Anticalcification effects of DS-1211 in pseudoxanthoma elasticum mouse models and the role of tissue-nonspecific alkaline phosphatase in ABCC6-deficient ectopic calcification.

Pseudoxanthoma elasticum (PXE) is a multisystem, genetic, ectopic mineralization disorder with no effective treatment. Inhibition of tissue-nonspecific alkaline phosphatase (TNAP) may prevent ectopic soft tissue calcification by increasing endogenous pyrophosphate (PPi). This study evaluated the anticalcification effects of DS-1211, an orally administered, potent, and highly selective small molecule TNAP inhibitor, in mouse models of PXE. Calcium content in vibrissae was measured in KK/HlJ and ABCC6-/- mice after DS-1211 administration for 13-14 weeks. Pharmacokinetic and pharmacodynamic effects of DS-1211 were evaluated, including plasma alkaline phosphatase (ALP) activity and biomarker changes in PPi and pyridoxal-phosphate (PLP). Anticalcification effects of DS-1211 through TNAP inhibition were further evaluated in ABCC6-/- mice with genetically reduced TNAP activity, ABCC6-/-/TNAP+/+ and ABCC6-/-/TNAP+/-. In KK/HlJ and ABCC6-/- mouse models, DS-1211 inhibited plasma ALP activity in a dose-dependent manner and prevented progression of ectopic calcification compared with vehicle-treated mice. Plasma PPi and PLP increased dose-dependently with DS-1211 in ABCC6-/- mice. Mice with ABCC6-/-/TNAP+/- phenotype had significantly less calcification and higher plasma PPi and PLP than ABCC6-/-/TNAP+/+ mice. TNAP plays an active role in pathomechanistic pathways of dysregulated calcification, demonstrated by reduced ectopic calcification in mice with lower TNAP activity. DS-1211 may be a potential therapeutic drug for PXE.

Minocycline Attenuates Excessive DNA Damage Response and Reduces Ectopic Calcification in Pseudoxanthoma Elasticum.

Pseudoxanthoma elasticum (PXE) is a hereditary ectopic calcification disorder affecting the skin, eyes, and blood vessels. Recently, the DNA damage response (DDR), in particular PARP1, was shown to be involved in aberrant mineralization, raising the hypothesis that excessive DDR/PARP1 signaling also contributes to PXE pathogenesis. Using dermal fibroblasts of patients with PXE and healthy controls, (lesional) skin tissue, and abcc6a‒/‒ zebrafish, we performed expression analysis of DDR/PARP1 targets with QRT-PCR, western blot, immunohistochemistry, and enzyme activity assays before and after treatment with the PARP1 inhibitor minocycline. PARP1 and the ATM‒p21‒p53 axis was found to be significantly increased in PXE. In addition, PARP1 downstream targets IL-6, signal transducer and activator of transcription 1/3, TET1, and RUNX2 were upregulated, whereas the RUNX2 antagonist microRNA-204 was decreased. In PXE fibroblasts, DDR/PARP1 signaling increased with advancing ectopic calcification. Minocycline treatment attenuated DDR/PARP1 overexpression and reduced aberrant mineralization in PXE fibroblasts and abcc6a‒/‒ zebrafish. In summary, we showed the involvement of excessive DDR/PARP1 signaling in PXE pathophysiology, identifying a signal transducer and activator of transcription‒driven cascade resulting in increased expression of the epigenetic modifier TET1 and procalcifying transcription factor RUNX2. Minocycline attenuated this deleterious molecular mechanism and reduced ectopic calcification both in vitro and in vivo, fueling the exciting prospect of a therapeutic compound for PXE.

A case report: pseudoxanthoma elasticum diagnosed based on ocular angioid streaks and the curative effect of Conbercept treatment.

