CARTILAGE AND BONE Department of Histology and Embryology, Faculty of Medicine MU pvanhara@med.muni.cz Petr Vaňhara Consistency Cells Fibers Amorphous ground substance Soft ↑ ↓ ↑ Rigid ↓ ↑ ↓ CONNECTIVE TISSUE 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 CARTILAGE ▪ Perichondrium – connective tissue around cartilage (except joints) ▪ Extracellular matrix – water, proteoglycans and collagen fibrils ▪ Cells of cartilage - chondroblasts, chondrocytes Solid consistence Pressure elasticity Growth ECM production Nutrition Growth CARTILAGE – COMPOSITION AND STRUCTURE Hyaline Elastic Fibrous DISTRIBUTION http://chickscope.beckman.uiuc.edu/explore/embryology/day14/dev2.html Hyaline Alcian Blue&Alizarin Red - most abundant - temporary embryonal/fetal skeleton - epiphyseal growth plate - articulation (joints) respiratory passages DISTRIBUTION • mesenchymal origin • typical ultrastructure of proteosynthetically active cells • production of extracellular matrix • interstitial proliferation • isogenetic groups, lacunae ▪ Chondroblasts and chondrocytes CELLS OF CARTILAGE Runx2 Osx Sox9 Runx2 C/EBP PPAR Collagen 2A aggrecan DIFFERENTIATION OF CHONDROBLASTS DIFFERENTIATION OF CHONDROBLASTS AND CHONDROCYTES GROWTH OF HYALINE CARTILAGE GROWTH OF HYALINE CARTILAGE • oval → round cells • rich in organelles, especially rER and GA • glycogen granules (anaerobic metabolism) • occasionally lipid droplets ULTRASTRUCTURE OF CHONDROCYTES ULTRASTRUCTURE OF CHONDROCYTES ULTRASTRUKTURA CHONDROCYTŮ ULTRASTRUCTURE OF CHONDROBLASTS ▪ Extracelullar matrix biomechanical properties HOW IT WORKS? glycosaminoglycans proteoglycans fibers water 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 GLYCOSAMINOGLYCANS IN CARTILAGE 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 GLYCOSAMINOGLYCANS IN CARTILAGE Chondroitinsulphate Keratansulphate • proteoglycans - protein + dominant linear saccharide component - proteoglycan aggregates - water-binding – 80%, volume dependent of hydratation - aggrecan (cartilage) - syndekan - fibroglykan PROTEOGLYCANS AND FIBERS • collagen fibrils - col II + col IX/XI - thin fibrils (15-20 nm → no striation) that do not form fibers like col I - interconnected with perichondrium - elastic fibers • pericellular • territorial • interterritorial transduction of biochemical and biomechanical signals TISSUE ARCHITECTURE OF CARTILAGE ECM • pressure elasticity - proteoglycans – polyanionic (COO-, SO4 II-) - expansion prevented by collagen fibrils - repulsion forces • biphasic model of cartilage → 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 TISSUE ARCHITECTURE OF CARTILAGE ECM I. tangential (superficial) zone II. transitional zone III. radial (deep) zone tide mark I. mineralized cartilage zone subchondral bone • synovial cartilage TISSUE ARCHITECTURE OF CARTILAGE ECM Exchange of metabolites Apositional growth Interstitial proliferation NUTRITION AND GROWTH ▪ stratum fibrosum - biomechanics ▪ stratum chondrogenicum - growth PERICHONDRIUM ▪ 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: mesenchymal (c.t.) origin - synovial fluid rich in hyaluronans - bursae synoviales, vaginae tendineum http://www2.indstate.edu/thcme/mmmoga/histology/slide35.html SYNOVIUM https://www.dartmouth.edu/~anatomy/Histo/lab_2/bone/DMS090/53.gif - acidophilic elastic fibers dispersed in matrix - no isogenetic groups - auricula, meatus, larynx, epiglottis ELASTIC CARTILAGE • 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 FIBERS ELASTIC CARTILAGE • fibrous compound dominant – collagen I and II – mechanical durability • minimum of amorphous matrix-fibers visible • intervertebral discs, symphysis pubis, articular discs, meniscus FIBROCARTILAGE • Cartilage – no innervation, no vascularization – no spontaneous regeneration • No migration of