Abstract: Objective To discuss the effect of Usma grass on hair growth in hair removal mouse models and whether the content of parathyroid hormone（PTH） in mice affects hair growth rate,providing experimental basis for the treatment of hair loss with Usma grass. Methods Totally 59 mice were divided into groups based on gender and the dosage of Usma grass liquid,and the experimental area was taken from the symmetrical part of their backs. The blank control group was not treated,while the hair removal group had hair removal every three days. The experimental group was divided into physiological saline group,high,medium,and low dose groups according to gender. Apply the hair removal cream evenly to the skin on the back of the mouse and wipe off after 6 minutes. The experimental group was divided into groups and administered continuously for 24 days. The hair growth status,histological changes of hair follicles,and the diameter of final and velvety hair sections in the depilation area of mice were recorded. Measure the PTH content in mice using an ELISA kit. Results There was a statistically significant difference in hair growth scores between mice on days 11,15,18,and 21（P<0.05）. There were no statistically significant differences in hair regeneration weight between different groups（all P>0.05）. There were no statistically significant differences in PTH content in the blood between mice of different genders（all P>0.05）. Comparing the hair follicle slices of the experimental area on the back of mice, the number of final hair follicles in mice treated with Usma grass reagent was higher than that in the control group. Hair removal cream reduced the number of terminal hairs in the hair follicles of the experimental area and increased the number of velvety hairs. Conclusion Usma grass has a promoting effect on hair growth in hair removal mouse models,and the effect of PTH content on hair growth rate in mice is meaningless. This can provide experimental evidence for the treatment of hair loss with Usma grass.

Key words: Usma grass, Mouse hair loss model, Parathyroid hormone, Stained sections