Background: Multilineage differentiation, immunomodulation and secretion of trophic factors render mesenchymal
stromal cells (MSC) highly attractive for clinical application. Human platelet derivatives such as pooled human platelet
lysate (pHPL) and thrombin-activated platelet releasate in plasma (tPRP) have been introduced as alternatives to fetal
bovine serum (FBS) to achieve GMP-compliance. However, whereas both pHPL and tPRP support similar proliferation
kinetics of lipoaspirate-derived MSC (LA-MSC), only pHPL significantly accelerates bone marrow-derived MSC (BM-MSC)
expansion. To identify functionally bioactive factors affecting ex vivo MSC expansion, a differential proteomic approach
was performed and identified candidate proteins were evaluated within a bioassay.
Results: Two dimensional difference gel electrophoresis (2D-DIGE), MALDI-TOF analyses and complementary Western
blotting revealed 20 differential protein species. 14 candidate proteins occured at higher concentrations in pHPL
compared to tPRP and 6 at higher concentrations in tPRP. The candidate proteins fibrinogen and apolipoprotein A1
differentially affected LA- and BM-MSC proliferation.
In a second set of experiments, reference cytokines known to foster proliferation in FBS were tested for their effects in
the human supplements. Interestingly although these cytokines promoted proliferation in FBS, they failed to do so
when added to the humanized system.
Conclusions: The differential proteomic approach identified novel platelet derived factors differentially acting on
human MSC proliferation. Complementary testing of reference cytokines revealed a lack of stimulation in the human
supplements compared to FBS. The data describe a new coherent approach to combine proteomic technologies with
functional testing to develop novel, humanized, GMP-compliant conditions for MSC expansion