FIG. 2.

Expression of Fz receptors, LRP5/6 coreceptors, and the noncanonical Ryk receptor in the spinal cord of adult mice after spinal cord injury (SCI). All genes were constitutively expressed in the uninjured adult spinal cord. After SCI, the majority of Fz receptors showed a dramatic reduction in expression during the early time points we analyzed (6–24 hpi), followed by a steady increase in expression beginning at 3 or 7 dpi and lasting until 14 dpi, when maximal expression was observed (Fz1, -2, -3, -6, -7, and -10, LRP5, and Ryk). Only Fz4 showed significant up-regulation during 6–24 hpi, after which mRNA levels decreased to below control levels during 7–14 dpi. Fz5 showed no significant changes in its expression profile, and Fz8, 9, and LRP6 exhibited dramatic reductions at nearly all of the time points analyzed. Expression levels of all genes were measured using quantitative polymerase chain reaction with specific primers, and the results were normalized to the β-actin expression. The values for each experimental group and day are expressed as the mean±standard error of the mean (n=4). Each animal/sample was assayed in triplicate in two separate occasions, yielding two independent technical triplicates and six measurements per sample. *p<0.05, compared to C (control). Fz, Frizzled; mRNA, messenger RNA; d, days; LRP, lipoprotein receptor-related protein; Ryk, receptor related to tyrosine kinase.