Cell-specific activation of the HB-EGF and ErbB1 genes by stretch in primary human bladder cells

Applications of tissue engineering in the genitourinary tract

Congenital abnormalities and acquired disorders can lead to organ damage or loss of tissue within the genitourinary tract. For reconstructive purposes, tissue-engineering efforts are currently underway for virtually every type of tissue and organ within the urinary tract. Tissue engineering incorporates the fields of cell transplantation, materials science and engineering for the purpose of creating functional replacement tissue. This article reviews some of the principles of tissue engineering and some of the applications of these principles to the genitourinary tract.

Tissue engineering of reproductive tissues and organs

Regenerative medicine and tissue engineering technology may soon offer new hope for patients with serious injuries and end-stage reproductive organ failure. Scientists are now applying the principles of cell transplantation, material science, and bioengineering to construct biological substitutes that can restore and maintain normal function in diseased and injured reproductive tissues. In addition, the stem cell field is advancing, and new discoveries in this field will lead to new therapeutic strategies. For example, newly discovered types of stem cells have been retrieved from uterine tissues such as amniotic fluid and placental stem cells. The process of therapeutic cloning and the creation of induced pluripotent cells provide still other potential sources of stem cells for cell-based tissue engineering applications. Although stem cells are still in the research phase, some therapies arising from tissue engineering endeavors that make use of autologous adult cells have already entered the clinic. This article discusses these tissue engineering strategies for various organs in the male and female reproductive tract.

Tissue engineering of the penis

Congenital disorders, cancer, trauma, or other conditions of the genitourinary tract can lead to significant organ damage or loss of function, necessitating eventual reconstruction or replacement of the damaged structures. However, current reconstructive techniques are limited by issues of tissue availability and compatibility. Physicians and scientists have begun to explore tissue engineering and regenerative medicine strategies for repair and reconstruction of the genitourinary tract. Tissue engineering allows the development of biological substitutes which could potentially restore normal function. Tissue engineering efforts designed to treat or replace most organs are currently being undertaken. Most of these efforts have occurred within the past decade. However, before these engineering techniques can be applied to humans, further studies are needed to ensure the safety and efficacy of these new materials. Recent progress suggests that engineered urologic tissues and cell therapy may soon have clinical applicability.

Regenerative medicine strategies for treating neurogenic bladder

Neurogenic bladder is a general term encompassing various neurologic dysfunctions of the bladder and the external urethral sphincter. These can be caused by damage or disease. Therapeutic management options can be conservative, minimally invasive, or surgical. The current standard for surgical management is bladder augmentation using intestinal segments. However, because intestinal tissue possesses different functional characteristics than bladder tissue, numerous complications can ensue, including excess mucus production, urinary stone formation, and malignancy. As a result, investigators have sought after alternative solutions. Tissue engineering is a scientific field that uses combinations of cells and biomaterials to encourage regeneration of new, healthy tissue and offers an alternative approach for the replacement of lost or deficient organs, including the bladder. Promising results using tissue-engineered bladder have already been obtained in children with neurogenic bladder caused by myelomeningocele. Human clinical trials, governed by the Food and Drug Administration, are ongoing in the United States in both children and adults to further evaluate the safety and efficacy of this technology. This review will introduce the principles of tissue engineering and discuss how it can be used to treat refractory cases of neurogenic bladder.

Tissue engineering: current strategies and future directions

Novel therapies resulting from regenerative medicine and tissue engineering technology may offer new hope for patients with injuries, end-stage organ failure, or other clinical issues. Currently, patients with diseased and injured organs are often treated with transplanted organs. However, there is a shortage of donor organs that is worsening yearly as the population ages and as the number of new cases of organ failure increases. Scientists in the field of regenerative medicine and tissue engineering are now applying the principles of cell transplantation, material science, and bioengineering to construct biological substitutes that can restore and maintain normal function in diseased and injured tissues. In addition, the stem cell field is a rapidly advancing part of regenerative medicine, and new discoveries in this field create new options for this type of therapy. For example, new types of stem cells, such as amniotic fluid and placental stem cells that can circumvent the ethical issues associated with embryonic stem cells, have been discovered. The process of therapeutic cloning and the creation of induced pluripotent cells provide still other potential sources of stem cells for cell-based tissue engineering applications. Although stem cells are still in the research phase, some therapies arising from tissue engineering endeavors that make use of autologous, adult cells have already entered the clinical setting, indicating that regenerative medicine holds much promise for the future.

