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.

Platelet‐rich fibrin‐based matrices to improve angiogenesis in an in vitro co‐culture model for bone tissue engineering

“…An ongoing challenge for tissue-engineering applications is the sufficient vascularization of an engineered construct that is essential for the survival of the implant and an adequate wound repair. Therefore, the generation of a tissue-like vascularized scaffold for implantation using cell-based prevascularization strategies in different experimental settings has been documented as advantageous (Amini, Xu, Chidambaram, & Nukavarapu, 2016;Grellier et al, 2009;Rouwkema et al, 2006;Tabata et al, 1999). In the context of bone tissue engineering, co-culture systems consisting of endothelial cells and osteoblasts or their precursors can be used from different sources in scaffold-free approaches as well as in combination with a material or co-implanted in Matrigel®-plugs (Fuchs, Jiang, et al, 2009;Rouwkema et al, 2006;Stahl et al, 2004).…”

Micro‐Nanostructures of Cellulose‐Collagen for Critical Sized Bone Defect Healing

“…A remaining challenge of BTE implants is limited diffusion, which results in the accumulation of material degradation products at the implant core. Consequently, acidic byproducts, such as those associated with PLGA, can cause minimum cellularity at the scaffold core resulting in bone formation that is limited to the periphery of the implant . Our results have demonstrated that the natural polymer based CA and CAc 3D‐porous microstructures and micro‐nanostructures showed greater tissue infiltration in contrast to PLGA structures.…”

The synergistic effect of bone forming peptide‐1 and endothelial progenitor cells to promote vascularization of tissue engineered bone

“…The uptake of Dil‐Ac‐LDL and binding of FITC‐UEA‐1 were examined using fluorescence microscope (EVOS FL Auto, Life Technologies). Immunofluorescence staining of endothelial markers for VEGF receptor‐2 (VEGFR2; ab39256, Abcam) and von Willebrand Factor (vWF; ab6994, Abcam) were also used to characterize EPCs …”

“…Immunofluorescence staining of endothelial markers for VEGF receptor-2 (VEGFR2; ab39256, Abcam) and von Willebrand Factor (vWF; ab6994, Abcam) were also used to characterize EPCs. 21…”