Auxin induces cell proliferation in an experimental model of mammalian renal tubular epithelial cells

Indole-3-acetic acid is the main auxin produced by plants and plays a key role in the plant growth and development. This hormone is also present in humans where it is considered as a uremic toxin deriving from tryptophan metabolism. However, beyond this peculiar aspect, the involvement of auxin in human pathophysiology has not been further investigated. Since it is a growth hormone, we evaluated its proliferative properties in an in vitro model of mammalian renal tubular epithelial cells. We employed an experimental model of renal tubular epithelial cells belonging to the LLC-PK1 cell line that is derived from the kidney of healthy male pig. Growth effects of auxin against LLC-PK1 cell lines were determined by a rapid colorimetric assay. Increasing concentrations of auxin (to give a final concentration from 1 to 1000 ng/mL) were added and microplates were incubated for 72 h. Each auxin concentration was assayed in four wells and repeated four times. Cell proliferation significantly increased, compared to control cells, 72 h after addition of auxin to cultured LLC-PK1 cells. Statistically significant values were observed when 100 ng/mL (p < 0.01) and 1000 ng/mL (p < 0.05) were used. In conclusion, auxin influences cell growth not only in plants, where its role is well documented, but also in mammalian cell lines. This observation opens new scenarios in the field of tissue regeneration and may stimulate a novel line of research aiming at investigating whether this hormone really influences human physiology and pathophysiology and in particular, kidney regeneration.