CCS,
The first study demonstrates the IGF-1 is a mediator in hair growth in vivo. The second study demonstrates that finasteride increases this mediator and that it seems to actually be required for any response to Finasteride in vivo.
(1)J Invest Dermatol. 2006 Sep;126(9):2135; author reply 2135-6.
Igf-I signalling controls the hair growth cycle and the differentiation of hair shafts.Weger N, Schlake T.
Max-Planck Institute of Immunobiology, Freiburg, Germany.
Mesenchymal-epithelial signalling between the dermal papilla and the hair matrix regulates cell proliferation and differentiation in mature hair follicles. The molecular basis of these interactions is largely unexplored. According to its expression in the dermal papilla, IGF-I is likely involved in reciprocal signalling. To examine its biological function in pelage follicles further, we generated transgenic mice that express Igf-I in the inner root sheath and the medulla using an involucrin promoter fragment. We demonstrate that Igf-I affects follicular proliferation, tissue remodelling, and the hair growth cycle, as well as folliclular differentiation. Transgenic skin temporarily lacks visible adipose tissue in telogen. The onset of the second, aberrant growth phase is markedly retarded. Transgenic guard hairs are significantly elongated and a small fraction of hair follicles is severely disoriented. The microscopic appearance of most hair shafts is altered and, strikingly, Igf-I transgenic mice lack hairs with a zigzag shape due to the suppression of hair shaft bending. All transgenic effects are partially compensated by ectopic expression of Igfbp3. Finally, Pdgfralpha was identified as the first molecular target that is affected in Igf-I transgenic mice. In summary, our data identify IGF-I signalling as an important mitogenic and morphogenetic regulator in hair follicle biology.
(2)J Am Acad Dermatol. 2003 Aug;49(2):229-33. Links
The expression of insulin-like growth factor 1 in follicular dermal papillae correlates with therapeutic efficacy of finasteride in androgenetic alopecia.Tang L, Bernardo O, Bolduc C, Lui H, Madani S, Shapiro J.
Division of Dermatology, The University of British Columbia, Vancouver Hospital, Canada.
BACKGROUND: It is generally believed that dihydrotestosterone is one of the pivotal mediators of hair loss in androgenetic alopecia (Androgenetic Alopecia). Finasteride, which blocks the conversion of testosterone to dihydrotestosterone, has now become an integral part of the current treatment approaches for male Androgenetic Alopecia. Several lines of evidence support the notion that dermal papilla (DP) cells represent the androgen target within the hair follicle. The specific molecular regulators modulated by androgens within hair follicles in the balding scalp are unknown. OBJECTIVE: The purpose of this study was to identify and quantify changes in expression of specific molecular hair growth regulators in DP of men with Androgenetic Alopecia treated with finasteride and correlate these findings to clinical efficacy. METHODS: Biopsy specimens were collected from 9 male patients from both the balding area and nonbalding occipital area before and after 4 months of finasteride therapy. DP were microdissected and total RNA was extracted from an equal number of DP from each biopsy specimen. The expression of various cytokines, including insulin-like growth factor (IGF)-1, was determined by reverse transcription polymerase chain reaction. The signals were detected by autoradiography. All 9 patients were given finasteride for 1 year and evaluated for efficacy at month 12. Efficacy was graded on a 7-point scale on the basis of comparison with initial baseline photography. RESULTS: IGF-1 was up-regulated by finasteride treatment in 4 of 9 patients. Among the patients with increased IGF-1 expression, 3 of them showed moderate clinical improvement after 12 months of treatment and another patient remained unchanged. In contrast, 3 patients with decreased IGF-1 expression in the balding scalp showed clinical worsening after 12 months. The other 2 patients without noticeable change in IGF-1 expression showed either slight improvement or no change in their hair condition. CONCLUSION: In a small uncontrolled study of 9 patients with Androgenetic Alopecia, an increased expression of IGF-1 messenger RNA levels in the DP was associated with patient response to finasteride.