Biologic scaffold materials composed of extracellular matrix (ECM) are typically derived by processes that involve decellularization of tissues or organs. Preservation of the complex composition and three-dimensional ultrastructure of the ECM is highly desirable but it is recognized that all methods of decellularization result in disruption of the architecture and potential loss of surface structure and composition. Physical methods and chemical and biologic agents are used in combination to lyse cells, followed by rinsing to remove cell remnants. Effective decellularization methodology is dictated by factors such as tissue density and organization, geometric and biologic properties desired for the end product, and the targeted clinical application. Tissue decellularization with preservation of ECM integrity and bioactivity can be optimized by making educated decisions regarding the agents and techniques utilized during processing. An overview of decellularization methods, their effect upon resulting ECM structure and composition, and recently described perfusion techniques for whole organ decellularization techniques are presented herein.

Biologic scaffolds composed of extracellular matrix (ECM) are commonly used repair devices in preclinical and clinical settings; however the use of these scaffolds for peripheral and central nervous system (CNS) repair has been limited. Biologic scaffolds developed from brain and spinal cord tissue have recently been described, yet the conformation of the harvested ECM limits therapeutic utility. An injectable CNS-ECM derived hydrogel capable of in vivo polymerization and conformation to irregular lesion geometries may aid in tissue reconstruction efforts following complex neurologic trauma. The objectives of the present study were to develop hydrogel forms of brain and spinal cord ECM and compare the resulting biochemical composition, mechanical properties, and neurotrophic potential of a brain derived cell line to a non-CNS-ECM hydrogel, urinary bladder matrix. Results showed distinct differences between compositions of brain ECM, spinal cord ECM, and urinary bladder matrix. The rheologic modulus of spinal cord ECM hydrogel was greater than that of brain ECM and urinary bladder matrix. All ECMs increased the number of cells expressing neurites, but only brain ECM increased neurite length, suggesting a possible tissue-specific effect. All hydrogels promoted three-dimensional uni- or bi-polar neurite outgrowth following 7 days in culture. These results suggest that CNS-ECM hydrogels may provide supportive scaffolding to promote in vivo axonal repair.

Acellular biologic scaffolds are commonly used to facilitate the constructive remodeling of three of the four traditional tissue types: connective, epithelial, and muscle tissues. However, the application of extracellular matrix (ECM) scaffolds to neural tissue has been limited, particularly in the central nervous system (CNS) where intrinsic regenerative potential is low. The ability of decellularized liver, lung, muscle, and other tissues to support tissue-specific cell phenotype and function suggests that CNS-derived biologic scaffolds may help to overcome barriers to mammalian CNS repair. A method was developed to create CNS ECM scaffolds from porcine optic nerve, spinal cord, and brain, with decellularization verified against established criteria. CNS ECM scaffolds retained neurosupportive proteins and growth factors and, when tested with the PC12 cell line in vitro, were cytocompatible and stimulated proliferation, migration, and differentiation. Urinary bladder ECM (a non-CNS ECM scaffold) was also cytocompatible and stimulated PC12 proliferation but inhibited migration rather than acting as a chemoattractant over the same concentration range while inducing greater rates of PC12 differentiation compared to CNS ECM. These results suggest that CNS ECM may provide tissue-specific advantages in CNS regenerative medicine applications and that ECM scaffolds in general may aid functional recovery after CNS injury.