Bioactive porous beads as an injectable urethral bulking agent: in vivo animal study for the treatment of urinary incontinence

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.

Stem cell therapy combined with controlled release of growth factors for the treatment of sphincter dysfunction

Sphincter dysfunction often occurs at the end of tubule organs such as the urethra, anus, or gastroesophageal sphincters. It is the primary consequence of neuromuscular impairment caused by trauma, inflammation, and aging. Despite intensive efforts to recover sphincter function, pharmacological treatments have not achieved significant improvement. Cell- or growth factor-based therapy is a promising approach for neuromuscular regeneration and the recovery of sphincter function. However, a decrease in cell retention and viability, or the short half-life and rapid degradation of growth factors after implantation, remain obstacles to the translation of these therapies to the clinic. Natural biomaterials provide unique tools for controlled growth factor delivery, which leads to better outcomes for sphincter function recovery in vivo when stem cells and growth factors are co-administrated, in comparison to the delivery of single therapies. In this review, we discuss the role of stem cells combined with the controlled release of growth factors, the methods used for delivery, their potential therapeutic role in neuromuscular repair, and the outcomes of preclinical studies using combination therapy, with the hope of providing new therapeutic strategies to treat incontinence or sphincter dysfunction of the urethra, anus, or gastroesophageal tissues, respectively.

In-vitro cellular and in-vivo investigation of ascorbic acid and β-glycerophosphate loaded gelatin/sodium alginate injectable hydrogels for urinary incontinence treatment

Urinary incontinence is one of the most common disorders especially in adult women. In this study, cellular and in-vivo analyses were performed on (3-glycidyloxypropyl) trimethoxysilane (GPTMS) and CaCl2 cross-linked alginate and gelatin hydrogels containing β-glycerophosphate and ascorbic acid to evaluate the regenerative potential as injectable compression agents for the treatment of urinary incontinence. The hydrogels were prepared with different percentages of components and were named as GA1 (7.2% w/v gelatin, 6% w/v sodium alginate, 0.5:1w/w GPTMS, CaCl2 1% (wt) sodium alginate, 50 μg/mL ascorbic acid, 1.5 mg/mL β-glycerophosphate), GA2 (10% w/v gelatin, 8.5% w/v sodium alginate, 0.5:1 w/w GPTMS, CaCl2 1% (wt) sodium alginate, 50 μg/mL ascorbic acid, 1.5 mg/mL β-glycerophosphate), and GA3 (10% (w/v) gelatin, 8.5% w/v sodium alginate, 1:1 w/w GPTMS, CaCl2 1% (wt) sodium alginate, 50 μg/mL ascorbic acid, 1.5 mg/mL β-glycerophosphate) hydrogels. The results of cell studies showed that although all three samples supported cell adhesion and survival, the cellular behavior of the GA2 sample was better than the other samples. Animal tests were performed on the optimal GA2 sample, which showed that this hydrogel repaired the misfunction tissue in a rat model within 4 weeks and the molecular layer thickness was reached the normal tissue after this duration. It seems that these hydrogels, especially GA2 sample containing 10% (w/v) gelatin, 8.5% (w/v) sodium alginate, 0.5:1 (w/w) GPTMS, CaCl2 1% (wt) sodium alginate, 50 μg/mL ascorbic acid, and 1.5 mg/mL β-glycerophosphate, can act as an injetable hydrogel for urinary incontinence treatment without the need for repeating the injection.

Use of bioactive extracellular matrix fragments as a urethral bulking agent to treat stress urinary incontinence

Injection of urethral bulking agents is a low-risk, minimally invasive surgical procedure to treat stress urinary incontinence (SUI). In this study, we developed a promising injectable bulking agent comprising extracellular matrix fragments of adipose-derived stem cell sheets (ADSC ECM) and investigated its effectiveness in urethral bulking therapy. The structural integrity and proteins of ADSC sheet ECM were well retained in decellularized ADSC ECM fragments. To locate transplanted ADSC ECM fragments, they were labeled with ultrasmall super-paramagnetic iron oxide nanoparticles, which enabled in vivo monitoring after implantation in a SUI rat model for up to 4 weeks. When ADSC ECM fragments were injected into the rat urethra, they became fully integrated with the surrounding tissue within 1 week. Four weeks after transplantation, host cells had regenerated within the ADSC ECM fragment injection area. Moreover, new smooth muscle tissue had formed around the ADSC ECM fragments, as confirmed by positive staining of myosin. These results indicate that injection of ECM fragments may be a promising minimally invasive approach for treating SUI.

