Skeletal muscle tissue engineering approaches to abdominal wall hernia repair

Abdominal wall hernia repair: from prosthetic meshes to smart materials

Hernia reconstruction is one of the most frequently practiced surgical procedures worldwide. Plastic surgery plays a pivotal role in reestablishing desired abdominal wall structure and function without the drawbacks traditionally associated with general surgery as excessive tension, postoperative pain, poor repair outcomes, and frequent recurrence. Surgical meshes have been the preferential choice for abdominal wall hernia repair to achieve the physical integrity and equivalent components of musculofascial layers. Despite the relevant progress in recent years, there are still unsolved challenges in surgical mesh design and complication settlement. This review provides a systemic summary of the hernia surgical mesh development deeply related to abdominal wall hernia pathology and classification. Commercial meshes, the first-generation prosthetic materials, and the most commonly used repair materials in the clinic are described in detail, addressing constrain side effects and rational strategies to establish characteristics of ideal hernia repair meshes. The engineered prosthetics are defined as a transit to the biomimetic smart hernia repair scaffolds with specific advantages and disadvantages, including hydrogel scaffolds, electrospinning membranes, and three-dimensional patches. Lastly, this review critically outlines the future research direction for successful hernia repair solutions by combing state-of-the-art techniques and materials.

Antimicrobial Meshes for Hernia Repair: Current Progress and Perspectives

Recent advances in the development of biomaterials have given rise to new options for surgery. New-generation medical devices can control chemical breakdown and resorption, prevent post-operative adhesion, and stimulate tissue regeneration. For the fabrication of medical devices, numerous biomaterials can be employed, including non-degradable biomaterials (silicone, polypropylene, expanded polytetrafluoroethylene) or biodegradable polymers, including implants and three-dimensional scaffolds for tissue engineering, which require particular physicochemical and biological properties. Based on the combination of new generation technologies and cell-based therapies, the biocompatible and bioactive properties of some of these medical products can lead to progress in the repair of injured or harmed tissue and in tissue regeneration. An important aspect in the use of these prosthetic devices is the associated infection risk, due to the medical complications and socio-economic impact. This paper provides the latest achievements in the field of antimicrobial surgical meshes for hernia repair and discusses the perspectives in the development of these innovative biomaterials.

Innervation of an engineered muscle graft for reconstruction of muscle defects

Autologous muscle flaps are commonly used to reconstruct defects that involve muscle impairment. To maintain viability and functionality of these flaps, they must be properly vascularized and innervated. Tissue-engineered muscles could potentially replace autologous muscle tissue, but still require establishment of sufficient innervation to ensure functionality. In this study, we explored the possibility of innervating engineered muscle grafts transplanted to an abdominal wall defect in mice, by transferring the native femoral nerve to the graft. Six weeks posttransplantation, nerve conduction studies and electromyography demonstrated increased innervation in engineered grafts neurotized with the femoral nerve, as compared to non-neurotized grafts. Histologic assessments revealed axonal penetration and formation of neuromuscular junctions within the grafts. The innervation process described here may advance the fabrication of a fully functional engineered muscle graft that will be of utility in clinical settings.

Genetically engineered human muscle transplant enhances murine host neovascularization and myogenesis

Engineered tissues are a promising tool for addressing the growing need for tissues and organs in surgical reconstructions. Prevascularization of implanted tissues is expected to enhance survival prospects post transplantation and minimize deficiencies and/or hypoxia deeper in the tissue. Here, we fabricate a three-dimensional, prevascularized engineered muscle containing human myoblasts, genetically modified endothelial cells secreting angiopoietin 1 (ANGPT1) and genetically modified smooth muscle cells secreting vascular endothelial growth factor (VEGF). The genetically engineered human muscle shows enhanced host neovascularization and myogenesis following transplantation into a mouse host, compared to the non-secreting control. The vascular, genetically modified cells have been cleared for clinical trials and can be used to construct autologous vascularized tissues. Therefore, the described genetically engineered vascularized muscle has the potential to be fully translated to the clinical setting to overcome autologous tissue shortage and to accelerate host neovascularization and integration of engineered grafts following transplantation.

