Background: Basic helix loop helix (bHLH) proteins play a critical role in
the differentiation of not only striated muscle cells but also adipocytes,
neuron cells and smooth muscle cells, Previous studies have established in
vitro mouse mesangial cells (MCs) to maintain the differentiated smooth mus
cle phenotype. Materials and methods: The purpose of the present study was
to clone bHLH proteins from these MCs using the primers designed from a hom
ologous sequence specific to bHLH, and to analyze the presence of bHLH prot
eins in normal kidney in vivo. From the cloning of MCs in vitro, we identif
ied myf5 and herculin mRNA but not myoD. The expression of bHLH proteins in
vivo was examined by immunohistochemistry with each specific antibody. Res
ults: The MCs in newborn mice possessed Id but did not express either prote
in herculin or myoD. On the other hand, mature MCs expressed both myf5 and
herculin. The Id protein disappeared in mature glomeruli. Conclusion: These
results suggest that bHLH proteins are an important factor for mature MCs
in vivo.