Role of PAX-7 as a tissue marker in mangled extremity: a pilot study.

The rising incidence of mangled extremity seen in modern trauma has lead to significant patient mortality. A lot of research is going on at microcellular level for a better understanding of tissue injury, repair and regeneration. PAX-7 is one such transcription factor, a marker of satellite stem cells in skeletal muscle. Though few studies have shown concrete evidence of increased expression of PAX-7 in the nearby injured zone in skeletal muscle post-injury, none has studied its expression in an event of mangled injury of limb in humans. We, hereby, attempted to identify whether PAX-7 expression of tissue near the zone of injury, after grievous trauma like mangled injury of extremities, actually increases, decreases or remains unaffected. A pilot study was conducted on 30 cases at a level 3 trauma centre; patients were segregated into two groups-group I with MESS score ≥ 7 and group II with score < 7. For group I patients, amputation was planned, and for group II, limb salvage surgery was planned. Skeletal muscle samples from three different zones (A, B and C) in group I, while pre- and post-debridement skeletal muscle samples in group II were sent for microscopic examination and IHC staining with PAX-7 antibody. A definite increase in PAX-7 expression, post-trauma near the zone of injury (Zone B and C in group I and post-debridement in group II), was noted. Increased expression of PAX-7 signifies increased recruitment of satellite stem cells near the injury zone, thereby reflecting the activation of skeletal muscle regeneration cascade. Hence, increased staining of PAX-7 in tissues could be a viable marker for identifying potential regeneration of skeletal muscle post-injury.