Tissue engineering of human bladder

There are a number of conditions of the bladder that can lead to loss of function. Many of these require reconstructive procedures. However, current techniques may lead to a number of complications. Replacement of bladder tissues with functionally equivalent ones created in the laboratory could improve the outcome of reconstructive surgery. A review of the literature was conducted using PubMed to identify studies that provide evidence that tissue engineering techniques may be useful in the development of alternatives to current methods of bladder reconstruction. A number of animal studies and several clinical experiences show that it is possible to reconstruct the bladder using tissues and neo-organs produced in the laboratory. Materials that could be used to create functionally equivalent urologic tissues in the laboratory, especially non-autologous cells that have the potential to reject have many technical limitations. Current research suggests that the use of biomaterial-based, bladder-shaped scaffolds seeded with autologous urothelial and smooth muscle cells is currently the best option for bladder tissue engineering. Further research to develop novel biomaterials and cell sources, as well as information gained from developmental biology, signal transduction studies and studies of the wound healing response would be beneficial.

Cell-based therapy for urinary incontinence

Urinary incontinence has become a societal problem that affects millions of people worldwide. Although numerous therapeutic modalities are available, none has been shown to be entirely satisfactory. Consequently, cell-based approaches using regenerative medicine technology have emerged as a potential solution that would provide a means of correcting anatomical deficiencies and restoring normal function. As such, numerous cell-based investigations have been performed to develop systems that are focused on addressing clinical needs. While most of these attempts remain in the experimental stages, several clinical trials are being designed or are in progress. This article provides an overview of the cell-based approaches that utilize various cell sources to develop effective treatment modalities for urinary incontinence.

Engineering tissues, organs and cells

Patients suffering from diseased and injured organs may be treated with transplanted organs; however, there is a severe shortage of donor organs that is worsening yearly, given the ageing population. In the field of regenerative medicine and tissue engineering, scientists apply the principles of cell transplantation, materials science and bioengineering to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues. Therapeutic cloning, where the nucleus from a donor cell is transferred into an enucleated oocyte in order to extract pluripotent embryonic stem cells, offers a potentially limitless source of cells for tissue engineering applications. The stem cell field is also advancing rapidly, opening new options for therapy, including the use of amniotic and placental fetal stem cells. This review covers recent advances that have occurred in regenerative medicine and describes applications of these technologies using chemical compounds that may offer novel therapies for patients with end-stage organ failure.

Inhibition of EGFR signaling abrogates smooth muscle proliferation resulting from sustained distension of the urinary bladder

Urinary bladder outlet obstruction results in sustained stretch of the detrusor muscle and can lead to pathological smooth muscle hyperplasia and hypertrophy. The epidermal growth factor receptor (EGFR) is a cognate receptor for mitogens implicated in bladder hyperplasia/hypertrophy. Here, we investigated the potential for modulation of this pathway by pharmacologic targeting with a clinically available EGFR antagonist using an organ culture model of bladder stretch injury as a test system. Urinary bladders from adult female rats were distended in vivo with medium containing the EGFR inhibitor ZD1839 (gefitinib, Iressa). The bladders were excised and incubated in ex vivo organ culture for 4-24 h. EGFR phosphorylation, DNA proliferation, and the extent of apoptosis in the cultured tissues were assessed. To verify that the smooth muscle cells (SMC) are a target of the EGFR inhibitor, primary culture human and rat bladder SMC were subjected to cyclic mechanical stretch in vitro in the presence of ZD1839. Levels of phosphorylated EGFR were significantly increased in the detrusor muscle with 12 h of stretch in the organ cultures. This activation coincided with a subsequent 23-fold increase in DNA synthesis and a 30-fold decrease in apoptosis in the muscle compartment at 24 h. In the presence of ZD1839, DNA synthesis was reduced to basal levels without an increase in the rate of apoptosis under ex vivo conditions. Mechanical stretch of bladder SMC in vitro resulted in a significant increase in DNA synthesis, which was completely abrogated by treatment with ZD1839 but not by AG825, an inhibitor of the related receptor, ErbB2. Our results indicate that the EGFR pathway is a physiologically relevant signaling mechanism in hypertrophic bladder disease resulting from mechanical distension and may be amenable to pharmacologic intervention.

