Bladder Augmentation Using Lyoplant®: First Experimental Results in Rats

Abstract

Background: Congenital defects of the urinary bladder (micro- or contracted bladder, bladder exstrophy) remain a challenging problem for pediatric surgeons. Even when conservative treatment options are fully exhausted, irreversible renal dysfunction can be observed in a large number of cases that can even lead to chronic renal failure and the need for kidney transplantation. To protect kidney function bladder augmentation using intestinal tissue is commonly applied as the standard treatment method. However due to the unphysiological nature of intestinal tissue a number of problems and complications such as urinary tract infections or bladder stone formation limit the clinical success of this approach. Moreover a number of substitutes for the implementation of a bladder augmentation have been tested without success to date. Here we used an experimental model to test wether the biocompatible collagen mesh Lyoplant may be a suitable candidate for bladder augmentation.

Methods: We implanted a biocompatible collagen mesh (Lyoplant^®) in a bladder defect rat model for bladder augmentation (Lyoplant^®-group: n = 12; sham group n = 4). After 6 weeks the abdomen was reopened and the initial implant as well as the bladder were resected for histological and immunohistochemical examination.

Results: All but one rat exhibited physiological growth and behaviour after the operation without differences between the Lyoplant^®-group (n = 12) and the sham group (n = 3). One rat from the sham group had to be excluded because of a suture leakage. No wound healing complications, wound infections and no herniation were observed. After 5 weeks the implants showed an adequate incorporation in all cases. This was confirmed by immunohistological analyses where a significant cell infiltration and neovascularization was observed.

Conclusion: In summary, Lyoplant^® appears to be a promising tool in experimental bladder augmentation/regeneration in rats.

Keywords: Biocompatible collagen mesh; Bladder regeneration/augmentation; Rat model.

Fig. 1

Macroscopic evaluation of adhesions in labaratory rats with A adhesion degree 0 and B adhesion degree 2 (black arrow points at macroscopic visible collagen-mesh, green arrow points at intestine and bladder wall grown together)

Fig. 2

A macroscopically completely incorporated collagen-mesh and B macoscopically visible collagen-mesh (Lyoplant^®; black arrow)

Fig. 3

Vascularisation in urinary bladder (black arrows) with incompletely incorporated collagen mesh (Lyoplant^®)

Fig. 4

Zone of transformation of untreated bladder wall with muscle layer to the area of implanted Lyoplant^®. Stars (*) mark small blood vessels in between the two layers, representing neovascularization (magnification: ×10)

Fig. 5

Immunohistochemical staining: CD4 positive cells (black arrows) around the remodulate Lyoplant^® (blue arrows; magnification: ×10)

Fig. 6

Immunohistochemical staining: CD68 positive cells (yellow arrows) around the suture material (Prolene^®, black arrow; magnification ×20)

Fig. 7

Hypothetic T_H2-Immunresponse to xenogeneic extracellular matrix grafts, such as Lyoplant^®