Effects of serum type on growth and permeability properties of cultured endothelial cells

Cell Line and Media Composition Influence the Production of Giant Plasma Membrane Vesicles

Giant plasma membrane vesicles (GPMVs) have been utilized as a model to study phase separation in the plasma membrane. Additionally, GPMVs have been employed as vehicle for delivering molecular cargo, including small molecule drugs and nanoparticles. Nearly all examples of GPMV production use a defined salt buffer that is a stark contrast to typical cell culture medium. In this study, we demonstrate that the addition of formaldehyde and dithiothreitol to a standard culture medium was capable of generating GPMVs at a concentration equal to or higher than the traditional production buffer. These methods were evaluated for two human cell lines: kidney endothelial and Schwann cells (SCs). Morphological properties of the resultant GPMVs exhibited no significant differences between the two formulations. Factors such as pH and seeding density significantly influenced the production of GPMVs in both mediums. The cell type and seeding density was shown to influence the number of GPMVs to the greatest extent. SCs yield more GPMVs at higher seeding densities compared to endothelial cells. Stability of the membrane of the GPMVs produced in both mediums was evaluated by monitoring passive diffusion of two fluorescently tagged dextrans (3 and 10 kDa). Regardless of the production formulation or cell type, approximately 85% GPMVs are impermeable to either dextran. Cold storage for on-demand use and shipping are essential for broader use of GPMVs. Toward this aim, we have evaluated the GMPV number and morphologies following storage at -80 °C and in liquid nitrogen. A significant loss of the GPMV number, ∼30%, was observed following storage across production formulations as well as cell types. Our results indicate that smaller GMPVs, <5 μm are more stable for preservation. In conclusion, GPMVs can be produced in a broad range of formulations, exhibit a high degree of stability, and can undergo cold storage for further adoption.

Serum factors mediate changes in mitochondrial bioenergetics associated with diet and exercise interventions

Mitochondrial improvements resulting from behavioral interventions, such as diet and exercise, are systemic and apparent across multiple tissues. Here, we test the hypothesis that factors present in serum, and therefore circulating throughout the body, can mediate changes in mitochondrial function in response to intervention. To investigate this, we used stored serum from a clinical trial comparing resistance training (RT) and RT plus caloric restriction (RT + CR) to examine effects of blood borne circulating factors on myoblasts in vitro. We report that exposure to dilute serum is sufficient to mediate bioenergetic benefits of these interventions. Additionally, serum-mediated bioenergetic changes can differentiate between interventions, recapitulate sex differences in bioenergetic responses, and is linked to improvements in physical function and inflammation. Using metabolomics, we identified circulating factors associated with changes in mitochondrial bioenergetics and the effects of interventions. This study provides new evidence that circulating factors play a role in the beneficial effects of interventions that improve healthspan among older adults. Understanding the factors that drive improvements in mitochondrial function is a key step towards predicting intervention outcomes and developing strategies to countermand systemic age-related bioenergetic decline.

Effect of different mitogens and serum concentration on HUVEC morphology and characteristics: implication on use of higher passage cells

Human umbilical vein endothelial cells (HUVEC) were cultured in two different media, viz. the commonly used M199 containing 20% fetal bovine serum (FBS) and endothelial cell growth factor and a defined media EGM-2 containing 2% FBS along with growth supplements in known concentrations. The purpose of this study was to determine the effect of different media on the growth potential and cell morphology in subsequent passages. We have established that a dual coating of gelatin and human fibronectin extracellular matrix provides optimal cell attachment. Growth rate for primary culture was almost double in defined media. For secondary culture a two fold higher proliferation rate was observed in defined EGM-2 media. Histological studies were done using phase contrast, confocal and scanning electron microscopy which showed that cells cultured in M199 started losing their morphological characteristic from 3rd passage and after 6th passage appeared to come in senescent stage, while in case of defined media there was no change observed in the cells up to 10th passage. A significant difference was found in the expression of soluble intracellular adhesion molecule-1 (sICAM-1) which is an endothelial cell marker on cells cultured in different media. Additionally it was observed that exposure duration to trypsin-EDTA during cell detachment also plays an important role in maintaining cell morphological characteristics. These results show that significant morphological changes appear in higher order passages if cells are grown in routine medium for a long time and therefore may not be suitable for cell signaling experiments.

