Reduction of inflammatory response in composite flap transfer by local stress conditioning-induced heat-shock protein 32

Background. The failure of composite flaps despite anastomotic patency is t hought to be mediated by the inflammatory response within the microvasculat ure, which results from unavoidable surgical trauma and transfer-related is chemia-reperfusion. Evidence suggests that stress conditioning may improve flap survival; however; the molecular mechanisms of protection are far from being clear. Therefore, we analyzed whether stress conditioning-induced he at-shock protein 32 is effective to prevent the inflammatory response in tr ans osteomyocutaneous flaps. Methods. In a rat model, leukocyte-endothelial cell interaction and endothe lial integrity disruption as early indicators of the inflammatory response were quantitatively analyzed in muscle, subcuticular tissue, and periosteum of microvascularly transferred osteomyocutaneous flaps by using intravital fluorescence microscopy. Twenty-four hours before flap transfer; stress co nditioning was induced by local heating of the left hindlimb up to 42.5 deg reesC for 30 minutes. In additional animals, stress conditioning-induced ac tivity of heat-shock protein 32 was inhibited by tin protoporphyrin-IX. Unc onditioned flaps served as controls. Results. In all tissues analyzed, control flaps showed significant leukocyt e adherence in postcapillary venules, increased intercellular adhesion mole cule-1 (ICAM-1) expression, and endothelial integrity disruption, but a lac k of heat-shock protein 32. In contrast, stress conditioning induced marked heat-shock protein 32 expression, which was associated with a significant reduction (P < .05) of leukocyte adherence ICAM-1 expression, and endotheli al hyperpermeability. The inhibition of heat-shock protein 32 by protoporph yhrin-IX completely abolished the stress conditioning-induced amelioration of the inflammatory response in all tissues analyzed. Conclusions. Stress conditioning by local heat-shock priming reduces the in flammatory response in osteomyocutaneous flaps. The protective effect is me diated by the induction of heat-shock protein 32.