Tissue Engineering Using Adult Stem Cells

Patients with a variety of diseases may be treated with transplanted tissues and organs. However, there is a shortage of donor tissues and organs, which is worsening yearly because of the aging population. Scientists in the field of tissue engineering are applying the principles of cell transplantation, material science, and bioengineering to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues. The stem cell field is also advancing rapidly, opening new options for cellular therapy and tissue engineering. The use of adult stem cells for tissue engineering applications is promising. This chapter discusses applications of these new technologies for the engineering of tissues and organs. The first part provides an overview of regenerative medicine and tissue engineering techniques; the second highlights different adult stem cell populations used for tissue regeneration.

Tissue engineering, stem cells and cloning: current concepts and changing trends

Organ damage or loss can occur from congenital disorders, cancer, trauma, infection, inflammation, iatrogenic injuries or other conditions and often necessitates reconstruction or replacement. Replacement may take the form of organ transplant. At present, there is a severe shortage of donor organs that is worsening with the aging of the population. Tissue engineering follows the principles of cell transplantation, materials science and engineering towards the development of biological substitutes that can restore and maintain normal tissue function. Therapeutic cloning involves the introduction of a nucleus from a donor cell into an enucleated oocyte to generate embryonic stem cell lines whose genetic material is identical to that of its source. These autologous stem cells have the potential to become almost any type of cell in the adult body, and thus would be useful in tissue and organ replacement applications. This paper reviews recent advances in stem cell research and regenerative medicine, and describes the clinical applications of these technologies as novel therapies for tissue or organ loss.

An oxidative stress mechanism mediates chelerythrine-induced heparin-binding EGF-like growth factor ectodomain shedding

Regulated shedding of cell surface proteins is a mechanism for rapid activation of autocrine and paracrine signaling. Here we report that chelerythrine, a protein kinase C (PKC) inhibitor that possesses a variety of biological functions, is a potent inducer of heparin-binding epidermal growth factor-like growth factor (HB-EGF) shedding from the cell surface. Chelerythrine induced a time- and dose-dependent shedding of an HB-EGF-alkaline phosphatase (HB-EGF-AP) fusion protein expressed in MC2 rat prostate epithelial cells. The soluble form of HB-EGF-AP bound to heparin and exhibited potent biological activity as measured by DNA synthesis assay. Chelerythrine-induced HB-EGF shedding was metalloproteinase-(MMP-) mediated because specific MMP antagonists inhibited shedding by > or =60%. Chelerythrine stimulated production of reactive oxygen species, and antioxidants prevented chelerythrine-induced HB-EGF shedding, suggesting that the production of intracellular peroxides is necessary for this event. Consistent with this possibility, antioxidant- and MMP-inhibitable shedding was also demonstrated when hydrogen peroxide was used as an inducer. Although JNK/SAPK and p38 MAPK pathways were activated by chelerythine, these signaling mechanisms were not required to mediate the shedding event. However, JNK signaling was involved in chelerythrine-stimulated apoptosis. Our results suggest that HB-EGF shedding induced by chelerythrine is mediated predominantly via the production of reactive oxygen species.

Growth and stretch response of human exstrophy bladder smooth muscle cells: molecular evidence of normal intrinsic function

OBJECTIVE

To establish primary cultures of smooth muscle cells (SMC) from human exstrophic bladders (E-SMC), and determine their in vitro growth dynamics and responses to mechanical stretch.

MATERIALS AND METHODS

Primary cultures of E-SMC from three patients were established from exstrophic bladder tissue using an explant method. Growth dynamics were assessed using tetrazolium-dye uptake. The DNA synthesis rate in response to cyclic stretch-relaxation was determined with thymidine-incorporation assays. Expression of the SMC mitogen heparin-binding epidermal growth factor-like growth factor (HB-EGF) mRNA in response to mechanical stretch was determined using semiquantitative reverse transcription-polymerase chain reaction.

