Leveraging Microsurgery and Bioprinting for Rapidly Oriented Vascularized Tissue Engineering

PROJECT SUMMARY/ABSTRACT Reconstructive surgery is the main treatment strategy to repair craniomaxillofacial (CMF) injuries. However, surgical options are often antiquated, leading to suboptimal outcomes, both functionally and cosmetically. Tissue engineered ‘replacement grafts’ represent the next era of reconstructive surgery. However, clinical translation is still profoundly limited by the lack of prompt vascularization following implantation. This leads to necrosis and reconstructive failure. Thus, there exists significant clinical need for an effective method that circumvents current limitations of graft vascularization. Our premise, based upon extensive clinical and tissue engineering expertise along with rigorous preliminary data is that new surgical and engineering approaches can be used to not only augment graft vascularization but also purposely orient microvascular ingrowth. We have recently developed a novel microsurgical tactic termed “vascular micropuncture” (MP) that significantly augments the angiogenic potential of the surgical site. With MP, we use an ultrafine needle (e.g., 60 µm) to create perforations in the targeted recipient macrovasculature to enable cell extravasation and angiogenesis, expediting the time to adjacent scaffold vascularization. With these compelling results, we propose to advance our microsurgical method using emerging three-dimensional (3D) printing technologies. Based on our unique approach, our overarching hypothesis is that MP will improve vascularization and survival of 3D printed or bioprinted bone grafts. To test this hypothesis, we will work on two complementary, but independent, aims. In Aim 1, using a rat model we will test the effectiveness of MP in vascularizing calvarial defects directly from the sagittal sinus vein. Following a defined implantation period, vascularization will be quantified via laser doppler, angiography, immunohistochemistry, and protein analysis. Next, a novel 3D air printing technique will be used to generate vascularized channels within 3D scaffolds, which will be used to guide the orientation of microvascular ingrowth. We will also perform a sheep study to demonstrate MP scalability and translatability. In Aim 2, we will assess the potential of sagittal sinus MP to directly induce the vascularization of bioprinted bone grafts. Sagittal sinus MP will be coordinated with implantation of an engineered bone graft fabricated via a novel high-throughput bioprinting method using high-cell density osteogenically committed spheroids. Vascularized bone volume/density will be evaluated using micro-computed tomography and histology. Accomplishment of these independent aims together will allow us to establish a groundbreaking surgical approach for tissue engineered graft vascularization and ultimately improve patient care.