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J J Yoo

Publications and source records attributed to J J Yoo.

At least 19 recordsLinked to original sources
PubMed2006

The role of preoperative bone scan for determining the treatment method for femoral neck fracture.

To evaluate the role of preoperative bone scintigraphy in determining the operative treatment method for femoral neck fracture, we reviewed the data of 83 patients who underwent preoperative bone scanning after femoral neck fracture. Fractures were classified using the Garden staging system. Radioisotope uptake in femoral heads was evaluated visually. Of 28 patients with Garden stage I or II, radioactivity of the femoral head was normal in 26, partially reduced in one, and generally reduced in one patient. Twenty-seven patients were treated by closed reduction and multiple pinning, and one patient was treated by bipolar hemiarthroplasty. Of 55 patients with Garden stage III or IV, femoral-head radioactivity was normal in three, partially reduced in seven and generally reduced in 45 patients. Fifty-four patients were treated by bipolar hemiarthroplasty or total hip arthroplasty, and one patient was treated by closed reduction and multiple pinning. In only one of the 83 cases was the operative method changed because of bone scan findings. Isotope uptake of the femoral head after femoral neck fracture generally corresponded with the degree of fracture displacement. Preoperative bone scans appear to have no significant role to play in determining the operative treatment method for femoral neck fracture.

Adolescent↗
PubMed2006

The effect of thrombin on ACL fibroblast interactions with collagen hydrogels.

Premature loss of provisional scaffold formation has been identified as one of the factors responsible for poor healing of intraarticular tissues. To address this deficiency, substitute provisional scaffolds are being developed. The function of these scaffolds can be enhanced by the addition of specific extracellular matrix proteins. In this study, it was hypothesized that the addition of thrombin to a provisional scaffold material would result in increases in cell proliferation, collagen production, and cell migration within the scaffold. These three parameters are thought to be critical components of wound healing. Gels containing fibrin and collagen supplemented with either 0, 10.5, 21, or 42 U/mL of thrombin were placed in contact with explants of tissue from the anterior cruciate ligament. The addition of thrombin stimulated cell migration at low concentrations and impaired migration at higher concentrations, and had no significant effect on cell proliferation or collagen production. The use of all concentrations of thrombin resulted in mechanically weaker gels. Thus, the use of thrombin to optimize a collagen-platelet rich plasma (PRP) provisional scaffold must be done with caution, and use of high concentrations of thrombin (>42 IU/mL) should be avoided specifically in situations where gel strength or cell ingrowth is important. Use of low concentrations of thrombin (10.5 IU/mL) may be beneficial in applications where a faster set time and enhanced cell migration are desirable and the gel mechanical strength is of secondary importance.

Animals↗
PubMed2002

In vitro release of vancomycin from vancomycin-loaded blood coated demineralised bone.

In vitro and in vivo studies have demonstrated the possibility that cancellous bone could be used as a carrier of antibiotics for local delivery. However, the release of antibiotics from the loaded cancellous bone is too rapid and uncertain. We hypothesised that demineralisation of cancellous bone would increase the amount of antibiotic adsorbed, and coating of the freeze-dried antibiotic-impregnated cancellous bone with bio-compatible material would prolong antibiotic release. Bovine cancellous bone blocks of equal size were demineralised using a 0.5 N HCl solution and loaded with vancomycin solution under vacuum. The loaded bone blocks were then freeze-dried. To obtain a bio-compatible coating, the vancomycin-impregnated bone blocks were soaked in fresh human venous blood for 3 h. The release of impregnated antibiotic from the bone blocks was evaluated in phosphate-buffered saline and foetal bovine serum. It was found that significantly larger amounts of vancomycin were adsorbed into the demineralised bone blocks than into the un-demineralised blocks. The blood coating was found to increase the duration of vancomycin release from the blocks. With demineralisation and blood coating, the blocks eluted vancomycin higher than therapeutic concentration for a 5-week period.

Absorption↗
PubMed2001

Tissue engineered stents created from chondrocytes.