RESULTS

The approximate doubling time of the E-SMC grown in the presence of serum was 4 days, consistent with growth rates of SMC reported previously. E-SMC exposed to stretch had greater DNA synthesis, albeit to a lesser extent than previously seen with non-exstrophic SMC. The expression of HB-EGF was also increased in cells exposed to mechanical stimuli, consistent with our previous finding of stretch-regulated HB-EGF gene expression in bladder SMC.

CONCLUSIONS

E-SMC had growth characteristics similar to those previously reported in non-exstrophic cells. E-SMC also had stretch-induced expression of HB-EGF mRNA. These observations provide evidence that despite development in an abnormal defunctionalized state, E-SMC retain the potential for normal growth, and may modulate this response through mechanisms similar to those operating in normal bladder SMC.

Tissue engineering, stem cells, cloning, and parthenogenesis: new paradigms for therapy

Patients suffering from diseased and injured organs may be treated with transplanted organs. However, there is a severe shortage of donor organs which is worsening yearly due to the aging population. Scientists in the field of tissue engineering apply the principles of cell transplantation, materials science, and bioengineering to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues. Both therapeutic cloning (nucleus from a donor cell is transferred into an enucleated oocyte), and parthenogenesis (oocyte is activated and stimulated to divide), permit extraction of pluripotent embryonic stem cells, and offer a potentially limitless source of cells for tissue engineering applications. The stem cell field is also advancing rapidly, opening new options for therapy. The present article reviews recent progress in tissue engineering and describes applications of these new technologies that may offer novel therapies for patients with end-stage organ failure.

Mechanical stretch is a highly selective regulator of gene expression in human bladder smooth muscle cells

Application of mechanical stimuli has been shown to alter gene expression in bladder smooth muscle cells (SMC). To date, only a limited number of "stretch-responsive" genes in this cell type have been reported. We employed oligonucleotide arrays to identify stretch-sensitive genes in primary culture human bladder SMC subjected to repetitive mechanical stimulation for 4 h. Differential gene expression between stretched and nonstretched cells was assessed using Significance Analysis of Microarrays (SAM). Expression of 20 out of 11,731 expressed genes ( approximately 0.17%) was altered >2-fold following stretch, with 19 genes induced and one gene (FGF-9) repressed. Using real-time RT-PCR, we tested independently the responsiveness of 15 genes to stretch and to platelet-derived growth factor-BB (PDGF-BB), another hypertrophic stimulus for bladder SMC. In response to both stimuli, expression of 13 genes increased, 1 gene (FGF-9) decreased, and 1 gene was unchanged. Six transcripts (HB-EGF, BMP-2, COX-2, LIF, PAR-2, and FGF-9) were evaluated using an ex vivo rat model of bladder distension. HB-EGF, BMP-2, COX-2, LIF, and PAR-2 increased with bladder stretch ex vivo, whereas FGF-9 decreased, consistent with expression changes observed in vitro. In silico analysis of microarray data using the FIRED algorithm identified c-jun, AP-1, ATF-2, and neurofibromin-1 (NF-1) as potential transcriptional mediators of stretch signals. Furthermore, the promoters of 9 of 13 stretch-responsive genes contained AP-1 binding sites. These observations identify stretch as a highly selective regulator of gene expression in bladder SMC. Moreover, they suggest that mechanical and growth factor signals converge on common transcriptional regulators that include members of the AP-1 family.

Tissue engineering and regenerative medicine: concepts for clinical application

Patients suffering from diseased and injured organs may be treated with transplanted organs. However, there is a severe shortage of donor organs that is worsening yearly given the aging population. Scientists in the field of regenerative medicine and tissue engineering apply the principles of cell transplantation, material science, and bioengineering to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues. Therapeutic cloning, where the nucleus from a donor cell is transferred into an enucleated oocyte in order to extract pluripotent embryonic stem cells, offers a potentially limitless source of cells for tissue engineering applications. The stem cell field is also advancing rapidly, opening new options for therapy. This paper reviews recent advances that have occurred in regenerative medicine and describes applications of these new technologies that may offer novel therapies for patients with end-stage organ failure.

