The goal of this research is to advance the understanding of a novel mechanism by which cells detect hydrostatic pressure as part of biological events. Although pressure, such as arterial and intracranial pressure, is experienced and regulated throughout the body, conventional thinking is that cells cannot directly sense pressure changes. However, numerous in vitro studies have demonstrated that when cells were subjected to elevated pressures, they exhibited an increase in cell proliferation, cytoskeletal reorganization, and a number of other cellular-/molecular-level changes. Because cells are assumed to be incompressible under physiological-levels of pressure, cell deformation as a mechanism for pressure sensing by cells has generally been ruled out. A novel experiment was devised to probe this conventional tenet, and volume changes in bladder urothelial cells exposed to pressure were quantified. Notably, application of pressure as low as 10 cmH2O caused rapid cell volume increases. Moreover, exposure to this level of pressure resulted in increased release of ATP from these cells.
Based on these preliminary findings, it is hypothesized that elevated pressure activates membrane-bound sodium channels, which increases intracellular sodium concentration and influx of water to induce cell swelling. This can lead to further activation of stretch-sensitive calcium channels, which has been shown to trigger downstream events, such as release of ATP.
The objective of this research is to test the novel hypothesis that sensing of hydrostatic pressure occurs via cell-swelling. In the proposed 3-year project, a custom perfusion chamber and optical imaging techniques will be used to quantify changes in cell volume and ATP release by bladder urothelial cells exposed to hydrostatic pressure. By altering the ion composition of perfusion media and blocking select ion channels during pressure application, potential mechanisms for this phenomenon will be determined. The three research aims are as follows. 1) To elucidate the role of Na+ in pressure-induced cell swelling of urothelial cells 2) To elucidate the role of pressure-induced cell swelling in ATP release by urothelial cells 3) To determine if cell-swelling is a common mechanism for pressure sensing in multiple cell types
This research will be conducted by a graduate student as part of his/her doctoral thesis under supervision of the PI; the student will also enroll in "BIOE 850: Mentoring undergraduate teams." Aspects of the research activity will be designated as 10-week-projects for summer interns to be recruited from minority-serving South Carolina colleges.
Intellectual Merit: An understanding of the mechanism for cell swelling under pressure, a fairly counterintuitive event, and investigation of the parallels in reaction to pressure in cells of many different organs could completely transform our understanding of pressure-sensing and regulation in the body. When the hypothesized pressure-sensing mechanism is accurately described, it may be applied to other areas of engineering research, such as bio-inspired sensors and tissue regeneration. Moreover, the research findings are expected to provide explanations for previous observations that various types of cells respond to pressure and facilitate further research in the field of cell mechanics and mechanobiology.
Broader Impacts: Deficiency in the body's innate ability to regulate pressure in the arteries, veins, eyes, and cranial cavity can lead to a number of life-threatening complications that affect millions of people. Looking beyond the traditional baroreceptor theory and identifying the actual cellular pressure-sensing mechanism can help develop treatment and preventative measures for various pressure-related diseases. The proposed research will provide graduate and undergraduate students an opportunity to make discoveries while mastering research skills including communication and dissemination of data. The summer internship will increase participation of SC students from underrepresented groups in STEM research. The findings will be disseminated to broad audiences through publications and outreach to the local community.
