Masters Theses

Date of Award

12-1994

Degree Type

Thesis

Degree Name

Master of Science

Major

Engineering Science

Major Professor

Judy L. Cezeaux

Committee Members

John H. Forrester, William R. Jacobs

Abstract

Cardiac hypertrophy, a remodeling of the ventricular wall of the heart, is a major risk factor associated with myocardial failure, the most common cause of heart failure in the United States. Left ventricular hypertrophy is an increased protein synthesis response of cardiac cells to a number of stimuli including mechanical loading and products of the renin-angiotensin system. This investigation initiates a study of the relationship between mechanical loading and the renin-angiotensin system in cultured cardiac non-myocytes and myocytes. Particularly, this thesis examines alterations in renin mRNA levels as a response to mechanical stretching of non-myocyte cells cultured from neonatal rats. Driving this study was the hypothesis that mechanical stretch of non-myocytes would cause an increase in renin mRNA levels. This hypothesis is based on the fact that the renin-angiotensin system has been implicated in myocyte hypertrophy and may also have autocrine effects in non-myocyte hyperplasia.

A mechanical stretching device was used to apply a static uniaxial stretch of 10% to cultured cardiac non-myocyte cells for a period of 24 hours. Unstretched cells served as experimental controls. Renin mRNA levels were measured in both the stretched and unstretched cells using the reverse transcription polymerase chain reaction method. The amount of renin mRNA in stretched cells was compared to unstretched cells to determine if a significant increase in renin message occurred following exposure to stretch.

Results indicate that pure cultures of non-myocytes were obtained and easily grown to confluency on fibronectin coated silicone membranes. RT-PCR was performed on rat kidney homogenates and cultured cardiac non-myocytes grown in tissue culture dishes and found to be an effective method for amplifying renin mRNA. It was also found that RT-PCR was valid in amplifying the renin message from stretched and unstretched non-myocytes adhered to silicone membranes. The results do not indicate that a significant increase in renin mRNA occurred in response to the stretch stimulus. These results do not agree with the hypothesis stated earlier.

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