Hypertension-linked mechanical changes of rat gut

Abstract

Hypertension is the most prevalent risk factor for cardiovascular disease caused by a persistent increase in arterial blood pressure that has lasting effects on the mechanical properties of affected tissues like myocardium and blood vessels. Our group recently discovered that gut dysbiosis is linked to hypertension in several animal models and humans; however, whether hypertension influences the gut’s mechanical properties remains unknown. In this study, we evaluated the hypothesis that hypertension increases fibrosis and thus mechanical properties of the gut. A custom indentation system was used to test colon samples from Wistar Kyoto (WKY) normotensive rats and Spontaneously Hypertensive Rats (SHR). Using force-displacement data, we derived an steady-state modulus metric to quantify mechanical properties of gastrointestinal tissue. We observed that SHR proximal colon has a mean steady-state modulus almost 3 times greater than WKY control rat colon (5.11 ± 1.58 kPa and 18.17 ± 11.45 kPa, respectively). These increases were associated with increase in vascular smooth muscle cells layer and collagen deposition in the intestinal wall in the SHR.

Characterization of the mechanical properties of resected porcine organ tissue using optical fiber photoelastic polarimetry

“…The experimentally determined range of elastic modulus values using the optical fiber PEP method and QLV fit is 0.1-0.5 KPa for liver, 0.15-0.9 KPa for kidney, and 0.2-8.0 KPa for pancreas. Our results are within the range of previously published elastic modulus values [1,2,[20][21][22][23][24]. Previously reported elastic modulus values vary due to several factors, including the animal model, sample preparation method, and mathematical fit used.…”

“…The general trend in the measurements is as the strain increases the elastic modulus increases. This behavior is commonly observed in viscoelastic materials [2,20]. The experimentally determined range of elastic modulus values using the optical fiber PEP method and QLV fit is 0.1-0.5 KPa for liver, 0.15-0.9 KPa for kidney, and 0.2-8.0 KPa for pancreas.…”

“…Compressive testing is one of the most robust methods for measuring the mechanical properties of tissues due to the large range in Young's Modulus values, from 50Pa-5GPa [1,2]. However, current techniques either suffer from poor spatial resolution or require destructive sample processing.…”

Hypertension-Linked Pathophysiological Alterations in the Gut

“…First, we investigated if the integrity of the gut epithelial barrier is altered in the spontaneously hypertensive rat (SHR) model using various techniques: (i) oral fluorescein isothiocyanate (FITC)-dextran for epithelial permeability, (ii) an innovative Multi-Scale Indention (MSI) System to measure gut wall stiffness 24, 25 , and (iii) Western blotting for tight junction proteins. Both young pre-hypertensive and adult SHR with established hypertension along with age-matched, normotensive Wistar Kyoto rats (WKY) were used to investigate gut associations with BP (Fig.…”

The Gut Microbiome, Energy Homeostasis, and Implications for Hypertension

“…In a recent case-report, a potent antihypertensive effect was observed in a human with resistant hypertension [50]. Further, changes in intestinal structure and function correlate with hypertension in the SHR model [51], and thus it is proposed that a bi-directional relationship between host cardiovascular function and gut bacteria exists, which may involve a complex interaction among hypothalamic inflammation, the autonomic nervous system, and host immune functions [52, 53]. How these mechanisms cross-talk with energy homeostasis remains speculative but not unexpected, given the implication of such systems and pathways in the control of host RMR [54–57].…”