Comparative Analysis of the Fibroblastic Response and Collagen and Elastic Fiber Formation After Implantation of Polypropylene Versus an Electrospun Biodegradable Polymer for Reinforcement of the Musculo-Fascial Wall

The replacement of polypropylene with biodegradable polymers for surgical reinforcement of musculo-fascial structures is of considerable clinical interest. A study in 98 laboratory rats with implanted polypropylene or biodegradable biopolymer demonstrated the formation of dense irregular connective tissue at the surgical site instead of biopolymer and dense regular connective tissue around the polypropylene. The fibroblastic response to the biopolymer lagged behind that to polypropylene by approximately nine months, reflecting gradual polymer degradation, but did not differ between groups at 12 months, when the biopolymer had completely biotransformed. In both groups, newly formed connective tissue contained numerous elastic fibers and relatively fewer type I (COLI) and type III (COLIII) collagen fibers compared with intact preoperative tissue. In peri-implant tissue from both groups, COLIII fibers significantly predominated over COLI, with a higher volume fraction of COLIII around the polypropylene than around the biopolymer, whereas COLI was significantly more abundant in intact tissues. These findings are consistent with the good extensibility and low tear resistance of newly formed connective tissue. In the polypropylene group, polymer filaments reinforced this tissue mechanically. Further analysis of explanted tissues is required to determine the functional properties of connective tissue remodeled at the site of a degraded biopolymer implant.