Objective: Pregnant women with systemic sclerosis (SSc; scleroderma) have an increased risk of premature delivery and small full-term infants. During placental development, angiogenesis and vascular remodelling are essential for a successful pregnancy outcome. An analysis was made of the pathological changes and expression of angiogenic factors in SSc placentas.
Methods: Placenta biopsies were obtained from three patients with SSc and four healthy uncomplicated pregnancies after delivery at 34–38 weeks of gestation. The sections were stained with Masson’s trichrome and phosphotungstic-acid-haematoxylin and immunostained for connective tissue growth factor (CTGF), α-smooth muscle actin (α-SMA), vascular endothelial growth factor (VEGF), placenta growth factor (PlGF) and receptors VEGFR-1 and VEGFR-2.
Results: The pathological findings were signs of decidual vasculopathy, increased syncytiotrophoblast knotting, placental infarcts and villous hypoplasia. Severe and diffuse perivascular and stromal fibrosis of decidua and chorionic villi, and extensive deposition of fibrinoid material around decidual vessels and in intervillous spaces were observed. Strong CTGF expression in the vessel wall, decidual cells and fibroblasts and α-SMA+ myofibroblasts were found. VEGF and VEGFR-2 expression was stronger in SSc than in healthy placentas, while VEGFR-1 expression was similar to controls. PlGF immunopositivity was weaker in SSc.
Conclusion: In SSc placentas, severe fibrosis and abnormal vascular remodelling were detected. This may result in reduced blood flow leading to deep sufferance of maternal placenta and possible premature delivery.
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Systemic sclerosis (SSc; scleroderma) is characterised by diffuse vasculopathy, immunological abnormalities and widespread fibrosis of the skin and internal organs.1 SSc occurs in women of childbearing age approximately five times more frequently than in men.2 Pregnancy outcome studies showed an increased incidence of perinatal loss as well as an increased risk of preterm births and growth retardation in maternal scleroderma.2 3 4 5 Detailed studies of placental findings in SSc are limited, and few pathological descriptions showed decidual vasculopathy, placental mesenchymal villous dysplasia, infarcts and reduction of uteroplacental perfusion.5 6 7 The decidual vascular abnormalities in SSc are similar to those observed in pregnancies complicated by hypertensive disorders and are correlated with a poor perinatal outcome.5
The invasion of the maternal decidua and transformation of spiral arteries in low resistance vessels by fetal trophoblasts are essential for the successful development of the placenta. Such complex vascular transformation requires a tight coordination of angiogenic mediators.8 These factors include vascular endothelial growth factor (VEGF), placenta growth factor (PlGF) and their receptors, VEGFR-1/Flt-1 and VEGFR-2/Flk-1/KDR, the latter selectively binding VEGF but not PlGF.8 The balance between VEGF and PlGF placental expression is known to change throughout gestation, suggesting different roles during placental development and differentiation.8 VEGF and VEGFR-2 expression is more intense in early pregnancy and declines as pregnancy advances. By contrast, the expression of PlGF and VEGFR-1 increases towards term, with normal placentas expressing higher PlGF levels relative to VEGF levels in the last trimester of gestation.8 Increasing evidence indicates that altered expression of VEGF family factors/receptors is involved in placental disorders such as gestational hypertension and pre-eclampsia, resulting in poor placental perfusion and fetal hypoxia.9 10 In the skin of patients with SSc, a disordered angiogenesis involving both VEGF and its receptors was recently implicated in the pathogenesis of progressive vascular damage leading to chronic tissue ischaemia.11
In SSc, early vasculopathy is associated with fibroblast activation which results in excessive tissue deposition of extracellular matrix leading to organ dysfunction.1 Myofibroblasts and profibrotic cytokines such as transforming growth factor β (TGFβ) and connective tissue growth factor (CTGF) are believed to play a crucial role in the SSc-related fibrotic process.1 Similar mechanisms might therefore be involved in the pathology of the placenta in SSc. The aim of this study was to analyse the pathological changes in placentas from women with SSc, focusing on the expression of angiogenic factors and markers of fibrosis.