PURPOSE: Trauma, operations or instrumentation of the urethra or ureter may lead to stricture disease. The use of a natural urethral stent made of autologous tissue would be advantageous due to its biocompatibility. In this study we investigated the feasibility of engineering cartilage stents in vitro and in vivo. MATERIALS AND METHODS: We fabricated 40 cylinders 10 mm. long with an inner and outer diameter of 5 and 9 mm., respectively, from polyglycolic acid mesh coated with 50:50 polylactic-co-glycolic acid. Chondrocytes isolated from bovine shoulders were seeded onto the tubular polymer scaffolds at a seeding density of 60 x 106 cells per ml. Scanning electron microscopy was performed to determine the even distribution of chondrocytes throughout the polymer scaffolds. We implanted 20 cylinders under the skin of nude mice and 20 were cultured in stirred bio-reactors. Cytological characteristics, collagen content and mechanical durability were evaluated 4 and 10 weeks after cell seeding. RESULTS: Gross examination of the engineered stents showed the solid, glistening appearance of cartilaginous tissue. Cytological analyses with hematoxylin and eosin, trichrome, alcian blue and safranin O confirmed cartilage, and the deposition of collagen and glycosaminoglycan in each group. Increased deposition of collagen and glycosaminoglycan was observed in the stents created in vivo. Biomechanical testing demonstrated that the cartilaginous cylinders in each group were readily elastic and withstood high degrees of pressure. CONCLUSIONS: This study demonstrates the feasibility of creating cartilaginous stents in vitro and in vivo using chondrocyte seeded polymer matrices. This technology may be useful clinically for stricture disease in the genitourinary tract.

Animals↗
PubMed2000

Tissue-engineering applications for phallic reconstruction.

Pathologic penile conditions often require reconstructive surgery. Due to the limited amount of autologous tissues available for reconstruction, other tissue substitutes have been used. Phallic reconstruction using engineered autologous genital tissue, i.e., tissue derived from the patient's own cells, may be preferable. In this article we describe tissue-engineering approaches that may be applicable to genital reconstruction.

Biocompatible Materials↗
PubMed2000

Experimental and clinical experience using tissue regeneration for urethral reconstruction.

Various urethral conditions often require additional tissue for reconstruction. Although several innovative tissues have been proposed for possible use as free grafts for urethral repair, all have specific advantages and disadvantages. The use of these tissues may be associated with additional procedures for graft retrieval, prolonged hospitalization, and donor-site morbidity. For these reasons, alternate materials have been sought for urethral repair. Our laboratory has developed an acellular collagen matrix that has shown adequate urothelial-cell epithelialization and urethral-tissue regeneration both experimentally and clinically. After a 3-year follow-up period, all patients who have had their urethras reconstructed with the acellular matrix are doing well, showing no clinical change from their immediate postoperative results. Other acellular materials may soon be tried clinically. Long-term studies need to be conducted before any of these materials can be accepted for routine use in urethral reconstructive procedures.

Animals↗
PubMed2000

Renal therapy using tissue-engineered constructs and gene delivery.

Currently available renal replacement therapies are not optimal for most patients. In addition to the inherent shortage of transplant organs, significant complications are associated with renal transplantation and immunosuppressive therapy. Dialysis neglects the resorptive, homeostatic, metabolic, and endocrinologic functions of the kidney and only partially replaces its filtration properties, resulting in morbidity and mortality. Application of tissue-engineering techniques may improve many aspects of renal function replacement. Identification of the growth factors capable of directing tissue development and of the technique to be used for their delivery would aid in the engineering of human tissue. The combination of tissue-engineering strategies with gene therapy might allow the transfection of diseased tissues with designated cDNA to eliminate inherent or acquired defects. Devices that have been targeted at replacing a single aspect of renal function, in addition to three-dimensional renal units that are capable of excreting urine-like solutes, have been used experimentally. Combination of these strategies may allow the formation of tissue-engineered kidneys in the future.

