Figure 2: Calcium signaling is impaired in aged human keratinocytes.

(a) Response to high extracellular calcium of FURA2 labelled NHEK (top panel) and AHEK (bottom panel) monolayers. Representative traces of 6–7 separate experiments on cells cultured from 3 neonatal and 3 aged donors. (b) distribution of single cell [Ca²⁺]_i variation after calcium switch reported as ΔR. N=220–410 cells per group from 6 (AHEK)-7 (NHEK) separate experiments on cells cultured from 3 neonatal and 3 aged donors. Asterisk denotes p<0.05. (c-f) Representative traces of cytosolic Ca²⁺ concentrations in keratinocytes at baseline and in response to 1uM thapsigargin followed by 1.2 mM [Ca²⁺]. NHEK (c) and AHEK (d) in 0.07 mM Ca²⁺. NHEK (e) vs. AHEK (f) cultured in 1.2 mM [Ca²⁺] for 24 hours. Data are reported as the ratio R of the fluorescence intensity at 340nm excitation (f_bound) over the fluorescence intensity at 390nm excitation (f_free). N=102–380 cells per group from 3–7 separate experiments on cells cultured from 3 neonatal and 3 aged donors. Results are summarized in Table 1.