EH Networks as a scaffold for skeletal muscle regeneration in abdominal wall hernia repair

Multifunctional Fluorinated Lubricant-Infused Poly(4-Hydroxybutyrate) (P4HB) Membranes for Full-Thickness Abdominal Wall Defect Repair

Abdominal wall defect caused by surgical trauma, congenital rupture, or tumor resection may result in hernia formation or even death. Tension-free abdominal wall defect repair by using patches is the gold standard to solve such problems. However, adhesions following patch implantation remain one of the most challenging issues in surgical practice. The development of new kinds of barriers is key to addressing peritoneal adhesions and repairing abdominal wall defects. It is already well recognized that ideal barrier materials need to have good resistance to nonspecific protein adsorption, cell adhesion, and bacterial colonization for preventing the initial development of adhesion. Herein, electrospun poly(4-hydroxybutyrate) (P4HB) membranes infused with perfluorocarbon oil are used as physical barriers. The oil-infused P4HB membranes can greatly prevent protein attachment and reduce blood cell adhesion in vitro. It is further shown that the perfluorocarbon oil-infused P4HB membranes can reduce bacterial colonization. The in vivo study reveals that perfluoro(decahydronaphthalene)-infused P4HB membranes can significantly prevent peritoneal adhesions in the classic abdominal wall defects' model and accelerate defect repair, as evidenced by gross examination and histological evaluation. This work provides a safe fluorinated lubricant-impregnated P4HB physical barrier to inhibit the formation of postoperative peritoneal adhesions and efficiently repair soft-tissue defects.

Living scaffolds: surgical repair using scaffolds seeded with human adipose-derived stem cells

BACKGROUND

Decellularized porcine small intestinal submucosa (SIS) is a biological scaffold used surgically for tissue repair. Here, we demonstrate a model of SIS as a scaffold for human adipose-derived stem cells (ASCs) in vitro and apply it in vivo in a rat ventral hernia repair model.

STUDY DESIGN

ASCs adherence was examined by confocal microscopy and proliferation rate was measured by growth curves. Multipotency of ASCs seeded onto SIS was tested using adipogenic, chondrogenic, and osteogenic induction media. For in vivo testing, midline abdominal musculofascial and peritoneal defects were created in Sprague-Dawley rats. Samples were evaluated for tensile strength, histopathology and immunohistochemistry.

RESULTS

All test groups showed cell adherence and proliferation on SIS. Fibronectin-treated scaffolds retained more cells than those treated with vehicle alone (p < 0.05). Fresh stromal vascular fraction (SVF) pellets containing ASCs were injected onto the SIS scaffold and showed similar results to cultured ASCs. Maintenance of multipotency on SIS was confirmed by lineage-specific markers and dyes. Histopathology revealed neovascularization and cell influx to ASC-seeded SIS samples following animal implantation. ASC-seeded SIS appeared to offer a stronger repair than plain SIS, but these results were not statistically significant. Immunohistochemistry showed continued presence of cells of human origin in ASC-seeded repairs at 1 month postoperation.

CONCLUSION

Pretreatment of the scaffold with fibronectin offers a method to increase cell adhesion and delivery. ASCs maintain their immunophenotype and ability to differentiate while on SIS. Seeding freshly isolated SVF onto the scaffold demonstrated that minimally manipulated cells may be useful for perioperative surgical applications within the OR suite. We have shown that this model for a "living mesh" can be successfully used in abdominal wall reconstruction.

Engineering muscle tissue for the fetus: getting ready for a strong life

Congenital malformations frequently involve either skeletal, smooth or cardiac tissues. When large parts of those tissues are damaged, the repair of the malformations is challenged by the fact that so much autologous tissue is missing. Current treatments require the use of prostheses or other therapies and are associated with a significant morbidity and mortality. Nonetheless, affected children have generally good survival rates and mostly normal schooling. As such, new therapeutic modalities need to represent significant improvements with clear safety profiles. Regenerative medicine and tissue engineering technologies have the potential to dramatically improve the treatment of any disease or disorder involving a lack of viable tissue. With respect to congenital soft tissue anomalies, the development of, for example, implantable muscle constructs would provide not only the usual desired elasticity and contractile proprieties, but should also be able to grow with the fetus and/or in the postnatal life. Such an approach would eliminate the need for multiple surgeries. However, the more widespread clinical applications of regenerative medicine and tissue engineering technologies require identification of the optimal indications, as well as further elucidation of the precise mechanisms and best methods (cells, scaffolds/biomaterials) for achieving large functional tissue regeneration in those clinical indications. In short, despite some amazing scientific progress, significant safety and efficacy hurdles remain. However, the rapid preclinical advances in the field bode well for future applications. As such, translational researchers and clinicians alike need be informed and prepared to utilize these new techniques for the benefit of their patients, as soon as they are available. To this end, we review herein, the clinical need(s), potential applications, and the relevant preclinical studies that are currently guiding the field toward novel therapeutics.

