Endothelial progenitor cells (EPCs) have been isolated postnatally from bone marrow, blood, and both the intima and adventitia of conduit vessels. However, it is unknown whether EPCs can be isolated from the lung microcirculation. Thus we sought to determine whether the microvasculature possesses EPCs capable of de novo vasculogenesis. Rat pulmonary artery (PAEC) and microvascular (PMVEC) endothelial cells were isolated and selected by using a single-cell clonogenic assay. Whereas the majority of PAECs (approximately 60%) were fully differentiated, the majority of PMVECs (approximately 75%) divided, with approximately 50% of the single cells giving rise to large colonies (>2,000 cells/colony). These highly proliferative cells exhibited the capacity to reconstitute the entire proliferative hierarchy of PMVECs, unveiling the existence of resident microvascular endothelial progenitor cells (RMEPCs). RMEPCs expressed endothelial cell markers (CD31, CD144, endothelial nitric oxide synthase, and von Willenbrand factor) and progenitor cell antigens (CD34 and CD309) but did not express the leukocyte marker CD45. Consistent with their origin, RMEPCs interacted with Griffonia simplicifolia and displayed restrictive barrier properties. In vitro and in vivo Matrigel assays revealed that RMEPCs possess vasculogenic capacity, forming ultrastructurally normal de novo vessels. Thus the pulmonary microcirculation is enriched with EPCs that display vasculogenic competence while maintaining functional endothelial microvascular specificity.

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Abstract-TheT he proximal tubule is the major site of sodium and water reabsorption in the mammalian nephron. Paracrine regulation of sodium reabsorption in the proximal tubule by the renin/angiotensin system occurs via several angiotensin receptor subtypes (AT 1 , AT 2 , and AT 4 ). [1][2][3][4][5] The activation of angiotensin II type 1 (AT 1 ) receptors by angiotensin II increases sodium transport, whereas the activation of AT 2 and AT 4 receptors decreases sodium reabsorption in this nephron segment. [1][2][3][4][5] However, in physiological conditions, the major effect of angiotensin II on sodium transport is stimulatory, via AT 1 receptors. 1,2,6 The dopaminergic system also exerts a paracrine regulatory role on renal sodium transport in the proximal tubule. 7,8 Dopamine receptors, like the angiotensin II receptors, are expressed in brush border and basolateral membranes of RPTs. 8 -11 In contrast to the stimulatory effect of angiotensin II on sodium transport in RPTs, the major consequence of the activation of dopamine receptors is an inhibition of sodium transport. 7,8 Inhibition of renal proximal tubular angiotensin II production or blockade of AT 1 receptors increases the natriuretic effect of the D 1 -like agonist, fenoldopam. 11 D 1 -like and D 2 -like receptor agonists also antagonize the stimulatory effect of angiotensin II, acting via AT 1 receptors, on renal proximal tubular luminal sodium transport. 12,13 The 2 D 1 -like (D 1 and D 5 ) and the 3 D 2 -like (D 2 , D 3 , and D 4 ) receptors are expressed in specific segments of the mammalian kidney. 7,8,14 -19 Whereas the D 4 receptor is expressed mainly in collecting ducts, the D 3 receptor, the major D 2 -like receptor, like the D 1 and D 5 receptors, is expressed in the proximal tubule. [7][8][9][10] The distribution of D 2 receptor protein along the nephron is still uncertain. 8,19 The effect of D 2 receptors on renal sodium transport is also not clear because of the lack of agonists that are highly selective to the D 2 over the D 3 receptor. 16,17 However, 7-OH-DPAT, a ligand with a 50-fold selectivity to the D 3 over the D 2 receptor, 16 increases sodium excretion in rats. 17 Moreover, D 3 receptor-null mice have a decreased ability to excrete an acute sodium load, whereas no such limitation is found in D 2 receptor-null mice. 18,19 We surmise that the D 3 receptor may be the D 2 -like subtype receptor that interacts with the AT 1 receptor in rat RPTs.Angiotensin and dopamine receptors are expressed in immortalized rat RPT cells. 20,21 These RPT cells have charOriginal

Background A somatic mutation in GNAQ (c.548G>A;p.R183Q), encoding Gαq, has been found in syndromic and sporadic capillary malformation tissue. However, the specific cell type(s) containing the mutation is unknown. The purpose of this study was to determine which cell(s) in capillary malformations have the GNAQ mutation. Methods Human capillary malformation tissue was obtained from 13 patients during a clinically-indicated procedure. Droplet digital PCR (ddPCR), capable of detecting mutant allelic frequencies as low as 0.1%, was used to quantify the abundance of GNAQ mutant cells in capillary malformation tissue. Six specimens were fractionated by fluorescence activated cell sorting (FACS) into hematopoietic, endothelial, perivascular, and stromal cells. The frequency of GNAQ mutant cells in these populations was quantified by ddPCR. Results Eight capillary malformations contained GNAQ p.R183Q mutant cells, 2 lesions had novel GNAQ mutations (p.R183L; p.R183G), and 3 capillary malformations did not have a detectable GNAQ p.R183 mutation. Mutant allelic frequencies ranged from 2% to 11%. Following FACS, the GNAQ mutation was found in the endothelial but not the platelet-derived growth factor receptor-β-positive (PDGFRβ) cell population; mutant allelic frequencies were 3% to 43%. Conculsions Endothelial cells in capillary malformations are enriched for GNAQ mutations and are likely responsible for the pathophysiology underlying capillary malformation.