Kinetics of implant-induced inflammatory angiogenesis in abdominal muscle wall in mice

Abstract

Injury of skeletal abdominal muscle wall is a common medical condition and implantation of synthetic or biological material is a procedure to repair musculofascial defects. We proposed to characterize the dynamics of inflammatory cell recruitment, newly formed blood vessels, cytokine production and fibrogenesis in the abdominal skeletal muscle in response to polyether-polyurethane sponge implants in mice. At 2, 4, 7 and 10days after implantation the muscle tissue underneath the sponge matrix was removed for the assessment of the angiogenic response (hemoglobin content, vascular endothelial growth factor and morphometric analysis of the number of vessels) and inflammation (myeloperoxidase and n-acethyl-B-d-glucosaminidase activities, cytokines). In addition, muscle fibrogenesis was determined by the levels of TGF-β1 and collagen deposition. Hemoglobin content, wash out rate of sodium fluorescein (indicative of blood flow) and the number of vessels increased in the abdominal muscle bearing the synthetic matrix in comparison with the intact muscle. Neutrophil recruitment peaked in the muscle at day 2, followed by macrophage accumulation at day 4 post-injury. The levels of the cytokines, VEGF, TNF-α, CCL-2/MCP-1 were higher in the injured muscle compared with the intact muscle and peaked soon after muscle injury (days 2 to 4). Collagen levels were higher in sponge-bearing muscle compared with the non-bearing tissue soon after injury (day 2). The implantation technique together with the inflammatory and vascular parameters used in this study revealed inflammatory, angiogenic and fibrogenic events and mechanisms associated with skeletal muscle responses to synthetic implanted materials.

PLGA nanofibers improves the antitumoral effect of daunorubicin

“…The extent of the vascularization of the sponge was assessed in terms of the amount of Hb that was detected in the tissue using the aforementioned Drabkin method [27][28][29][30]. The Hb concentration in the samples was determined spectrophotometrically by measuring the absorbance at 540 nm.…”

“…The Hb content in the implant was expressed as g Hb per mg wet weight. The cytokine VEGF was measured following the protocol described in previously published studies [28,30]. The neutrophils in the sponge were measured by assaying the MPO activity, as has been described in the literature [27][28][29][30].…”

“…The results were expressed as the change in OD/mg wet weight. The infiltration of mononuclear cells into the sponge was quantified by monitoring the levels of the lysosomal enzyme NAG, which was present in high levels in the activated macrophages, by measuring the absorption at 400 nm [27][28][29][30].…”

“…The inflammatory component of the fibrovascular tissue was assessed using several measures that are widely accepted as inflammation markers, such as MPO and NAG activities for the assessment of neutrophil or macrophage recruitment/activation, respectively [27,30,53,54]. Fig.…”

Angiopreventive versus angiopromoting effects of allopurinol in the murine sponge model

“…In this model, the acellular and avascular synthetic matrix implanted subcutaneously in the dorsal of the animals induces the migration, proliferation and activation of various cells types responsible for the development of a fibrovascular tissue that underlies both acute and chronic pathological conditions (Almeida et al, 2014;Castro et al, 2012Castro et al, , 2014Marques et al, 2011). We report here that allopurinol exhibited both angiopreventive and angiopromoting effects on the fibrovascular tissue induced by synthetic matrix in mice.…”