A human platelet lysate-based culture supplement for the successful isolation and scalable expansion of umbilical cord matrix-derived mesenchymal stem/stromal cells

Abstract

Umbilical cord matrix (UCM)-derived mesenchymal stem/stromal cells (MSC) are considered promising therapeutic agents. However, low cell yields per UC unit and high cell doses required in clinical settings emphasize the need for ex vivo expansion of UCM MSC. We recently demonstrated the ability to isolate and ex-vivo expand UCM MSC under serum-/xeno-free culture conditions using static systems.1 Also, we have previously established a xeno-free microcarrier-based system for the scalable expansion of human MSC from bone marrow and adipose tissue, using plastic microcarriers and a commercially available xeno-free medium formulation.2-3 However, the scalable expansion of UCM MSC under dynamic conditions, using plastic microcarriers combined with different commercially available serum-/xeno-free media, remains challenging. Here, we demonstrate the ability of using a human platelet lysate (HPL)-based culture supplement (UltraGROTM, HELIOS BioScience Inc.) for the successful isolation and scalable expansion of UCM MSC. MSC-like cells were isolated from UCM explant cultures after 11±2 days and upon 5 passages cells retained their immunophenotype and multilineage differentiation potential. In addition, UCM MSC expanded using UltraGROTM-supplemented medium expanded faster compared to cells expanded using the previously established protocol (1.0 vs. 0.54 day-1, respectively)1. Importantly, UCM MSC were successfully expanded under dynamic conditions on plastic microcarriers using UltraGROTM-supplemented medium in spinner flasks. Upon an initial 42-60% cell adhesion to the beads, UCM MSC were able to expand by >10 fold after 4-5 days. Upon dynamic culture, cells maintained their immunophenotype and multilineage differentiation ability. To our knowledge, this is the first study reporting the successful UCM MSC expansion in a fully scalable xeno-free microcarrier-based system, representing an important advance to obtain safer and clinically meaningful MSC numbers for Cell Therapy.