Biological basics in relation to molecular imaging.

Transcription

1 Master s Programme Biomedical Engineering Biological basics in relation to molecular imaging. Dr. Rory Koenen Institute for Molecular Cardiovascular Research (IMCAR) RWTH University Hospital Aachen, Germany Director: Prof. Christian Weber November 10, 2009 rkoenen@ukaachen.de amayer@ukaachen.de

2 Biological basics in relation to molecular imaging. A general cross section through basic (cell) biology with a special focus on human vascular (patho-) physiology

3 Biological basics in relation to molecular imaging. cell biology (introduction): differentiation/division apoptosis and necrosis tumor biology vascular biology: angiogenesis blood vessel architecture haemodynamics heart and circulation haematology (blood celltypes and coagulation) inflammation tumor biology (Dr. Lederle)

4 Basic Cell Biology Three types of cells: Germ cells: form gametes for reproduction (meiosis) Somatic cells: most cells of the body (gr. Soma) Stem cells: Embryonic stage: pluripotent stem cells in embryonic development Adult organism: multipotent stem cells for example Hematopoietic stem cells (bone marrow) -> red blood cells, white blood cells, platelets Mesenchymal stem cells (bone marrow) -> stromal cells, fat cells, bone cells unipotent (progenitor) cells for example skin cells endothelial progenitor cells (EPC) -> endothelial cell smooth muscle progenitor cells (SMC) -> smooth muscle cell

5 Basic Cell Biology

6 Basic Cell Biology The cell membrane and its asymmetry:

7 Basic Cell Biology The cell cycle: G0 (quiescent) (programmed) cell death Regulated by cyclins and cyclin-dependent kinases.

8 Basic Cell Biology Programmed cell death Autophagy self-eating of cells, leading to their death Apoptosis from Greek: dropping off of leaves an important regulated process clean involved in tissue homeostasis, immune tolerance involved in embryonic development: e.g. removal of interdigital tissue Ota, et al. Development 2007 Necrosis non-regulated cell death resulting from direct injury messy and results in inflammation and damage to tissue environment

9 Apoptosis Discovered during developmental studies Caenorhabditis elegans: a nematode worm Adult hermaphrodite has 959 cells if certain genes are deactivated the adult has 131 additional cells so some cells are eliminated during development by apoptosis C. elegans

10 Apoptosis Homology exists with human genes: Robertson et al., Cell Death Diff. 2002

11 Apoptosis Apoptosis proceeds through a tightly regulated cascade

12 Apoptosis Apoptosis is induced / mediated by: membrane receptors such as TNFR or Fas stress factors such as mitochondrial stress, oxidative stress, DNA damage, hypoxia, reactive nitrogen species executed by caspases (cysteine-aspartic acid proteases) in a coordinated fashion (cascade) mitochondria play an integral role e.g. release of cytochrome c Active process that does not take place at 4 C (unlike necrosis) Apoptosis is characterized by: shrinkage of the cell condensation of nuclear chromosomes and fragmentation of the nucleus (pyknosis and karyorrhexis, resp.) fragmentation of DNA into discrete fragments: ladder cell membrane forming blebs and loss of membrane asymmetry: phosphatidyl serine exposure formation of cell-derived apoptotic bodies

13 Apoptosis imaging Annexin A5: strong calcium-dependent binding to phosphatidyl serine forms so-called 2-dimensional crystals on phospholipid bilayers is used in biomedical research to stain apoptotic cells Ca 2+ Ca 2+ Ca 2+ van Genderen et al., BBA, 2008

14 Apoptosis imaging Annexin A5: is used in biomedical research to stain apoptotic cells labeled with 99 Tc it has been used to visualize ischemic heart injury in vivo

15 Apoptosis imaging Annexin A5: is used in biomedical research to stain apoptotic cells labeled with 99 Tc it has been used to visualize ischemic heart injury in vivo SPECT Annexin A5 Sestamibi reperfusion 22 hours after perfusion 6 weeks after Hofstra et al. Lancet 2000

16 Apoptosis Robertson et al., Cell Death Diff. 2002

17 Carcinogenesis NIH Multiple hits are needed to transform a cell mostly transformation starts with abnormal proliferation accompanied by extension of the division limit reduction of contact inhibition evasion from immune surveillance attraction of microvasculature expression of matrix-degrading enzymes (intravasation) ability to survive without cell anchorage and in blood circulation ability to extravasate, embed, and proliferate at distant sites Metastasis

18 Steeg, Nat Rev Cancer 2003 Tumor biology

19 Tumor imaging In vivo using a quenched near infrared fluorescent matrix metalloprotease probe: probe probe + inhibitor Bremer, Nat. Med. 2001

20 Tumor biology

21 Angiogenesis Angiogenesis: the formation of new blood vessels from existing vessels Vasculogenesis: de novo formation of blood vessels (development) Arteriogenesis: formation of arteries Lymphangiogenesis: formation of lymphatic vessels Degradation of basement membrane by enzymes Attraction of endothelial cells and/or (endothelial) progenitors Proliferation of endothelial and/or smooth muscle cells Involves growth factors such as VEGF, FGF and chemoattractants such as the chemokine CXCL12/SDF1α and adhesion molecules such as VE-Cadherin and integrins

22 Angiogenesis Malpighi, 1661 Hoyer, 1905 Carmeliet, Nature, 2005

23 Angiogenesis Angiogenesis in a Petri dish: Sprouting from aortic section: Endothelial tube formation on gel matrix: Kreisel, J. Immunol. Meth Alisina Sarabi, IMCAR

