Figure 2.

LPA is a specific, potent survival factor for Schwann cells. (a) Control and LPA (1 μM)-treated SC cultures 48 h after serum withdrawal (DAPI and ISEL+ panels show the same fields). Total cell number is always greater in LPA-treated cultures, whereas the number of cells with apoptotic morphology or ISEL+ labeling is decreased. In contrast, LPA treatment does not affect BrdUrd incorporation. (Bars = 30 μM.) (b) LPA significantly decreases apoptosis as detected by ISEL+ at doses as low as 10 nM. Number of ISEL+-labeled cells is expressed as percentage of control. ∗, P < 0.05; ∗∗, P < 0.0001 (vs. control). (Inset) Northern blot analysis shows that lp_A1/vzg-1 expression is maintained after serum withdrawal. (c) BrdUrd incorporation is not increased by LPA treatment, as it is after addition of 10% FCS. ∗, P < 0.0001 (vs. control). (d) The survival-promoting effect of LPA also is evidenced by increased maintenance of cell number after 48-h serum withdrawal. ∗, P < 0.0001 (vs. control). (e) The LP S1P does not promote SC survival (S1P vs. control, P > 0.3). ∗, P < 0.0001 (vs. control). (f) LPA (1 μM) is as effective in promoting SC survival as a maximal dose (100 ng/ml, determined in pilot experiments) of NRG-β (ref. 18; see also d), a proven SC survival factor (18, 28). LPA and NRG-β do not synergize at these maximal doses. ∗, P < 0.01 (vs. control). In all experiments control is serum-free DMEM alone. (Bars in b–f represent means ± SEM of 3–5 experiments performed in duplicate.) P values are from ANOVA with Fisher’s protected least significant difference post-hoc analysis.