Tissue engineering for the replacement of organ function in the genitourinary system

Acquired and congenital abnormalities may lead to genitourinary organ damage or loss, requiring eventual reconstruction. Tissue engineering follows the principles of cell transplantation, materials science, and engineering toward the development of biological substitutes that would restore and maintain normal function. Tissue engineering may involve matrices alone, wherein the body's natural ability to regenerate is used to orient or direct new tissue growth, or the use of matrices with cells. Both synthetic and natural biodegradable materials have been used, either alone or as cell delivery vehicles. Tissue engineering has been applied experimentally for the reconstitution of several urologic tissues and organs, including bladder, ureter, urethra, kidney, testis, and genitalia. Fetal applications have also been explored. Recently, several tissue engineering technologies have been used clinically including the use of cells as bulking agents for the treatment of vesicoureteral reflux and incontinence and urethral replacement. Recent progress suggests that engineered genitourinary tissues may have clinical applicability in the future.

Tissue engineering, stem cells, and cloning for the regeneration of urologic organs

Tissue engineering efforts are currently being undertaken for every type of tissue and organ within the urinary system. Most of the effort expended to engineer genitourinary tissues has occurred within the last decade. Tissue engineering techniques require a cell culture facility designed for human application. Personnel who have mastered the techniques of cell harvest, culture, and expansion as well as polymer design are essential for the successful application of this technology. Various engineered genitourinary tissues are at different stages of development, with some already being used clinically, a few in preclinical trials, and some in the discovery stage. Recent progress suggests that engineered urologic tissues may have an expanded clinical applicability in the future.

Signaling through PI3K/Akt mediates stretch and PDGF-BB-dependent DNA synthesis in bladder smooth muscle cells

PURPOSE

Smooth muscle cells (SMC) of the bladder undergo hypertrophy and hyperplasia following exposure to sustained mechanical overload. Although superficial similarities in the response of the heart and bladder to hypertrophic stimuli suggest that similar molecular mechanisms may be involved, this remains to be demonstrated. In this study we compared signal transduction pathway activation in primary culture bladder SMC and cardiac myofibroblasts in response to cyclic stretch. The effects of growth factor stimulation on pathway activation in bladder SMC were also investigated.

MATERIALS AND METHODS

Primary culture rodent bladder SMC or cardiac myofibroblasts were subjected to cyclic stretch-relaxation in the absence or presence of pharmacologic inhibitors of the phosphoinositide-3-kinase, (PI3K)/Akt, extracellular signal-regulated kinase-mitogen activated protein kinase (Erk-MAPK) or the p38 stress-activated protein kinase-2 (SAPK2) pathways. In parallel experiments human bladder SMC were treated with platelet-derived growth factor-BB (PDGF-BB), heparin-binding EGF-like growth factor (HB-EGF) or fibroblast growth factor-2 (FGF-2). In each case the extent of DNA synthesis was determined by uptake of tritiated thymidine, and activation of specific signaling intermediates was determined by immunoblot analysis using antibodies to the non-phosphorylated and phosphorylated (activated) forms of Akt, p38 and Erk1/2.

RESULTS

Akt and p38 were rapidly phosphorylated in stretched bladder SMC and cardiac myofibroblasts, and stretch-induced DNA synthesis in these cells was ablated with inhibitors of PI3K or p38 but not Erk-MAPK. Similarly, PDGF-BB up-regulated DNA synthesis in bladder SMC in a p38 and Akt-dependent manner.

CONCLUSIONS

We conclude that distinct stimuli, such as mechanical stretch and PDGF-BB, promote DNA synthesis in bladder SMC through shared downstream signaling pathways. Furthermore, phenotypically similar cells from the bladder and heart show comparable pathway activation in response to stretch. These findings suggest that similar molecular mechanisms underlie the altered growth responses of the bladder and heart to mechanical overload. This study also provides the first report of Akt activation in bladder SMC and suggests that Akt, consistent with its pivotal role in cardiac hypertrophy, may also be a key regulator of remodeling in the SMC compartment of the bladder exposed to hypertrophic/hyperplastic stimuli in vivo.

