Biomedical subjects

Anthony Atala

Publications and source records attributed to Anthony Atala.

82 records · Page 5Linked to original sources

PubMed2002

Urethral mobilization and advancement for midshaft to distal hypospadias.

PURPOSE: A urethral mobilization and advancement technique for repairing glanular, subglanular and midshaft hypospadias with or without chordee was developed, and has been used for more than 6 years. A brief description of the procedure and the results are presented. MATERIALS AND METHODS: From 1995 to 2001, 73 boys 4 months to 12 years old underwent repair of glanular (14), subglanular (38) and midshaft (20) hypospadias. Chordee was present in 37 boys. Upon initiating the surgery, a circumcising incision was made proximal to the urethral orifice. The ventral glanular mucosa was preserved. The penile skin was degloved and any chordee was corrected. The meatus was circumscribed and the urethra was mobilized proximally until a 4 to 5:1 ratio was achieved between the length of the mobilized urethra and the initial distance measured from the meatus to the distal margin of the glanular groove. The ventral glans was incised deeply to the corpora cavernosa and the glans wings were mobilized laterally. The urethral meatus was advanced and sutured to the distal glans. The glans wings were approximated over the urethra. The glanular mucosal wings were approximated ventrally, and the skin was resected and closed in the usual fashion. A urethral catheter was left overnight. RESULTS: Followup ranged from 6 months to more than 6 years. None of the patients had a urethrocutaneous fistula or meatal stenosis. There were no episodes of new, persistent or recurrent chordee. Two patients had meatal retraction wherein the urethra migrated proximally but still within the glans. Only 1 of these patients required a second procedure. One patient had a hematoma that resolved spontaneously. CONCLUSIONS: The hypospadias technique described, which uses wide urethral and glanular mobilization and advancement, can be useful for repair of midshaft to distal hypospadias with or without chordee with minimal complications and excellent cosmetic results.

Child↗

PubMed2002

Urethral replacement using cell seeded tubularized collagen matrices.

PURPOSE: Acellular collagen matrices derived from bladder submucosa have been used successfully as an off-the-shelf biomaterial for urethral replacement, experimentally and clinically in an onlay fashion. We investigated whether collagen matrices, either alone or with autologous cells, could be used for tubularized urethral replacement. MATERIALS AND METHODS: Acellular collagen matrices were processed and tubularized. Ten rabbits underwent an open bladder biopsy with subsequent cell expansion. Autologous bladder cells were grown and seeded onto the pre-configured tubular matrices. A 1 cm. long urethral segment was excised in 24 male rabbits. Urethroplasty was performed with the tubularized collagen matrices seeded with cells in 12 animals and without cells in 12. Serial urethrography was performed preoperatively and at 1, 2, 3 and 6 months postoperatively. Retrieved urethras were analyzed grossly, histologically, immunocytochemically and with Western blots. Contractility and the presence of neurotransmitter receptors were confirmed with organ bath studies. RESULTS: Serial urethrography confirmed the maintenance of a wide urethral caliber without any signs of strictures in animals implanted with the cell seeded matrices. The urethral segments replaced with the collagen scaffolds without cells demonstrated strictures and graft collapse at all time points. The implanted cell seeded matrices had a normal urethral architecture by 1 month, consisting of a transitional cell layer surrounded by muscle cell fiber bundles with increasing cellular organization with time. Epithelial and smooth muscle phenotypes were confirmed immunocytochemically and with Western blot analyses using pancytokeratins AE1/AE3 and smooth muscle specific alpha-actin antibodies. Formation of a transitional cell layer was confirmed in the matrices implanted without cells but only scant unorganized muscle fiber bundles were present, mostly at the anastomotic sites. Organ bath studies demonstrated the capacity for contractility along with cholinergic and adrenergic specific receptors in the tissue engineered scaffolds compared to controls. CONCLUSIONS: These results show that collagen matrices seeded with cells form normal urethral tissue can be used for tubularized replacement, whereas tubularized collagen matrices alone without cells lead to poor tissue formation and strictures. The collagen matrices seeded with cells may offer a useful alternative in the future for patients requiring a tubularized urethral segment replacement.

Animals↗

PubMed2002

Engineering of human cartilage rods: potential application for penile prostheses.

