title: Oxygen Tension-Controlled Matrices with Osteogenic and Vasculogenic Cells for Vascularized Bone Regeneration In Vivo.
abstract: Despite recent progress, segmental bone defect repair is still a significant challenge in orthopedic surgery. While bone tissue engineering approaches using biodegradable matrices along with bone/blood vessel forming cells offered improved possibilities, current regenerative strategies lack the ability to achieve vascularized bone regeneration in critical-sized/segmental bone defects. In this study, we introduced and evaluated a two-pronged approach for vascularized bone regeneration in vivo. The goal was to demonstrate vascularized bone formation using oxygen tension-controlled (OTC) matrices seeded with bone and blood vessel forming cells. OTC matrices were coimplanted with rabbit mesenchymal stem cells (MSCs) and peripheral blood-derived endothelial progenitor cells (PB-EPCs) to demonstrate the osteogenic and vasculogenic differentiation of these cells, postseeding on a matrix, especially deep inside the matrix pore structure. Matrices coimplanted with varied rabbit MSC and PB-EPC ratios (1:4, 1:1, and 4:1) were assessed in a nude mouse subcutaneous implantation model to determine a coimplantation ratio with superior osteogenic as well as vasculogenic properties. The implants were analyzed, at week 8, for endothelial (CD31 and Von Willebrand factor [vWF]) and osteogenic marker (RunX2 and Col I) staining qualitatively and collagen deposition and number of vessel formation quantitatively. Results from these experiments established MSC-to-PB-EPC ratio 1:1 as the best coimplantation ratio. OTC matrix with 1:1 coimplantation ratio was assessed for segmental bone defect repair in a rabbit critical-sized bone defect model. The group under investigation was OTC matrix, and the matrix was seeded with MSCs, EPCs, or MSCs:EPCs in a 1:1 ratio. Explants at week 12 were evaluated for bone defect repair via micro-CT and histology. Results from rabbit in vivo experiments show enhanced mineralization and vascularization for the 1:1 coimplantation group. Overall, the study establishes a two-pronged approach involving OTC matrix and effective progenitors for large-area and vascularized bone regeneration.
authors.affiliation: 1 Oral and Maxillofacial Surgery, Massachusetts General Hospital , Boston, Massachusetts.|2 Institute for Regenerative Engineering, University of Connecticut Health Center , Farmington, Connecticut.
authors.forename: Ami R
authors.initials: AR
authors.lastname: Amini
authors.affiliation: 2 Institute for Regenerative Engineering, University of Connecticut Health Center , Farmington, Connecticut.|3 Department of Orthopedic Surgery, University of Connecticut Health Center , Farmington, Connecticut.
authors.forename: Thomas O
authors.initials: TO
authors.lastname: Xu
authors.affiliation: 4 Center for Comparative Medicine, University of Connecticut Health Center , Farmington, Connecticut.
authors.forename: Ramaswamy M
authors.initials: RM
authors.lastname: Chidambaram
authors.affiliation: 2 Institute for Regenerative Engineering, University of Connecticut Health Center , Farmington, Connecticut.|3 Department of Orthopedic Surgery, University of Connecticut Health Center , Farmington, Connecticut.|5 Department of Materials Science & Engineering, University of Connecticut , Storrs, Connecticut.|6 Department of Biomedical Engineering, University of Connecticut , Storrs, Connecticut.
authors.forename: Syam P
authors.initials: SP
authors.lastname: Nukavarapu
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001861:Bone Regeneration / Q000187:drug effects*; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000166:cytology* / Q000187:drug effects; D005455:Fluorescent Antibody Technique; D020007:Implants, Experimental; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects; D016513:Mice, SCID; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D010012:Osteogenesis / Q000187:drug effects*; D010100:Oxygen / Q000494:pharmacology*; D011817:Rabbits; D054457:Tissue Scaffolds / Q000737:chemistry*; D014457:Ulna / Q000000981:diagnostic imaging / Q000187:drug effects / Q000473:pathology; D055114:X-Ray Microtomography
chemical_list: D015415:Biomarkers; D010100:Oxygen