Intraoral wound closure with tissue-engineered mucosa: new perspectives for urethra reconstruction with buccal mucosa grafts

Bilateral Buccal Mucosa Graft for Urethroplasty: A Versatile Graft

Male urethral stricture is scarring of the urethral tissue that narrows the urethral lumen causing reduced urinary flow. Urethral reconstruction or substitution urethroplasty using oral mucosa graft, especially from the buccal mucosa, is one of the most widely known techniques to manage urethral stricture. However, studies using bilateral buccal mucosa are still limited. Therefore, this study aims to report our experience and technique of bilateral buccal mucosa grafting for urethroplasty. The authors described a 66-year-old man with long-segment urethral stricture that was successfully treated with urethral reconstruction harvested from bilateral buccal mucosa.

Oral mucosa grafting in periorbital reconstruction

To provide an extensive literature review on the clinical indications of oral mucosa grafts (OMG) and minor salivary gland grafts (MSGG) in periorbital reconstruction together with safe practice graft harvesting techniques to minimize donor-site morbidity. A literature review was performed by searching the databases of PUBMED, EMBASE, and COCHRANE library using the keywords: minor salivary glands; oral mucosal graft; orbit; and eye. The bibliographies of the pertinent articles were examined for additional papers. Indications for OMG include treatment of recurrent pterygia; socket contracture in anophthalmic patients; repair of eyelid deformities; ocular surface and fornix reconstruction following tumour resection, cicatricial ocular surface disorders, or chemical burns. More novel uses include repair of glaucoma aqueous drainage device erosions or leaking trabeculectomy blebs; scleral buckle exposure; and keratoprosthesis-related corneal melts as well as lining the dacryocystorhinostomy tract to prevent closure. Simultaneous MSGG transplantation may be used in the treatment of severe dry eyes or dry anophthalmic cavities. Harvesting from the inner cheek is preferred to lower lip as it causes less post-operative discomfort and neurosensory deficits. Suturing is recommended for smaller ovoid grafts as it allows less painful closure without tension, while larger rectangular defects are best left to heal by secondary intention. OMG and MSGG transplantation is a viable alternative to replace conjunctiva and restore the ocular surface. The donor site is readily accessible and widely available in most patients, grafting is fast and cheap, and the same site may undergo repeated harvesting with few donor site complications.

An endothelialized urothelial cell-seeded tubular graft for urethral replacement

INTRODUCTION

Many efforts are used to improve surgical techniques and graft materials for urethral reconstruction. We developed an endothelialized tubular structure for urethral reconstruction.

METHODS

Two tubular models were created in vitro. Human fibroblasts were cultured for 4 weeks to form fibroblast sheets. Then, endothelial cells (ECs) were seeded on the fibroblast sheets and wrapped around a tubular support to form a cylinder for the endothelialized tubular urethral model (ET). No ECs were added in the standard tubular model (T). After 21 days of maturation, urothelial cells were seeded into the lumen of both models. Constructs were placed under perfusion in a bioreactor for 1 week. At several times, histology and immunohistochemistry were performed on grafted nude mice to evaluate the impact of ECs on vascularization.

RESULTS

Both models produced an extracellular matrix, without exogenous material, and developed a pseudostratified urothelium. Seven days after the graft, mouse red blood cells were present only in the outer layers in T model, but in the full thickness of ET model. After 14 days, erythrocytes were present in both models, but in a greater proportion in ET model. At day 28, both models were well-vascularized, with capillary-like structures in the whole thickness of the tubes.

CONCLUSION

Incorporating endothelial cells was associated with an earlier vascularization of the grafts, which could decrease the necrosis of the transplanted tissue. As those models can be elaborated with the patient's cells, this tubular urethral graft would be unique in its autologous property.

Inducing re-epithelialization in skin wound through cultured oral mucosal keratinocytes

Objectives

The purpose of this study was to investigate the wound healing effect of primary cultured oral mucosal keratinocytes (OMKs) and to assess their roles in skin wounds.