PURPOSE: Natural penile prostheses created from the patient's own cells may eliminate the biocompatibility risks associated with artificial prostheses. We previously demonstrated that autologous cartilaginous rods could be created in animal corpus cavernosum as penile prostheses in situ by transplanting autologous chondrocytes on biodegradable polymer scaffolds. In the present study we investigated the possibility of engineering human cartilage rods for potential use as penile prostheses. MATERIALS AND METHODS: Chondrocytes isolated from human ear were seeded on rod shaped biodegradable polymer scaffolds (1.2 cm. in diameter, 6.0 cm. long). The seeded scaffolds were maintained in stirred bioreactors for 1 month. Subsequently, the seeded scaffolds were implanted subcutaneously into athymic rats. The specimens were retrieved 2 months after implantation, and histological, structural and mechanical properties were analyzed. The mechanical properties of the engineered prostheses were compared to those of silicone prostheses. RESULTS: Human chondrocytes seeded onto polymer scaffolds formed milk-white cartilaginous rods of the same size as the initial implants. Histological analyses using hematoxylin and eosin, toluidine blue and alcian blue showed mature and well-formed chrondrocytes in the retrieved implants. The engineered human cartilaginous rods were flexible, elastic and able to withstand high degrees of compressive forces. The mechanical properties were comparable to those of commercially available silicone prostheses. CONCLUSIONS: Transplantation of chrondrocytes isolated from human ear on polymer scaffolds resulted in the formation of human cartilage rods with the appropriate mechanical properties required for use as penile prostheses. This study demonstrates the feasibility of creating human cartilage rods with a large dimension. This technology may be useful for patients who need penile reconstruction.

Biomechanical Phenomena↗

PubMed2002

Phenotypic and functional characterization of in vivo tissue engineered smooth muscle from normal and pathological bladders.

PURPOSE: The engineering of bladder tissue involves obtaining a biopsy from a host, expanding the cells, seeding them onto a matrix and implanting the cell-matrix composite back into the host. Clinically, cells used for these techniques may be harvested from abnormal bladders. It is not known whether abnormal bladder cells may be engineered into functionally normal tissue. We investigated the phenotypic and functional characteristics of tissue engineered bladder smooth muscle derived from patients with functionally normal bladders and functionally abnormal exstrophic and neuropathic bladders. MATERIALS AND METHODS: Human smooth muscle cells derived from functionally normal bladders, exstrophic bladders and neurogenic bladders were grown, expanded and seeded onto polymer scaffolds. Sixteen cell seeded scaffolds were analyzed in vitro and 40 cell seeded scaffolds were implanted in athymic mice. The tissue engineered constructs were retrieved and analyzed at 2 weeks and 2 months. The scaffolds were evaluated immunocytochemically, histologically, with organ bath studies and with Western blot analyses. RESULTS: Human bladder cells showed similar expression of smooth muscle marker proteins (alpha-actin and myosin) in vitro and after 2 months in vivo, regardless of their origin. All scaffolds showed similar muscle formation in vivo. The cell seeded scaffolds demonstrated the typical "contraction-relaxation" response to supramaximal electrical field and carbachol stimulation. There were no statistical differences among the experimental groups (normal, exstrophic, neurogenic). CONCLUSIONS: Tissue engineered muscle from normal and diseased bladders retain their phenotype in vitro and after implantation in vivo. The cells exhibited the same degree of contractility to electrical and chemical stimulation regardless of their origin. These results suggest that there are no phenotypic or functional differences between muscle cells obtained from urodynamically normal or pathological bladders, and that bladder muscle cells, regardless of their origin, may have the potential to be engineered into normal bladder tissues.

Actins↗

PubMed2002

Autologous penile corpora cavernosa replacement using tissue engineering techniques.