Preparation and properties of cyclic acetal based biodegradable gel by thiol-ene photopolymerization

Synthetic, hydrolytically degradable biomaterials have been widely developed for biomedical use; however, most of them will form acidic products upon degradation of polymer backbone. In order to address this concern, we proposed to fabricate a biodegradable gel based on the crosslinking of a cyclic acetal monomer with reactable diallyl group and multifunctional thiols by thiol-ene photopolymerization. This gel produces diols and carbonyl end groups upon hydrolytic degradation and could be entirely devoid of acidic by-products. Real time infrared spectroscopy was employed to investigate the effect of different light intensities and concentrations of photoinitiator on the polymerization kinetics. With the increase of the concentration of photoinitiator and light intensity, both the rate of polymerization and final double bond conversion increased. Degradation of cyclic acetal based networks was investigated in PBS medium so as to simulate physiological conditions. The remaining mass of the materials after 25 days incubation was 84%. TGA analysis showed that the gels exhibited a typical weight loss (97.2%) at around 378 °C. In vitro cytotoxicity showed that the cyclic acetal based gels had non-toxicity to cell L-929 and had good biocompatibility.

Single-injection HPLC method for rapid analysis of a combination drug delivery system

Developing combination drug delivery systems (CDDS) is a challenging but necessary task to meet the needs of complex therapy regimes for patients. As the number of multi-drug regimens being administered increases, so does the difficulty of characterizing the CDDS as a whole. We present a single-step method for quantifying three model therapeutics released from a model hydrogel scaffold using high-performance liquid chromatography (HPLC). Poly(ethylene glycol) dimethacrylate (PEGDMA) hydrogel tablets were fabricated via photoinitiated crosslinking and subsequently loaded with model active pharmaceutical ingredients (APIs), namely, porcine insulin (PI), fluorescein isothiocyanate-labeled bovine serum albumin (FBSA), prednisone (PSE), or a combination of all three. The hydrogel tablets were placed into release chambers and sampled over 21 days, and APIs were quantified using the method described herein. Six compounds were isolated and quantified in total. Release kinetics based on chemical properties of the APIs did not give systematic relationships; however, PSE was found to have improved device loading versus PI and FBSA. Rapid analysis of three model APIs released from a PEGDMA CDDS was achieved with a direct, single-injection HPLC method. Development of CDDS platforms is posited to benefit from such analytical approaches, potentially affording innovative solutions to complex disease states.

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.

Biomedical Applications of Biodegradable Polymers

Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. Specifically, polymeric biomaterials that are biodegradable provide the significant advantage of being able to be broken down and removed after they have served their function. Applications are wide ranging with degradable polymers being used clinically as surgical sutures and implants. In order to fit functional demand, materials with desired physical, chemical, biological, biomechanical and degradation properties must be selected. Fortunately, a wide range of natural and synthetic degradable polymers has been investigated for biomedical applications with novel materials constantly being developed to meet new challenges. This review summarizes the most recent advances in the field over the past 4 years, specifically highlighting new and interesting discoveries in tissue engineering and drug delivery applications.

Effect of dilute gelatine on the ultrasonic thermally assisted synthesis of nano hydroxyapatite

A series of nano hydroxyapatite-gelatine composites with different dilute solutions of gelatine concentrations were synthesized by a thermally assisted low-power ultrasonic irradiation method. The gelatine hydroxyapatite, (Gel-HAP) nanoparticles were prepared using Ca(NO(3))(2) and KH(2)PO(4) in the presence of gelatine in an aqueous solution. The synthesised products were heat treated between 100 and 400°C. The effect of the addition of gelatine on the nucleation and growth of synthesised nano HAP was investigated. Characterisation was performed using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared spectroscopy (FT-IR). The characterisation results indicate that gelatine has been appended to the nano HAP forming regular spherical shaped crystals of nano sized Gel-HAP.

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.

Porous EH and EH-PEG scaffolds as gene delivery vehicles to skeletal muscle

PURPOSE

Synthetic biomaterials are widely used in an attempt to control the cellular behavior of regenerative tissues. This can be done by altering the chemical and physical properties of the polymeric scaffold to guide tissue repair. This paper addresses the use of a polymeric scaffold (EH network) made from the cyclic acetal monomer, 5-ethyl-5-(hydroxymethyl)-β,β-dimethyl-1,3-dioxane-2-ethanol diacrylate (EHD), as a release device for a therapeutic plasmid encoding for an insulin-like growth factor-1 green fluorescent protein fusion protein (IGF-1 GFP).

METHODS

Scaffolds were designed to have different porous architectures, and the impact of these architectures on plasmid release was determined. We hypothesized that IGF-1 could be delivered more effectively using a porous scaffold to allow for the release of IGF-1.