Materials and Methods

OMK labeled with BromodeoxyUridine were scattered onto 1.5×1.5 cm skin defects of adult female nude mice (OMK group, n=15). For the control, culture media were placed on the wound (control group, n=15). Mice in both groups were sacrificed at three days (n=5), one week (n=5), and two weeks (n=5), and histomorphometric and immunoblot analyses with keratinocyte growth factor (KGF), interleukin (IL)-6, and IL-1α antibody were performed for the biopsied wound specimen. To verify the effect of the cytokine, rhIL-1α was applied instead of OMK transplantation, and the OMK and control groups were compared with regard to re-epithelialization.

Results

Histomorphometric analyses demonstrated faster re-epithelialization in the graft group than in the control group at the third day, first week, and second week. Newly forming epithelium showed maintenance of the histological character of the skin epithelium. The graft group showed superior expression of KGF, IL-6, and IL-1α protein, compared with the control group. Similar faster re-epithelialization was observed after treatment with rhIL-1α instead of OMK transplantation.

Conclusion

We successfully confirmed that the graft of primary cultured OMKs promoted regeneration of skin defects. The mechanism of accelerated wound healing by primary cultured OMKs was attributed to inducement of cytokine expression as required for re-epithelialization.

Prepubertal follow-up after hypospadias repair with autologous in vitro cultured urothelial cells

AIM

To evaluate the long-term effects on hypospadias repair with cultured autologous urothelial cells.

METHODS

From 2000 to 2002, six patients with scrotal or perineal hypospadias and pronounced chordee were treated surgically with cultured autologous urothelial cell transplants. All patients were evaluated at 6-8 years postoperatively, that is, in the prepubertal period. The outcome was assessed with respect to cosmetic appearance, voiding function, urinary flow, artificial erection, urethroscopy and biopsies.

RESULTS

Median follow-up time was 7.25 years. Up to date, all patients present with a good cosmetic appearance. One of the boys prefers a sitting voiding position. Urinary flow curves are bell-shaped in all but one. All have straight erections, urethroscopy reveals an even, non-hair-bearing surface on the transplanted side and 2/6 present with urothelial cells in biopsies. Limitations of this follow-up study include a small group of patients and lack of controls. However, patients with severe hypospadias have high complication rates, and our results are equal or better than expected for the phenotype.

CONCLUSION

Tissue engineering for severe hypospadias repair can be performed in a safe manner. The method is feasible for treatment of a selected group of hypospadias, where pronounced chordee and shortage of preputial and penile skin complicates the creation of a neourethra.

Regenerative medicine in urology

The term 'regenerative medicine' encompasses strategies for restoring or renewing tissue or organ function by: (i) in vivo tissue repair by in-growth of host cells into an acellular natural or synthetic biomaterial, (ii) implantation of tissue 'engineered'in vitro by seeding cultured cells into a biomaterial scaffold, and (iii) therapeutic cloning and stem cell-based tissue regeneration. In this article, we review recent developments underpinning the emerging science of regenerative medicine and critically assess where successful implementation of novel regenerative medicine approaches into urology practice might genuinely transform the quality of life of affected individuals. We advocate the need for an evidence-based approach supported by strong science and clinical objectivity.

In vivo behavior of complete human oral mucosa equivalents: characterization in athymic mice

BACKGROUND AND OBJECTIVE

The interest in tissue engineering as a way to achieve repair of damaged body tissues has led to the carrying out of many studies whose results point to the potential effectiveness of these methods. In a previous study, we reported the obtaining of complete autologous oral mucosa equivalents (CAOMEs), characterized by oral immature keratinocytes and stem cells on an autologous plasma and fibroblast scaffold. The purpose of this study is to show their behavior in vivo, by using them as free grafts in experimental animals, and to demonstrate their potential capacity to regenerate oral mucosa.

MATERIAL AND METHODS

We engineered CAOMEs, as previously described. All CAOMEs thus obtained were used as free grafts in nu/nu mice. To assess their evolution in vivo, we studied their histological and immunohistochemical features by using AE1/AE3 pancytokeratin, the 5/6 cytokeratin pair, cytokeratin 13, laminin 5, collagen IV, vimentin, p-63 and Ki-67, at 7, 14 and 21 d.

