The stabilizing effect of glucocorticoids on human endothelial cells in culture

Forward programming of human induced pluripotent stem cells via the ETS variant transcription factor 2: rapid, reproducible, and cost-effective generation of highly enriched, functional endothelial cells

AIMS

Endothelial cell (EC) dysfunction plays a key role in the initiation and progression of cardiovascular disease. However, studying these disorders in ECs from patients is challenging; hence, the use of human induced pluripotent stem cells (hiPSCs) and their in vitro differentiation into ECs represents a very promising approach. Still, the generation of hiPSC-derived ECs (hECs) remains demanding as a cocktail of growth factors and an intermediate purification step are required for hEC enrichment. Therefore, we probed the utility of a forward programming approach using transgenic hiPSC lines.

METHODS AND RESULTS

We have used the transgenic hiPSC line PGP1 ETV2 isoform 2 to explore the in vitro differentiation of hECs via doxycycline-dependent induction of the ETS variant transcription factor 2 (ETV2) and compared these with a standard differentiation protocol for hECs using non-transgenic control hiPSCs. The transgenic hECs were highly enriched without an intermediate purification step and expressed-as non-transgenic hECs and human umbilical vein endothelial cells-characteristic EC markers. The viability and yield of transgenic hECs were strongly improved by applying EC growth medium during differentiation. This protocol was successfully applied in two more transgenic hiPSC lines yielding reproducible results with low line-to-line variability. Transgenic hECs displayed typical functional properties, such as tube formation and LDL uptake, and a more mature phenotype than non-transgenic hECs. Transgenic hiPSCs preferentially differentiated into the arterial lineage; this was further enhanced by adding a high concentration of vascular endothelial growth factor to the medium. We also demonstrate that complexing lentivirus with magnetic nanoparticles and application of a magnetic field enables efficient transduction of transgenic hECs.

CONCLUSION

We have established a highly efficient, cost-effective, and reproducible differentiation protocol for the generation of functional hECs via forward programming. The transgenic hECs can be genetically modified and are a powerful tool for disease modelling, tissue engineering, and translational purposes.

Biochemistry of HELLP syndrome

The HELLP syndrome is a serious complication of pregnancy characterized by hemolysis (H), elevated liver (EL) enzymes, and low platelet (LP) count that occurs in 0.2-0.6% of all pregnancies and in 10-20% of cases with severe preeclampsia and frequently leads to adverse maternal and perinatal outcome. The exact pathobiology of HELLP syndrome has not been clearly defined. As it is considered a form or a complication of severe preeclampsia, it likely has its origin in aberrant placental development and function resulting in ischemia-producing oxidative stress. However, there is still a debate on whether HELLP must be considered a severe form of preeclampsia or a separate disease entity. It can be described as a placenta-induced disease, as is preeclampsia itself, but with a more acute and predominant inflammatory process typically targeting the liver and with a greater activation of the coagulation system. This occurs during a disordered immunologic process and may be due to a genetic predisposition. In this review, we discuss the main biochemical characteristics of HELLP syndrome, particularly focusing on molecular aspects of placental involvement and maternal systemic responses.

Is there a diurnal pattern in the clinical symptoms of HELLP syndrome?

OBJECTIVE

To determine if there is a diurnal pattern in the clinical symptoms of HELLP (Hemolysis, Elevated Liver enzymes, Low Platelets) syndrome.

STUDY DESIGN

A retrospective study was performed in 134 pregnancies complicated by HELLP syndrome. The medical records were reviewed to describe each HELLP episode. Time of day was divided into three periods, day, evening, and night. The following parameters were categorized according to the time of day: onset of symptoms, consultation by the doctor, initial blood sampling, diagnosis and decrease of symptoms. Biochemical parameters at clinical presentation and consecutive changes within 24 h were recorded.

RESULTS

In 65 pregnancies 77 HELLP episodes were well documented. Times of onset of symptoms and consultation by the doctor were significantly higher during the evening and night (p < 0.001), whereas times of diagnosis and decrease of symptoms occurred significantly more during the day (p < 0.001). In only 49.3% of the cases were diagnostic laboratory criteria met at clinical presentation. This was mainly due to platelet values in excess of 100 x 10(9)/l. Several hours later (median 8 h, range 2-23) the decrease in platelets occurred.

CONCLUSIONS

A diurnal pattern exists in the clinical symptoms of HELLP syndrome that is characterized by an exacerbation during the night and recovery during the day. There is a considerable delay between the onset of symptoms and the fulfillment of diagnostic laboratory criteria.