BACKGROUND: This article is a case report of pseudoxanthoma elasticum (PXE) which was diagnosed based on significant angioid streaks (AS) with choroidal neovascularization (CNV) and regain normal visual function by intravitreal injection with Conbercept. CASE PRESENTATION: A 51-year-old woman was referred to the Ophthalmology Department of Qingdao Municipal Hospital (Qingdao, China) on September 14, 2020 for metamorphopsia and loss of vision in the left eye in the preceding three days. Past history: high myopia for more than 30 years, best corrected visual acuity (BCVA) of both eyes was 1.0 (5 m Standard Logarithm Visual Acuity chart in decimal notations), hypertension for six years, and cerebral infarction two years ago, no history of ocular trauma or surgeries or similar patients in family was documented. We used methods for observation, including fundus examination, optical coherence tomography (OCT), fluorescein angiography combined with indocyanine green angiography (FFA + ICGA). Due to her symptoms and manifestations, along with the appearance of her neck skin, which resembled 'chicken skin', we speculated that she should be further examined at the Department of Dermatology by tissue paraffin section and molecular pathology analyses, and the diagnosis of PXE was then confirmed. After intravitreal injection with Conbercept (10 mg/ml, 0.2 ml, Chengdu Kanghong Biotechnologies Co., Ltd.; Chengdu, Sichuan, China) she regained her BCVA. CONCLUSIONS: This patient regained her best corrected visual acuity through intravitreal injection with Conbercept. To the best of our knowledge, no publications are available on cases in which a vision loss and the normal visual function can be reverted by intravitreal injection with Conbercept. Although PXE is a disease with low incidence and thus no effective cure established, targeted symptomatic treatment can effectively retard the disease progression and improve visual function, such as intravitreal injection with Conbercept.

A phytic acid analogue INS-3001 prevents ectopic calcification in an Abcc6-/- mouse model of pseudoxanthoma elasticum.

Pseudoxanthoma elasticum (PXE), a prototype of heritable ectopic calcification disorders, affects the skin, eyes and the cardiovascular system due to inactivating mutations in the ABCC6 gene. There is no effective treatment for the systemic manifestations of PXE. In this study, the efficacy of INS-3001, an analogue of phytic acid, was tested for inhibition of ectopic calcification in an Abcc6-/- mouse model of PXE. In prevention study, Abcc6-/- mice, at 6 weeks of age, the time of onset of ectopic calcification, were treated with INS-3001 with 0.16, 0.8, 4, 20 or 100 mg/kg/day administered by subcutaneous implantation of osmotic pumps, as well as 4 mg/kg/day by subcutaneous injection thrice weekly or 14, 4 and 0.8 mg/kg/day once weekly subcutaneous injection. Mice were necropsied at 12 weeks of age. Histologic examination and quantitative calcium assay revealed that mice receiving 6 weeks of continuous INS-3001 administration via osmotic pumps showed dose-dependent inhibition of muzzle skin calcification with complete response at 4 mg/kg/day and a minimum effective dose at 0.8 mg/kg/day. INS-3001 plasma concentrations were dose-dependent and largely consistent during treatment for each dose. thrice weekly and once weekly subcutaneous injections of INS-3001 also prevented calcification. In established disease study, 12-week-old Abcc6-/- mice with extensive calcification were continuously administered INS-3001 at 4 mg/kg/day for a follow-up of 12 weeks. INS-3001 treatment was found to stabilize existing calcification that had developed at start of treatment. These results suggest that INS-3001 may provide a promising preventive treatment strategy for PXE, a currently intractable ectopic calcification disorder.

Polypoidal choroidal vasculopathy in a patient with angioid streaks treated by bevacizumab.

