Department of Histology and Embryology, Faculty of Medicine MU pvanhara@med.muni.cz Tissue concept and classification Petr Vaňhara, PhD How the variability of a multicellular body develops?  Tissues and organs Myocardium - 6  1013 CELLS of 200 different types - cells form functional, three-dimensional, organized aggregations of morphologically similar cells and their products or derivatives - TISSUES - tissues constitutes ORGANS and organ systems  Tissues and organs Parenchyma: functional component of a tissue (liver, lung, pancreatic, kidney parenchyma) Stroma: surrounding, supportive tissue Parenchyma Stroma LIVER Parenchyma: - Hepatocytes - Sinusoids and adjacent structures Stroma: - Connective tissue and adjacent structures - Vessels - Nerves - Bile ducts Epithelium Muscle Nerve Connective  Contemporary tissue classification Based on morphology and function: Myofibrils  contraction Mesoderm – skeletal muscle, myocard, mesenchyme – smooth muscles Rarely ectoderm (eg. m. sphincter a m. dilatator pupillae) Neurons and neuroglia Reception and transmission of electric signals Ectoderm, rarely mesoderm (microglia) Dominant extracellular matrix Connective tissue, cartilage, bone… Mesenchyme Continual, avascular layers of cells with different function, oriented to open space, with specific junctions and minimum of ECM and intercellular space. Derivates of all three germ layers  Basic principles of histogenesis Proliferation Diferentation Migration Apoptosis Tissue patterns  Functional cells of tissues differentiate from stem cells Knoblich JA. Asymmetric cell division during animal development. 2001. Nat Rev Mol Cell Biol Differentiation Self-renewal Stem cells are capable of differentiation and self-renewal Asymetric division Proliferation Formation of functional types  Stem cells Totipotent - Constitute all cells of the body incl. extraembryonic tissues - Zygote and early stages Pluripotent - All cells in the body except for trophoblast - Blastocyst – Inner cell mass - ICM (embryoblast) - Embryonic stem cells Multipotent - Give rise to various cell types of a particular tissue - Mesenchymal SC, hematopoietic SC http://www.embryology.ch/anglais/evorimplantation/furchung01.html Oligo- a unipotent - One or several cell types – hematopoietic, tissue precursors for renewal of intestinal epithelia, etc.  Stem cells as a foe Cancer stem cells - solid tumor is always heterogeneous - small population of cells with stem cell character can repopulate tumor tissue after cytotoxic therapy Tissue stem cells Renewal Low frequency (<1%) Quiescence Multipotency Long life Resistence Tumorigenicity Proliferation capacity Cancer stem cells  Microenvironment regulates tissue function and reflects its tissue composition • Embryonic development • Intercellular interaction • Space organization (dimensionality) • Gradient of morphogenes • Epigenetic profile • Gene expression dynamics • Partial pressure of gases • ECM composition • Mechanical stimulation • Perfusion and interstitial flows • Local immunity response • Metabolites Huge number of biological and physically-chemical parameters Stem cell niche? Molecular principles of histogenesis  French flag model Hox complex doi:10.1038/sj.hdy.6800872 Hox genes Highly conserved family of transcription regulators that determine body polarity, orientation and axis Tissue differentiation along anterioposterior axis Human (39 genes) Cluster Chromosome # Hox genes HoxA 7 11 HoxB 17 10 HoxC 12 9 HoxD 2 9 Microenvironment controls embryonic organogenesis Apical ectodermal ridge (AER) Zone of polarizing activity (ZPA) Manipulation with AER changes the instructions for limb development Gradients of morphogenes from AER and ZPA defines limb formation HOX Thalidomid Vascularisation AER ZPA Ectoderm Mesenchyme Fgf Shh … Proliferation Thalidomid Ectoderm MesodermEntoderm Trilqaminar germ disc (3rd week) Histogenesis and organogenesis Embryonic development  Connective tissue of head  Cranium, dentin  Skeletal muscle of trunk and limbs except cranium  Dermis of skin  Muscles of head  Urogenital system + ducts, glands and gonads  Visceral muscle and connective tissue  Serous membranes of pleura, peritoneum and pericardium  Blood cells, leukocytes  Cardiovascular and lymphatic system  Spleen  Adrenal cortex  GIT epithelium except oral cavity and part of anal canal  Extramural glands of GIT  Epithelium of bladder  Epithelium of respiratory system  Thyroid gland, parathyroid glands, thymus  Tonsils  Epithelium of cavum tympani and Eustachian tube  Epidermis, hair nails, cutaneous and mammary glands  Corneal epithelium and lens of eye  Enamel of teeth  Internal ear  Anterior pituitary gland  Epithelium of oral cavity and part of anal canal  Neural tube and derivatives - CNS - Retina - Posterior pituitary gland - Pineal body  Neural crest and derivatives: - Cranial and sensory ganglia and nerves - Schwann cells - adrenal medulla - Enteroendocrinne cells - Melanocytes - Head mesenchyme and connective tissue - Odontoblasts SurfaceectodermNeuroectoderm headParaxialIntermediateLateral EndodermEctoderm Mesoderm 6. Connective tissue Not only a tissue glue…  Connective