Project Summary: One of dura mater’s most important functionalities is to keep Cerebral Spinal Fluid (CSF) inside of the cranial cavity. To avoid life-threatening complications there exists a need for effective and reliable dural graft replacements post-surgery. A broad selection of dura grafts exists; however, no consensus has been reached on which graft is best suited to avoid dura mater ruptures and adverse immunological responses. Naturally derived and synthetic grafts are most used as dura replacements in the clinic. Native ECM constructs, when properly treated and handled, have the potential to preserve the overall architecture of the tissue matrix. Decellularized constructs have been shown to provide structural support, adhesion sites for cell attachment, and growth factors for cell proliferation. However, the commercially available naturally derived matrices undergo extensive processing, including lyophilization, which may be cause for clearing of relevant ECM proteins needed for sustained tissue health. The research question we propose to answer in this study is Do acellular xenogeneic dural grafts elicit a less deleterious immune response than naturally derived commercial grafts and maintain structural integrity over the long term for in vivo studies? We will examine the rigor of graft sealing strength, risk of infection and/or inflammation, and wound healing/tissue incorporation in vitro and in vivo within a rat model. Our central hypothesis is that native xenogeneic ECM grafts with multiple ECM proteins will perform better than the naturally derived (commercial) ECM dural grafts due to their improved mechanical and immunological responses assayed in vitro and in vivo. This application focuses on two, multi- objective specific aims. In Aim 1 we will perform in vitro studies focused on the mechanical response, structural integrity, immunological response, and scar formation associated with four grafts. We will examine two naturally derived, commercial dural grafts, Biodesign®, and Lyoplant®, and two tissue-based grafts directly from the source—porcine dura, and cadaveric human dura. In Aim 2 we will investigate, in vivo, the border integrity of all grafts by quantifying leakage of CSF. Additionally, we will assess scar formation and immune infiltration in our xenogeneic vs. naturally derived commercially available grafts. The knowledge gained from this work will provide empirical knowledge on the role of tissue-derived xenogeneic grafts for dural replacement. Increased surgeon confidence will enable appropriate graft selection for patients, reduced operative morbidity and mortality following cranial procedures.