Dual growth factor-immobilized microspheres for tissue reinnervation: in vitro and preliminary in vivo studies

Growth factors (GFs) (basic fibroblast growth factor (bFGF) and/or nerve growth factor (NGF))-immobilized polycaprolactone (PCL)/Pluronic F127 microspheres were prepared using an isolated particulate-melting method and the sequential binding of heparin and GFs onto the microspheres. The GFs immobilized on the microspheres were released in a sustained manner over 28 days, regardless of GF type. From the in vitro culture of muscle-derived stem cells, it was observed that the NGF-immobilized microspheres induced more neurogenic differentiation than the bFGF-immobilized microspheres, as evidenced by a quantitative real-time polymerase chain reaction using specific neurogenic markers (Nestin, GFAP, β-tubulin, and MAP2) and Western blot (Nestin and β-tubulin) analyses. The dual bFGF/NGF-immobilized microspheres showed better neurogenic differentiation than the microspheres immobilized with single bFGF or NGF. From the preliminary animal study, the dual bFGF/NGF-immobilized microsphere group also showed effective nerve regeneration, as evaluated by immunocytochemistry using a marker - β-tubulin. The dual bFGF/NGF-immobilized PCL/Pluronic F127 microspheres may be a promising candidate for nerve regeneration in certain target tissues (i.e. muscles) leading to sufficient reinnervation.

Dual growth factor-loaded in situ gel-forming bulking agent: passive and bioactive effects for the treatment of urinary incontinence

Stress urinary incontinence (SUI) is one of the major medical problems for adult females and has a devastating effect on their quality of life. The major cause of the development of the SUI is dysfunction of the urethral supporting tissues as a result of aging and childbirth. In this study, in situ gel-forming bulking agent loaded with dual growth factors, nerve growth factor (NGF) and basic fibroblast growth factor (bFGF), was fabricated. The bulking agent consisted of three components; (i) polycaprolactone (PCL) beads, (ii) bFGF-loaded nanogels, and (iii) NGF-loaded in situ gel forming solution. The bulking agent can provide an initial passive bulking effect (from the PCL beads) and regenerate malfunctioning tissues around the urethra (from the sequential and continuous release of growth factors from the hydrogel) for the effective treatment of SUI. The PCL beads were located stably at the applied urethra site (urinary incontinent SD rat) without migration to provide a passive bulking effect. The sequential release of the growth factors (NGF within a week and bFGF for more than 4 weeks) from the bulking agent provided regeneration of damaged nerve and smooth muscle, and thus enhanced biological function around the urethra. From the findings, we suggest that dual growth factor (NGF and bFGF)-loaded in situ gel-forming bulking agent may be a promising injectable bioactive system for the treatment for SUI.

Functional recovery of urethra by plasmid DNA-loaded injectable agent for the treatment of urinary incontinence

Stress urinary incontinence (SUI) is an embarrassing problem affecting a large number of women and interfering with their quality of life. The injury or weakness of urethral supporting tissues by childbirth and aging has been considered as key factors in the development of the SUI. In this study, plasmid DNA (pDNA; encoding for bFGF) complex-loaded poly(DL-lactic-co-glycolic acid) (PLGA)/Pluronic F127 mixture dispersed with polycaprolactone (PCL) microspheres was prepared as an injectable bioactive bulking agent that may provide bulking effect (by PCL microspheres) and allow stimulation of the defect tissues around urethra (by synthesis of bFGF from cells or tissues transfected by the pDNA complex) for the effective treatment of SUI. From in vitro experiments, the pDNA complex incorporated in the bulking agent was released in a sustained manner over 84 days (≥80% of the initial loading amount). The pDNA complex was effectively transfected into fibroblasts and the cells were continuously producing the target protein, bFGF. From the in vivo study using hairless mice and Sprague-Dawley rats, it was confirmed that the pDNA complex released from the bulking agent is transfected into surrounding cells/tissue, and the cells/tissues synthesize sufficient bFGF to regenerate smooth muscle with biological function around the urethra. Basis on these results, the pDNA (encoding for bFGF) complex-loaded PLGA/Pluronic F127 mixture dispersed with PCL microspheres can be a promising bioactive bulking agent system for the fundamental cure of SUI.

