Surgical implantation of a bioengineered internal anal sphincter

A systematic review of translation and experimental studies on internal anal sphincter for fecal incontinence

The complexity in the molecular mechanism of the internal anal sphincter (IAS) limits preclinical or clinical outcomes of fecal incontinence (FI) treatment. So far, there are no systematic reviews of IAS translation and experimental studies that have been reported. This systematic review aims to provide a comprehensive understanding of IAS critical role in FI. Previous studies revealed the key pathway for basal tone and relaxation of IAS in different properties as follows; calcium, Rho-associated, coiled-coil containing serine/threonine kinase, aging-associated IAS dysfunction, oxidative stress, renin-angiotensin-aldosterone, cyclooxygenase, and inhibitory neurotransmitters. Previous studies have reported improved functional outcomes of cellular treatment for regeneration of dysfunctional IAS, using various stem cells, but did not demonstrate the interrelationship between those results and basal tone or relaxation-related molecular pathway of IAS. Furthermore, these results have lower specificity for IAS-incontinence due to the included external anal sphincter or nerve injury regardless of the cell type. An acellular approach using bioengineered IAS showed a physiologic response of basal tone and relaxation response similar to human IAS. However, in both cellular and acellular approaches, the lack of human IAS data still hampers clinical application. Therefore, the IAS regeneration presents more challenges and warrants more advances.

Cell Therapy for Anal Sphincter Incontinence: Where Do We Stand?

Anal sphincter incontinence is a chronic disease, which dramatically impairs quality of life and induces high costs for the society. Surgery, considered as the best curative option, shows a disappointing success rate. Stem/progenitor cell therapy is pledging, for anal sphincter incontinence, a substitute to surgery with higher efficacy. However, the published literature is disparate. Our aim was to perform a review on the development of cell therapy for anal sphincter incontinence with critical analyses of its pitfalls. Animal models for anal sphincter incontinence were varied and tried to reproduce distinct clinical situations (acute injury or healed injury with or without surgical reconstruction) but were limited by anatomical considerations. Cell preparations used for treatment, originated, in order of frequency, from skeletal muscle, bone marrow or fat tissue. The characterization of these preparations was often incomplete and stemness not always addressed. Despite a lack of understanding of sphincter healing processes and the exact mechanism of action of cell preparations, this treatment was evaluated in 83 incontinent patients, reporting encouraging results. However, further development is necessary to establish the correct indications, to determine the most-suited cell type, to standardize the cell preparation method and to validate the route and number of cell delivery.

BioSphincters to treat Fecal Incontinence in Nonhuman Primates

Loss of anorectal resting pressure due to internal anal sphincter (IAS) dysfunctionality causes uncontrolled fecal soiling and leads to passive fecal incontinence (FI). The study is focused on immediate and long-term safety and potential efficacy of bioengineered IAS BioSphincters to treat passive FI in a clinically relevant large animal model of passive FI. Passive FI was successfully developed in Non-Human Primates (NHPs) model. The implantation of autologous intrinsically innervated functional constructs resolved the fecal soiling, restored the resting pressure and Recto Anal Inhibitory Reflex (RAIR) within 1-month. These results were sustained with time, and efficacy was preserved up to 12-months. The histological studies validated manometric results with the regeneration of a well-organized neuro-muscular population in IAS. The control groups (non-treated and sham) remained affected by poor anal hygiene, lower resting pressure, and reduced RAIR throughout the study. The pathological assessment of implants, blood, and the vital organs confirmed biocompatibility without any adverse effect after implantation. This regenerative approach of implanting intrinsically innervated IAS BioSphincters has the potential to offer a better quality of life to the patients suffering from FI.

Regenerative medicine as a therapeutic option for fecal incontinence: a systematic review of preclinical and clinical studies

BACKGROUND

Fecal incontinence is the uncontrollable loss of stool and has a prevalence of around 7-15%. This condition has serious implications for patients' quality of life. Current treatment options show unsatisfactory results. A novel treatment option is therefore needed.

OBJECTIVE

This systematic review aims to perform a quality assessment and to give a critical overview of the current research available on regenerative medicine as a treatment for fecal incontinence.

