Marfan syndrome is an inherited connective tissue disorder that affects the cardiovascular, musculoskeletal, and ocular systems. It is caused by pathogenic variants in the fibrillin-1 gene (FBN1). Fibrillin is a primary component of microfibrils, which are found throughout the extracellular matrix (ECM) and provide elasticity and resilience to connective tissue. Microfibrils also play a role in signaling by sequestering growth factors and interacting with cell surface receptors. In many tissues, microfibrils are interwoven with elastin, collagens, and other elements of the ECM. However, uniquely in the ciliary zonule of the eye, microfibrils exist in cell-free bundles largely devoid of other components. This structure offers a rare opportunity to study a pure population of fibrillin microfibrils in a relatively native state. Here, we briefly review the organization of the zonule and describe recent experiments in which we measure zonular biomechanics, providing insights into microfibril dynamics that would be challenging to obtain in other contexts.

Background/Objectives: Exsanguination is a leading cause of preventable death in military and civilian settings due to extensive blood loss and hemorrhagic shock, which trigger systemic effects such as impaired tissue perfusion, hypoxia, inflammation, and multi-organ dysfunction. Standard resuscitation restores blood volume but fails to address critical aspects of hemorrhagic shock, including inflammation, coagulopathy, and reperfusion injury. To address these limitations, novel phospholipid nanoparticle (PNP)-based resuscitative fluids, VBI-S and VBI-1, were developed to modulate nitric oxide (NO) levels, improving hemodynamic stability, tissue oxygenation, and reducing inflammatory injury. This study assessed the potential of novel phospholipid nanoparticle fluids, VBI-S and VBI-1, as resuscitative agents for severe hemorrhagic shock by evaluating their ability to regulate nitric oxide, restore blood pressure, and mitigate ischemia–reperfusion injury. Methods: This study involved two phases with Sprague Dawley rats (n = 6 per group). Phase one, lasting 4 h, included four groups: blood, Ringer’s lactate, VBI-S, and VBI-1. Phase two, lasting 12 h, comprised sham, blood, and VBI-1 groups. Under anesthesia, one femoral artery was catheterized for blood pressure monitoring, and blood withdrawal from the other induced apnea. Reanimation was performed using an intra-arterial infusion of shed blood, Ringer’s lactate, VBI-S, or VBI-1. Tissue samples were analyzed histologically and for oxidative DNA damage via immunofluorescence. Chemiluminescence and rheology assessed nitric oxide interactions and viscosity. Data were analyzed using ANOVA. Results: VBI-1 and shed blood increased mean arterial pressure (MAP) from <10 mmHg to survivable levels sustained for 12 h, with VBI-1 showing significantly higher MAP at 3–4 h. Rats treated with Ringer’s lactate died within 30 min. Histology revealed reduced organ damage in VBI-1-treated rats compared to shed blood. Immunohistochemistry indicated significantly less oxidative DNA damage (p < 0.001) in VBI-1-treated rats. VBI-1 exhibited superior viscosity and nitric oxide binding. Conclusions: VBI-1 demonstrates strong potential as a resuscitative fluid, offering blood pressure restoration, reduced oxidative damage, and enhanced tissue perfusion, with significant implications for use in resource-limited and pre-hospital settings.

Elasticity is essential to the function of tissues such as blood vessels, muscles, and lungs. This property is derived mostly from the extracellular matrix (ECM), the protein meshwork that binds cells and tissues together. How the elastic properties of an ECM network relate to its composition, and whether the relaxation properties of the ECM play a physiological role, are questions that have yet to be fully addressed. Part of the challenge lies in the complex architecture of most ECM systems and the difficulty in isolating ECM components without compromising their structure. One exception is the zonule, an ECM system found in the eye of vertebrates. The zonule comprises fibers hundreds to thousands of micrometers in length that span the cell-free space between the lens and the eyewall. In this report, we describe a mechanical technique that takes advantage of the highly organized structure of the zonule to quantify its viscoelastic properties and to determine the contribution of individual protein components. The method involves dissection of a fixed eye to expose the lens and the zonule and employs a pull-up technique that stretches the zonular fibers equally while their tension is monitored. The technique is relatively inexpensive yet sensitive enough to detect alterations in viscoelastic properties of zonular fibers in mice lacking specific zonular proteins or with aging. Although the method presented here is designed primarily for studying ocular development and disease, it could also serve as an experimental model for exploring broader questions regarding the viscoelastic properties of elastic ECM's and the role of external factors such as ionic concentration, temperature, and interactions with signaling molecules.

Zonular fibers are essential for suspending the lens within the eye and, in primates, for transmitting forces generated by the ciliary body to drive ocular accommodation. Despite their biomechanical importance, the response of these fibers to sudden strains, and the molecular basis of their exceptional durability remain poorly understood. This is due, in part, to the absence of tools for studying them in isolation. Here, we present a custom-built, cost-effective apparatus designed to isolate, manipulate, and characterize individual zonular fibers under controlled physical and chemical conditions. The apparatus enables quantification of elastic moduli, stress-relaxation behavior, Poisson's ratio, and response to chemical or enzymatic treatments all from a single fiber, while supporting simultaneous imaging and post-experiment analyses by atomic force microscopy (AFM) or other modalities. We describe the design and calibration of the system, provide protocols for sample mounting and mechanical testing, and introduce accessories for high-resolution imaging and temperature control. Using bovine zonular fibers as a model, we demonstrate the system's ability to capture dynamic responses to enzymatic digestion, including time-resolved degradation kinetics following exposure to α-amylase and trypsin. The modular design, precision, and affordability of the apparatus make it a valuable platform for investigating the mechanics of fine elastic fibers in the eye and beyond, with relevance to connective tissue biology across organ systems.