Investigate the effects of insulin-like growth factor-1 (IGF-1) expression in vivo on vibrissae growth in transgenic mouse and the effects of exogenous IGF-1 in vivo on hair follicle growth in Swiss Random White mice

Abstract

The objective of this project was to investigate the effects of insulin-like growth factor-I (lGF-I) on the rate of vibrissa and follicle growth in mice. The project was divided into two parts. Part one of the project was divided into two experiments. Experiment one is to study the effect of IGF-I during early anagen phase of the vibrissae growth cycle, on day 6, 10 and 14. Experiment two is to study the effect of IGF-I during late anagen phase of the vibrissae growth cycle. Part two of the project , refered to experiment three in this dissertation, investigates the effect of IGF-I on hair follicle size. The first part of the project was to study the effects of over-expression of IGF-I in murine skin on the rate of vibrissae growth in transgenic mice. These transgenic mice contain an IGF-I construct driven by an ultra-high sulphur keratin (UHSK) promoter specific for the expression of hair specific protein in the hair follicle. Radioautographic technique (23) was used to measure and investigate the effect of IGF-I on the rate of hair growth in transgenic and non-transgenic mice from mouse line 1417. The rate of hair growth in mice was measured by [35S]Cystine administration on two separate periods. The first period spans day 6, 10 and 14 of age. This period constitutes early anagen phase of the neonatal- hair cycle. The second period spans day 11,16 and 21, and corresponds to late anagen to catagen. The vibrissae were plucked after the last IGF-I injection, treated with photographic emulsion and developed to reveal three black spots that correspond to the [35S]Cystine injections administered. The distance between the spots gives a measure of the rate of vibrissa growth and results have shown that there is a significant difference in the rate of vibrissa growth between the transgenic and non-transgenic mice. IGF-I also has a significant effect in stimulating increases in body weight (p<O.05) of transgenic mice compared with non-transgenic mice.