The advent of mesenchymal stem cell (MSC)-based therapies has been an exciting innovation for the treatment of degenerative and inflammatory diseases. However, the surface markers that accurately reflect the self-renewal and differentiation potential of MSCs and their sensitivity to environmental cues remain poorly defined. Here, we studied the role of CD49f in bone marrow MSCs (BMSCs) and the mechanism by which it regulates the behavior of BMSCs under inflammatory conditions. We found that CD49f is preferentially expressed in fetal cells rather than adult cells, CD49f-positive BMSCs possess higher CFU-F formation ability and differentiation potential than CD49f negative cells, and the CD49f expression of BMSCs gradually decreases during in vitro passaging. CD49f knockdown dramatically decreased the differentiation of BMSCs and isoform A was demonstrated to be the main functional form that enhanced the differentiation ability of BMSCs. The influences of inflammatory cytokines on BMSCs revealed that TNF-a downregulated CD49f in BMSCs with impaired differentiation, decreased adhesion to laminins, and increased migration. Moreover, tissue transglutaminase was found to work together with CD49f to regulate the behavior of BMSCs. Finally, we showed that mTOR signaling rather than NF-jB activation mediated CD49f downregulation induced by TNF-a and maintained CD49f homeostasis in BMSCs. Our findings suggest that CD49f is a stemness marker of BMSCs and is tightly correlated with the behavioral changes of BMSCs under inflammatory conditions. These data demonstrate a novel role for CD49f in sensing inflammation through mTOR pathway to further modulate the behavior of MSCs to fulfill the requirements of the body. STEM CELLS 2015;33:2798-2810 SIGNIFICANCE STATEMENTThe identification of stemness markers and the understanding of their regulation under different physiological and pathological conditions are of the utmost importance for both stem cell research and the development of personalized MSCs therapy. Our study demonstrates that CD49f serves not only as a stemness marker for MSCs, but also plays roles in sensing inflammatory cues and further regulating the behaviors of MSCs. Additionally, the novel information about the specific roles of CD49f splicing isoforms in MSCs, CD49f binding with TG2, and CD49f regulation by mTOR signaling advances the field of CD49f.

Human dermal fibrotic disease keloid has been a clinical challenge because of its tumour-like growth and the lack of effective therapy. Dysregulated alternative splicing events have been demonstrated in tumours and fibrosis. In the current study, for the first time, it was demonstrated that the splicing regulator polypyrimidine tract-binding protein (PTB), which plays a pivotal role in tumour proliferation, invasion and metastasis, is overexpressed in keloid tissues and fibroblasts. Additionally, TGF-β1 upregulated the expressions of PTB and its upstream regulator, C-MYC, in keloid fibroblasts. Furthermore, we suppressed PTB using siRNA in keloid fibroblasts and in a keloid xenograft nude mouse model. PTB knockdown significantly slowed the proliferation of keloid fibroblasts and accelerated the regression of transplanted keloid tissues, which was accompanied by a shift in the alternative splicing of USP5 and RTN4. Moreover, when PTB was suppressed, there was a reduction in excessive deposition of FN1 and COL3A1 in transplanted keloid tissues. However, only FN1 was downregulated in keloid fibroblasts that were cultured in media supplemented with TGF-β1. Our study provides evidence for the role of PTB in keloid pathophysiology and offers a novel therapeutic target for keloids. Most importantly, the role TGF-β1 regulation of PTB may provide new insights into the mechanisms underlying inflammatory cytokine-induced fibrosis.

BackgroundIn spite of the purification of the laying hens and broilers of avian leukosis virus (ALV) has made remarkable achievements, the infection of ALV was still serious in Chinese indigenous chickens.MethodsIn order to assess the epidemic state of avian leukosis virus in indigenous chickens in China, 10 novel strains of ALV subgroup J (ALV-J), named JS16JH01 to JS16JH10, were isolated and identified by virus isolation and immunofluorescence antibody assays from a Chinese local breed farm with a sporadic incidence of tumors. To understand their virological characteristics further, the proviral genome of ENV-LTR was sequenced and compared with the reference strains.ResultsThe homology of the gp85 gene between the ten ALV-J strains and NX0101 was in the range from 89.7–94.8% at the nuclear acid level. In addition, their gp85 genes were quite varied, with identities of 92–98% with themselves at the nuclear acid level. There were several snp and indel sites in the amino acid sequence of gp85 genes after comparison with other reference strains of ALV. Interestingly, a novel insertion in the gp85 region was found in two strains, JS16JH01 and JS16JH07, compared with NX0101 and HPRS-103.DiscussionAt present, owing to the large-scale purification of ALV in China, laying hens and broiler chickens with ALV infection are rarely detected, but ALVs are still frequently detected in the local chickens, which suggests that more efforts should be applied to the purification of ALV from indigenous chickens.