An anti-inflammatory role for leukemia inhibitory factor receptor signaling in regenerating skeletal muscle

Abstract

Skeletal muscle regeneration in pathology and following injury requires the coordinated actions of inflammatory cells and myogenic cells to remove damaged tissue and rebuild syncytial muscle cells, respectively. Following contusion injury to muscle, the cytokine leukemia inhibitor factor (LIF) is up-regulated and knockout of Lif negatively impacts on morphometric parameters of muscle regeneration. Although it was speculated that LIF regulates muscle regeneration through direct effects on myogenic cells, the inflammatory effects of LIF have not been examined in regenerating skeletal muscle. Therefore, the expression and function of LIF was examined using the antagonist MH35-BD during specific inflammatory and myogenic stages of notexin-induced muscle regeneration in mice. LIF protein and mRNA were up-regulated in two distinct phases following intramuscular injection of notexin into tibialis anterior muscles. The first phase of LIF up-regulation coincided with the increased expression of pro-inflammatory cytokines; the second phase coincided with myogenic differentiation and formation of new myotubes. Administration of the LIF receptor antagonist MH35-BD during the second phase of LIF up-regulation had no significant effects on transcript expression of genes required for myogenic differentiation or associated with inflammation; there were no significant differences in morphometric parameters of the regenerating muscle. Conversely, when MH35-BD was administered during the acute inflammatory phase, increased gene transcripts for the pro-inflammatory cytokines Tnf (Tumor necrosis factor), Il1b (Interleukin-1β) and Il6 (Interleukin-6) alongside an increase in the number of Ly6G positive neutrophils infiltrating the muscle were observed. This was followed by a reduction in Myog (Myogenin) mRNA, which is required for myogenic differentiation, and the subsequent number of myotubes formed was significantly decreased in MH35-BD-treated groups compared to sham. Thus, antagonism of the LIF receptor during the inflammatory phase of skeletal muscle regeneration appeared to induce an inflammatory response that inhibited subsequent myotube formation. We propose that the predominant role of LIF in skeletal muscle regeneration appears to be in regulating the inflammatory response rather than directly effecting myogenic cells.

Osteopontin ablation ameliorates muscular dystrophy by shifting macrophages to a pro-regenerative phenotype

“…The increased muscle strength observed in this investigation is highly likely to be related to the significant increase in macrophage expression of pro-regenerative factors insulin-like growth factor 1 (Barton et al, 2002), leukemia inhibitory factor (Barton et al, 2002;Hunt et al, 2013), and urokinase plasminogen activator (Suelves et al, 2007;Bryer et al, 2008). At the same time, no significant difference was observed in the expression of profibrotic factors such as fibronectin (Vidal et al, 2008;To and Midwood, 2011), C-C chemokine ligand 17 (Belperio et al, 2004;Yogo et al, 2009), and TGF-β (Fig.…”

“…8 A). On the contrary, OPN −/− mdx macrophages showed significantly increased expression of pro-regenerative factors, such as insulin-like growth factor 1 (Barton et al, 2002), leukemia inhibitory factor (Hunt et al, 2013), and urokinase plasminogen activator (Suelves et al, 2007; Fig. 8 B).…”

The Role of Leukemia Inhibitory Factor Receptor Signaling in Skeletal Muscle Growth, Injury and Disease

“…The sources of cells which can produce LIFR cytokines that are capable of exerting effects on muscle appear to include most of these possibilities; one such example is that macrophages can produce LIF and this acts as a chemotactic factor for myogenic precursor cells (Robertson et al 1993 ). We observed LIF immunoreactivity in injured muscle deriving from mononucleated cells, which could include infl ammatory cells such as macrophages or neutrophils (Hunt et al 2013 ). Nerve injury increases LIF expression and therefore the neurons or glial Schwann cells that comprise the nerve could be a source of LIF that can regulate muscle homeostasis (Ito et al 1998 ).…”

“…Fulfi lling this defi nition, LIF and other LIFR cytokines are indeed myokines. Whilst monitoring the administration of a LIF mutant, we detected a signifi cant increase in circulating endogenous LIF in the control group shortly after muscle injury (1 day) (Hunt et al 2013 ). This suggested that muscle damage may be one such stimulus, in addition to the aforementioned muscle stimulation or exercise, which induces LIF and myokine expression capable of acting as an endocrine.…”

Hyaluronan Synthesis and Myogenesis

“…The expression profile of Has2 associated best with macrophage accumulation or myoblast differentiation, myotube formation, and maturation (39).…”