RESULTS

The structure became progressively closer to that of oral mucosa samples. Cytokeratin 5/6 staining became increasingly intense in the basal and suprabasal layers, and cytokeratin 13 was exclusively positive in the superficial layers. The basal membrane was completed in 21 d. Vimentin showed a correct formation of the chorion. The increasingly positive staining of p-63 and Ki-67 indicated that the regeneration process was taking place.

CONCLUSION

The present study shows the potential regenerative capacity of the CAOMEs by their ability to reach maturity similar to that seen in oral mucosa.

Roles of Palatine Bone Denudation Repairing With Free Buccal or Palatal Mucosal Graft on Maxillary Growth

Most surgical repairs of cleft palate result in areas of bone denudation on lateral aspects of the hard palate. The present study was designed to investigate growth patterns of the maxilla following palatal bone denudation covering with free buccal or palatal mucosal graft in rabbits with surgically created defects simulating palatal bone denudation. Forty-five purebred New Zealand rabbits were used in this experiment. The animals were divided into 3 groups: 1 control group (left palatal bone denudation was not repaired and the right side was unoperated as a control) and 2 experimental groups (the right side of palatal bone denudation was covered with free buccal or palatal mucosal graft, respectively, and the left side was not repaired). Nineteen metric cranial variables were measured directly from the cleaned skulls. Direct cephalometric measurements were taken in the following dimensions: maxillary length, width and height, posterior facial width, and nasal deflection. Significant differences were noted between 2 sides of maxilla in all animals for the 19 cephalometric measurements. The cephalometric measurements of the right side in maxillary length, height, and width were significantly greater than those in the left side. There was no statistically significant difference between free buccal mucosal graft repaired group and free palatal mucosal graft repaired group for the cephalometric measurements. There was also no statistically significant difference for the cephalometric measurements between the 3 groups. The results of this study demonstrate that palatal bone denudation repaired by free buccal or palatal mucosal graft might prevent maxillary deformity following cleft palate surgery.

Autologous in vitro cultured urothelium in hypospadias repair

OBJECTIVE

To treat severe hypospadias with a transplant of autologous in vitro cultured urothelial cells on acellular dermis.

PATIENTS AND METHODS

During 2000-2002 six patients aged 14-44 months with severe hypospadias were treated surgically with autologous urothelial cell transplants. All were born with scrotal or perineal hypospadias and pronounced chordee. All patients were subjected to a two-staged procedure starting with repair of the chordee. Urothelial cell harvesting via bladder lavage was performed during the first operation. The neourethra was constructed by using a transplant with cultured urothelium in an on-lay fashion. Patients have been followed 3-5.5 years.

RESULTS

All six boys are voiding through their neourethra without straining and have no residual urine after micturition. Five patients are using a standing voiding position and present bell shaped, urinary flow curves. One developed a stricture treated conservatively with persisting good effect (after more than 5 years). Two developed a fistula requiring surgical correction that was uneventful. The last patient developed an obstruction in the proximal anastomosis that was treated with an internal urethrotomy. Cosmetic appearance is good in all cases with good parental satisfaction. Urethroscopy in all patients show a wide penile neourethra. Biopsies indicate a mucosal lining consisting of urothelial cells in three cases.

CONCLUSION

This technique is feasible for treatment of a selected group of hypospadias where pronounced chordee and shortage of preputial and penile skin complicates the creation of a neourethra. It may have other clinical implications including disorders such as bladder exstrophy and cloacal malformations, as well as mutilating traumatic injuries or cancer therapy.

Clinical application of tissue-engineered transplants. Part I: mucosa

OBJECTIVES

The study series aims at testing the feasibility of the clinical application of tissue-engineered oral mucosa. The preliminary results were gathered over a period varying from 6 months to 12 years depending on the surgical method.

METHODS

Tissue-engineered oral mucosa was used to cover defects in various surgical procedures like vestibuloplasty (n=42), freeing of the tongue (n=10), prelaminating the radial flap (n=5) and reconstruction of the urethra (n=16). In all interventions small samples of oral mucosa were harvested, cut into small pieces, resuspended in culture medium and seeded into a culture flask. Cultured keratinocytes were transferred onto membranes which then were used to cover mucosal defects in the oral cavity.