Patients and control subjects
Three patients with SSc referred to the Division of Rheumatology of the University of Florence were studied. Case 1, a 29-year-old woman with diffuse SSc12 and a modified Rodnan skin score of 2/51, presented with antinuclear and antitopoisomerase I antibodies, giant capillaries and capillary haemorrhages at nailfold videocapillaroscopy, a history of digital ulcers, normal pulmonary function, small areas of ground-glass opacity on the high-resolution CT scan, normal pulmonary artery pressure and no cardiac or renal involvement. During pregnancy she experienced a rapidly progressive increase in the skin score (14/51) and arthralgias and was treated with hydroxychloroquine and low-dose steroids. After 34 weeks of gestation the pregnancy was successfully ended. Case 2 was a 36-year-old woman with limited SSc,12 Raynaud’s phenomenon, antinuclear and antitopoisomerase I antibodies, giant capillaries and capillary haemorrhages at videocapillaroscopy with no internal organ involvement. Delivery was at 38 weeks. Case 3 was a 37-year-old woman with limited SSc, significant oesophageal involvement, antinuclear and antitopoisomerase I antibodies who delivered at 37 weeks.
Four healthy women with uncomplicated pregnancies and matched to the women with SSc for gestational age (trimester) were examined as a control group. All SSc and control women had a caesarean delivery for obstetric indications and gave written informed consent to use their placentas in the study as approved by the local ethics committee.
At delivery the placentas were weighed and full-thickness biopsies were obtained. A stratified random sampling procedure was performed to obtain six full-thickness blocks per organ. The specimens were fixed in 10% buffered formalin, dehydrated in alcohol graded series and embedded in paraffin. Sections (3 μm) were stained with haematoxylin and eosin, Masson’s trichrome and phosphotungstic-acid-haematoxylin (PTAH; Bio-Optica, Milan, Italy) to evaluate pathological changes, tissue fibrosis and fibrinoid material deposition. The sections were carefully examined by an expert pathologist who was blind to sample classification.
Serial sections (3 μm) were heated in 10 mM citrate buffer (pH 6.0) for antigen retrieval. After blocking endogenous peroxidase activity and non-specific site binding, the sections were incubated with the following primary antihuman antibodies: mouse monoclonal anti-VEGF (VEGF-A) (1:50, BD PharMingen, Heidelberg, Germany), rabbit polyclonal anti-PlGF (1:100, Abcam, Cambridge, UK), rabbit polyclonal anti-VEGFR-1 (1:50, Santa Cruz Biotechnology, Santa Cruz, California, USA), rabbit polyclonal anti-VEGFR-2 (1:50, Abcam), mouse monoclonal anti-α-smooth muscle actin (α-SMA) (1:50, Abcam) and rabbit polyclonal anti-CTGF (1:400, Abcam). The sections were incubated with biotinylated secondary antibodies and avidin-biotin-peroxidase complex (UltraVision Detection System, LabVision, Fremont, California, USA). The immunoreactivity was developed using 3-amino-9-ethylcarbazole or 3,3′-diaminobenzidine tetrahydrochloride (Vector, Burlingame, California, USA) as chromogens. Some sections were counterstained with Mayer’s haematoxylin. Normal isotype-matched IgG (Sigma, St Louis, Missouri, USA) were used to replace the primary antibodies as negative controls. The sections were observed under a light microscope (Eclipse E400, Nikon, Tokyo, Japan) and photographed by digital camera (Coolpix 2500, Nikon).
Analysis of immunostaining intensity
The immunostaining for CTGF, VEGF, PlGF, VEGFR-1 and VEGFR-2 was assessed using a semiquantitative scoring system. Three fields (×20 magnification) from three random sections of each specimen were analysed by two blinded observers and scored for location of staining in trophoblast, stromal cells and vessels. Histological grading was based on the intensity of the staining (– negative, +/– weak, + moderate, ++ intense).
Placental weights were consistent with the estimated gestational age in both patients with SSc and controls.
In all SSc placentas, signs of decidual vasculopathy, villous hypovascularity and severe perivascular and stromal fibrosis of decidua and chorionic villi were observed (fig 1). In addition, an increased syncytiotrophoblast knotting was found in all SSc cases.
Masson’s trichrome staining revealed an excessive perivascular and stromal extracellular matrix deposition in maternal decidua and chorionic villi of placentas from patients with SSc (fig 1A, B). In particular, cases 1 and 3 showed more severe fibrosis whereas, in case 2, areas of stromal fibrosis as well as areas of villous hyalinosis were observed. All SSc placentas had pathological features of vasculopathy and hypoperfusion of chorionic villi. Most decidual blood vessels showed a thickened and delaminated wall with reduction in the vessel lumen (fig 1A). Furthermore, foamy degeneration of decidual endothelial cells partially occluding the vessel lumen was found (fig 1A). In placentas from patients with SSc, extensive deposition of fibrinoid material was detected around decidual vessels and in the intervillous spaces (fig 1C). Placentas from women with SSc had increased and larger infarcts in chorionic villi (signs of hypermaturity) compared with gestational age-matched controls (fig 1C). In case 1 a greater number of placental infarcts as well as hypoplasic villi with small peripheral capillary vessels (signs of retarded growth and maturation) were observed.