tissue Mechanical and biological properties → surrounds other tissues, compartmentalization, support, physico-chemical environment, immunological support, storage  General composition of connective tissue (CT) Cells and extracellular matrix • Matrix – fibrous and amorphous Fibrous component - collagen - reticular - elastic Amorphous component (amorphous ground substance) - Complex matrix consisting of glycosaminoglycans, glycoproteins and proteoglycans, depending on tissue type (connective  ligament  cartilage  bone) • Cells Connective tissue – permanent and transient cell populations (fibroblasts/myofibroblasts, immune cells, adipocytes, adult stem cells) Cartilage – chondroblasts/chondrocytes Bone – osteoblasts/osteocytes/osteoclasts  Classification of CT Embryonic CT - Mesenchyme - Jelly-like CT (Wharton jelly, dental pulp, stroma of iris) Adult CT - Areolar (loose, interstitial) CT - Dense collagen irregular CT - Dense collagen regular CT - Fat (adipose tissue) - Cartilage - Bone - Blood and hematopoietic tissue - Lymphatic tissue CT Specialized CT Trophic CT (body liquids)  Embryonic origin of CT • Mesenchyme = loose tissue between germ layers • Complex network of star- or spindle-shaped cells • Jelly-like amorphous ground substance http://www.mun.ca/biology/desmid/brian/BIOL3530/DB_Ch02/DBNModel.html Week 3 of embryonic development  Basic derivatives of CT Connective BoneCartilage Mesenchyme  Cells of connective tissue Cells - Fibroblasts/fibrocytes/myofibroblasts - Heparinocytes - Macrophages of CT = histiocytes - Plasma cells - Lymphocytes - Adipocytes - Adult stem cells Extracellular matrix - Fibrous compound - Amorphous ground substance  Cells of connective tissue Mesenchymal (adult) stem cells Koch et al. BMC Biotechnology 2007 7:26 doi:10.1186/1472-6750-7-26  Extracellular matrix – fibrous component Collagen fibers - family of fibrous proteins encoded by >35 genes (2013) - polymer – subunit = tropocollagen; triple helix - different structural and mechanical properties (strength, elasticity, pliability…) - most abundant protein in human body ( 30% dry weight)  Collagen Type Localization Structure Main function I Bone, tendons, meniscus, dentin, dermis, capsules of organs, loose CT 90% of type I Fibrils (75nm) – fibers (1-20m) Resilience in pull II Hyaline and elastic cartilage Fibrils (20nm) Resilience in pressure III Skin, veins, smooth muscles, uterus, liver, spleen, kidney, lung Like I, high content of proteoglycans and glycoprotiens, reticular network Shape formation IV Basal lamina of epithelium and endtohelium, basal membranes No fibrils or fibers Mechanical support V Lamina of muscle cells and adipocytes, fetal membranes Like IV VI Interstitial tissue, chondrocytes – adhesion Connecting dermis and epidermis VII Basal membrane of epithelium VIII Some endothelia (Cornea) X Growth plate, mineralized cartilage Growth of bones, mineralization  Collagen  Collagen in LM AZAN HES HE Julian Voss-Andreae "Unraveling Collagen", 2005 Orange Memorial Park Sculpture Garden, City of South San Francisco, CA  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  Reticular fibers • collagen 3D meshwork • bone marrow, spleen, lymphatic nodules • microenvironment for e.g. hematopoietic stem cells and progenitors Amorphous extracellular matrix Colorless, transparent, homogenous substance consisting of glycosaminglycans, proteoglycans and structural glycoproteins  Extracellular matrix – ground matrix  Glycosaminoglycans linear polysaccharides composed of two disaccharide subunits – uronic acid and hexosamine glucosamin or galactosamin glucuronic or iduronic acid polysaccharides rich in hexosamines = acid mukopolysaccharides 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 They bind to protein structures (except for hyaluronic acid)  Proteoglycans — protein + dominant linear saccharide component — proteoglycan aggregates — water-binding, volume dependent of hydratation — aggrecan (cartilage) — syndecan — fibroglycan • dominant protein + branched saccharide component • interaction between cells and ECM ― fibronectin – connects collagen fibers and glykosaminoglycans, cell adhesion and migration ― laminin – basal lamina – epithelial integrity ― chondronectin – cartilage – adhesion of chondrocytes to collagen (J. Nutr. 136:2123-2126, 2006)  Structural glycoproteins  Composition of amorphous ground matrix  Classification of specialized connective tissue http://www.exploringnature.org/db/detail.php?dbID=21&detID=691  Adipose tissue • Adipocytes, fibroblasts, reticular, collagen and elastic fibers, capillarie • White and brown adipose tissue  Brown adipose tissue • fetus and child to 1st year of life • fast source of energy • typical localization – between shoulder blades, axilla, mediastinum, around kidneys, pancreas, small intestine • small cells with numerous fat droplets  White adipose tissue • adipocytes are actively form until 2nd year of life • no innervations, but rich vascularisation • adipocytes with only one lipid droplet • leptin (adipokinins)  Further study http://www.med.muni.cz/histology Thank you for attention Dr. Petr Vaňhara, PhD. pvanhara@med.muni.cz