"INTRODUCTION: Osteoarthritis (OA) is the most common arthropathy and a leading cause of pain and disabilities worldwide. Globally, OA affected more than 300 million people; however, despite its prevalence and importance, even economically, the comprehension of its molecular background is limited. Moreover, as OA is characterized by a complex molecular network, it is unlikely that targeting a single molecule would be sufficient to treat the disease. In this perspective, the idea of cell-based-therapies has gained much attention to possibly revert and stop the disease’s progression. However, even though the effects exerted by stem cells on chondrocytes have been investigated, it’s not clear yet if the stem cell’s niche and their potency affect the quality of the tissue regeneration. For these reasons, the aim of this work was to investigate the effects exercised by different stem cell populations (multi- and pluripotent) on diseased chondrocytes, to identify the key molecules responsible for a successful articular cartilage (AC) regeneration.
METHODOLOGY: The hASCs (human adipose stem cells), SVF (stromal vascular fraction), hAECs (human amniotic epithelial stem cells) and the OA chondrocytes were isolated from tissue biopsies in accordance with the 1975 Declaration of Helsinki and the Ethics Committees of the research institutes involved. The stem cells (SCs) were isolated and kept in their specific growth media (GM) until further processing. After chondrocytes isolation,3D cultures were prepared (50 % chondrocytes + 50 % SCs), cultured at 37°C in humidified atmosphere (5% CO2) and soaked by GM (DMEM high glucose, 10% FBS, pen/strep, amphotericin B, ascorbic acid 0.05 mM). After 7 and 21 days of culture, the pellets were sacrificed to extract the total RNA according to Chomczynski method. Then, the gene expression of healthy and hypertrophic articular cartilage markers was analysed with qRT-PCR, and the results were reported as relative gene expression (fold change -FC).
RESULTS: The qRT-PCR results indicated that the hASCs induced the best regenerative response in OA chondrocytes; indeed, while the AC markers were up-regulated those associated with fibrotic and hypertrophic phenotypes were down-regulated. The treatment with SVF instead, revealed an increase of runx2 and col10a1 expression, suggesting that the heterogeneous population of SVF might not be the more appropriate source of bioactive factors for AC regeneration. When OA chondrocytes were treated with AECs, the expression of transcription factors peaked earlier (7 d); however, the results don’t display any clear trend; indeed, besides the up regulation of AC specific genes, there was an increase in the expression of hypertrophic markers. Nevertheless, these results reflect the plasticity of hAECs which, depending on the microenvironment, can finely modulate the components of their secretome, affecting the overall biological outcome.
CONCLUSIONS: To conclude, the results clearly indicated that the stem cell populations differ in their ability to induce a high-quality AC. However, these encouraging results need further investigation with high-throughput techniques to map accurately the differently expressed molecules, that may reveal important hints for OA fighting."