Jacobs Journal of Regenerative Medicine

Culture Expansion Increases Lineage Heterogeneity in ELA® Cells: Implications for the Biomanufacturing of Adult Tissue Stem Cell-Based Therapies

*Keith D. Crawford
Department Of Orthopedic Surgery, Brigham And Women’s Hospital, Harvard Medical School, Boston, United States

*Corresponding Author:
Keith D. Crawford
Department Of Orthopedic Surgery, Brigham And Women’s Hospital, Harvard Medical School, Boston, United States
Email:crawford@asclepiuslabs.com

Published on: 2018-04-14

Abstract

Previously, we described a population of early lineage adult (ELA®) stem cells isolated from the synovial fluid (SF) of patients with osteoarthritis. These adult stem cells expressed elevated mRNA levels for cardiac-, pancreatic-, and neuronal-specific transcripts. In addition, the ELA ® cells were observed to have superior immunosuppressive capabilities to those of mesenchymal stem cells (MSC). The objective of this study was to evaluate the properties of ELA® cells that are relevant to future expansion and biomanufacture for clinical applications. Our first aim was to identify a putative surface marker present on the uncommitted ELA® cell population that does not undergo significant changes during culturing and can therefore be used to detect and monitor ELA® cells during culture and expansion. The second aim was to define the extent of differentiation and immunomodulatory variability that occurs between cell donors and with increasing passaging. To accomplish these aims, we used data generated through global transcriptome analysis in conjunction with computational analysis tools and online databases. We identified CD99 as a potential candidate marker for the monitoring of ELA® cells. CD99 was constitutively and uniformly expressed under low serum culture conditions in the expanding cell population and was a more reliable marker than the SH2 (CD105) or SH3/ SH4 (CD73) antigens, which are currently used to identify MSCs. ELA® cells differentiated into osteogenic, adipogenic and chondrogenic tissues, and quantitative analysis revealed significant variation between cells from different donors and across subsequent tissue culture passages. Such variation was not evident for the immunosuppressive effects of ELA cells, which correlated more closely with ELA® cell numbers. Our findings demonstrate that expression of CD99 did not correlate with functional attributes of the ELA cell population and therefore could serve as a more reliable marker for monitoring ELA cell culture and expansion efficiency. Our observations demonstrate a proclivity for donor-to-donor, individual, and functional heterogeneity amongst ELA® cell populations that could impact clinical biomanufacturing and therapeutic potency.

Keywords

Osteoarthritis; Synovial fluid; Adult Stem Cells (ASCs); Early Lineage Adult (ELA®) stem cells; Heterogeneity; Lineage priming and differentiation; Global transcriptome analysis; CD99

Introduction

Over the past 65 years, significant progress has been made in the field of stem cell biology and regenerative medicine. However, there still exist critical gaps in our understanding of lineage heterogeneity at the population level and how this may impact basic research findings and clinical outcomes. It is commonly accepted that stem cells from different sources are considered to be a homogenous population with comparable functions. Regardless of whether the stem cells are derived from bone marrow or fat, the isolation, culture media and culture expansion are considered to have similar dynamic and functional effects. It is our hypothesis that stark dynamic and functional differences exist, even when controlled for origin, culture expansion conditions, and method of detection/isolation.