MicroRNAs and Bone Regeneration

Bone has multiple functions, both morphologically and physiologically, and it frequently features in the pathological condition, including fracture and osteoporosis. For bone regeneration therapy, the regulation of osteoblast differentiation is important. MicroRNA (miRNA)s are short noncoding RNA which regulate gene expression at the post-transcriptional level. MiRNAs play an important role not only in a variety of other cellular processes including differentiation, proliferation, and apoptosis but also in the pathogenesis of human diseases. Recently, miRNAs have been known to participate in osteoblast differentiation by regulating several signaling pathways including transcription factors. New insight into the mechanism during osteogenes is affected by miRNAs has been gained. Moreover, therapeutic trials for bone diseases including osteoporosis, fracture and bone defects targeting miRNAs have been examined in animal models. MiRNA therapy will enable development of a bone regeneration therapy.

Identifying hedgehog signaling specific microRNAs in glioblastomas

Aberrant activation of hedgehog (Hh) signaling pathway plays an important role in the development and proliferation of glioblastoma (GBM) cells. However, its mechanism remains unknown. MicroRNAs (miRNAs) are short non-coding RNA molecules which are involved in the post-transcriptional regulation of genes, and enrolled in signaling transduction network in tumors. This study was designed to investigate the role of miRNAs targeting the Hh signaling pathway in GBMs. According to the expression level of Gli1 mRNA measured by real time PCR, GBM samples were assigned to Gli1 high or low expression group. MiRNA microarray was applied to screen the dysregulated miRNA. As a result, 17 miRNAs were differentially expressed between Gli1 high expression and low expression groups (p < 0.005). Thirteen miRNAs including miR-125b-1 were downregulated, while only 4 miRNAs including miR-144 were upregulated in Gli1 high expression group. In summary, our study presents a subset of miRNAs which target the Hh signaling pathway in GBMs, and throws some light on the aberrant activation mechanism.

Vector-mediated selective expression of lethal factor, a toxic element of Bacillus anthracis, damages A549 cells via inhibition of MAPK and AKT pathways

Lethal factor (LF), a major toxic element of Bacillus anthracis combined with its protective antigen (PA), enters the cells through the cytomembrane receptors and causes damage to the host cells, thereby leading to septicemia, toxemia, and meningitis with high mortality. LF has been identified as a potential biotech-weapon, which can impede cancer growth in vascular endothelial cells because of its cytotoxicity. However, the feasibility of LF application and further investigations has been limited because LF is nonspecific. To solve this problem, we constructed a vector that contained the LF sequence, which was regulated by a tumor-specific human telomerase reverse transcriptase promoter (hTERTp). Results showed that LF was selectively expressed in lung cancer A549 cells but not in normal cells, thereby resulting in A549 cell apoptosis. The results also revealed that the inhibition of mitogen-activated protein kinase and AKT pathways was partially involved in the process. Thus, hTERTp-regulated LF increase could be a promising approach in lung cancer-targeted therapy.

Mechano-regulation of alternative splicing

Alternative splicing contributes to the complexity of proteome by producing multiple mRNAs from a single gene. Affymetrix exon arrays and experiments in vivo or in vitro demonstrated that alternative splicing was regulated by mechanical stress. Expression of mechano-growth factor (MGF) which is the splicing isoform of insulin-like growth factor 1(IGF-1) and vascular endothelial growth factor (VEGF) splicing variants such as VEGF₁₂₁, VEGF_165, VEGF₂₀₆, VEGF₁₈₉, VEGF₁₆₅ and VEGF₁₄₅ are regulated by mechanical stress. However, the mechanism of this process is not yet clear. Increasing evidences showed that the possible mechanism is related to Ca²⁺ signal pathway and phosphorylation signal pathway. This review proposes possible mechanisms of mechanical splicing regulation. This will contribute to the biomechanical study of alternative splicing.