OBJECTIVE: We report the association of polypoid choroidal vasculopathy (PVC) with angioid streaks (AS) secondary to pseudoxanthoma elasticum (PXE) treated by intravitreal injection of bevacizumab. CASE REPORT: A 50-year-old patient, followed in dermatology for a PXE, who consulted for a consulted for a decreased vision in his right eye (RE) for a month. On examination, best corrected visual acuity (BCVA) was at 1/20 P14 in the RE and at 8/10 P2 in the left eye (LE). Fundus examination revealed AS in both eyes, large patches of exudate at the posterior pole with retinal hemorrhages in the RE. Fluorescein angiography (FA) showed constant hypofluorescence by mask effect due to exudates and macular early hyperfluorescence with late diffusion associated with small hyperfluorescent lesions in the RE. We suspected CNV type 2. Macular Spectral Domain optical coherence tomography (SD-OCT) showed significant retinal infiltration with pre-epithelial hyper-reflectivity bracing the diagnosis of type 2 CNV. In view of the importance of exudates and intra-retinal infiltration, we completed by indocyanine green angiography (ICGA) which showed hypercyanecent vascular dilations grouped in clusters of grapes relevant to an associated VPC. The patient received eight monthly intravitreal (IVT) injections of bevacizumab with good anatomical evolution. At 10 months, visual acuity was 1/10 with disappearance of exudates and retinal infiltration. CONCLUSION: Patients with AS should receive regular follow-up given the risk of CNV but also of VPC, especially in cases of PXE. Multimodal imaging is of great help and ICGA remains inescapable.

Severe early-onset manifestations of pseudoxanthoma elasticum resulting from the cumulative effects of several deleterious mutations in ENPP1, ABCC6 and HBB: transient improvement in ectopic calcification with sodium thiosulfate.

Pseudoxanthoma elasticum (PXE) is a rare disorder characterized by fragmentation and progressive calcification of elastic fibres in connective tissues. Overlap has been reported between the inherited PXE phenotype associated with ENPP1, ABCC6 or NT5E mutations and acquired PXE clinical manifestations associated with haemoglobinopathies induced by HBB mutations. No treatment is currently available for PXE. A young boy presented with severe early-onset systemic calcifications occurring in the skin as elastosis perforans serpiginosa (EPS) and in the arteries, causing mesenteric and limb ischaemia. Analyses revealed deleterious ABCC6, ENPP1 and HBB mutations. The diagnosis of severe PXE was retained and we have coined the term 'PXE+ syndrome' to describe the cumulative effects of the various mutations in this uncommon phenotype. Given the severity, rapid progression and a potentially fatal prognosis, intravenous sodium thiosulfate (STS) was initiated at 25 g three times weekly for 6 months. Numerous side-effects prompted dosage adjustment to 10 g intravenously daily. Treatment efficacy was evaluated at 6 months. Asthaenia, anorexia and pre-/postprandial pain had subsided, entailing weight gain. Abdominal EPS had diminished. Calcific stenosis of the coeliac and mesenteric arteries was no longer detectable on arterial ultrasonography. Follow-up revealed only transient efficacy of STS. Discontinuation of treatment to evaluate the persistence of effects resulted in relapse of the initial symptomatology after 4 months. STS efficacy is conceivably due to strong antioxidant properties and chelation of calcium to form soluble calcium thiosulfate complexes. This case is suggestive of PXE+ syndrome for which STS may represent potential treatment in severe cases. What's already known about this topic? Generalized arterial calcification of infancy may occur in association with ABCC6 mutations and pseudoxanthoma elasticum (PXE) can be linked to ENPP1 mutations. A PXE-like phenotype has also been reported in a subset of patients with inherited haemoglobinopathies, namely sickle cell disease or ß-thalassaemia, related to HBB mutations. To date, there is still no cure for PXE. What does this study add? We report a severe case of PXE resulting from the cumulative effects of several deleterious mutations in ENPP1, ABCC6 and HBB. We suggest the term 'PXE+ syndrome' to describe such patients. Sodium thiosulfate therapy could represent a potential option in severe cases of PXE+ syndrome.

[Angioid streaks in systemic disease]. / Szemfenéki angioid csíkok szisztémás betegségekben.

