Stromal vascular fraction cells as biologic coating of mesh for hernia repair

Background

The interest in non-manipulated cells originating from adipose tissue has raised tremendously in the field of tissue engineering and regenerative medicine. The resulting stromal vascular fraction (SVF) cells have been successfully used in numerous clinical applications. The aim of this experimental work is, first to combine a macroporous synthetic mesh with SVF isolated using a mechanical disruption process, and to assess the effect of those cells on the early healing phase of hernia.

Methods

Human SVF cells combined with fibrin were used to coat commercial titanized polypropylene meshes. In vitro, viability and growth of the SVF cells were assessed using live/dead staining and scanning electron microscopy. The influence of SVF cells on abdominal wall hernia healing was conducted on immunodeficient rats, with a focus on short-term vascularization and fibrogenesis.

Results

Macroporous meshes were easily coated with SVF using a fibrin gel as temporary carrier. The in vitro experiments showed that the whole process including the isolation of human SVF cells and their coating on PP meshes did not impact on the SVF cells’ viability and on their capacity to attach and to proliferate. In vivo, the SVF cells were well tolerated by the animals, and coating mesh with SVF resulted in a decrease degree of vascularity compared to control group at day 21.

Conclusions

The utilization of SVF-coated mesh influences the level of angiogenesis during the early onset of tissue healing. Further long-term animal experiments are needed to confirm that this effect correlates with a more robust mesh integration compared to non-SVF-coated mesh.

Infections associated with mesh repairs of abdominal wall hernias: Are antimicrobial biomaterials the longed-for solution?

The incidence of mesh-related infection after abdominal wall hernia repair is low, generally between 1 and 4%; however, worldwide, this corresponds to tens of thousands of difficult cases to treat annually. Adopting best practices in prevention is one of the keys to reduce the incidence of mesh-related infection. Once the infection is established, however, only a limited number of options are available that provides an efficient and successful treatment outcome. Over the past few years, there has been a tremendous amount of research dedicated to the functionalization of prosthetic meshes with antimicrobial properties, with some receiving regulatory approval and are currently available for clinical use. In this context, it is important to review the clinical importance of mesh infection, its risk factors, prophylaxis and pathogenicity. In addition, we give an overview of the main functionalization approaches that have been applied on meshes to confer anti-bacterial protection, the respective benefits and limitations, and finally some relevant future directions.

Drug delivery systems functionalized with bone mineral seeking agents for bone targeted therapeutics

The systemic administration of drugs to treat bone diseases is often associated with poor uptake of the drug in the targeted tissue, potential systemic toxicity and suboptimal efficacy. In order to overcome these limitations, many micro- and nano-sized drug carriers have been developed for the treatment of bone pathologies that exhibit specific affinity for bone. Drug carriers can be functionalized with bone mineral seekers (BMS), creating a targeted drug delivery system (DDS) which is able to bind to bone and release therapeutics directly at the site of interest. This class of advanced DDS is of tremendous interest due to their strong affinity to bone, with great expectation to treat life-threatening bone disorders such as osteomyelitis, osteosarcoma or even osteoporosis. In this review, we first explain the mechanisms behind the affinity of several well-known BMS to bone, and then we present several effective approaches allowing the incorporation BMS into advanced DDS. Finally, we report the therapeutic applications of BMS based DDS under development or already established. Understanding the mechanisms behind the biological activity of recently developed BMS and their integration into advanced therapeutic delivery systems are essential prerequisites for further development of bone-targeting therapies with optimal efficacy.

