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1. Development and Optimization of a Novel Centrifugal Bioreactor with a Real-Time Monitoring Sensor for T Cell Exhaustion with Applications in Cancer Immunotherapy

   Brenden Fraser-Hevlin, Kitana M. (November 2021, Annual meeting American Institute of Chemical Engineers)

   Cancer has been one of the most significant and critical challenges in the field of medicine. It is a leading cause of death both in the United States and worldwide. Common cancer treatments such as radiation and chemotherapy can be effective in destroying cancerous tissue but cause many detrimental side effects. Thus, recent years have seen new treatment methods that do not harm healthy tissue, including immunotherapy. Adoptive cell therapy (ACT) is one form of immunotherapy in which patients’ immune cells are modified to target cancer cells and then reintroduced into the body. ACT is promising, but most current treatments are inefficient and costly. Widespread implementation of ACT has been a difficult task due to the high treatment cost and inefficient methods currently used to expand the cells. Additionally, if the manufacturing process is not carefully controlled, it can result in the cells losing their cancer-killing ability after expansion. To address the need for an economically feasible culture process to expand immune cells for immunotherapy, our laboratory has designed a centrifugal bioreactor (CBR) expansion system. The CBR uses a balance of centrifugal forces and fluid forces, as shown in Figure 1, to quickly expand infected CD8+ T-cells from a bovine model up to high population densities. With other applications, the CBR has achieved cell densities as high as 1.8 x 108 cells/mL over 7 days in an 11.4-mL chamber. For this study, our goal is to begin validating the CBR by optimizing the growth of CEM (human lymphoblastic leukemia) cells, which are similar cell to cytotoxic T lymphocytes (CTLs). This can be accomplished by measuring kinetic growth parameters based on the concentrations of glucose and inhibitory metabolites in the culture. We hypothesize that by designing a kinetic model from static culture experiments, we can predict the parameters necessary to achieve peak CEM and eventually CTL growth in the CBR. We will report on kinetic growth studies in which different glucose concentrations are tested, and a maximum specific growth rate and Monod constant determined, as well as studies where varying levels of the inhibitory growth byproducts, lactate and ammonium, are added to the culture and critical inhibitor concentrations are determined. Another recent conceptual development for the design of the CBR is a real-time monitoring and feedback control system to regulate the cellular environment, based on levels of surface co-receptors and mRNA signaling within the culture. Prior studies have pinpointed T cell exhaustion as a significant issue in achieving successful immunotherapy, particularly in treatments for solid tumors; T cell exhaustion occurs during a period of chronic antigen stimulation when the cells lose their ability to target and kill cancer cells, currently theorized to be associated with particular inhibitory receptors and cytokines in the immune system. Designing a system with a fiber optic sensor that can monitor the cell state and use feedback control to regulate the pathways involved in producing these receptors will ensure the cells maintain cytotoxic properties during the expansion process within a Centrifugal Fluidized Expansion we call the CentriFLEX. In this presentation, we will also report on early results from development of this exhaustion monitoring system. In brief, achieving optimal kinetic models for the CBR system and methods to prevent T cell exhaustion has the potential to significantly enhance culture efficiency and availability of immunotherapy treatments. 

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2. Optimizing Cytotoxic T Cell Growth in a Centrifugal Bioreactor through Kinetic Growth Models

   Kitana Kaiphanliam, Brenden Fraser-Hevlin (November 2021, Annual meeting American Institute of Chemical Engineers)

   Cancer is the second leading cause of death globally and remains a significant issue in medicine. Immunotherapy treatments such as Chimeric Antigen Receptor T cell (CAR-T) therapies are becoming a more promising option because of their effectiveness in killing cancer cells without harming healthy tissue in the body. CAR-T therapies, however, are inaccessible to many due to the high cost—a result of inefficient cell expansion and manufacturing methods. To address this issue, we have developed the Centrifugal Fluidized Expansion (CentriFLEX) bioreactor that balances centrifugal and fluid forces, allowing the system to operate in perfusion and maintain a high cell density. Shown in past applications for similar cell types, the CentriFLEX can expand cultures up to 2.1 billion cells in an 11.4 mL chamber over the course of one week. Recently, we have used this system to expand bovine T cells as part of a collaboration with the College of Veterinary Medicine at Washington State University. Through the project, we conducted kinetic studies to model substrate consumption and metabolite production of bovine T cells and have enhanced the bioreactor design by making it more compact to fit entirely within a biosafety cabinet— mitigating contamination concerns. Current efforts have been spent determining the remaining parameters for the kinetic models and using such models to understand how the cells grow over time and in the space of a high-population density chamber. In this presentation, we will share how we use growth models that are based on a series of kinetic studies to predict substrate and metabolite levels over time in the bioreactor, allowing us to alter feed and dosing rates of medium and nutrients to maintain cell growth at the maximum specific growth rate. 

