Biomimetic In Vitro Model of Cell Infiltration into Skin Scaffolds for Pre-Screening and Testing of Biomaterial-Based Therapies

The use of artificial dermal substitutes for repair of the donor site following harvesting of a radial forearm free flap: A systematic review

BACKGROUND

Artificial dermal substitutes (ADMs) have been trialled to improve outcomes at the donor site following the harvesting of a radial forearm free flap (RFFF). This systematic review compares donor site aesthetic and functional outcomes, with the use of an ADM versus conventional practice.

METHODS

The databases Medline, Embase, Cochrane Library, Web of Science (Core Collection), and Scopus were searched for retrospective, prospective, and case-control studies and randomised control trials (RCTs) involving any ADM. Studies with adult patients having undergone RFFF harvesting and donor site repair with an ADM, commenting on appropriate clinical outcomes and without high risk of bias, were included. Direction-of-effect analysis was performed on relevant groupings of studies since heterogeneity in outcome measurement precluded meta-analyses.

RESULTS

Across eight non-comparative studies included, 132 patients had donor site coverage with AlloDerm™, Integra™, Matriderm™, or Rapiderm. Across 11 comparative studies included, 240 patients had donor site coverage with fish-skin matrix, AlloDerm™, amniotic membrane, MegaDerm™, Hyalomatrix, Integra™, or Matriderm™. Five out of 11 comparative studies demonstrated superior aesthetic outcomes with ADMs according to at least one aesthetic metric compared to controls, whilst 6/11 demonstrated superior functional outcomes with ADMs. No study demonstrated poorer aesthetic or functional outcomes with an ADM compared to conventional practice.

CONCLUSIONS

In summary, the lack of studies reporting poorer outcomes with them compared to conventional practices, and a cumulative effect direction in their favour, provide strong indications in support of the use of AlloDerm™, Integra™, or Matriderm™ grafts. Further comparative studies, including RCTs, are needed to reinforce these initial indications.

Comparison of Decellularized Human Dermal Scaffolds versus Bovine Collagen/Elastin Matrices for Engineering of Soft-Tissue Flaps

BACKGROUND

Free flap-based soft-tissue reconstruction comes at the price of donor-site morbidity. The arteriovenous loop (AVL) technique can overcome this issue by allowing for the de novo generation of axially vascularized soft-tissue flaps from vein grafts embedded into different matrices. Application of the AVL technique has been limited by insufficient long-term volume retention and poor tissue stability. The authors investigated the suitability of a novel human dermal scaffold to improve volume retention and tissue stability.

METHODS

AVLs were created in 28 immunocompetent rats and embedded in either decellularized human dermal scaffolds (experimental group, n = 14) (Epiflex) or bovine collagen/elastin matrices (control group, n = 14) (MatriDerm) in subcutaneous polytetrafluoroethylene chambers. The weight and volume of engineered tissues, the extent of angiogenesis, and the proportion of proliferating cells were compared between groups on postoperative days (PODs) 21 and 28 by means of immunohistochemistry and micro-computed tomography.

RESULTS

On POD 28, both groups displayed homogeneous microvascular networks on histopathology and micro-computed tomography. Mean microvessel counts and surface areas and the percentage of proliferating cells did not differ between the groups. However, the experimental human scaffold group displayed significantly smaller volume loss and significantly less tissue degradation compared with bovine matrix controls (volume retention, 102% ± 5% versus 27% ± 7% on POD 21, and 79% ± 12% versus 12% ± 7% on POD 28, respectively; P < 0.0001).

CONCLUSION

Compared with bovine matrices, decellularized human scaffolds allow for superior volume retention and tissue stability of de novo engineered soft-tissue AVL flaps in rats.

CLINICAL RELEVANCE STATEMENT

AVLs allow for the de novo generation of vascularized soft-tissue flaps. However, insufficient long-term volume retention is still an issue. The authors' study shows that decellularized human matrices guarantee superior volume stability of de novo grown soft-tissue flaps in rats.

