Full-Thickness Oral Mucoperiosteal Defects: Challenges and Opportunities

Regenerative engineering strategies for the oral mucoperiosteum, as may be needed following surgeries, such as cleft palate repair and tumor resection, are underdeveloped compared with those for maxillofacial bone. However, critical-size tissue defects left to heal by secondary intention can lead to complications, such as infection, fistula formation, scarring, and midface hypoplasia. This review describes current clinical practice for replacing mucoperiosteal tissue, including autografts and allografts. Potentially paradigm-shifting experimental regenerative engineering strategies for mucoperiosteal wound healing, such as hybrid grafts and engineered matrices, are also discussed. Throughout the review, the advantages and disadvantages of each replacement or regeneration strategy are outlined in the context of clinical outcomes, quality of life for the patient, availability of materials, and cost of care. Finally, future directions for research and development in the area of mucoperiosteum repair are proposed, with an emphasis on identifying globally available and affordable solutions for promoting mucoperiosteal regeneration. Impact statement Unassisted oral mucoperiosteal wound healing can lead to severe complications such as infection, fistulae, scarring, and developmental abnormalities. Thus, strategies for promoting wound healing must be considered when mucoperiosteal defects are incident to oral surgery, as in palatoplasty or tumor resection. Emerging mucoperiosteal tissue engineering strategies, described in this study, have the potential to overcome the limitations of current standard-of-care donor tissue grafts. For example, the use of engineered mucoperiosteal biomaterials could circumvent concerns about tissue availability and immunogenicity. Moreover, employment of tissue engineering strategies may improve the equity of oral wound care by increasing global affordability and accessibility of materials.

Which substances loaded onto collagen scaffolds influence oral tissue regeneration?-an overview of the last 15 years

BACKGROUND

Collagen scaffolds are widely used for guided bone or tissue regeneration. Aiming to enhance their regenerative properties, studies have loaded various substances onto these scaffolds. This review aims to provide an overview of existing literature which conducted in vitro, in vivo, and clinical testing of drug-loaded collagen scaffolds and analyze their outcome of promoting oral regeneration.

MATERIALS AND METHODS

PubMed, Scopus, and Ovid Medline® were systematically searched for publications from 2005 to 2019. Journal articles assessing the effect of substances on oral hard or soft tissue regeneration, while using collagen carriers, were screened and qualitatively analyzed. Studies were grouped according to their used substance type-biological medical products, pharmaceuticals, and tissue-, cell-, and matrix-derived products.

RESULTS

A total of 77 publications, applying 36 different substances, were included. Collagen scaffolds were demonstrating favorable adsorption behavior and release kinetics which could even be modified. BMP-2 was investigated most frequently, showing positive effects on oral tissue regeneration. BMP-9 showed comparable results at lower concentrations. Also, FGF2 enhanced bone and periodontal healing. Antibiotics improved the scaffold's anti-microbial activity and reduced the penetrability for bacteria.

CONCLUSION

Growth factors showed promising results for oral tissue regeneration, while other substances were investigated less frequently. Found effects of investigated substances as well as adsorption and release properties of collagen scaffolds should be considered for further investigation.

CLINICAL RELEVANCE

Collagen scaffolds are reliable carriers for any of the applied substances. BMP-2, BMP-9, and FGF2 showed enhanced bone and periodontal healing. Antibiotics improved anti-microbial properties of the scaffolds.

Current and upcoming therapies to modulate skin scarring and fibrosis

Skin is the largest organ of the human body. Being the interface between the body and the outer environment, makes it susceptible to physical injury. To maintain life, nature has endowed skin with a fast healing response that invariably ends in the formation of scar at the wounded dermal area. In many cases, skin remodelling may be impaired, leading to local hypertrophic scars or keloids. One should also consider that the scarring process is part of the wound healing response, which always starts with inflammation. Thus, scarring can also be induced in the dermis, in the absence of an actual wound, during chronic inflammatory processes. Considering the significant portion of the population that is subject to abnormal scarring, this review critically discusses the state-of-the-art and upcoming therapies in skin scarring and fibrosis.

Lack of interferon-gamma attenuates foreign body reaction to subcutaneous implants in mice

Subcutaneous implantation of synthetic materials and biomedical devices often induces abnormal tissue healing - the foreign body reaction-which impairs their function. In particular, Interferon-γ (IFN-γ) is a critical endogenous mediator of inflammation and plays a key role in a wide variety of biological responses including tissue healing. However, the contribution of endogenous IFN-γ on different features of the foreign body response induced by synthetic implants regarding neovascularization, inflammation, and fibrogenesis is not well known. Here, we evaluated inflammatory angiogenesis and fibrogenesis induced by implantation of polyether-polyurethane sponges in mice targeted disrupted of the interferon-γ gene (IFN-γ^-/- ) and wild-type (WT). The hemoglobin content, the number of vessels, and blood flow (evaluated by LDPI-laser Doppler perfusion imaging) were decreased in the implants from IFN-γ^-/- as compared to WT mice. Likewise, neutrophils and macrophages accumulation (MPO and NAG activities, respectively) was decreased in IFN-γ^-/- implants. Interestingly, while the local content of VEGF, TNF-α, CXCL-1/KC, as measured by ELISA, and iNOS expression, as measured by qPCR, were significantly reduced, the content of IL-10 was greatly increased in the implants from IFN-γ^-/- mice as compared to WT mice. No alterations were observed in CCL-2/MCP-1 levels. Lastly, the collagen deposition, assessed by Picro-Sirius red-stained histological sections, was also reduced in IFN-γ^-/- implants. Altogether, these data suggest that IFN-γ activity contributes to inflammatory angiogenesis and fibrogenesis in synthetic implants and that lack of IFN-γ expression attenuates foreign body reaction to implants in mice. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2243-2250, 2018.

Collagen scaffolds in bone sialoprotein-mediated bone regeneration

Decades of research in bioengineering have resulted in the development of many types of 3-dimentional (3D) scaffolds for use as drug delivery systems (DDS) and for tissue regeneration. Scaffolds may be comprised of different natural fibers and synthetic polymers as well as ceramics in order to exert the most beneficial attributes including biocompatibility, biodegradability, structural integrity, cell infiltration and attachment, and neovascularization. Type I collagen scaffolds meet most of these criteria. In addition, type I collagen binds integrins through RGD and non-RGD sites which facilitates cell migration, attachment, and proliferation. Type I collagen scaffolds can be used for bone tissue repair when they are coated with osteogenic proteins such as bone morphogenic protein (BMP) and bone sialoprotein (BSP). BSP, a small integrin-binding ligand N-linked glycoprotein (SIBLING), has osteogenic properties and plays an essential role in bone formation. BSP also mediates mineral deposition, binds type I collagen with high affinity, and binds αvβ₃ and αvβ₅ integrins which mediate cell signaling. This paper reviews the emerging evidence demonstrating the efficacy of BSP-collagen scaffolds in bone regeneration.