A randomised placebo-controlled trial of prolonged prednisolone administration to patients with HELLP syndrome remote from term

OBJECTIVES

To evaluate the effect of prolonged administration of high-dose prednisolone on early onset HELLP (hemolysis, elevated liver enzymes, and low platelets) syndrome during expectant management.

STUDY DESIGN

A randomized, double-blind trial was performed in 31 pregnant women with HELLP syndrome with an onset before 30 weeks gestation. Patients received either 50mg prednisolone or placebo intravenously twice a day. Primary outcome measures were the entry-to-delivery interval and the number of recurrent HELLP exacerbations in the antepartum period.

RESULTS

Serious maternal morbidity was considerable, in particular in the placebo group where even on maternal occurred as a consequence of liver rupture. The mean entry-delivery interval did not differ between the prednisolone group (6.9 days) and the placebo group (8.0 days). However, patients in the prednisolone group had a significant lower risk of a recurrent HELLP exacerbation after the initial crisis had subsided, as compared to patients in the placebo group (HR 0.3, with 95% CI 0.3-0.9). Platelet count recovered faster in the prednisolone group as compared to the placebo group (mean 1.7 days versus 6.2 days, P<0.01).

CONCLUSIONS

HELLP syndrome remote from term causes high risk for serious maternal morbidity and mortality. When expectant management is pursued in selected patients with a HELLP syndrome remote from term, prolonged administration of prednisolone reduces the risk of recurrent HELLP syndrome exacerbations.

Corticosteroids, pregnancy, and HELLP syndrome: a review

Corticosteroids are potent antiinflammatory and immunosuppressive drugs, which are used in the treatment of a wide range of medical disorders. During pregnancy, several corticosteroids are administered for maternal as well as fetal reasons. Prednisone and prednisolone show limited transplacental passage and are thus used for treatment of maternal disease. Dexamethasone and betamethasone, drugs that can easily cross the placenta, are more suitable for fetal indications. During the last decade, administration of corticosteroids was introduced in the treatment of hemolysis, elevated liver enzymes, and low platelets (HELLP syndrome), a severe form of preeclampsia unique to human pregnancy. Several randomized, controlled trials as well as other prospective and retrospective studies have been performed to investigate this beneficial effect of corticosteroids on biochemical measures and clinical signs. This review discusses the characteristics of corticosteroids in humans and details the use of corticosteroids during pregnancy. A review of literature on the effect of corticosteroids on HELLP syndrome is given and possible mechanisms of action are discussed.

Effect of thalidomide, octreotide, and prednisolone on the migration and proliferation of RPE cells in vitro

PURPOSE

The retinal pigment epithelium (RPE) is involved in the pathogenesis of age-related macular degeneration. The purpose of this study was to assess the effect of thalidomide, octreotide, and prednisolone on the proliferation and migration of bovine RPE cells in vitro.

METHODS

The migration assay was performed in double-chamber-wells separated by a membrane filter with 8 microm pores. Cells were allowed to migrate vertically for 7 hr, afterwards the cells on both filtersides were fixed, stained, and the migrated cells were counted. To examine RPE proliferation, bovine RPE cells were seeded subconfluently followed by an incubation with octreotide, thalidomide or prednisolone in a concentration gradient for 24 hr. Stimulation or inhibition of DNA synthesis was measured by [(3)H]-thymidine incorporation. Statistical analysis was performed with the paired student's t-test.

RESULTS

Statistically significant (p < 0.05) inhibition of RPE cell proliferation was measured for thalidomide at a concentration of 10-50 microg/ml, for octreotide at a concentration of 5 x 10(-4) and 5 x 10(-5) M, and for prednisolone at a concentration of 250 and 500 microg/ml as compared to the negative control. RPE cell migration was significantly (p < 0.05) inhibited by thalidomide at a concentration of 10 microg/ml, by octreotide at a concentration of 5 x 10(-5) M, and also by prednisolone at a concentration of 500 microg/ml as compared to the negative control.

CONCLUSIONS

Although the main effect of thalidomide, octreotide, and prednisolone when treating patients with choroidal neovascular membranes is probably related to the inhibition of angiogenesis it should be kept in mind that these substances may additionally inhibit RPE proliferation and migration.