Surface-enrichment with hydroxyapatite nanoparticles in stereolithography-fabricated composite polymer scaffolds promotes bone repair

Fabrication of composite scaffolds using stereolithography (SLA) for bone tissue engineering has shown great promises. However, in order to trigger effective bone formation and implant integration, exogenous growth factors are commonly combined to scaffold materials. In this study, we fabricated biodegradable composite scaffolds using SLA and endowed them with osteopromotive properties in the absence of biologics. First we prepared photo-crosslinkable poly(trimethylene carbonate) (PTMC) resins containing 20 and 40wt% of hydroxyapatite (HA) nanoparticles and fabricated scaffolds with controlled macro-architecture. Then, we conducted experiments to investigate how the incorporation of HA in photo-crosslinked PTMC matrices improved human bone marrow stem cells osteogenic differentiation in vitro and kinetic of bone healing in vivo. We observed that bone regeneration was significantly improved using composite scaffolds containing as low as 20wt% of HA, along with difference in terms of osteogenesis and degree of implant osseointegration. Further investigations revealed that SLA process was responsible for the formation of a rich microscale layer of HA corralling scaffolds. To summarize, this work is of substantial importance as it shows how the fabrication of hierarchical biomaterials via surface-enrichment of functional HA nanoparticles in composite polymer stereolithographic structures could impact in vitro and in vivo osteogenesis.

STATEMENT OF SIGNIFICANCE

This study reports for the first time the enhance osteopromotion of composite biomaterials, with controlled macro-architecture and microscale distribution of hydroxyapatite particles, manufactured by stereolithography. In this process, the hydroxyapatite particles are not only embedded into an erodible polymer matrix, as reported so far in the literature, but concentrated at the surface of the structures. This leads to robust in vivo bone formation at low concentration of hydroxyapatite. The reported 3D self-corralling composite architecture provides significant opportunities to develop functional biomaterials for bone repair and tissue engineering.

Fabrication of silk mesh with enhanced cytocompatibility: preliminary in vitro investigation toward cell-based therapy for hernia repair

Recent studies have demonstrated that combining cells with meshes prior to implantation successfully enhanced hernia repair. The idea is to create a biologic coating surrounding the mesh with autologous cells, before transplantation into the patient. However, due to the lack of a prompt and robust cell adhesion to the meshes, extensive in vitro cultivation is required to obtain a homogenous cell layer covering the mesh. In this context, the objective of this publication is to manufacture meshes made of silk fibres and to enhance the cytoadhesion and cytocompatibility of the biomaterial by surface immobilization of a pro-adhesive wheat germ agglutinin (lectin WGA). We first investigated the affinity between the glycoprotein WGA and cells, in solution and then after covalent immobilization of WGA on silk films. Then, we manufactured meshes made of silk fibres, tailored them with WGA grafting and finally evaluated the cytocompatibility and the inflammatory response of silk and silk-lectin meshes compared to common polypropylene mesh, using fibroblasts and peripheral blood mononuclear cells, respectively. The in vitro experiments revealed that the cytocompatibility of silk can be enhanced by surface immobilization with lectin WGA without exhibiting negative response in terms of pro-inflammatory reaction. Grafting lectin to silk meshes could bring advantages to facilitate cell-coating of meshes prior to implantation, which is an imperative prerequisite for abdominal wall tissue regeneration using cell-based therapy.

Role of chemical communication and behavioural interactions among conspecifics in the choice of shelters by the cave-dwelling salamander Proteus anguinus (Caudata, Proteidae)

Non-sexually active males and females of the cave-dwelling salamander Proteus anguinus always aggregate in the same shelters, either under stones or in fissures. However, it was not known if this behaviour results from chemical communication and (or) behavioural interactions among conspecifics. I tested the hypothesis that this is the case by using two-choice tests. The results showed that salamanders re-located their own shelter even when it was displaced. However, they preferred a shelter that belonged to a conspecific or contained faecal pellets of a conspecific to their own or a control "blank" shelter. When two salamanders were simultaneously given the choice between two blank shelters, they cohabited. When they were simultaneously given the choice between their own shelter and each other's, they used them indiscriminately and frequently cohabited. These data provide evidence that P. anguinus use chemical signals as directional cues for homing and also for social behaviour. Chemical signals may attract conspecifics, which subsequently may exhibit gregarious behaviour by occupying common shelters.