Wnts are expressed in the spinal cord of adult mice and are differentially induced after injury

The Wnt family of proteins plays key roles during central nervous system development and has been involved in several neuropathologies during adulthood, including spinal cord injury (SCI). However, Wnts expression knowledge is relatively limited during adult stages. Here, we sought to define the Wnt family expression pattern after SCI in adult mice by using quantitative PCR (qPCR) and immunohistochemistry. Under physiological conditions, the mRNAs of most Wnt ligands, inhibitors, receptors and co-receptors are constitutively expressed in healthy adult mice. Following dorsal hemisection, we found significant time-dependent variations, with a prominent upregulation of the Wnt Inhibitory Factor 1. Accordingly, immunohistochemistry against Fz1 and Fz4, as representatives of late and acute up-regulated receptors, showed a differential expression in the uninjured spinal cord of Fz1 by neurons and oligodendrocytes and Fz4 by astrocytes. After injury, both receptors were maintained in the same type of cells. Finally, by using the BATgal reporter mice, our results revealed active β-catenin signaling in neurons of the dorsal horn and cells of the central canal of uninjured spinal cords, besides a lack of additional SCI induced activation. In conclusion, we demonstrate Wnt expression in the adult spinal cord of mice that is modulated by SCI, which differs from the previously described in rats. Furthermore, Fz receptors are differentially expressed by neurons and glial cells, suggestive for cell-specific patterns and thus diverse physiological roles. Further studies will help to in-depth characterize the role of all Wnt factors and receptors described, and eventually allow for the design of novel therapies.