In the previous literature, “mesenchymal stromal cells,” “mesenchymal stem cells,” and “multipotent stem cells” are collectively abbreviated as “MSCs,” which are likely to lead some confusion. Similarly, “bone marrow stromal cells” and “bone marrow stem cells” are collectively abbreviated as “BMSCs.” In this subdivision, mesenchymal stromal cell is abbreviated as “MSC,” and bone marrow stromal cell is abbreviated as “BMSC” to avoid misunderstanding. According to a review article by Charbord, the historical emergence of the concept of “mesenchymal stem cell” emerged in the 1960s [34]. Besides hematopoietic stem/progenitor cells, the bone marrow contains cells that form colonies consisting of plastic-adherent, elongated cells of fibroblastic appearance when cultured at low density in liquid medium containing serum. In 1991, Caplan first introduced the term “mesenchymal stem cell.” To clarify the nomenclature for MSC, International Society for Cellular Therapy has proposed the term “multipotent mesenchymal stromal cell” in 2005. The accumulation of several years of solid and rigorous research indicates that MSCs are mesenchymal precursors with multipotency and self-renewal capacity that are present in the bone marrow of multiple species, including humans, as well as in other sources, including adipose tissue and the umbilical cord. MSCs can be extensively amplified ex vivo, which enables their use in cell therapy applications. Although the pluripotency of MSCs is somewhat controversial (criteria for differentiation need to be rigorously defined) [34, 35], MSCs, especially BMSCs, show several advantages (see Chap. 2) over other cell types as resources of cell therapy against cerebral stroke.

Regarding the cell culture of human BMSCs, previous basic research investigating human BMSC (hBMSC) therapy against cerebral stroke in animal models employed liquid culture media comprising a basic culture medium with supplements for cell growth [36–50]. Table 5.3 summarizes the basic culture medium and supplements used for ex vivo hBMSC expansion in these preclinical studies. Historically, animal serum (i.e., fetal bovine serum; FBS) or human serum was added to the basic medium, including Dulbecco’s modified Eagle medium (DMEM) or alpha-minimal essential medium (αMEM) for ex vivo cell expansion. These basic media contain inorganic salts, amino acids, vitamins, nucleotides, glucose, and buffers. In most cases, antibiotic agents were also added. As previously discussed elsewhere, the use of FBS raises several concerns for preparations of clinical-grade hBMSC, including the potential for an immunologic reaction to the xenogeneic antigen and/or the potential risk for viral and prion contamination [51]. Animal or human serum has also been shown to have inconsistent lot-to-lot performance, which may cause variability in the cell expansion effect. To overcome the inconsistent performance associated with serum, the development of serum-free hBMSC culture medium has been warranted. Toward this end, human platelet lysate (PL) was recently tested for use in hBMSC expansion instead of FBS or autologous human serum. As a result, some researchers reported that autologous human PL was an efficient substitute for FBS in expanding hBMSCs [52, 53]. More recently, there have been attempts to establish another serum-free expansion system for hBMSCs. Chase et al. reported a serum-free medium containing xenogeneic components as a containing medium as a potential substitute for serum-containing medium in hBMSC expansion [54]. Thus, hBMSCs isolated and expanded in serum-free medium supplemented with recombinant human platelet-derived growth factor-BB (PDGF-BB), basic fibroblast growth factor (bFGF), and transforming growth factor-β1 (TGF-β1) were found to effectively retain their phenotypic, differentiation, and colony-forming potential. In addition, Yamauchi et al. reported that serum-free, allogeneic human PL-containing medium supplemented with granulocyte-colony stimulating factor (G-CSF) was safe and could accelerate the expansion of hBMSCs for cell therapy against cerebral infarct in rats [55]. Taken together, multiple culture media have been tested for hBMSC culture in basic research studies, including serum-containing media, serum-free and allogeneic human PL-containing media supplemented with or without G-CSF, and serum-free and xenogeneic recombinant human PDGF-BB-, bFGF-, and TGF-β-containing media.