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Int J Cancer. 2011 Nov 30. doi: 10.1002/ijc.27379. [Epub ahead of print] Treatment for chemotherapy-induced hair loss in mice using parathyroid hormone agonists and antagonists linked to a collagen binding domain. Katikaneni R, et al Abstract Parathyroid hormone (PTH) agonists and antagonists have been shown to improve hair regrowth after chemotherapy; however, rapid clearance and systemic side-effects complicate their usage. To facilitate delivery and retention to skin, we fused PTH agonists and antagonists to the collagen binding domain of Clostridium histolyticum collagenase. In-vitro studies showed that the agonist fusion protein, PTH-CBD, bound collagen and activated the PTH/parathyroid hormone-related peptide (PTHrP) receptor in SaOS-2 cells. The antagonist fusion proteins, PTH(7-33)-CBD and PTH([-1]-33)-CBD, also bound collagen and antagonized PTH(1-34) effect in SaOS-2 cells; however, PTH(7-33)-CBD had lower intrinsic activity. Distribution studies confirmed uptake of PTH-CBD to the skin at 1 hour and 12 hours after subcutaneous injection. We assessed in-vivo efficacy of PTH-CBD and PTH(7-33)-CBD in C57BL/6J mice. Animals were depilated to synchronize the hair follicles; treated on day 7 with agonist, antagonist, or vehicle; treated on day 9 with cyclophosphamide (CYP) (150 mg/kg i.p.) or vehicle; and sacrificed on day 39. Normal mice (no chemo, no treatment) showed rapid regrowth of hair and normal histology. Chemo+Vehicle mice showed reduced hair regrowth and decreased pigmentation; histology revealed reduced number and dystrophic anagen/catagen follicles. Chemo+Antagonist mice were grossly and histologically indistinguishable from Chemo+Vehicle mice. Chemo+Agonist mice showed more rapid regrowth and repigmentation of hair; histologically there was a normal number of hair follicles, most of which were in the anagen phase. Overall, the agonist PTH-CBD had prominent effects in reducing chemotherapy-induced damage of hair follicles, and may show promise as a therapy for chemotherapy-induced hair loss. © 2011 Wiley-Liss, Inc. Edited for blog use