The main pathogenic feature of preeclampsia is maternal endothelial dysfunction that results from impaired angiogenesis and reduced endothelial repair capacity. In addition, preeclampsia risk is associated with vitamin D deficiency. We hypothesized that vitamin D3 stimulates proangiogenic properties of endothelial colony-forming cells (ECFCs). ECFCs were obtained and cultured from cord blood and characterized by immunocytochemistry and flow cytometry. Proliferation, total length of tubule formation on Matrigel, expression of VEGF mRNA, and pro-matrix metalloproteinases (MMP)-2 activity were assessed after treatment of ECFCs with vitamin D 3. Specificity of the observed effects was tested by blocking the vitamin D receptor (VDR) or the VEGF signaling pathway. ECFCs treated with 10 nM vitamin D3 showed a 1.27 times higher tubule formation compared with vehicle-treated controls (1.27 Ϯ 0.19) as well as a 1.36 times higher proliferation rate (1.36 Ϯ 0.06). Vitamin D3 induced pro-MMP-2 activity (1.29 Ϯ 0.17) and VEGF mRNA levels (1.74 Ϯ 0.73) in ECFCs. VDR blocking by pyridoxal-5-phosphate (0.73 Ϯ 0.19) or small interfering RNA (0.75 Ϯ 0.17) and VEGF inhibition by Su5416 (0.56 Ϯ 0.16) or soluble fms-like tyrosine kinase-1 (0.7 Ϯ 0.14) reduced tubule formation and pro-MMP-2 activity (pyridoxal-5-phosphate: 0.84 Ϯ 0.09; Su5416: 0.79 Ϯ 0.11; or sFlt: 0.88 Ϯ 0.13). This effect was neutralized by vitamin D3. Consequently, vitamin D3 significantly promoted angiogenesis in ECFCs in vitro possibly due to an increase in VEGF expression and pro-MMP-2 activity. Since angiogenesis is a crucial feature in the pathophysiology of preeclampsia these findings could explain the positive influence of vitamin D3 in reducing preeclampsia risk. vitamin D; preeclampsia; ECFC; angiogenesis; VEGF VITAMIN D, PRIMARILY KNOWN for its important role in calcium homeostasis and bone metabolism, influences the cardiovascular system through unclear mechanisms (33). Vitamin D deficiency is associated with increased all-cause and cardiovascular disease mortality, coronary heart disease, and various cardiovascular risk factors (33).Preeclampsia, a pregnancy-specific disorder that affects 3-7% of all pregnancies, is a major cause of maternal and fetal morbidity and mortality (43) and is associated with an increased risk for cardiovascular events later in life (6). Endothelial dysfunction underlies the hypertension, proteinuria, and multiorgan damage that occur during preeclampsia. The mechanisms that contribute to the disturbed endothelial homeostasis in the pathophysiology of preeclampsia remain unclear (41,46). Compared with normal pregnancies, preeclampsia is characterized by marked changes in vitamin D and calcium metabolism (3). Epidemiological studies have demonstrated an association between low maternal vitamin D levels and the incidence of preeclampsia (23, 27) and suggest vitamin D deficiency to be an independent risk factor for the development of preeclampsia (7). Moreover, vitamin D supplementation studies also showed protective effects on pr...

Vertebrate limb outgrowth is driven by a positive feedback loop that involves Sonic hedgehog (Shh) and Gremlin1 (Grem1) in the posterior limb bud mesenchyme and Fibroblast growth factors (Fgfs) in the overlying epithelium. Proper spatio-temporal control of these signaling activities is required to avoid limb malformations such as polydactyly. Here we show that, in Tbx2-deficient hindlimbs, Shh/Fgf4 signaling is prolonged, resulting in increased limb bud size and duplication of digit 4. In turn, limb-specific Tbx2 overexpression leads to premature termination of this signaling loop with smaller limbs and reduced digit number as phenotypic manifestation. We show that Tbx2 directly represses Grem1 in distal regions of the posterior limb mesenchyme allowing Bone morphogenetic protein (Bmp) signaling to abrogate Fgf4/9/17 expression in the overlying epithelium. Since Tbx2 itself is a target of Bmp signaling, our data identify a growth-inhibiting positive feedback loop (Bmp/Tbx2/Grem1). We propose that proliferative expansion of Tbx2-expressing cells mediates self-termination of limb bud outgrowth due to their refractoriness to Grem1 induction.

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ZusammenfassungIn der Transplantationsdiagnostik werden die Seren der Patienten auf der Warteliste jedes Quartal auf präexistierende Anti-HLA-Antikörper untersucht. Jedoch kann die Existenz von zirkulierenden peripheren Antikörpern, die von knochenmarkresidierenden Plasmazellen sezerniert wurden, keine zuverlässige Information über das Zellkompartment von B-Gedächtniszellen geben. Die Exposition mit einem inkompatiblen HLA-Antigen kann immer die Aktivierung vorhandener B-Gedächtniszellen auslösen. Die Analyse von B-Gedächtniszellen ermöglicht die Erhebung von belastbaren Daten über den individuellen Immunstatus eines Patienten.