A spatial model showing differences between juxtacrine and paracrine mutual oocyte-granulosa cells interactions

Oocyte-granulosa cell communication involves multiple signaling mechanisms. Prior research has shown that these cells exchange factors through local feedback loops. However, the spatial differences between juxtacrine and paracrine interactions remain unclear. This gap motivated the development of a spatial model to study these interactions. No prior work had resolved how the physical distance between cells affects signaling outcomes. It was already known that GDF9 and BMP15 are secreted by oocytes. Yet, the comparative effects of direct versus indirect cell contact on these factors had not been fully explored. This study aimed to address that uncertainty. The findings may help improve in vitro maturation protocols.

This study aimed to compare juxtacrine and paracrine communication between porcine oocytes and granulosa cells. The researchers proposed to use a transwell system to simulate paracrine interactions. They wanted to determine how physical contact influences oocyte-secreted factors. The motivation was to understand how cell proximity affects developmental outcomes. The study also sought to assess steroid hormone levels and gene expression differences. The authors hypothesized that direct contact would yield distinct results compared to indirect co-culture. They focused on blastocyst development rates and granulosa cell viability. The goal was to propose a new model for studying follicular cell interactions.

The study used a transwell system with 0.4 μm polyester membrane inserts. Oocytes and granulosa cells were co-cultured in a defined maturation medium. Two groups were established: direct contact (juxtacrine) and paracrine (2 mm apart). Cultures lasted 44 hours at controlled conditions. Researchers measured oocyte-secreted factors like GDF9 and BMP15 over time. Steroid hormone levels and gene expression were analyzed using mRNA quantification. Granulosa cell counts were monitored to assess viability. The blastocyst development rate was evaluated after parthenogenetic activation.

Oocyte-secreted factors decreased over time in direct contact cultures. In contrast, these factors increased in paracrine co-cultures. Blastocyst development was higher in direct contact (20%) than in paracrine (11.5%). Granulosa cell counts dropped significantly in direct contact groups. Steroid levels and enzyme mRNA showed significant changes in both groups. CX43 expression was higher in granulosa cells with direct contact. The differences suggest that physical proximity alters signaling dynamics. These findings support a new model for follicular cell interactions.

The authors propose that juxtacrine and paracrine interactions differ in their effects on oocyte-granulosa communication. The study suggests that direct contact leads to lower oocyte-secreted factor levels. Paracrine co-culture showed increased factor expression over time. Blastocyst development rates support the importance of physical proximity. Granulosa cell viability was reduced in direct contact groups. Steroidogenesis and CX43 expression varied between the two systems. These results indicate distinct signaling mechanisms in each interaction type. The findings may guide future studies on follicular cell communication.