Immunohistochemical analyses for CTGF, the myofibroblast marker α-SMA and VEGF family angiogenic factors/receptors were performed. In placentas from women with SSc, strong CTGF immunopositivity was detected in decidual cells, in some areas of the trophoblast, in the vessel wall (pericytes, smooth muscle cells), endothelial cells lining the capillary lumen and in stromal fibroblasts of the chorionic villi (fig 2). In contrast, very weak immunostaining was observed in control placentas (fig 2).
α-SMA immunoreactivity was evident in vascular smooth muscle cells and pericytes in both healthy and SSc placentas. Interestingly, many α-SMA+ stromal cells were found in SSc placentas only, suggesting a transdifferentiation of resting fibroblasts to activated α-SMA+ myofibroblasts (fig 2). In SSc specimens, endothelial cells of most vessels, stromal cells and the trophoblast showed a stronger VEGF immunopositivity than in control placentas (fig 3). In SSc and controls, endothelial cells, fibroblasts, decidual cells and the trophoblast were immunopositive for PlGF, but SSc samples showed weaker expression (fig 3). Furthermore, in SSc placentas, VEGFR-1 immunostaining was similar to controls in all placental components (fig 3). VEGFR-2 was strongly expressed by endothelial cells in many capillary vessels within the chorionic villi of SSc placentas but was weakly or not expressed in controls (fig 3). The results of immunostaining intensity analysis are summarised in table 1 in the online supplement.
In this study we provide evidence to show that SSc placentas are affected by fibrosis and abnormal vascular remodelling. These modifications may affect the placental function and favour the intrauterine growth restriction and premature delivery seen in clinics.3 5 13
The main pathological features observed in SSc placentas were a thickened and delaminated wall of decidual vessels and foamy degeneration of endothelial cells, as well as chorionic villous infarcts, increased syncytiotrophoblast knotting and severe villous hypovascularity and fibrosis. These vascular findings are similar to those observed in other organs in SSc14 and are consistent with the definition of “decidual vasculopathy” proposed by Langston et al15 and the “uteroplacental vascular pathological process” described by Salafia et al.16 Moreover, SSc placentas showed signs of hypermaturity, as indicated by the increased and larger infarcted areas.
We also analysed the expression of specific markers of fibrosis and the vascular remodelling process. Severe perivascular and stromal fibrosis of decidua and chorionic villi, as well as marked overexpression of CTGF and many α-SMA+ myofibroblasts, were detected. Thus, SSc placentas display fibrotic features similar to those observed in the skin and visceral organs of patients with SSc.1 17 Furthermore, an extensive deposition of fibrinoid material was found around decidual vessels and in the intervillous spaces leading to vessel collapse. Taken together, such pathological features may lead to uteroplacental hypoperfusion and tissue hypoxia, which is a major stimulus for angiogenesis.
Increasing evidence suggests that the final geometry of the villous vascular bed is defined, to some degree, by the balance of VEGF/PlGF and their receptors.8 A predominance of VEGF/VEGFR-2 promotes establishment of richly branched low-resistance capillary beds within immature placental villi during the first two trimesters of pregnancy. By contrast, the presence of poorly branched terminal capillary loops in the last trimester may be controlled by the predominance of PlGF/VEGFR-1.8 The balance between VEGF and PlGF expression is altered in SSc placentas. In fact, we found increased immunostaining for VEGF and VEGFR-2, while PlGF was markedly decreased. Our data suggest that an impairment in the physiological switch from VEGF-driven branching to PlGF-driven non-branching angiogenesis may be responsible for the altered vascular remodelling and hypoperfusion in SSc placentas. Interestingly, these results mirror those previously reported in the skin of patients with SSc where an uncontrolled expression of VEGF and its receptors has been proposed to lead to altered vessel morphology/function such as giant and bushy capillaries.11
In conclusion, this study shows an active vascular and fibrotic pathological process in the placenta, suggesting that the pathogenetic mechanism in SSc is an ongoing one that may affect newly formed tissues. Such pathological changes may favour the hypoperfusion of the maternal-fetal interface causing fetal suffering and the risk of premature delivery.
▸ Additional details are published online only at http://ard.bmj.com/content/vol69/issue2
Funding This study was supported by grants from the Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR), and the Associazione per lo studio della Sclerosi Sistemica e delle Malattie Fibrosanti (ASSMaF onlus).
Competing interests None.
Provenance and Peer review Not commissioned; externally peer reviewed.