Sonic hedgehog secreted by neurons regulates angiopoietin expression in neighboring fibroblasts

Lately, the importance of the communication between different cell types and the understanding of the cell communication pathway has been emphasized, as it may provide a novel therapeutic strategy for the regeneration of damaged tissue. In the present study, we suggest that sonic hedgehog (Shh) is a mediator of cell communication between neurons and fibroblasts. Recombinant Shh (rShh) affected the expression of the angiogenic factors, angiopoietin (Ang)-1 and Ang-2, in fibroblasts, but not in neurons or neural progenitor cells (NPCs). The expression of the Shh downstream transcription factor, Gli1, was markedly increased in neurons and NPCs, indicating that neurons and NPCs responded to rShh. However, rShh did not affect Ang-1 and Ang-2 expression in neurons and NPCs. It should be noted that Shh was strongly expressed in neurons, but that Shh expression was undetectable in fibroblasts. We performed a co-culture assay using neurons and fibroblasts to investigate whether the expression of Ang-1 and Ang-2 is regulated by cell communication, without rShh treatment. Ang-1 expression in fibroblasts was markedly upregulated by co-culture with neurons, whereas Ang-2 expression was decreased by co-culture with neurons. Moreover, when an Shh-neutralizing antibody was added, this effect was diminished. Collectively, our data suggest that Shh-expressing neurons regulate angiopoietin expression in neighboring fibroblasts in a paracrine manner.