Figure 2. Analysis of SIRT1 expression and the degree of senescence in human NP cells subjected to high-magnitude compression. (A) Schematic of the primary units of the substance exchanger-based perfusion bioreactor system: (1) medium reservoir; (2) peristaltic pumps; (3) tissue culture chambers; (4) substance exchanger; (5) pH, PO2 and PCO2 sensor; (6) loading application devices. NP cell-encapsulated Gel-MA hydrogels were dynamically compressed by the loading application devices in the chambers at 0% (a) and 20% (b) compressive deformation for the control and high-compression groups, respectively at a frequency of 1.0 Hz. (B) The degree of senescence of the NP cells subjected to 0% or 20% (high-magnitude) compressive deformation was analyzed using SA-β-Gal staining (200×). (C) The expression level of SIRT1 in the NP cell-encapsulated hydrogels was detected by immunohistochemistry (200×). (D) The SIRT1, PGC1α and senescence-related protein (AMPK, P53, P21 and P16) levels were analyzed by Western blotting. *P<0.05 versus the control group. Black bars=100 μm.