STUDY DESIGN

A systematic search strategy was applied in PubMed, Cochrane Library, EMBASE, MEDLINE, Web of Science, and Cinahl from inception until March of 2018. Studies were found relevant when the animals or patients in the studied group had objectively determined or induced fecal incontinence, and the intervention must have used any kind of cells, stem cells, or biocompatible material, with or without the use of trophic factors. Studies were screened on title and consecutively on abstract for relevance by 2 independent investigators. The risk of bias of preclinical studies was assessed using the SYstematic Review Centre for Laboratory animal Experimentation risk of bias tool for animal studies, and for clinical studies the Cochrane risk of bias tool for randomized trials was used.

RESULTS

In all, 34 preclinical studies and 5 clinical studies were included. Animal species, type of anal sphincter injury, intervention, and outcome parameters were heterogenous. Therefore, a meta-analysis could not be performed. The overall risk of bias of the included studies was high.

CONCLUSION

The efficacy of regenerative medicine to treat fecal incontinence could not be determined due to the high risk of bias and heterogenicity of the available preclinical and clinical studies. The findings of this systematic review may result in improved study design of future studies, which could help the translation of regenerative medicine to the clinic as an alternative to current treatments for fecal incontinence.

Regenerative medicine provides alternative strategies for the treatment of anal incontinence

INTRODUCTION AND HYPOTHESIS

Anal incontinence is a common disorder but current treatment modalities are not ideal and the development of new treatments is needed. The aim of this review was to identify the existing knowledge of regenerative medicine strategies in the form of cellular therapies or bioengineering as a treatment for anal incontinence caused by anal sphincter defects.

METHODS

PubMed was searched for preclinical and clinical studies in English published from January 2005 to January 2016.

RESULTS

Animal studies have demonstrated that cellular therapy in the form of local injections of culture-expanded skeletal myogenic cells stimulates repair of both acute and 2 - 4-week-old anal sphincter injuries. The results from a small clinical trial with ten patients and a case report support the preclinical findings. Animal studies have also demonstrated that local injections of mesenchymal stem cells stimulate repair of sphincter injuries, and a complex bioengineering strategy for creation and implantation of an intrinsically innervated internal anal sphincter construct has been successfully developed in a series of animal studies.

CONCLUSION

Cellular therapies with myogenic cells and mesenchymal stem cells and the use of bioengineering technology to create an anal sphincter are new potential strategies to treat anal incontinence caused by anal sphincter defects, but the clinical evidence is extremely limited. The use of culture-expanded autologous skeletal myogenic cells has been most intensively investigated and several clinical trials were ongoing at the time of this report. The cost-effectiveness of such a therapy is an issue and muscle fragmentation is suggested as a simple alternative.

Prospective regenerative medicine therapies for obstetric trauma-induced fecal incontinence

Fecal incontinence is a major public health issue that has yet to be adequately addressed. Obstetric trauma and injury to the anal sphincter muscles are the most common cause of fecal incontinence. New therapies are emerging aimed at repair or regeneration of sphincter muscle and restoration of continence. While regenerative medicine offers an attractive option for fecal incontinence there are currently no validated techniques using this approach. Although many challenges are yet to be resolved, the advent of regenerative medicine is likely to offer disruptive technologies to treat and possibly prevent the onset of this devastating condition. This article provides a review on regenerative medicine approaches for treating fecal incontinence and a critique of the current landscape in this area.

Successful implantation of an engineered tubular neuromuscular tissue composed of human cells and chitosan scaffold

BACKGROUND

There is an urgent need for gut lengthening secondary to massive resections of the gastrointestinal tract. In this study, we propose to evaluate the remodeling, vascularization, and functionality of a chitosan-based, tubular neuromuscular tissue on subcutaneous implantation in the back of athymic rats.

METHODS

Aligned innervated smooth muscle sheets were bioengineered with the use of human smooth muscle and neural progenitor cells. The innervated sheets were wrapped around tubular chitosan scaffolds. The engineered tubular neuromuscular tissue was implanted subcutaneously in the back of athymic rats. The implant was harvested after 14 days and assessed for morphology, vascularization, and functionality.

