P2.16 Bulge Region- and Epidermal Basal Layer-Specific Expression of Fibroblast Growth Factor-13 (FHF-2) in Mouse Skin

Mitsuko Kawano^{1, 2}, Akiko Komi-Kuramochi¹, Satoshi Suzuki³, Ryoji Tsuboi⁴ and Toru Imamura^{1, 2, 3}

¹National Institute of Advanced Industrial Science and Technology (AIST), Higashi, Tsukuba, Ibaraki, Japan; ²University of Tsukuba, Tsukuba; ³Advangen, Inc. Tsukuba; ⁴Tokyo Medical University, Shinjuku, Tokyo, Japan

Objectives: A variety of polypeptide growth factors, including several members of the fibroblast growth factor (FGF) family, have been reported to play important roles in the dynamic maintenance of skin and hair.  Here, we aimed at identifying additional member(s) of the FGF family which play important roles in skin.

Methods: Using real time PCR, expression of all 22 FGF family members in C3H/HeN adult mouse skin was quantitated at various stages of hair cycle.  The distribution of the FGF member of interest was evaluated using in situ hybridization and immunohistochemical staining.  Hair follicle morphogenesis in C3H/HeN newborn mice was also examined.

Results: We found that expression of FGF-13 mRNA is comparable to, or higher than, that of other FGFs known to regulate hair growth and wound healing.  Unlike other FGFs, the distribution of FGF-13 mRNA and protein in adult mice was mainly restricted to cells in the bulge region of hair follicles, though lower levels were detected with less frequency in keratinocytes in the basal layer of the epidermis.  FGF-13 protein was detectable in the bulge region throughout the hair growth cycle, but its distribution was especially wide during telogen and early anagen.  During hair follicle morphogenesis in newborn mice, FGF-13 protein was first detected in the bulge region and basal layer keratinocytes 3 days after birth. 

Conclusions:  We demonstrate for the first time the presence of high levels of FGF-13 [or FGF-homologous factor (FHF)-2] in the bulge region of hair follicles.  These findings suggest that FGF-13 may play a role in regulating the function of cells in the bulge region and basal layer of the epidermis.