Human Mesenchymal Stem Cell Therapy: Platelet Lysate Supports Efficient Preclinical Expansion.

Coinfusion of hematopoietic stem cells with multipotent mesenchymal stromal/stem cells (MSC) to facilitate engraftment and immunomodulatory treatment of graft versus host disease (GvHD) are the two foremost applications of MSC therapy in hematology and oncology. Translation of promising experimental results into clinical applications has been mainly hampered by the strict dependence of MSC propagation from fetal bovine serum (FBS)-derived factors.

We analyzed the capacity of different preparations of human platelet lysates (HPL) to replace FBS for clinical scale MSC production with cytomic, proteomic and genomic technology.

Using a previously established two-step good manufacturing practice procedure for MSC propagation, we found that HPL can fully replace FBS as a growth factor supplement for clinical scale MSC preparation. HPL was reproducibly more efficient than FBS and supported the outgrowth of >400 million MSC from <0.4 million primary MSC (derived from <2mL bone marrow aspiration within 10 days ex vivo) within only 2 additional weeks of culture. Although morphologically distinct, HPL-MSC and FBS-MSC did not differ regarding their CD13⁺/29⁺/73⁺/90⁺/105⁺/146⁺/34⁻/45⁻/133⁻/HLA-AB⁺ immunophenotype. Multiplex analyses allowed delineating a distinct cytokine and growth factor profile. Whole transcriptome microarray analyses revealed a differential regulation of >300 genes after only one cycle of human as compared to bovine growth factor stimulation. Allogeneic HPL-MSC infusion in an intent to treat refractory GvHD was feasible and without infusion-related side effects in one patient. This new FBS-free two-step procedure for clinical scale MSC propagation will largely facilitate rational clinical testing of MSC based therapies. Replacing FBS with HPL excludes bovine prion, viral and zoonose contamination of the stem cell product. Based on this protocol a clinical trial for the treatment of steroid-refractory GvHD with HPL-MSC has been initiated.