Production of consistent crush lesions in murine quadriceps muscle—A biomechanical, histomorphological and immunohistochemical study

Abstract

Poor healing of high-energy fractures is often associated with severe muscle damage. This mdy be partly due to the production, by the injured muscle, of inflammatory cytokines that somehow misdirect bone healing. In order to investigate this question, an animal model was established which embodies a controlled degree of muscle injury with a dose response to the energy absorbed, that can be characterised histologically. Using a custom crush jig, 60 CFLP mice had either 100 or 200 g masses dropped from a fixed height onto the quadriceps muscle, with mechanical measurement of the impact. Energy of impact was reliably and significantly different between the small and large impact conditions, though there was more variability when the large mass was used. Animals were sacrificed at day 2,4, 8, 16, and 24 post-injury. Muscle histomorphometry at all time points and immunohistochemistry for ILlp, IL-6, and TNF-a up to day 8 were used as measures of muscle damage, inflammation and repair. Histological sections were analysed into areas of normal muscle fibres, damagedhegenerating muscle fibres and fibrous/inflammatory infiltrate. Early histological response was similar between the two groups; the large crush group displayed significantly greater areas of inflammatory infiltrate and damaged muscle at the later time points after day 8. In the large crush group, IL-lP and IL-6 expression were significantly higher at day 2 and TNF-a was higher at day 8 when compared to the small crush group.The experiment demonstrated that more severe injury to muscle was reliably followed by increased inflammatory cytokine production and a greater degree of inflammation and fibrosis. Increased production of inflammatory cytokines such as TNF-a and I t -l p in the damaged muscles may activate macrophages and recruit fibroblasts, promote scar formation and lead to delayed union or non-union of the adjacent fracture(s).

Degeneration/Regeneration as a Mechanism Contributing to the Effect of Manual Acupuncture-Induced Injury on Rat Skeletal Muscle

“…Although IL-6 is classified as a pro-inflammatory cytokine it has a variety of biological functions. IL-6 can also act as in anti-inflammatory manner to inhibit the inflammatory response (Bunn et al, 2004;Xing et al, 1998). The expression of IL-6 mRNA was detected in different injury models of muscle regeneration Sheriff et al, 2009;Warren et al, 2002).…”

“…The expression of IL-6 mRNA was detected in different injury models of muscle regeneration Sheriff et al, 2009;Warren et al, 2002). For example, Bunn et al (2004) investigated the increase of IL-6 during regeneration following crush injury in rat muscle at different time points: 2, 4, 8, 16, and 24 days. The results showed a high level increase on day 2 post injury, decrease on day 4 and then increase again on day 8.…”

Time course of skeletal muscle regeneration after severe trauma

“…Among them, open crush injuries allow standardized evaluation of regeneration in a selected muscle (Schultz et al 1985, Rushton et al 1997). For the execution of the trauma, either forceps (McGeachie and Grounds 1987, Kurek et al 1997, Fink et al 2003) or custom-made devices have been used (Jarvinen and Sorvari 1975, Rushton et al 1997, Bunn et al 2004). …”

“…Histological analysis of the regenerative process after crush injury has been done by a number of authors, describing the initial phase of inflammation followed by satellite cell activation, myotube regeneration, and fibrosis of the muscle (Jarvinen and Sorvari 1975, Schmalbruch 1976, Sorokin et al 2000, Bunn et al 2004). It has been shown that the development of fibrotic tissue is one of the key factors for regenerative deficits of muscle function after trauma (Anderson et al 1999, Nozaki et al 2008).…”

A Comparison of Surgical Invasions for Spinal Nerve Ligation with or without Paraspinal Muscle Removal in a Rat Neuropathic Pain Model

“…Furthermore, changes in cytokine levels are dependent on the degree of injury. An experimental study demonstrated that more severe injury to muscles produced increased cytokine production and a greater degree of inflammation [27]. Clinical studies usually measure the changes of the cytokine levels to evaluate the surgical invasions [28, 29].…”