Early tissue incorporation and collagen deposition in lightweight polypropylene meshes: bioassay in an experimental model of ventral hernia.

BACKGROUND: This study was designed to assess the early host tissue incorporation of several polypropylene lightweight (PP-LW) meshes used to repair abdominal wall defects and to correlate collagen deposition with the biomechanical response shown by PP-LW versus polypropylene heavyweight (PP-HW) meshes.
METHODS: Ventral hernial defects (7 x 5 cm) were created in the anterior abdominal wall of New Zealand rabbits and repaired by fixing PP-LW mesh of different pore sizes or a low porosity HW mesh to the edges of the defect. Rabbits were killed 14 days after implant, and specimens were taken from the central mesh area to examine collagen deposition by light microscopy, real time reverse transcription polymerase chain reaction, immunohistochemistry, and Western blotting. The biomechanical resistance of the biomaterials was also assessed.
RESULTS: All the materials showed excellent incorporation in host tissue. Relative amounts of collagen III mRNA were considerably higher than collagen I mRNA. Higher collagen I and III mRNA levels were noted for pore sizes equal to or greater than 3.45 +/- 0.19 mm(2) (Ultrapro/Optilene Elastic. These two meshes showed significantly higher levels of collagen III than Parietene and Surgipro with smaller pores. Biomechanical resistance values for Optilene were significantly higher than those recorded for Surgipro and Parietene.
CONCLUSIONS: (a) LW meshes of pore size larger than 3 mm(2) induced the genetic overexpression of collagen types I and III; (b) the larger pore-sized LW meshes induced more collagen type III deposition and its faster conversion to collagen I; (c) Optilene, the most porous LW mesh examined, showed the greatest tensile strength 14 days after implant.