Use of single-layer artificial dermal template in patients with trauma and burns

Objective:

Artificial dermal templates (ADTs), were designed initially to provide extracellular matrix and skin substitute for extensive burn injuries. Use of ADTs in a variety of other indications, has also been described in the literature. In this study, we describe our experience of using ADTs for different indications in burn contractures and wound coverage.

Method:

In this retrospective study, patients requiring burn scar contracture release, permanent wound coverage for acute traumatic wounds and temporary wound coverage to prepare for complex reconstructions, and where the ADT Pelnac (Gunze Ltd., Japan) was applied, were evaluated. Data regarding patient sex, age, type and location of injury, comorbidities, operations and complications were recorded.

Results:

A total of 24 patients were included in the study, of whom 12 patients were operated on for burn contractures. ADTs were used with split-thickness skin grafts (STSGs) or Z-plasties in a single-stage procedure. In six patients, ADT and STSGs were used to cover defects with exposed bone or tendon. Of the patients, six had their wounds covered temporarily while they were stabilised for complex reconstructions or were awaiting definitive histopathological results. Revisional surgeries due to graft failures or insufficient contracture releases were required by 12 patients. All temporary wound coverage patients had successful flap reconstructions after stabilisation of their general status, had tumour-free margins in the histopathological examination, and no necrosis or infection was seen on follow-up.

Conclusion:

In this study, ADTs had positive effects on selected patients, but comprehensive and comparative clinical studies are needed for different indications to choose between these templates.

Multi-functional nanocellulose-chitosan dressing loaded with antibacterial lawsone for rapid hemostasis and cutaneous wound healing

Cutaneous wounds accompanied by massive bleeding, bacterial infections might be lethal and cause fundamental therapeutic impediments in clinical fields. As part of the push for a solution, biomaterial having hemostatic-antibacterial features is highly desirable. Inspired by this concept, freeze dried sponges were developed followed by combining tempo-oxidized nanocellulose (TOCN), chitosan using EDC/NHS cross-linker with antibacterial lawsone loading for controlled delivery of this compound during wound healing. The pore diameter decreased upon increasing chitosan (2.5, 3.5, 4.5, 5.5% w/v) while TOCN ensured scaffold's mechanical stability. The in vitro degradation, lawsone release from fibroblast cell-compatible sponge was faster in acidic pH 5.5 than physiologic pH 7.4 indicating adaptability to physiological skin milieu of wounds. The rat tail amputation model, 14 days rat full-thickness cutaneous-wound model ensured hemostasis, dramatic wound closure after TLC4.5 (optimized scaffold) treatment suggesting its potential as functional wound healing substitute showing obvious avenue for hemostatis and skin tissue reconstruction arena.

Realizing tissue integration with supramolecular hydrogels

Biomaterial matrices must permit tissue growth and maturation for the success of tissue regeneration strategies. Naturally, this accommodation is achieved via the dynamic remodeling of a cell's extracellular matrix (ECM). Synthetically, hydrolytic or enzymatic degradation are often engineered into materials for this purpose. More recently, supramolecular interactions have been used to provide a biomimetic and tunable mechanism to facilitate tissue formation via their dynamic and reversible non-covalent interactions. By engineering the mechanical and bioactive properties of a material, supramolecular chemists are able to design permissivity into the construct and facilitate tissue integration in-vivo. Furthermore, via the reversibility of non-covalent interactions, injectability and responsiveness can be designed for enhanced delivery and spatio-temporal control. In this review, we delineate the basic considerations needed when designing permissive supramolecular hydrogels for tissue engineering with an eye toward tissue growth and integration. We highlight three archetypal hydrogel systems that have shown well-documented tissue integration in vivo, and provide avenues to assess tissue in-growth. Careful design and assessment of the biomedical potential of a supramolecular hydrogels can inspire the creation of robust and dynamic implants for new tissue engineering applications.