Advances in the roles and mechanisms of nonsense-mediated mRNA decay in embryonic development / 生理学报

Nonsense-mediated mRNA decay (NMD) is originally identified as a widespread mRNA surveillance machinery in degrading 'aberrant' mRNA species with premature termination codons (PTCs) rapidly, which protects the cells from the accumulation of truncated proteins. Recent studies show that NMD can also regulate the degradation of normal gene transcripts, which execute important cellular and physiological functions. Therefore, NMD is considered as a highly conserved post-transcriptional regulatory mechanism in eukaryotes. NMD modulates 3% to 20% of the transcriptome from yeast to human directly or indirectly, which is essential for various physiological processes, such as cell homeostasis, stress response, proliferation, and differentiation. NMD can regulate the level of transcripts that involves in development, and single knockout of most NMD factors has an embryonic lethal effect. NMD plays an important role in the self-renewal, differentiation of embryonic stem cells and is critical during embryonic development. In this review, we summarized the latest advances in the roles and mechanisms of NMD in embryonic development, in order to provide new ideas for the research on embryonic development and the treatment of embryonic development related diseases.

Effect of polycaprolactone-ascobic acid scaffold in repairing articular cartilage defects in rabbits / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of polycaprolactone-ascobic acid (PCL-AA) scaffolds in promoting repair of articular cartilage defects in a rabbit model.</p><p><b>METHODS</b>The cartilage defects (3.5 mm in diameter and 3.0 mm in depth) were created in the trochlear groove of the bilateral knees of eight 6-month-old male New Zealand white rabbits. The rabbit models were then randomized into 3 groups to receive implantation of PCL-AA scaffolds (group A, n=8), implantation of PCL scaffolds without AA (group B, n=5), or no treatment (group C, n=3). In groups A and B, the mixture of fibrin gel (10 µg) and thrombinogen (10 µg) was injected into the defects to fix the scaffolds during the surgery. Histological analyses and quantitative assessments of defect repair were conducted at 6 and 12 weeks after implantation of the scaffold.</p><p><b>RESULTS</b>At 6 weeks after scaffold implantation, macroscopic observation showed better filling of the cartilage defects in group A than in group B, while no obvious defect repair was observed in group C. The rabbits in group A showed a significant improvement of the Wakitani score than those in group B (4.05∓1.11 vs 7.05∓0.98, P<0.05). HE staining revealed the presence of newly generated cells in and around the PCL-AA scaffolds without inflammatory cells. Safranin O staining showed a significantly greater ECM of the newly regenerated tissue in groups A and B than in group C (P<0.05), and the volume of the regenerated cartilage and cells was significantly greater in group A than in group B (P<0.05). Samples harvested at 12 weeks showed more hyalione-like cartilage formation than that at 6 weeks in group A.</p><p><b>CONCLUSION</b>PCL-AA scaffolds have a good biocompatibility and promotes the healing of articular cartilage defects. Adding ascorbic acid into PCL scaffolds better promotes cartilage formation in terms of both quantity and quality of the regenerated tissues. PCL-AA scaffolds can serve as a promising biomaterial to promote the regeneration of articular cartilage using tissue engineering techniques.</p>

Tricaicium phosphate complex pre-loaded with bone morphogenetic protein-2 or platelet derived growth factor-BB for repairing critical-size cranial defects in SD rats / 南方医科大学学报

