Critical location of cell viability loss during the cell injection process in hepatocyte transplantation using a rectangular microchannel model

Abstract

A sufficient number of functional live hepatocytes delivered to a recipient is necessary for cell therapy. Preventing cell viability loss during the cell injection process is important to improve the clinical outcomes of hepatocyte transplantation. The critical location of cell viability loss is important to identify the causal relationship between the viability loss and cell injection process. In this study, the critical location of cell viability loss was determined experimentally in a rectangular microchannel by microscopic high-speed camera observations. Live hepatocyte distributions were investigated upstream and downstream, and measured on three planes, top, center, and bottom, under horizontally or vertically supplied conditions of the syringe orientation. Sedimented and uniform dispersion conditions of the live hepatocyte distribution at upstream of the microchannel were classified according to observations at horizontal and vertical syringe orientations, respectively. Higher hepatocyte viability loss was found under the sedimented condition. The results suggested that the critical location of hepatocyte viability loss was on the bottom plane of the microchannel. Furthermore, physical causes of the hepatocyte viability loss were found by micro-scale observations of the cell velocity and diameter during the cell injection process. This information may contribute to development of a guideline for the cell injection process to improve hepatocyte transplantation.

A linear shear model of cell viability loss during hepatocyte transplantation

“…Cell death occurred after a loss of membrane integrity in the loose gap (50 µm), when the cell first increased in size, then shrank when not limited by friction from the parallel plate boundaries under loose gap conditions. The deformation ratios for live and dead cells under condition D were in good agreement with the deformation ratio of cells flowing on the bottom of a microchannel, observed at upstream and downstream locations (Sufiandi et al, 2017). The cell shrinkage occurred between 0 to 10 seconds (zone 1), and expansion occurred between 10 seconds to 40 seconds (zone 2), as shown in Fig.…”

“…Using a flow rate 1 mL/min (Sufiandi et al, 2015) these have velocities, shear rates, and shear stress 25 µm from catheter wall, respectively, (2.0 mm/s, 80 1/s, 0.1 Pa), (6.2 mm/s, 248 1/s, 0.3 Pa), (9.6 mm/s, 384 1/s, 0.5 Pa), (13.9 mm/s, 556 1/s, 0.7 Pa) and (23.9 mm/s, 1.3 1/s, 956Pa). On the other hand, the velocity, shear rate, and shear stress in the microchannel experiment at 25 µm from the bottom of the microchannel was (8.8 mm/s, 352 1/s, 0.5 Pa) (Sufiandi et al, 2015;Sufiandi et al, 2017). The velocities, shear rate, and shear stress in this study was (2.0 mm/s, 78 1/s, 0.1 Pa) (1.5 mm/s, 61 1/s, 0.1 Pa) (9.7 mm/s, 388 1/s, 0.52 Pa) (9.7 mm/s, 388 1/s, 0.52 Pa), respectively, for conditions A, B, C, and D. Therefore, the…”

“…This was compared with a horizontal syringe orientation (Sufiandi et al, 2017). The results showed the effects of the syringe orientation on the distribution of live cells at the upstream positions of the microchannel.…”

“…The animals were given standard rat chow and water ad libitum until used for isolation. Hepatocyte isolation was performed as in previous works (Hsu et al, 2013;Sufiandi et al, 2015;Yasuda et al, 2015;Sufiandi et al, 2017).…”

“…Condition D models the viability loss in a microchannel (Sufiandi et al, 2017) with 100% more separation (50 µm) and a higher shear rate (388 1/s). The number of surviving cells in condition D decreased with increasing exposure time, as shown in Fig.…”