Endothelial cell culture: protocol to obtain and cultivate human umbilical endothelial cells

Endothelial cells play a key role in prominent immunological and pathological processes such as leukocyte trafficking, inflammation, atheroma or cancer cell metastasis. Umbilical veins are probably the most widely used source for human endothelial cells, since they are more easily available than many other vessels, they are free from any pathological process and they are physiologically more relevant than many established cell lines. Here, we describe a standard protocol for preparation, maintenance and quality control of these cells.

Isolation and culture of capillary endothelial cells from the eel, Anguilla rostrata

There has been little development of endothelial cell cultures from vertebrates other than mammals. In this report the isolation of capillary endothelial cells from the rete mirabile of the eel, Anguilla rostrata, is described. The cells are isolated with collagenase H and dispase II. The cells are plated into fibronectin-hyaluronic acid coated flasks. The culture medium is M199 with Earle's salts supplemented with NaCl, HEPES, NaHCO(3), glutamine, pyruvate, heparin, antibiotics, endothelial cell growth supplement, and 20% serum. Cultures are incubated at 25 degrees C in humidified air. The rete mirabile contains pericytes in addition to endothelial cells. Variations in plating time, serum concentrations, and growth matrices were tried to separate the two cell types. The total number of endothelial cells and the ratio of endothelial cells to pericytes are the most important factors in obtaining pure cultures of capillary endothelial cells. Endothelial cells are isolated also from the endocardium, bulbus arteriosus, and large vessels. The initial isolates usually take 3-6 weeks to grow to confluence with subcultures taking about 2 weeks to confluence.

Mechanism of endothelium-dependent relaxation induced by thrombin in the pig coronary artery

The mechanism of thrombin-induced endothelium-dependent relaxation was investigated using fura-2 front-surface fluorometry. Thrombin induced an endothelium-dependent relaxation during U46619-induced contractions in pig coronary arterial strips. The relaxation consisted of two components: the early phasic component with a transient decrease in [Ca2+]i of smooth muscle and the subsequent sustained tonic component without [Ca2+]i decrease. The phasic relaxation was inhibited by a combination of N(omega)-nitro-L-arginine and K+-depolarization, while the tonic component was inhibited by either indomethacin or K+-depolarization. Thrombin induced a transient [Ca2+]i increase and nitric oxide (NO) production in pig aortic valvular endothelial cells, which expressed NO synthase as determined by reverse transcription and polymerase chain reaction. Thus, it was concluded that NO and hyperpolarizing factor were involved in the phasic component of thrombin-induced relaxation and that hyperpolarizing factor and prostacyclin were involved in the tonic component.

Serum-free media for culturing and serial-passaging of adult human retinal pigment epithelium