Angioid streaks are defined as the special morphological alteration of the fundus; the most common clinical manifestations are irregular, reddish brownish stripes around the optic nerve head or on the posterior pole. On the basis of histological examination, the cause of this phenomenon is the breaks and continuity deficiencies in the thin layer of Bruch membrane caused by the degeneration of elastic fibers. The aim of this study is to present the ocular complication of this rare entity through the description of three cases, and to draw attention to systemic diseases in the background. In our first and third cases, pseudoxanthoma elasticum (Grönblad-Strandberg syndrome) was in the background, while in our second case, hematological disease was confirmed. In our first and second cases, the ocular complication was the choroidal neovascularization, which we treated with intravitreal anti-VEGF injection. In our third case, the choroidal rupture was the ocular complication, caused by trauma. Angioid streaks on the fundus may be sub-phenomena of systemic diseases, the detection, differential diagnosis and treatment require interdisciplinary collaboration between associate physicians. Orv Hetil. 2019; 160(25): 994-1000.

Inhibition of Tissue-Nonspecific Alkaline Phosphatase Attenuates Ectopic Mineralization in the Abcc6-/- Mouse Model of PXE but Not in the Enpp1 Mutant Mouse Models of GACI.

Pseudoxanthoma elasticum (PXE), a prototype of heritable ectopic mineralization disorders, is caused by mutations in the ABCC6 gene encoding a putative efflux transporter ABCC6. It was recently shown that the absence of ABCC6-mediated adenosine triphosphate release from the liver and, consequently, reduced inorganic pyrophosphate levels underlie the pathogenesis of PXE. Given that tissue-nonspecific alkaline phosphatase (TNAP), encoded by ALPL, is the enzyme responsible for degrading inorganic pyrophosphate, we hypothesized that reducing TNAP levels either by genetic or pharmacological means would lead to amelioration of the ectopic mineralization phenotype in the Abcc6-/- mouse model of PXE. Thus, we bred Abcc6-/- mice to heterozygous Alpl+/- mice that display approximately 50% plasma TNAP activity. The Abcc6-/-Alpl+/- double-mutant mice showed 52% reduction of mineralization in the muzzle skin compared with the Abcc6-/-Alpl+/+ mice. Subsequently, oral administration of SBI-425, a small molecule inhibitor of TNAP, resulted in 61% reduction of plasma TNAP activity and 58% reduction of mineralization in the muzzle skin of Abcc6-/- mice. By contrast, SBI-425 treatment of Enpp1 mutant mice, another model of ectopic mineralization associated with reduced inorganic pyrophosphate, failed to reduce muzzle skin mineralization. These results suggest that inhibition of TNAP might provide a promising treatment strategy for PXE, a currently intractable disease.

Anti-VEGF treatment for choroidal neovascularization complicating pattern dystrophy-like deposit associated with pseudoxanthoma elasticum.

PURPOSE: To evaluate the efficacy of intravitreal anti-VEGF injections in choroidal neovascularization (CNV) related to pattern dystrophy-like deposit in pseudoxanthoma elasticum (PXE). METHODS: One-year prospective, interventional study. Nine eyes were recruited in the ophthalmology departments of San Raffaele University and University of Barcelona. Each patient underwent best corrected visual acuity (BCVA) measurement on ETDRS chart, slit-lamp biomicroscopy, fluorescein angiography (FA), indocyanine green angiography (ICGA), and optical coherence tomography (OCT). The protocol included a first anti-VEGF injection, followed by monthly evaluations with re-treatments based on new funduscopic hemorrhages, fluid on OCT or leakage on FA and/or ICGA. Primary outcome measures were the mean BCVA changes. Secondary outcomes included central macular thickness (CMT) variations and the number of injections needed. RESULTS: At month 12, mean BCVA significantly improved from 20/45 to 20/35 Snellen equivalent, with 3 eyes gaining at least 3 ETDRS lines. Mean CMT decreased from 297 ± 22 to 262 ± 13 µm, after 5.5 ± 4.0 injections. No leakage was observed at the end of follow-up. CONCLUSIONS: Intravitreal anti-VEGF injections represent an effective treatment for CNV related to pattern dystrophy-like deposit in PXE, with an improvement of BCVA and CMT. Mean injection number is in line with other studies performed in CNV secondary to angioid streaks.