RESULTS

Gross examination of the implants showed healthy color with no signs of inflammation. The implanted tissue became vascularized as demonstrated by gross and histologic analysis. Chitosan supported the luminal patency of the tissue. The innervated muscle remodeled around the tubular chitosan scaffold. Smooth muscle maintained its circumferential alignment and contractile phenotype. The functionality of the implant was characterized further by the use of real-time force generation. A cholinergic response was demonstrated by robust contraction in response to acetylcholine. Vasoactive intestinal peptide-, and electrical field stimulation-caused relaxation. In the presence of neurotoxin tetrodotoxin, the magnitude of acetylcholine-induced contraction and vasoactive intestinal peptide-induced relaxation was attenuated whereas electrical field stimulation-induced relaxation was completely abolished, indicating neuronal contribution to the response.

CONCLUSION

Our results indicated the successful subcutaneous implantation of engineered tubular neuromuscular tissues. The tissues became vascularized and maintained their myogenic and neurogenic phenotype and function, which provides potential therapeutic prospects for providing implantable replacement GI segments for treating GI motility disorders.

Tissue-engineering of the gastrointestinal tract

PURPOSE OF REVIEW

The purpose of this review is to describe recent advancements in tissue-engineering of the gastrointestinal system. For some patients, a congenital or acquired defect in the alimentary system results in digestive or nutritional deficiencies requiring intervention. Unfortunately, these treatments are associated with morbid complications. Advances in the growth of tissue-engineered esophagus, stomach, small intestine, colon and anus have been made in recent years. The progress reviewed here hopefully will someday benefit patients with gastrointestinal organ loss by providing a tissue replacement with morphology and function similar to native tissue.

RECENT FINDINGS

In native gastrointestinal tissue, epithelial homeostasis is governed largely by the interaction of the stem cell and its surrounding cellular niche. In particular, the small intestinal stem cell populations identified as the crypt base columnar cell (CBCC) and at cell position 4 (cp4) are responsible for mucosal maintenance and response to injury. This work influences efforts to generate bioengineered tissues for both in-vitro mucosal models and full-thickness in-vivo tissue-engineered esophagus, stomach, intestine and colon.

SUMMARY

Gastrointestinal organ loss is a challenge to manage. Current therapy can be life-saving, but is associated with morbid complications. Tissue-engineering will someday restore normal gastrointestinal function and eliminate the need for nutritional supplementation or transplant.

Successful implantation of bioengineered, intrinsically innervated, human internal anal sphincter

BACKGROUND & AIMS

To restore fecal continence, the weakened pressure of the internal anal sphincter (IAS) must be increased. We bioengineered intrinsically innervated human IAS to emulate sphincteric physiology in vitro.

METHODS

We cocultured human IAS circular smooth muscle with immortomouse fetal enteric neurons. We investigated the ability of bioengineered innervated human IAS, implanted in RAG1-/- mice, to undergo neovascularization and preserve the physiology of the constituent myogenic and neuronal components.

RESULTS

The implanted IAS was neovascularized in vivo; numerous blood vessels were observed with no signs of inflammation or infection. Real-time force acquisition from implanted and preimplant IAS showed distinct characteristics of IAS physiology. Features included the development of spontaneous myogenic basal tone; relaxation of 100% of basal tone in response to inhibitory neurotransmitter vasoactive intestinal peptide (VIP) and direct electrical field stimulation of the intrinsic innervation; inhibition of nitrergic and VIPergic electrical field-induced relaxation (by antagonizing nitric oxide synthesis or receptor interaction); contraction in response to cholinergic stimulation with acetylcholine; and intact electromechanical coupling (evidenced by direct response to potassium chloride). Implanted, intrinsically innervated bioengineered human IAS tissue preserved the integrity and physiology of myogenic and neuronal components.

CONCLUSIONS

Intrinsically innervated human IAS bioengineered tissue can be successfully implanted in mice. This approach might be used to treat patients with fecal incontinence.

