Expression and secretion of interleukin-1β, tumour necrosis factor-α and interleukin-10 by hypoxia- and serum-deprivation-stimulated mesenchymal stem cells Implications for their paracrine roles

To understand the potential paracrine roles of interleukin-1 beta (IL-1 beta), tumour necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10), the expression and secretion of these factors by rat bone marrow-derived mesenchymal cells stimulated by hypoxia (4% oxygen) and serum deprivation (hypoxia/SD) were investigated. We found that hypoxia/SD induced nuclear factor kappa Bp65-dependent IL-1 beta and TNF-alpha transcription. Furthermore, hypoxia/SD stimulated the translation of pro-IL-1 beta and its processing to mature IL-1 beta, although the translation of TNF-alpha was unchanged. Unexpectedly, the release of IL-1 beta and TNF-alpha from hypoxia/SD-stimulated mesenchymal cells was undetectable unless ATP or lipopolysaccharide was present. This result suggests that IL-1 beta and TNF-alpha are not responsible for the paracrine effects of mesenchymal cells under ischaemic conditions. We also found that hypoxia/SD induced the transcription and secretion of IL-10, which were significantly enhanced by lipopolysaccharide and the proteasomal inhibitor MG132. Moreover, both the conditioned medium from hypoxia/SD-stimulated mesenchymal cells (MSC-CM) and IL-10 efficiently inhibited cardiac fibroblast proliferation and collagen expression in vitro, suggesting that mesenchymal cell-secreted IL-10 prevents cardiac fibrosis in a paracrine manner under ischaemic conditions. Taken together, these findings may improve understanding of the cellu-lar and molecular basis of the anti-inflammatory and paracrine effects of mesenchymal cells.