Hypertension contributes to exacerbated osteoarthritis pathophysiology in rats in a sex-dependent manner.

BACKGROUND: Hypertension is a common comorbidity of osteoarthritis (OA) with known autonomic dysregulation; thus, the autonomic nervous system may provide a shared underlying mechanism. The objective of this study was to examine the role of the autonomic nervous system in a preclinical model of OA and hypertension. METHODS: Experiments were conducted in spontaneously hypertensive rats and a normotensive control strain, including male and female rats. OA was surgically induced via medial meniscus transection with skin incision used as a sham control (n = 7-8/strain/sex/surgery). Tactile sensitivity, anxiety-related behavior, and serum corticosterone were measured at baseline then bi-weekly across 8 weeks. At weeks 9-10, cardiovascular responses to a chemical vagal nerve agonist were determined to indirectly evaluate vagus nerve function. The joint structure was assessed via grading of histological sections. RESULTS: In males, OA resulted in thinner cartilage in both hypertensive (OA vs. non-OA p < 0.001) and normotensive (OA vs. non-OA p < 0.001). Only females with comorbid hypertension and OA displayed thinner cartilage (p = 0.013). Male hypertensive OA animals had increased calcified subchondral bone compared to normotensive OA animals (p = 0.043) while female hypertensive OA animals had increased calcified subchondral bone compared to hypertensive sham animals (p < 0.001). All MCLT+MMT groups developed low-grade synovitis; interestingly, hypertensive OA females had higher synovitis scores than normotensive OA females (p = 0.046). Additionally, hypertension led to larger drops in blood pressure with vagal activation in both OA (hypertensive vs. normotensive p = 0.018) and sham (hypertensive vs. normotensive p < 0.001) male animals. In females, this trend held true only in OA animals (normotensive vs. hypertensive p = 0.005). CONCLUSION: These data provide preliminary evidence that hypertension influences OA progression and encourages further study into the autonomic nervous system as a possible mechanism.

Human dermal microvascular endothelial cell morphological response to fluid shear stress.

As the cells that line the vasculature, endothelial cells are continually exposed to fluid shear stress by blood flow. Recent studies suggest that the morphological response of endothelial cells to fluid shear stress depends on the endothelial cell type. Thus, the present study characterizes the morphological response of human dermal microvascular endothelial cells (HMEC-1) and nuclei to steady, laminar, and unidirectional fluid shear stress. Cultured HMEC-1 monolayers were exposed to shear stress of 0.3 dyn/cm2, 16 dyn/cm2, or 32 dyn/cm2 for 72 h with hourly live-cell imaging capturing both the nuclear and cellular morphology. Despite changes in elongation and alignment occurring with increasing fluid shear stress, there was a lack of elongation and alignment over time under each fluid shear stress condition. Conversely, changes in cellular and nuclear area exhibited dependence on both time and fluid shear stress magnitude. The trends in cellular morphology differed at shear stress levels above and below 16 dyn/cm2, whereas the nuclear orientation was independent of fluid shear stress magnitude. These findings show the complex morphological response of HMEC-1 to fluid shear stress.

In situ fixation and subsequent collection of cultured endothelial cells in a shear flow.

In situ fixation of adherent cells is a necessary process for downstream assays. Current methods to dissociate adherent endothelial cells require the use of a cell scraper that may introduce variability in nuclear morphology. Also, a cell scraper is not an option for experiments using sealed flow chambers. HMEC-1 cells were sheared at 5 dyn/cm2 for 24 h and then fixed in situ, quenched, and dissociated at the same shear rate. Analysis revealed no statistically significant change in nuclear shape between the steps of fixation and dissociation. This method outlines an alternative for the dissociation of adherent sheared endothelial cells after being fixed in situ in a micro-scale channel without causing a change in the nuclear morphology. •This method can be used with any commercially available, or custom-made, flow chamber and flow system.•Allows for downstream experimentation with adherent cells fixed in situ, such as Hi-C analysis, without impacting nuclear morphology or chromatin organization.•Cells are cultured, fixed, and dissociated at the same shear rate. Using the same shear rate for each step yields results that are not influenced by variable forces.