The structural integrity of the cervix in pregnancy is necessary for carrying a pregnancy until term, and the organization of human cervical tissue collagen likely plays an important role in the tissue’s structural function. Collagen fibers in the cervical extracellular matrix exhibit preferential directionality, and this collagen network ultrastructure is hypothesized to reorient and remodel during cervical softening and dilation at time of parturition. Within the cervix, the upper half is substantially loaded during pregnancy and is where the premature funneling starts to happen. To characterize the cervical collagen ultrastructure for the upper half of the human cervix, we imaged whole axial tissue slices from non-pregnant and pregnant women undergoing hysterectomy or cesarean hysterectomy respectively using optical coherence tomography (OCT) and implemented a pixel-wise fiber orientation tracking method to measure the distribution of fiber orientation. The collagen fiber orientation maps show that there are two radial zones and the preferential fiber direction is circumferential in a dominant outer radial zone. The OCT data also reveal that there are two anatomic regions with distinct fiber orientation and dispersion properties. These regions are labeled: Region 1—the posterior and anterior quadrants in the outer radial zone and Region 2—the left and right quadrants in the outer radial zone and all quadrants in the inner radial zone. When comparing samples from nulliparous vs multiparous women, no differences in these fiber properties were noted. Pregnant tissue samples exhibit an overall higher fiber dispersion and more heterogeneous fiber properties within the sample than non-pregnant tissue. Collectively, these OCT data suggest that collagen fiber dispersion and directionality may play a role in cervical remodeling during pregnancy, where distinct remodeling properties exist according to anatomical quadrant.

During pregnancy, the uterine cervix is the mechanical barrier that prevents delivery of a fetus. The underlying cervical collagen ultrastructure, which influences the overall mechanical properties of the cervix, plays a role in maintaining a successful pregnancy until term. Yet, not much is known about this collagen ultrastructure in pregnant and nonpregnant human tissue. We used optical coherence tomography to investigate the directionality and dispersion of collagen fiber bundles in the human cervix. An image analysis tool has been developed, combining a stitching method with a fiber orientation measurement, to study axially sliced cervix samples. This tool was used to analyze the ultrastructure of ex-vivo pregnant and non-pregnant hysterectomy tissue samples taken at the internal os, which is the region of the cervix adjacent to the uterus. With this tool, directionality maps of collagen fiber bundles and dispersion of collagen fiber orientation were analyzed. It was found that that the overall preferred directionality of the collagen fibers for both the nonpregnant and pregnant samples were circling around the inner cervical canal. Pregnant samples showed greater dispersion than non-pregnant samples. Lastly, we observed regional differences in collagen fiber dispersion. Fibers closer to the inner canal showed more dispersion than the fibers on the radial edges.

A supercontinuum source based on a 1-mm ² Si ₃ N ₄ chip offers improved OCT imaging performance over commercial supercontinuum sources.

Cardiac diseases are among the leading causes of morbidity and mortality globally. During the progression of heart disease, microstructural heterogeneity within myocardial tissue could lead to an increased risk of life-threatening cardiac diseases such as ventricular arrhythmias and heart failure.^1,2 Visualization of the features in the endomyocardial layer may shed light on the correlations between the microstructural and functional changes in the tissue, which are important for guiding diagnostic procedures and clinical treatment such as reverse remodeling therapy,³ radiofrequency ablation,⁴ and endomyocardial biopsy (EMB).^5,6 Particularly, despite the controversy of EMB, it is still the most frequently used method for surveillance of cardiac allograft rejection and for the diagnosis of unexplained ventricular dysfunction.⁶ The main reason is that most of the well-established medical imaging modalities (magnetic resonance imaging,⁷ echocardiography,⁸ and computed tomography⁹) do not have sufficient resolution to provide the cellular-level assessment of the myocardium that the biopsy can otherwise provide.⁵ Optical coherence tomography (OCT) is a high-speed, nondestructive imaging tool that is able to produce cross-sectional and three-dimensional (3-D) images with cellular/subcellular axial resolution within millimeter-scale penetration depth of biological samples and has been applied in a wide range of medical imaging applications.^10,11

Cardiovascular disease (CVD) is the leading cause of mortality and morbidity in the United States.¹ An important factor in the pathophysiology of CVD is the composition and remodeling of the myocardium. Myocardial tissue includes muscle, adipose tissue, collagen fibers, and fibrotic myocardium, and the relative percentage of each varies by chamber and with the progression of the disease. Myofiber disarray can impair electrical conduction and result in arrhythmias or hypertrophic cardiomyopathy.² The presence of adipose within the myocardium provides a high indication of arrhythmogenic cardiomyopathy³ and thickened layers of collagen fibers imply severe myocardial scar.⁴ The diffusion of myocardial fibrosis, a fundamental process in the remodeling of cardiomyopathy, is postulated to cause increased cardiac stiffness and poor clinical outcomes.⁵ Due to the importance of myocardial tissue composition on normal heart function and CVD, characterization of myocardial tissue can facilitate the evaluation of tissue remodeling, identification of arrhythmogenic substrates, and diagnosis of CVD.