Abstract
The skeletal muscle injury triggers the inflammatory response which is crucial for damaged muscle fiber degradation and satellite cell activation. Immunodeficient mice are often used as a model to study the myogenic potential of transplanted human stem cells. Therefore, it is crucial to elucidate whether such model truly reflects processes occurring under physiological conditions. To answer this question we compared skeletal muscle regeneration of BALB/c, i.e. animals producing all types of inflammatory cells, and SCID mice. Results of our study documented that initial stages of muscles regeneration in both strains of mice were comparable. However, lower number of mononucleated cells was noticed in regenerating SCID mouse muscles. Significant differences in the number of CD14-/CD45+ and CD14+/CD45+ cells between BALB/c and SCID muscles were also observed. In addition, we found important differences in M1 and M2 macrophage levels of BALB/c and SCID mouse muscles identified by CD68 and CD163 markers. Thus, our data show that differences in inflammatory response during muscle regeneration, were not translated into significant modifications in muscle regeneration.
Highlights
Skeletal muscle regeneration relies on the differentiation of tissue specific stem cells, i.e. satellite cells (Montarras et al 2013; Scharner and Zammit 2011)
We found important differences in M1 and M2 macrophage levels of BALB/c and severe combined immunodeficiency (SCID) mouse muscles identified by CD68 and CD163 markers
SCID mice are widely used in studies investigating myogenic potential of stem cells after transplantation into regenerating muscles (Arpke et al 2013; Brzoska et al 2006; Dellavalle et al 2007; Grabowska et al 2012, 2013; Morosetti et al 2010)
Summary
Skeletal muscle regeneration relies on the differentiation of tissue specific stem cells, i.e. satellite cells (Montarras et al 2013; Scharner and Zammit 2011). The activation of satellite cells, occurring in response to the muscle injury, is manifested by the resumption of the cell cycle and differentiation into myoblasts [reviewed in (Ciemerych et al 2011)]. Satellite cells start to proliferate approximately 18–24 h after the injury. At days 3 and 4 of regeneration the proliferation of mouse satellite cells is the most intense and it decreases during 7–10 days (Grounds and McGeachie 1987). At day 4 of regeneration satellite cells-derived myoblasts fuse into myotubes and subsequently into muscle fibers which formation is almost completed within 7–10 days after the injury (Robertson et al 1990). Within 14 days after the injury full restoration of muscle architecture and function is completed (Robertson et al 1993)
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