Aberrant Water Structure Dynamics in B16 Melanoma-Bearing Mice by Time Domain Refractometry Analysis

Living bodies comprise approximately 55-75% water to maintain homeostasis. However, little is known about the comprehensive differences in in vivo water molecule dynamics (water structure dynamics; WSD) between physiological and pathophysiological statuses. Here, we examined the WSD of ex vivo tumor tissues and organs from tumor-bearing mice with engrafted mouse malignant melanoma cells (B16-F10) in the right flanks to compare with those in healthy mice, using time domain reflectometry of dielectric spectroscopy at days 9, 11, and 14 after engrafting. The relaxation parameters of relaxation time (τ), relaxation time distribution parameter (β), and relaxation strength (∆ε) were measured on tumor tissues and lung, liver, kidney, and skin tissues. Immediately afterward, the water contents (%) in the tumor and the other organs were calculated by measuring their weights before and after freeze-drying. Each parameter of the tumor was compared to that of pooled values of other organs in tumor-bearing (TO) and healthy mice (HO). The tumor water content temporarily increased compared to that of HO at day 11; the tumor volume was also prone to increase. In contrast, tumor tissues exhibited significantly higher values of β close to 1 of ultrapure water and ∆ε compared to TO and HO at all times. Moreover, β in the viscera of TO was prone to increase compared to that of HO with significantly higher levels at day 11. Conclusively, tumor-bearing mice exhibited systemically aberrant WSD, unlike healthy mice. Thus, dielectric spectroscopy in terms of WSD may provide novel pathophysiological perspectives in tumor-bearing living bodies.

Gut lumen formation defect can cause intestinal atresia: evidence from histological studies of human embryos and intestinal atresia septum

Intestinal atresia (IA), a common cause of neonatal intestinal obstruction, is a developmental defect, which disrupts the luminal continuity of the intestine. Here, we investigated (i) the process of lumen formation in human embryos; and (ii) how a defective lumen formation led to IA. We performed histological and histochemical study on 6-10 gestation week human embryos and on IA septal regions. To investigate the topology of embryonic intestine development, we conducted 3D reconstruction. We showed that a 6-7th gestation week embryonic gut has no lumen, but filled with mesenchyme cells and vacuoles of a monolayer of epithelial cells. A narrow gut lumen was formed by gestation week-9, the gut was filled with numerous vacuoles of different sizes, some vacuoles were merging with the developing embryonic gut wall. At gestation week-10, a prominent lumen was developed, only few vacuoles were present and were merging with the intestine wall. At IA septal regions, vacuoles were located in the submucous layer, covered by a single layer of epithelium without glandular structure, and surrounded with fibrous tissue. The mucosal epithelium was developed with lamina propria and basement membrane, but the submucosa and the longitudinal smooth muscle layers were not properly developed. Hence, the vacuoles in IA septum could represent a remnant of vacuoles of embryonic gut. In conclusion, the fusion of vacuoles with the developing intestine wall associates with the disappearance of vacuoles and gut lumen formation in human embryos, and perturbation of these developmental events could lead to IA.

Online monitoring of hiPSC expansion and hepatic differentiation in 3D culture by dielectric spectroscopy

Hepatocyte-like cells derived from human-induced pluripotent stem cells (hiPSC-HLC) are expected to have important applications in drug screening and regenerative medicine. However, hiPSC-HLC are difficult to produce on a large-scale to obtain relevant numbers for such applications. The aim of this study was to implement a novel integrated strategy for scalable production of hiPSC-HLC and demonstrate the applicability of dielectric spectroscopy to monitor hiPSC expansion/differentiation processes. We cultured hiPSC as three-dimensional (3D) aggregates in stirred-tank bioreactors (STB) operated in perfusion with an in situ capacitance probe. Dissolved oxygen concentration and dilution rate were controlled along the process and after 5 days of cell expansion, the hepatic differentiation was integrated in sequential steps for 28 days. The hiPSC were able to grow as 3D aggregates and the expression of hepatic markers and albumin production after differentiation confirmed that hepatocyte differentiation improved when compared to 2D culture. These hiPSC-HLC exhibited functional characteristics of hepatocytes including glycogen storage and drug metabolization capacity. Our results also show a good correlation between the cell permittivity measured online and the aggregate biovolume measured by standard offline methods, demonstrating for the first time the potential of dielectric spectroscopy to monitor hiPSC expansion and differentiation in STB.

Electrical Impedance Measurements of Biological Cells in Response to External Stimuli

Dielectric spectroscopy (DS) is a noninvasive technique for real-time measurements of the impedance spectra of biological cells. DS enables characterization of cellular dielectric properties such as membrane capacitance and cytoplasmic conductivity. We have developed a lab-on-a-chip device that uses an electro-activated microwells array for capturing, DS measurements, and unloading of biological cells. Impedance measurements were conducted at 0.2 V in the 10 kHz to 40 MHz range with 6 s time resolution. An equivalent circuit model was developed to extract the cell membrane capacitance and cell cytoplasmic conductivity from the impedance spectra. A human prostate cancer cell line, PC-3, was used to evaluate the device performance. Suspension of PC-3 cells in low conductivity buffers (LCB) enhanced their dielectrophoretic trapping and impedance response. We report the time course of the variations in dielectric properties of PC-3 cells suspended in LCB and their response to sudden pH change from a pH of 7.3 to a pH of 5.8. Importantly, we demonstrated that our device enabled real-time measurements of dielectric properties of live cancer cells and allowed the assessment of the cellular response to variations in buffer conductivity and pH. These data support further development of this device toward single cell measurements.