Immunoneutralization of TGFβ1 Improves Skeletal Muscle Regeneration: Effects on Myoblast Differentiation and Glycosaminoglycan Content

Abstract

When injured by crushing, the repair of the slow-twitch soleus rat muscle, unlike the fast-twitch EDL, is associated with fibrosis. As TGFβ1, whose activity can be controlled by glycosaminoglycans (GAG), plays a major role in fibrosis, we hypothesized that levels of TGFβ1 and GAG contents could account for this differential quality of regeneration. Here we show that the regeneration of the soleus was accompanied by elevated and more sustained TGFβ1 level than in the EDL. Neutralization of TGFβ1 effects by antibodies to TGFβ1 or its receptor TGFβ-R1 improved muscle repair, especially of the soleus muscle, increased in vitro growth of myoblasts, and accelerated their differentiation. These processes were accompanied by alterations of GAG contents. These results indicate that the control of TGFβ1 activity is important to improve regeneration of injured muscle and accelerate myoblast differentiation, in part through changes in GAG composition of muscle cell environment.

Decrease of MMP-9 Activity Improves Soleus Muscle Regeneration

“…25 Thus, the regeneration of crush-injured rat slow twitch Soleus muscle leads to the formation of a dysfunctional fibrotic muscle, characterized by the accumulation of ECM components, such as fibronectin. 24 Our previous study showed that MMP-9 and MMP-2 are significantly upregulated during crush-induced Soleus muscle regeneration. 8 Rise in MMP-9 activity was associated with both the myolysis and the reconstruction phases, whereas the activity of MMP-2 increased at the reconstruction phase.…”

“…1a) can be induced by crushing. [22][23][24] Histological analysis of such muscle proves that the myolysis phase is completed by day 3 after the injury (data not shown) and, by day 7, the reconstructed muscle contains the newly formed, heterogeneous in size, fibers ( Fig. 1b).…”

Mouse gastrocnemius muscle regeneration after mechanical or cardiotoxin injury

“…Crushing as a method of inducing regeneration was first described by Bassaglia and Gautron [11], and has since been used in many research studies by us www.fhc.viamedica.pl [17][18][19][20] and by others [11,16]. One of the important steps of this procedure is denervation, which not only ensures reproducibility of the process, but also makes the initial steps of regeneration less painful for the animal.…”

“…Moreover, differences in the process of regeneration may be caused not only by different methods of injury [13--15], but might also be associated with the type of regenerating muscle. Slow-twitch muscle regeneration has been shown to be impaired compared to fasttwitch muscle [19,20]. Furthermore, cells isolated from different muscles have been shown to express different myogenic potential [11,35].…”

“…Moreover, only a few papers have included a detailed, side by side, comparison of the muscle regeneration induced using different methods, and these publications do not cover all the molecular changes occurring within the muscles [13][14][15]. To fill this gap in knowledge, we aimed to carefully compare the dynamics of regeneration induced by two types of commonly used injury methods: crushing [11,[16][17][18][19][20] and CTX injection [7,[21][22][23][24][25][26]. Crushing, accompanied by denervation, causes muscle degeneration as a result of mechanical devastation of myofibers [11].…”