Comparison of Angiogenic Activities after Urethral Reconstruction Using Free Grafts in Rabbits

Advances in 3D bioprinting for urethral tissue reconstruction

Urethral conditions affect children and adults, increasing the risk of urinary tract infections, voiding and sexual dysfunction, and renal failure. Current tissue replacements differ from healthy urethral tissues in structural and mechanical characteristics, causing high risk of postoperative complications. 3D bioprinting can overcome these limitations through the creation of complex, layered architectures using materials with location-specific biomechanical properties. This review highlights prior research and describes the potential for these emerging technologies to address ongoing challenges in urethral tissue engineering, including biomechanical and structural mismatch, lack of individualized repair solutions, and inadequate wound healing and vascularization. In the future, the integration of 3D bioprinting technology with advanced biomaterials, computational modeling, and 3D imaging could transform personalized urethral surgical procedures.

Construction of adhesive and bioactive silk fibroin hydrogel for treatment of spinal cord injury

Spinal cord injury (SCI) often causes severe and permanent disabilities due to the complexity of injury progression. The promising methods are generally based on tissue engineering technology using biocompatible hydrogels to achieve SCI repair. However, hydrogels are commonly incapable of close contact with the damaged spinal cord stumps and fail to support neural regeneration in SCI. Therefore, it is still a challenge to achieve stable contact with the transected nerve stumps and accelerate neural regeneration in the lesion microenvironment. Here, an in situ forming glycidyl methacrylated silk fibroin/ laminin-acrylate (SF-GMA/LM-AC) hydrogel was fabricated for SCI repair. The polymer chains formed a network quickly after ultraviolet (UV)-light trigger, in topological entanglement with the spinal cord, stitching the hydrogel and wet tissues together like a suture at the molecular scale. The SF-GMA/LM-AC hydrogel also provided a favorable environment for the growth of cells due to the incorporation of LM-AC. Compared with physical entrapment of LM, LM-AC immobilized in the hydrogel by covalent technology provided better microenvironments for neural stem cells (NSCs) growth. The repair of complete transection SCI in rats demonstrated that this hydrogel guided and promoted neural regeneration over 8 weeks, leading to hind limb locomotion recovery. This adhesive and bioactive SF-GMA/LM-AC hydrogel may open many opportunities in various therapeutic indications, including SCI. STATEMENT OF SIGNIFICANCE: Many materials have been developed for building transplanted scaffolds, but it is still a challenge to fabricate bioactive scaffolds and adhesion to wet tissues. In this study, we successfully developed an in situ forming SF-GMA/LM-AC hydrogel for SCI repair. This in situ forming hydrogel formed significant adhesion to the native spinal cord, stitching hydrogel and tissue together like a suture at the molecular scale. In addition, covalent immobilized LM-AC was used as the contact guidance biochemical cues for axonal outgrowth and had much better bioactive effects than physically entangled LM. Moreover, this universal strategy would open an avenue to fabricate adhesive and bioactive hydrogel for various disease treatments including SCI.

Ventral onlay graft urethroplasty using bladder mucosa in a cat with a urethral stricture

A 3-year-old, 4.0 kg, intact male domestic shorthair cat presented with postoperative dysuria following urethral resection and anastomosis for urethral rupture. Retrograde urethrography revealed a stricture in the pelvic urethra. Urethroplasty with bladder mucosa was performed following a bilateral pubic-ischial osteotomy. The bladder wall was resected to harvest an appropriately sized bladder mucosa graft. The graft was placed over the urethral defect in patch fashion and stabilized with interrupted sutures. The cat was able to urinate normally with no evidence of lower urinary tract signs 2 year postoperatively. Therefore, urethroplasty with an onlay bladder mucosa graft may be a feasible alternative to prepubic or subpubic urethrostomy for the treatment of pelvic urethral stricture in cats.

A new technique for ureteral reconstruction using lingual mucosa grafts in a beagle model

PURPOSE

To investigate the feasibility of ureteral reconstruction using lingual mucosa graft (LMG) and evaluate the histological changes of the engrafted LMG in beagles.

METHODS

Twelve male beagle dogs were randomly divided into groups A, B and C (n = 4). A ventral ureteral defect was created by excising half of the ureteral wall. The length of the defect was 3 cm, 6 cm, and 10 cm in groups A, B, and C, respectively. The LMGs were harvested and employed to repair the ureteral defects in onlay fashion. Two dogs per group were sacrificed after 6 months, with additional two dogs per group sacrificed after 12 months. Intravenous urography (IVU) and macroscopic examination were performed to evaluate renal function and ureteral patency. Histological changes in the engrafted LMGs during the tissue incorporation process were assessed by histological analysis.

RESULTS

There were no postoperative complications. Only one dog in group C developed a mild stricture near the proximal anastomosis. In the remaining 11 animals, IVU showed normal renal function and a wide ureteral caliber without stricture or fistula. The diameter of the LMG-reconstructed ureter was greater than that of the proximal and distal ureter (each p value < 0.01). The LMGs survived in situ with newly formed capillaries. The epithelium of the lingual mucosa resembled the urothelium in postoperative 12 months.

CONCLUSION

This new technique for ureteral reconstruction using LMGs is feasible. This approach is a promising alternative clinical treatment for curing long ureteral strictures.

The effect of penile urethral fat graft application on urethral angiogenesis

BACKGROUND

Autologous fat grafts are rich in adipose-derived stem cells, providing optimal soft-tissue replacement and significant quantities of angiogenic growth factor. Although fat grafts (FG) are used in several clinical conditions, the use of FG in urethral repairs and the effects of FG to urethral repairs have not yet been reported.

