Student Research: Sean M. Harris
Current models of reproductive toxicity can be expensive, time consuming and require a large number of animals. While new in vitro methods have the potential to aid in reducing these burdens, the use of alternative models of male reproductive development has been limited by difficulties in modeling the complex cellular interactions and multiple endpoints which are involved in processes such as germ cell differentiation in the testes. Our lab has developed a new 3-dimensional model of male reproductive development. This cellular co-culture system (3D-TCS) contains several rat testes cell types (Sertoli, germ and Leydig cells) grown in a three dimensional conformation facilitated by an extracellular matrix (ECM) overlay. The addition of ECM in this co-culture model results in a more physiologically stable system and cells form a testicular-like architectural structure representative of in vivo characteristics of seminiferous tubules. We sought to characterize the responses in the 3D-TCS to an array of diverse chemicals across multiple endpoints in order to assess which aspects of in vivo testicular toxicity are reflected in the model. Transcriptomic responses after phthalate ester exposure in the 3D-TCS were compared to responses in in vivo testes. These analyses showed that transcriptomic responses in the 3D-TCS reflect key aspects of phthalate toxicity in vivo. We also analyzed the metabolism of phthalate esters and the kinetic behavior (partitioning) of the both phthalate parent compounds and the main metabolite in the 3D-TCS. In addition, potency of cytotoxic, inflammatory and endocrine disruption endpoints were also evaluated across a diverse set of 5 compounds in order to characterize the range of toxicity signals captured by the model. These studies have demonstrated that the 3D-TCS can be used in a medium throughput format to investigate responses which cover a wide range of testes toxic responses in a manner that in informative of the mechanism of toxicity and the dynamic processes which occur across time and dose.