Development of the kidney - malformations Ágnes Nemeskéri 2016 Semmelweis University Department of Anatomy, Histology and Embryology nemeskeri.agnes@med.semmelweis-univ.hu

Intermediate mesoderm (IM) PM IM The specification of renal progenitor cells is influenced by Retinoic Acid (RA) signals emanating from the paraxial mesoderm (PM). RA - diffusible morphogen – effects through concentration dependent activity

Embryonic origin of the urogenitalis system ? intermedier mesoderm - between paraxial and lateral mesoderm - after lateral folding: ventral position Urogenital ridge - paired longitudinal ridges developing in the dorsal body wall  on either side of the dorsal mesentery and aorta medial gonadal ridge and lateral nephrogenic ridge nephrogenic ridge develops into  three sets of tubular nephric structures (from head to tail): pronephros mesonephros metanephros https://classconnection.s3.amazonaws.com/962/flashcards/ 3550962/jpg/urogenital_ridge_1-14224ADADE72D060CF5.jpg urogenital ridge Gray19_with_color.png‎ (670 × 228 pixels, file size: 153 KB, MIME type: image/png)

Pronephros (Greek: first kidney) pronephric duct pronephric tubules http://image.slidesharecdn.com/embryology-urogenitalsystem-100625063133-phpapp02/95/embryology-urogenital-system-8-728.jpg?cb=1277447590 Pronephros (Greek: first kidney) https://i.ytimg.com/vi/9xD-PMekVPM/hqdefault.jpg pronephric tubules coelom pronephric duct it develops during the 4th week in the cervical region of the intermediate mesoderm the nephrogen tissue is segmented into nephrotomes – epithelialization – vesicle – pronephric tubules – nephrostome: opening into the coelom from the aorta: glomus – coiled capillary network segmental vesicles elongate and fuse to form the pronephric duct –that grows caudally towards the cloaca until the level of 12-13 somites the pronephric duct cannot filter materials outside the embryo pronephro kidney is vestigial in humans thus it degenerates soon on the 5th week https://www.google.hu/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=&url=http%3A%2F%2Fscienceblogs.com%2Fpharyngula%2F2011%2F05%2F02%2Fthe-basics-of-building-a-kidne%2F&psig=AFQjCNFWWKzAKfEgGDSdozbIIejXy6LBrw&ust=1460304710935897

Pronephros (Greek: first kidney) Pax8 (Paired box gene 8) - the earliest determinants of pronephric fate - both are under control of RA signaling - its depletion leads to a complete absence of pronephric tubule - pax8 overexpression leads to an enlargement of pronephros pteg (Proximal tubules-expressed gene protein) - an early pronephric marker - direct target of the RA signaling - essential factor for pronephric specification

2. Mesonephros (Middle kidney) Temporary excretory organ Starts to develop at the end of 4th week Functions between 6th and 10th weeks Mesonephric nephrons do not form any part of the mature kidney ! Nephron – „excretory mesonephric unit” - a single glomerulus – arising from the lateral branches of dorsal aorta - a Bowman’s capsule - a mesonephric tubule – enters the mesonephric duct Next to the mesonephric duct the intermediate mesoderm differentiates into mesonephric vesicle This vesicle elongates to form mesonephric tubules attaching to the mesonephric duct An artery extends towards the mesonephric tubule – contact each other – Bowman’s capsule On the medial side of the mesonephric duct , from the 6th cervical to 3rd lumbar segments a series of mesonephric tubules develop Mesonephric tubules collectively constitute the mesonephros

2. Mesonephros (Middle kidney) C C C Function of mesonephros - produces urine - as the more caudal nephrons form, the more cranial nephrons are already degenerating - in females some vestigial structures remain: Gartner’s duct, epoophoron, paroophoron - in males the more caudal tubules survive and give rise to efferent tubules of testis, epididymis, vas deferens, seminal vesicle + vestigial structures: appendix epididymis, paradidymis C C C https://embryology.med.unsw.edu.au/embryology/images/thumb/a/a4/Keith1902_fig081.jpg/400px-Keith1902_fig081.jpg

