Collagen scaffolds tethered with bFGF promote corpus spongiosum regeneration in a beagle model

Scaffold-based tissue engineering strategies for urethral repair and reconstruction

Urethral strictures are common in urology; however, the reconstruction of long urethral strictures remains challenging. There are still unavoidable limitations in the clinical application of grafts for urethral injuries, which has facilitated the advancement of urethral tissue engineering. Tissue-engineered urethral scaffolds that combine cells or bioactive factors with a biomaterial to mimic the native microenvironment of the urethra, offer a promising approach to urethral reconstruction. Despite the recent rapid development of tissue engineering materials and techniques, a consensus on the optimal strategy for urethral repair and reconstruction is still lacking. This review aims to collect the achievements of urethral tissue engineering in recent years and to categorize and summarize them to shed new light on their design. Finally, we visualize several important future directions for urethral repair and reconstruction.

Porous Photocrosslinkable Hydrogel Functionalized with USC Derived Small Extracellular Vesicles for Corpus Spongiosum Repair

Reconstruction of a full-thickness spongy urethra is difficult because a corpus spongiosum (CS) defect cannot be repaired using self-healing or substitution urethroplasty. Small extracellular vesicles (sEVs) secreted by urine-derived stem cells (USC-sEVs) strongly promote vascular regeneration. In this study, it is aimed to explore whether USC-sEVs promote the repair of CS defects. To prolong the in vivo effects of USC-sEVs, a void-forming photoinduced imine crosslinking hydrogel (vHG) is prepared and mixed with the USC-sEV suspension. vHG encapsulated with USC-sEVs (vHG-sEVs) is used to repair a CS defect with length of 1.5 cm and width of 0.8 cm. The results show that vHG-sEVs promote the regeneration and repair of CS defects. Histological analysis reveals abundant sinusoid-like vascular structures in the vHG-sEV group. Photoacoustic microscopy indicates that blood flow and microvascular structure of the defect area in the vHG-sEV group are similar to those in the normal CS group. This study confirms that the in situ-formed vHG-sEV patch appears to be a valid and promising strategy for repairing CS defects.

Engineered Tissues: A Bright Perspective in Urethral Obstruction Regeneration

Impact Statement The current article examines urethral reconstruction on three fronts: presently available grafts, clinical trials, and preclinical studies. In this context, studies have focused on various types of biomaterial grafts, including natural, synthetic, and decellularized, combined with or without cells or growth factors, aiming to improve outcomes at both clinical and pre-clinical stages. Subsequently, four stages in the commercialization regulatory pathway in urethra engineering were examined, focusing on the commercialization challenges, particularly those associated with urethral products. Finally, the forthcoming challenges in urethra engineering and potential solutions for its enhancement have been explored. [Figure: see text].

The Regenerative Microenvironment of the Tissue Engineering for Urethral Strictures

Urethral stricture caused by various reasons has threatened the quality of life of patients for decades. Traditional reconstruction methods, especially for long-segment injuries, have shown poor outcomes in treating urethral strictures. Tissue engineering for urethral regeneration is an emerging concept in which special designed scaffolds and seed cells are used to promote local urethral regeneration. The scaffolds, seed cells, various factors and the host interact with each other and form the regenerative microenvironment. Among the various interactions involved, vascularization and fibrosis are the most important biological processes during urethral regeneration. Mesenchymal stem cells and induced pluripotent stem cells play special roles in stricture repair and facilitate long-segment urethral regeneration, but they may also induce carcinogenesis and genomic instability during reconstruction. Nevertheless, current technologies, such as genetic engineering, molecular imaging, and exosome extraction, provide us with opportunities to manage seed cell-related regenerative risks. In this review, we described the interactions among seed cells, scaffolds, factors and the host within the regenerative microenvironment, which may help in determining the exact molecular mechanisms involved in urethral stricture regeneration and promoting clinical trials and the application of urethral tissue engineering in patients suffering from urethral stricture.