RESULTS

We showed that by altering the number of pores exposed to the surface of the network, faster plasmid loading and release were achieved. In addition, the IGF-1 GFP plasmids were found to be effective in producing IGF-1 and GFP within human skeletal muscle myoblast cell cultures.

CONCLUSIONS

This work aims to show the utility of EH biomaterials for plasmid delivery for potentially localized skeletal muscle regeneration.

Macroporous hydrogel scaffolds and their characterization by optical coherence tomography

A simple porogen-leaching method to fabricate macroporous cyclic acetal hydrogel cell scaffolds is presented. Optical coherence tomography (OCT) was applied for nondestructive imaging and quantitative characterization of the scaffold structures. High-resolution OCT reveals the microstructures of the engineered tissue scaffolds in three dimensions. It also enables subsequent image processing to investigate quantitatively several key morphological design parameters for macroporous scaffolds, including the volume porosity, pore interconnectivity, and pore size. Two image-processing algorithms were adapted: three-dimensional labeling was applied to assess the interconnectivity, and erosion was applied to assess the pore size. Scaffolds with different design parameters were imaged, characterized, and compared. OCT imaging and image processing successfully discriminated scaffolds made from different formulations in terms of volume porosity, interconnectivity, and pore size. The cell viability and their spread across the scaffolds were confirmed by the fluorescence microscopy co-registered with OCT.

Human peritoneal membrane reduces the formation of intra-abdominal adhesions in ventral hernia repair: experimental study in a chronic hernia rat model

BACKGROUND

Adhesions leading to intestinal obstructions and fistulae are severe complications related to the intraperitoneal placement of synthetic meshes. This study evaluated the efficacy of human peritoneal membrane (HPM) in a chronic hernia repair rat model as an anti-adhesive solution for preventing the development of intra-abdominal adhesions.

MATERIALS AND METHODS

The mechanical properties of HPM and human fascia lata (HFL) were evaluated prior to in vivo implantation. Twenty rats underwent midline laparotomy, which led to the development of chronic hernias 28 d later. Then, animals underwent incisional hernia repair in an underlay fashion (n=5/mesh group) with compressed poly(tetra-fluoro-ethylene) (cPTFE), onto which HPM or HFL were affixed pre-repair, along with two additional controls. The extent and tenacity of intra-abdominal adhesions were determined through qualitative gross evaluations and quantitative tensiometry at 30 d post-repair. The host tissue response was evaluated histologically.

RESULTS

In hydrated state, the elastic properties of HPM were superior to HFL. Repairs with HPM had significantly less surface area covered by adhesions, with significantly lower tenacity compared with all other groups. Furthermore, intra-abdominal adhesions developed in the presence of HPM were associated with omentum only, and were distributed around the perimeter of the exposed cPTFE. HPM served as an active tissue remodeling template, replacing the traditional foreign body encapsulation with an anatomically and physiologically superior outcome.

CONCLUSIONS

HPM significantly reduces the extent and tenacity of intra-abdominal adhesion formation, and represents a bioprosthetic template that encourages structural and functional neo peritonealization.

A hierarchical response of cells to perpendicular micro- and nanometric textural cues

In this paper, we report on the influence of shallow micro- and nanopatterned substrata on the attachment and behavior of a human fibroblast [human telomerase transfected immortalized (hTERT)] cells. We identify a hierarchy of textural guidance cues with respect to cell alignment on these substrates. Cells were seeded and cultured for 48 h on silicon substrates patterned with two linear textures overlaid at 90 degrees, both with 24 microm pitch: a micrograting and a nanopattern of rows of 140- nm-diameter pits arranged in a rectangular array with 300 nm centre-to-centre spacing. The cell response to these textures was shown to be highly dependent on textural feature dimensions. We show that cells align to the stripes of nanopits. Stripes of 30-nm deep nanopits were also shown to elicit a stronger response from cells than 160-nm deep nanopits.

Skeletal muscle tissue engineering approaches to abdominal wall hernia repair

Abdominal wall hernias resulting from prior incisions are a common surgical complication affecting hundreds of thousands of Americans each year. The negative consequences associated with abdominal hernias may be considerable, including pain, bowel incarceration, vascular disruption, organ loss, and death. Current clinical approaches for the treatment of abdominal wall hernias focus on the implantation of permanent biomaterial meshes or acellular xenografts. However, these approaches are not infrequently associated with postoperative infections, chronic sinuses, or small bowel obstruction. Furthermore, the most critical complication, hernia recurrence, has been well described and may occur in a large percentage of patients. Despite many advances in repair techniques, wound healing and skeletal muscle regeneration is limited in many cases, resulting in a decrease in abdominal wall tissue function and contributing to the high hernia recurrence rate. This review will give an overview of skeletal muscle anatomy, skeletal muscle regeneration, and herniation mechanisms, as well as discuss the current and future clinical solutions for abdominal wall hernia repair.