Biocompatible Materials↗
PubMed2000

Defunctionalized bladders: effects before and after refunctionalization in an animal model.

PURPOSE: Bladder behavior after refunctionalization is usually unpredictable. We comparatively analyze various aspects of bladder defunctionalization and subsequent refunctionalization using an animal model. MATERIALS AND METHODS: A total of 18 rabbits were divided equally into 3 groups. Animals in group 1 underwent 2 successive surgical procedures, including bladder division and reattachment. Bladder division was performed by hemisecting the bladder from dome to trigone into a functioning and nonfunctioning chamber. Bladder reattachment was achieved by reanastomosing both hemibladders. Group 2 animals underwent sham operations, and group 3 animals were age matched normal controls. Serial urodynamic studies and fluoroscopic cystograms were performed in all animals. Gross, histochemical (hematoxylin and eosin, Masson's trichrome and Sirius red) and immunocytochemical (alpha-actin, collagen I and III) analyses, collagen content determination and organ bath studies were performed. RESULTS: The defunctionalized hemibladders demonstrated lower wet weight, capacity and compliance compared to the functional contralateral and normal control bladders. Refunctionalization of the bladders resulted in a progressive recovery of capacity and compliance with time. The bladder contractile response and connective tissue-to-muscle ratio were abnormal in the defunctionalized segments but normalized after bladder refunctionalization. CONCLUSIONS: Defunctionalization results in remarkable alterations in bladder growth, capacity, compliance and distribution of connective tissue. However, these bladders demonstrate an innate capacity to recover from these alterations following refunctionalization.

Animals↗
PubMed2000

Tissue engineering applications in the genitourinary tract system.

The concept of cell transplantation using tissue engineering techniques has provided numerous possibilities in the area of urologic tissue reconstruction. Tissue engineering applications in the genitourinary tract system have been investigated in almost every tissue in order to improve, restore and replace existing tissue function. Although most reconstructive efforts still remain in the experimental stage, several technologies have been transferred to the bedside with satisfactory outcome. In this article, we describe tissue engineering approaches attempted in the genitourinary system for reconstruction.

Animals↗
PubMed1999

Reconstitution of human corporal smooth muscle and endothelial cells in vivo.

PURPOSE: The availability of autologous erectile tissue composed of corporal smooth muscle and endothelial cells would be beneficial in patients undergoing penile reconstruction. We previously showed that cultured cavernous cells seeded on polymer scaffolds form corporal muscle when implanted in vivo. However, to reconstruct corporal tissue endothelial and corporal muscle cells are necessary. In this study we investigated the possibility of developing tissue composed of corporal cells in vivo by combining smooth muscle and endothelial cells. MATERIALS AND METHODS: Human corporal smooth muscle and endothelial cells were seeded on biodegradable polyglycolic acid polymer scaffolds at concentrations of 20 x 10(6) and 10 x 10(6) cells per cm3, respectively. A total of 60 polymer scaffolds seeded with cells and 20 control polymers without cells were implanted in the subcutaneous space of 20 athymic mice. Mice were sacrificed 1, 3, 5, 7, 14, 21, 28 and 42 days, respectively, after implantation. Immunocytochemical and histochemical analyses were performed with antifactor VIII, antipancytokeratins and anti-alpha actin antibodies. RESULTS: Histologically the retrieved polymers seeded with corporal smooth muscle and endothelial cells showed the formation of multilayered smooth muscle strips adjacent to endothelial cells 7 days after implantation. Increased organization of the smooth muscle tissue and accumulation of endothelium lining the luminal structures were evident by 14 days. A well organized tissue construct was noted 28 and 42 days after implantation. There was no evidence of tissue formation in controls. Immunocytochemical analysis using antifactor VIII to identify native vasculature only and antipancytokeratins to identify ECV 304 endothelial cells only distinguished the origin of the vascular structures in each construct. Anti-alpha-actin confirmed the smooth muscle phenotype. CONCLUSIONS: Human corporal smooth muscle and endothelial cells seeded on biodegradable polymer scaffolds formed vascularized corpus cavernosum muscle when implanted in vivo. To our knowledge this is the first demonstration in tissue engineering in which capillary formation was facilitated by the addition of endothelial cells in composite tissue in vivo.

