Two new male contraceptives exert their effects by depleting germ cells prematurely from the testis
Cheng,Chuen-yan; Silvestrini,Bruno; Grima,Josephine; Mo,Meng-Yun; Zhu,Li-Ji; Johansson,Elof D.B.; Saso,Luciano; Leone,Maria Grazia; Palmery,Maura; Mruk,Dolores D.
Biology of Reproduction 65(2): 449-461
Publication date: 2001
The three currently available male contraceptive approachesare 1) the barrier method such as the condom, 2) hormonal methodsby disrupting the pituitary-testicular axis so as to impairspermatogenesis, and 3) immunological methods by preparing vaccinesagainst male-specific antigens. We hereby describe an alternativeapproach in which attachments of developing germ cells ontothe seminiferous epithelium are disrupted, thereby inducingtheir premature release into the tubular lumen. This in turnleads to infertility. A panel of analogues based on the corestructure of 1-(2,4-dichlorobenzyl)-indazole-3-carboxylic acidwas synthesized. These compounds were subjected to an in vivoscreening assay assessing their effects in inducing the expressionof testin, a testicular marker whose expression correlates withthe integrity of Sertoli-germ cell junctions. An induction oftestin expression in the testis signifies a disruption of Sertoli-germcell junctions that is followed by depletion of germ cells fromthe seminiferous epithelium. Two compounds, namely 1-(2,4-dichlorobenzyl)-indazole-3-carbohydrazide(AF-2364) and 1-(2,4-dichlorobenzyl)-indazole-3-acrylic acid(AF-2785), were identified that caused detachment of germ cells,in particular round and elongated spermatids, from the epitheliuminducing their premature release into the tubular lumen as confirmedby histological analysis. Adult rats receiving several oraldoses of either one of these compounds became infertile within3-7 wk after the epididymal sperm reserve was exhausted.Depending on the dosing of the administered compound, rats becameinfertile for 4-14 wk before their fertility graduallybounced back, illustrating the reversibility and efficacy ofthese new compounds. Also, these compounds did not appear toimpair the hypothalamus-pituitary-testicular axis because theserum levels of LH, FSH, and testosterone of the treated animalsdid not change significantly when compared to control rats.In addition, results of serum microchemistry illustrate thatliver and kidney function was not affected in animals treatedwith both compounds.