Authors:
Yang Shuxia, Ma Shengqing, Qin Jian. First Hospital of Beijing University, Beijing, China.
To study the effects of thyroid hormone on hair cycle and hair growth. C57BL6 mice of 6-8 weeks old with hair of telogen were selected, and were fed with different dosage of L-thyroxine sodium (T4).
Anagen was induced by depilation as control. We also cultured the follicles and dermal papilla cells of human scalp hair. We observed the growth and the synthesis of protein and DNA of triiodothyranine (T3)-treated follicles by inverted microscope, 3H-leucine incorporation and 3H-thymidine incorporation. Cultured dermal papilla cells were treated with various concentration of T3. The DNA and insulin-like growth factor I (IGF-I) synthesis were measured by 3H-incorporation and ELISA respectively.
The results showed that anagen of C57BL6 mice can be induced by T4. The duration of anagen induced by T4 was the same as that of control. The T3-treated follicles, compared with control, transformed into catagen prematurely. T3 also inhibited the protein and DNA synthesis of the follicles. The DNA and IGF-I synthesis of the cultured dermal apilla cells was stimulated by T3 100 nM. This study suggested that, T4 can induce telogen hair of C57BL6 mice transforming into anagen, and the reason might be that T3 can stimulate dermal papilla cells growth, and increase the IGF-I synthesis.
However, T3 can shorten the anagen duration of cultured hair follicles, and inhibit protein and DNA synthesis at the same time.
