Generating Virtual Bone Scans for the Purpose of Investigating the Effects of Cortical Microstructure.

Evaluating the contribution of microstructure to overall bone strength is tricky since it is difficult to control changes to pore structure in human or animal samples. We developed an open-source program that can generate three-dimensional models of micron-scale cortical bone. These models can be highly customized with a wide array of variable input parameters to allow for generation of samples with high similarity to CT scans of cortical bone or with specific geometric features.

Building Entrepreneurial Mindset: Motivating Curiosity, Connections, and Creating Value in an Assistive-Device Design Project.

Developing entrepreneurial mindset (EM) can help students understand the bigger picture, recognize opportunities, and learn from mistakes to create value. The purpose of this work was to promote EM development in a required junior-level mechanical engineering course. A pre-existing assistive device project was adapted to incorporate entrepreneurial-minded learning activities requiring students to demonstrate curiosity, make connections, and create value.

Mineral deposition and vascular invasion of hydroxyapatite reinforced collagen scaffolds seeded with human adipose-derived stem cells.

Background: Collagen-based scaffolds reinforced with hydroxyapatite (HA) are an attractive choice for bone tissue engineering because their composition mimics that of bone. We previously reported the development of compression-molded collagen-HA scaffolds that exhibited high porosity, interconnected pores, and mechanical properties that were well-suited for surgical handling and fixation. The objective of this study was to investigate these novel collagen-HA scaffolds in combination with human adipose-derived stem cells (hASCs) as a template for bone formation in a subcutaneous athymic mouse model.

Hydroxyapatite reinforced collagen scaffolds with improved architecture and mechanical properties.

Hydroxyapatite (HA) reinforced collagen scaffolds have shown promise for synthetic bone graft substitutes and tissue engineering scaffolds. Freeze-dried HA-collagen scaffolds are readily fabricated and have exhibited osteogenicity in vivo, but are limited by an inherent scaffold architecture that results in a relatively small pore size and weak mechanical properties. In order to overcome these limitations, HA-collagen scaffolds were prepared by compression molding HA reinforcements and paraffin microspheres within a suspension of concentrated collagen fibrils (∼ 180 mg/mL), cross-linking the collagen matrix, and leaching the paraffin porogen.

A probabilistic damage model based on direct 3-D correlation of strain to damage formation following fatigue loading of rat femora.

Microdamage accumulates in bone due to repetitive or excessive mechanical loading, and accumulation of damage can lead to an increase in fracture susceptibility. Understanding the stress or strain criterion for damage formation would allow improved predictive modeling to better assess experimental results or evaluate training regimens. Finite element models coupled with three-dimensional measurements of damage were used to directly correlate damage formation to the local strain state in whole rat femora subjected to three-point bending fatigue.

Shear strength and toughness of trabecular bone are more sensitive to density than damage.

Microdamage occurs in trabecular bone under normal loading, which impairs the mechanical properties. Architectural degradation associated with osteoporosis increases damage susceptibility, resulting in a cumulative negative effect on the mechanical properties. Treatments for osteoporosis could be targeted toward increased bone mineral density, improved architecture, or repair and prevention of microdamage.

Detection of fatigue microdamage in whole rat femora using contrast-enhanced micro-computed tomography.

Microdamage in bone tissue is typically studied using destructive, two-dimensional histological techniques. Contrast-enhanced micro-computed tomography (micro-CT) was recently demonstrated to enable non-destructive, three-dimensional (3-D) detection of microdamage in machined cortical and trabecular bone specimens in vitro. However, the accumulation of microdamage in whole bones is influenced by variations in the magnitude and mode of loading due to the complex whole bone morphology.

The sequential production profiles of growth factors and their relations to bone volume in ossifying bone marrow explants.

Osteogenesis is a complex process that involves the synergistic contribution of multiple cell types and numerous growth factors (GFs). To develop effective bone tissue engineering strategies employing GFs, it is essential to delineate the complex and interconnected role of GFs in osteogenesis. The studies investigating the temporal involvement of GFs in osteogenesis are limited to in vitro studies with single cell types or complex in vivo studies.