Active and Passive Responses of Myofibroblasts in Response to Mechanical Stretching in 3D Culture

The stretch response of myofibroblast cells cultured in a three-dimensional environment was simultaneously measured and observed using a tissue stretching apparatus mounted to a confocal microscope. Optical measurements were used to assess mechanical estimates of cell response obtained through combined mechanical testing and biochemical inhibition. Results show that activated myofibroblasts provide an effective resistance on the order of 100s of kPa. In specific mechanical environments, stretched myofibroblasts release the ECM.

Parametric Stent Design Using pyFormex

Stenting is the most commonly used medical procedure to restore blood flow in stenotic arteries. During this endovascular intervention, a small tube-like structure is implanted in the narrowed section of the diseased artery. The vast majority of stents are crimped (i.e. plastically deformed) on a folded balloon (balloon expandable stents). After insertion through a small incision in the femoral or radial artery using a catheter, the balloon is inflated and the stent deploys. Following to the expansion, the balloon is deflated and retracted and from then on, the stent acts as a mechanical scaffold for the enlarged lumen.

Kinetic Differences in a Subject With Two Different Prosthetic Knees While Performing Sitting and Standing Movements

Advanced prostheses are currently being sold in consumer markets. The development of these advanced prostheses is largely a result of a better understanding of the biomechanics of human locomotion [1]. Powered and microprocessor controlled prostheses are offering better performance in a variety of movements and in the gait cycle. However the focus in lower limb prosthetics has been largely on locomotion (e.g. walking, stair gait and running). This study focuses on the sit and stand cycles of an individual with an Otto Bock C-leg and an Ossur Power Knee prosthesis, comparing his ability to utilize each prosthesis and comparing his cycle to that of a healthy (non-amputee) control subject. This study is part of a larger ongoing study of the sit and stand cycles seen in a large population of unilateral transfemoral prosthetic users of various kinds. The purpose of this study is to compare the difference in method of standing, and assistance provided by the prosthesis. With the knowledge gained from this study we hope to better understand the biomechanics of the sit and stand cycles, leading to better prostheses in the future.

Validation of 1D Model of the Systemic Arterial Tree Including the Cerebral Circulation

The aim of this study is to develop a distributed model of the entire systemic arterial tree, coupled to a heart model and including a detailed description of the cerebral arteries. Distributed models of the arterial tree have been studied extensively in the past (Avolio [1], Stergiopulos et al [2], Westerhof et al [3]), however, no model has been developed so far that offers a physiologically relevant coupling to the heart and includes the entire cerebral arterial tree.

Effects of External Loading on the Morphology of the Yielded Regions in Trabecular Bone Predicted by FEA

Osteoporosis is an age-related skeletal condition characterized by low bone mineral density and deterioration of the trabecular architecture leading to increased susceptibility to fracture [1]. Wolff hypothesized that trabecular architecture adapts to have its principal material axes aligned with the principal loading directions. Regions of experimentally labeled trabecular microdamage correspond to areas of high stress and strain calculated from FEA [2]. Studying the morphology of numerically predicted regions of tissue level yielding might provide insight into the role of trabecular architecture in the strength of trabecular bone.

Computational Model of Direct Injection Into the Spinal Cord Using in Vivo Diffusion Tensor Imaging

Local infusion, i.e., convection-enhanced delivery (CED), is increasingly being considered as a means to deliver therapeutic agents to nervous tissues. These infusion techniques bypass the blood-brain barrier and overcome problems associated with slow diffusion [1, 2]. Predictive models of extracellular fluid flow and transport during and following CED would be useful in treatment optimization and planning. To account for large infusion volumes, such infusion models should incorporate tissue boundaries and anisotropic tissue properties.

Growth and Remodeling of Arterial Tissue

Living tissues continuously undergo growth, i.e. a change in mass, and remodeling, i.e. reorganization or renovation. Modeling both growth and remodeling (G&R) of the vascular tissue is aimed to provide insight into the adaptation of the tissue, in the healthy and diseased state, and upon surgical intervention. An important aspect is the description of remodeling of collagen fiber direction. Whereas a phenomenological approach for that is suggested in [2], in this study we adopt an approach towards more microstructural approach, along the model in [1].

Viscoelastic Properties of Genetically Engineered Silk-Elastin-Like Protein Polymers

Genetic engineering of protein-based materials provides material scientists with high levels of control in material microstructures, properties, and functions [1]. For example, multi-block protein copolymers in which individual block may possess distinct mechanical or biological properties have been biosynthesized [2, 3]. Polypeptide sequences derived from well-studied structural proteins (e.g., collagen, silk, elastin) are often used as motifs in the design and synthesis of new protein-based material, in which new functional groups may be incorporated. In this fashion, we have produced a series of silk-elastin-like proteins (SELPs) consisting of polypeptide sequences derived from silk of superior mechanical strength and elastin that is extremely durable and resilient [2, 4]. Notably, the silk-like blocks are capable of crystallizing to form virtual cross-links between elastin-mimetic sequences, which, in turn, lower the crystallinity of the silk-like blocks and thus enhance the solubility of SELPs. Consequently, SELPs may be fabricated into useful structures for biomedical applications, including drug delivery. In this study, we will characterize viscoelastic properties of SELPs, which are particularly relevant to tissue engineering applications.

Effect of Gait on Patellofemoral Mechanics

Computational modeling of the reconstructed knee is an important tool in designing components for maximum functionality and life. Utilization of boundary conditions consistent with in vivo gait loading in such models enables predictions of knee kinematics and polyethylene damage [1–4], which can then be used to optimize component design. Several recent clinical studies have focused on complications associated with the patellofemoral joint [5–6], highlighting the need to better understand the mechanics of this compartment of total knee arthroplasty (TKA). This study utilizes a computational model to characterize the impact of gait loading on the mechanics of the patella in TKA.

The Role of Knee Extensor Strength in Balance-Restoring Step Initiation and Execution

A stepping response is often used to restore balance following a fall. Using laboratory-induced balance perturbations, various researchers have reported age-related alterations in balance recovery step characteristics including earlier step liftoff time [1; 2], shorter step length [1; 3], and longer step duration [2]. Such age-related changes in the step response may be related to older adults’ reduced strength reserve, which is prominent in the lower extremities [4] and therefore likely plays an important role in balance recovery.