Luba Perry et al. report transplantation of engineered prevascularized human muscle into mice to repair an abdominal muscle defect. They show that genetically engineering smooth muscle cells to secrete VEGF and endothelial cells to secrete ANGPT1 significantly improves host neovascularization and myogenesis.

Design Strategies and Applications of Biomaterials and Devices for Hernia Repair

Hernia repair is one of the most commonly performed surgical procedures worldwide, with a multi-billion dollar global market. Implant design remains a critical challenge for the successful repair and prevention of recurrent hernias, and despite significant progress, there is no ideal mesh for every surgery. This review summarizes the evolution of prostheses design toward successful hernia repair beginning with a description of the anatomy of the disease and the classifications of hernias. Next, the major milestones in implant design are discussed. Commonly encountered complications and strategies to minimize these adverse effects are described, followed by a thorough description of the implant characteristics necessary for successful repair. Finally, available implants are categorized and their advantages and limitations elucidated, including non-absorbable and absorbable (synthetic and biologically derived) prostheses, composite prostheses, and coated prostheses. This review not only summarizes the state of the art in hernia repair, but also suggests future research directions toward improved hernia repair utilizing novel materials and fabrication methods.

Adipose-derived stem-cell-seeded non-cross-linked porcine acellular dermal matrix increases cellular infiltration, vascular infiltration, and mechanical strength of ventral hernia repairs

Adipose-derived stem cells (ASCs) facilitate wound healing by improving cellular and vascular recruitment to the wound site. Therefore, we investigated whether ASCs would augment a clinically relevant bioprosthetic mesh-non-cross-linked porcine acellular dermal matrix (ncl-PADM)-used for ventral hernia repairs in a syngeneic animal model. ASCs were isolated from the subcutaneous adipose tissue of Brown Norway rats, expanded, and labeled with green fluorescent protein. ASCs were seeded (2.5×10(4) cells/cm(2)) onto ncl-PADM for 24 h before surgery. In vitro ASC adhesion to ncl-PADM was assessed at 0.5, 1, and 2 h after seeding, and cell morphology on ncl-PADM was visualized by scanning electron microscopy. Ventral hernia defects (2×4 cm) were created and repaired with ASC-seeded (n=31) and control (n=32) ncl-PADM. Explants were harvested at 1, 2, and 4 weeks after surgery. Explant remodeling outcomes were evaluated using gross evaluation (bowel adhesions, surface area, and grade), histological analysis (hematoxylin and eosin and Masson's trichrome staining), immunohistochemical analysis (von Willebrand factor VIII), fluorescent microscopy, and mechanical strength measurement at the tissue-bioprosthetic mesh interface. Stem cell markers CD29, CD90, CD44, and P4HB were highly expressed in cultured ASCs, whereas endothelial and hematopoietic cell markers, such as CD31, CD90, and CD45 had low expression. Approximately 85% of seeded ASCs adhered to ncl-PADM within 2 h after seeding, which was further confirmed by scanning electron microcopy examination. Gross evaluation of the hernia repairs revealed weak omental adhesion in all groups. Ultimate tensile strength was not significantly different in control and treatment groups. Conversely, elastic modulus was significantly greater at 4 weeks postsurgery in the ASC-seeded group (p<0.001). Cellular infiltration was significantly higher in the ASC-seeded group at all time points (p<0.05). Vascular infiltration was significantly greater at 4 weeks postsurgery in the ASC-seeded group (p<0.001). The presence of ASCs improved remodeling outcomes by yielding an increase in cellular infiltration and vascularization of ncl-PADM and enhanced the elastic modulus at the ncl-PADM-tissue interface. With the ease of harvesting adipose tissues that are rich in ASCs, this strategy may be clinically translatable for improving ncl-PADM ventral hernia repair outcomes.

