PS190. Ischemia Mediates Myogenic Progenitor Cell Dysfunction

Abstract

42 days. Specimens were collected at days 1, 3,7,21,42, and 90. IH and SMCp were measured at the fistula site as well as in the artery and vein proximal and distal to the fistula.Results: IH was first noted at day 3 and significantly increased through day 90 at all locations in the nonoxygen supplemented groups. There was no significant IH noted in the O 2 supplemented groups at any location or any time point Table). SMCp was noted at Day 3 through Day 21 in the non-oxygen supplemented group while almost no SMCp was noted in the O 2 supplemented groups at any location or timepoint.Conclusions: Without O 2 supplementation SMCp begins at day 3 and is no longer noted at day 21 after creation of an AVF while IH begins by day 3 and increases at least through day 90 after creation of an AVF. 42 days of 30% supplemental O 2 inhibits both IH and SCMp after creation of an AVF. This data suggests a role for short-term administration of low-dose O 2 to prevent both IH and SMCp after creation of an AVF prolonging fistula patency and function.Objectives: Treatment options for critical limb ischemia (CLI) are limited. Recent evidence has suggested that even with successful revascularisation, patients often show little functional improvement. This has been attributed to a musculopathy that occurs in CLI. Myogenic progenitor satellite cells (SCs) provide skeletal muscle with an intrinsic ability to regenerate. It has been shown that there is an increase in SCs in ischemic muscle, however their function in ischemia is poorly understood and we hypothesize that ischemia has a detrimental effect on SC function.Methods: Gastrocnemius muscle biopsies were taken from CLI patients and compared with non ischemic control biopsies. The phenotypical changes and frequency of satellite cells were investigated using PAX 7 immunohistochemistry and western blot. C2C12 myoblasts were used in vitro, to investigate the effect of ischemia on muscle progenitor cell function. Myoblasts were exposed to simulated ischemia for 24, 48 and 72hrs. Proliferation rates were assessed using an MTT assay. Differentiation and apoptosis were assessed by MYOD and cleaved caspase 3 western blotting respectively.Results: There is an increased expression of PAX 7 in CLI muscle biopsies, shown by both immunostaining and western blot analysis, suggesting an increased number of SCs in ischemic human skeletal muscle (P Ͻ.05). Myoblasts cultured in ischemic conditions demonstrated decreased cell proliferation, reduced myogenic differentiation (decreased MYOD expression), and increased apoptosis (increased cleaved caspase 3 expression).Conclusions: Despite an upregulation of SCs in ischemic tissue, their function is suppressed in ischemic conditions and this may be contributing to the poor functional recovery of patients post revascularisation. Enhancement of muscle regeneration in ischemia may be a useful therapeutic adjunct in the treatment of CLI.Objectives: MicroRNAs (miRs) are a class of recently discovered noncoding endogenous, small RNAs that negatively regulate gen...