(A) MSC chondrogenic differentiation in response to multiple exposures to PEMFs or exogenously elevated calcium. MSCs were subjected to either PEMF stimulation alone (white bars) or with transient supplementation of CaCl2 alone (5 mM; hatched bars), once (1x), twice (2x) or thrice (3x) in a week. Dotted lines refers to expression level of non-treated controls. Real-time PCR analysis was performed on day 7 of chondrogenic differentiation. *Denotes significant increase relative to non-PEMF (0 mT) control. # and + denote significant differences relative to respective single (1x) exposure (white and hatched bars, respectively). P = PEMF treatment, Ca = CaCl2 supplementation. (B) MSC chondrogenic differentiation in response to multiple exposures to PEMFs alone (white bars) or in combination with calcium chelator (EGTA) or TRP channel antagonists. EGTA (2 mM; dark grey bars; “E”), Ruthenium Red (10 µM; RR, black bars; “R”) or 2-APB (100 µM; light grey bars; “C”) was added to the MSC differentiation medium during PEMF expoure applied once (1x), twice (2) or thrice (3x) per week. EGTA, RR and 2-APB were included 10 min before exposure and replaced with media harvested from age-matched chondrogenic control cultures 10 min after exposure. *Denotes significant increase compare to non-PEMF (0 mT) control. #Denotes significant decrease compared to single PEMF exposure (1x). +Denotes significant difference compared to respective PEMF control (white bar). P = PEMF treatment, E = EGTA, R = Ruthenium Red (RR), C = 2-APB. Data shown are means ± SD, n = 6 from 2 independent experiments.