP kinase (MAPK) pathway activation. 21 Since SMPs are sensitive to these environmental cues, it is likely that tendon tear activates SMPs in RC muscles, as we have shown by an increase in the SMP population in muscle from partial RCT tears.…”

“…To determine if the lower regenerative capacity of SMPs in muscle from torn RCTs can be "rejuvenated" by the restoration of normal niche characteristics, we extended our previous observations of SMPs that were restricted to fibronectin-coated hydrogels 22 to more broadly determine whether or not SMPs isolated from supraspinatus, infraspinatus, and deltoid muscles from varying RCT tear states could be culture-expanded in muscle-mimetic niches. Using substrate stiffness, [12][13][14] ECM protein composition, 15,16 and soluble signals and growth factors, [17][18][19][20] we quantified the extent to which disease state influenced expansion and subsequent differentiation, finding that tear state alone had a substantial and long-lasting effect on SMP phenotype; tear-derived SMPs fused into multinucleated myotubes at greater rates but were less proliferative than controls despite normal niche conditions. These data correlated with ECM compositional differences between tear states obtained by HPLC-MS/MS, suggesting that intrinsic niche differences may have permanently reprogrammed SMPs, thus impairing repair post-reloading of muscle.…”