Bladder reconstruction using a collagen patch prefabricated within the omentum

Abstract

Objective: We present our experience with a novel bladder reconstruction model using a collagen sponge pre-embedded within the omentum. The aim of the study is to evaluate tissue regeneration of the reconstructed bladder and the effect of prefabricating the collagen patch within the omentum. Materials and methods: Twenty pigs were divided into three groups. For the prefabricated patch group (PFP; n = 10), collagen sponge was inserted into the omentum. After 1 week, the pigs underwent a hemicystectomy and the sponge with an attached omental flap was brought to close the defect. For the non-prefabricated patch group (NPFP; n = 6), pigs received hemicystectomy and closure with a collagen sponge without prefabricating in the omentum. Four other pigs received hemicystectomy alone as a control (C; n = 4). All animals in the NPFP and C groups, and 7 of 10 in the PFP group were sacrificed at 4 or 8 weeks. Three other pigs in the PFP group were sacrificed at 12 weeks. Resected bladders were submitted to hematoxylin-eosin, and immunohistochemical staining. Results: All animals except for two in the NPFP group survived. At the time of grafting, the collagen sponge was covered with thick omental methothelial layers, and neo-vascularization from the omentum was observed. At each time point, only slight adhesion was observed around the patch in the PFP group, while severe adhesion between the patch and the bowel was observed in the NPFP group, suggesting that prefabricated collagen sponge within the omentum prevented urine leakage from the bladder. Histologically, the patch was well vascularized, and the luminal surface was covered with urothelium at 4 weeks in both groups. However, in the PFP group, there was mild inflammation in the submucosa and in-growth of smooth muscle derived from the adjacent muscle layers was observed with time, whereas severe inflammation was observed and in-growth of smooth muscle was limited in the NPF group. Conclusions: Prefabricating of a collagen patch within the omentum stimulated early neo-vascularization before grafting, and this procedure appears to offer an advantage for bladder reconstruction over a non-prefabricated procedure in terms of prevention of urine leakage and inflammation, and favorable tissue regeneration.

Changing concepts of bladder regeneration

“…Although regeneration of smooth muscle-like tissue is usually observed in BAM, SIS, or other collagen-derived materials, their morphology and function is not completely equivalent to a native bladder detrusor. 15,26,36 The origin of regenerated smooth muscle may be de-differentiated smooth muscle cells from adjacent bladder parenchyma, while a minor contribution of bone marrow cells was also reported by our group. 19,37 Initially, urothelial cells were believed to promote muscle regeneration via epithelialmesenchymal interaction, 19 but a study by our group demonstrated that the growth factor milieu created by urothelium, with higher levels of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF), had a negative effect on muscle maturation.…”

Prevascularization of cardiac patch on the omentum improves its therapeutic outcome

“…Others have successfully exploited the omentum for the vascularization of hepatic tissues and for bladder construction (30,31). Recently, our group transplanted cardiac cell-seeded scaffolds into the peritoneal cavity in an attempt to induce tissue engineering of the patch (32).…”

One-Stage Tissue Engineering of Bladder Wall Patches for an Easy-To-Use Approach at the Surgical Table

“…[1][2]16 Among the natural polymers, collagen has been widely used for bladder tissue engineering applications because of its favorable cell-matrix interactions. [16][17][18][19] However, conventional collagen-based scaffolds in the form of hydrogels that allow rapid introduction of cells or tissues suffer from low mechanical strength and are not conducive to surgical handling. To overcome this limitation, the technique of plastic compression of collagen hydrogels was introduced by Brown et al 20 While this approach improves the mechanical properties, it does not provide sufficient strength for bladder engineering.…”