were done on RGCs and oligodendrocytes using heat inactivated A1 ACM (20-minute treatment at 60 °C) or protease treatment of A1 ACM (0.01 U/ml plasmin from human plasma, Sigma – P1867), 2 h at room temperature. Protease treatment was halted with phenylmethylsulfonyl fluoride (Sigma, 78830) and aprotinin (Sigma, A4529) – final concentrations: 2 mM and 0.55 TIU/ml, respectively. Equivalent amounts of astrocyte base media proteins (BSA, transferrin, HBEGF etc.) were added back to protease-treated A1 ACM before treating cells). Viability was again assessed at 24 h as before. At least 6 independent experiments were conducted for each condition. For each experiment, 4 non-overlapping 20× fields per well were quantified in six wells.