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3. Induced pluripotent stem cells can utilize lactate as a metabolic substrate to support proliferation

   https://doi.org/10.1002/btpr.3090  

   Odenwelder, Daniel_C; Lu, Xiaoming; Harcum, Sarah_W (November 2020, Biotechnology Progress)

   Abstract Human‐induced pluripotent stem cells (iPSCs) hold the promise to improve cell‐based therapies. Yet, to meet rising demands and become clinically impactful, sufficient high‐quality iPSCs in quantity must be generated, a task that exceeds current capabilities. In this study, K3 iPSCs cultures were examined using parallel‐labeling metabolic flux analysis (¹³C‐MFA) to quantify intracellular fluxes at relevant bioprocessing stages: glucose concentrations representative of initial media concentrations and high lactate concentrations representative of fed‐batch culture conditions, prior to and after bolus glucose feeds. The glucose and lactate concentrations are also representative of concentrations that might be encountered at different locations within 3D cell aggregates. Furthermore, a novel method was developed to allow the isotopic tracer [U‐¹³C₃] lactate to be used in the¹³C‐MFA model. The results indicated that high extracellular lactate concentrations decreased glucose consumption and lactate production, while glucose concentrations alone did not affect rates of aerobic glycolysis. Moreover, for the high lactate cultures, lactate was used as a metabolic substrate to support oxidative mitochondrial metabolism. These results demonstrate that iPSCs have metabolic flexibility and possess the capacity to metabolize lactate to support exponential growth, and that high lactate concentrations alone do not adversely impact iPSC proliferation. 

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4. The Differential Effects of Fluid Shear Stress on Mesenchymal Stem Cell Differentiation

   Robertson, T; Van_Wie, B; Driskell, R; Gozen, A; Bonassar, L; Thiessen, D; Dong, W; Schuler, A (October 2024, Biomedical Engineering Society)

   Introduction: Directing mesenchymal stem cell (MSC) chondrogenesis by bioreactor cultivation provides fundamental insight towards engineering healthy, robust articular cartilage (AC). The mechanical environment is represented by compression, fluid shear stress, hydrostatic pressure, and tension which collectively contribute to the distinct spatial organization of AC. Mimicking this cell niche is necessary for dictating cell growth, fate, and role. Researchers have shown that different mechanical stimulus types improve MSC chondrogenic commitment demonstrated by increases in key chondrogenic gene and protein markers. However, challenges remain in manufacturing spatially, anisotropic AC consisting of defined regions such as native tissue. Our strategy towards furthering this effort involves exposing MSC-laden alginate scaffolds in a multi-chambered, perfusion bioreactor with controlled fluid shear stress magnitudes to better mimic the native AC microenvironment leading to defined regions throughout the scaffold marked by varied cellular phenotypes. Validations made from assessing biochemical content, mRNA expression, western blot analysis, and cell viability will provide meaningful insight towards regulating MSC chondrogenesis. Methods: MSCs grown up to passage 4 were expanded to confluency in a T-175 flask then released from the surface using trypsin. Cells were stored in -80 ℃ freezer until experimentation. Our bioreactor system was sterilized by UV radiation for 4 hours then perfused with 70% ethanol overnight. Cell-laden scaffolds were prepared by first dissolving 1.5% alginate into deionized water. The polymeric solution was sterilely filtered and stored until usage. Cryopreserved MSCs were thawed and suspended in α-MEM medium containing essential supplements. Cells were counted and resuspended in alginate at a density of 106 cells/mL. The mixture was transferred to our multi-chambered bioreactor where they were allowed to crosslink in CaCl2 solution for 45 min. Separate scaffolds (N = 3) were molded within an identical reactor system and removed to serve as a control to compare effects of fluid shear stress on MSC differentiation. All, structures were washed with PBS then supplied with DMEM/F-12 medium containing 10% FBS, 1% penicillin/streptomycin , 1% L-glutamine, 100 nM dexamethasone, 50 µg/mL L-ascorbic acid, and10 ng/mL TGF-β3. The flowrate for the bioreactor was adjusted to 20 mL/min which provided desired fluid shear ranges of 2-87 mPa to stimulate the cells . Cell cultures were grown for 7 days, and medium changed every 3 days. Sectioned samples were analyzed for biochemical content, mRNA expression, and western blot to understand the impact of fluid shear stress magnitudes on MSC differentiation. Results: Directed fluid shear stress across a cell-laden alginate scaffold contained within an individual chamber in our bioreactor indicates varied cellular behavior within the superficial and deep regions of the construct marked by spatially secreted biochemical content as well as mRNA expression. This observation is supported by superficial MSCs stimulated by high and medium mechanical stimulation which indicates a 1.3 and 1.2-fold increase in total collagen production, respectively, when directly compared to cells deep in the construct. A similar effect is supported by total GAG secretion where high and medium shear stress across the fluid hydrogel interface yielded 1.2 and 1.3-fold upregulation of protein secretion, respectively, when observed under similar conditions. Perfused MSCs show upregulation to 3 and 20-fold for Sox9 and aggrecan, respectively, compared to a static culture. Shear ranges distributed throughout our cell-laden alginate scaffold correlates to differential chondrogenic commitment shown by variance of Sox9 expression when assessed by location and depth. Additional information on COL10A1 expression demonstrates mechanical stimulation that reduces hypertrophic cell differentiation contrary to a static culture. Discussion: In this investigation we emphasize that cells respond differently to mechanical stimulation when located in either the superficial or deep region of an alginate scaffold. This observation is supported by enhanced matrix production of chondrogenic protein for cells near the perfused fluid and hydrogel interface compared to deeper areas when stimulated by high and medium fluid shear loading regimes. Most importantly, maintenance of a healthy fluid shear gradient in our TBR provides evidence of promoting MSC chondrogenesis by spatially upregulating anabolic cartilage-like markers in addition to diminishing the onset of cell hypertrophy. Our efforts in monitoring mRNA expression of our samples reveals enhancement of chondrogenic cell differentiation for a perfused sample marked by increases in Sox9 and aggrecan genes; whereas a static sample stimulated only by TGF-β3 leads to undesirable expression of COL10A1. Key takeaways from our study support the contributions from previous researchers in recreating the native AC mechanical environment to encourage MSC differentiation. The development of our TBR system for controlled delivery of fluid shear stresses to MSCs furthers efforts in spatially guiding MSC chondrogenesis which is critical for engineering zonally differentiated AC. 

