Evaluation of MSC-Secretome Effects in an Ex Vivo Compartmentalized Osteochondral Interface Model

Osteoarthritis (OA) represents a significant challenge in both orthopedic research and clinical practice, necessitating the development of effective therapeutic strategies. Here, we describe an ex vivo model based on osteochondral (OCh) explants housed in a three-dimensional printed device that enables the separation of bone and cartilage compartments. Our model demonstrates effective partitioning, as confirmed by significant differences in measurements of tissue-specific markers. The markers included matrix metalloproteinase (MMP) activity and sulfated glycosaminoglycan (sGAG) release for cartilage and alkaline phosphatase (ALP) activity, tartrate-resistant acid phosphatase (TRAP) activity, and osteocalcin (OC) levels for bone. The cartilage compartment of OCh explants was exposed to inflammatory stimuli, to mimic the OA-related microenvironment, using 10 ng/mL TNFα and 1 ng/mL IL-1β. Cytokine administration was coupled with secretome (or conditioned medium, CM) treatment obtained from 5 × 10⁵ naïve or cytokine-primed adipose-derived mesenchymal cells (CM and pCM). After 3 days, inflammatory cytokines induced a significant upregulation of MMP activity, effectively countered by both CM and pCM, alongside a modest increase in sGAG release. No major changes were detected in the bone counterpart. This study holds dual significance: firstly, the development and preliminary assessment of a human-based ex vivo model in accordance with 3Rs (Replacement, Reduction, Refinement) principles in preclinical research; secondarily, the evidence of an anti-catabolic potential of the adipose-derived mesenchymal cell secretome contributes, within a broader research context, to hypothesizing its potentiality in counteracting OA-associated hallmarks, with possible applications at early onset to mitigate the degenerative processes of this pathology. Trial Registration: ClinicalTrials.gov identifier: NCT04223622.