Microcarrier-based clinical-grade manufacturing of therapeutic Wharton's jelly mesenchymal stromal cells

Due to their immunomodulatory and anti-inflammatory properties, tissue repair capabilities and regenerative potential, Wharton's jelly mesenchymal stem/stromal cells (WJMSCs) have been widely investigated as potential treatment for diverse clinical indications. WJMSCs have been found to be well-tolerated and safe, positioning them as a promising candidate for cellular therapy. To address the commercial need for manufacturing WJMSCs for clinical applications, the production scale should be capable of generating large quantities of cells that retain their expected identity, purity and potency. This study aimed to establish a current Good Manufacturing Practice (cGMP) compliant robust and scalable expansion process representing a critical step towards a cGMP-compliant large-scale production platform for WJMSC-based clinical applications. Using our in-house cGMP-manufactured WJMSCs, which are currently being tested in a Phase Ib clinical trial (NCT03158896) using two-dimensional (2D) planar systems, we optimized various culture parameters including type of microcarrier, seeding density, agitation and culture feed regime in a 3D microcarrier-based culture system in spinner flasks. The results showed that cell adhesion was potentiated under intermittent stirring (3 min of agitation at 25 rpm followed by a period of non-agitation for 30 min), with reduced supplementation (0.05%) during the initial 8 h of cultivation with an initial cell concentration of 0.45 × 10⁵ cells/mL. Microcarrier-based WJMSC expansion in spinner flasks achieved greater cell densities of 1.67 × 10⁶ cells/mL with a maximum of 37-fold expansion, yielding ∼84 × 10⁶ cells after 6 days of culture with a 95% harvest efficiency. Additionally, post 3D expansion, WJMSCs maintained their phenotypic characteristics, differentiation potential, normal karyotype, functional properties and sterility in the culture systems evaluated. This cGMP-compliant expansion process described herein demonstrates a successful transition of an established 2D planar culture process of clinical grade WJMSCs to 3D microcarrier-based suspension process generating higher cell yields, is cost-effective and represents an important step toward fulfilling the commercial demand of clinical grade mesenchymal stromal cells.