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5. Chemical inhibitors of hexokinase‐2 enzyme reduce lactate accumulation, alter glycosylation processing, and produce altered glycoforms in CHO cell cultures

   https://doi.org/10.1002/bit.28417  

   Naik, Harnish_Mukesh; Kumar, Swetha; Reddy, Jayanth_Venkatarama; Gonzalez, Jacqueline_E; McConnell, Brian_O; Dhara, Venkata_Gayatri; Wang, Tiexin; Yu, Marcella; Antoniewicz, Maciek_R; Betenbaugh, Michael_J (May 2023, Biotechnology and Bioengineering)

   Abstract Chinese hamster ovary (CHO) cells, predominant hosts for recombinant biotherapeutics production, generate lactate as a major glycolysis by‐product. High lactate levels adversely impact cell growth and productivity. The goal of this study was to reduce lactate in CHO cell cultures by adding chemical inhibitors to hexokinase‐2 (HK2), the enzyme catalyzing the conversion of glucose to glucose 6‐phosphate, and examine their impact on lactate accumulation, cell growth, protein titers, andN‐glycosylation. Five inhibitors of HK2 enzyme at different concentrations were evaluated, of which 2‐deoxy‐d‐glucose (2DG) and 5‐thio‐d‐glucose (5TG) successfully reduced lactate accumulation with only limited impacts on CHO cell growth. Individual 2DG and 5TG supplementation led to a 35%–45% decrease in peak lactate, while their combined supplementation resulted in a 60% decrease in peak lactate. Inhibitor supplementation led to at least 50% decrease in moles of lactate produced per mol of glucose consumed. Recombinant EPO‐Fc titers peaked earlier relative to the end of culture duration in supplemented cultures leading to at least 11% and as high as 32% increase in final EPO‐Fc titers. Asparagine, pyruvate, and serine consumption rates also increased in the exponential growth phase in 2DG and 5TG treated cultures, thus, rewiring central carbon metabolism due to low glycolytic fluxes.N‐glycan analysis of EPO‐Fc revealed an increase in high mannose glycans from 5% in control cultures to 25% and 37% in 2DG and 5TG‐supplemented cultures, respectively. Inhibitor supplementation also led to a decrease in bi‐, tri‐, and tetra‐antennary structures and up to 50% lower EPO‐Fc sialylation. Interestingly, addition of 2DG led to the incorporation of 2‐deoxy‐hexose (2DH) on EPO‐FcN‐glycans and addition of 5TG resulted in the first‐ever observedN‐glycan incorporation of 5‐thio‐hexose (5TH). Six percent to 23% ofN‐glycans included 5TH moieties, most likely 5‐thio‐mannose and/or 5‐thio‐galactose and/or possibly 5‐thio‐N‐acetylglucosamine, and 14%–33% ofN‐glycans included 2DH moieties, most likely 2‐deoxy‐mannose and/or 2‐deoxy‐galactose, for cultures treated with different concentrations of 5TG and 2DG, respectively. Our study is the first to evaluate the impact of these glucose analogs on CHO cell growth, protein production, cell metabolism,N‐glycosylation processing, and formation of alternative glycoforms. 

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