To compare the therapeutic potential of tissue-engineered constructs (TECs) combining mesenchymal stem cells (MSCs) and coral granules from either Bone marrow-derived, autologous MSCs were seeded on Objectives
Materials and Methods
Bone tissue engineering constructs (BTEC) combining natural resorbable osteoconductive scaffolds and mesenchymal stem cells (MSCs) have given promising results to repair critical size bone defect. Yet, results remain inconsistent. Adjonction of an osteoinductive factor to these BTEC, such as rh-BMP-2, to improve bone healing, seems to be a relevant strategy. However, currently supraphysiological dose of this protein are used and can lead to adverse effects such as inflammation, ectopic bone and/or bone cyst formation. Interestingly, in a preliminary study conducted in ectopic site in a murine model, a synergistic effect on bone formation was observed only when a low dose of rh-BMP-2 was associated with MSCs-seeded coral scaffolds but not with a high dose. The objective of the study was then to evaluate a BTEC combining coral scaffold, MSCs and a low dose of rh-BMP-2 in a large animal model of clinical relevance. Sixteen sheep were used for this study. MSCs were isolated from an aspirate of bone marrow harvested from the iliac crest of each sheep receiving BTEC with MSCs, cultivated and seeded on Rh-BMP-2, used at two different doses (low dose: 68μg/defect and high dose: 680μg/defect), was diluted and absorbed on Metatarsal segmental bone defects (25 mm) were made in the left metatarsal bone of the sheep, stabilized by plate fixation, and filled with Bone volumes (BV) evaluated by μCT and bone surfaces (BS) evaluated by histomorphometry did not differ between groups (BV: 1914±870, 1737±841, 1894±1028 and 1835±1342 mm3; BS: 25,41±14,25, 19,85±8,31, 25,54±16,98 and 26,08±22,52 %; groups 1, 2, 3 and control respectively); however, an higher bone union was observed in group 1 compared to the others (3, 1, 2 and 2 sheep with bone union in groups 1, 2, 3 and control respectively). No histological abnormalities were observed in any group. Coral resorption was almost complete in all specimens. No significant difference in coral volumes and coral surfaces was observed between groups. A trend towards a higher variability in coral resorption was noted in group 1 compared to the others. There seems to be a benefit to associate low dose of rh-BMP-2 with MSCs-seeded coral scaffolds as this strategy allowed an increase of bone unions in our model. Yet, results remain inconsistent. Although, defective coupling between scaffold resorption and bone formation impaired bone healing in some animals, adjunction of rh-BMP-2 (even at low dose) to CSMs loaded construct is a promising strategy for bone tissue engineering.
MSCs could promote bone regeneration in sheep when loaded on natural fully-resorbable scaffolds, but results are highly variable. Improving the ultimate performance of cell-containing constructs cannot be limited to the decreased rate of scaffold resorption. Introduction. Tissue constructs containing mesenchymal stem cells (MSCs) are an appealing strategy for repairing massive segmental bone defects. However, their therapeutic effectiveness does not match that of autologous bone grafts; among the failure reasons the scaffold resorbability has been identified as a critical feature for achieving bone regeneration. In the present study, the osteogenic potential of 2 constructs obtained by expanding in a bioreactor autologous MSCs onto granules of Acropora or Porites coral, natural fully-resorbable scaffolds, was compared. 15 sheep underwent a 25 mm long metatarsal ostectomy stabilised with a 3.5 DCP plate. Bone defects were replaced with (i) MSCs-Acropora constructs (n=7), (ii) MSCs-Porites constructs (n=6), (iii) autograft (n=2). Animals were sacrificed 4 months later and bone healing and coral resorption was documented by radiographic, histologic and microCT studies.Summary
Materials and methods
Despite similar, early and massive death, hMSCs promote bone formation which was higher in orthotopic than ectopic site suggesting a trophic effect of hMSCs. Ectopic implantation is suitable to evaluate cell survival, but assessment of bone formation requires orthotopic implantation Tissue constructs containing mesenchymal stem cells (MSCs) are appealing strategies for repairing large segmental bone defects but they do not allow consistent bone healing and early and massive MSCs death was identified as a cause of failure. However, little is known about cell survival in the clinical micro-environment encountered during bone healing process, whereas ectopic evaluation is well documented.
Summary
Introduction
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. 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.Short Summary
Introduction
an abundant vascular network, presence of cells expressing transcription factor CBFA1, very few inflammatory CD14+ cells (macrophages), an extracellular matrix positive for type I collagen.
evaluate new therapeutic strategies for bone regeneration in conditions close to clinical situations, study the role of the membrane in bone repair. The presence of a pseudosynovial membrane might:
be a barrier against the diffusion of bone morphogenetic proteins outside the lesion and potentially be a reservoir of stem and vascular cells which could be useful for new technologies.
