Obesity impairs skeletal muscle repair through NID-1 mediated extracellular matrix remodeling by mesenchymal progenitors.

Obesity triggers skeletal muscle physio-pathological alterations. However, the crosstalk between adipose tissue and myogenic cells remains poorly understood during obesity. We identified NID-1 among the adipose tissue secreted factors impairing myogenic potential of human myoblasts and murine muscle stem cells in vitro. Mice under High Fat Diet (HFD) displayed increased NID-1 expression in the skeletal muscle endomysium associated with intramuscular fat adipose tissue expansion and compromised muscle stem cell function. We show that NID-1 is highly secreted by skeletal muscle fibro-adipogenic/mesenchymal progenitors (FAPs) during obesity. We demonstrate that increased muscle NID-1 impairs muscle stem cells proliferation and primes the fibrogenic differentiation of FAPs, giving rise to an excessive deposition of extracellular matrix. Finally, we propose a model in which obesity leads to skeletal muscle extracellular matrix remodeling by FAPs, mediating the alteration of myogenic function by adipose tissue and highlighting the key role of NID-1 in the crosstalk between adipose tissue and skeletal muscle. A. Adult skeletal muscle mesenchymal progenitor fibro-adipogenic potential in regular diet conditions. Undifferentiated multipotent PDGFRα-expressing progenitors (FAPs) are able to generate pre-adipocytes (NID-1 low) and fibrocytes (NID-1 high) committed to become adipocytes and fibroblast-like cells, respectively, under homeostatic and regeneration condition. B. Adult MuSCs myogenic potential under regular diet. During homeostasis, MuSCs are quiescent Pax7-expressing cells. Their role is maintaining the number of skeletal muscle progenitors throughout life. However, certain stimuli, such as muscle injury, launch the muscle regeneration program. Pax7 expression is downregulated at the time MyoD is expressed. Activated myoblasts undergo several cell cycles (Ki67+) to generate abundant number of myoblasts. Following differentiation, myoblasts decrease MyoD expression, and upregulate the commitment marker MyoG. Finally, myocytes fuse to repair or generate new myotubes. C. Adult skeletal muscle mesenchymal progenitor fibro-adipogenic potential after High-Fat Diet (HFD). HFD promotes FAP infiltration into obese mouse skeletal muscle. The surplus of energy stimulates transformation of the NID-1 Low FAP subpopulation into adipocytes and therefore, intramuscular adipose tissue deposition. The overstimulation of low NID-1 expressing FAPs forces their differentiation or trans-differentiation to NID-1 high expression FAPs. In obese mice under homeostatic conditions, most FAPs are expressing high levels of NID-1 which give rise to fibroblast-like cells upon regeneration. This in turn leads to excessive extracellular matrix deposition once the muscle damage is repaired. D. Obese mice adipose tissue secretome enhances FAP's fibrogenic fate during regeneration. E. Adult MuSCs myogenic potential after HFD. The increase in NID-1 secreting-FAPs alters the MuSCs niche. In the steady state, NID-1 may maintain the quiescence of Pax7 -expressing MuSCs, giving rise to a higher number of skeletal muscle progenitors. However, upon regeneration the persistence of NID-1 may blunt MuSCs clonal expansion and favor myoblast differentiation. [Display omitted] [ABSTRACT FROM AUTHOR]