Background: Embryo implantation is a complex process regulated by interactions between endometrial epithelial and stromal cells. The endometrium plays a critical role in this process, providing a supportive environment for embryo attachment. However, conventional 2D cell culture models fail to fully replicate the complex 3D structure and cellular interactions of the endometrium. To overcome these limitations, 3D organoid models have been developed to better mimic the in vivo endometrial environment. Methods: In this study, a multicellular uterine organoid model was developed using porcine endometrial epithelial cells (pEECs) and porcine endometrial stromal cells (pESCs) to evaluate the effects of the endometrial environment on embryo implantation. First, single-cell endometrial organoids (pEOs) were formed by culturing pEECs in Matrigel, and their basic cellular characteristics were assessed. Then, a multicellular uterine organoid model was established by combining pEOs with pESCs. Finally, porcine embryos were co-cultured with this model to examine its effect on embryo attachment. Results: The multicellular uterine organoid model facilitated embryo attachment, demonstrating that the 3D structure and cellular interactions of the endometrium play a significant role in embryo implantation. The presence of both epithelial and stromal cells contributed to a more physiologically relevant environment that supported embryo adhesion. Conclusions: This study demonstrates that a multicellular uterine organoid model can serve as a useful in vitro system for porcine embryo implantation research. This model may contribute to a better understanding of embryo development and implantation mechanisms, with potential applications in regenerative medicine and biotechnology.

Organ size control is a fundamental developmental processes for higher plants as well as a promising target trait for molecular breeding in crop plants. Genetic mechanisms how plant organs grow to a certain size remains still unclear. Here we present the identification and characterization of a genetic mutant, big flower1-1 (bif1-1) in Arabidopsis that exhibits bigger organ size primarily due to increased cell size. Genetic analysis indicated that it is a single, semi-dominant mutation. Phenotypic analysis showed that bif1-1 exerts pleiotropic effects: it caused bigger seed size, bigger seedling, bigger leaf, thicker stem, increased trichome branching, smaller fruit, and bigger pollen. Microscopic analysis suggested that the bigger organ size in bif1-1 mutant is primarily attributed to increased cell size. Gene expression analysis indicated that most of growth-control genes tested were not altered in bif1-1 mutant. Instead, expression of ARGOS and auxin-inducibility of ANT were reduced in bif1-1 mutant. Our ongoing positional on the corresponding gene would not only shed light on the molecular mechanisms how plants adopt final organ size but also provide a promising genetic resource for genetic engineering of flower- and seed-size in crop plants.