Venous malformation (VM) consists of a network of thin-walled ectatic venous channels with deficient media,1 and TIE2 and PIK3CA mutations have been demonstrated.2 Management of VM remains unsatisfactory.2
There are 2 embryonic stem cell (ESC)-like subpopulations within subcutaneous VM (SCVM) and intramuscular VM (IMVM): one on the endothelium expressing the ESC markers NANOG, pSTAT3, OCT4, SOX2, SALL4, and CD44; and another outside the endothelium expressing NANOG, pSTAT3, SOX2, and CD44.2 Both SCVM and IMVM express components of the renin–angiotensin system (RAS).1 This study investigated whether the primitive subpopulations within SCVM and IMVM express the RAS.
Four-micrometer-thick formalin-fixed paraffin-embedded sections of 2 representative samples each from 7 SCVM (mean age 22.9 years) and 7 IMVM (mean age 21.1 years) patients included in our previous studies,1,2 underwent immunofluorescence (IF) immunohistochemical (IHC) staining with primary antibodies OCT4 (1:30; cat#MRQ-10, Cell Marque, Santa Cruz, Calif.), SOX2 (1:200, cat#PA1-094, Thermo Fisher Scientific, Waltham, Mass.), (pro)renin receptor (PRR) (1:2000; cat#AB40790, Abcam, Cambridge, Mass.), ACE (1:40; cat#3C5, Serotec, Raleigh, N.C.), angiotensin II receptor 1 (ATIIR1) (1:25; cat#ab9391, Abcam), and angiotensin II receptor 2 (ATIIR2) (1:2000; cat#NBPI-77368, Novus Biologicals, Littleton, Colo.). Vectafluor Excel anti-rabbit 594 (ready-to-use; cat#VEDK-1594, Vector Laboratories, Burlingame, Calif.) and Vectafluor Excel anti-mouse (ready-to-use; cat#VEDK2488, Vector Laboratories) secondary antibodies combinations, were used for IF IHC detection.
IF IHC-stained slides were viewed and imaged using an Olympus FV1200 biological confocal laser-scanning microscope, and the images were deconvoluted using cellSens Dimension 1.11 software 2D deconvolution algorithm (Tokyo, Japan).
(Pro)renin receptor (red) was expressed by the OCT4+ (green) cells on the endothelium and pericytes in SCVM (Fig. 1A) and IMVM (see figure, Supplemental Digital Content 1, http://links.lww.com/PRSGO/B49, which displays representative IF IHC-stained sections of IMVM, demonstrating expression of PRR (A, red) by the OCT4+ [A, green] cells on the endothelium and cells outside of the endothelium, and ACE [B, green] and ATIIR1 [C, green] by the SOX2+ [B and C, red] cells on the endothelium and cells outside the endothelium. Angiotensin II receptor 2 [D, red] was expressed by the OCT4+ [D, green] cells on the endothelium and cells outside the endothelium. Cell nuclei were counterstained with 4′, 6′-diamindino-2-phenylindole [A–D, blue]. Original magnification: 600×, http://links.lww.com/PRSGO/B23). ACE (green) was expressed by the SOX2+ (red) cells, predominantly in the endothelium in SCVM (Fig. 1B) and IMVM (see figure, Supplemental Digital Content 1, http://links.lww.com/PRSGO/B49). Angiotensin II receptor 1 (green) was expressed by the SOX2+ (red) cells on the endothelium and pericytes in SCVM (Fig. 1C) and IMVM (see figure, Supplemental Digital Content 1). Angiotensin II receptor 2 (red) was expressed by the OCT4+ (green) endothelium and pericytes in SCVM (Fig. 1D) and IMVM (see figure, Supplemental Digital Content 1, http://links.lww.com/PRSGO/B49). Negative controls for IF IHC staining for SCVM and IMVM samples demonstrated minimal staining (data not shown; see figure, Supplemental Digital Content 1, http://links.lww.com/PRSGO/B49).
We hypothesize that the ESC-like subpopulations may give rise to cells in VM, and that the RAS may sustain these ESC-like subpopulations. The novel finding of the expression of components of the RAS by the ESC-like subpopulations within SCVM and IMVM suggests that these primitive cells may be a novel therapeutic target by manipulation of the RAS using medications such as β-blockers and ACE inhibitors. In vitro and in vivo functional studies are needed to determine the effects of administration of RAS modulators.
Serendipitous observation of reduced rectal bleeding and anemia in a case of rectosigmoid junction VM following propranolol and celecoxib treatment3 could be explained by the inhibitory effects of a β-blocker and COX2 inhibitor on the RAS. (Pro)renin receptor, expressed on the endothelium of VM, signaling through the Wnt-β-catenin pathway4 to maintain pluripotency of ESCs5 may be the mechanism by which the RAS regulates the ESC-like subpopulations within VM.
We thank Ms Liz Jones of the Gillies McIndoe Research Institute for her assistance in immunohistochemical staining. This study was carried out with the approval of the Central Health and Disability Ethics Committee (Ref. 13/NTB/155) with written informed consent from all subjects in accordance with the Declaration of Helsinki.
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3. Abematsu T, Okamoto Y, Nakagawa S, et al. Rectosigmoid colon venous malformation successfully treated with propranolol and celecoxib. J Pediatr Surg Case Reports. 2015;3:331–333.
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