Abstract
Short Summary
The present study demonstrated the feasibility of culturing a large number of standardised granular MSC-containing constructs in a packed bed/column bioreactor that can produce sheep MSC-containing constructs to repair critical-size bone defects in sheep model.
Introduction
Endogenous tissue regeneration mechanisms do not suffice to repair large segmental long-bone defects. Although autologous bone graft remains the gold standard for bone repair, the pertinent surgical technique is limited. Tissue constructs composed of MSCs seeded onto biocompatible scaffolds have been proposed for repairing bone defects and have been established in clinically-relevant animal models. Producing tissue constructs for healing bone defects of clinically-relevant volume requires a large number of cells to heal an approximately 3 cm segmental bone defect. For this reason, a major challenge is to expand cells from a bone marrow aspirate to a much larger, and sufficient, number of MSCs. In this respect, bioreactor systems which provide a reproducible and well-controlled three-dimensional (3D) environment suitable for either production of multiple or large size tissue constructs are attractive approaches to expand MSCs and obtain MSC-containing constructs of clinical grade. In these bioreactor systems, MSCs loaded onto scaffolds are exposed to fluid flow, a condition that provides both enhanced access to oxygen and nutrients as well as fluid-flow-driven mechanical stimulation to cells. The present study was to evaluate bioreactor containing autologous MSCs loaded on coral scaffolds to repair critical-size bone defects in sheep model.
Materials and Methods
Animals: 12 two-year-old, female Pre-Alpes sheep were used and reared in accordance with the European Committee for Care. Three-dimensional, porous scaffolds (each 3×3×3 mm) of natural coral exoskeleton were used as substrates for cell attachment. The packed bed/column bioreactor set-up used in the present study was composed of a vertical column filled with MSC-containing constructs. Sheep MSCs were isolated from sheep bone marrow. MSCs were seeded on scaffolds and cultured overnight under standard cell-culture condition. MSC-containing constructs were r placed into the perfusion bioreactor and were either exposed to a perfusion medium flow rate of 10 mL/min for 7 continuous days. Osteoperiosteal segmental (25 mm) defects were made in the left metatarsal bone of 12 sheep. The defect was either filled with coral scaffolds alone (Group 1; five sheep); or filled with coral scaffolds loaded with MSCs (Group 2; five sheep); or filled with autologous bone graft (Group 3; 2 sheep).
Results
At 6 month after implantation, radiographs showed resorption of the coral scaffold in all animals but this process was not complete and not the same in all animal. At 6 month radiographs showed more bone formation in group 2 than in group 1. New bone formation volume in each defect was assessed by micro-computed tomography. Volume of bone healing was higher in group 2 than group 1.
Discussion
The potential of MSC-containing constructs in a bioreactor for repairing long segmental critical-sized bone defects in sheep was investigated. In one animal of the group 2 the volume of new bone formation was 2066 mm3 and was similar to the bone volume of group 3 (2300 mm3). Our results may have important implications in bone tissue engineering. We observed that the bone tissue regenerationosteogenic ability of bone constructs processed in bioreactor approached the bone autografts.
