Exposure to Bisphenol A affect the size, viability, and maturation of pig testicular tissue ectopically grafted in immunocompromised mice
Authors: Rodriguez-Sosa Jose Rafael , Ruiz Saul , Valdez Dominik , Tullot Tony 
Published: April 2020

Bisphenol A (BPA) is a plastic additive, specially of polycarbonates and epoxy resins, as it imparts transparency, flexibility, and durability. BPA‐containing plastic is present in a great variety of common consumer products, such as water bottles, food packaging, and coating of food cans. BPA leaches from these products into the environment and is detectable in humans, animals, and drinking water sources. In rodents, BPA exhibits estrogen‐like properties and has detrimental effects on testicular maturation and function. Currently the effects of BPA in other species are still unclear. However, the studies that are necessary to elucidate the effects of potentially toxic compounds on the testes of non‐rodent species are logistically difficult and ethically prohibitive. One alternative is using mice as bioincubators to grow testicular tissue of large animals and then expose these mice to those compounds. In this technique, small pieces of immature testes transplanted from these animals into adult castrated immunocompromised mice, survive and fully mature. In order to investigate the effects of BPA on the testes of other species, we grafted piglet testicular pieces (~1 mg, 8 pieces / mouse) under the dorsal skin of adult castrated NCr nude mice. After two weeks of grafting, mice (n=10) were treated daily by oral gavage for 26 weeks (the approximate time in which pig testicular tissue reaches full maturity in mice) with 10 mg/kg of BPA in corn oil as vehicle. As control, we exposed an equal number of mice to the same volume of corn oil. The experimental dose of BPA is lower than the lowest adverse effect level (LOAEL, 50 mg/kg) for humans, which is the currently accepted by the US Environmental Protection Agency. At sacrifice, neither the weight of mice nor their liver were affected by treatment (P > 0.05), indicating that subsequent effects of treatment on the grafted tissue were a result of direct BPA exposure and not due to indirect systemic toxicity induced by this compound. The rate of graft recovery was not affected by treatment either; 65.62 vs 58.33 % of the transplanted pieces were recovered from the treated and control mice, respectively (P>0.05). However, the graft weight was significantly reduced by BPA; 24.56 ± 4.33 vs 43.62 ± 5.36 mg (P<0.05). Moreover, the rate of graft viability (defined as the presence of viable seminiferous tubules in the graft) was significantly reduced in treated mice as well (30.43 vs 70.00 % in treated and control groups, respectively, P<0.05). Some seminiferous tubules in grafts of both groups of mice reached full maturity (full spermatogenesis; presence of elongated spermatids in the seminiferous epithelium), but the number of these tubules was lower in the BPA‐treated group; 2.43 vs 8.89 % (P<0.05). In summary, exposure to BPA at these low levels results in reduced size, viability, and maturation of the piglet testicular tissue ectopically grafted in mice. This strongly suggests that the testes of non‐rodent animals are also susceptible to the detrimental effects observed in rodents with exposure to BPA.

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Midwestern University intramural funds