Tissue engineering as a potential alternative or adjunct to surgical reconstruction in treating pelvic organ prolapse

INTRODUCTION AND HYPOTHESIS

Cell-based tissue engineering strategies could potentially provide attractive alternatives to surgical reconstruction of native tissue or the use of surgical implants in treating pelvic organ prolapse (POP).

METHODS

Based on a search in PubMed, this review focuses on candidate cell types, scaffolds, and trophic factors used in studies examining cell-based tissue engineering strategies to treat POP, stress urinary incontinence (SUI), and the closely related field of hernias.

RESULTS

In contrast to the field of SUI, the use of cell-based tissue engineering strategies to treat POP are very sparsely explored, and only preclinical studies exist.

CONCLUSION

The available evidence suggests that the use of autologous muscle-derived cells, fibroblasts, or mesenchymal stem cells seeded on biocompatible, degradable, and potentially growth-promoting scaffolds could be an alternative to surgical reconstruction of native tissue or the use of conventional implants in treating POP. However, the vagina is a complex organ with great demands of functionality, and the perfect match of scaffold, cell, and trophic factor has yet to be found and tested in preclinical studies. Important issues such as safety and economy must also be addressed before this approach is ready for clinical studies.

Tissue engineering as a potential alternative or adjunct to surgical reconstruction in treating pelvic organ prolapse

INTRODUCTION AND HYPOTHESIS

Cell-based tissue engineering strategies could potentially provide attractive alternatives to surgical reconstruction of native tissue or the use of surgical implants in treating pelvic organ prolapse (POP).

METHODS

Based on a search in PubMed, this review focuses on candidate cell types, scaffolds, and trophic factors used in studies examining cell-based tissue engineering strategies to treat POP, stress urinary incontinence (SUI), and the closely related field of hernias.

RESULTS

In contrast to the field of SUI, the use of cell-based tissue engineering strategies to treat POP are very sparsely explored, and only preclinical studies exist.

CONCLUSION

The available evidence suggests that the use of autologous muscle-derived cells, fibroblasts, or mesenchymal stem cells seeded on biocompatible, degradable, and potentially growth-promoting scaffolds could be an alternative to surgical reconstruction of native tissue or the use of conventional implants in treating POP. However, the vagina is a complex organ with great demands of functionality, and the perfect match of scaffold, cell, and trophic factor has yet to be found and tested in preclinical studies. Important issues such as safety and economy must also be addressed before this approach is ready for clinical studies.

Musculature tissue engineering to repair abdominal wall hernia

Hernia repair is one of the most frequently performed operations in surgical clinics. Tissue engineering provides insights for the treatment of abdominal wall hernias and other disorders involving deficiencies in the musculature. The present review summarizes the mechanisms of muscle development and regeneration and provides an overview of tissue engineering strategies for the construction of muscles.

Abdominal hernia repair with a decellularized dermal scaffold seeded with autologous bone marrow-derived mesenchymal stem cells

Surgeons usually use synthetic polymer meshes for abdominal wall hernia repair. However, synthetic polymer meshes exhibit a lack of growth and related complications. In this study, we produced a tissue-engineered patch for abdominal hernia repair. Autologous bone-marrow-derived mesenchymal stem cells (BMSCs) were isolated and proliferated in vitro; decellularized dermal scaffolds (DSs) were prepared using enzymatic process; and then BMSCs were seeded onto the DSs for the construction of tissue-engineered patches. Under general anesthesia, rabbits underwent creation of abdominal wall defects and which were repaired with BMSC-seeded DSs, acellular DSs, and skin sutures only, respectively. Animals were sacrificed after 2 months for assessing the histological and gross examination. Abdominal hernias were absent in animals repaired with cell-seeded group, and abdominal hernias or bulges appeared in all animals repaired with acellular group. All the animals that were not repaired died within 10 days. The cell-seeded implants were thicker and indicated good angiogenesis compared with that of the acellular implants, both in histological and gross examination. The tissue-engineered patches prepared with BMSCs seeding on DSs can be used for abdominal wall hernia repair.

