For example, studies have shown that adipose tissue-derived MSCs exhibit in vitro immunomodulatory properties at higher efficiencies compared to their bone marrow-derived counterparts [40]. Another example can be found in a study comparing the differentiation potential of MSCs derived AG14699 from bone marrow and the pancreas to become insulin-producing endocrine cells [41]. That study revealed that MSCs derived from the pancreas are committed to an endocrine fate and thus have a greater propensity to generate insulin-producing cells compared

to bone marrow-derived MSCs. Therefore, to select an ideal source of MSCs for therapeutic use, the functional properties of the cells (e.g. differentiation potential, immunomodulation, secretion Buparlisib concentration of bioactive factors) should be critically evaluated in comparison with the properties of cells from other potential sources. Although bone marrow-derived MSCs are among the most frequently used types in bone regeneration studies [44], [45], [46] and [47], several investigators have suggested the use of other

sources of MSCs, namely, peripheral blood-derived MSCs, fetal MSCs and adipose tissue-derived MSCs [48], [49], [50], [51] and [52]. However, there are no clear guidelines indicating which sources are the most suitable for bone regeneration. To develop MSC-based methods for bone regeneration, mice are suitable experimental animals; however, standard culture conditions, including plastic culture flasks and standard culture media do not support the passage of pure MSCs derived from murine bone marrow. Several groups have reported independent methods for purifying MSCs obtained from murine bone marrow, including plastic adherent selection

[53], retroviral infection [54] and unique culture systems [55], [56], [57], [58] and [59]. However, the long time passage of MSCs has not been successfully achieved. Moreover, the fact that murine bone marrow harbors very few MSCs and contains hematopoietic cells [60] shows that murine bone marrow may not be a suitable source of murine MSCs. To overcome the difficulties in culturing MSCs obtained from mice, Sun et Florfenicol al. [61] established murine MSC cultures by adding fragments of murine bone to murine bone marrow cells. Short et al. [62], using a CFU-Fs assay, found that the femoral bone itself is a richer source of murine MSCs than the marrow within the bone. Additionally, we [63] succeeded in maintaining murine MSCs for more than 120 days in culture in the presence of basic fibroblast growth factor (bFGF). Based on this information, we confirmed that cells derived from compact bone and propagated in bFGF-conditioned medium are murine MSCs and that bFGF-conditioned medium supports the self-renewal of murine MSCs and maintains the potential of these MSCs to differentiate along multiple lineages, including chondrocyte, osteocyte and adipocyte lineages (Fig. 2).