Results
None of the animals died during the investigation and none of the animals developed any signs of local or general inflammation.
MMP-2 protein Expression
Apart from the PVDF + PAAc group, MMP-2 expression significantly decreased for all other mesh groups comparing day 7 to day 21 (PVDF: p = 0.016; 2 μg/mg: p = 0.016; 5 μg/mg: p = 0.016; 8 μg/mg: p = 0.029). In the later course of time the MMP-2 expression was significantly reduced only for the 5 and 8 μg/mg group comparing day 21 to day 90 (5 μg/mg: p = 0.016; 8 μg/mg: p = 0.029) (Figure 1 and 2A).
(Enlarge Image)
Figure 1.
Histogram illustrating the percentage of MMP-2 positive stained cells detected in the perifilamentary area in each mesh group (represented as mean ± standard deviation, significant differences are marked (*)).
(Enlarge Image)
Figure 2.
Immunohistochemical images representing MMP-2 staining following implantation of a PVDF mesh (A) and a PVDF+PAAc+8 μg/mg mesh (C). Figure (B) demonstrates ß-galactosidase staining following implantation of a PVDF mesh and a PVDF+PAAc+8 μg/mg mesh (D) (magnification 200 fold, 90 days postoperatively respectively).
Both the 5 and 8 μg/mg mesh material showed significantly reduced levels of MMP-2 positive stained cells when compared to the pure PVDF group on day 7, 21 and 90 (5 μg/mg: p = 0.016, p = 0.016, p = 0.016; 8 μg/mg: p = 0.029, p = 0.016, p = 0.029). Except for day 7 the 2 μg/mg group likewise showed a significant reduction of MMP-2 protein expression compared to the pure PVDF group on day 21 (p = 0.016) and 90 (p = 0.032) (Figure 1 and 2A).
MMP-2 Promoter Activity (ß-galactosidase)
To detect the perifilamentary MMP-2 promoter activity we analyzed the ß-galactosidase expression (Figure 2B). In contrast to the MMP-2 expression MMP-2 promoter activity was reciprocal and increased discrete over time for all mesh modifications. Certainly a significant increase of ß-galactosidase expression could be detected only for the 5 μg/mg group from day 7 to day 21 (5 μg/mg: p = 0.026). The enhancement of the MMP-2 promoter activity was significant for the PVDF (p = 0.016), 2 μg/mg (p = 0.008) and 8 μg/mg (p = 0.029) group comparing day 21 and day 90 (Figure 2B and 3).
(Enlarge Image)
Figure 3.
Histogram representing the perifilamentary ß-galactosidase expression in each mesh group (represented as mean ± standard deviation, significant differences are marked (*)).
On postoperative day 90 a significant reduction of ß-galactosidase stained cells was observed for all gentamicin supplemented mesh groups in comparison to the pure PVDF group (2 μg/mg: p = 0.016; 5 μg/mg: p = 0.016; 8 μg/mg: p = 0.029). On day 21 the MMP-2 promoter activity showed any significant differences comparing the groups. Only the 8 μg/mg group revealed a significant reduced expression of ß-galactosidase on day 7 compared to the pure PVDF group (p = 0.029) (Figure 2B and 3).
Collagen Type I/III Ratio
The collagen type I/III ratio was investigated to evaluate the quality of perifilamentary collagen deposition. This ratio ascended in each mesh group in the course of time. Comparing day 7 to day 21, the collagen type I/III ratio increased significantly in each mesh group except for the PVDF + PAAc group (PVDF: p = 0.016; 2 μg/mg: p = 0.016; 5 μg/mg: p = 0.016; 8 μg/mg: p = 0.029). A significantly increased collagen type I/III ratio was detected comparing day 21 to day 90 for each mesh group apart from the PVDF group (PVDF + PAAc: p = 0.036; 2 μg/mg: p = 0.008; 5 μg/mg: p = 0.016; 8 μg/mg: p = 0.029) (Figure 4).
(Enlarge Image)
Figure 4.
Histogram demonstrating the perifilamentary collagen type I/III ratio in each mesh group (represented as mean ± standard deviation, significant differences are marked (*)).
Only the 8 μg/mg group showed significantly elevated values 7, 21 and 90 days after implantation when compared to the pure PVDF group (p = 0.029, p = 0.016, p = 0.029). The 2 μg/mg group as well as the 5 μg/mg group exhibited a significantly improved collagen type I/III ratio in comparison with the PVDF group only on day 90 (p = 0.016 and p = 0.016). Additionally the collagen type I/III ratio was significantly elevated in the 2 μg/mg group (p = 0.029) on day 7, and in the PVDF + PAAc group (p = 0.036) on day 21 compared to the PVDF group, respectively (Figure 4).