Dexamethasone reduces oxygen induced retinopathy in a mouse model

Dexamethasone is widely used in the postnatal period. Its impact on retinopathy of prematurity (ROP) is extremely controversial; published studies have found a detrimental, protective, or no effect on ROP. The goal of this study was to test the hypothesis that use of dexamethasone during the injury phase (oxygen exposure) reduces the severity of oxygen-induced retinopathy (OIR) in a mouse model. C57BL6 mice pups were exposed to either room air or hyperoxia (75% FiO2) from postnatal d 7 through 12 (PN7-12) with or without dexamethasone (0.5 mg/kg/d s.c.) and killed on PN17-21. Retinopathy was assessed by a scoring system of retinal flat mount preparations and periodic acid-Schiff (PAS) staining of retinal sections. Pups exposed to dexamethasone and oxygen had a lower median retinopathy score of 5 (4, 6) [median (25th, 75th quartile)] compared with animals exposed to oxygen alone with median score of 9 (6, 10) with p < 0.001. PAS staining for extra retinal neovascularization in the dexamethasone and oxygen treated animals showed a significant reduction in number of nuclei extending beyond the inner limiting membrane when compared with oxygen exposed alone (p = 0.04). Animals treated with dexamethasone had decreased weight gain compared with control animals. Dexamethasone did not appear to affect the normal development of retinal vasculature as assessed by the scoring system when compared with control animals. Thus, dexamethasone decreases severity of OIR without having an adverse effect on normal retinal vascular development in the mouse model. We speculate that dexamethasone decreases the injury response that occurs during the hyperoxic phase, thus protecting the developing vasculature and improving the subsequent retinopathy.

Expression of small extracellular chondroitin/dermatan sulfate proteoglycans is differentially regulated in human endothelial cells

We have examined the expression of the small extracellular chondroitin/dermatan sulfate proteoglycans (CS/DS PGs), biglycan, decorin, and PG-100, which is the proteoglycan form of colony stimulating factor-1, in the human endothelial cell line EA.hy 926. We have also examined whether modulation of the phenotype of EA.hy 926 cells by tumor necrosis factor-alpha (TNF-alpha) is associated with specific changes in the synthesis of these PGs. We demonstrate that EA.hy 926 cells, when they form monolayer cultures typical of macrovascular endothelial cells, express and synthesize detectable amounts of biglycan and PG-100, but not decorin. On SDS-polyacrylamide gel electrophoresis both PGs behave like proteins of the relative molecular weight of approximately 250,000. TNF-alpha that changed the morphology of the cells from a polygonal shape into a spindle shape and that also stimulated the detachment of the cells from culture dish, markedly decreased the net synthesis of biglycan, whereas the net synthesis of PG-100 was increased. These changes were parallel with those observed at the mRNA level of the corresponding PGs. The proportions of the different sulfated CS/DS disaccharide units of PGs were not affected by TNF-alpha. Several other growth factors/cytokines, such as interferon-gamma, fibroblast growth factors-2 (FGF-2) and -7 (FGF-7), interleukin-1beta, and transforming growth factor-beta, unlike TNF-alpha, modulated neither the morphology nor the biglycan expression of EA.hy 926 cells under the conditions used in the experiments. However, PG-100 expression was increased also in response to FGF-2 and -7 and transforming growth factor-beta. None of the above cytokines, including TNF-alpha, was able to induce decorin expression in the cells. Our results indicate that the regulatory elements controlling the expression of the small extracellular CS/DS PGs in human endothelial cells are different.

Anti-tumor and anti-angiogenic effects in mice of heparin conjugated to angiostatic steroids

Heparin-steroid conjugates have been prepared by linking a non-anti-coagulating derivative of heparin, which binds to endothelial cells, to an angiostatic steroid, which suppresses endothelial cell division. One such conjugate, heparin adipic hydrazide (HAH) linked to cortisol, has previously been shown to inhibit both angiogenesis and the growth of solid tumors in mice. In the present study, heparin hydrazide (HH) was linked to tetrahydro S, tetrahydrocortisone and tetrahydrocortisol, which are devoid of glucocorticoid and mineralocorticoid activity and hence were predicted to have low toxicity to animals. The tetrahydro steroid conjugates were compared with the cortisol conjugate for therapeutic effectiveness against solid Lewis lung carcinoma growing in mice. HAH-cortisol reduced tumor growth by up to 75% whereas a simple mixture of HAH and cortisol was not significantly inhibitory. In contrast to HAH-cortisol, the 3 tetrahydro steroid conjugates did not significantly inhibit tumor growth. The differences in anti-tumor properties of the conjugates correlated with their ability to inhibit angiogenesis in a Matrigel implant model in mice. The tetrahydro steroid conjugates did not significantly inhibit angiogenesis whereas HAH-cortisol inhibited angiogenesis by greater than 90%. Therefore, HAH-cortisol is the most effective heparin-steroid conjugate so far developed.