Clemson University

Department of Chemical & Biomolecular Engineering

Expansion of mesenchymal stem cells in atmospheric carbon dioxide — bioreactor control implications

Dr. Sarah Harcum

Bioengineering Department

Clemson University

       Most current stem cell research is concentrated on determining the environment signals essential to steer an undifferentiated stem cell into the desired differentiated adult cell. In part due to the tremendous progress achieved in understanding differentia-tion, a major remaining engineering bottleneck limiting clinical and diagnostic application is our ability to culture large numbers of undifferentiated stem cell in industrial instrumented-stirred bioreactors. Stem cell culture development is ready to leverage and build upon the knowledge gained by the mammalian cell culture biotechnology industry. These past gains did not; nonetheless, address the fundamental issue of assessing cell metabolic health in real-time using common bioreactor sensors, including off-gas sensors. Oxygen and carbon dioxide off-gas measurements have advanced estimation and control methods for aerobic bioprocesses; however, encumbering the application of carbon dioxide off-gas sensor measurements for control of stem and mammalian cell cultures is the prevalence of bicarbonate buffered medium in mammalian cell culture systems. The bicarbonate buffering system – which relies upon an elevated CO2 environment – typically used to maintain pH in stem and mammalian cell cultures introduces several unnecessary limitations in bioreactor systems. Not only do artificially high dissolved CO2 levels negatively affect cell growth, but also more importantly, the need to sparge CO2 into the system complicates the ability to control culture parameters. This control is especially important for stem cells, whose behavior and phenotype is highly sensitive to changes in culture conditions such as dissolved oxygen and pH.  As a first step, we have developed a buffer to support expansion of mesenchymal stem cells (MSC) under an atmospheric CO2 environment in static cultures. MSC expanded under atmospheric CO2 with this buffer achieved equivalent growth rates without adaptation compared to those grown in standard conditions and also maintained a stem cell phenotype, self-renewal properties, and the ability to differentiate into multiple lineages after expansion. In parallel, we are developing state estimators that combine oxygen off-gas gas, stir speed, and dissolved oxygen measurements to predict the true oxygen transfer rate (OTR) in real-time without attenuation or delay. Oxygen sensing can be accomplished in a bicarbonate buffered medium; however, is intrinsically a less sensitive indicator of cell metabolism than carbon dioxide. Eventually, the overall goal of this project is to culture stems cell in a non-bicarbonate buffered medium where feeding is controlled using the carbon dioxide off-gas sensing as a component of an indicator of the cell metabolic state.

      Dr. Harcum has over 30 years of experience conducting Escherichia coli fermentations and over 20 years of cell culture experience.  She is trained in microbiology and molecular biology and has work both in the federal and industrial sections, in addition to academics.  Dr. Harcum’s cell culture research has included identification of tyrosine phosphorylation motifs in B-cells, gene expression analysis of genes controlling protein glycosylation in Chinese hamster ovary (CHO) cells, DNA microarray analysis of glycosylation genes in NS0 cells (a mouse myeloma cell line) and development of non-bicarbonate buffer media for stems cells. Additionally, Dr. Harcum has cultured several bacterial, yeast, and parasitic organisms in fermenters in collaboration Clemson and industrial researchers.  Her research group has analyzed gene expression changes via DNA microarrays for E. coli due to recombinant protein expression.  Her group reported that E. coli down-regulate protein synthesis and energy metabolism genes, while up-regulating prophage and flagella genes.  Dr. Harcum’s group recently published a dynamic gene expression comparison of E. coli expressing soluble and insoluble recombinant proteins.

      Dr. Harcum graduated from the University of Michigan with her BSE in Engineering Science – Bioengineering; Colorado State University with her MS in Chemical Engineering; and the University of Maryland, College Park with her PhD in Chemical Engineering.  She then joined the Food and Drug Administration where with reviewed monoclonal drug applications and conducted research in development immunology using cell culture and molecular biology techniques. Dr. Harcum took her first academic appointment at New Mexico State University in Chemical Engineering with a joint appointment in Molecular Biology.  She moved to Clemson University’s Department of Chemical Engineering before transferring to the Department of Bioengineering at Clemson.

Thursday, April 17, 2014 at 2:00pm to 3:00pm

Earle Hall, 100
206 S. Palmetto Blvd., Clemson, SC 29634

Notice of Non-Discrimination

Event Type

Seminars

Target Audience

General Public

Departments

College of Engineering, Computing and Applied Sciences, Chemical and Biomolecular Engineering

Contact Name:

Diana Stamey

Contact Phone:

864-656-1182

Contact Email:

short@clemson.edu

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