The ability of a chemically-defined serum-free culture medium to support the attachment, growth and serial passaging of primary adult human retinal pigment epithelial (RPE) cells was studied. Primary cultures of adult human RPE were established in a chemically-defined serum-free culture medium on both bare or bovine corneal endothelial extracellular matrix-coated tissue-culture plastic. Confluent cells were serially passaged in chemically-defined serum-free culture medium three times by trypsinization, and trypsin activity was quenched with aprotinin. First passage RPE cells were plated onto tissue-culture plastic precoated with bovine corneal endothelial extracellular matrix or uncoated tissue-culture plastic in 24 well plates at a density of 50 viable cells mm-2. Cells were maintained either in chemically-defined serum-free culture medium, DMEM without serum, or DMEM with 15% fetal bovine serum. For each medium plating, efficiencies were determined 24 hours after plating, and growth rates were determined on the first, third and seventh days after plating. Morphometric image analysis was performed on cells cultured for up to 6 weeks and three serial passages. Seeding efficiency on bovine corneal endothelial extracellular matrix-coated tissue-culture plastic and treated tissue-culture plastic were higher for chemically-defined serum-free culture medium (88.9+/-2.7% and 47.1+/-4.1%, respectively) and DMEM with serum (87.2+/-5.6% and 52.9+/-10.5%, respectively) than DMEM without serum (59.2+/-5.6% and 33.1+/-6.9%, respectively; P<0.01). The RPE proliferation rate in chemically-defined serum-free culture medium was comparable to DMEM with serum on both substrates within the first 3 days, although cells in DMEM with serum had a higher proliferation rate on day 7. Cells cultured in DMEM without serum, eventually decreased in number. RPE maintained in chemically-defined serum-free culture medium maintained a consistent proliferation rate, reached confluence, and retained an epitheloid morphology on either extracellular matrix or tissue-culture plastic for up to 6 weeks and three serial passages. Primary RPE reached confluence at 12+/-3 days on bovine corneal endothelial extracellular matrix-coated tissue-culture plastic and 21+/-5 days on treated tissue-culture plastic. Confluent cultures were composed of small hexagonal cells with epitheloid morphology on both substrates. We concluded that primary adult human RPE can be cultured in this chemically-defined serum-free culture medium. RPE will proliferate, reach confluence, retain their epitheloid morphology and can be serially passaged in the absence of serum.

Growth requirements of endothelial cells in culture: variations in serum and amino acid concentrations

Endothelial cell growth in vitro is limited to the availability of nutrients from commercially available media and added serum. Nutrients, such as amino acids, are chiefly derived from the cell culture medium, rather than from added serum, and optimal endothelial cell growth may be dependent on amino acid levels in the culture media. To test this hypothesis, porcine pulmonary artery-derived endothelial cells were exposed to culture medium 199 (M199), amino acid-deficient M199 (dM199), as well as dM199 supplemented with amino acids. Cell protein was similar in cells cultured for 3 d in M199 supplemented with 1, 3, 5 or 10% bovine calf serum, respectively. Addition of amino acid solutions (L-amino acids [Laa], DL-amino acids [DLaa], 2Laa, or Laa+glutamine) to dM199 demonstrated a cell dependence for optimal growth on the type of amino acids as well as on the total available nitrogen in the media. Compared with M199, dM199 supplemented with Laa only partially supported long-term growth of endothelial cells in culture. On the other hand, dM199 supplemented with either 2Laa, DLaa, or Laa+ glutamine was superior over M199 with regard to endothelial cell growth. The addition of Laa+glutamine to dM199 was most growth-supporting, with an increase of over 2.6-fold in total cell protein compared with cells cultured with M199. These results suggest that, in addition to the presence of essential amino acids, total available nitrogen in culture media may be a critical factor for optimal endothelial cell growth.

Sensitivity of G-protein involved in endothelin-1-induced Ca2+ influx to pertussis toxin in porcine endothelial cells in situ

