Abigail Harris Becker

Thermo Fisher Scientific

CTS StemPro HSC expansion medium for cell and gene therapies

A major limitation in the ex vivo expansion of harvested human hematopoietic stem-progenitor cells (HSPCs) is the rapid differentiation of HSPCs at the expense of the most primitive pluripotent hematopoietic stem cells (HSCs). A culture system that expands both short-term progenitor cells and long-term repopulating HSCs could benefit translational research and clinical applications such as HSC transplantation and gene therapies. To address this challenge, we developed CTS StemPro HSC Expansion Medium, a xeno-free, serum-free medium designed with regulatory compliance in mind.  Using a Design of Experiments approach, media constituents were systematically modified and each iteration was evaluated with the goal to maximize ex vivo expansion of hematopoietic stem-progenitor cell (HSPC) immunophenotypes.

CTS StemPro HSC Expansion Medium supplemented with FLT3L, SCF (also known as KITL), TPO, IL-3, and IL-6 (“FST36”) expands human CD34+ cells from mobilized peripheral blood, cord blood, and bone marrow. For example, primary human CD34+ cells from mobilized peripheral blood cultured for 7 days in FST36-containing CTS StemPro™ HSC Expansion Medium resulted in a ~100-fold increase in the number of CD34+CD45+Lin- cells and a ~2000-fold increase in the number of CD34+Lin-CD90+CD45RA- cells (an early HSPC immunophenotype), compared to uncultured cells. Expanded CD34+ cells maintained key hematopoietic stem cell characteristics including in vitro differentiation into erythroid and non-erythroid cell colonies and expression of high levels of aldehyde dehydrogenase. Importantly, in vivo transplantation studies indicate that the expanded CD34+ cells can engraft into the bone marrow of immuno-deficient mice. In addition, utilizing liposome-mediated electroporation to deliver Cas9 RNPs (500 ng 1.4 kb GFP), we observed indel rates of up to 60% and a knock-in rate of 10% in cultured CD34+ cells. Both cultured CD34+ cells and PBMCs demonstrated a high reprogramming efficiency (~0.3%) with the CytoTune-iPS Sendai Reprogramming Kit. We are enthusiastic to introduce CTS StemPro HSC Expansion Medium, which enables a complete xeno-free and serum-free workflow for the utilization of human CD34+ cells in gene and cell therapies.


Abigail completed her Master’s Degree in Biomedical Sciences at Penn State College of Medicine in Hershey, PA, where her graduate research focused on the role of genetic and epigenetic alterations in Acute Myeloid Leukemia (AML).  Abigail joined Thermo Fisher Scientific in the Cell Biology business based in Frederick, MD in 2016 as an R&D Scientist. Abigail is part of a team focused on research and development of cell therapy-grade products that support translational and clinical research workflows. As part of this work Abigail has employed a range of research tools including formulation and assay development, verification and validation, technology transfer and statistical analyses. Other experience in the biotechnology field includes development of cell-based assays as well as micro-RNA detection and gene editing technologies.