Page 280 - Prevention and Treatment of Incisional Hernia- New Techniques and Materials

Chapter 13
results of negative microbiological cultures of the biomaterial 28 days after implantation(15). This means that the extended in ammatory reaction is not caused by the presence of bacteria. The macrophages surrounding the PP mesh displayed mainly an M2 phenotype, which is associated with tissue repair and angiogenesis, thus indicating a remodelling phase of wound healing(10). In earlier in vivo rat studies, mono lament PP biomaterial evoked an anti- in ammatory/ brotic reaction with formation of brotic tissue around the mesh bres, a low infection rate, and good incorporation into the abdominal wall, in both a contaminated(15, 18).
For the in vitro analysis, the M1/M2 index was calculated to summarize the e ects of a biomaterial on macrophages. However, it should be appreciated that dividing macrophages into either M1 or M2 phenotypes is a simpli cation, as several intermediate states exist28. In the in vitro in ammatory environment, macrophages on the multi lament PP biomaterial induced the expression of anti-in ammatory proteins at a higher rate than the other biomaterials tested, thus resulting in a low M1/M2 index. The low M1/M2 index in the case of PP is caused mainly by a high protein production of CCL18, which is known for its association with brosis23.
Macrophages on the COL biomaterial produced a relatively low amount of proin ammatory and anti-in ammatory cytokines, indicative of a mild reaction to the biomaterial. A mild foreign body reaction against collagen- based biomaterial has also been observed in vivo by others(11, 12, 14, 19).
Macrophages on the PET biomaterial had a relatively high M1/M2 index in the in vitro model, indicating a predominantly proin ammatory reaction of macrophages. PET and PP biomaterials are knitted according to similar weaves, resulting in comparable surfaces ( gure 1). The di erence in vitro is thus mainly in the contact angle/hydrophobicity, and therefore the proin ammatory reaction; thus the high M1/M2 index can be caused partly by the polymer type itself.
The PET+COL composite biomaterial tested is the mesh type generally preferred for intraperitoneal hernia surgery, as it minimizes the formation of postoperative tissue adhesions(20, 21). A high M1/M2 index was found for PET+COL biomaterial, indicating a high proin ammatory reaction in an in ammatory environment. In fact, this material evoked the highest absolute production of proin ammatory cytokines. This acute reaction can be explained by phagocytic activity of macrophages, trying to break down and digest
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