RESULTS

To gain a graft of 15 cm(2) size a mucosa biopsy of 4-8 mm(2) and 40 ml autologous patients serum is needed. Tissue-engineered oral mucosa was applied successfully in all four surgical methods. Six months after transplantation a regular epithelial layering with a histological delimitation of the stratum, epithelial crest and a strong basal membrane appeared. According to the reception site the tissue engineered oral mucosa differentiated in several ways.

CONCLUSION

Tissue-engineered oral mucosa fulfils the requirements for clinical routine. With view to healing time and outcome it does not appear to be superior to regular harvested oral mucosa transplants. Because of a smaller harvesting defect and primary wound closure at the actual operation site the patients' convenience is increased. Thus this method reduces morbidity and advances the quality of life.

Characteristics of iris and retinal pigment epithelial cells cultured on collagen type I membranes

PURPOSE

Transplantation of pigment epithelial cells is a promising treatment modality to repair retinal damage in age-related macular degeneration. For this purpose, it is necessary to establish cell culture techniques that allow acquisition of proper functional and morphological characteristics by the cells to be transplanted.

METHODS

Primary retinal pigment epithelial (RPE) and iris pigment epithelial (IPE) cells grown to confluence on collagen membranes were examined for morphology, adhesion, proliferation, apoptosis, as well as viability after ex vivo transplantation.

RESULTS

Pigment epithelial cells adhere, proliferate, form monolayers, acquire differentiated properties, and remain viable during transplantation to the subretinal space.

CONCLUSIONS

Pigment epithelial cells cultured on collagen membranes acquire differentiated characteristics and are amenable to be transplanted as cell monolayers.

Identification of Ghrelin in Human Saliva: Production by the Salivary Glands and Potential Role in Proliferation of Oral Keratinocytes

Background: We investigated whether ghrelin is present in human saliva, is produced by salivary glands, and physiologic consequences of these findings.

Methods: Expression of ghrelin and specific receptor mRNA was determined by PCR. Proteins were identified by immunoblotting and size-exclusion fast protein liquid chromatography (FPLC) with consecutive RIA. Specific RIAs were used for quantification of salivary total and bioactive ghrelin. Distribution of ghrelin was investigated by immunohistochemistry in cryosections of the salivary glands. The effect of ghrelin on incorporation of 5-bromo-2′-deoxyuridine as a measure of cell proliferation was investigated in primary oral keratinocytes.

Results:Ghrelin is produced by the salivary glands. The hormone was identified in saliva and glands by immunoblotting and by FPLC fractionation of saliva. Immunohistochemistry demonstrated ghrelin distribution in the salivary glands. The receptor was also produced by the glands and by oral keratinocytes and was shown to be functional. Comparison of total ghrelin values for healthy individuals (body mass index, 18–27 kg/m2) showed significantly lower concentrations in saliva than in serum (P <0.01). The correlation between both matrices was r2 = 0.56 (P <0.001) with a negative correlation to body mass index (r2 = 0.314; P <0.01). Bioactive acylated ghrelin was also present in saliva. Incubation of keratinocytes with ghrelin led to significantly increased cell proliferation (P <0.001). This effect could be completely suppressed by co-incubation with NOX-B11 (50 nmol/L), a novel specific inhibitor of acylated ghrelin.

Conclusions: Ghrelin in saliva is produced and released by salivary glands. The effect of ghrelin on oral cell proliferation adds to the pro-proliferative action of other salivary growth factors.

