Dual closed-loop ex-vivo perfusion of the placenta:
From Dr. Fusch's previous work place we have long-standing experience with this exciting model. The ultimate goal of our work is to understand how the placenta contributes to the cytokine exposure of the fetus in pregnancies complicated by chorioamnionitis. Chorioamnionitis is an infection of the uterus usually caused by bacteria that can lead to severe inflammation of the mother. The fetus can subsequently become compromised because inflammatory cytokines are either transferred via the placenta or because they induce themselves placental cytokine production and release. Little is known about this mechanism, but there is convincing evidence that a systemic inflammatory response (FIRS) is detrimental for the developing brain and negatively impacts later neurodevelopmental outcome. In this regard it does not play a role whether inflammation in the infant is induced by a postnatal sepsis or by chorioamnionitis. The long-term aim of our research is to either block transplacental transfer or suppress placental production and release of cytokines into the fetal circulation.
During the last three years we have established the perfusion model at McMaster and we have also created some modifications of the perfusion chamber. We were able to demonstrate viability of the placenta even after 6 hours of perfusion.
In our lab, amasters thesis is actually being performed investigating the response of the placenta to LPS stimulation. LPS (i.e. lipopolysaccharid) is a breakdown product of gram-negative bacteria and as such a strong inducer of the inflammatory cascade. In our experiments we have found that LPS is indeed capable to induce a strong TNF-a response in the placenta. However, we surprisingly detected a significant TNF-a release in control experiments that are supposed to run LPS-free. We have identified bovine serum albumin (BSA) , one of the component of the perfusion buffer solution, as the source of contamination. In the meantime we are now able to establish LPS-free perfusions by altering components. However, we have also learned that there is a significant memory effect of the tubes and of the perfusion chamber once they have been flushed with the LPS contaminated buffer. While these findings are important for us to run our experiments with properly defined conditions, they imply on the other hand that most of the published placental perfusion studies using the established BSA source have been run under mild LPS stimulation. We are currently preparing a manuscript summarizing these findings. In order to characterize the experimental setup more in detail we are also actually studying the relationship between different LPS levels and inflammatory response.
Even though our lab is in close proximity to the L&D facilities and we are closely collaborating with Dr. deFrance from MFM/OB, we are still experiencing a shortage in placenta supply at McMaster; this is mainly due to a number of competing studies that need to have access to cord blood, but not to the placenta itself. We have started to address this issue with the research groups involved in this field and will hopefully establish an algorithm that can satisfy the needs of all groups.
In summary, we are expecting that this research will contribute to develop strategies to protect the developing fetus against these substances.