1. We designed a new method to determine quantitatively the intracellular Ca2+ concentration ([Ca2+]i) in endothelial cells in situ, using front-surface fluorometry and fura-2-loaded porcine aortic valvular strips. Using this method, we investigated the characteristics of the G-protein involved in endothelin-1 (ET-1)-induced changes in [Ca2+]i of endothelial cells in situ. 2. Endothelial cells were identified by specific uptake of acetylated-low density lipoprotein labelled with 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine perchlorate (DiI-Ac-LDL). Double staining with DiI-Ac-LDL and fura-2 showed that the valvular strip was covered with a monolayer of endothelial cells and that the cellular component which contributed to the fura-2 fluorescence, [Ca2+]i signal, was exclusively endothelial cells. 3. ET-1 (10(-7) M) induced an elevation of [Ca2+]i consisting of two components: the first was a rapid and transient elevation to reach a peak, followed by a second, sustained elevation (the second phase). The first phase was composed of extracellular Ca(2+)-independent and -dependent components, while the second phase was exclusively extracellular Ca(2+)-dependent. The extracellular Ca(2+)-independent component of the first phase was due to the release of Ca2+ from intracellular storage sites. The second phase and part of the first phase of [Ca2+]i elevation were attributed to the influx of extracellular Ca2+. The Ca2+ influx component was completely inhibited by 10(-3) M Ni2+ but was not affected by 10(-5) M diltiazem. 4. Pertussis toxin (IAP) markedly inhibited the extracellular Ca2+-dependent elevation of [Ca2+]j, but had no effect on the extracellular Ca2+-independent elevation of [Ca2+], caused by ET-1 (10-7M).5. Bradykinin (10-7 M) or ATP (10- 5M) elevated [Ca2+]i and these responses also consisted of extracellular Ca2+-independent and extracellular Ca2+-dependent components. IAP had no effect on either component of the [Ca2+]i elevation induced by bradykinin or ATP.6. From these findings we conclude that, in porcine endotheliel cells in situ, ET-1 elevates [Ca2+]i as are result of a Ca2+ influx component from the extracellular space and release of intracelluarly stored Ca2+ .The Ca2+ influx is regulated by an IAP-sensitive G-protein, while the release of Ca2+ from the intracellular store is not.

Drug transport across the blood-brain barrier. II. Experimental techniques to study drug transport

This is part II of a review on the transport of drugs across the blood-brain barrier. In this part, the emphasis is on the various experimental techniques that can be used to characterize the blood-brain barrier transport of drugs. Generally speaking, three approaches can be distinguished: in vitro techniques using isolated brain capillaries, cerebrovascular endothelial cells in primary culture or endothelium-derived cell lines; in vivo techniques (both single-passage and multi-passage techniques) and in situ perfusion techniques. Each of these techniques has specific advantages and disadvantages associated with it. Therefore, in many instances, a combination of different approaches is needed to study the fundamental aspects of drug transport across the blood-brain barrier.

The cerebral microvessels in culture, an update

Recent advances in our knowledge of the blood-brain barrier (BBB) have in part been made by studying the properties and function of cerebral endothelial cells in vitro. After an era of working with a fraction, enriched in cerebral microvessels by centrifugation, the next generation of in vitro BBB model systems was introduced, when the conditions for routinely culturing the endothelial cells were established. This review summarizes the results obtained from this rapidly growing field. It can be stated with certainty that, in addition to providing a better insight into the chemical composition of cerebral endothelial cells, much has been learned from these studies about the characteristics of transport processes and cell-to-cell interactions during the last 12 years. With the application of new technologies, the approach offers a new means of investigation, applicable not only to biochemistry and physiology but also to the drug research, and may improve the transport of substances through the BBB. The in vitro approach has been and should remain an excellent model of the BBB to help unravel the complex molecular interactions underlying and regulating the permeability of the cerebral endothelium.

Endothelin induces the Ca(2+)-transient in endothelial cells in situ

Using front-surface fluorometry of fura-2 and valvular strips of the pig aorta, we recorded changes in the cytosolic Ca2+ concentration, [Ca2+]i, of endothelial cells in situ, quantitatively, and investigated the effects of endothelin-1 and -3 on these endothelial cells. Both endothelin-1 and -3 elevated [Ca2+]i of a peak (the first phase) and sustained type. This first phase is considered to be due to a release of Ca2+ from intracellular storage sites. The sustained phase depended on extracellular Ca2+ and is considered to be due to an influx of Ca2+ through the plasma membrane. At equimolar concentrations, the peak elevations of [Ca2+]i induced by endothelin-1 were much higher than those induced by endothelin-3. We suggest that, in endothelial cells in situ, endothelin-1 mobilizes stored Ca2+ and may activate Ca(2+)-sensitive pathways, including the release of prostacyclin and endothelium-derived relaxing factors, more potently than does endothelin-3.