chondrocytes to site of damage • Initiation of other degenerative events leading to cartilage erosion (arthritis) Therapy: • joint mobility • restoration of biochemical and biophysical parameters of cartilage • prevention of further damage • removal of damaged tissue, autologous transplantation • MSCs on biocompatible scaffolds (still only experimental) CLINICAL CORRELATION Further reading: ▪ BONE • Primary (woven, fibrous) • Secondary (lamellar) - Lamellae – collagen fibers in concentric layers (3-7m) around a canal with capillaries = Haversian system (osteon) HISTOLOGICAL CLASSIFICATION OF BONE TISSUE PRIMARY (WOVEN) BONE • 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 cementum SECONDARY (LAMELLAR) BONE • 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 SECONDARY (LAMELLAR) BONE SECONDARY (LAMELLAR) BONE SECONDARY (LAMELLAR) BONE Capillary Osteoblasts Interstitial lamella Osteocyte in lacune Canaliculi ossium Lamellae • 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 BONE SURFACES National Museum of Natural History NY, USA BONE SURFACES BONE SURFACES Inactive Active • Inner surface – lining of cavities - 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 BONE SURFACES ENDOSTEAL SURFACE OF COMPACT BONE - 60% mineral compound, 24% organic compound 12% H20, 4% fat - crystals – calcium phosphate, hydroxyapatite BONE MATRIX BONE MATRIX BONE MATRIX BONE MATRIX Production and degradation of bone ECM • collagen (I) • non-collagenous proteins • proteoglycans/glycoproteins, • mineralized matrix BONE CELLS – OSTEOBLASTS, OSTEOCYTES, OSTEOCLASTSY Architecture of mineralized tissue and bone morphology Phosphate and calcium metabolism Bone marrow and hematopoiesis 10.13140/RG.2.2.20595.32802 ▪ Inner celllayer of perios, Haversian cannals and endost - origin in embryonic mesenchyme - mitotic divisions, diferentiaation to osteoblasts BONE CELLS - OSTEOPROGENITORS BONE CELLS - OSTEOBLASTS - lining bone surface - produce ECM – collagen (I) and noncollagenous proteoglycans, glycoproteins - basophilic cytoplasm, rER, well developed Golgi Apparatus - euchromatin nucleus - osteocytes embedded in matrix - canalliculi ossium BONE CELLS – OSTEOBLASTS BONE CELLS – OSTEOCYTES BONE CELLS - OSTEOCYTES 10.13140/RG.2.2.20595.32802 - multinuclear, formed by fusion of mononuclear macrophages - bone matrix resorption BONE CELLS – OSTEOCLASTS BONE CELLS – OSTEOCLASTS - complex architecture - enzymes degrading organic matrix - HCl BONE CELLS – OSTEOCLASTS BONE CELLS - OSTEOCLASTS • Intramembraneous • Endochondral BONE OSSIFICATION INTRAMEMBRANEOUS OSSIFICATION 2 1 3 4 5 ENDOCHONDRAL OSSIFICATION ENDOCHONDRAL OSSIFICATION ENDOCHONDRAL OSSIFICATION https://doi.org/10.1159/000088791 ENDOCHONDRAL OSSIFICATION GROWTH PLATE GROWTH GROWTH PLATE GROWTH GROWTH PLATE GROWTH PLATE • Reserve zone • Zone of proliferation • Zone of hypertrophy • Zone of calcification • Line of erosion • Zone of ossification Ossification in growth plate is a 3D phenomenon http://ns.umich.edu/Releases/2005/Feb05/img/bone.jpg BONE REMODELLING Reactive phase - fracture and inflammatory phase - granulation tissue formation Reparative phase - cartilage callus formation - lamellar bone deposition Remodeling phase - remodeling to original bone shape CLINICAL CORRELATIONS – FRACTURE HEALING • OSTEOPOROSIS • OSTEOPETROSIS • REVMATOID ARTHRITIS CLINICAL CORRELATIONS – DISBALANCE OF BONE HOMEOSTASIS • PAGET DISEASE Synarthrosis - joint by intercalated tissue (catilage, bone or c.t.) - Synostoses – joint by bone tissue – os coxae, os sacrum - Synchondrosis – joint by hyaline cartilage – 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 - cartilage 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 JOINTS http://www.histology.med.muni.cz/ FURTHER STUDY Thank you for attention