Collagen biomaterials promote the regenerative repair of abdominal wall defects in Bama miniature pigs

Due to adhesion and rejection of recent traditional materials, it is still challenging to promote the regenerative repair of abdominal wall defects caused by different hernias or severe trauma. However, biomaterials with a high biocompatibility and low immunogenicity have exhibited great potential in the regeneration of abdominal muscle tissue. Previously, we have designed a biological collagen scaffold material combined with growth factor, which enables a fusion protein-collagen binding domain (CBD)-basic fibroblast growth factor (bFGF) to bind and release specifically. Though experiments in rodent animals have indicated the regeneration function of CBD-bFGF modified biological collagen scaffolds, its translational properties in large animals or humans are still in need of solid evidence. In this study, the abdominal wall defect model of Bama miniature pigs was established by artificial operations, and the defective abdominal wall was sealed with or without a polypropylene patch, and unmodified and CBD-bFGF modified biological collagen scaffolds. Results showed that a recurrent abdominal hernia was observed in the defect control group (without the use of mesh). Although the polypropylene patch can repair the abdominal wall defect, it also induced serious adhesion and inflammation. Meanwhile, both kinds of collagen biomaterials exhibited positive effects in repairing abdominal wall defects and reducing regional adhesion and inflammation. However, CBD-bFGF-modified collagen biomaterials failed to induce the regenerative repair reported in rat experiments. In addition, unmodified collagen biomaterials induced abdominal wall muscle regeneration rather than fibrotic repair. These results indicated that the unmodified collagen biomaterials are a better option among translational patches for the treatment of abdominal wall defects.

Collagen-binding fibroblast growth factor ameliorates liver fibrosis in murine bile duct ligation injury

Cholestatic liver injury, characterized by liver fibrosis, has increasingly become a global health problem, with no effective treatment available. Hepatic stellate cells (HSCs) differentiate into myofibroblasts, leading to excessive deposition of the extracellular matrix (ECM), which is a feature of liver fibrosis. Basic fibroblast growth factor (bFGF) has proven antifibrotic effects in chronic liver disease; however, the lack of an effective delivery system to the injury site reduces its therapeutic efficacy. The aim of this study was to assess the therapeutic effect of collagen-binding bFGF (CBD-bFGF) for the treatment of liver fibrosis in a murine bile duct ligation (BDL) model. We found that CBD-bFGF treatment significantly alleviated liver injury in the early phase of BDL injury, and was associated with decreased necroptotic cell death and inflammatory response. Moreover, CBD-bFGF had enhanced therapeutic effects for liver fibrosis on day 7 after surgery compared to those obtained with native bFGF treatment. In vitro, CBD-bFGF treatment notably inhibited TGF-β1-induced LX-2 cell activation, migration, and contraction compared with native bFGF. In conclusion, CBD-bFGF may be a promising treatment for hepatic fibrosis.

Assessing the potential regeneration ability of corpus spongiosum in rabbit models

Most congenital or acquired urethral diseases are usually accompanied by corpus spongiosum (CS) defects. However, Substitution urethroplasty can only reconstruct urethral lumen, not the CS. Many long-term complications occur due to the lack of protection from CS. Is CS a kind of tissue that cannot be repaired by regeneration and self-healing? In this study, the CS defect with urethral mucosa intact model was established in rabbits by removing the ventral CS tissue. Based on this model, three groups of different CS defect sizes, with lengths of 0.5 cm (Group A), 1.0 cm (Group B) and 1.5 cm (Group C), were then constructed, respectively, to assess the potential regeneration ability of CS. Three months later, the entire urethra, including the CS defect, was assessed by histological staining. Results showed that the vascular sinusoids were completely removed from urethral mucosa. The rabbit model of CS defect was established successfully. Three months post-operatively, the CS defects in all the 3 groups were replaced by disordered collagen instead of regenerating typical sinusoid-like vascular structure, which is significantly different from the normal CS rich in vascular sinusoids. The CS defects could not be repaired through self-healing. The potential regeneration ability of CS is extremely poor.

Collagen-binding basic fibroblast growth factor improves functional remodeling of scarred endometrium in uterine infertile women: a pilot study

Intrauterine adhesion (IUA) is a common cause of uterine infertility and one of the most severe clinical features is endometrial fibrosis namely endometrial scarring for which there are few cures currently. Blocked angiogenesis is the main pathological change in the scarred endometrium. The fibroblast growth factor 2 (bFGF), a member of FGF family, is usually applied to promote healing of refractory ulcer and contributes to angiogenesis of tissues. In this study, the sustained-release system of bFGF 100 µg was administrated around scarred endometrium guiding by ultrasound every 4 weeks in 18 patients (2-4 times). Results showed that after treatment, the menstrual blood volume, endometrial thickness and the scarred endometrial area were improved. Histological study showed blood vessel density increased obviously. Three patients (3/18) achieved pregnancy over 20 gestational weeks. Therefore, administrating the bFGF surrounding scarred endometrium may provide a new therapeutic approach for the patients with endometrial fibrosis.