Animals↗
PubMed1999

Direct in vivo gene transfer to urological organs.

PURPOSE: Patients with urological disorders may benefit from gene based therapy. We investigated the feasibility of delivering exogenous genes into urological tissues in vivo using direct in vivo electrotransfection. MATERIALS AND METHODS: Gene transfer to rat kidneys, testes and bladders was accomplished via direct local injection of pGL3/luciferase and beta-galactosidase reporter gene constructs, followed by an electrical pulse ranging from 55 to 115 msec at 100 V. Direct injection of deoxyribonucleic acid without an electrical pulse served as the control. The transfected and nontransfected organs were retrieved and analyzed by luciferase activity assay, histochemical and immunocytochemical staining for beta-galactosidase, and reverse transcription polymerase chain reaction with primers specific for beta-galactosidase messenger ribonucleic acid. RESULTS: There was significant luciferase activity 1, 3 and 5 days after direct in vivo electrotransfection in kidneys and testes, and after 3, 5, 7 and 10 days in bladders. Positive beta-galactosidase enzyme activity and beta-galactosidase immunoreactivity were observed in the transfected renal tubular cells, testicular interstitial and germ cells, and uroepithelial bladder layer. Reverse transcription-polymerase chain reaction products of the transfected organs were noted, indicating the successful transcription of messenger ribonucleic acid. CONCLUSIONS: This study demonstrates that direct in vivo electrotransfection is a feasible method of transient gene delivery into intact urological organs. Its apparent safety and relative simplicity suggest that direct in vivo electrotransfection may be useful clinically.

Animals↗
PubMed1999

Autologous engineered cartilage rods for penile reconstruction.

PURPOSE: Conditions such as inadequate and ambiguous genitalia that are caused by rudimentary penis, severe hypospadias or traumatic injury require surgical intervention. Although silicone penile prostheses are an accepted treatment modality, biocompatibility issues may be a problem in select cases. We previously demonstrated that rods composed of cartilage could be created using chondrocytes seeded on biodegradable polymer scaffolds. We showed that the cartilage rods engineered ex situ were readily elastic and withstood high degrees of pressure. We investigated the feasibility of applying the engineered cartilage rods in situ in an animal model. MATERIALS AND METHODS: Autologous chondrocytes harvested from rabbit ears were grown and expanded in culture. Cells were seeded onto biodegradable poly-L-lactic acid coated polyglycolic acid polymer rods at a concentration of 50 x 10(6) chondrocytes per cm3. A total of 18 chondrocyte polymer scaffolds were implanted into the corporal spaces in 10 rabbits. As controls, 1 corpus in each of 2 rabbits was not implanted. The animals were sacrificed 1, 2, 3 or 6 months after implantation. Histological analysis was performed using hematoxylin and eosin, aldehyde fuschin-alcian blue and toluidine blue staining. RESULTS: All animals tolerated the implants for the duration of the study without any complications. Gross examination after retrieval at 1 month showed well formed, milky white cartilage structures within the corpora. All polymers were fully degraded by 2 months. There was no evidence of erosion or infection at any of the implant sites. Histological analysis using alcian blue and toluidine blue staining revealed mature and well formed chondrocytes in the retrieved implants. CONCLUSIONS: Autologous chondrocytes seeded on preformed biodegradable polymer structures form cartilage structures within the rabbit corpus cavernosum. This technology appears to be useful for creating autologous penile prostheses.

Animals↗
PubMed1999

Acellular collagen matrix as a possible "off the shelf" biomaterial for urethral repair.

