Future trends in bladder reconstructive surgery

In Vitro Construction of Urinary Bladder Wall using Porcine Primary Cells Reseeded on Acellularized Bladder Matrix and Small Intestinal Submucosa

BACKGROUND

Partial or radical cystectomy requires replacement of the urinary reservoir normally achieved by using small or large bowel segments. Our aim was to establish tissue engineering of an bioartificial bladder wall using primary cultures of porcine urothelial (pUC) and bladder smooth muscle cells (pSMC) to be reseeded on different acellular biological matrices.

METHODS

Primary porcine cultures of pUC and pSMC were established from open bladder biopsy material 25 mm2 in size. Acellular matrix was generated either from a) porcine bladder wall segments or b) tubular small intestinal submucosa with the still attached decellularized muscularis layer. Reseeding of these matrices with primary cells was done in a two-dimensional static model and in a three-dimensional rotating bioreactor perfused with cell culture medium for a period of 6 weeks.

RESULTS

Prior to reseeding the cultured cells were characterized as pUC and pSMC by immunohistochemical staining with either anti-keratin 7 or anti-alpha actin. For both matrices a reseeded double layer cell system of pUC and pSMC could be identified after incubation in the described systems for 6 weeks.

CONCLUSIONS

Our results document successful generation of tissue engineered urinary bladder wall, which can be used in further large animal transplantation experiments.

Bladder reconstruction using a collagen patch prefabricated within the omentum

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.

Altered phenotype of cultured urothelial and other stratified epithelial cells: implications for wound healing

The differentiation of cultured stratified epithelial cells can deviate significantly from that of normal epithelium, leading to suggestions that cultured cells undergo abnormal differentiation, or a truncated differentiation. Thus cultured epidermal and corneal epithelial cells stop synthesizing their tissue-specific keratin pair K1/K10 and K3/K12, respectively. The replacement of these keratins in the suprabasal compartment by K6/K16 keratins that are made by all stratified squamous epithelia during hyperplasia rules out a truncated differentiation. Importantly, the keratin pattern of in vivo corneal epithelium undergoing wound repair mimics that of cultured rabbit corneal epithelial cells. Although cultured urothelial cells continue to synthesize uroplakins, which normally form two-dimensional crystalline urothelial plaques covering almost the entire apical urothelial surface, these proteins do not assemble into crystals in cultured cells. Cultured epithelial cells can, however, rapidly regain normal differentiation on the removal of mitogenic stimuli, the use of a suitable extracellular matrix, or the transplantation of the cells to an in vivo, nonmitogenic environment. These data suggest that cultured epithelial cells adopt altered differentiation patterns mimicking in vivo regenerating or hyperplastic epithelia. Blocking the synthesis of tissue-specific differentiation products, such as the K1 and K10 keratins designed to form extensive disulfide cross-links in cornified cells, or the assembly of uroplakin plaques allows epithelial cells to better migrate and proliferate, activities that are of overriding importance during wound repair. Cultured urothelial and other stratified epithelial cells provide excellent models for studying the regulation of the synthesis and assembly of differentiation products, a key cellular process during epithelial wound repair.

Regenerative medicine and developmental biology: the role of the extracellular matrix

The principles and ultimate goals of regenerative medicine and developmental biology involve a complex sequence of events, culminating in the formation of structurally and functionally normal tissues and organs. The molecular composition of the extracellular matrix (ECM) plays a critical role in cellular migration and differentiation events. Mammalian ECM, derived from various tissues and organs, has been used as a biologic scaffold for therapeutic regenerative applications. Hundreds of thousands of human patients have benefited from the use of biologic scaffolds composed of naturally occurring ECM. The mechanisms by which ECM induces constructive remodeling instead of scar tissue formation are only beginning to be understood. This article reviews composition of mammalian ECM, its poorly understood role in developmental biology, and the clinical applications that have resulted from the use of this naturally occurring scaffold.

Cellular basis of urothelial squamous metaplasia: roles of lineage heterogeneity and cell replacement

Although the epithelial lining of much of the mammalian urinary tract is known simply as the urothelium, this epithelium can be divided into at least three lineages of renal pelvis/ureter, bladder/trigone, and proximal urethra based on their embryonic origin, uroplakin content, keratin expression pattern, in vitro growth potential, and propensity to keratinize during vitamin A deficiency. Moreover, these cells remain phenotypically distinct even after they have been serially passaged under identical culture conditions, thus ruling out local mesenchymal influence as the sole cause of their in vivo differences. During vitamin A deficiency, mouse urothelium form multiple keratinized foci in proximal urethra probably originating from scattered K14-positive basal cells, and the keratinized epithelium expands horizontally to replace the surrounding normal urothelium. These data suggest that the urothelium consists of multiple cell lineages, that trigone urothelium is closely related to the urothelium covering the rest of the bladder, and that lineage heterogeneity coupled with cell migration/replacement form the cellular basis for urothelial squamous metaplasia.