In vitro cultured autologous pre-confluent oral keratinocytes for experimental prefabrication of oral mucosa

The reconstruction of large defects after head and neck cancer resection often requires composite tissue transfer to replace a combination of bone, muscle and mucosa. Thus, tissue engineering techniques may be useful for oral mucosal reconstructive surgery to prefabricate mucosal tissue on the muscle flap in vivo, instead of using conventional skin-bearing composite flaps. The aim of this study was to investigate whether autogenous pre-confluent oral keratinocytes (PCOK) cultured in vitro can create mucosal coverage on muscle in vivo, in a single grafting procedure. In 30 Wistar rats, with a small piece of oral mucosa (2 mm x 5 mm), oral keratinocytes were isolated and then seeded on a hydrophilic PTFE membrane (n = 50) in serum-free culture condition. After 48 h, the membrane, together with the PCOK, was transplanted onto the gracilis muscle to fabricate a mucosal flap in vivo. The wound bed was closed primarily until the time of examination. Biopsies were carried out 1, 2, 3, and 4 weeks, respectively, after transplantation and were evaluated immunohistochemically (AE1/AE3 anti-pancytokeratin, cytokeratin 5/6, collagen IV, laminin, lectin-specific labeling of N-acetylglucosamine oligomeres of endothelial cells) with relation to the following criteria: (1) graft acceptance; (2) inflammatory signs; (3) structural changes and keratinocyte lining; (4) expression of basement membrane components; and (5) vascularization. Ninety-one percent of the grafts showed uniform epithelial layers. The mean number of reconstructed epithelial cell layers was 1.7, 2.0, 1.85 and 2.7 at 1, 2, 3 and 4 weeks, respectively after transplantation (P = 0.342). Collagen IV, laminin and lectin-specific capillaries developed between the neoepithelium and the underlying muscular layer. Only two specimens showed signs of infection 2 weeks after transplantation. In conclusion, this experiment demonstrated that PCOK grafts on muscle in vivo can achieve uniform multi-layered oral epithelial coverage in a short period of time. This technique may be a useful alternative tool for oropharyngeal reconstructive surgery and is also worth considering for further clinical studies.

Tissue-engineered buccal mucosa for substitution urethroplasty

OBJECTIVE

To develop tissue-engineered buccal mucosa (TEBM) for use in substitution urethroplasty, as urethral reconstruction is limited by the amount and type of tissue that is available for grafting, and BM has become the favoured tissue for use as a urethral substitute in the last decade.

MATERIALS AND METHODS

After enzymatic treatment of a small (0.5 cm) BM biopsy the epidermis and dermis were mechanically separated. Oral keratinocytes were isolated from the epidermis and oral fibroblasts from the dermis. These cells were expanded and applied to sterilized de-epidermized dermis (DED) to obtain a full-thickness TE oral mucosa. Horizontal migration of keratinocytes on the DED was assessed using a tetrazolium-blue (MTT) assay. The TEBM was assessed histologically after mechanical stressing in vitro using catheterization and meshing.

RESULTS

Histologically the TEBM closely resembled the native oral mucosa after culturing at an air-liquid interface for 2 weeks. The MTT assay showed good horizontal migration of keratinocytes on the DED. Serial histology revealed a gradually increasing thickness of the epidermis and remodelling of the dermis by the fibroblasts from day 1 to day 14. Despite subjecting the TEBM to mechanical stress the integrity of the epidermal-dermal junction was maintained.

CONCLUSIONS

We report the successful culture of full-thickness TEBM for substitution urethroplasty, which is robust and suitable for clinical use.

Making bone: implant insertion into tissue-engineered bone for maxillary sinus floor augmentation-a preliminary report

Autologous, allogenic and alloplastic materials for bony reconstruction in the cranio-maxillofacial area have many drawbacks thus stimulating the on-going search for new (bio-)materials. Whereas cultivated skin and mucosa are already in clinical routine use in head and neck reconstruction, so far there has been no successful clinical application to the best of our knowledge of periosteum-derived, tissue-engineered bone for augmentation of the edentulous posterior maxilla. In a pilot study, augmentation of the posterior maxilla was carried out using a bone matrix derived from mandibular periosteal cells on a polymer fleece. This paper demonstrates fabrication of the matrix, clinical application, and the histological results in two patients. The results suggest that periosteum-derived osteoblasts on a suitable matrix form lamellar bone within 4 months which allows reliable implant insertion.

