Optimizing normoxic conditions in liver devices using enhanced gel matrices

Abstract

For in vitro liver replacement devices, such as packed bed bioreactors, to maintain the essential functions of the liver, they must at least successfully support hepatocytes, the parenchymal cell of the liver. In vivo, the liver is a major consumer of oxygen. Hence it is unsurprising that the limited transport distance of oxygen (O(2)) governs the dimensions of the cellular space of engineered devices. Because cellular space capacity directly affects the device's performance, O(2) transport is a critical issue in the scale up of bioreactor designs. In the current investigation, the microporosity of the extracellular matrix (ECM) has been modified to further improve O(2) transport in packed bed devices beyond that previously reported in the literature. These improvements to the O(2) enhancement technique enabled O(2) transport distances of 481.7 +/- 12.5 microm to be achieved under acellular conditions; and distances of 418.1 +/- 6.0 microm to be attained in the presence of 1 million hepatocytes. Both values are significantly greater than the 170 microm baseline attained when 10(6) hepatocytes are packed within normal non-enhanced ECM gels. The study's results also illustrate that the O(2) enhancement technique has the added benefit of preventing regions of severe hypoxia and hyperoxia from developing within the cellular space. As such, enhanced ECM gels enable packed hepatocytes to maintain better hepatocellular metabolic status than is possible with normal non-enhanced gels.

Use of perfluorocarbons to enhance the performance of perfused three‐dimensional hepatic cultures

“…More specifically, this work shows that the beneficial effects of 5% (v/v) PFC on the O 2 capacity of nutrient medium has effectively reduced the cells' glucose uptake, improved their proliferation and enhanced their net CYP450 activity performance when cultured under flow conditions. The benefits of enhanced O 2 availability on the functional performance of primary hepatocytes have been previously reported by our group 9,51,52 and others, 13,21,53 while the benefits of having PFCs incorporated into hepatic systems was also demonstrated by human cell line-based studies. 18,21,54 The current study is focused on addressing two questions: (1) how does this PTBCH-based PFC affect the O 2 capacity of the perfusate; and (2) are the use of PFCs in the perfusate a reasonable approach for supporting 3D cultures able to achieve strong functional performance.…”

The Effectiveness of a Novel Cartridge-Based Bioreactor Design in Supporting Liver Cells

“…The bioreactor has the additional benefit of employing a cellular space (i.e., its cartridge design) that is unique in that it offers the flexibility to easily support any anchorage-dependant cell type. It can also be modified to incorporate modifications proven to further improve functional output (e.g., O 2 transport enhancements [38][39][40] and micropatterned cocultures 27,28 ). The cartridge design also enables cells of the bioreactor to interact with the circulating medium through both of the membrane surfaces of each individual cartridge.…”

Overcoming hypoxia to improve tissue-engineering approaches to regenerative medicine

“…Indeed, short‐term culture of rat hepatocytes resulted in reduced cell viability when cultured at atmospheric p O 2 (21%) and at hyperbaric levels (~28%) than when cultured at sub‐atmospheric oxygen level (~12.6% O 2 ) (Suleiman and Stevens, ). Similar concerns regarding cell culture at hyperbaric oxygen tensions have been noted in other work (Niu et al ., ; O'Driscoll et al ., ). However, the effects of hyperbaric oxygen in cell culture for the cellular population of tissue engineering scaffolds are not always clear.…”

“…Systemic hyperbaric oxygen treatment is generally regarded as a therapeutic advantage for wound healing in chronically hypoxic wounds (Rollins et al, 2006;Calhoun et al, 2002). Nonetheless, exposure of cells in culture to hyperbaric oxygen is potentially hazardous, due to the increased production of harmful oxygen radicals (Niu et al, 2008;Suleiman and Stevens, 1987). Indeed, short-term culture of rat hepatocytes resulted in reduced cell viability when cultured at atmospheric pO 2 (21%) and at hyperbaric levels (~28%) than when cultured at sub-atmospheric oxygen level (~12.6% O 2 ) (Suleiman and Stevens, 1987).…”