Blockade of purinergic receptors or pannexin hemichannels does not reverse the effects of depolarization. Total calcium content in hMSCs was quantified after 21 days of OS differentiation under depolarized (HK, 40 mM high K+) or nondepolarized (OS) conditions, in the presence of 30 or 10 μM PPADS, 1 or 0.1 μM TNP-ATP, or 10 μM CBX. Data points represent mean calcium content (μg) ± standard deviation, n = 3. CBX, carbenoxolone; PPADS, pyridoxalphosphate-6-azophenyl-2′,4′-disulfonic acid tetrasodium salt; TNP-ATP, 2′,3′-O-(2,4,6-Trinitrophenyl)adenosine-5′-triphosphate tetra(triethylammonium) salt.