The diamond CO2 laser as a method of improving the vascularisation of a permanent collagen implant

Histological Comparison of Implanted Cadaveric and Porcine Dermal Matrix Grafts

OBJECTIVES: Histological comparison of human-based (AlloDerm) and porcine-based (ENDURAGen) dermal matrices regarding tissue incorporation and neovascularization as potential soft tissue augmentation materials.

STUDY DESIGN: In vivo, rat model.

METHODS: Subcutaneous implantation of 1-mm thick, 1 cm X 1 cm pieces of AlloDerm, ENDURAGen, and meshed ENDURAGen was performed in 24 Sprague Dawley rats. Implant materials were harvested at 4 (n = 12) and 8 weeks (n = 12). Histological quantification of soft tissue ingrowth and microvascular density was performed following hematoxylin-eosin staining and CD34 immunohistochemistry, respectively.

RESULTS: AlloDerm showed significantly greater soft tissue in-growth and microvascular density compared with both ENDURAGen and meshed ENDURAGen at 4 and 8 weeks ( P < 0.001).

CONCLUSIONS: Although these results may differ in human host tissues, AlloDerm seems to be a more suitable dermal matrix implant than ENDURAGen for cases in which tissue incorporation and neovascularization are sought for the optimal outcome based on this animal model.

Cytotoxicity testing of scaffolds potentially suitable for the preparation of three-dimensional skin substitutes

The preparation and study of three-dimensional functional skin substitutes has been the focus of intense research for several decades. Dermal substitutes are now commonly used in medical practice for a variety of applications. Here, we assess the toxicity of seven selected acellular dermal matrix materials to establish their potential for use in future three-dimensional skin substitute studies. The cytotoxicity of acellular dermis (of Allo- and Xenograft origin) prepared in our lab and biomaterials based on collagen and hyaluronic acid (Coladerm H and Coladerm H-L) were compared to that seen in three commercially available products (Xe-Derma, AlloDerm and Xeno-Impl). Murine fibroblasts NIH-3T3 and human dermal fibroblasts were used in cytotoxicity tests, with any resultant cytotoxic effects caused by the seven tested dermal scaffolds visualised using an inverted microscope system and confirmed in parallel using colorimetric MTT cell proliferation assays. While most of the dermal substitutes did not demonstrate a cytotoxic effect on our two cell types, Xeno and Xeno-Impl scaffolds clearly did. The cytotoxic effect of acellular Xeno dermal matrix could essentially be removed through a regime of multiple washes, but we were unable to remove the cytotoxic effect of Xeno-Impl. Thus, Xeno-Impl alone has been excluded from our future work on preparation of 3D skin substitutes.

A review of tissue-engineered skin bioconstructs available for skin reconstruction

Situations where normal autografts cannot be used to replace damaged skin often lead to a greater risk of mortality, prolonged hospital stay and increased expenditure for the National Health Service. There is a substantial need for tissue-engineered skin bioconstructs and research is active in this field. Significant progress has been made over the years in the development and clinical use of bioengineered components of the various skin layers. Off-the-shelf availability of such constructs, or production of sufficient quantities of biological materials to aid rapid wound closure, are often the only means to help patients with major skin loss. The aim of this review is to describe those materials already commercially available for clinical use as well as to give a short insight to those under development. It seeks to provide skin scientists/tissue engineers with the information required to not only develop in vitro models of skin, but to move closer to achieving the ultimate goal of an off-the-shelf, complete full-thickness skin replacement.

Use of a novel porcine collagen paste as a dermal substitute in full-thickness wounds

A commercially available porcine collagen sheet material has been found previously to be useful as an implant for reconstructive surgery. However, its use as a dermal substitute has been hindered by slow cell penetration and vascularization. A novel paste formulation of this material was investigated for its potential role as a dermal substitute in full-thickness wounds. A porcine punch biopsy model was initially used to assess the integration of a wide range of material formulations. Selected formulations were then assessed further in a larger wound-chamber model. Paste formulations were compared with those of sheet and another commercially available dermal regeneration template. The porcine collagen paste became integrated into full-thickness wounds without rejection and without excessive inflammation. It was detected in wounds up to day 27 postimplantation. Porcine collagen paste was readily infiltrated by host cells by day 2 and supported migrating keratinocytes on its surface. Staining for endothelial cells indicated neovasculature formation as early as day 4 and functional newly formed microvessels were noted at day 7. This was comparable with neovascularization of an alternative and clinically proven dermal regeneration template and was significantly superior to the sheet material formulation at the same time points. Our findings suggest that porcine collagen paste may be suitable as an alternative to current dermal substitutes in full-thickness wounds.

Extracellular matrix bioscaffolds for orthopaedic applications. A comparative histologic study

BACKGROUND

Biologic scaffold materials prepared from extracellular matrix are currently available for the surgical repair of damaged or missing musculotendinous tissue. These scaffolds differ in their species and tissue of origin, methods of processing, and methods of terminal sterilization. The purpose of the present study was to evaluate the host-tissue morphologic response to five commercially available extracellular matrix-derived biologic scaffolds used for orthopaedic soft-tissue repair in a rodent model.

METHODS

One hundred twenty-six Sprague-Dawley rats were divided into six groups of twenty-one animals each. A defect was created in the musculotendinous tissue of the abdominal wall of each animal and then was repaired with one of five different scaffold materials (GraftJacket, Restore, CuffPatch, TissueMend, Permacol) or with the excised autologous tissue. Three animals from each group were killed at one of seven time-points after surgery (two, four, seven, fourteen, twenty-eight, fifty-six, and 112 days), and the specimens were examined with histologic and morphologic methods. The degree of cellular infiltration, multinucleated giant cell presence, vascularity, and organization of the replacement connective tissue were evaluated with semiquantitative methods.

RESULTS

Each device elicited a distinct morphologic response that differed with respect to cellularity (p<0.001), vascularity (p<0.01), the presence of multinucleated giant cells (p<0.01), and organization of the remodeled tissue (p<0.01) at or after the Day 7 time-point. More rapidly degraded devices such as Restore and autologous tissue showed the greatest amount of cellular infiltration, especially at the early time-points. Devices that degraded slowly, such as CuffPatch, TissueMend, and Permacol, were associated with the presence of foreign-body giant cells, chronic inflammation, and/or the accumulation of dense, poorly organized fibrous tissue.

CONCLUSIONS

Biologic scaffold materials composed of extracellular matrix elicit distinct host-tissue histologic and morphologic responses, depending on species of origin, tissue of origin, processing methods, and/or method of terminal sterilization.

Regenerative medicine and developmental biology: the role of the extracellular matrix

The principles and ultimate goals of regenerative medicine and developmental biology involve a complex sequence of events, culminating in the formation of structurally and functionally normal tissues and organs. The molecular composition of the extracellular matrix (ECM) plays a critical role in cellular migration and differentiation events. Mammalian ECM, derived from various tissues and organs, has been used as a biologic scaffold for therapeutic regenerative applications. Hundreds of thousands of human patients have benefited from the use of biologic scaffolds composed of naturally occurring ECM. The mechanisms by which ECM induces constructive remodeling instead of scar tissue formation are only beginning to be understood. This article reviews composition of mammalian ECM, its poorly understood role in developmental biology, and the clinical applications that have resulted from the use of this naturally occurring scaffold.