Dietary Pyrophosphate Modulates Calcification in a Mouse Model of Pseudoxanthoma Elasticum: Implication for Treatment of Patients.

Pseudoxanthoma elasticum is a heritable disease caused by ABCC6 deficiency. Patients develop ectopic calcification in skin, eyes, and vascular tissues. ABCC6, primarily found in liver and kidneys, mediates the cellular efflux of ATP, which is rapidly converted into inorganic pyrophosphate (PPi), a potent inhibitor of calcification. Pseudoxanthoma elasticum patients and Abcc6-/- mice display reduced PPi levels in plasma and peripheral tissues. Pseudoxanthoma elasticum is currently incurable, although some palliative treatments exist. In recent years, we have successfully developed therapeutic methodologies to compensate the PPi deficit in animal models and humans. Here, we inadvertently discovered that modulating dietary PPi can also be an effective approach to reducing calcification in Abcc6-/- mice. Our findings were prompted by a change in institutional rodent diet. The new chow was enriched in PPi, which increased plasma PPi, and significantly reduced mineralization in Abcc6-/- mice. We also found that dietary PPi is readily absorbed in humans. Our results suggest that the consumption of food naturally or artificially enriched in PPi represents a possible intervention to mitigate calcification progression in pseudoxanthoma elasticum, that dietary preferences of patients may explain pseudoxanthoma elasticum heterogeneous manifestations, and that animal chow has the potential to influence data reproducibility.

Inherited Arterial Calcification Syndromes: Etiologies and Treatment Concepts.

PURPOSE OF REVIEW: We give an update on the etiology and potential treatment options of rare inherited monogenic disorders associated with arterial calcification and calcific cardiac valve disease. RECENT FINDINGS: Genetic studies of rare inherited syndromes have identified key regulators of ectopic calcification. Based on the pathogenic principles causing the diseases, these can be classified into three groups: (1) disorders of an increased extracellular inorganic phosphate/inorganic pyrophosphate ratio (generalized arterial calcification of infancy, pseudoxanthoma elasticum, arterial calcification and distal joint calcification, progeria, idiopathic basal ganglia calcification, and hyperphosphatemic familial tumoral calcinosis; (2) interferonopathies (Singleton-Merten syndrome); and (3) others, including Keutel syndrome and Gaucher disease type IIIC. Although some of the identified causative mechanisms are not easy to target for treatment, it has become clear that a disturbed serum phosphate/pyrophosphate ratio is a major force triggering arterial and cardiac valve calcification. Further studies will focus on targeting the phosphate/pyrophosphate ratio to effectively prevent and treat these calcific disease phenotypes.

Ranibizumab for choroidal neovascularization secondary to pseudoxanthoma elasticum: 4-year results from the PIXEL study in France.

