Women are known to experience higher rates of meniscal injury and poorer medical outcomes throughout life, but the mechanisms underlying these sex based differences are unclear. In order to study sex differences in the knee meniscus, we gather primary cells from meniscus repair surgeries to create a bank of primary meniscal fibrochondrocytes. We then utilize hanging drop spheroids to create a small 3D piece of tissue in order to study sex differences in their response to exogenous signaling factors.

Women are also two times more likely to experience an abnormality in the meniscus called a discoid meniscus, where the meniscal tissue covers more of the articulating surface than what is normally expected. The discoid meniscus is poorly characterized, with limited information being available for any in vitro work. Therefore, we have since performed transcriptomic sequencing on our bank of primary meniscal fibrochondrocytes to investigate differences; not only to better characterize the discoid meniscus, but to be able understand potential mechanisms for the observed sex differences.

Phenol red is a ubiquitous additive to cell culture media, where it can act as a non-steroidal estrogen. Additionally, fetal bovine serum (FBS) is also commonly added to cell culture media and contains exogenous hormones. We are currently investigating the effects of the exogenous estrogens on human mesenchymal stem cells (MSCs) in order to better understand the impact common culture conditions have on MSCs, which are commonly used in tissue engineering applications.

We have also identified some evidence of sex differences in mechanosensing in primary human meniscal fibrochondrocytes. Utilizing our mechanically tunable pentenoate-functionalize hyaluronic acid hydrogel system, we are able to observe differences in cell spreading in male and female cells on hydrogels of low, medium, and high stiffness. These morphological differences we observe have laid the foundation for further work investigating the mechanisms for mechanotransduction in meniscal fibrochondrocytes, how these mechanisms differ based on biological sex, and how this knowledge can be leveraged to control sex-specific tissue regeneration.