Background: The nurse cell (NC) constitutes in mammalian skeletal muscles a confined intracellular niche to support the metabolic needs of muscle larvae of Trichinella spp. encapsulating species. The main biological functions of NC were identified as hypermitogenic growth arrest and pro-inflammatory phenotype, both inferred to depend on AP-1 (activator protein 1) transcription factor. Since those functions, as well as AP-1 activity, are known to be regulated among other pathways, also by Wnt (Wingless-Type of Mouse Mammary Tumor Virus Integration Site) signaling, transcription profiling of molecules participating in Wnt signaling cascades in NC, was performed.
Methods: Wnt signaling-involved gene expression level was measured by quantitative RT-PCR approach with the use of Qiagen RT(2) Profiler PCR Arrays and complemented by that obtained by searching microarray data sets characterizing NC transcriptome.
Results: The genes involved in inhibition of canonical Wnt/β-catenin signaling cascade as well as leading to β-catenin degradation were found expressed in NC at high level, indicating inhibition of this cascade activity. High expression in NC of genes transmitting the signal of Wnt non-canonical signaling cascades leading to activation of AP-1 transcription factor, points to predominant role of non-canonical Wnt signaling in a long term maintenance of NC biological functions.
Conclusions: Canonical Wnt/β-catenin signaling cascade is postulated to play a role at the early stages of NC formation when muscle regeneration process is triggered. Following mis-differentiation of infected myofiber and setting of NC functional specificity, are inferred to be controlled among other pathways, by Wnt non-canonical signaling cascades.
Keywords: AP-1 transcription factor; Growth arrest; Inflammatory phenotype; Nurse cell; Trichinella spp.; Wnt signaling.