Bone tissue

Abstract: The worldwide incidence of bone disorders and conditions has trended steeply upward and is expected to double by 2020, especially in populations where aging is coupled with increased obesity and poor physical activity. Engineered bone tissue has been viewed as a potential alternative to the conventional use of bone grafts, due to their limitless supply and no disease transmission. However, bone tissue engineering practices have not proceeded to clinical practice due to several limitations or challenges. Bone tissue engineering aims to induce new functional bone regeneration via the synergistic combination of biomaterials, cells, and factor therapy. In this review, we discuss the fundamentals of bone tissue engineering, highlighting the current state of this field. Further, we review the recent advances of biomaterial and cell-based research, as well as approaches used to enhance bone regeneration. Specifically, we discuss widely investigated biomaterial scaffolds, micro- and nano-structural properties of these scaffolds, and the incorporation of biomimetic properties and/or growth factors. In addition, we examine various cellular approaches, including the use of mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), adult stem cells, induced pluripotent stem cells (iPSCs), and platelet-rich plasma (PRP), and their clinical application strengths and limitations. We conclude by overviewing the challenges that face the bone tissue engineering field, such as the lack of sufficient vascularization at the defect site, and the research aimed at functional bone tissue engineering. These challenges will drive future research in the field.

Abstract: Compression tests of human and bovine trabecular bone specimens with and without marrow in situ were conducted at strain rates of from 0.001 to 10.0 per second. A porous platen above the specimens allowed the escape of marrow during testing. The presence of marrow increased the strength, modulus, and energy absorption of specimens only at the highest strain rate of 10.0 per second. This enhancement of material properties at the highest strain rate was due primarily to the restricted viscous flow of marrow through the platen rather than the flow through the pores of the trabecular bone. In specimens without marrow, the strength was proportional to the square of the apparent density and the modulus was proportional to the cube of the apparent density. Both strength and modulus were approximately proportional to the strain rate raised to the 0.06 power. These power relationships, which were shown to hold for all bone in the skeleton, allow meaningful predictions of bone tissue strength and stiffness based on in vivo density measurements.

Abstract: Bone tissue is continuously remodeled through the concerted actions of bone cells, which include bone resorption by osteoclasts and bone formation by osteoblasts, whereas osteocytes act as mechanosensors and orchestrators of the bone remodeling process. This process is under the control of local (e.g., growth factors and cytokines) and systemic (e.g., calcitonin and estrogens) factors that all together contribute for bone homeostasis. An imbalance between bone resorption and formation can result in bone diseases including osteoporosis. Recently, it has been recognized that, during bone remodeling, there are an intricate communication among bone cells. For instance, the coupling from bone resorption to bone formation is achieved by interaction between osteoclasts and osteoblasts. Moreover, osteocytes produce factors that influence osteoblast and osteoclast activities, whereas osteocyte apoptosis is followed by osteoclastic bone resorption. The increasing knowledge about the structure and functions of bone cells contributed to a better understanding of bone biology. It has been suggested that there is a complex communication between bone cells and other organs, indicating the dynamic nature of bone tissue. In this review, we discuss the current data about the structure and functions of bone cells and the factors that influence bone remodeling.

Abstract: Basic Biology Integrated Bone Tissue Physiology: Anatomy and Physiology (Jee) Cell Biology of Bone (Majeska) Molecular Biology Techniques to Measure Skeletal Gene Expression (Young and Dieudonne) Creating Transgenic Mice to Study Skeletal Function (Young and Xu) Bone Mineralization (Boskey) Techniques from Mechanics and Imaging Mechanics of Materials (Cowin) Experimental Techniques for Bone Mechanics (Turner and Burr) In Vivo Measurement of Bone Deformations Using Strain Gages (Fritton and Rubin) Imaging of Bone Structure (Ruegsegger) Mechanical and Architectural Properties of Bone Mechanical Properties of Cortical Bone and Cancellous Bone Tissue (Guo) Viscoelastic Properties of Cortical Bone (Lakes) Composite Models of Bone Properties (Lucchinetti) Dense Bone Tissue as a Molecular Composite (Lucchinetti) Quantification of Cancellous Bone Architecture (Odgaard) Elastic Constants of Cancellous Bone (von Rietbergen and Huiskes) Strength of Trabecular Bone (Keaveny) Observations of Damage in Bone (Jepsen, Davy, and Akkus) Bone Damage Mechanics (Davy and Jepsen) Ontogenic Changes in Compact Bone Material Properties (Currey) Mechanical Effects of Postmortem Changes, Preservation, and Allograft Bone Treatments (Martin and Sharkey) Flow of Fluids in Bone Blood Flow in Bone (Winet) Interstitial Fluid Flow (Knothe-Tate) Bone Poroelasticity (Cowin) Streaming Potentials in Bone (Pollack) The Intrinsic Permeability of Cancellous Bone (Arramon and Nauman) Bone Adaptation Pathophysiology of Functional Adaptation of Bone in Remodeling and Repair In Vivo (Goodship and Cunningham) Devices and Techniques for in Vitro Mechanical Stimulation of Bone Cells (Brown) Experiments on Cell Mechanosensitivity (Burger) Mechanosensory Mechanisms in Bone (Cowin and Moss) The False Premise of Wolff's Law (Cowin) Bone Modeling and Remodeling: Theories and Computation (Hart) Mechanics of Bone Regeneration (Prendergast and van der Meulen) Clinically Related Issues Applications of Bone Mechanics (Villarraga and Ford) Noninvasive Measurement of Bone Integrity (Kaufman and Siffert) Bone Prostheses and Implants (Prendergast) Design and Manufacture of Bone Replacement Scaffolds (Hollister, Chu, Halloran, and Feinberg)