Platelet derived growth factor-BB is a potent mitogen for rat ureteral and human bladder smooth muscle cells: dependence on lipid rafts for cell signaling

PURPOSE

Fibromuscular tissues of the detrusor/bladder body (B), trigone (T) and ureter (U) display distinct patterns of tissue remodeling in pathologic contexts, however the mechanisms underlying these observations are unknown. In this study we asked whether B, T and U smooth muscle cells (SMC) respond to several SMC growth factors and explored the role of caveolae/lipid raft membrane microdomains in signaling by one of these factors, PDGF-BB.

MATERIALS AND METHODS

SMC were isolated and cultured from B, T and U from newborn rats and from human bladder detrusor. Responses to growth factors were assessed by cell proliferation, DNA synthesis, and immunoblot methods. Cholesterol was depleted from cell membranes in select experiments using cyclodextrin and the cholesterol synthesis inhibitor lovastatin. High-affinity PDGF receptor (PDGFR) sites were measured by 125I-PDGF-BB binding assay.

RESULTS

PDGF-BB increased DNA synthesis rate in U and T SMC, with U SMC being highly responsive; in contrast, B SMC did not respond to this growth factor. Two other mitogens, HB-EGF and FGF-2, marginally stimulated DNA synthesis in all lineages. Human detrusor (hD) SMC were also highly responsive to PDGF-BB. Differences in responses to PDGF-BB correlated with translocation of PDGFRs into the caveolae/lipid raft membrane fraction following stimulation, but not with the number of high affinity PDGF binding sites. Cholesterol depletion from cell membranes reduced the response of U and hD SMC to PDGF-BB.

CONCLUSIONS

These findings indicate that 1) PDGF-BB is likely to be a physiologically relevant stimulator of mitogenic signaling in certain types of urinary tract SMC, 2) there are significant and unanticipated regional differences in the ability of urinary tract SMC to respond to muscle mitogens, and 3) lipid raft membrane microdomains mediate, in part, the ability of urinary tract SMC to respond to PDGF-mediated signals.

Future trends in bladder reconstructive surgery

The incorporation of bowel into the urinary tract is associated with significant long-term complications. Therefore, considerable efforts are being made to avoid the use of enteric epithelium in bladder reconstruction. The simplest of these entail the use of native urothelium that is already available, with techniques such as auto-augmentation, auto-augmentation de-epithelialized enterocystoplasty, and ureterocystoplasty. Unfortunately, in many patients, the bladder is too small, or dilated ureters are not available, and these techniques cannot be applied. Recently, experimental techniques are examining the use of tissue expansion to the ureter and bladder to increase the volume of tissue available. Tissue engineering techniques are being applied to bladder regeneration, and considerable advances have already been made leading to in vivo animal experimentation, the results of which are very encouraging. The details of these most recent advances will be discussed in detail in this report.

Experimental and clinical experience with tissue engineering techniques for urethral reconstruction

Tissue engineering has been proposed as a strategy for urethral reconstruction. This may involve matrices alone, wherein the body's natural ability to regenerate is used to orient or direct new tissue growth, or the use of matrices with cells. Acellular collagen matrices derived from donor bladder submucosa have been used both experimentally and clinically for onlay urethral replacement with good success at our center. If a tubularized urethral repair is needed, the use of cells on the collagen matrix is essential for adequate tissue formation. Tissue engineering techniques are useful for urethral reconstruction.

The decision to undergo DNA or protein synthesis is determined by the degree of mechanical deformation in human bladder muscle cells

OBJECTIVES

To investigate the effect of varying levels of mechanical deformation (cyclic stretch-relaxation) on protein and DNA synthesis rates in human bladder smooth muscle cells (SMCs). Cells in the bladder wall respond to outlet obstruction by increasing rates of protein synthesis ("hypertrophy") and/or DNA synthesis ("hyperplasia"); however, it is not established how these distinct processes are initiated.

METHODS

Primary cultures of human bladder SMCs were generated and maintained according to published methods. Cells were plated on type I collagen-coated elastomer-bottomed plates and subjected to cyclical stretch-relaxation (0.1 Hz) at 6%, 12%, and 20% elongation using a computer-controlled stretch-inducing device. DNA and protein synthesis rates were determined by uptake of radiolabeled thymidine and leucine, respectively. Nonstretched cells served as controls.

