Monochorionic-twin-on-a-chip for investigating fetal organ growth and metabolism

Placental vascular anastomoses are a relatively common occurrence in monochorionic twin pregnancies, potentially leading to unbalanced blood supply to the developing twins, higher rates of perinatal mortality and long term morbidity. Unfortunately, our understanding of these conditions and their treatment strategies remains limited due to the lack of suitable in vitro and vivo twin models. Herein, we presented a microfluidic-based Monochorionic-Twin-on-a-Chip (MTOC) model designed to simulate monochorionic diamnionic (MCDA) pregnancies. The aim was to model the impact of an unbalanced nutrition supply on fetal organ growth using hepatic cells grown in vitro. Our findings confirm that an unbalanced nutrition supply from the donor circulation reduces cellular growth relative to the recipient system. This recapitulates the situation of the smaller (donor) and larger twins (recipient) within an MCDA pregnancy in vivo. Furthermore, hepatic cells exposed to the donor circulation exhibited a relative hypoxia state. Metabolite profiling of intracellular, extracellular, and biomass samples from small twins revealed lower levels of amino acids, fatty acids, and TCA cycle intermediates compared to large twins. Additionally, 13C metabolic flux showed upregulation of TCA cycle activity in the large twin, whereas the small twin would utilize more glutamine for energy supply and lipid synthesis. These results suggest that the unbalanced nutrient supply associated with some MC twin pregnancies restricts fetal liver growth in association with altered metabolic profiles. Moreover, our MTOC model represents a novel system for studying a range of other physiological intrauterine environments and pregnancy outcomes associated with MC twin pregnancies.