Anatomy, physiology and disease
C M Langton, C F Njeh in The Physical Measurement of Bone, 2016
In addition to these growth factors, the bone matrix also contains skeletal specific proteins such as osteocalcin, and other connective tissue molecules like osteonectin and osteopontin, derived from differentiated osteoblasts [43–46]. But, by far, the major structural component of the skeletal matrix is collagen type I, a large protein composed of three separate peptide chains organized in parallel and synthesized by mature osteoblasts (see section 1.5). In fact, 90% of unmineralized osteoid is collagen type I [47, 48]. Individual subunits of the collagen helix are connected terminally to each other by cross-linking amino acids, added as a post-translational modification of the entire collagen molecule. During resorption, cross-links are catalysed initially, and are subsequently liberated from the matrix proper [43]. Some of these enter the circulation as telopeptide fragments, and are eventually filtered by the renal tubules. Both qualitative and quantitative defects in collagen synthesis, modification or mineralization can lead to chronic disorders characterized by enhanced skeletal fragility, such as osteoporosis.
Metabolic Bone Disease in Adults with Short Bowel Syndrome
John K. DiBaise, Carol Rees Parrish, Jon S. Thompson in Short Bowel Syndrome Practical Approach to Management, 2017
Bone consists of mineral in two forms, hydroxyapatite and amorphous calcium phosphate, together with type I collagen and water. In adults, normal bone is made up of compact (cortical) bone as the outer layer (80% of bone mass in adult humans) and trabecular (spongy) bone (the other 20%). The bone matrix is made up of 90% type I collagen, which is impregnated with calcium and phosphorus (hydroxyapatite) (Figure 8.1) [4]. Three main cell types are present in human bone and include osteoblasts, osteoclasts, and osteocytes. Osteoblasts, the principal bone-forming cells, are modified fibroblasts that originate from common pluripotent mesenchymal stem cells (MSCs). The differentiation of osteoblasts results in bone matrix production and bone apposition, which is also called bone formation. Osteoblasts account for 3–4% of resident bone cells and can undergo (1) apoptosis, (2) transformation into inactive osteoblasts called bone-lining cells, or (3) terminal differentiation into osteocytes. Osteocytes are star-shaped cells that account for 90–95% of all bone cells. Osteocytes play a key role in mechanotransduction [5]. Osteoclasts are multinucleated cells that are derived from pluripotent hematopoietic precursors of the macrophage lineage.
The material and structural basis of the growth-related gain and age-related loss of bone strength
Nicholas C. Harvey, Cyrus Cooper in Osteoporosis: a lifecourse epidemiology approach to skeletal health, 2018
During growth, an increasing volume of bone matrix is assembled with varying medullary and cortical canal void volumes establishing bone’s external dimension and differing configuration of its matrix forming the compact bone (the least porous compartment), the transitional compartment and the most porous trabecular compartment. Bone size is achieved using relatively more void than matrix volume, so larger bones are assembled with relatively less material; larger bones have a lower volumetric apparent bone mineral density (BMD). Smaller bones are more robustly assembled. Asians have long bones with thicker cortices relative to their cross-sectional size, less porous cortices with a higher matrix mineral density than Caucasians. Sex and racial differences in bone dimensions and microstructure become most evident at puberty, partly due to differences in pubertal age. Later puberty in males than females, or Caucasians than Asians, results in greater appendicular dimensions in males than females and Caucasians than Asians because the longer prepubertal years of the more rapid appendicular than axial growth. Longer intrapubertal growth confers greater axial length in males than females but comparable axial length in Caucasians and Asians.
Isoflavones improve collagen I and glycosaminoglycans and prevent bone loss in type 1 diabetic rats
Published in Climacteric, 2020
A. A. F. Carbonel, M. C. Vieira, R. S. Simões, P. D. A. Lima, L. F. P. Fuchs, E. R. C. Girão, G. P. Cicivizzo, G. R. S. Sasso, L. O. Carvalho de Moraes, J. M. Soares Junior, E. C. Baracat, M. J. Simões, M. J. B. C. Girão
In mammals, collagen is the most abundant protein, constituting more than a third of the protein weight of the body42. About 28 types of collagen were found in vertebrates and four types of collagen were found in the bone, including CollI and collagen types III, V, and XXIV. CollI is the most prevalent in the extracellular matrix, especially in tissues such as the bone and tendons43–45. The extracellular matrix plays an important role in morphogenesis and cellular metabolism of new tissues, granting mechanical and biochemical properties43. Thus, we understand that bone is composed of the bone matrix, cells, and bioactive factors, and the bone matrix is a combination of inorganic minerals and organic polymers. The CollI fibril, composed of five chains of triple-helix collagen, is the main organic polymer of the bone matrix, playing an important role in the process of bone formation and remodeling46,47.
Ficus deltoidea promotes bone formation in streptozotocin-induced diabetic rats
Published in Pharmaceutical Biology, 2021
Nurdiana Samsulrizal, Yong-Meng Goh, Hafandi Ahmad, Sulaiman Md Dom, Nur Syimal’ain Azmi, Noor Syaffinaz NoorMohamad Zin, Mahdi Ebrahimi
The histological section of normal rat femur showed a network of bone trabeculae at the distal femoral metaphysis which separated by bone marrow spaces (Figure 2(A1)). It was also found that osteocytes were surrounded by their lacunae in the bone matrix. As depicted in Figure 2(C1), a normal healthy articular cartilage was observed on the distal femur of NC rats in which the calcified cartilage layer is flanked by an undulating tidemark. Conversely, the DC rats displayed a sparse and thinner trabecular structure of the cancellous bone (Figure 2(A2)) along with a paucity of cells in the proliferative zone (Figure 2(B2)). The thickness of the cortical layer and articular cartilage was phenotypically decreased in the DC rats. Strikingly, it was observed that the bone trabeculae were more orderly arranged and bone matrix density increased (Figure 2(B4)) in the DFD rats. Figure 2(D4) also showed that less cortical erosion was found following F. deltoidea treatment. However, the DFD rats were associated with thicker calcified cartilage with chondrocyte hypertrophy.
Bioavailability of Calcium from Chia (Salvia hispanica L.) in Ovariectomized Rats Fed a High Fat Diet
Published in Journal of the American College of Nutrition, 2021
Marcella Duarte Villas Mishima, Bárbara Pereira da Silva, Renata Celi Lopes Toledo, Neuza Maria Brunoro Costa, Hércia Stampini Duarte Martino
With aging and post-menopause, the efficiency of calcium absorption is decreased. Low estrogen levels are known to induce bone remodeling and skeletal frailty, determinants of osteoporosis pathogenesis (1–3). Skeletal abnormalities such as bone loss occur when there is an imbalance in bone matrix synthesis and bone resorption, controlled by osteoblasts and osteoclasts, respectively. This imbalance is also caused by hormonal changes and inflammation (4). In this sense, bone resorption is affected by low estrogen in the postmenopausal period and inflammation induced by obesity. Consumption of a high fat diet increases inflammation (5), adipocyte hypertrophy stimulates the secretion of proinflammatory cytokines. In turn, these cytokines stimulate the differentiation of osteoclasts and bone resorption (6, 7). Recommendation of calcium intake is based on bone health since calcium is one of the main strategies to ensure bone construction and maintenance (8), thus its adequate intake is important (9).
Related Knowledge Centers
- Bone
- Cytoplasm
- Haversian Canal
- Lacuna
- Osteocyte
- Osteology
- Metabolism
- Osteoblast
- Bone Canaliculus
- Nutrient