A picture shows me at a glance what it takes dozens of pages of a book to expound Ivan Turgenev, Russian writer, 1862 DEVELOPMENT OF THE CAUDAL VENA CAVA IN THE PIG EMBRYO A THREE‐DIMENSIONAL ANGIOGENIC MODEL Pieter Cornillie Thesis submitted in fulfilment of the requirements for the degree of Doctor in Veterinary Medical Sciences (Ph.D.) Promoter: Prof. dr. Paul Simoens Promoter: Prof. dr. Wim Van den Broeck Department of Morphology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium 2008 The printing of this work was sponsored by: Development of the caudal vena cava in the pig embryo: a three‐dimensional angiogenic model Pieter Cornillie, 2008, Ghent University ISBN 978‐90‐5864‐138‐0 CONTENTS GENERAL INTRODUCTION ..................................................................................... 1 CHAPTER 1: INTRODUCTION ................................................................................. 5 1.1. Vasculogenesis and angiogenesis: an update ............................................................. 5 1.1.1. Definitions .................................................................................................................. 5 1.1.2. Concepts of vasculogenesis ........................................................................................ 6 1.1.2.1. Extraembryonic vasculogenesis .................................................................................. 6 1.1.2.2. Intraembryonic vasculogenesis .................................................................................. 7 1.1.2.3. Blood vessels derived from vasculogenesis ................................................................ 8 1.1.3. Mechanisms of angiogenesis ...................................................................................... 9 1.1.3.1. VEGFs as the promoters of endothelial proliferation ............................................... 10 1.1.3.2. Angiopoietins and vessel stabilisation ...................................................................... 11 1.1.3.3. Ephrins and the specification of arteries and veins .................................................. 13 1.1.3.4. CCN family proteins as supervisors of angiogenesis ................................................. 13 1.2. The development of the caudal vena cava in the pig as a model for angiogenesis .. 15 1.2.1. Introduction .............................................................................................................. 15 1.2.2. Selection of a suitable physiological study object .................................................... 16 1.2.3. Original theory on the morphological development of the caudal vena cava in the pig embryo ............................................................................................................... 19 1.2.3.1. The caudal cardinal veins ......................................................................................... 20 1.2.3.2. The subcardinal veins ............................................................................................... 20 1.2.3.3. The supracardinal veins ............................................................................................ 22 1.2.3.4. The final construction of the caudal vena cava ........................................................ 24 1.3. Literature .................................................................................................................. 26 CHAPTER 2: PROBLEMS AND SCIENTIFIC AIMS .................................................... 35 2.1. Questioning the existing supracardinal model ......................................................... 35 2.1.1. Introduction .............................................................................................................. 35 2.1.2. Alternative theories on the development of the caudal vena cava .......................... 36 2.1.2.1. The supracardinal model .......................................................................................... 36 2.1.2.2. The caudal cardinal model........................................................................................ 37 2.1.2.3. The sacrocardinal model .......................................................................................... 40 2.1.2.4. The lateral sympathetic model ................................................................................. 41 2.1.2.5. The subcardinal model ............................................................................................. 41 2.1.2.6. Discussion ................................................................................................................. 43 2.1.3. Anatomical variations of the venous system ............................................................ 48 2.1.3.1. Case descriptions ...................................................................................................... 48 2.1.3.2. Discussion ................................................................................................................. 51 2.2. Scientific aims ........................................................................................................... 57 2.3. Literature .................................................................................................................. 58 CHAPTER 3: MATERIALS AND METHODS ............................................................. 69 3.1. Introduction .............................................................................................................. 69 3.2. Computer assisted three‐dimensional reconstruction ............................................. 70 3.2.1. Embryo collection ..................................................................................................... 70 3.2.2. Fixation and tissue processing .................................................................................. 70 3.2.3. Selection of the embryos for reconstruction ............................................................ 71 3.2.4. Acquisition of the digital images ............................................................................... 71 3.2.5. Three‐dimensional reconstruction ........................................................................... 72 3.2.5.1. Data input ................................................................................................................. 72 3.2.5.2. Image alignment ....................................................................................................... 72 3.2.5.3. Casting ...................................................................................................................... 74 3.2.5.4. Image segmentation ................................................................................................. 75 3.2.5.5. Resampling ............................................................................................................... 77 3.2.5.6. Surface generation ................................................................................................... 77 3.2.6. Evaluation ................................................................................................................. 78 3.3. Microvascular corrosion casting ............................................................................... 79 3.4. Discussion ................................................................................................................. 81 3.4.1. Artefacts and final image quality .............................................................................. 81 3.4.2. Elimination of non‐invasive three‐dimensional techniques ..................................... 84 3.5. Literature .................................................................................................................. 88 CHAPTER 4: RESULTS .......................................................................................... 93 4.1. Vascular development in the 3.7‐18.0 mm pig embryo ........................................... 93 4.1.1. General remarks ....................................................................................................... 93 4.1.2. Vascular configuration in the 3.7 mm embryo ......................................................... 93 4.1.3. Vascular configurations in the 4.6 and 4.7 mm embryos ......................................... 94 4.1.4. Vascular configurations in the 10.0 and 12.0 mm embryos ..................................... 97 4.1.5. Vascular configuration in the 18.0 mm embryo ....................................................... 99 4.1.6. Discussion ............................................................................................................... 102 4.2. Development of the infrarenal part of the porcine caudal vena cava in the late embryonic and early foetal period ......................................................................... 105 4.2.1. General remarks ..................................................................................................... 105 4.2.2. Venous pattern in the lumbar region of the 20.0 mm embryo .............................. 105 4.2.3. Venous pattern in the 22.5 mm embryo ................................................................ 106 4.2.4. Venous pattern in the lumbar region of the 27.6 mm embryo .............................. 109 4.2.5. Venous pattern in the lumbar region of the 36.7 mm foetus ................................. 112 4.2.6. Corrosion casting of the 9 cm foetus .....................................................................