DESCRIPTION (provided by applicant): Charles Corey Hardin MD, PhD is a fellow both in the Division of Pulmonary and Critical Care Medicine at Massachusetts General Hospital and in the Molecular and Integrative Physiology Program at the Harvard School of Public Health. He will become a staff physician in the Pulmonary and Critical Care Division at Massachusetts General Hospital in July of 2011. He has a background in biological physics and pulmonary and critical care medicine. His doctoral research focused on statistical mechanics of glassy biological materials, while his post-doctoral research focuses on dynamics of the cytoskeleton. He is the author of five first-author papers. His most recent work, which is in review, and on which he is co-first author, describes the first direct measurement in cellular monolayers of the distribution of intercellular forces at cell-cell junctions[1]. Building on that advance, in the prsent K25 application he will test the hypothesis that the intrinsic mechanical properties of the cytoskeleton in pulmonary endothelial cells are major determinants of the distribution of these intercellular forces. He will also test the two corollary hypotheses that 1) these mechanical properties change in predictable ways in models of acute lung injury and the Acute Respiratory Distress Syndrome (ARDS), and 2) that such changes compromise endothelial barrier function. As a study in experimental cellular biology, this work marks a departure from Dr. Hardin's graduate work in theoretical physics. As such, a mentored K25 will provide the support necessary to pursue ongoing training and research. Ultimately, this career development grant will form the foundation upon which Dr. Hardin will become a successful independent investigator. Environment: Prof. Jeffrey Fredberg will serve as Dr. Hardin's primary mentor. Prof. Fredberg is a renowned pulmonary physiologist who has made seminal contributions to the study of asthma and, more recently, to the experimental study of cell mechanics more broadly. He has an excellent track record in training new investigators, having served as primary mentor for 41 past and present doctoral and post-doctoral trainees. Of those who have completed their training, nine have gone on to become independent principal investigators, seven have earned tenure and six are full professors. He is also PI of a recently renewed T32 training grant in interdisciplinary pulmonary sciences and 2 new RO1 grants. The interdisciplinary work from his laboratory has been widely noted[2-5]. Dr. Hardin will also enjoy close collaborations with other eminent physiologists and clinicians with whom Prof. Fredberg maintains close ties including Dr. James P. Butler and Dr. Atul Malhotra. The Harvard School of Public Health is in close proximity to the Massachusetts General Hospital, Brigham and Women's Hospital, and Harvard Medical School, thus providing an excellent intellectual environment. Dr. Hardin will also have a staff appointment at the Massachusetts General Hospital, where he will enjoy close collaboration with experts in ARDS such as Dr. Taylor Thompson. Research: ARDS is a major cause of mortality[6]. Among the earliest events in the pathology of ARDS is the breakdown of the endothelial barrier[7], which occurs primarily because of the formation of gaps between endothelial cells[8]. A great amount is now known about the signaling cascades and biologic mediators involved, but far less is known about underlying cytoskeletal and mechanical events. A technique recently developed my colleagues and I (Monolayer Stress Microscopy or MSM) allows for the first time direct measurement of intercellular forces[1]. Combined with methodologies already invented in our lab to discover the surprising physical properties of the cell including cellular traction forces (Fourier Transform Traction Microscopy or FTTC[9, 10]) and cytoskeletal mechanics (Optical Magnetic Twisting Cytometry OMTC[11-15] and Cell Mapping Rheometry[12, 16]), we are now in a position to characterize comprehensively the mechanics of the pulmonary endothelial monolayer and its alteration in models of disease.

The Acute Respiratory Distress Syndrome (ARDS) is a major cause of mortality, caused in part by an alteration of the mechanical forces in the pulmonary endothelium that leads to pulmonary edema. The physical forces acting on the individual cell-cell junction within an intact endothelial monolayer have never been measured; here I propose a new technique in order to do just that. This technique will enhance the understanding of endothelial biology and serve as a platform with which to evaluate new therapies in ARDS.