Injection of porous polycaprolactone beads containing autologous myoblasts in a dog model of fecal incontinence

PURPOSE

Few studies have examined whether bioengineering can improve fecal incontinence. This study designed to determine whether injection of porous polycaprolactone beads containing autologous myoblasts improves sphincter function in a dog model of fecal incontinence.

METHODS

The anal sphincter of dogs was injured and the dogs were observed without and with (n = 5) the injection of porous polycaprolactone beads containing autologous myoblasts into the site of injury. Autologous myoblasts purified from the gastrocnemius muscles were transferred to the beads. Compound muscle action potentials (CMAP) of the pudendal nerve, anal sphincter pressure, and histopathology were determined 3 months after treatment.

RESULTS

The amplitudes of the CMAP in the injured sphincter were significantly lower than those measured before injury (1.22 mV vs. 3.00 mV, P = 0.04). The amplitudes were not different between dogs with and without the injection of autologous myoblast beads (P = 0.49). Resting and squeezing pressures were higher in dogs treated with autologous myoblast beads (2.00 mmHg vs. 1.80 mmHg; 6.13 mmHg vs. 4.02 mmHg), although these differences were not significant in analyses of covariance adjusted for baseline values. The injection site was stained for smooth muscle actin, but showed evidence of foreign body inflammatory reactions.

CONCLUSION

This was the first study to examine whether bioengineering could improve fecal incontinence. Although the results did not show definite evidence that injection of autologous myoblast beads improves sphincter function, we found that the dog model was suitable and reliable for studying the effects of a potential treatment modality for fecal incontinence.

Polycaprolactone spheres and theromosensitive Pluronic F127 hydrogel for vocal fold augmentation: in vivo animal study for the treatment of unilateral vocal fold palsy

OBJECTIVES/HYPOTHESIS

The purpose of this study was to explore a novel strategy to restore vocal gap by using polycaprolactone (PCL) spheres with thermosensitive Pluronic F127 in a paralyzed rabbit vocal fold.

STUDY DESIGN

In vivo study using a rabbit model.

METHODS

The PCL spheres were fabricated by an isolated particle-melting method. The PCL spheres/Pluronic F127 gel mixture was prepared by a simple mixture of PCL and Pluronic F127 solution. We used 33 New Zealand white rabbits, which were divided into normal (n = 3), vocal fold palsy (VFP, n = 12), PCL/Pluronic F127 gel mixture (PCL, n = 12), and Radiesse (n = 6) groups. After unilateral recurrent laryngeal nerve section, PCL or Radiesse were injected into paralyzed vocal folds. Laryngoscopic exams were performed 1, 2, 4, and 12 weeks after implantation; then larynx specimens were sampled. High-speed camera recording of vocal fold vibration and evaluation by videokymography were performed. Open quotient and asymmetric index were calculated. We evaluated the volume of the implants over time and investigated histologic changes.

RESULTS

Endoscopic analysis showed that PCL/Pluronic F127 gel mixture maintained its volume without migration or inflammatory response. Vocal fold gap decreased and asymmetric vocal fold movement was improved compared with the VFP group. Histologically, connective tissue growth was observed between the spheres. The remaining volume of injected material was greater than the Radiesse group, without statistical significance.

CONCLUSIONS

Locally injected PCL/Pluronic F127 can enhance glottal contact, suggesting it as a potential new therapeutic approach that may lead to better treatment of vocal fold palsy.