Mesenchymal stem cells MSCs can be isolated from various

Mesenchymal stem endothelin receptor antagonist (MSCs) can be isolated from various adult tissues (including bone marrow), they are multipotent and can differentiate into cells of the mesodermal (e.g. adipocytes, osteocytes, chondrocytes) as well as other embryonic lineages (Jiang et al., 2002). MSCs can also be cultured in vitro and retain their multilineage potential (Pittenger et al., 1999). It is not known whether AML cells can alter the biological functions of bone marrow MSCs. However, several observations suggest that cells with a stromal phenotype are important in leukemogenesis (Blau et al., 2011; Blau et al., 2007). MSCs may even mediate resistance against antileukemic chemotherapy (Kojima et al., 2011), possibly through their effects on the local cytokine network of the bone marrow (Bruserud et al., 2007; Uccelli et al., 2008). Finally, MSCs may also have immunomodulatory effects (Uccelli et al., 2008; Le Blanc et al., 2007; Le Blanc et al., 2008), but it is not known whether this is important for leukemogenesis or chemosensitivity. We have previously shown that the cytokine-mediated crosstalk between AML cells and differentiated stromal cells supports leukemia cell proliferation (Bruserud et al., 2004; Hatfield et al., 2006), and in the present study we investigated the cytokine-mediated crosstalk between primary human AML cells on immature MSCs.
Material and methods
Results
Discussion AML is a heterogeneous malignancy with regard to the biology of the leukemic cells, and bone marrow stromal cells support the growth of primary human AML cells (Bruserud et al., 2004; Hatfield et al., 2006; Reikvam et al., 2013b; Reikvam et al., 2012). In the present study we focused on the cytokine-mediated crosstalk between AML cells and MSCs and how this communication alters the biological characteristics of normal MSCs. Our MSCs were derived from three healthy individuals and showed several common characteristics; only one of them was therefore included in the global gene expression studies. Firstly, the MSCs expressed cell surface molecules consistent with a normal MSC phenotype (Kemp et al., 2005; Lv et al., 2014). Secondly, our MSCs showed only minor differences in their constitutive cytokine release profiles and several of these cytokines are constitutively released by normal MSCs during in vitro culture (Kastrinaki et al., 2013; Kemp et al., 2005; Ranganath et al., 2012). Thirdly, the presence of primary AML cells had no or only weak effects on MSC proliferation. Finally, all three MSC populations increased the in vitro proliferation and viability of primary human AML cells during coculture (Ito et al., 2014). Thus, our MSCs usually showed similar functional characteristics in various experimental models with only minor differences; these minor differences between our MSC populations are thus not caused by age-dependent differences (Liedtke et al., 2015; Lepperdinger, 2011). Taken together our observations suggest that the microarray data for the MSC24429 cells should be regarded as representative for our three normal human MSC populations. However, our results should be interpreted with care because of the limited number of MSC donors examined, e.g. we do not know whether age-induced differences in MSCs will influence the effects of the cocultures. Our in vitro model was based on the use of transwell cultures (Bruserud et al., 2004; Hatfield et al., 2006; Glenjen et al., 2002; Hatfield et al., 2009), and we could thereby investigate the cytokine-mediated crosstalk between MSCs and primary AML cells without the influence of direct cell–cell contact. We used a growth-factor supplemented culture medium that has been developed for MSC culture, and this medium could be used for AML cell culture. Our experimental model thereby represents a highly standardized methodological approach. We analyzed our results from the microarray studies by using different bioinformatical strategies. However, independent of the method used for data analysis we observed that patients were heterogeneous with regard to the effects of AML cells on MSCs and usually differed from normal hematopoietic cells, but a common effect of the AML cells was a modulation of the TLR–NFκB-chemokine axis in the normal MSCs. NFκB is also an important regulator of cytokine release by primary human AML cells (Bruserud et al., 2007). NFκB inhibitors are now available and this strategy thus represents a dual targeting of the cytokine release both in AML cells and MSCs (Reikvam et al., 2009).