Ph.D Thesis


Ph.D StudentRedenski Idan
SubjectEnhancing Bone Regeneration Capabilities using a Tissue
Engineered Vascular Flap
DepartmentDepartment of Biomedical Engineering
Supervisor PROF. Shulamit Levenberg


Abstract

Functional regeneration of complex large-scaled defects requires both soft and hard tissue grafts. Moreover, bone constructs within these grafts require an extensive vascular supply for survival and metabolism during the engraftment. Soft-tissue pedicles are often used to vascularize bony constructs. However, extensive autologous tissue-harvest required for the fabrication of these grafts remains a major procedural drawback. In the present work, we investigated the potential of human dental pulp stem cells (DPSCs) to serve as a supporting cell population for fabricating highly vascularized tissues. More rapid, stable, and mature vascular networks were formed in human adipose microvascular endothelial cell (HAMEC) cultures supported by DPSCs, as compared to HAMECs monocultures. Transplantation of prevascularized constructs bearing DPSCs into the femoral vessel bundle in rats resulted in highly vascularized neo-tissues, featuring high host vessel invasion and perfusion. Conversely, constructs with HAMECs only exhibited poor graft integration and low vascularization. High-resolution micro-computed tomography (microCT) imaging and novel analytical methods enabled in-depth volumetric and spatial analyses of 3-dimensional (3D) vasculatures within the engineered tissues, indicating significantly higher vessel volume and perfusion by the DPSCs-supported prevascularized constructs.

Next, a composite tissue was fabricated using the same soft tissue engineering approach, while a decellularized bone was combined in vivo to form de novo composite tissue with its own axial vascular supply. Pre-vascularization of the soft tissue matrix using DPSCs and HAMECs enhanced vascular development within decellularized bones. In addition, osteogenic induction of bone constructs engineered using adipose derived mesenchymal stromal cells, positively affected micro-capillary organization within the mineralized component of the neo-tissue. Eventually, these neo-tissues, used as axial reconstructive flaps, supported long-term bone defect repair, as well as muscle defect bridging. The composite flaps described here may help eliminate invasive autologous tissue-harvest for patients in need of viable grafts for transplantation.