Plxnd1-mediated mechanosensing of blood flow controls the caliber of the Dorsal Aorta via the transcription factor Klf2

The cardiovascular system generates and responds to mechanical forces. The heartbeat pumps blood through a network of vascular tubes, which adjust their caliber in response to the hemodynamic environment. However, how endothelial cells in the developing vascular system integrate inputs from circulatory forces into signaling pathways to define vessel caliber is poorly understood. Using vertebrate embryos and in vitro-assembled microvascular networks of human endothelial cells as models, flow and genetic manipulations, and custom software, we reveal that Plexin-D1, an endothelial Semaphorin receptor critical for angiogenic guidance, employs its mechanosensing activity to serve as a crucial positive regulator of the Dorsal Aorta's (DA) caliber. We also uncover that the flow-responsive transcription factor KLF2 acts as a paramount mechanosensitive effector of Plexin-D1 that enlarges endothelial cells to widen the vessel. These findings illuminate the molecular and cellular mechanisms orchestrating the interplay between cardiovascular development and hemodynamic forces.

Repeatability and Comparability of Retinal Blood Vessel Caliber Measurements by OCTA

BACKGROUND

To investigate the repeatability in vessel caliber measurements by optical coherence tomography angiography (OCTA).

METHODS

In this prospective study, 28 patients (47 eyes) underwent sequential OCTA imaging of the optic nerve head and macula. Two independent masked graders measured vessel caliber for sequential images of the optic nerve head and macula. The average vessel width was determined and variability between graders and images.

RESULTS

A total of 8400 measurements of 420 vessels from 84 OCTA images were included in the analysis. Overall, inter-grader agreement was excellent (ICC 0.90). The coefficient of variation (CoV) for all repeated OCTA images was 0.10. Greater glaucoma severity, older age, macular location, and diagnosis of diabetes were associated with thinner vessels (p < 0.05). CoV was higher in the peripapillary region (0.07) as compared to the macula (0.15). ICC was high for all subgroups except for the macula (ICC = 0.72).

CONCLUSIONS

Overall, the repeatability of vessel caliber measurements by OCTA was high and variability low. There was greater variability in the measurement of macular vessels, possibly due to technical limitations in acquiring accurate vessel widths for smaller macular vessels.

Investigating the Role of PPARβ/δ in Retinal Vascular Remodeling Using Pparβ/δ-Deficient Mice

Peroxisome proliferator-activated receptor (PPAR)β/δ is a member of the nuclear receptor superfamily of transcription factors, which plays fundamental roles in cell proliferation and differentiation, inflammation, adipogenesis, and energy homeostasis. Previous studies demonstrated a reduced choroidal neovascularization (CNV) in Pparβ/δ-deficient mice. However, PPARβ/δ's role in physiological blood vessel formation and vessel remodeling in the retina has yet to be established. Our study showed that PPARβ/δ is specifically required for disordered blood vessel formation in the retina. We further demonstrated an increased arteriovenous crossover and wider venous caliber in Pparβ/δ-haplodeficient mice. In summary, these results indicated a critical role of PPARβ/δ in pathological angiogenesis and blood vessel remodeling in the retina.

Recipient Vessel Selection in Head and Neck Reconstruction

Objective: Recipient vessel caliber may be the single most important variable for flow to free tissue transfer. We performed cadaveric dissection of the external carotid artery and its branches to analyze average diameter in order to determine an algorithm for recipient vessel selection in head and neck reconstruction. Methods: The external carotid artery and branches were exposed on 3 lightly embalmed male human cadavers, aged 82 to 85 years. Each vessel was dissected, and luminal diameters were recorded with calipers. Results: The proximal ECA had the greatest average diameter (4 ± 0.6 mm) and potential flow; followed by distal ECA (2.85 ± 0.4 mm) facial (2.0 ± 0.6 mm), lingual (1.65 ± 0.6 mm), superior thyroid (1 ± 0.3  mm), and superficial temporal (0.85 ± 0.4 mm). There was a trend towards size variation between sides of the same cadaver. Conclusion: The external carotid artery has the greatest internal diameter and potential blood flow. It should be considered, when feasible, especially for defects of the upper third of the head. For defects of the lower third, the facial artery and the lingual artery should be utilized before the smaller diameter superior thyroid artery. Vessel selection is more challenging in the setting of radiation therapy, complex trauma, and prior neck surgery. In these settings, it is useful to have knowledge of the vascular anatomy and an objective algorithm for recipient vessel selection.

The effects of ranibizumab injections on fluorescein angiographic findings and visual acuity recovery in age-related macular degeneration

Aim

The objective of the study reported here was to evaluate the effect of ranibizumab on retinal circulation times and vessel caliber and to analyze the correlation of these factors with visual acuity (VA) prognosis in patients with age-related macular degeneration (AMD).

Subjects and methods

This prospective cohort study included 52 eyes of 46 patients (mean age 73.5 years [standard deviation 7.7]; 28 males, 18 females). The study parameters were best-corrected visual acuity (BCVA), central macular thickness (CMT) (pre- and posttreatment: for 3 months after the last injection), retinal circulation times, diameter of retinal arteriole (DRA), and diameter of retinal vein (DRV) (pre- and posttreatment: after a loading dose of three consecutive injections of ranibizumab with a 4-week interval in the initial phase). The pretreatment, posttreatment measurements, and their differences were recorded for analyses. The injections were repeated when needed. Eyes were grouped into one of two groups according to VA recovery: Group 1, cases showing significant recovery of VA (n=21, 37%), and Group 2, cases showing preservation of VA (n=22, 42%) and deterioration of VA (n=11, 21%). Differences were compared statistically in and between groups. Logistic regression analysis was undertaken to determine the correlation of these parameters with VA recovery.

Results

There was a significant reduction in DRA (P=0.007) and CMT levels (P<0.001) in both study groups after treatment. When the two groups were compared, the differences in pretreatment values of DRA (P=0.001), DRV (P=0.017), CMT (P=0.039), and mean BCVA (P=0.00) were found to be statistically significant. Posttreatment changes in DRA (P=0.013) and mean CMT (P=0.010) were found to be factors related to VA recovery by logistic regression analysis.

Conclusion

Our findings reveal that ranibizumab treatment is associated with decrease in DRA, CMT, and significant improvement in VA recovery. Further, taking into account the cases in which VA was preserved, when needed, ranibizumab should be re-injected after the loading dose.