OBJECTIVES: To determine whether a naturally derived collagen-based tissue substitute developed for urethral reconstruction would be suitable for urethral repair in an animal model. Several urethral conditions often require nongenital tissues for reconstruction, such as skin grafts or mucosal grafts from the bladder or buccal regions. However, the use of these tissues for urethroplasty may be associated with additional procedures for graft retrieval, prolonged hospitalization, and morbidity. METHODS: A ventral urethral defect was created in 10 male rabbits. The acellular collagen matrix, obtained and processed from porcine bladder submucosa, was trimmed and used to replace the urethral defect in an onlay fashion. Serial urethrography was performed pre- and postoperatively at 0.5, 1, 2, 3, and 6 months. The animals were sacrificed 0.5, 1, 2, 3, and 6 months after surgery. The retrieved implants were analyzed grossly, histologically, and with immunocytochemistry. RESULTS: All animals survived until being sacrificed without any noticeable voiding dysfunction. Serial urethrograms confirmed the maintenance of a wide urethral caliber without any signs of strictures. Gross examination at retrieval showed normally appearing tissue without any evidence of fibrosis. Histologically, the implanted matrices contained host cell infiltration and generous angiogenesis by 2 weeks after surgery. The presence of a confluent transitional cell layer was confirmed by immunocytochemical analyses using pancytokeratin antibodies. Anti-alpha actin antibodies demonstrated the migration of unorganized muscle fiber bundles 2 months after implantation and organized muscle bundles 6 months after implantation. CONCLUSIONS: The acellular collagen matrix appears to be a useful material for urethral repair in the rabbit. The matrix can be processed easily, has good characteristics for tissue handling and urethral function, and has the advantage of being an "off the shelf" material.

Animals↗
PubMed1999

De novo reconstitution of a functional mammalian urinary bladder by tissue engineering.

Human organ replacement is limited by a donor shortage, problems with tissue compatibility, and rejection. Creation of an organ with autologous tissue would be advantageous. In this study, transplantable urinary bladder neo-organs were reproducibly created in vitro from urothelial and smooth muscle cells grown in culture from canine native bladder biopsies and seeded onto preformed bladder-shaped polymers. The native bladders were subsequently excised from canine donors and replaced with the tissue-engineered neo-organs. In functional evaluations for up to 11 months, the bladder neo-organs demonstrated a normal capacity to retain urine, normal elastic properties, and histologic architecture. This study demonstrates, for the first time, that successful reconstitution of an autonomous hollow organ is possible using tissue-engineering methods.

Animals↗
PubMed1999

Progressive dilation for bladder tissue expansion.

PURPOSE: The use of gastrointestinal tissue for augmentation cystoplasty is associated with numerous complications. We previously reported the development of a system in which ureters were progressively dilated and used for ureterocystoplasty. We have now applied a similar system for the progressive expansion of native bladder tissue. We investigated whether the expanded bladder tissue retained normal functional and phenotypic characteristics. MATERIALS AND METHODS: Urodynamic studies were performed in 5 beagle dogs and the bladder was divided horizontally into a superior bladder neo-reservoir, and an intact smaller bladder inferiorly with both ureters left intact and draining. A silicone catheter was threaded into the newly formed, superiorly located neo-reservoir, and connected to an injection port which was secured subcutaneously. A saline antibiotic solution was injected daily into the palpable injection port 4 weeks after surgery, dilating the neo-reservoir through the silicone catheter. Baseline and weekly cystograms were performed. Urodynamic studies of the neo-reservoirs were done immediately before sacrifice. Animals were sacrificed 3 months after the initial intervention and the bladder was examined grossly and microscopically. RESULTS: Within 30 days after progressive dilation, the neo-reservoir volume was expanded at least 10-fold according to radiography and cystometrograms. Urodynamic studies of the dilated neo-reservoirs showed normal compliance in all animals. Microscopic examination of the expanded neo-reservoir tissue revealed normal histology. A series of immunocytochemical studies demonstrated that the dilated bladder tissue maintained normal phenotypic characteristics. CONCLUSIONS: The system of progressive dilation is effective in expanding bladder tissue which is able to retain normal phenotypic and functional characteristics.

