Comparison of the effects of oxidative and inflammatory stresses on rat chondrocyte senescence.

Osteoarthritis (OA) is an age-related degenerative joint disease that causes progressive cartilage loss. Chondrocyte senescence is a fundamental mechanism that contributes to the imbalance of matrix homeostasis in OA by inducing senescence-associated secretory phenotype (SASP). Although OA chondrocytes are mainly exposed to oxidative and inflammatory stresses, the role of these individual stresses in chondrocyte senescence remains unclear. In this study, we compared the effects of these stresses on the senescence of rat chondrocytes. Rat chondrocytes were treated with H2O2 and a combination of IL-1ß and TNF-α (IL/TNF) to compare their in vitro effect on senescent phenotypes. For in vivo evaluation, H2O2 and IL/TNF were injected into rat knee joints for 4 weeks. The in vitro results showed that H2O2 treatment increased reactive oxygen species, γ-H2AX, and p21 levels, stopped cell proliferation, and decreased glycosaminoglycan (GAG)-producing ability. In contrast, IL/TNF increased the expression of p16 and SASP factors, resulting in increased GAG degradation. Intraarticular injections of H2O2 did not cause any changes in senescent markers; however, IL/TNF injections reduced safranin O staining and increased the proportion of p16- and SASP factor-positive chondrocytes. Our results indicate that oxidative and inflammatory stresses have significantly different effects on the senescence of rat chondrocytes.

Optimal Pore Size of Honeycomb Polylactic Acid Films for In Vitro Cartilage Formation by Synovial Mesenchymal Stem Cells.

BACKGROUND: Tissue engineering of cartilage requires the selection of an appropriate artificial scaffold. Polylactic acid (PLA) honeycomb films are expected to be highly biodegradable and cell adhesive due to their high porosity. The purpose of this study was to determine the optimal pore size of honeycomb PLA films for in vitro cartilage formation using synovial mesenchymal stem cells (MSCs). METHODS: Suspensions of human synovial MSCs were plated on PLA films with different pore sizes (no pores, or with 5 µm or 20 µm pores) and then observed by scanning electron microscopy. The numbers of cells remaining in the film and passing through the film were quantified. One day after plating, the medium was switched to chondrogenic induction medium, and the films were time-lapse imaged and observed histologically. RESULTS: The 5 µm pore film showed MSCs with pseudopodia that extended between several pores, while the 20 µm pore film showed MSC bodies submerged into the pores. The number of adhered MSCs was significantly lower for the film without pores, while the number of MSCs that passed through the film was significantly higher for the 20 µm pore film. MSCs that were induced to form cartilage peeled off as a sheet from the poreless film after one day. MSCs formed thicker cartilage at two weeks when growing on the 5 µm pore films than on the 20 µm pore films. CONCLUSIONS: Honeycomb PLA films with 5 µm pores were suitable for in vitro cartilage formation by synovial MSCs.