FIG. 5.

Wnt inhibitor expression in the spinal cord of adult mice after spinal cord injury (SCI). All of the inhibitors, with the exception of sFRP4 and -5, were detected in the uninjured spinal cord. After SCI, expression of the Dkks was differentially modulated. Dkk1 was induced early, with a maximal peak of expression at 24 hpi, and had a significant decrease in expression from 3 dpi onward. Dkk2 exhibited an early down-regulation during 6–24 hpi, followed by a steady increase in expression from 3 dpi onward. Dkk3 was consistently down-regulated at all time points analyzed, and Dkk4 showed a biphasic up-regulation with peaks at 24 hpi and 14 dpi. Kremen1 was up-regulated during all time points analyzed. sFRP1, -2, and -3 exhibited strong down-regulation during all experimental time points, and Wif1 expression was significantly up-regulated from 3 dpi until the end of the study. Expression levels of inhibitors were measured using quantitative polymerase chain reaction with specific primers, and the results were normalized to β-actin expression. 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). Dkk, dickkopf; mRNA, messenger RNA; d, days; sFRP, secreted Frizzled-related protein; Wif1, Wnt inhibitory factor 1.