PURPOSE: The availability of engineered tissues would be beneficial to patients undergoing penile reconstruction. We explored the possibility of replacing an entire cross-sectional segment of both corporal bodies with autologous engineered tissues in rabbits, and investigated the structural and functional integrity of the neo-corpora. MATERIALS AND METHODS: Acellular corporal collagen matrices were obtained from donor rabbit penis. Autologous corpus cavernosal smooth muscle and endothelial cells were harvested, expanded and seeded on the matrices. An entire cross-sectional segment of protruding rabbit phallus was excised, leaving the urethra intact. A total of 26 matrices, including 18 seeded with cells and 8 without cells, were interposed into the excised corporal space. An additional 4 rabbits that did not undergo surgical intervention served as normal controls. Functional and structural parameters (cavernosography, cavernosometry, mating behavior and sperm ejaculation) were followed for 6 months. Gross examination, and histochemical, immunocytochemical and Western blot analyses were performed at 3 and 6 months after implantation. RESULTS: The experimental corporal bodies demonstrated intact structural integrity on cavernosography and decreased maximal intracavernosal pressures on cavernosometry compared to normal controls. Mating activity in animals with engineered corpora normalized by 3 months postoperatively. The presence of sperm was confirmed during mating and was present in all rabbits with engineered corpora but in only 2 with the matrix alone. Histologically sinusoidal spaces and walls lined with endothelial and smooth muscle cells were observed in the engineered grafts. Each cell type was identified immunocytochemically. Grafts without cells contained fibrotic tissue and calcifications with sparse corporal elements. Western blot analysis of engineered grafts showed nitric oxide synthase activity similar to normal controls. CONCLUSIONS: Autologous corpus cavernosal smooth muscle and endothelial cells seeded on collagen matrices can form corpora cavernosa tissue structures in a rabbit model. Engineered corpora cavernosa achieved adequate structural and functional parameters. This technology may be applicable to patients who require additional tissue for phallic reconstruction.

Animals↗

PubMed2002

In vitro systems for tissue engineering.

Tissue engineering, by necessity, encompasses a wide array of experimental directions and scientific disciplines. In vitro tissue engineering involves the manipulation of cells in vitro, prior to implantation into the in vivo environment. In contrast, in vivo tissue engineering relies on the body's natural ability to regenerate over non-cell-seeded biomaterials. Cells, biomaterials, and controlled incubation conditions all play important roles in the construction and use of modern in vitro systems for tissue engineering. Gene delivery is also an important factor for controlling or supporting the function of engineered cells both in vitro and post implantation, where appropriate. In this review, systems involved in the context of in vitro tissue engineering are addressed, including bioreactors, cell-seeded constructs, cell encapsulation, and gene delivery. Emphasis is placed upon investigations that are more directly linked to the treatment of clinical conditions.

Animals↗

PubMed2002

Testicular volume: comparison of orchidometer and US measurements in dogs.

PURPOSE: To compare the accuracy and precision of orchidometer and ultrasonographic (US) measurements of testicular volume in a canine model. MATERIALS AND METHODS: Volume measurements of 18 canine testes were obtained by using Prader and Rochester orchidometers. Testes were scanned with two linear-array US transducers with imaging frequencies of 6-13 MHz and 5-10 MHz. For each transducer, testicular volumes were calculated by using three formulas: length (L) x width (W) x height (H) x 0.52, L x W(2) x 0.52, and L x W x H x 0.71. Testes were weighed following bilateral orchiectomies. True testicular volume was determined by using the formula volume = weight/density. Paired t tests were used to assess whether mean measurement biases differed significantly from zero. The relationship between true and measured volume was evaluated with a linear regression model. RESULTS: US volume measurements demonstrated lower variability and better linear fit compared with orchidometry (R(2) = 0.75-0.90 vs R(2) = 0.14-0.38). The formula L x W x H x 0.71 had the smallest mean bias relative to true volume with use of either transducer over the entire volume range. CONCLUSION: US methods of testicular volume measurement are more accurate and precise than orchidometry. The formula L x W x H x 0.71 provides a superior estimate of testicular volume and should be used in clinical practice.

Animals↗

PubMed2002

In vitro biocompatibility evaluation of naturally derived and synthetic biomaterials using normal human bladder smooth muscle cells.

