title: Novel insights into osteogenesis and matrix remodelling associated with calcific uraemic arteriolopathy.
abstract: BACKGROUND
  Calcific uraemic arteriolopathy (CUA) or calciphylaxis is a rare, life-threatening disease predominantly occurring in patients with end-stage renal disease. Its pathogenesis has been suggested to include ectopic osteogenesis in soft tissue and the vasculature associated with extracellular matrix (ECM) remodelling.
  
  
  METHODS
  To gain further insights into the pathogenesis of CUA, we performed systematic analyses of skin specimens obtained from seven CUA patients including histology, immunohistochemistry, electron microscopy, electron dispersive X-ray analysis (EDX) and quantitative real-time RT-PCR. Skin specimens of (i) seven patients without chronic kidney disease and without CUA and (ii) seven dialysis patients without CUA served as controls.
  
  
  RESULTS
  In the CUA skin lesions, we observed a significant upregulation of bone morphogenic protein 2 (BMP-2), its target gene Runx2 and its indirect antagonist sclerostin. Furthermore, we detected an increased expression of inactive uncarboxylated matrix Gla protein (Glu-MGP). The upregulation of osteogenesis-associated markers was accompanied by an increased expression of osteopontin, fibronectin, laminin and collagen I indicating an extensive remodelling of the subcutaneous ECM. EDX analysis revealed calcium/phosphate accumulations in the subcutis of all CUA patients with a molar ratio of 1.68 ± 0.06 matching that of hydroxyapatite mineral. Widespread media calcification in cutaneous arterioles was associated with destruction of the endothelial layer and partial exfoliation of the endothelial cells (ECs). CD31 immunostaining revealed aggregates of ECs contributing to intraluminal obstruction and consecutive malperfusion resulting in the clinical picture of ulcerative necrosis in all seven patients.
  
  
  CONCLUSIONS
  Our data indicate that CUA is an active osteogenic process including the upregulation of BMP-2 signalling, hydroxyapatite deposition and extensive matrix remodelling of the subcutis.
authors.affiliation: Department of Pathology, Haartman Institute, University of Helsinki, Helsinki, Finland. rkramann@gmx.net
authors.forename: Rafael
authors.initials: R
authors.lastname: Kramann
authors.forename: Vincent M
authors.initials: VM
authors.lastname: Brandenburg
authors.forename: Leon J
authors.initials: LJ
authors.lastname: Schurgers
authors.forename: Markus
authors.initials: M
authors.lastname: Ketteler
authors.forename: Saskia
authors.initials: S
authors.lastname: Westphal
authors.forename: Isabelle
authors.initials: I
authors.lastname: Leisten
authors.forename: Manfred
authors.initials: M
authors.lastname: Bovi
authors.forename: Willi
authors.initials: W
authors.lastname: Jahnen-Dechent
authors.forename: Ruth
authors.initials: R
authors.lastname: Knüchel
authors.forename: Jürgen
authors.initials: J
authors.lastname: Floege
authors.forename: Rebekka K
authors.initials: RK
authors.lastname: Schneider
mesh_terms: D000328:Adult; D000368:Aged; D017209:Apoptosis; D015153:Blotting, Western; D002115:Calciphylaxis / Q000378:metabolism / Q000473:pathology*; D002118:Calcium / Q000378:metabolism*; D016022:Case-Control Studies; D049109:Cell Proliferation; D002470:Cell Survival; D004797:Enzyme-Linked Immunosorbent Assay; D005109:Extracellular Matrix / Q000378:metabolism*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D007676:Kidney Failure, Chronic / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D010012:Osteogenesis / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012871:Skin Diseases / Q000378:metabolism / Q000473:pathology*; D014511:Uremia / Q000378:metabolism / Q000473:pathology*; D055815:Young Adult
chemical_list: D012333:RNA, Messenger; D002118:Calcium