Repair of abdominal wall defects with biodegradable laminar prostheses: polymeric or biological?

Abstract

Introduction: Biological and synthetic laminar absorbable prostheses are available for the repair of hernia defects in the abdominal wall. They share the important feature of being gradually degraded in the host, resulting in place the formation of a neotissue. This study was designed to assess the host tissue's incorporation of collagen bioprostheses and a synthetic absorbable prosthesis.

Methods: Partial defects were created in the abdominal walls of 72 New Zealand rabbits and repaired using collagen bioprostheses Tutomesh® and Strattice® or a synthetic prosthesis Bio-A®. Specimens were collected for light microscopy, collagens gene and protein expression, macrophage response and biomechanical resistance at 14, 30, 90 and 180 days post-implantation.

Results: Tutomesh® and Bio-A® were gradually infiltrated by the host tissue and almost completely degraded by 180 days post-implantation. In contrast, Strattice® exhibited material encapsulation, no prosthetic degradation and low cell infiltration at earlier timepoints, whereas at later study time, collagen deposition could be observed within the mesh. In the short term, Bio-A® exhibited higher level of collagen 1 and 3 mRNA expression compared with the two other biological prostheses, which exhibited two peaks of higher expression at 14 and 90 days. The expression of collagen III was homogeneous throughout the study and collagen I deposition was more evident in Strattice®. Macrophage response decreased over time in biomeshes. However, in the synthetic mesh remained high and homogeneous until 90 days. The biomechanical analysis demonstrated the progressively increasing tensile strength of all biomaterials.

Conclusions: The tissue infiltration of laminar absorbable prostheses is affected by the structure and composition of the mesh. The synthetic prosthesis exhibited a distinct pattern of tissue incorporation and a greater macrophage response than did the biological prostheses. Of all of the laminar, absorbable biomaterials that were tested in this study, Strattice® demonstrated the optimal levels of integration and degradation.

Figure 1. Used biomaterials.

Scanning electron microscopy images (100×) showing the aspect and the thickness of Bio-A (A), Tuto (B) and St (C). Polarized light images, with collagen fibers displayed in red after Sirius Red staining (200×). Bio-A (D), Tuto (E) and St (F).

Figure 2. Macroscopic biomaterial images.

Bio-A implants after 14 days (A) and 30 days postimplantion (D). Tuto, 14 days (B) and 30 days (E). St, 14 days (C) and 30 days (F). Partial degradation of Tuto at 14 (G) and 30 days (H). St encapsulation (arrow) at 30 days post-implantation (I).

Figure 3. Light microscopy images.

Tissue integration and prostheses degradation in the different timepoints (100×). Bio-A (A–D) and Tuto (E–H) showed a gradual infiltration of host tissue and was completely degraded by 180 days post-implantation. St exhibited material encapsulation, without signs of degradation and low cell infiltration at 180 days (I–L). (– Prosthesis).

Figure 4. Collagen 1 and 3 mRNA expression determined by RT-PCR.

Agarose gel product and relative mRNA quantity of Bio-A (A), Tuto (B) and St (C) after 14, 30, 90 and 180 days post-implantation. The results are expressed as the mean ± SEM of three experiments. Gene expression was normalized with the GAPDH gene. A) Bio-A: Collagen (Col) 1: *, vs. 90 days (P<0.05) and 180 days (P<0.01); #, vs. 90 days (P<0.05) and 180 days (P<0.01); τ, vs. Tuto (P<0.05) and St (P<0.01) at 30 days. Col 3: |, vs. 30 days and 90 days (P<0.05) and 180 days (P<0.001); †, vs. 90 days (P<0.05) and 180 days (P<0.001); ξ, vs. Tuto (P<0.05) and St (P<0.01) at 30 days. B) Tuto: Col 1: ‡, vs. 30 days (P<0.05). Col 3: §, vs. 14 and 90 days (P<0.05). C) St: Col 1: ƒ, vs. Bio-A and Tuto at 14 days (P<0.01). (N = negative control; Mw = molecular weight markers).

Figure 5. Immunodetection of neoformed collagen I and III in Bio-A®.

Mature Collagen I (A–H) and immature Collagen III (I–P) immunofluorescence at 14, 30, 90 and 180 days post-implantation. The neoformed collagen appears in red and the cell nuclei (stained with DAPI) appear in blue. The DIC images that identify the biomaterial appear translucent (E–H and M–P). Confocal light microscopy (200×). (* Synthetic mesh).

Figure 6. Immunodetection of neoformed collagen I and III in Tutomesh®.

Mature Collagen I (A–H) and immature Collagen III (I–P) immunofluorescence at 14, 30, 90 and 180 days post-implantation. The neoformed collagen appears in red and the cell nuclei (stained with DAPI) appear in blue. The DIC images that identify the biomaterial appear translucent (E–H and M–P). Confocal light microscopy (200×). (* Biomesh).

Figure 7. Immunodetection of the neoformed collagen I and III in Strattice®.

Mature Collagen I (A–H) and immature Collagen III (I–P) immunofluorescence at 14, 30, 90 and 180 days post-implantation. The neoformed collagen appears in red and the cell nuclei (stained with DAPI) appear in blue. The DIC images that identify the biomaterial appear translucent (E–H and M–P). Confocal light microscopy (200×). (* Biomesh).

Figure 8. Foreign-body reaction of the different meshes.

Immunohistochemical labeling of rabbit macrophages (red color, arrows) using the RAM-11 monoclonal antibody (200×) (top panel): Bio-A (A–D), Tuto (E-H) and St (I–L). Percentage of positive cells for the RAM-11 antibody in the different prostheses after 14, 30, 90 and 180 days post-implantation (bottom panel). The results were expressed as the mean ± SEM. A) Bio-A: *, vs. 14 days and 90 days (P<0.001) and 30 days (P<0.01); #, vs. St (P<0.001) at 14 days; τ, vs. Tuto and St (P<0.01) at 30 days; |, vs. Tuto and St (P<0.001) at 90 days; †, Tuto and St (P<0.001) at 180 days post-implantion. B) Tuto: ξ, vs. 30 days (P<0.05) and 90 days (P<0.001); ‡, vs. 14 days and 30 days (P<0.001) and 90 days (P<0.01). C) St: §, vs. 90 days (P<0.001); ƒ, vs. 14, 30 and 90 days (P<0.001); φ, vs. Tuto (P<0.01) at 14 days; ξ, vs. Tuto (P<0.05) at 90 days; υ, vs. Tuto (P<0.001) at 180 days post-implantation.

Figure 9. Biomechanical strength of the different meshes.

The results (Newtons) were expressed as the mean ± SEM at 14, 30, 90 and 180 days post-implantation. Bio-A: *, vs. 14 days and 30 days (P<0.01). Tuto: #, vs. 90 days (P<0.01); τ, vs. 14 days and 90 days (P<0.05) and 30 days (P<0.01). St: |, vs. 14 days and 30 days (P<0.05).