OBJECTIVE

An experimental study was performed to evaluate the effect of FG on urethral angiogenesis and tissue growth factor (GF) levels.

STUDY DESIGN

Sixteen Wistar albino, adult, male rats were allocated into two groups: the control group (CG) (n = 8) and the experiment group (EG) (n = 8). After anesthetization of all rats, 3-mm vertical incisions were made on the urethras, and then sutured with interrupted 5/0 vicryl sutures. The operations were performed under a stereo dissecting microscope under magnification (×20). In the CG, no additional procedure was performed. In the EG after the same surgical procedure, 1 mm(3) FG was removed from the inguinal region by sharp dissection with a knife. The grafts were trimmed to 1 × 1 mm dimensions on millimeter paper. The FGs were placed on the repaired urethras. The skin was then closed. Samples from urethral and penile skin were taken 21 days after surgery in both groups. Density and intensity of staining with vascular-endothelial GF (VEGF), VEGF-receptor, and endothelial-GF receptor (EGFR) in the endothelial and mesenchymal cells of the penile urethral vessels were immunohistochemically evaluated. Data obtained from immunohistochemical evaluations were analyzed with SPSS 15.0. The P-values lower than 0.05 were considered as significant.

RESULTS

Density of VEGF staining was significantly decreased in the vascular endothelium of the EG compared to the CG (P < 0.05). Density of the EGFR staining was significantly decreased in the vascular endothelium of the EG compared to the CG (P < 0.05) (Table). Intensity of VEGF, VEGF-R and EGFR staining was not significantly different between the two groups. There were no significant differences between groups regarding to VEGFR staining and mesenchymal examination.

DISCUSSION

Decreased density was found in the VEGF staining in the vascular endothelium. This could be explained by the day that the tissues were harvested or because autologous fat grafts might cause decreased growth factor levels, which is contrary to the literature data.

CONCLUSION

Fat grafting has an immunohistochemical effect on the growth factor levels that are related to angiogenesis after urethral repair. It is difficult to make a firm conclusion about the role of fat grafting on urethral healing. Therefore, future studies are needed to see if FG can be used as an alternative to other procedures in order to avoid complications.

Long-term angiogenic activity of free grafts and pedicle flap in a rabbit urethroplasty model

PURPOSE

We studied the late angiogenic activity of free grafts and a pedicle flap in a rabbit urethroplasty model to determine whether angiogenic activity plays a role in late outcomes of urethral reconstruction in rabbits.

METHODS

Twenty-eight rabbits were randomly divided into five groups according to the method used to bridge a urethral defect as an onlay patch: Control, simple closure of urethral defect (Group O1); free penile skin graft (FPSG, Group A1); buccal mucosal graft (BuMG, Group B1); bladder mucosal graft (BlMG, Group C1); and pedicle penile skin flap (PPSF, Group D1). Angiogenic activity of the patch on postoperative day 84 was assessed by immunohistochemistry.

RESULTS

The angiogenic activity in Groups O1, A1, B1, C1, and D1 was 23.33 ± 4.92 (means ± SD), 42.89 ± 6.52, 55.78 ± 3.46, 53.61 ± 6.17, and 24.11 ± 9.07 vessels per optical field, respectively. There were statistically significant differences (p < .001) between Group O1 and A1 B1, C1, Group A1 and B1, C1, D1, Groups B1 and D1 and Groups C1 and D1, but not between Groups O1 and D1 (p = 1.000) and Groups B1 and C1 (p = .872). The long-term angiogenic activity of all the groups was significantly lower (p < .001) than in the corresponding early groups.

CONCLUSIONS

Although the angiogenic activity of all the groups decreased in the late assessment, the buccal mucosal graft continued to exhibit elevated angiogenesis above bladder or skin (free or pedicle) graft. Therefore, buccal mucosal patch graft might be preferable because of its easier harvesting.

Urethral Reconstruction Using the Radial Forearm Free Flap: Experience in Oncologic Cases and Gender Reassignment

OBJECTIVES

Urethra reconstruction in men remains a complex problem, particularly in patients who have had previous amputation for penile tumour or who have undergone gender reassignment. Many reconstructive techniques currently in use recreate the urethra but are prone to recurrent stricture formation and fail to achieve micturition with a good stream when standing. The authors propose using the radial forearm fasciocutaneous free flap as a single-stage technique of male urethral reconstruction.

METHODS

During 1999-2004, nine patients underwent microsurgical reconstruction of the male urethra using the radial forearm fasciocutaneous free flap. Three patients underwent urethral reconstruction following previous subcutaneous penectomy for penile cancer. Another six patients had urethral reconstruction performed after failure of primary urethra construction as part of their gender reassignment surgery.

RESULTS

The average age at the time of surgery was 35.1 yr (range: 22-55 yr) and average follow-up time was 41.8 mo (range: 13-55 mo). Flap reconstruction was successful in all cases, with no instances of free flap failure; however, two patients developed significant stenosis requiring revision, and no patients had postoperative fistula formation. Therefore, the success rate for urethral reconstruction after the first operation was seven of nine. Two patients with stenosis were treated operatively to release strictures with local flaps. Uroflowmetry demonstrated that these patients had satisfactory flow rates.

CONCLUSION

Patient satisfaction and objective studies have demonstrated that urethral reconstruction with the use of radial forearm free flap is a good reconstructive procedure particularly when the patients need an extensive and long urethral reconstruction.

Experience with fibrin glue in bulbar urethral reconstruction using dorsal buccal mucosa graft

Buccal mucosa dorsal onlay graft urethroplasty represents a widespread method for bulbar urethral stricture repair. We describe a modified procedure with the use of fibrin glue applied on the receiving bed before graft location.