Intraarticular Administration of Dexamethasone after Mesenchymal Stem Cells Implantation Does Not Improve Significantly the Treatment of Preestablished Full-Thickness Chondral Defect in a Rabbit Model

OBJECTIVE: The aim of this study was to evaluate the contribution to hyaline cartilage regeneration of dexamethasone intraarticular administration after autologous mesenchymal stem cells (MSCs) implantation into a preestablished knee full-thickness chondral defect. DESIGN: Full-thickness chondral defects of 4.5 × 4.5 mm(2) were surgically made in both medial femoral condyles of adult male New Zealand rabbits. Two weeks later, autologous ex vivo expanded bone marrow–derived MSCs were embedded in hyaluronic acid and implanted into the chondral defects. Immediately and every week after the intervention, dexamethasone 0.25 mg/kg was intraarticularly administered (MSC/dexa-treated group). Six weeks after MSC transplantation, the animals were euthanized and condyles were characterized molecularly according to aggrecan, collagen type II, and collagen type I gene expression (quantitative reverse transcriptase-polymerase chain reaction) and histologically (hematoxylin–eosin staining). Data of MSC/dexa-treated condyles were compared with untreated, dexa-treated, MSC-treated, or normal unlesioned condyles. RESULTS: The ratio between collagen type II expression versus collagen type I expression in MSC/dexa-treated condyles was higher than one, even though the group mean value was not statistically different from that of untreated defects. Histological changes were observed between MSC/dexa-treated and untreated defects mainly in surface regularity and in hyaline matrix abundance. However, International Cartilage Repair Society score analysis did not support robust differences between those groups. CONCLUSION: Intraarticular administration of dexamethasone after autologous MSC implantation into a preestablished full-thickness chondral defect does not contribute significantly to the regeneration of a tissue with molecular and histological characteristics identical to hyaline cartilage.