Hypertension III: Flow-Induced Vascular Remodeling

David A. Tulis
damit@ruf.rice.edu

� Thank you kindly for your note and comments. �Yes, indeed, the duration of our study was 7 days, and therefore we cannot ascertain whether the changes observed at this time point (ie, cellular hypertrophy and/or nuclear polyploidy) will eventually lead to enhanced cellular hyperplasia as the cell cycle procedes which might be observed at later time points. �If indeed we have cellular hyperplasia in the larger ileal artery and cellular hypertrophy in the second-order vessel (as observed), then this regional heterogeneity in vascular responses might be explained by differential GF expression. �The ileal artery demonstrated significant medial expression of PDGF-A after 24 hours, with subsequent endothelial expression at 3 and 7 days. �In addition, we found significant endothelial expression of PDGF-B after 7 days in the ileal artery (data not illustrated). �This GF induction was not observed in the smaller second-order branch; therefore, the highly replicative state of cells in the ileal artery might be directly due to an exaggerated GF expression which was not observed in the smaller branch vessel. � � �

� In terms of connective tissue results, we used a modification of Masson's Trichrome Stain to stain all connective tissue; therefore, we cannot distinguish between the different components found in the ECM such as elastin and various forms of collagen. �The percent of medial wall occupied by ECM components was between 29% and 34% in the control vessels, and between 34% and 41% in the high flow vessels. �As the vessel walls hypertrophied in response to elevated flow, a concomitant increase in ECM components was observed in an effort to maintain a normal vessel wall environment.

�I hope these comments adequately address your questions. �If you have any additional questions or comments, please do not hesitate to contact me.

�Very truly yours,

David A. Tulis