Assessment of mesh shrinkage using fibroblast-populated collagen matrices: a proof of concept for in vitro hernia mesh testing

Abstract

Purpose: This study uses free-floating contractile fibroblast-populated collagen matrices (FPCMs) to test the shrinkage of different hernia mesh products. We hope to present this model as a proof of concept for the development of in vitro hernia mesh testing-a novel technology with interesting potential.

Methods: FPCMs were formed by seeding Human Dermal Fibroblasts into collagen gels. FPCMs were seeded with three different cell densities and cast at a volume of 500 μl into 24-well plates. Five different mesh products were embedded within the collagen constructs. Gels were left to float freely within culture media and contract over 5 days. Photographs were taken daily and the area of the collagen gel and mesh were measured. Media samples were taken at days 2 and 4 for the purposes of measuring MMP-9 release. After 5 days, dehydrated FPCMs were also examined under light and fluorescence microscopy to assess cell morphology.

Results: Two mesh products-the mosquito net and large pore lightweight mesh were found to shrink notably more than others. This pattern persisted across all three cell densities. There were no appreciable differences observed in MMP-9 release between products.

Conclusions: This study has successfully demonstrated that commercial mesh products can be successfully integrated into free-floating contractile FPCMs. Not only this, but FPCMs are capable of applying a contractile force upon those mesh products-eliciting different levels of contraction between mesh products. Such findings demonstrate this technique as a useful proof of concept for future development of in vitro hernia mesh testing.

Keywords: Hernia; In vitro; Materials; Mesh; Testing.

Fig. 1

Three photographic images taken of the macroporous mesh integrated within the high cell density FPCM (1.5 × 10⁶). Images A, B and C are taken at 24, 72 and 120 h (days 1, 3 and 5) of culture respectively. The reduction of size in both collagen and mesh can be clearly observed. Note also the visible increase in collagen density—especially at the periphery of the gels

Fig. 2

Three photographic images taken of the microporous mesh integrated within the high cell density FPCM (1.5 × 10⁶). Images A, B and C are taken at 24, 72 and 120 h (Days 1, 3 and 5) of culture respectively. The reduction of size in both collagen and mesh are less clearly observed than the macroporous mesh in Fig. 1

Fig. 3

Graphs showing the average percentage of collagen contraction over 120 h at three different cell densities. Hw = heavyweight, Lw = lightweight

Fig. 4

Graphs depicting the average percentage of mesh contraction over 120 h period at three different cell densities. Hw = heavyweight, Lw = lightweight

Fig. 5

Light microscopy images of 3 separate mesh products (PP medium pore, PP macroporous and mosquito net) within FPCMs after 5 days (120 h) of culture. Images are provided of both the central portion of the mesh (left sides images) and those on the edge of the mesh (right sided images). Images are taken with a 4× objective, scale bars 1550 µm

Fig. 6

Fluorescence microscopy images showing Cell distribution at different regions (edge, pore and mesh fibre regions) of the collagen constructs with different integrated meshes at the highest cell density (1.5 × 10⁶ cells/ml). a PP medium pore mesh. b PP macroporous mesh. c mosquito net. Right sided images are from the central mesh pores, whilst left sided images are from the edge of the mesh. White double headed arrows indicate cellular alignment. Image objective is 20×, and scale bars are 200 µm