Aquaporin1 and 3 modification as a result of chondrogenic differentiation of human mesenchymal stem cell

Chondrocytes are cells of articular cartilage particularly sensitive to water transport and ionic and osmotic changes from extracellular environment and responsible for the production of the synovial fluid. Aquaporins (AQPs) are a family of water and small solute transport channel proteins identified in several tissues, involved in physiological pathways and in manifold human diseases. In a recent period, AQP1 and 3 seem to have a role in metabolic water regulation in articular cartilage of load bearing joints. The aim of this study was to examine the levels of AQP1 and 3 during the chondrogenic differentiation of human mesenchymal stem cells (MSCs) derived from adipose tissue (AT). For the determination of chondrogenic markers and AQPs levels, glycosaminoglycans (GAGs) quantification, immunocytochemistry, RT-PCR, and Western blot were used after 0, 7, 14, 21, and 28 days from the start of differentiation. At 21 days, chondrocytes derived from AT-MSCs were able to produce augmented content of GAGs and significant quantity of SOX-9, lubricin, aggrecan, and collagen type II, suggesting hyaline cartilage formation, in combination with an increase of AQP3 and AQP1. However, while AQP1 level decreased after 21 days; AQP3 reached higher values at 28 days. The expression of AQP1 and 3 is a manifestation of physiological adaptation of functionally mature chondrocytes able to respond to the change of their internal environment influenced by extracellular matrix. The alteration or loss of expression of AQP1 and 3 could contribute to destruction of chondrocytes and to development of cartilage damage.