PURPOSE: To evaluate the long-term effectiveness and safety of ranibizumab 0.5 mg in patients with choroidal neovascularization (CNV) secondary to pseudoxanthoma elasticum (PXE) in a real-world setting. METHODS: A descriptive, observational, multicenter study in a retrospective and prospective cohort was conducted in France that included patients who had received at least one injection of ranibizumab 0.5 mg during the period October 2011 to October 2014, for CNV secondary to PXE. Eligible patients were identified by review of medical records or during routine consultations. The main objectives were to describe patient characteristics, assess changes in best-corrected visual acuity [VA, Early Treatment Diabetic Retinopathy Study (ETDRS) letters] over time, the number and reasons for ranibizumab treatment and overall safety. RESULTS: Of the 72 enrolled patients (98 eyes) from 23 centers, 39 (54.2%) were male and mean [±standard deviation (SD)] age was 59.6 (±8.3) years. The mean VA was 64.6 letters at the first ranibizumab injection, which was maintained at the 1-year follow-up (64.7 letters). Thereafter, the mean VA was stable until the 4-year follow-up. At 4 years, the proportion of eyes with VA gain of ≥15 letters was 3/19 (15.8%) and stable VA (change between -15 and +15 letters) was 10/19 (52.6%). Mean (±SD) annual number of ranibizumab injections was 4.1 (±4.0), lower in the second versus first year. The most common reason for ranibizumab treatment was progression of neovascular activity (42.9%). No deaths or new safety findings were reported. CONCLUSIONS: In patients with CNV secondary to PXE, ranibizumab 0.5 mg resulted in stable VA over 4 years with a limited number of injections. Safety findings were consistent with the established safety profile of ranibizumab.

Pseudoxanthoma Elasticum-Like Papillary Dermal Elastolysis: A Single Case Report.

BACKGROUND: Pseudoxanthoma elasticum-like papillary dermal elastolysis (PXE-PDE), a rare acquired elastolytic disorder, occurs in postmenopausal, elderly women and is characterized by soft, white-yellow papules that localize on the neck and supraclavicular regions and often coalesce into cobblestone plaques. It has no systemic involvement and is histologically distinct from the clinically similar inherited pseudoxanthoma elasticum. CASE SUMMARY: A 64-year-old Caucasian woman presented with a 2-year history of multiple, asymptomatic soft yellow 1- to 2-mm papules on her neck, which were increasing in number. On histopathology, haemotoxylin and eosin stain showed a normal-appearing papillary dermis; however, Verhoeff-van Gieson elastic stain showed absent elastic fibres in the papillary dermis. Papular elastorrhexis was suggested, but given its clinical picture, PXE-PDE was also considered. There was no resolution after 2 courses of intralesional triamcinolone acetonide (0.1 mL of 5 mg/mL). CONCLUSION: PXE-PDE, which is characterized by complete loss or significant reduction of elastic fibres in the papillary dermis, was consistent with our patient's presentation and histologic findings. Papular elastorrhexis, a paediatric cutaneous disorder, was initially considered, but clinicopathologic correlation led to a diagnosis of PXE-PDE. Intralesional corticosteroids was tried as a treatment but was ineffective at improving the condition. This report documents the importance of histopathology and clinicopathologic correlation when differentiating the overlapping variants of fibroelastolytic disease.

Functional Rescue of ABCC6 Deficiency by 4-Phenylbutyrate Therapy Reduces Dystrophic Calcification in Abcc6-/- Mice.

Soft-tissue calcification is associated with aging, common conditions such as diabetes or hypercholesterolemia, and with certain genetic disorders. ABCC6 is an efflux transporter primarily expressed in liver facilitating the release of adenosine triphosphate from hepatocytes. Within the liver vasculature, adenosine triphosphate is converted into pyrophosphate, a major inhibitor of ectopic calcification. ABCC6 mutations thus lead to reduced plasma pyrophosphate levels, resulting in the calcification disorder pseudoxanthoma elasticum and some cases of generalized arterial calcification of infancy. Most mutations in ABCC6 are missense, and many preserve transport activity but are retained intracellularly. We have previously shown that the chemical chaperone 4-phenylbutyrate (4-PBA) promotes the maturation of ABCC6 mutants to the plasma membrane. In a humanized mouse model of pseudoxanthoma elasticum, we investigated whether 4-PBA treatments could rescue the calcification inhibition potential of selected ABCC6 mutants. We used the dystrophic cardiac calcification phenotype of Abcc6-/- mice as an indicator of ABCC6 function to quantify the effect of 4-PBA on human ABCC6 mutants transiently expressed in the liver. We showed that 4-PBA administrations restored the physiological function of ABCC6 mutants, resulting in enhanced calcification inhibition. This study identifies 4-PBA treatment as a promising strategy for allele-specific therapy of ABCC6-associated calcification disorders.

