BBB on chip: microfluidic platform to mechanically and biochemically modulate blood-brain barrier function.

The blood-brain barrier (BBB) is a unique feature of the human body, preserving brain homeostasis and preventing toxic substances to enter the brain. However, in various neurodegenerative diseases, the function of the BBB is disturbed. Mechanisms of the breakdown of the BBB are incompletely understood and therefore a realistic model of the BBB is essential. We present here the smallest model of the BBB yet, using a microfluidic chip, and the immortalized human brain endothelial cell line hCMEC/D3. Barrier function is modulated both mechanically, by exposure to fluid shear stress, and biochemically, by stimulation with tumor necrosis factor alpha (TNF-α), in one single device. The device has integrated electrodes to analyze barrier tightness by measuring the transendothelial electrical resistance (TEER). We demonstrate that hCMEC/D3 cells could be cultured in the microfluidic device up to 7 days, and that these cultures showed comparable TEER values with the well-established Transwell assay, with an average (± SEM) of 36.9 Ω.cm(2) (± 0.9 Ω.cm(2)) and 28.2 Ω.cm(2) (± 1.3 Ω.cm(2)) respectively. Moreover, hCMEC/D3 cells on chip expressed the tight junction protein Zonula Occludens-1 (ZO-1) at day 4. Furthermore, shear stress positively influenced barrier tightness and increased TEER values with a factor 3, up to 120 Ω.cm(2). Subsequent addition of TNF-α decreased the TEER with a factor of 10, down to 12 Ω.cm(2). This realistic microfluidic platform of the BBB is very well suited to study barrier function in detail and evaluate drug passage to finally gain more insight into the treatment of neurodegenerative diseases.

Effects of fulvestrant alone or combined with different steroids in human breast cancer cells in vitro.

OBJECTIVES: Fulvestrant is an estrogen receptor (ER) antagonist that binds, blocks and degrades the estrogen receptor and is currently used in adjuvant treatment in postmenopausal women with ER-positive breast cancer as an alternative for tamoxifen. As an antagonist, it may induce or aggravate climacteric symptoms. In order to alleviate these symptoms, one could consider hormone therapy. The objective of this study was to analyze the effect of fulvestrant alone or in combination with different steroids in human breast cancer cells in vitro, and to demonstrate whether these steroids will compromise the efficacy of fulvestrant in ER-positive breast cancer cells. METHODS: We performed experiments in vitro with various hormone therapy preparations (estradiol (E2), dihydrodydrogesterone (DHD) and tibolone) at a concentration of 10(-6) mol/l alone or combined with fulvestrant in different breast cancer cell lines, ER-positive and ER-negative. After an incubation of 144 h, proliferation and apoptosis were measured. The first was measured by quantification of the expression of cyclin D1 mRNA, the latter by the Nicoletti fragmentation assay. RESULTS: This in vitro study revealed clear differences in results when various hormone therapy preparations, alone or combined with fulvestrant, are added to ER-positive and ER-negative breast cancer cell lines. CONCLUSIONS: Our study demonstrated that fulvestrant, an ER antagonist used in the treatment of ER-positive breast cancer, combined with E2 and DHD or in combination with tibolone, is not compromised in its efficacy in inducing apoptosis in ER-positive breast cancer cell lines in vitro.

Differential effects of bisphosphonates on breast cancer cell lines.

Bisphosphonates may induce direct anti-tumor effects in breast cancer cells in vitro. In this study, six bisphosphonates were administered to three breast cancer cell lines. Cell proliferation was measured by quantification of the expression of Cyclin D1 mRNA. Apoptosis was determined by flow cytometry of a DNA fragmentation assay. We demonstrated that bisphosphonates have direct effects on cell proliferation and apoptosis in different breast cancer cell lines. However, not all bisphosphonates act equally on breast cancer cells in vitro. Zoledronate seems to be the most potent of the six bisphosphonates. This in vitro study showed that bisphosphonates possess promising anti-tumor potential.

Apoptosis induced kinetic changes in autofluorescence of cultured HL60 cells-possible application for single cell analysis on chip.

INTRODUCTION: This paper presents a new method using natural cellular fluorescence (autofluorescence, AF) to study apoptosis. Measurement of AF reduces sample preparation time and avoids cellular toxicity due to the fact that no labelling is required. METHODS: Human promyelocytic leukemic HL60 cells were incubated with camptothecin (CPT), tumour necrosis factor (TNF)-alpha in combination with cycloheximide (CHX), or irradiated with 6 or 10 Gray, during varying time periods, to initiate apoptosis. AF was measured at the flow cytometer. RESULTS: Induction of apoptosis results in the shrinkage of the cell and the fragmentation into apoptotic bodies. With flow cytometry, 4 subpopulations, viable, early apoptotic, late apoptotic and the necrotic cells, can be distinguished. Induction of apoptosis results in a decrease in AF intensity compared to untreated HL60 cells, especially seen in the late apoptotic subpopulation. The AF intensity is found to decrease significantly in time (between 2 h and 24 h) for all the four apoptotic inducers used. CONCLUSIONS: Our results show that it is possible to specifically measure the apoptotic-induced kinetic changes in AF in HL60 cells. A decrease in AF intensity is seen from 2 h till 24 h. These results open a door for future developments in single-cell analysis.

Apoptotic cell death kinetics in vitro depend on the cell types and the inducers used.

INTRODUCTION: In vitro exposure of cells to a fluorochrome-labeled inhibitor of caspases (FLICA) labels cells after caspase activation and arrests further progress of apoptotic cell death. The labeled apoptotic cells can be quantified in relation to time of apoptosis induction with flow cytometry. Loss of membrane integrity (late apoptosis and cell death) was measured with exposure to propidium iodide (PI). From the labeling patterns with FLICA and PI the apoptotic cell death kinetics was calculated. METHODS: HL60 cells and human umbilical vein endothelial cells (HUVECs) were incubated in the presence of the fluorescent inhibitor of caspases, FAM-VAD-FMK (20 mM, FLICA) for up to 48 h. Apoptosis was induced by Camptothecin (CPT, 0.15 microM) or by a mixture of tumour necrosis factor alpha (TNF-alpha, 3 nM)-Cycloheximide (CHX, 50 microM). Samples were counterstained with PI. RESULTS: Incubation of HL60 cells with CPT induced apoptosis in 92% of cells within the first 18 h at a rate of 5% per hour while incubation with TNF-alpha/CHX resulted in apoptosis in 76% of the cells within the first 6 h at a rate of 12% per hour. Incubation of HUVECs with TNF-alpha/CHX induced apoptosis in 65% of the cells within the first 18 h at a rate of 3.7% per hour during the first 6 h of the incubation. During incubation with TNF-alpha/CHX the remaining viable HL60 cells and HUVECs entered apoptosis within 48 h at an approximate rate of 0.2 per hour. However, on the road of the cell death, HL60 cells showed a transit from the viable (FLICA-/PI-) to early (FLICA+/PI-) and further to late apoptotic phase (FLICA+/PI+), while HUVECs entered directly from the viable to the late apoptotic stage. CONCLUSION: Apoptotic turnover rate depends on the stimulus used to induce apoptosis, while the type of the cell determines the way of the transition within the apoptotic cascade.