Background: The role of adrenoceptors in granulation tissue formation is not well understood. The aim of this study was to investigate the effects of alpha- and beta-adrenoceptor blockade on granulation tissue development using polyurethane (PU) implants in the rat.
Methods: Animals were treated orally with propranolol (beta1- and beta2-antagonist), atenolol (beta1-antagonist) or phentolamine (alpha1- and alpha2-antagonist) until euthanasia. The control group received only water. All animals received subcutaneous implants of PU sponges. After 14 days, implants were collected, formalin-fixed and paraffin-embedded. Sections were stained with hematoxylin and eosin and Sirius red and immunostained for CD68 and alpha-smooth muscle actin.
Results: The number of inflammatory cells and the volume density of myofibroblasts and blood vessels were lower in the control group than in the propranolol- and atenolol-treated groups. The collagen fiber score was greater in the control group than in the propranolol- and atenolol-treated groups. The inflammatory infiltrate, collagen fiber score, blood vessel density or myofibroblast differentiation was not affected by phentolamine. The percentage of fibrovascular invasion was greater in the antagonist-treated groups than in the control group.
Conclusions: Blockade of beta1- and beta2-adrenoceptors, but not alpha-adrenoceptors, impairs granulation tissue development in PU implants due to interference with the inflammatory response.