Pseudoxanthoma elasticum.

Pseudoxanthoma elasticum (PXE) is characterized by elastic tissue fragmentation and calcification. The deterioration of elastic fibers leads to characteristic yellowish papules and plaques (pseudoxanthomas) and retinal angioid streaks. Although these findings may begin in childhood, the diagnosis is typically not made until the second or third decade after the skin and retinal findings become more prominent. Cerebrovascular complications include brain infarction due to narrowing and occlusion of cerebral arteries and aneurysm formation. Intracranial hemorrhage can occur in the absence of aneurysm, and gastrointestinal hemorrhage is common. Peripheral arterial vascular disease can lead to intermittent leg claudication. A skin biopsy often demonstrates calcified elastic fibers, even in a mildly affected area of skin. The inheritance is autosomal recessive, although heterozygotes may exhibit some features of the disease. PXE is due to mutation of the ABCC6 gene on chromosome 16. There is no treatment, but certain lifestyle modifications may limit the complications. The potential for retinal hemorrhage has led to recommendations for limitations of contact sports or other activities that might facilitate eye trauma. Other recommendations include maintaining a normal lipid profile, avoidance of aspirin and nonsteroidal anti-inflammatory agents, and limiting dietary calcium intake.

Zebrafish enpp1 mutants exhibit pathological mineralization, mimicking features of generalized arterial calcification of infancy (GACI) and pseudoxanthoma elasticum (PXE).

In recent years it has become clear that, mechanistically, biomineralization is a process that has to be actively inhibited as a default state. This inhibition must be released in a rigidly controlled manner in order for mineralization to occur in skeletal elements and teeth. A central aspect of this concept is the tightly controlled balance between phosphate, a constituent of the biomineral hydroxyapatite, and pyrophosphate, a physiochemical inhibitor of mineralization. Here, we provide a detailed analysis of a zebrafish mutant, dragonfish (dgf), which is mutant for ectonucleoside pyrophosphatase/phosphodiesterase 1 (Enpp1), a protein that is crucial for supplying extracellular pyrophosphate. Generalized arterial calcification of infancy (GACI) is a fatal human disease, and the majority of cases are thought to be caused by mutations in ENPP1. Furthermore, some cases of pseudoxanthoma elasticum (PXE) have recently been linked to ENPP1. Similar to humans, we show here that zebrafish enpp1 mutants can develop ectopic calcifications in a variety of soft tissues - most notably in the skin, cartilage elements, the heart, intracranial space and the notochord sheet. Using transgenic reporter lines, we demonstrate that ectopic mineralizations in these tissues occur independently of the expression of typical osteoblast or cartilage markers. Intriguingly, we detect cells expressing the osteoclast markers Trap and CathepsinK at sites of ectopic calcification at time points when osteoclasts are not yet present in wild-type siblings. Treatment with the bisphosphonate etidronate rescues aspects of the dgf phenotype, and we detected deregulated expression of genes that are involved in phosphate homeostasis and mineralization, such as fgf23, npt2a, entpd5 and spp1 (also known as osteopontin). Employing a UAS-GalFF approach, we show that forced expression of enpp1 in blood vessels or the floorplate of mutant embryos is sufficient to rescue the notochord mineralization phenotype. This indicates that enpp1 can exert its function in tissues that are remote from its site of expression.

An atypical case of choroidal neovascularization associated with pseudoxanthoma elasticum treated with intravitreal bevacizumab: a case report.

