Background

Therapeutic application of mesenchymal stromal cells (MSC) implies their ex vivo expansion in growth media that can affect MSC characteristics. Human platelet lysate (PL) is a xenogeneic-free (XF) cell culture supplement but its mostly unknown composition is a big drawback. Hence, defined serum- and xenogeneic-free (SF/XF) media were developed, though, most of them led to poor cell growth. We expanded MSC in either XF or SF/XF media or in mixtures of both and analyzed functional characteristics.

Methods

MSC were expanded in aMEM+8%PL (XF, media 1), StemMACS (Miltenyi Biotec; SF/XF, media 13), or in mixtures of both media (media 4, 7, 10; for composition see Table 1). Proteome of media and cells was only analysed for XF and SF/XF approaches while further analyses were performed for all media. Specific growth factors, cytokines, chemokines, hormones and other factors were determined in media and MSC conditioned media. Consumption of growth factors or secretion of functionally relevant factors was analysed. Expression of surface antigens related to metabolism, adhesion, differentiation and other cellular processes was investigated. Differentiation potential and migratory capacity of MSC were determined as functional cell characteristics.

Results

Comparison of proteome of XF and SF/XF media identified various proteins exclusive for each media. Respective cells showed significant alterations in protein expression involved in several cellular pathways. Analysis of additional factors showed higher concentrations in XF media except for fibroblast growth factor-2 and insulin. Significantly different consumption of growth factors like platelet derived growth factor was observed and confirmed by significant differences in receptor expression. Secretion of functionally relevant factors could be identified and varied significantly for cells of different media (see Table 1). Cells of all media retained their differentiation potential but migration of cells was impaired by SF/XF conditions.

Conclusion

Metabolism of cells varied for XF and SF/XF media as shown by proteome analysis. This may rely on availability of nutrients as indicated by divergent consumption and secretion pattern of cells. Impaired migratory potential of cells grown in SF/XF media may be unfavorable for MSC homing towards sites of injury. Since therapeutic applications require different MSC characteristics, growth media may be utilized as priming approach for specific purposes.

Offenlegung Interessenkonflikt:

The authors declare no commercial, proprietary or financial interest. MR and HS work for IKT Ulm, manufacturing PL. VJ, MR and HS received funding from the Bundesministerium für Verteidigung, the European Union"s Seventh Framework Programme and the European Union"s Network HORIZON2020. The materials presented and views expressed here are the responsibility of the authors only. The European Union Commission takes no responsibility for any use made of the information set out.