Role of rho kinase in the functional and dysfunctional tonic smooth muscles

Tonic smooth muscles play pivotal roles in the pathophysiology of debilitating diseases of the gastrointestinal and cardiovascular systems. Tonic smooth muscles differ from phasic smooth muscles in the ability to spontaneously develop myogenic tone. This ability has been primarily attributed to the local production of specific neurohumoral substances that can work in conjunction with calcium sensitization via signal transduction events associated with the Ras homolog gene family, member A (RhoA)/Rho-associated, coiled-coil containing protein kinase 2 (ROCK II) pathways. In this article, we discuss the molecular pathways involved in the myogenic properties of tonic smooth muscles, particularly the contribution of protein kinase C vs the RhoA/ROCK II pathway in the genesis of basal tone, pathophysiology and novel therapeutic approaches for certain gastrointestinal and cardiovascular diseases. Emerging evidence suggests that manipulation of RhoA/ROCK II activity through inhibitors or silencing of RNA interface techniques could represent a new therapeutic approach for various gastrointestinal and cardiovascular diseases.

In vivo growth of a bioengineered internal anal sphincter: comparison of growth factors for optimization of growth and survival

PURPOSE

Our laboratory has developed and implanted a novel bioengineered internal anal sphincter (IAS) to treat anal incontinence. Fibroblast growth factor-2 (FGF-2) has been used in mice; however, the optimal growth factor for successful IAS implantation is unclear. This study compares several growth factors in order to optimize IAS viability and functionality.

METHODS

Bioengineered IAS rings were implanted subcutaneously into the dorsum of wildtype C57Bl/6 mice, with an osmotic pump dispensing FGF-2, vascular endothelial growth factor (VEGF), or platelet-derived growth factor (PDGF) (n = 4 per group). Control mice received IAS implants but no growth factor. The IAS was harvested approximately 25 days post-implantation. Tissue was subjected to physiologic testing, then histologically analyzed. Muscle phenotype was confirmed by immunofluorescence.

RESULTS

All implants supplemented with growth factors maintained smooth muscle phenotype. Histological scores, blood vessel density and muscle fiber thickness were all markedly better with growth factors. Neovascularization was comparable between the three growth factors. Basal tonic force of the constructs was highest with VEGF or PDGF.

CONCLUSION

All growth factors demonstrated excellent performance. As our ultimate goal is clinical implantation, our strong results with PDGF, a drug approved for use in the United States and the European Union, pave the way for translating bioengineered IAS implantation to the clinical realm.

Successful implantation of physiologically functional bioengineered mouse internal anal sphincter

We have previously developed bioengineered three-dimensional internal anal sphincter (IAS) rings from circular smooth muscle cells isolated from rabbit and human IAS. We provide proof of concept that bioengineered mouse IAS rings are neovascularized upon implantation into mice of the same strain and maintain concentric smooth muscle alignment, phenotype, and IAS functionality. Rings were bioengineered by using smooth muscle cells from the IAS of C57BL/6J mice. Bioengineered mouse IAS rings were implanted subcutaneously on the dorsum of C57BL/6J mice along with a microosmotic pump delivering fibroblast growth factor-2. The mice remained healthy during the period of implantation, showing no external signs of rejection. Mice were killed 28 days postsurgery and implanted IAS rings were harvested. IAS rings showed muscle attachment, neovascularization, healthy color, and no external signs of infection or inflammation. Assessment of force generation on harvested IAS rings showed the following: 1) spontaneous basal tone was generated in the absence of external stimulation; 2) basal tone was relaxed by vasoactive intestinal peptide, nitric oxide donor, and nifedipine; 3) acetylcholine and phorbol dibutyrate elicited rapid-rising, dose-dependent, sustained contractions repeatedly over 30 min without signs of muscle fatigue; and 4) magnitudes of potassium chloride-induced contractions were 100% of peak maximal agonist-induced contractions. Our preliminary results confirm the proof of concept that bioengineered rings are neovascularized upon implantation. Harvested rings maintain smooth muscle alignment and phenotype. Our physiological studies confirm that implanted rings maintain 1) overall IAS physiology and develop basal tone, 2) integrity of membrane ionic characteristics, and 3) integrity of membrane associated intracellular signaling transduction pathways for contraction and relaxation by responding to cholinergic, nitrergic, and VIP-ergic stimulation. IAS smooth muscle tissue could thus be bioengineered for the purpose of implantation to serve as a potential graft therapy for dysfunctional internal anal sphincter in fecal incontinence.