2019 Basic Science Presentations

Kenneth J Bogenberger, MD, Dao H Ho, PhD; Tripler Army Medical Center

Objectives: Hemorrhagic shock as a result of trauma or surgical bleeding is frequently temporized with administration of vasopressors in order to augment systemic vascular resistance while resuscitation measures are employed.  This mimics the treatment strategy of other forms of shock where systemic vascular resistance is low and vasopressors are heavily relied upon to resuscitate the patient.  Blood vessels respond to direct exposure to vasopressin and norepinephrine via receptors on smooth muscle and endothelial cells and ultimately result in vasoconstriction which contributes to a low flow state and increases shear stress within vessels.  The effect of vasopressors on vascular cells with regard to direct cellular injury and repair has not been well-studied.  The objective of this study is to examine the in vitro effect of vasopressin and norepinephrine on the rate of healing of vascular cells after wounding.

Methods:  Wounding and measurement of healing rate of cells were performed using Electric Cell-substrate Impedance Sensing (ECIS) technology.  A specified area of a monolayer of cells was wounded via high electrical charge, and healing of the cell layer was assessed via measurement of resistance (ohms) over time.  Pig vascular smooth muscle cells (SMCs) and pig vascular endothelial cells (ECs) were seeded in 96-well plates. Immediately after wounding, cells were treated with either lysine-vasopressin (LVP; 0, 0.001, 0.01, 0.1, 1, 10, 100, 1000 ηM; n=6/group), or  norepinephrine (NE; 0, 0.001, 0.01, 0.1, 1, 10, 100, 1000 µM; n=6/group). Data were recorded continuously for another 18 hours.  Statistical comparisons were made using two-way ANOVA and Tukey HSD post hoc analysis (alpha level = 0.05).

Results: When SMCs were injured, NE treatment significantly suppressed healing rate over the course of 10 hours (Time x Dose, F(133,665) = 1.955, p<0.0001), whereas LVP had minimal effect on healing of SMCs (F(133,665) = 0.6346, p=0.999).  When ECs were injured, both NE (F(133,665) = 3.716, p<0.0001), and LVP (F(133,665) = 3.058, p<0.0001) significantly suppressed rate of healing.

Conclusions: NE significantly suppressed the wound healing response of both SMCs and ECs, whereas LVP suppressed wound healing of ECs only.  This strongly suggests that the use of different vasopressors during treatment and resuscitation can elicit unique effects on vascular healing in the body.  We plan to further explore the physiological effects of vasopressors on post-injury healing of blood vessels to aid in optimizing resuscitation strategies that reduce vascular injury and end organ damage in the period after recovery from trauma and shock.