RESULTS

Mechanical stretch stimulated DNA synthesis in a dose and time-dependent manner with marked upregulation (4.5-fold) in response to 20% elongation. Mechanical deformation also elicited changes in protein synthesis in bladder SMCs. However, in contrast to the DNA synthesis pattern, leucine uptake over time was stimulated at 6% and 12% elongation, and no protein synthesis response was seen at 20% elongation.

CONCLUSIONS

Our findings suggest that stretch, in isolation from other potential mediators such as pressure or hypoxia, can induce either a hyperplastic or hypertrophic response in bladder SMCs and that the cells' response is dependent on the intensity of the stretch stimulus. These observations may be relevant to the process of in vivo tissue remodeling stimulated by bladder distension or contractile dysfunction.

Long-term culture of porcine bladder epithelial cells

Epithelial cells from normal pig bladders proliferated when cocultured with lethally irradiated feeder cells of the LA7 rat mammary tumor line. When the bladder cells and feeders were plated together at a confluent density, the bladder cells proliferated as the feeder cells died, resulting in a confluent culture of bladder cells. The bladder cells were successfully subcultured by plating with freshly irradiated LA7 feeder cells. In this way, bladder cells from five pigs were carried to confluency in passages 1, 4, 7, 7, and 13, amounting to at least 6, 18, 24, 26, and 45 doublings in culture, respectively, and none showed signs of slowed proliferation at the time of culture termination. Fibroblasts never became a prominent feature of these cultures, and their frequency was determined to be about 26 fibroblasts per 10(5) cells in passage 9. Pig bladder cells in 0.5% serum doubled in number in slightly over 3 d, whereas cells in 5.0% serum doubled in about 6 d. In fresh medium without feeder cells only minimal proliferation of bladder cells occurred. In LA7-conditioned medium the bladder cell numbers decreased, leading to the conclusion that the stimulus from LA7 cells is mechanically or physically transmitted. The bladder cells reacted with antibodies to keratins 7 and 18 but not to keratin 14 or vimentin. Tight junctions, visualized with an antibody to the ZO1 protein, connected all the cells to their neighbors. Most cells in passage 9 carried the diploid chromosome number of 38.

Juxtacrine stimulation of normal and malignant human bladder epithelial cell proliferation

PURPOSE

We developed a method for culturing normal and malignant human bladder epithelial cells for many generations.

MATERIALS AND METHODS

Cells from bladder washes or surgical specimens were plated in culture with lethally irradiated cells of the LA7 rat mammary tumor line (American Type Culture Collection, Bethesda, Maryland) at a confluent density and fed regularly. After cells from surgical specimens became confluent they were diluted and subcultured with fresh irradiated LA7 cells. The growth rate was measured by cell counts and cell sorter analysis. Expression of intermediate filaments was determined by immunocytochemical testing.

RESULTS

All 5 normal and 3 of the 4 tumor specimens developed into long-term cell strains. A single normal strain was carried through passage 11, amounting to 37 cell doublings. Cell numbers doubled in 2 days in medium with 0.5% serum and in 5.6 days in 5% serum. Plating efficiency was almost 100% and cloning efficiency was approximately 9%. LA7 conditioned medium did not stimulate bladder cell proliferation. Two tumor strains were carried through passage 9, amounting to 20 and 27 doublings, respectively. No cell strains expressed signs of senescence at culture termination. Normal and tumor strains expressed keratins 7, 10, 11, 18 and 19, and ZO1 tight junction protein but not vimentin or keratin 14. Umbrella cells comprised the uppermost cell layer in cultures from normal bladder.

CONCLUSIONS

LA7 feeder cells stimulate human bladder cell proliferation for many generations in culture by a juxtacrine mechanism and promote the expression of differentiated traits.

Partial ureteral obstruction dysregulates the renal renin-angiotensin system in the fetal sheep kidney

OBJECTIVES

To investigate whether partial ureteral obstruction (PUO) in the fetus induces dysregulation of the renin-angiotensin system (RAS) and of transforming growth factor-beta 1 (TGF-beta1) and tissue inhibitors of metalloproteinase (TIMP1) expression. Previous studies have indicated that renal and urinary tract development depend on an intact renal RAS. Fetal urinary obstruction is distinct from postnatal obstruction. It has been suggested in postnatal animal studies that dysregulation of the RAS, and subsequent increased expression of TGF-beta1 and TIMP1, leads to changes in extracellular matrix composition.

