Spring 2020 – Deviation from Murray’s Law under Hyperglycemic and Hyperketonic Enviornments in the Chick Chorioallantoic Membrane Model

Under normal conditions, endothelial shear stress stimulates nitric oxide production by endothelial nitric oxide synthase (eNOS), a critical mechanism for stimulating acute dilation and chronic growth of blood vessels. When vessel growth properly regulates endothelial shear stress, the radii of arterioles at a branch follow a specific pattern, known as Murray’s Law: the cube of the mother radii is equal to the sum of the cube of daughter vessel radii. Although in vitro exposure to glucose and ketones downregulate and upregulate eNOS, respectively, the impact on the radii of arterioles in vivo has not been evaluated. Conventional microvascular animal models limit access to an intact microvascular network, and radii are impacted by anesthesia, surgical trauma, and inflammation. In contrast, the ex-ovo chick chorioallantoic membrane (CAM) model allows access to the entire arteriolar network over the course of successive days as blood flow (and thus endothelial shear stress) increases. Therefore, the purpose of the present work is to determine the feasibility of the CAM model to test the hypothesis that chronic exposure to hyperglycemic and hyperketonic environments will cause deviation from Murray’s Law. Four critical requirements have been identified: 1) mapping microvessel networks, allowing return to particular branches on consecutive days, 2) antibiotic use and aseptic techniques, minimizing infection, 3) regulating temperature and humidity during measurements, maintaining long-term viability, and 4) measuring branching patterns of control and experimental subjects. Preliminary experimentation has shown all requirements as attainable, and it is therefore feasible to use the chick CAM model.