PURPOSE: Tissue engineering of the urinary tract often requires the use of various biomaterials. Adequate biomaterial biocompatibility is necessary for successful urinary reconstruction. In this study using a primary normal human bladder smooth muscle cell culture system we evaluated the in vitro biocompatibility of a number of naturally derived biomaterials, including bladder submucosa, small intestinal submucosa, collagen and alginate, and polymeric biomaterials, including polyglycolic acid, poly(L-lactic acid) and poly(lactic-co-glycolic acid, which have been used for urinary reconstruction experimentally or clinically. MATERIALS AND METHODS: To determine the cytotoxic and bioactive effects of bladder submucosa, small intestinal submucosa, collagen, alginate, polyglycolic acid, poly(L-lactic acid) and poly(lactic-co-glycolic acid) we measured cell viability, metabolic activity, apoptotic properties and DNA synthesis activity with 4 types of assays, namely Neutral Red (Sigma Chemical Co., St. Louis, Missouri), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (Sigma Chemical Co.), apoptotic activity and tritiated thymidine incorporation (Dupont NEN, Boston, Massachusetts) assays. Normal human bladder smooth muscle cells were cultured with the extracts of the biomaterials or cultured in direct contact with the biomaterials. RESULTS: All naturally derived and synthetic biomaterials tested in this study except alginate exhibited nontoxic and bioactive effects on human bladder smooth muscle cells (HBSMCs) in vitro, as indicated by the 4 types of biocompatibility assays using the extract and direct contact methods. Cell viability, apoptotic properties, metabolic activity and DNA synthesis activity of HBSMCs cultured with the extracts of the biomaterials or cultured in direct contact with the biomaterials were not significantly different from those of negative controls (fresh medium with no extracts or tissue culture plates without biomaterials). CONCLUSIONS: All naturally derived and synthetic biomaterials tested in this study except alginate exhibited nontoxic and bioactive effects on HBSMCs in vitro. This normal primary human bladder smooth muscle cell culture model is suitable for in vitro biocompatibility assessment. It provides information on cell-biomaterial interactions and on the ability of biomaterials to support bioactive cell functions.

Biocompatible Materials↗

PubMed2002

A system for the enhancement of adenovirus mediated gene transfer to uro-epithelium.

PURPOSE: Recombinant adenovirus has been used widely as an in vivo gene transfer vector, although its transfection efficiency in bladder tissue is limited. Several studies have indicated that the bladder surface glycosaminoglycan (GAG) layer functions as a nonspecific anti-adherence factor and possibly as a first line anti-infection defense mechanism. We determined whether recombinant adenovirus mediated gene transfer could be enhanced in intact bladders by HCl pretreatment and by alterations in the GAG layer. MATERIALS AND METHODS: In vitro viral transfection efficiencies with and without the GAG analog pentosan polysulfate (Sigma Chemical Co., St. Louis, Missouri) were determined in bladder muscle and urothelial cells. Immunocytochemical studies and Western blot analysis were performed to determine whether urothelial cells possessed the Coxsackievirus and adenovirus receptor. Rat bladders were intravesically pretreated with HCl at various concentrations and for various periods. After 60 mM. HCl pretreatment for 10 minutes 2 x 109 pfu of recombinant adenovirus carrying the Escherichia coli LacZ gene were intravesically instilled into the bladders. RESULTS: Adenoviral infection of urothelial cells was significantly reduced in the presence of pentosan polysulfate in vitro. Coxsackievirus and adenovirus receptor expression was detected in urothelial cells in vivo and in vitro. Bladders pretreated with HCl resulted in an alteration of the bladder GAG layers. After intravesical gene instillation reporter gene analyses using X-5-bromo-4-chloro-3-inodolyl beta-D-galactopyranoside (Sigma Chemical Co.) showed approximately 80% urothelial cell transfection efficiency in bladders pretreated with HCl. However, less than 10% of the urothelial cells expressed the transfected gene in control HCl untreated bladders. CONCLUSIONS: Primary urothelial cells and bladder carcinoma cells can be efficiently transfected using an adenoviral vector with similar infectivity. In vitro viral infection shows that the efficiency of adenoviral transfection is significantly reduced in the presence of pentosan polysulfate, a GAG analog. Adenoviral mediated gene transfer to bladder urothelium is enhanced by HCl pretreatment.

Adenoviridae↗

PubMed1977

Morphometric and dynamic studies of bone changes in hyperthyroidism.

Bone biopsies were performed after tetracycline double-labelling by transfixing the right iliac crest in forty hyperthyroid patients. The bone changes in cortical and trabecular bone were determined by simple measurement and point counting on decalcified and undecalcified stained sections. A slight decrease in the amount of cancellous bone was found. The mean cortical width was normal. The amount of osteoid and the length of the osteoid seams were increased, whereas the mean width of osteoid seams was decreased. The cortical osteoclastic activity and porosity were markedly increased. The trabecular osteoclasic activity was moderately increased and the mean size of periosteocytic lacunae was slightly increased. The calcification rate in cancellous bone was increased as were the active calcification surfaces (tetracycline-labelled). The osteoclastic activity in cortical bone was positively correlated to the free thyroxine index and to the urinary calcium and phosphorus excretion. The findings indicate that the bone changes in hyperthyroidism are specific and that thyroid hormone(s) stimulates both bone formation and resorption followed by increased porosity in cortical bone and by mobilization of bone mineral.

Adolescent↗