IntroductionMesenchymal stem cells (MSCs) play a central role in mediating endogenous repair of cell and tissue damage. Biologic aging is a universal process that results in changes at the cellular and molecular levels. In the present study, the role of microRNA (miRNA) in age-induced molecular changes in MSCs derived from adipose tissue (ASCs) and bone marrow (BMSCs) from young and old human donors were investigated by using an unbiased genome-wide approach.MethodsHuman ASCs and BMSCs from young and old donors were cultured, and total RNA was isolated. The miRNA fraction was enriched and used to determine the expression profile of miRNA in young and old donor MSCs. Based on miRNA expression, differences in donor MSCs were further investigated by using differentiation assays, Western blot, immunocytochemistry, and bioinformatics.ResultsBiologic aging demonstrated reduced osteogenic and adipogenic potential in ASCs isolated from older donors, whereas cell size, complexity, and cell-surface markers remained intact with aging. Analysis of miRNA profiles revealed that small subsets of active miRNAs changed secondary to aging. Evaluation of miRNA showed significantly decreased levels of gene expression of inhibitory kappa B kinase (IκB), interleukin-1α, inducible nitric oxide synthase (iNOS), mitogen-activated protein kinase/p38, ERK1/2, c-fos, and c-jun in MSCs from older donors by both bioinformatics and Western blot analysis. Nuclear factor kappa B (NF-κB), myc, and interleukin-4 receptor mRNA levels were significantly elevated in aged cells from both the adipose and bone marrow depots. Immunocytochemistry showed nuclear localization in young donors, but a cytosolic predominance of phosphorylated NF-κB in ASCs from older donors. Western blot demonstrated significantly elevated levels of NF-κB subunits, p65 and p50, and AKT.ConclusionsThese findings suggest that differential expression of miRNA is an integral component of biologic aging in MSCs.

Background:The effects of inflammation upon the biology of human mesenchymal stem cells are poorly understood. Results: IL-1␤ provoked massive hydroxyapatite deposition by inhibiting ectonucleotide pyrophosphatase. Cells did not express typical markers of osteoblasts or other mesenchymal lineages. Conclusion: Inflammation promotes mineralization by a novel mechanism. Significance: These data provide new insights into cytokine effects on mineralization of soft tissues.

While attachment to bone is required for optimal osteoclast function, the molecular events that underlie this fact are unclear, other than that the cell requires adhesion to mineralized matrix to assume a fully differentiated phenotype. To address this issue, we cultured murine bone marrow-derived osteoclasts on either cell culture plastic or devitalized mouse calvariae to identify the distinct genetic profile induced by interaction with bone. Among a number of genes previously unknown to be expressed in osteoclasts we found that Annexin A8 (AnxA8) mRNA was markedly up-regulated by bone. AnxA8 protein was present at high levels in osteoclasts present in human tissues recovered from sites of pathological bone loss. The presence of bone mineral was required for up-regulation of AnxA8 mRNA since osteoclasts plated on decalcified bone express AnxA8 at low levels as did osteoclasts plated on native or denatured type I collagen. Finally, AnxA8-regulated cytoskeletal reorganization in osteoclasts generated on a mineralized matrix. Thus, we used a novel approach to define a distinct bone-dependent genetic program associated with terminal osteoclast differentiation and identified Anxa8 as a gene strongly induced late in osteoclast differentiation and a protein that regulates formation of the cell's characteristic actin ring.

Purpose The Ewing Sarcoma Family of Tumors (ESFTs) comprises a group of aggressive, malignant bone and soft tissue tumors that predominantly affect children and young adults. These tumors frequently share expression of the EWS-FLI-1 translocation, which is central to tumor survival but not present in healthy cells. In this study, we examined EWS-FLI-1 antigens for their capacity to induce immunity against a range of ESFT types. Design Computer prediction analysis of peptide binding, HLA-A2.1 stabilization assays, and induction of Cytotoxic T-Lymphocytes (CTL) in immunized HLA-A2.1 transgenic mice were used to assess the immunogenicity of native and modified peptides derived from the fusion region of EWS-FLI-1 type 1. CTL-killing of multiple ESFT family members in vitro, and control of established xenografts in vivo, was assessed. We also examined whether these peptides could induce human CTLs in vitro. Results EWS-FLI-1 type 1 peptides were unable to stabilize cell surface HLA-A2.1 and induced weak CTL activity against Ewing Sarcoma cells. In contrast, peptides with modified anchor residues induced potent CTL killing of Ewing Sarcoma cells presenting endogenous (native) peptides. The adoptive transfer of CTL specific for the modified peptide YLNPSVDSV resulted in enhanced survival of mice with established Ewing Sarcoma xenografts. YLNPSVDSV-specific CTL displayed potent killing of multiple ESFT types in vitro: Ewing Sarcoma, pPNET, Askin’s Tumor, and Biphenotypic Sarcoma. Stimulation of human Peripheral Blood Mononuclear Cells with YLNPSVDSV peptide resulted in potent CTL-killing. Conclusions These data show that YLNPSVDSV peptide is a promising antigen for ESFT immunotherapy and warrants further clinical development.