[Xenogeneic protein free cultivation of mesenchymal multipotent stromal cells]

Abstract

Purpose of the study: The aim of this study was to compare the standard laboratory method of cultivation of mesenchymal multipotent stromal cells (MSC) and a novel technique of rapid MSC expansion focused on simple clinical use.

Material and methods: Bone marrow mononuclear cells of donors were cultured for 14 days by the standard and the new cultivation method. The standard method (STD) was based on an alpha MEM medium supplemented with foetal calf serum (FCS). The new animal protein-free method (CLI) was based on the clinical grade medium CellgroTM, pooled human serum and human recombinant growth factors (EGF, PDGF-BB, M-CSF, FGF-2) supplemented with dexamethasone, insulin and ascorbic acid. The cell product was analyzed by flow cytometry. Furthermore, the cell products of STD and CLI methods were differentiated in vitro, and histochemical and immunohistochemical analyses, electron microscopy and elemental analysis were performed. Some cells were seeded on biodegradable scaffolds, in vivo implanted into immunodeficient mice for 6 weeks and evaluated by histological methods.

Results: Yields of the CLI method after 14 days of cultivation were 40-fold higher than those obtained by the STD technique (p<0.05). Cell products of both STD and CLI methods fulfilled the criteria of MSC in terms of antigen expression assessed by flow cytometry, as well as osteogenic, chondrogenic and adipogenic in vitro differentiation assays. Moreover, these cells seeded on three-dimensional scaffolds cultured in osteogenic medium produced mineral deposits and a fibrillar extracellular matrix seen with the electron microscope. Deposits examined by element analysis contained calcium and phosphorus at a ratio of 5 to 3, which corresponded to hydroxyapatite. The cell product seeded on biodegradable scaffolds and implanted into immunodeficient mice was able to form a bone-like calcified tissue with blood supply of mouse origin.

Discussion: The currently used methods of cultivation have certain disadvantages compared to the CLI technique, such as a longer cultivation period, need of primary expansion and reseeding and use of FCS with all its potential risks. High yields of cells obtained by the CLI method in a very short time make the use of cultured cells potentially suitable for an acute trauma management. Other therapeutic non-orthotopic applications of CLI-cultured cells have to be further investigated.

Conclusions: The CLI method is unique, rapid, simple and lacking the addition of animal proteins. CLI-cultured cells fulfil the criteria of MSC. The CLI method potentially allows for closed system cultivation in good manufacturing practice (GMP) conditions. It seems to be easily transferable to good clinical practice compared to other protocols and should extend the possibilities of cell therapy and tissue engineering of cartilage and bone. The new method is protected by Czech patent 301 148 and by Europian patent EP 1999250 according to Czech and international laws.