Easy tissue expansion of prelaminated mucosa-lined flaps for cheek reconstruction in a canine model

In head and neck reconstruction, there is sometimes the need for a skin flap lined with mucosa. The object of this study was to determine whether small pieces of mucosa grafted onto the undersurface of a skin flap can be expanded in a reasonable time to provide the material required to reconstruct a full-thickness cheek defect as a free flap. The study consisted of two phases: prelamination and expansion of the flap, and vascularized free-tissue transfer of the flap. Six adult mongrel dogs were used. First, a 5 x 10-cm flap based on the saphenous vessels was elevated on the lower leg, and then four 1 x 2-cm pieces of mucosa harvested from the tongue were grafted onto the undersurface of the flap. A tissue expander (5 x 10 cm) was then placed under the flap, and the incision was closed primarily. The expanders were initially filled with just enough normal saline to obliterate dead space immediately after surgery. The expansion was continued twice weekly for 3 weeks until sufficient expansion was obtained. Two of six flaps were followed for an additional 6 weeks after the 3-week expansion period to observe whether additional mucosa could be obtained. After measurement of the mucosal area, each flap was transferred as free flap to reconstruct an iatrogenic cheek defect. The increase of mucosal surface area was compared with the original graft, and differences were analyzed using the paired t test. All flaps were successfully expanded without any complications. Histologic evaluation revealed that grafted mucosa took well without evidence of graft necrosis, and the intergraft area was covered with histiocytes. Angiography revealed well-defined vascular structures covering the entire area of the flap. The new mucosal area (23.5 +/- 2.4 cm2) was significantly larger than the original mucosal graft (8.7 +/- 0.9 cm2) (p < 0.001). The net increase of the mucosal area was 172.9 +/- 32.4 percent. The increase of mucosal area in two flaps, following a 6-week consolidation period after 3 weeks of expansion, was only slightly greater (25.9 +/- 1.3 cm2) than those without the consolidation period (22.3 +/- 1.8 cm2). This increase of the mucosal area appears to be related to the amount of expansion, and not to the length of the consolidation period. The flaps were successfully transferred as free flaps to reconstruct the full-thickness cheek defects without major complications. Although a staged operation to allow flaps to mature is needed, the present procedure has the advantages of providing a mucosa-lined flap and allowing primary closure of the donor site. The authors conclude that expansion of this flap has great potential in reconstructive surgery.

Prelaminating the fascial radial forearm flap by using tissue-engineered mucosa: improvement of donor and recipient sites

In reconstructive surgery, prelamination of free flaps using split-thickness skin is an established technique to avoid the creation of a considerable defect at the donor site, for example, in the case of a radial forearm flap. For oral and maxillofacial surgery, this technique is less than optimal for the recipient site because the transferred skin is inadequate to form a lining in the oral cavity. To create mucosa-lined free flaps, prelamination using pieces of split-thickness mucosa has been performed. However, the availability of donor sites for harvesting mucosa is limited. The present study combines a tissue-engineering technique with free flap surgery to create mucosa-lined flaps with the intention of improving the tissue quality at the recipient site and decreasing donor-site morbidity. On five patients undergoing resection of squamous cell carcinoma of the oral cavity, the radial forearm flap was prelaminated with a tissue-engineered mucosa graft to reconstruct intraoral defects. Using 10 x 5 mm biopsies of healthy mucosa, keratinocytes were cultured for 12 days and seeded onto collagen membranes (4.5 x 9 cm). After 3 days, the mucosal keratinocyte collagen membrane was implanted subcutaneously at the left or right lower forearm to prelaminate the fascial radial forearm flap. One week later, resection of the squamous cell carcinoma was performed, and the free fascial radial forearm flap pre- laminated with tissue-engineered mucosa was transplanted into the defect and was microvascularly anastomosed. Resection defects up to a size of 5 x 8 cm were covered. In four patients, the graft healed without complications. In one patient, an abscess developed in the resection cavity without jeopardizing the flap. During the postoperative healing period, the membrane detached and a vulnerable pale-pink, glassy hyperproliferative wound surface was observed. This surface developed into normal-appearing healthy mucosa after 3 to 4 weeks. In the postoperative follow-up period, such functions as mouth opening and closing and speech attested to the success of the tissue-engineering technique for flap prelamination.