CARTILAGE AND BONE Department of Histology and Embryology, Faculty of Medicine MU pvanhara@med.muni.cz Petr Vaňhara, PhD ▪ CARTILAGE ▪ Cartilage General features: ▪ specialized connective tissue with continuous ECM ▪ flexible, mechanically resistant ▪ avascular, non-innervated ▪ support of soft tissues - trachea, larynx ▪ skeletal support - costal cartilages ▪ diarthrosis - joints ▪ bone growth 1. cells 2. fibrils 3. amorphous ground substance ▪ Composition and structure ▪ Perichondrium – connective tissue around cartilage (except joints) ▪ Extracellular matrix – water, proteoglycans and collagen II fibrils ▪ Cells of cartilage - chondroblasts, chondrocytes Solid consistence Pressure elasticity Growth ECM production Nutrition Growth ▪ Distribution Hyaline Elastic Fibrous http://chickscope.beckman.uiuc.edu/explore/embryology/day14/dev2.html ▪ Distribution Hyaline Alcian Blue&Alizarin Red - most abundant - temporary embryonal/fetal skeleton - epiphyseal growth plate - articulation (joints) respiratory passages ▪ Cells of cartilage • mesenchymal origin • typical ultrastructure of proteosynthetically active cells • production of extracellular matrix • interstitial proliferation • isogenetic groups, lacunae ▪ Chondroblasts and chondrocytes ▪ Origin of chondrocytes Runx2 Osx Sox9 Runx2 C/EBP PPAR Collagen 2A aggrecan ▪ Origin of chondrocytes ▪ Ultrastructure of chondrocytes • oval → round cells • rich in organelles, especially rER and GA • glycogen granules (anaerobic metabolism) • occasionally lipid droplets ▪ Ultrastructure of chondrocytes ▪ Ultrastructure of chondrocytes ▪ Extracellular matrix biomechanical properties 1. glycosaminoglycans 2. proteoglycans 3. fibers 4. water Glycosaminoglycans linear unbranched polysaccharides containing a repeating disaccharide unit: 1. N-acetylgalactosamine (GalNAc) or N-acetylglucosamine (GlcNAc) 2. uronic acid (glucuronate (GlcA)) or iduronate. hyaluronic acid Glycosaminoglycan Localization Hyaluronic acid Umbilical cord, synovial fluid, fluid of corpus vitreum, cartilage Chondroitinsulphate Cartilage, bone, cornea, skin, notochord, aorta Dermatansulphate Skin, ligaments, adventitia of aorta Heparansulphate Aorta, lungs, liver, basal membranes Keratansulphate Iris, cartilage, nucleus pulposus, anulus fibrosus Proteoglycans — protein + dominant linear saccharide component — proteoglycan aggregates — water-binding, volume dependent of hydratation — aggrecan (cartilage) — syndekan — fibroglykan • pericellular • territorial • interterritorial ▪ Architecture of extracellular matrix transduction of biochemical and biomechanical signals • collagen fibrils - col II + col IX/XI - thin fibrils (15-20 nm → no striation) do not form fibers - interconnected with perichondrium • proteoglycans and glycosaminoglycans - aggrecan hyaluronan-based aggregates • water - 80% ▪ Extracellular matrix • pressure elasticity - proteoglycans – polyanionic (COO-, SO4 II-) - expansion prevented by collagen fibrils - repulsion forces ▪ Architecture of extracellular matrix • biphasic model of cartilage conditioned by ECM composition - proteoglycans, collagen, cells, and lipids constitute the solid phase of the mixture - interstitial fluid that is free to move through the matrix fluid phase) - under impact loads, fluid flows through the framework, until the cartilage start to behave as a single-phase, incompressible, elastic solid - the fluid does not flow - after load release, fluid returns - nutritive aspect I. tangential (superficial) zone II. transitional zone III. radial (deep) zone tide mark I. mineralized cartilage zone subchondral bone ▪ Architecture of extracellular matrix • synovial cartilage ▪ Perichondrium ▪ stratum fibrosum - biomechanics ▪ stratum chondrogenicum - growth Exchange of metabolites Apositional growth Interstitial proliferation ▪ Synovium ▪ membrana fibrosa - dense collagen c.t. ▪ membrana synovialis ▪ intima, subintima - folds extending to the joint cavity - numerous blood and lymphatic vessels, nerves - discontinuous cell layers (synovialocytes) - basal membrane and intercellular junctions absent - not an epithelium but mesenchymal (c.t.) origin - synovial fluid rich in hyaluronans - bursae