Improved vascular organization enhances functional integration of engineered skeletal muscle grafts

Severe traumatic events such as burns, and cancer therapy, often involve a significant loss of tissue, requiring surgical reconstruction by means of autologous muscle flaps. The scant availability of quality vascularized flaps and donor site morbidity often limit their use. Engineered vascularized grafts provide an alternative for this need. This work describes a first-time analysis, of the degree of in vitro vascularization and tissue organization, required to enhance the pace and efficacy of vascularized muscle graft integration in vivo. While one-day in vitro was sufficient for graft integration, a three-week culturing period, yielding semiorganized vessel structures and muscle fibers, significantly improved grafting efficacy. Implanted vessel networks were gradually replaced by host vessels, coupled with enhanced perfusion and capillary density. Upregulation of key graft angiogenic factors suggest its active role in promoting the angiogenic response. Transition from satellite cells to mature fibers was indicated by increased gene expression, increased capillary to fiber ratio, and similar morphology to normal muscle. We suggest a "relay" approach in which extended in vitro incubation, enabling the formation of a more structured vascular bed, allows for graft-host angiogenic collaboration that promotes anastomosis and vascular integration. The enhanced angiogenic response supports enhanced muscle regeneration, maturation, and integration.

Fabrication and characterization of porous EH scaffolds and EH-PEG bilayers

Biomaterials made from synthetic polymers are becoming more pervasive in the medical field. Synthetic polymers are particularly advantageous as their chemical and mechanical properties can be easily tailored to a specific application. This work characterizes polymer scaffolds derived from the cyclic acetal monomer 5-ethyl-5-(hydroxymethyl)-β,β-dimethyl-1,3-dioxane-2-ethanol diacrylate (EHD). Both porous scaffolds and bilayer scaffolds based upon the EHD monomer were fabricated, and the resulting scaffolds' degradation and mechanical properties were studied. The results showed that by modifying the architecture of an EH scaffold, either by adding a porous network or a poly(ethylene glycol) (PEG) coating, the degradation and Young's modulus of the biomaterial can be significant altered. However, results also indicated that these architectural modifications can be accomplished without a significant loss in the flexural strength of the scaffold. Therefore, we suggest that porous EH scaffolds, and particularly porous EH-PEG bilayers, may be especially useful in dynamic tissue environments due to their advantageous architectural and mechanical properties.

Novel polyurethanes with interconnected porous structure induce in vivo tissue remodeling and accompanied vascularization

Tissue engineering and regenerative medicine have furnished a vast range of modalities to treat either damaged tissue or loss of soft tissue or its function. In most approaches, a temporary porous scaffold is required to support tissue regeneration. The scaffold should be designed such that the turnover synchronizes with tissue remodeling and regeneration at the implant site. Segmented polyester urethanes (PUs) used in this study were based on epsilon-caprolactone (CL) and co-monomers D,L-lactide (D,L-L) and gamma-butyrolactone (BL), and 1,4-butanediisocyanate (BDI). In vitro, the PUs were nontoxic and haemocompatible. To test in vivo biocompatibility, the PUs were further processed into porous structures and subcutaneously implanted in rats for a period up to 21 days. Tissue remodeling and scaffold turnover was associated with a mild tissue response. The tissue response was characterized by extensive vascularization through the interconnected pores, with low numbers of macrophages on the edges and stroma formation inside the pores of the implants. The tissue ingrowth appeared to be related to the extent of microphase separation of the PUs and foam morphology. By day 21, all of the PU implants were highly vascularized, confirming the pores were interconnected. Degradation of P(CL/D,L-L)-PU was observed at this time, whereas the other two PU types remained intact. The robust method reported here of manufacturing and processing, good mechanical properties, and in vivo tissue response of the porous P(CL/D,L-L)-PU and PBCL-PU makes them excellent candidates as biomaterials with an application for soft tissue remodeling, for example, for cardiovascular regeneration.