Age‐related decline of interferon‐gamma responses in macrophage impairs satellite cell proliferation and regeneration

Abstract

Background Impaired muscle regeneration and increased muscle fibrosis are observed in aged muscle accompanied by progressive loss of muscle mass (sarcopenia). However, the underlying mechanism is still unclear. Methods The differentiated expressed genes in young and aged muscles after acute injury by cardiotoxin were identified by RNA-sequence analysis. Single-cell RNA-sequence analysis was used to identify cell clusters and functions in young muscle after acute injury, and flow cytometry analysis and sorting were used to validate the function. The proliferation and differentiation functions of satellite cells were accessed by immunostaining with 5-ethynyl-2′-deoxyuridine and embryonic myosin heavy chain (eMyHC), respectively. Muscle regeneration ability was accessed by histopathological and molecular biological methods. Results Gene expression patterns associated with responses to interferon-gamma (IFN-γ) (15 genes; false discovery rate < 0.001) were significantly down-regulated during muscle regeneration in aged mice (P = 2.25eÀ7). CD8 + T cells were the main source of increased IFN-γ after injury, adoptive transfer of wild-type CD8 + T cells to IFN-γ-deficient young mice resulted in 78% increase in cross-sectional areas (CSAs) of regenerated myofibres (P < 0.05) and 63% decrease in muscle fibrosis (P < 0.05) after injury. Single-cell RNA-sequence analysis identified a novel subset of macrophages [named as IFN-responsive macrophages (IFNRMs)] that specifically expressed IFN-responsive genes (Ifit3, Isg15, Irf7, etc.) in young mice at 3 days after injury, and the number of this macrophage subset was~20% lower in aged mice at the same time (P < 0.05). IFNRMs secreted cytokine C-X-C motif chemokine 10 (CXCL10) that promoted the proliferation and differentiation of satellite cells via its receptor, CXCR3. Intramuscular recombinant CXCL10 treatment in aged mice rejuvenated the proliferation of satellite cells (80% increase in Ki-67 + Pax7 + cells, P < 0.01) and resulted in 27% increase in CSA of regenerated myofibres (P < 0.01) and 29% decrease in muscle fibrosis (P < 0.05). Conclusions Our study indicates that decline in IFN-γ response in a novel subset of macrophage contributes to satellite cells dysfunctions in aged skeletal muscles and demonstrates that this mechanism can be targeted to restore age-associated myogenesis.

Metabolipidomic profiling reveals an age‐related deficiency of skeletal muscle pro‐resolving mediators that contributes to maladaptive tissue remodeling

“…Consistent with recent reports, we found that aged mice displayed marked defects in regenerating myofiber number and size (Blanc et al, 2020;Patsalos et al, 2018;Rahman et al, 2020;Zhang et al, 2020), but RvD1 treatment had minimal impact on this response. Aging is also well-established to limit recovery of muscle function following injury, due at least in part to an accumulation of fibrotic tissue during muscle regeneration (Rahman et al, 2020;Zhang et al, 2020).…”

“…Consistent with recent reports, we found that aged mice displayed marked defects in regenerating myofiber number and size (Blanc et al, 2020;Patsalos et al, 2018;Rahman et al, 2020;Zhang et al, 2020), but RvD1 treatment had minimal impact on this response. Aging is also well-established to limit recovery of muscle function following injury, due at least in part to an accumulation of fibrotic tissue during muscle regeneration (Rahman et al, 2020;Zhang et al, 2020). Indeed, we found that aged mice showed marked deficits in recovery of strength due to both reduced abilities of aged muscle to recover its pre-injury size as well as maladaptive tissue remodeling that further impaired relative contractile function.…”

Macrophage function in the elderly and impact on injury repair and cancer

“…TNF) observed in muscles of elderly patients (81 years old) male compared to young patients (23 years old) [99], and in muscles from aged C57BL/6J male mice [100]. Interestingly, following cardiotoxininduced injury, aged male C57BL/6J mice (24 months) showed decreased infiltration of macrophages into damaged muscle [101], which was associated with decreased chemokine secretion (particularly interferon-gamma inducible protein-10). This is similar to the delayed inflammatory infiltration previously observed with crosstransplantation young-old studies in aged female C57BL/6J mice [97], suggesting that the ageing microenviroment impacts chemotaxis [102].…”

The Roles of Macrophages in Heart Regeneration and Repair After Injury

“…On the one hand, this classification is not entirely consistent with the ideas of Mills who defined macrophages based on their function, and the macrophage types defined in these two ways actually have different gene signatures as shown by comparing transcriptomes between the M1/M2 and classically/alternatively activated types ( 39 , 40 ). On the other hand, it is an oversimplification to describe the spectrum of macrophage subsets using only two categories ( 34 , 41 – 43 ), which neglect the diversity of macrophages in distinct tissues and conditions ( 33 , 44 , 45 ). Some suggest that M1 and M2 are more like two extremes of macrophage polarization and that the observation of the complete process is limited by experimental methods ( 46 ).…”