3D-Printed Graphene Material Scaffolds in a Rat Femoral Neurotization Model for Muscle Tissue Engineering
Sumanas W. Jordan, MD, PhD1, Adam E. Jakus, PhD2, Phillip Lewis, BS2, Xin Li, MD, PhD2, Ramille N. Shah, PhD2.
1The Ohio State University, Columbus, OH, USA, 2Northwestern University, Chicago, IL, USA.
PURPOSE: Though vascularization has been a long-recognized and significant challenge in tissue engineering, the task of neurotization has been understated. Functional tissues require integration with the voluntary or autonomic nervous system for applications including, but not limited to, facial reanimation, intrinsic hand muscle reconstruction, cardiac rehabilitation, and urologic tone. Electrically conductive biomaterials, such as graphene, are a relatively unexplored, promising class of materials which have been shown to support neural, glial, and muscle cell types even in the absence of stimulation. This is the first study to evaluate graphene in a neurotized in vivo environment. METHODS: Graphene-based scaffolds were 3D-printed from a liquid ink comprising 60%vol particle and 40%vol polylactide-co-glycolide (PLG). Three material scaffolds were fabricated: (i) 3D-printed graphene (3DG, 60%vol graphene/40% PLG), (ii) 3D-printed graphene-decellularized muscle ECM blend (3DG-mECM, 30%vol graphene/30% mECM particles/40% PLG), and (iii) 3DG infused with decellularized skeletal muscle hydrogel (3DG-mgel). Scaffolds measured 6-mm diameter by 2.5-mm thick (8 layers, 600-micron strut size, 90 degree offset). The constructs were implanted in a rat medial thigh muscle defect with and without femoral nerve coaptation for 6 weeks. Explants were analyzed by histology and scanning electron microscopy. RESULTS: Vascularization was observed between the struts of all constructs. Myogenesis (Pax7+) was observed replacing the struts of 3DG-mECM constructs. Fewer Pax7+ cells were observed in 3DG and 3DG-mgel groups. Increased graphene dispersion between struts was observed in the neurotized group compared to internal controls. An encapsulation foreign body response was not observed. Macrophage (CD68+) amount and distribution did not differ significantly between groups. CONCLUSION: Neurotization altered the degradation pattern of the constructs. 3D-printed scaffolds containing decellularized skeletal muscle induced myogenesis without exogenous growth factors or cells. Material ink composition may be tuned to impart inherent myogenic bioactivity.
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