P4.35 HAIR CYCLE SPECIFIC IMMUNOLOCALIZATION OF RETINOIC ACID SYNTHESIS MARKERS

Helen B. Everts, ***John P. Sundberg, *Lloyd E. King Jr., and David E. Ong

Departments of Biochemistry and * Medicine (Dermatology), Vanderbilt University Medical Center, Nashville, TN, USA, and ** The Jackson Laboratory, Bar Harbor, ME, USA

This study was performed to examine the sites of endogenous retinoic acid (RA) synthesis in cycling hair follicles. C3H/HeJ mice were wax stripped to initiate a synchronized anagen hair cycle and samples taken at various time points after depilation. Immunohistochemistry was performed with antibodies against one retinol dehydrogenase (eRoldh), two retinal dehydrogenases (Aldh1a2 and Aldh1a3, formally called Raldh2 and Raldh3), cellular retinol binding protein (Crbp) and cellular RA binding protein type II (Crabp2) involved in RA synthesis.  In early anagen, Crbp, eRoldh, and Crabp2 are expressed in the sebaceous gland or its duct. This expression alters through the hair cycle, with the greatest expression seen in Anagen IIIb.  In the downward growing hair follicle, Crbp, eRoldh and Aldh1a2 are expressed in early anagen, while Crabp2 expression occurs later during anagen at this site. In addition, expression in the bulb region (precortex and dermal papilla) of Crbp, eRoldh, Aldh1a3, and Crabp2 begins in mid anagen and extends throughout anagen.  Crabp2 is also expressed in the dermal papilla during telogen. The inner layer of the outer root sheath (or companion layer) expresses Crbp, Aldh1a3, and Crabp2 once it forms and throughout anagen.  Some hair fibers express Aldh1a3 and Crabp2 during anagen. During catagen the regressing part of the follicle expresses Crbp, Aldh1a2, and eRoldh. Throughout the hair cycle Aldh1a2 is expressed in the outer root sheath and stratum granulosum, while Crabp2 is expressed in the stratum corneum. This expression pattern indicates that endogenous RA may be important for: sebaceous gland function, hair follicle growth and regression, hair fiber growth and release from its sheath, and epidermal barrier function.