3. Metanephros (definitive kidney) Primordia of permanent kidney starts to develop on the 5th week - become functional on the 9th week Definitive kidney develops from 2 sources 1. Metanephric diverticulum – ureteric bud 2. Metanephrogenic blastema – metanephric mesenchyme

Ureteric bud Ureteric bud – outgrowth from the mesonephric duct near its entrance into the cloaca  reciprocal induction - retinoic acid dependent Cranial-caudal patterning establishes  a “renogenic” region within the intermediate mesoderm in the tail of the embryo –this renogenic mesoderm is the METANEPHRIC BLASTEMA The METANEPHRIC BLASTEMA secretes growth factors that induce growth of the URETERIC BUD from the caudal portion of the mesonephric duct. The URETERIC BUD proliferates and responds by secreting  growth factors that stimulates proliferation and then differentiation of the metanephric blastema into glomeruli and kidney tubules (i.e. induces the blastema to undergo mesenchymal-to-epithelial transition ).

Ureteric bud -reciprocal inductive signals!!! Ureteric bud - elongates and penetrates the blastema 1. Caudal part -the stalk develops to ureter -reciprocal inductive signals!!! 2. Cranial part - undergoes a number of dichotomous branching events to form the urinary collecting tubule system -the first 4 generations of tubules enlarge to form the major calyces - second 4 generations fuse to form the minor calyces - the end of each arched tubule induces clusters of blastema cells to form small metanephric vesicles

Metanephrogenic blastema - derives from the caudal part of the nephrogenic cord Metanephric Mesenchyme - is induced to undergo a mesenchymal-to- epithelial transformation - to form the nephron: from the epithelial glomerulus to the distal tubule Nephrons: on average 900,000–1 million in humans https://www.researchgate.net/profile/Aswin_Menke/publication/9000665/figure/fig1/AS:277733436346369@1443228219134/Fig-2-Schematic-diagrams-representing-stages-of-nephrogenesis-Upon-induction-by-the.png

Nephron formation

CHRONOLOGICAL ORDER OF THE DEVELOPMENT OF PRO-, MESO- AND METANEPHROS 1. 2. 3. 4. 20. day of embryonic life 25. day of embryonic life 35. day of embryonic life Cytokeratin fluorescence immunostaining of mouse embryo. Cytokeratin is present in nephric duct and its derivates. http://2.bp.blogspot.com/-zBVXhGbp7BY/TgjAiwoYjII/AAAAAAAAAGE/8xGoYC2YrBo/s1600/pronephric+kidmey.jpg

„Ascent„ of the kidneys

Malformations of the kidney Perturbations of inductive events (e.g. mutations of either metanephric or ureteric factors or disruption of retinoic acid signaling) may cause inhibition of ureteric bud growth and renal hypoplasia or agenesis.  Conversely, duplication or overproliferation of structures can occur if there is a gain of function of the inductive factors. Gain-of-function mutations, also called activating mutations, change the gene product such that its effect gets stronger

Horseshoe kidney (1:400) recent studies abnormal fusion result of a teratogenic event -abnormal migration of posterior nephrogenic cells, -coalesce to form the isthmus Horseshoe kidney (1:400)

Congenital polycystic disease of kidney (1:800 live birth), PKD1 and PKD2 mutation Cyst formation is tied to cilia-mediated signaling that is irregular polycystin-1 and 2 proteins appear to be involved in both autosomal and recessive polycystic kidney disease due to defects in both proteins - both proteins have communication with calcium channel proteins this causes reduction in resting (intracellular) calcium and endoplasmic reticulum storage of calcium

The fetal kidneys regulate the amount of amniotic fluid. Renal agenesis Oligohydramnion (insuficient amniotic fluid) Polyhydramnios (excess of amniotic fluid) FATE OF EXCRETED URINE IN FETAL LIFE urine is expelled into the amniotic fluid - amniotic fluid is partially swallowed by the fetus and partially is absorbed by maternal tissues. - swallowed amniotic fluid is absorbed by the digestive system of the fetus into the circulation - through the umbilical arteries it enters the placenta where waste products leave the fetus for the maternal blood. Potter’s face

Ureter duplex From our dissecting room