[Current status of tissue engineering in urology. Review of the literature]

In the eighties a new field of the medicine appears wich applies the principles of cellular cultivation to synthetic biodegradable polymers scaffolds with the purpose of creating autologous biological substitutes that could improve, maintain or restore the function of organs or damaged tissues. The Tissue Engineering constitutes a new discipline in full phase of development especially in USA, with multiple potential applications in several medical specialities. Our speciality can't remain indifferent to interest and encouraging future originated by this new science. In this work we have made a wide bibliographical revision in the Medline to know the antecedents, current state and the possible future applications of Tissue Engineering in Urology.

Long-term outcome of bladder augmentation using living-related partial bladder transplantation in rats

Long-term histopathologic changes after bladder augmentation (BA) in rats using living-related partial bladder transplantation (LPBTx) or conventional ileocystoplasty (ICP) were compared. In this study, BA (n = 37), LPBTx (n = 18), and ICP (n = 19) were performed in 16-wk-old Lewis rats. Five donors and seven nontransplanted normal Lewis rats (controls) were also studied. Rats that survived >10 mo after BA were killed after blood biochemistry and neobladder imaging. Harvested bladders were examined with hematoxylin and eosin and proliferating cell nuclear antigen (PCNA). When the rats were killed, there were 16 rats in the LPBTx group and 12 rats in the ICP group; ICP rats were significantly smaller than LPBTx rats (p < 0.05). Mean duration of follow-up for the LPBTX group was 17.3 mo, for the ICP group was 13.7 mo, for the donor group was 16.1 mo, and for the control group was 19.7 mo. Mean serum pH in the LPBTx group was 7.41 +/- 0.78 and in the ICP group was 7.25 +/- 0.38. Mean base excess in the ICP group was significantly lower than in the LPBTx group (p < 0.05). Incidence of bladder calculi in the LPBTx group (6.3%) was significantly lower than in the ICP group (33.3%; p < 0.05). There was no dysplasia/malignancy/increase in PCNA in the LPBTx group. PCNA increased in the ICP group, compared with controls (p < 0.05); two (16.7%) of 12 of ICP rats had dysplasia with mitosis. Bladder capacity increased in LPBTx and ICP compared with controls (both p < 0.05). We hope to show that BA using LPBTx may result in a neobladder with fewer complications than BA using ICP; LPBTx may also decrease the risk for malignancy.

Tissue-engineered urinary bladder wall using PLGA mesh-collagen hybrid scaffolds: a comparison study of collagen sponge and gel as a scaffold

PURPOSE

Tissue engineering of the urinary bladder using autologous cells and biodegradable scaffold is a promising method for augmentation. The authors developed 2 hybrid scaffolds by combining poly (DL-lactic-co-glycolic acid; PLGA) mesh for mechanical strength with collagen sponge or gel suitable for cell seeding. The aim of this study was to compare collagen as a scaffold between collagen sponge and gel and to construct a tissue-engineered urinary bladder wall utilizing these hybrid scaffolds.

METHODS

The PLGA mesh-collagen hybrid scaffolds were prepared by introducing collagen sponge or gel into the PLGA knitted mesh. Urothelial and smooth muscle cells were obtained from porcine urinary bladder wall and were cultured in their respective media. The cells were seeded on these hybrid scaffolds. These constructs were analyzed morphologically and immunohistochemically.

RESULTS

The urothelial layer was generated 3 dimensionally by culturing urothelial cells with PLGA mesh and collagen sponge. The smooth muscle layer was constructed by culturing smooth muscle cells with PLGA mesh and collagen gel. And a novel tissue-engineered urinary bladder wall was constructed laminating the urothelial and smooth muscle layers.

CONCLUSIONS

Ex vivo construction of urinary bladder wall using hybrid scaffolds prepared by combining PLGA mesh with collagen sponge or gel was successful. This tissue-engineered urinary bladder wall allows easy handling and may become a promising tool for bladder augmentation.