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ECM biomaterials are a class of biomaterials derived from processing human or animal tissues to retain portions of the extracellular matrix. These materials are typically cell-free, distinguishing them from classical allografts and xenografts, can be integrated or incorporated into the body, and have been FDA approved for human use for more than 10 years in a wide range of clinical indications.〔Cornwell, K.G., Landsman, A., James, K.S. ''Extracellular Matrix Biomaterials for Soft Tissue Repair.'' Clin Podiatr Med Surg 26 (2009) 507–523 ((Original Article) )〕 ==Harvesting and Processing== All ECM samples originate from mammalian tissues, such as dermis, pericardium, and small intestinal submucosa (SIS).〔 After explantation from the source, the ECM biomaterial retains some characteristics of the original tissue.〔 The ECM tissues can be harvested from varying stages in the developmental stages in mammalian species such as human, porcine, equine, and bovine.〔 Although they are similarly composed of fibril collagen, the microstructure, specific composition (including presence of noncollageous protein and glycosaminoglycans and ratio of different types of collagen), physical dimensions and mechanical properties can differ.〔 Depending on the developmental stage of the tissue during which harvesting occurred, the microstructure can vary within an organism. Additionally, keeping in mind the size and shape of the final tissue, the potential of the physical dimensions of the tissue of origin must be considered.〔 Despite this “memory” of the ECM tissue, methods have been engineered so that these innate characteristics can be modified, saved or removed.〔 The modification process varies depending on the material used in clinical setting. Some ECM biomaterials undergo a modification that removes all the cells but leaves the remainder of the other ECM components called decellularization. Another process that can be introduced into the biomaterial is artificial crosslinking. Artificial crosslinking has been shown to stabilize reconstituted collagen, which can rapidly degenerate in vivo.〔 Although mechanical strength is gained, the artificial crosslinks that are added increase the chance for a host-cell rejection, due to its foreign origin.〔(Badylak S. "Host Response to Biomaterials" )〕 Due to this complication, intentional crosslinking is no longer practiced as more recent advancements have been made that increase the lifespan of the collagen without the use of artificial stabilization. Finally, to ensure the ECM biomaterial is without infectious bacteria and viruses, most are terminally sterilized.〔 This can include ethylene oxide (EO) gas, gamma irradiation, or electron beam (e-beam) irradiation as the sterilizing agent.〔 In all, the small variances from origin, time of harvest, and processing method can direct the final properties of the ECM biomaterial. Decellularized ECM biomaterials can be further processed into a fine powder and then lyophilized (freeze-dried). This powder can then be mixed with collagenase to form an ECM derived hydrogel (self-healing hydrogels). These hydrogels are then used in cell culture to help maintain cell phenotype and increase cell proliferation. Cells cultured on ECM hydrogels maintain their phenotype better than cells cultured on other substrates such as matrigel or type 1 collagen.〔Wolf MT, et al. "A hydrogel derived from decellularized dermal extracellular matrix"()〕〔Sawkins MJ, et al. "Hydrogels derived from demineralized and decellularized bone extracellular matrix"()〕 Though hydrogels do not yet have direct clinical relevance, they have shown promise as a method of assisting in organ regeneration.〔〔〔Barker TH "The role of ECM proteins and protein fragments in guiding cell behavior in regenerative medicine"()〕 Similarly, whole organs can be decellularized to create 3-D ECM scaffolds.〔Faulk DM, et al. "Role of the extracellular matrix in whole organ engineering" ()〕 These scaffolds can then be re-cellularized in an attempt to regenerate whole organs for transplant. This method works primarily for organs with a complex vasculature, as it allows detergent to be fully perfused through the material.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「ECM Biomaterial」の詳細全文を読む スポンサード リンク
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