Dialysis and lyophilization of the mesenchymal stromal cell secretome for wound healing.

Background Aims: The clinical translation of mesenchymal stromal cell secretome (MSC-S) has been challenging owing to a lack of appropriate methods in downstream processing. Dialysis is an age-old method of protein purification by the exchange of small molecules through a semi-permeable membrane. In this study, we investigated the potential of three forms of umbilical cord-derived MSC secretome (UC-MSC-S)-native (S), dialyzed (DS), and lyophilized (LDS)-for wound healing applications.

Methods And Results: We dialyzed the UC-MSC-S using Slide-A-Lyzer G3 Dialysis Cassettes (20K MWCO) and then lyophilized it to obtain secretome powder. The DS fraction exhibited an 86.01-fold decrease compared with S, whereas LDS showed a 613.71-fold increase in the total protein concentration. Growth factor analysis revealed a significant decrease in the levels of interleukin-6 (IL-6; 54.44-fold), angiopoietin-1 (79.56-fold), angiopoietin-2 (51.76-fold), IL-8 (54.4-fold), platelet endothelial cell adhesion molecule-1 (PECAM-1; 63.25-fold), phosphatidylinositol glycan anchor biosynthesis class F (PIGF; 40.42-fold), vascular endothelial growth factor (VEGF; 39.64-fold), and tumor necrosis factor alpha (TNF-α; 24.62-fold) after dialysis as analyzed by the LEGEND plex multi-analyte flow assay kit on a FACS analyzer. Post-lyophilization, the levels of IL-6 (392.21-fold), angiopoietin-1 (823.04-fold), angiopoietin-2 (397.69-fold), IL-8 (584.83-fold), PECAM-1 (341.28-fold), PIGF (342.85-fold), VEGF (2209.42-fold), and TNF-α (194.4-fold) were enriched in LDS. The highest wound closure (64.07%) and a significant increase in angiogenesis were seen in DLS at the concentration of 1 µg/µL of protein by wound scratch and in ovo yolk sac membrane assay, respectively.

Conclusions: Dialysis followed by lyophilization is a simple and cost-effective method to fractionate and enrich the bioactive components of MSC-S without compromising the bioactivity for tailor-made applications.