Stimulation of HT29-D4 cell growth by excretory/secretory products of the parasite nematode Trichostrongylus colubriformis.

The presence of the nematode parasite Trichostrongylus colubriformis in the small intestine is associated with an increase in epithelial renewal. To assess the possible role of excretory/secretory products from the worm on cell proliferation, adult Trichostrongylus colubriformis were incubated in vitro in Dulbecco's Modified Eagle's Medium for 24 h and the conditioned medium was added to the culture medium of the transformed epithelial cell line HT29-D4. A stimulation of the HT29-D4 cell growth was ascertained at concentrations of 0.25-1.0 micrograms protein/ml using counts of cell numbers, the MTT method and incorporation of tritiated thymidine. An increased incorporation of tritiated thymidine was also observed with the excretory/secretory products from T. colubriformis fourth stage larvae at 1.0 microgram/ml. Dialysis of the medium conditioned by the worms indicated that the molecular weight of the factor is greater than 8000 Daltons in size. Heat treatment, acid hydrolysis and precipitation by trichloracetic acid of the conditioned medium resulted in the disappearance of the proliferative effect while treatment with trypsin partially depleted the stimulative activity. These results suggest that T. colubriformis produce some protein factor which could increase the epithelial regeneration in the host small intestine.