METHODS

Bilateral PUO was created in 4 fetal sheep. Seven animals (four obstructed and three controls) were killed at birth and their kidneys removed. Semiquantitative reverse transcriptase-polymerase chain reaction was used to quantify the levels of renin, angiotensinogen, angiotensin receptor type 1 (AT1 receptor), angiotensin receptor type 2 (AT2 receptor), TGF-beta1, and TIMP1. These messages were normalized to glyceraldehyde-3-phosphate dehydrogenase mRNA.

RESULTS

All obstructed animals had moderate to severe hydronephrosis with enlarged kidneys (mean weight 22.0 g versus 9.4 g for the control animals; P <0.05). The increase in the levels of renin, angiotensinogen, AT1 receptor, TGF-beta1, and TIMP1 mRNA was significant in the PUO group compared with the control group (P <0.05). AT2 receptor levels did not increase, but the AT1/AT2 mRNA ratio was significantly increased over normal (P <0.005). Also, a significant linear correlation was found between the increased renal weight and increased TGF-beta1 mRNA levels (P <0.005).

CONCLUSIONS

Our findings suggest that fetal PUO can cause upregulation of the renal RAS and increased expression of TGF-beta1 and TIMP1, which may alter the balance between the generation and degradation of the extracellular matrix. The coordinate increases in renin, angiotensinogen, and AT1 receptor mRNA levels in chronic fetal PUO may represent a maladaptive response that contributes to interstitial fibrosis and prolonged vasoconstriction. RAS components and growth factors, particularly TGF-beta1, may be considered relevant targets in the prevention and treatment of congenital obstructive nephropathy.

Tissue engineering in urology

Congenital abnormalities, cancer, trauma, infection, inflammation, iatrogenic injuries, and other conditions may lead to genitourinary organ damage or loss, requiring eventual reconstruction. Tissue engineering follows the principles of cell transplantation, materials science, and engineering toward the development of biological substitutes that would restore and maintain normal function. Tissue engineering may involve matrices alone, wherein the body's natural ability to regenerate is used to orient or direct new tissue growth, or the use of matrices with cells. Both synthetic (polyglycolic acid polymer scaffolds alone and with co-polymers of poly-1-lactic acid and poly-DL-lactide-coglycolide) and natural biodegradable materials (processed collagen derived from allogeneic donor bladder submucosa and intestinal submucosa) have been used, either alone or as cell delivery vehicles. Tissue engineering has been applied experimentally for the reconstitution of several urologic tissues and organs, including bladder, ureter, urethra, kidney, testis, and genitalia. Fetal applications have also been explored. Recently, several tissue engineering technologies have been used clinically, including the use of cells as bulking agents for the treatment of vesicoureteral reflux and incontinence, urethral replacement, and bladder reconstruction. Recent progress suggests that engineered urologic tissues may have clinical applicability in the future.

Heparin-binding EGF-like growth factor is up-regulated in the obstructed kidney in a cell- and region-specific manner and acts to inhibit apoptosis

The expression of certain growth factors in the epidermal growth factor (EGF) family is altered in response to renal injury. Recent studies have demonstrated that heparin binding EGF-like growth factor (HB-EGF) expression may be cytoprotective in response to apoptotic signals. The purpose of this study was to investigate the potential role of HB-EGF in the upper urinary tract following unilateral ureteral obstruction. We present evidence that: i) ureteral obstruction induced cell-specific but transient activation of HB-EGF gene expression; ii) HB-EGF expression in renal epithelial cells increased under conditions where mechanical deformation, such as that caused by hydronephrotic distension, induces apoptosis, but HB-EGF expression did not increase in renal pelvis smooth muscle cells under identical conditions; and iii) enforced expression of HB-EGF served to protect renal epithelial cells from stretch-induced apoptosis. These results suggest a potential mechanism by which the kidney protects itself from apoptosis triggered by urinary tract obstruction.