Animals↗
PubMed1998

Bladder augmentation using allogenic bladder submucosa seeded with cells.

OBJECTIVES: The search for a suitable material to reconstruct the genitourinary tract has been a challenging task. Bowel has been widely used for urinary tract reconstruction, despite its subsequent complications. We investigated the possibility of using allogenic bladder submucosa, a tissue consisting of nonimmunogenic acellular collagen, either with or without cells, as a material for bladder augmentation. METHODS: Partial cystectomies were performed in 10 beagle dogs. Both urothelial and smooth muscle cells were harvested and expanded separately in 5 animals. The allogenic bladder submucosa obtained from sacrificed dogs was seeded with muscle cells on one side and urothelial cells on the opposite side. All beagles underwent cruciate cystotomies on the bladder dome. Augmentation cystoplasty was performed with the allogenic bladder submucosa seeded with cells in 5 animals and with the allogenic bladder submucosa without cells in 5. The augmented bladders were retrieved 2 and 3 months after augmentation. RESULTS: Bladders augmented with the allogenic bladder submucosa seeded with cells showed a 99% increase in capacity compared with bladders augmented with the cell-free allogenic bladder submucosa, which showed only a 30% increase in capacity. All dogs showed a normal bladder compliance, as evidenced by urodynamic studies. Histologically, all retrieved bladders contained a normal cellular organization consisting of a urothelial lined lumen surrounded by submucosal tissue and smooth muscle. Immunocytochemical analyses confirmed the urothelial and muscle cell phenotype and showed the presence of nerve fibers. CONCLUSIONS: These results show that allogenic bladder submucosa seeded with cells appears to be an excellent option as a biomaterial for bladder augmentation.

Animals↗
PubMed1998

Cartilage rods as a potential material for penile reconstruction.

PURPOSE: Sex assignment is made in patients with ambiguous genitalia, genital trauma or iatrogenic injury after a thorough diagnostic evaluation and careful consultation with the family. In numerous instances a decision is made to rear the child as the female gender due to inadequate genitalia regardless of karyotype. Although a silicone penile prosthesis is accepted treatment in adults who require penile reconstruction, it has not been generally used in the pediatric population, mainly due to associated long-term problems. We determine the feasibility of creating natural penile prostheses of cartilage which, if biocompatible and elastic, may be used in patients who require genital reconstruction. MATERIALS AND METHODS: Cartilage was harvested from the articular surface of calf shoulders. Chondrocytes were isolated, grown and expanded in vitro. Cells were seeded onto preformed cylindrical polyglycolic acid polymer rods 1 cm. in diameter and 3 cm. long at a concentration of 50 x 10(6) chondrocytes per cm.3. A total of 40 polymer scaffolds were implanted in the subcutaneous space of 20 athymic mice. In each mouse 2 implantation sites consisted of a polymer scaffold seeded with chondrocytes and a control (polymer alone). Mice were sacrificed 1, 2, 4 and 6 months after implantation, respectively. Stress relaxation studies to measure biomechanical properties, including compression, tension and bending, were performed on the retrieved structures. Histological analyses were done with hematoxylin and eosin, aldehyde fuchsin-alcian blue and toluidine blue staining. RESULTS: Gross examination revealed well formed, milk-white rod-shaped solid cartilaginous structures the same size as the initial implant. Compression, tension and bending studies demonstrated that the cartilaginous structures were readily elastic and withstood high degrees of pressure. Histochemical analyses showed mature, well formed chondrocytes in all implants. There was no evidence of cartilage formation in the controls. CONCLUSIONS: Chondrocytes seeded on preformed biodegradable polymer structures form cartilage rods. The use of an entirely autologous system composed of biodegradable polymers and chondrocytes precludes an immunological reaction. This technology appears to be useful for the creation of a biocompatible malleable penile prosthesis, which may be useful in children with ambiguous genitalia and patients undergoing penile reconstruction.

Animals↗