Hair Growth Cycle Affects Hair Follicle Destruction by Ruby Laser Pulses  Tai-Yuan David Lin, Woraphong Manuskiatti, Christine C. Dierickx, William A. Farinelli, Marnie E. Fisher, Thomas Flotte, Howard P. Baden, R. Rox Anderson  Journal of Investigative Dermatology  Volume 111, Issue 1, Pages 107-113 (July 1998) DOI: 10.1046/j.1523-1747.1998.00227.x Copyright © 1998 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 1 Laser exposure on anagen day 6 selectively damages follicular epithelium over its entire length. Laser irradiation led to a heterogeneous and widespread thermal injury to follicular epithelium but not the neighboring dermis (a, b). The fluence level was 3.16 J per cm2×one pulse. Normal histology (c) from the age-matched unirradiated control is shown for comparison. Scale bar: (a, c) 200 μm, (b) 100 μm. Journal of Investigative Dermatology 1998 111, 107-113DOI: (10.1046/j.1523-1747.1998.00227.x) Copyright © 1998 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 2 Follicular damage immediately after laser exposure is absent during catagen or telogen, and fluence dependent during anagen. 0, No damage; 1, mild; 2, moderate; 3, severe; A, anagen; C, catagen; T, telogen. The number in parentheses indicates the sample size. Error bars: SD. Journal of Investigative Dermatology 1998 111, 107-113DOI: (10.1046/j.1523-1747.1998.00227.x) Copyright © 1998 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 3 Selectivity of thermal injury to follicles is lost at high fluences, given on anagen day 14. The fluence level was 3.16 J per cm2×one pulse. Note the damage to the entire follicular epithelium. In addition, there was thermal denaturation of the collagen and overlying epidermis. The asterisks mark the boundary between the irradiated tissue on the left and the unirradiated skin on the right. Scale bar: 200 μm. Journal of Investigative Dermatology 1998 111, 107-113DOI: (10.1046/j.1523-1747.1998.00227.x) Copyright © 1998 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 4 Full hair regrowth occurs 28 d after laser exposure given during catagen or telogen, whereas regrowth after exposure given in anagen is fluence dependent. 0, No regrowth; 1, sparse; 2, moderate; 3, full; A, anagen; C, catagen; T, telogen. The number in parentheses indicates the sample size. Error bars: SD. Journal of Investigative Dermatology 1998 111, 107-113DOI: (10.1046/j.1523-1747.1998.00227.x) Copyright © 1998 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 5 Full hair regrowth occurs 56 d after laser exposure given during catagen or telogen, whereas regrowth after exposure given in anagen is fluence dependent. 0, No regrowth; 1, sparse; 2, moderate; 3, full; A, anagen; C, catagen; T, telogen. The number in parentheses indicates the sample size. Error bars: SD. Journal of Investigative Dermatology 1998 111, 107-113DOI: (10.1046/j.1523-1747.1998.00227.x) Copyright © 1998 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 6 Fibrosis is seen at 28 d after a high fluence laser exposure on anagen day 6. (a) Low power magnification demonstrates the decreased number of hair follicles as compared with the age-matched unirradiated control (d). (b) Intermediate magnification illustrates fibrosis. (c) High power magnification illustrates dermal melanophages in the area of fibrosis. The fluence level was 3.16 J per cm2×one pulse. Scale bars: (a, b, d) 200 μm, (c) 100 μm. Journal of Investigative Dermatology 1998 111, 107-113DOI: (10.1046/j.1523-1747.1998.00227.x) Copyright © 1998 The Society for Investigative Dermatology, Inc Terms and Conditions