Nanoscale Imaging and Analysis of Bone Pathologies

Understanding the properties of bone is of both fundamental and clinical relevance. The basis of bone’s quality and mechanical resilience lies in its nanoscale building blocks (i.e., mineral, collagen, non-collagenous proteins, and water) and their complex interactions across length scales. Although the structure–mechanical property relationship in healthy bone tissue is relatively well characterized, not much is known about the molecular-level origin of impaired mechanics and higher fracture risks in skeletal disorders such as osteoporosis or Paget’s disease. Alterations in the ultrastructure, chemistry, and nano-/micromechanics of bone tissue in such a diverse group of diseased states have only been briefly explored. Recent research is uncovering the effects of several non-collagenous bone matrix proteins, whose deficiencies or mutations are, to some extent, implicated in bone diseases, on bone matrix quality and mechanics. Herein, we review existing studies on ultrastructural imaging—with a focus on electron microscopy—and chemical, mechanical analysis of pathological bone tissues. The nanometric details offered by these reports, from studying knockout mice models to characterizing exact disease phenotypes, can provide key insights into various bone pathologies and facilitate the development of new treatments.

Exceptionally preserved extracellular bone matrix proteins from the late Neogene proboscidean Anancus (Mammalia: Proboscidea)

In an exceptional preservation state, bones conserve the entire pattern of extracellular bone matrix proteins over thousands or sometimes even millions of years. Here we present typical extracellular bone matrix proteins, which were extracted from a 3.0-million-year-old gomphothere proboscidean, and identified with special antibodies. For the first time, osteonectin, osteopontin and BMP-2 were confidently identified from the extinct Anancus arvernensis, based on late Pliocene material from Willershausen, Lower Saxony, Germany. Our study has value in demonstrating that the longevity of original extracellular bone matrix proteins is much greater than formerly expected, and that such materials may be stabilised for distinct geological periods of time, especially in Fossil Lagerstätten.

The Cell Origin and Role of Osteoclastogenesis and Osteoblastogenesis in Vascular Calcification

Arterial calcification refers to the abnormal deposition of calcium salts in the arterial wall, which results in vessel lumen stenosis and vascular remodeling. Studies increasingly show that arterial calcification is a cell mediated, reversible and active regulated process similar to physiological bone mineralization. The osteoblasts and chondrocytes-like cells are present in large numbers in the calcified lesions, and express osteogenic transcription factor and bone matrix proteins that are known to initiate and promote arterial calcification. In addition, osteoclast-like cells have also been detected in calcified arterial walls wherein they possibly inhibit vascular calcification, similar to the catabolic process of bone mineral resorption. Therefore, tilting the balance between osteoblast-like and osteoclast-like cells to the latter maybe a promising therapeutic strategy against vascular calcification. In this review, we have summarized the current findings on the origin and functions of osteoblast-like and osteoclast-like cells in the development and progression of vascular progression, and explored novel therapeutic possibilities.

Prospective Aspects of Regeneration in Orthopaedics: A Review

Musculoskeletal diseases affect millions of people worldwide and are one of the leading causes of long-term pain and physical disability. Traditional treatment methods for promoting healing and repair has always been consider gold standard, But the emergence of new therapeutic approaches aims to regenerate or repair musculoskeletal tissue. The recognition of a regenerative therapy in orthopaedics requires the demonstration of new Bone, Cartilage, ligament, tendons, healing of soft tissues injuries and Overuse conditions like plantar fasciitis or tennis elbow . Regenerative therapy boosts the body’s ability to use its repair systems to heal diseased or damaged cells after a severe injury, or other degenerative condition. A diversity of regenerative strategies have been evaluated, including distraction osteogenesis, bone grafts and bone substitute materials, bone matrix proteins, growth/differentiation factors, combined therapies and, more recently, tissue‐engineering approaches. This review aims to evaluate the current status of the therapies available and to discuss the challenges that must be faced in order to achieve predictable orthopaedic regeneration in clinical practice.

Evidence of Osteogenic Regulation in Calcific Porcine Aortic Valves

Background: Chemically cross-linked animal tissues, such as porcine aortic valves (PAVs) have many documented advantages over mechanical valves. However, calcification is the major underlying pathologic process that results in bioprosthetic valve failure. Recently, several reports described the expression of noncollagenous bone matrix proteins in bioprosthetic valves and suggested an actively regulated process of tissue repair. Methods: Thirty-one explanted PAVs with evidence of calcification were collected and examined for the protein expression implicated in myofibroblast activation, osteoblast differentiation, and bone matrix deposition by using immunohistochemistry. Results: The mean duration that PAVs were implanted was 11.5 ± 5.6 years, ranging from 12 months to 28 years. Pearson correlation analysis showed a significant relationship between the duration and valvular calcification (r = 0.3818, P = .034). The number of vimentin-positive mesenchymal cells in explanted PAVs was significantly lower than that of unused PAVs (P < .01). However, increased expression of α-smooth muscle actin (α-SMA) (P < .01), proliferating cell nuclear antigen (PCNA, P < .01), Cbfa1/Runx2 (P < .01), osterix (P = .0126), bone sialoprotein (BSP, P < .01), osteocalcin (P < .01), and osteopontin (P < .01) was found in explanted PAVs. Immunohistochemical staining of alkaline phosphatase (ALP) and osteocalcin was negative in the unused PAVs. In explanted PAVs, the expression level of these 2 proteins was also significantly increased. Conclusions: Our results support the view that PAV calcification is an actively regulated process with osteogenic signaling activation.

Expression of Non-collagenous Bone Matrix Proteins in Osteoblasts Stimulated by Mechanical Stretching in the Cranial Suture of Neonatal Mice

We investigated the influence of mechanical stretching on the genetic expression pattern of non-collagenous bone matrix proteins in osteoblasts. The cranial sutures of neonatal mice were subjected to ex vivo mechanical stretching. In the non-stretched control group, as osteoblast differentiation progressed, the successive genetic expression of bone sialoprotein (BSP), osteopontin (OPN), and osteocalcin (OCN) was detected using in situ hybridization, in that order. In the stretched group, the sutures were widened, and after 24 hr of cultivation, a large number of osteoblasts and abundant new osteoid were observed on the borders of the parietal bones. All new osteoblasts expressed BSP and some of them expressed OPN, but very few of them expressed OCN. After 48 hr, more extensive presence of osteoid was noted on the borders of the parietal bones, and this osteoid was partially mineralized; all osteoblasts on the osteoid surface expressed BSP, and more osteoblasts expressed OPN than those after 24 hr cultivation. Surprisingly, many of the osteoblasts that did not express OPN, expressed OCN. This suggests that when osteoblast differentiation is stimulated by mechanical stress, the genetic expression pattern of non-collagenous proteins in the newly differentiated osteoblasts is affected.