CASP3 and cyclic hematopoiesis: In order to investigate the involvement of Erk1/2, p38 MAPK, and PI3K/Akt signaling pathways in the catabolic responses of OA-CH, the viability and caspase 3/7 activity of IL-1β-induced OA-CH were determined after treatment with inhibitors of Erk1/2 (U0126), PI3K/Akt (LY294002), and p38MAPK (SB202190) for 24 h (Fig. 7a, b).