24 Angiogenesis When do we want angiogenesis? Embryonic development Menstrual cycle Neovascularization after ischemia When do we NOT want angiogenesis? cancer / neoplasia several diseases such as (wet) age related macular degeneration, endometriosis Angiogenesis inhibitors (mainly VEGF antagonists) are being tested as therapeutic against cancer and other syndromes that involve angiogenesis

25 Blood vessels Several types of blood vessels exist: Artery Arteriole Capillary (organs) Venule Vein thick multilayered vessels that provides oxygen-rich blood to organs (except pulmonary artery), away from heart thin (single endothelial layer) and permeable vessels, huge surface area multilayered vessels (valves!) that bring oxygen-poor blood back to the heart, toward the heart

26 Blood vessels Artery Tunica externa/adventitia (fibrous connective tissue) Tunica media (smooth muscle cells tonus) Tunica intima (endothelial lining) Vasa vasorum: blood vessels supplying blood to large blood vessels

27 Heart and blood circulation William Harvey ( ) Marcello Malpighi (1681)

28 Heart and blood circulation

29 Heart and blood circulation Superior vena cava from head, arms Pulmonary artery to lungs Pulmonary veins from lungs Aortic arch with branches to head and arms Pulmonary artery to lungs Pulmonary veins from lungs Inferior vena cava from organs, legs Aorta to organs, legs

30 Heart and blood circulation Right atrium Left atrium Right ventricle Left ventricle (thick wall) Note the heart valves Small circulation : right ventricle to lungs to left atrium oxygen loading Large circulation : left ventricle to organs to right atrium oxygen delivery

31 Haemodynamics Laminar blood flow through vessels Blood flow approximates Poiseuille s law of laminar flow of Newtonian fluids Shear rate: velocity gradient, rate at which shear is applied Shear stress: stress applied parallel to boundary (layers), depends on viscosity of fluid Rate = v/h = 8*v m / d (blood) d h Stress = rate x * η (viscosity) = (4*η)*q / π*r 3 (blood) Approximation: blood is a complex non-newtonian fluid and blood vessels are elastic (non-rigid), flow is pulsating (heartbeat)

32 Visualization of haemodynamics with ultrasound Velocity profile Shear stress Brachialis Carotis Reneman et al., J. Vasc. Res. 2006

33 Blood: Haematology Blood plasma: protein-rich liquid without cells, contains fibrinogen Blood serum: protein-rich liquid, after coagulation and removal of cells, does not contain fibrinogen and most native coagulation factors Blood cells: Erythrocytes: biconcave anucleate red cells for oxygen transport Thrombocytes: anucleate cell particles for primary haemostasis Leukocytes: white cells for host defense (Circulating progenitors)

34 Haematology Leukocytes: Polymorphonuclear cells: Neutrophilic granulocytes (50-70% of white blood cells) Eosinophilic granulocytes (<5%) Basophilic granulocytes (<1%) First line of cellular host defense e.g. against bacteria

35 Mononuclear cells: Haematology Monocyte (blood, 2-8%) / Macrophage (tissue) phagocytic function secretion of effectors cytokines / chemokines foam cells in atherosclerosis Dendritic cell / Langerhans cell (skin): different origins. antigen gathering and presentation activation and induction of (clonal) proliferation of T cells Lymphocyte (20-45%): B cell / plasmacell: immunoglobulin production T cell: T helper cells, memory T cells, cytotoxic T cells, effector T cells: general immune response Natural killer cells: cytotoxic cells that can eliminate infected or cancer cells monocyte macrophage dendritic cell T cell

36 Hematopoiesis: Haematology

37 Blood coagulation: Haematology Primary haemostasis: formation of a platelet plug on the injury Secondary haemostasis : activation of a cascade of coagulation that lead to the formation of a fibrin clot factors

38 Haematology Extrinsic pathway / initiation Intrinsic pathway / propagation

39 Haematology Venous thromboembolism (VTE): blood clot in veins (leg vein) danger of releasing clot fragments (embolization) emboli can end up in lungs and cause infarction pulmonary embolism Technegas perfusion scintigraphy Pulmonary embolism

40 Inflammation Inflammation: Classical symptoms of inflammation: Dolor = pain Calor = heat Rubor = redness Tumor = swelling Loss of function (Virchow) acute and chronic inflammation: acute inflammation is caused by pathogens or injury and involves neutrophilic granulocytes and monocytes chronic inflammation is caused by prolonged insults and is mediated by mononuclear cells (monocytes, lymphocytes) and inflammatory mediators such as cytokines, chemokines, reactive oxygen species

41 Inflammation Acute inflammation (wound):

42 Inflammation Chronic inflammation (atherosclerosis): Weber et al., Nat. Rev. Immunol. 2008

43 Inflammation Inflammatory cell infiltration to the site of injury/infection: the leukocyte adhesion cascade: Ley et al., Nat. Rev. Immunol. 2007

44 Inflammation Inflammatory cell infiltration to the site of injury/infection: Intravital microscopy To camera Vein Blood flow Dr. Oliver Söhnlein, Karolinska Institute, Stockholm / IMCAR, Aachen

45 Inflammation Inflammatory cell infiltration to the site of injury/infection: the leukocyte adhesion cascade: Intravital microscopy To camera Fluorescence Vein Blood flow Dr. Oliver Söhnlein, Karolinska Institute, Stockholm / IMCAR, Aachen

46 intact WBC PMN depletion Dr. Oliver Söhnlein, Karolinska Institute, Stockholm / IMCAR, Aachen June, 7th,