BACKGROUND: Pseudoxanthoma elasticum is an inherited disorder that is associated with accumulation of pathologic elastic fibers in the skin, vascular walls and Bruch's membrane in the eye. Choroidal neovascularization is one of the most common causes of acute vision loss in these patients. We report an atypical case of suspected choroidal neovascularization associated with pseudoxanthoma elasticum. CASE PRESENTATION: A 47-year-old Caucasian woman with pseudoxanthoma elasticum and angioid streaks was referred because of decreased and distorted vision in her right eye of one week's duration. Visual acuity was 6/12 in the right eye and 6/6 in the left eye. Fundus examination revealed angioid streaks and white intraretinal macular deposits bilaterally. Fluorescein angiography did not reveal any obvious leakage in the right eye while optical coherence tomography revealed subretinal fluid associated with an adjacent intraretinal hyperreflective structure. Autofluoresence imaging showed focal areas of increased autofluorescence corresponding to the deposits in both eyes. Over the following year the patient underwent five intravitreal injections of bevacizumab (Genentech/Roche,US) in the right eye, which resulted in visual acuity improving to 6/9 with regression of the hyperreflective structrure and complete resolution of subretinal fluid. CONCLUSIONS: Traditionally, fluorescein angiography is effective in the detection of choroidal neovascularization in patients with pseudoxanthoma elasticum. In our case, optical coherence tomography revealed subretinal fluid and an adjacent hyperreflective structure while fluorescein angiography did not reveal any obvious leakage. The sole presence of subretinal fluid does not necessarily imply the presence of choroidal neovascularization and certainly retinal pigment epithelium dysfunction could also explain subretinal fluid in these patients. However, the complete absorption of the fluid and the disappearance of the previously evident hyperreflective structure following treatment, led us to suspect choroidal neovascularization as the primary cause of the above findings. The poor natural course of choroidal neovascularization in these patients increases the importance of early detection and should result in the adaptation of a low-threshold strategy concerning the initiation of treatment.

Atorvastatin counteracts aberrant soft tissue mineralization in a mouse model of pseudoxanthoma elasticum (Abcc6⁻/⁻).

UNLABELLED: Pseudoxanthoma elasticum (PXE), a multisystem heritable disorder with aberrant mineralization of arterial blood vessels, is caused by mutations in the ABCC6 gene. Previous studies have suggested that carriers of the ABCC6 mutations, particularly of p.R1141X, are at increased risk for coronary artery disease. In this study, we used Abcc6 (tm1Jfk) knock-out mice to determine the serum lipid profiles and examine the effects of atorvastatin on the aberrant mineralization in this model of PXE. First, serum lipid profiles at 12 weeks of age, after overnight fasting, revealed a statistically significant increase in total cholesterol and triglyceride levels in Abcc6 (tm1Jfk) mice compared to their wild-type littermates. Placing these mice at 4 weeks of age for 20 weeks on atorvastatin, either 0.01 % or 0.04 % of the diet (low statin and high statin groups, respectively), reduced the total triglyceride and cholesterol levels, which was accompanied with significantly reduced mineralization of the dermal sheath of vibrissae, a biomarker of the aberrant mineralization process in these mice. However, if the mice were placed on atorvastatin for 12 weeks at 12 weeks of age, at which time point significant mineralization had already taken place, no difference in the amount of mineralization was noted. These observations suggest that statins, particularly atorvastatin, can prevent, but not reverse, aberrant mineralization in this mouse model of PXE. For a clinical perspective, a survey of 1,747 patients with PXE was conducted regarding their present or past use of statins. The results indicated that about one third of all PXE patients are currently or have previously been on cholesterol-lowering drugs. Thus, a sizable number of patients with PXE could be subject to modulation of their mineralization processes by concomitant statin treatment. KEY MESSAGE: The Abcc6 (-/-) mice serve as a model system for PXE, an ectopic mineralization disorder Abcc6 (-/-) mice were shown to have elevated serum cholesterol and triglyceride levels Feeding of the Abcc6 (-/-) mice with atorvastatin prevented connective tissue mineralization A third of patients with PXE was found to be on cholesterol-lowering therapy Atorvastatin may potentially be beneficial for patients with PXE.