Immunohistochemical analysis of host reaction to heavyweight-, reduced-weight-, and expanded polytetrafluoroethylene (ePTFE)-based meshes after short- and long-term intraabdominal implantations

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Abstract
Prosthetic meshes induce a variety of inflammatory changes in the host, which may lead to excessive scarring with detrimental clinical consequences, especially in the long term. This study aimed to characterize the degree of short- and long-term inflammatory changes induced by common prosthetic meshes. Twenty 4 × 4-cm samples each of expanded polytetrafluoroethylene (ePTFE), heavyweight polypropylene (hPP), ePTFE/heavyweight polypropylene (ePTFE/hPP), and reduced-weight polypropylene/regenerated cellulose (rPP) were implanted intraperitoneally in 40 rabbits for 4 or 12 months. After explantation, samples of mesh/tissue complex were analyzed for the degrees of cellular apoptosis (enzyme-linked immunoassay [ELISA]) and cellular turnover (mouse monoclonal antibody). In the short term, the degree of apoptosis in the hPP mesh was significantly higher than in the ePTFE and rPP groups. Similarly, it was higher in the ePTFE/hPP group than in either the ePTFE or the rPP group. The amount of Ki-67-positive cells was significantly higher in the hPP group than in the ePTFE or rPP group. The cell turnover in the ePTFE/hPP group was similar to that in the hPP group, but significantly higher than in either the ePTFE or the rPP group. The rPP group, in turn, had a higher Ki-67 score than the ePTFE group. In the long term, both the degree of apoptosis and Ki-67 positivity were significantly lower in the rPP and ePTFE groups than in either the ePTFE/hPP or the hPP group. A significant decrease in Ki-67 scores between the short and long-term groups was found only in the rPP group. In the short term, heavyweight polypropylene-based meshes were associated with significantly higher cell proliferation and death. A significantly higher degree of apoptosis and cell turnover were associated with heavyweight polypropylene-based meshes even 1 year after implantation, indicating ongoing inflammation and scar remodeling. On the other hand, ePTFE and reduced-weight polypropylene meshes were associated with nearly physiologic levels of inflammatory markers. Overall, an exaggerated and persistent host foreign body response to heavyweight polypropylene-based meshes indicates poor biocompatibility, with potential detrimental clinical sequela.