Department of Histology and Embryology, Faculty of Medicine MU pvanhara@med.muni.cz Tissue concept and classification Petr Vaňhara, PhD  Cells are the basic units of any organism  New cells origin only from other cells  Cells exchange energy (open thermodynamic system)  Genetic information is inherited in new generations  Chemical and structural composition of cells is generally identical MODERN CELL TEHORY Theodor SchwannMatthias Jacob Schleiden Omnis cellula e cellula! Rudolf Wirchow J.E.P. Robert Remak CELL AND TISSUE VARIABILITY IN A MULTICELLUALR BODY - 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 Myocardium TISSUES AND ORGANS 25-40109 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 TISSUES AND ORGANS Epithelium Muscle Nerve Connective 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 CONTEMPORARY TISSUE CLASSIFICATION  classical histological definition is based on microscopic visualization Functional, three-dimensional, organized aggregation of morphologically similar cells, their products and derivatives TISSUE DEFINITION HISTOLOGY IS NOT ONLY ABOUT MICROSCOPY Proliferation Diferentation Migration Apoptosis Tissue patterns BASIC PRINCIPLES OF HISTOGENESIS 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 FUNCTIONAL CELL TYPES DIFFERENTIATE FROM 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 STEM CELLS Tissue (adult) stem cells - regeneration and renewal of tissues - GIT, CNS, mesenchyme - regenerative medicine, cancer biology Embryonic stem cells (ESCs) - embryoblast of blastocyst - pluripotent - modelling of early embryogenesis, regenerative medicine STEM CELLS IN HUMAN BODY Induced pluripotent stem cells (iPSc) - adult differentiated cell (fibroblast) is reprogrammed into pluripotent state - differentiation into desired cell type - regenerative medicine, cell and gene therapy Nobel prize 2012 Disease modelling Drug testing Tissue replacement … STEM CELLS AS RESEARCH TOOLS hESCs hiPSCs iPSCs SHARE FUNDAMENTAL PROPERTIES WITH hESCs Age-related macular degeneration neovascularisation Clinical trial hiPSCs Retinal pigment epithelium STEM CELLS AS THERAPY 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 STEM CELLS AS FOES WHY ARE TISSUES DIFFERENT? • Induction of differentiation • Terminal differentiation • Determination and commitment -blast -cyte eg. myeloblast granulocyte CELL DIFFERENTIATION doi:10.1038/nrg3209 DIFFERENTIATION IS DRIVEN BY GENE TRANSCRIPTION doi:10.1038/nature10523 TISSUE DIFFER IN THEIR GENETIC AND EPIGENETIC PROFILES Adhesion molecules Growth factors ECM components Cell interactionsMetabolites Immunity Inflammation CELLS CAN CREATE UNIQUE MICROENVIRONMENT • 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 MICROENVIRONMENT REGULATES TISSUE FUNCTION STEM CELL NICHE HEMATOPOIETIC NICHE Apoptosis Regeneration Senescence Transformation MICROENVIRONMENT IS NECESSARY FOR TISSUE HOMEOSTASIS MICROENVIRONMENT IS OF CLINICAL IMPORTANCE MOLECULAR PRINCIPLES OF HISTOGENESIS LEWIS WOLPERT AND FRENCH FLAG MODEL WHY DO TIGERS HAVE STRIPES? Reakčně-difúzní systém TISSUE PATTERNS ARE DRIVEN BY GRADIENTS OF MORPHOGENES 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 HOX COMPLEX TEMPORO-SPATIAL EXPRESSSION OF MORPHOGENES DRIVES FINAL LOCALIZATION, ORIENTATION AND MORPHOLOGY OF TISSUES AND ORGANS MANIPULATING AER ALTERS INSTRUCTIONS FOR LIMB DEVELOPMENT TEMPORO-SPATIAL EXPRESSION OF DIFFERENT REGULATORS DETERMINES FINAL LOCALIZATION, ORIENTATION AND MORPHOLOGY OF TISSUES AND ORGANS http://courses.biology.utah.edu/bastiani/3230/DB%20Lecture/Lectures/b14Limb.html ZPA SPECIFIES POSITIONAL INFORMATION IN LIMB BUD MORPHOGENES FROM AER AND ZPA DEFINES LIMB FORMATION http://courses.biology.utah.edu/bastiani/3230/DB%20Lecture/Lectures/b14Limb.html HOX PATTERN DRIVES TRANSCRIPTIONAL RESPONSE HOX Vascularisation Fgf Shh … Proliferation Thalidomid STORY OF THALIDOMID Thalidomid embryopathy • phocomelia • amelia • anophtalmia/microphtalmia • abnormal kidneys, heart, GIT, genitalia Frances Oldham Kelsey, FDA USA Untested drug to pregnant mothers?!! Not in U.S.! Ectoderm MesodermEndoderm Trilqaminar germ disc (3rd week) HISTOGENESIS AND ORGANOGENESIS  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 EMBRYONIC DEVELOPMENT 6. CONNECTIVE TISSUE Not just a tissue glue… Mechanical and biological properties → surrounds other tissues, compartmentalization, support, physico-chemical environment, immunological support, storage CONNECTIVE TISSUE 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 GENERAL COMPOSITION OF CONNECTIVE TISSUE 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) CLASSSIFICATION OF CONNECTIVE TISSUE • 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 DAY 12 of embryonic development EMBRYONIC ORIGIN OF CONNECTIVE TISSUE Connective BoneCartilage Mesenchyme DERIVATIVES 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 CELLS OF CONNECTIVE TISSUE 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) EXTRACELLULAR MATRIX – FIBROUS COMPONENT 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 AZAN HES HE COLLAGEN IN LIGHT MICROSCOPE Julian Voss-Andreae "Unraveling Collagen" 2005 Orange Memorial Park Sculpture Garden, City of South San Francisco, CA COLLAGEN IN ART • 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 • collagen 3D meshwork • bone marrow, spleen, lymphatic nodules • microenvironment for e.g. hematopoietic stem cells and progenitors RETICULAR FIBERS RETICULAR CONNECTIVE TISSUE Amorphous extracellular matrix Colorless, transparent, homogenous substance consisting of glycosaminglycans, proteoglycans and structural glycoproteins EXTRACELLULAR MATRIX – GROUND SUBSTANCE linear polysaccharides composed of two disaccharide subunits – uronic acid and hexosamine glucosamin or galactosamin glucuronic or iduronic acid polysaccharides rich in hexosamines = acid mukopolysaccharides GLYCOSAMINOGLYCANS 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 They bind to protein structures (except for hyaluronic acid) GLYCOSAMINOGLYCANS — protein + dominant linear saccharide component — proteoglycan aggregates — water-binding, volume dependent of hydratation — aggrecan (cartilage) — syndecan — fibroglycan PROTEOGLYCANS • 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 ECM http://www.exploringnature.org/db/detail.php?dbID=21&detID=691 CLASSIFICATION OF SPECIALIZED CONNECTIVE TISSUE • Adipocytes, fibroblasts, reticular, collagen and elastic fibers, capillaries • White and brown adipose tissue 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 BROWN ADIPOSE TISSUE • adipocytes are actively formed until 2nd year of life • no innervations, but rich vascularisation • adipocytes with only one lipid droplet • leptin (adipokinins) WHITE ADIPOSE TISSUE http://www.med.muni.cz/histology FURTHER STUDY Thank you for attention Petr Vaňhara, PhD. pvanhara@med.muni.cz