Revascularization of Ischemic Skeletal Muscle by Estrogen-Related Receptor-γ

Abstract

Rationale Oxidative myofibers in the skeletal muscles express high levels of angiogenic factors, have dense vasculature, and promptly revascularize during ischemia. Estrogen-related receptor-gamma (ERRγ) activates genes that govern metabolic and vascular features typical to oxidative myofibers. Therefore, ERRγ-dependent remodeling of the myofibers may promote neoangiogenesis and restoration of blood perfusion in skeletal muscle ischemia. Objective To investigate the muscle fiber type remodeling by ERRγ and its role in the vascular recovery of ischemic muscle. Methods and Results Using immunohistology, we show that skeletal muscle-specific transgenic overexpression of ERRγ increases the proportions of oxidative and densely vascularized type IIA and IIX myofibers and decreases glycolytic and less vascularized type IIB myofibers. This myofiber remodeling results in a higher basal blood flow in the transgenic skeletal muscle. By applying unilateral hind limb ischemia to transgenic and wild-type mice, we found accelerated revascularization (fluorescent microangiography), restoration of blood perfusion (laser Doppler flowmetry), and muscle repair (Evans blue dye exclusion) in transgenic compared to wild-type ischemic muscles. This ameliorative effect is linked to enhanced neoangiogenesis (CD31 staining and microfil perfusion) by ERRγ. Using cultured muscle cells in which ERRγ is inactivated, we show that the receptor is dispensable for the classical hypoxic response of transcriptional upregulation and secretion of vascular endothelial growth factor A. Rather, the ameliorative effect of ERRγ is linked to the receptor-mediated increase in oxidative myofibers that inherently express and secrete high levels of angiogenic factors. Conclusions The ERRγ is a hypoxia-independent inducer of neoangiogenesis that can promote reparative revascularization.

Muscle Arnt/Hif1β Is Dispensable in Myofiber Type Determination, Vascularization and Insulin Sensitivity

“…Frozen muscle sections were processed for immunofluorescence staining of capillaries [using CD31/PECAM-1 antibody # RM5200 (Invitrogen)] and of myosin heavy chains (MyHC) type IIA, IIX and IIB [using, respectively, # SC-71, # BF-F3, and # 6H1 (Developmental Studies Hybridoma Bank)], as we previously described [19,20]. All primary antibodies were visualized using suitable Alexa Fluor® or Cy5 secondary antibodies from Molecular Probes.…”

Perm1 enhances mitochondrial biogenesis, oxidative capacity, and fatigue resistance in adult skeletal muscle

“…Furthermore, in many transgenic mouse models, an increase in muscle mitochondrial oxidative capacity is associated with a shift to a more oxidative muscle fibertype composition. For example, mice with musclespecific overexpression of PGC-1a, PGC-1b, PPARd, or ERRg have increases in type I, IIa, or IIx fibers, at the expense of IIb fibers (with each transgenic model showing distinct patterns of fiber-type composition) (20)(21)(22)(23)(24)63). Some of these mouse models also show decreases in fiber cross-sectional area, consistent with a switch to more oxidative fibers (21,23).…”

Estrogen-Related Receptor γ Plays a Key Role in Vascular Calcification Through the Upregulation of BMP2 Expression

“…A growing body of evidence suggests that ERRγ is relevant to vascular pathophysiology, including angiogenesis and restoration of blood perfusion in ischemic tissues. 21,22 Here, we provide another pathophysiological function for ERRγ in the process of vascular calcification. Because a previous study reported that ERRγ negatively regulates BMP2-induced osteoblast differentiation and bone formation, we initiated this study with the expectation that ERRγ would have beneficial effects on vascular calcification under calcificationprone conditions.…”