synoviales, vaginae tendineum http://www2.indstate.edu/thcme/mmmoga/histology/slide35.html ▪ Elastic cartilage - acidophilic elastic fibers in matrix - no isogenetic groups - auricula, meatus, larynx, epiglottis ▪ Elastic fibers • less abundant than collagen • polymer – tropoelastin • minimal tensile resistance, loss of elasticity if overstretched • reduction of hysteresis = allow return back to original state after mechanic change ▪ Elastic cartilage ▪ Fibrocartilage • fibrous compound dominant – collagen I and II – mechanical durability • minimum of amorphous matrixfibers visible • intervertebral discs, symphysis pubis, articular discs, meniscus ▪ BONE ▪ Histological classification of bone tissue • Primary (woven, fibrous) - Temporary, growth and regeneration of bones, collagen fibrils woven - Replaced by secondary bone - Remains only in some parts of body - sutures of skull, tuberositas ossium, tooth cement • Secondary (lamellar) - Lamellae – collagen fibers in concentric layers (3-7m) around a canal with capillaries = Haversian system (osteon) - Spongy (trabecular) - Trabeculae, similar to compact - Epiphyses of long bones, short bones, middle layer of flat bones of the skull (diploe) - Compact - Outer and inner coat lamellae typical Haversian systems - Volkmann’s canals - Interstitial canals ▪ Bone Spongy Articular cartilage Bone marrow cavity Capillaries Diaphysis Epiphysis Compact bone Periost Capillaries in Haversian system Capillaries in Volkman’s system ▪ Surface of compact bone • Outer surface - Synovial joint – hyaline cartilage - periosteum (periost) – membrane – dense CT, inner layer (osteoblasts) and outer layer (fibrous CT) - Inactive bone - fibrous CT in periost dominant - Collagen fibers – parallel to the bone surface - Sharpey’s fibers fix periost to the bone National Museum of Natural History NY, USA ▪ Surface of compact bone ▪ Surface of compact bone • Inner surface - lining of medullar cavity - endosteum (endost) – single cell lining – bone remodeling - red bone marrow – hematopoiesis - yellow and gray bone marrow – adipocytes or CT - rich vascularization - hematopoietic niche ▪ Endosteal urface of compact bone ▪ Bone matrix - 60% mineral compound, 24% organic compound 12% H20, 4% fat - crystals – calcium phosphate, hydroxyapatite - lining bone surface - produce ECM – collagen (I) and noncollagenous proteoglycans, glycoproteins - basophilic cytoplasm, rER, well developer Golgi Apparatus - euchromatin nucleus - osteocytes embedded in matrix - canalliculi ossium ▪ Cells of the bone - osteoblasts ▪ Cells of the bone - osteocytes - multinuclear, formed by fusion of mononuclear macrophages - bone matrix resorption ▪ Cells of the bone - osteoclasts ▪ Cells of the bone - osteoclasts - complex architecture - enzymes degrading organic matrix - HCl ▪ Cells of the bone - osteoclasts ▪ Ossification Intramembraneous Endochondral ▪ Intramembraneous ossification 2 1 3 4 5 ▪ Endochondral ossification ▪ Endochondral ossification 1 2 3 4 5 http://ns.umich.edu/Releases/2005/Feb05/img/bone.jpg ▪ Bone remodelling ▪ Clinical correlations - fracture healing Reactive Phase - fracture and inflammatory phase - granulation tissue formation Reparative Phase - cartilage callus formation - lamellar bone deposition Remodeling Phase - remodeling to original bone shape • OSTEOPOROSIS ▪ Clinical correlations – disbalance in osteosynthesis and osteoresorption • OSTEOPETROSIS • REVMATOID ARTHRITIS ▪ Skeletal joints Synarthrosis - joint by intercalated tissue (catilage, bone or c.t.) - Synostoses – joint by bone tissue – os coxae, os sacrum - Synchondrosis – joint by hyaline cartialge – development of synostosis - Symphysis – joint by fibrocartilage– os pubis, intervertebral discs - Syndesmosis – dense collage regular c.t. – sutures of skull, gomphosis Diarthrosis - synovial joint - hyaline cartilage without perichondrium - cartialge calcification in site of attachment to the bone - joint capsule - Stratum fibrosum - Stratum synoviale - Meniscus – fibrocartialge, avascular, without inervation - tendons – dense collagen regular c.t., elastic fibers - bursae – like joint capsule Further study http://www.histology.med.muni.cz/ Thank you for attention