3D microenvironments for gonadal cell development in domestic cats and dogs.

The development of functional gametes in vitro depends on the ability to recreate the complex gonadal niche that orchestrates germ cell survival, growth and differentiation in vivo. In vitro gametogenesis therefore relies on the design of appropriate three-dimensional (3D) microenvironments capable of providing structural and biochemical support to gonadal cells. These approaches hold considerable promise for fertility and biodiversity preservation, particularly in prepubertal individuals and endangered species. Although complete in vitro follicle growth to the metaphase II oocyte stage has been achieved in rodents and humans and in vitro spermatogenesis has been obtained in murine models, translation to small domestic animals remains challenging. Dogs and cats are of particular interest both as target species and as comparative models for their wild counterparts, but their peculiar reproductive physiology limits the direct application of protocols developed in other mammals. In this context, advanced 3D culture systems, including hydrogel encapsulation, organoids, air-liquid interface platforms, biomimetic scaffolds and microfluidic devices, are being explored to better mimic ovarian and testicular microenvironments. The present review summarizes current advances in 3D microenvironments, with a focus on those designed for gonadal cell culture in small animals, highlighting species-specific challenges, key achievements and future directions toward in vitro gametogenesis.