Abstract 12527: Impaired Angiogenesis During Hindlimb Ischemia in Skeletal Muscle-Specific STAT3 Deficient Mice
Background: Although the STAT3 activating cytokines such as leukemia inhibitory factor (LIF) and interleukin-11 (IL-11) play an important role in angiogenesis, little is known about the signaling mechanism in skeletal muscle during ischemia-induced angiogenesis. We investigated whether the STAT3 signaling pathway in the skeletal muscle might play a role in angiogenesis during hindlimb ischemia (HLI).
Methods and Results: We conducted western blot and real-time PCR to examine the activation of STAT3 and inductions of STAT3-activating cytokines in the adductor muscle from ischemic limbs of wild-type mice (WT). Western blot revealed that STAT3 was promptly phosphorylated, and this was sustained up to 7 days after HLI in WT mice. Real-time PCR showed up-regulation of STAT3-activating cytokine expression after 12 h of HLI compared to sham operated controls. The up-regulated cytokines included leukemia inhibitory factor (58.7 fold), interleukin-10 (IL-10; 7.4 fold), IL-11 (4.3 fold), and G-CSF (22.8 fold). To investigate the role of skeletal muscle STAT3 signaling in angiogenesis during HLI, we generated skeletal muscle-specific, STAT3 knockout mice (sm-STAT3-KO). We used serial laser Doppler blood-flow (LDBF) analysis to determine the ischemic to normal LDBF ratio. The LDBF ratio showed the impaired recovery in sm-STAT3-KO mice 14 days after HLI (p<0.01). We conducted immunohistochemical staining of CD31 to evaluate capillary formation. The number of CD31 positive cells 14 days after induction of HLI was significantly less in sm-STAT3-KO than that in WT (p<0.05). To investigate the mechanism that gave rise to impaired angiogenesis during HLI in sm-STAT3-KO, we conducted a real-time PCR array analysis for angiogenesis. The expression of chemokine (C-X-C motif) ligands (CXCL) that have angiogenic property was markedly up-regulated after HLI compared to sham operated controls (CXCL1: 77.8 fold, CXCL2: 133.4 fold, CXCL5: 39.5 fold). Interestingly, CXCL expression levels were significantly lower in sm-STAT3-KO than those in WT after HLI (CXCL1; 0.06 fold, CXCL2; 0.05 fold, CXCL5; 0.09 fold).
Conclusion: These results suggested that angiogenesis during HLI was impaired in sm-STAT3-KO, possibly through the inhibition of CXCL chemokine expression.
- © 2011 by American Heart Association, Inc.