Culture Expansion Alters Human Bone Marrow-Derived Mesenchymal Stem Cell Production of Osteoarthritis-Relevant Cytokines and Growth Factors.

Purpose: The purposes of this study were to characterize the human bone marrow-derived mesenchymal stem cells (BM-MSCs) production of osteoarthritis-relevant cytokines and growth factors as they are purified and multiplied, a process termed culture expansion, and to compare the immunomodulatory potential of BM-MSCs based on source and medium used for culture expansion.

Methods: BM-MSCs were obtained from iliac crest bone marrow aspirates of 4 healthy donors. These 4 BM-MSC cell lines underwent 4 rounds, or "passages," of the institutional culture expansion protocol, using institutional culture media. The secretory molecules known to play a role in osteoarthritis-related inflammatory immune response, cartilage degradation, and patient symptoms, together called the BM-MSC "secretome," were measured at each passage. Three lines of commercially available BM-MSCs from healthy donors underwent culture expansion by the same protocol, using commercial culture media. The commercial BM-MSCs secretome and the institutional BM-MSCs secretome were compared at each passage. Significance was set at P < .05.

Results: Institutional BM-MSCs produced less interleukin-6 at passages 3 (237 ± 113 pg/mL) and 4 (237 ± 113 pg/mL) compared with passages 1 (884 ± 97 pg/mL) and 2 (1071 ± 129 pg/mL; P < .01). Institutional BM-MSCs produced more macrophage inflammatory protein 3-alpha at passage 4 than at passage 1 (106 ± 41 vs 32 ± 7 pg/mL; P < .01). Across passages of culture expansion, institutional BM-MSCs grown on institutional medium expressed more interleukin-6 (P < .001), interleukin-10 (P < .001), interleukin-1 beta (P < .001), tumor necrosis factor alpha (P = .004), and vascular endothelial growth factor C (P = .003) than commercially available BM-MSCs grown on commercial medium.

Conclusions: Culture expansion alters key molecules within the BM-MSC secretome. Additionally, differences in BM-MSC source and culture medium alter the BM-MSC secretome and its immunomodulatory potential.

Clinical relevance: This study characterizes the in-vitro changes in BM-MSC secretome during culture expansion based on the cell source and culture medium. It suggests nonequivalence of culture-expanded BM-MSC therapies obtained from different donors using different culture media, even if delivering equivalent numbers of BM-MSCs.