<p><b>OBJECTIVE</b>To observe the effect of a new biomaterial in promoting the bone regeneration for repairing critical-size cranial defects in SD rats.</p><p><b>METHODS</b>Critical-size cranial defects were induced in 3-month-old male Sprague-Dawley rats and repaired with the implants of calcium phosphate from growth factor enhanced matrix 21 (CaPfromGEM21, control), CaPfromGEM21 preloaded with 10 ng bone morphogenetic protein-2 (BMP-2), CaPfromGEM21 preloaded with 100 ng BMP-2, CaPfromGEM21 preloaded with 0.3 µg platelet-derived growth factor-BB (PDGF-BB), or CaPfromGEM21 preloaded with 3 µg PDGF-BB. The defects were examined 6 weeks after the surgery with X-ray, micro-CT, HE staining and quantitative assessments.</p><p><b>RESULTS</b>X-ray showed defect repair in all the groups. The fracture line became obscure, and the defects were almost fully repaired by the regenerated bone tissues in PDGF-BB group. Micro-CT demonstarted new bone formation in the defects. The new bone volume was significantly greater in PDGF-BB groups than in BMP-2 groups (P<0.05). HE staining revealed the presence of new bones in the defects and new vessels in and around the new bones without inflammatory cells. The new bone area fraction was significantly greater in 10 ng BMP-2 group and 0.3 µg PDGF-BB group than in the control group (P<0.05), and the new vessel density was similar in the all the 4 cytokine-preloaded groups and all significantly greater than that in the blank and CaPfromGEM21 control group (P<0.05).</p><p><b>CONCLUSION</b>CaPfromGem21 combined with BMP-2 or PDGF-BB has good biocompatibility and can better promote bone regeneration for repairing bone defects.</p>

Migratory properties of vascular smooth muscle cells on extracellular matrix: a study on inverted coverslip migration assay / 生理学报

Migration of vascular smooth muscle cells (VSMCs) is involved in vascular development and various vascular diseases; however, the molecular mechanisms of VSMC migration remain unclear. In this study, we established an inverted coverslip migration assay to study the migratory properties of cultured VSMCs on extracellular matrix. Pulmonary arterial smooth muscle cells (PASMCs) from rats were cultured and identified by immunocytochemistry. Each coverslip with a confluent monolayer of PASMCs was inverted to a larger coverslip which was coated with phosphate buffered saline (PBS, as a control), poly-D-lysine hydrobromide (PDL), laminin or Matrigel. After 24 h of migration over the larger coverslip, PASMCs were fixed, and reliably quantified. The roles and mechanisms of extracellular matrix in PASMC migration were further studied by wound-healing assay and immunocytochemistry. The results showed that: (1) The purity of the cultured PASMCs was (97 ± 3)%. (2) The number of PASMCs on laminin or Matrigel migrating out from the inverted coverslip was significantly increased compared with that on PBS or PDL, and the migratory distance of PASMCs on laminin or Matrigel was significantly farther than that on PBS or PDL. (3) The motility of PASMCs on laminin or Matrigel was significantly higher than that on PBS at 8 h, 12 h and 24 h after wounding, respectively. (4) F-actin staining showed that F-actin was congregated along the brim of the migrating cells from the inverted coverslip, and vinculin (a cell marker of focal adhesion) staining showed that the distribution of vinculin in PASMCs plated on laminin or Matrigel was significantly lower than that on PBS or PDL. These results suggest that the inverted coverslip migration assay is suitable to study VSMC migration, and laminin and Matrigel substrates may promote VSMC migration through inhibiting the formation of focal adhesion and regulating the cytoskeletal proteins.

cAMP mediates the morphological change of cultured olfactory ensheathing cells induced by serum / 生理学报

Olfactory ensheathing cells (OECs) are a unique type of glia with common properties of astrocyte and Schwann cells. Cultured OECs have two morphological phenotypes, astrocyte-like OECs and Schwann cell-like OECs. Reversible changes have been found between these two morphological phenotypes. However, the molecular mechanism underlying the regulation of these reversible changes is still unknown. The aim of this paper is to establish a method for the morphology plasticity of cultured OECs, and investigate the underlying mechanism. Using the primary culture of OECs and immunocytochemistry, the morphology of OECs was observed under serum, serum free media or dB-cAMP drug treatment. Statistical analysis was performed to test differences among the percentages of OEC subtypes under these conditions. The results showed that under serum free media, (95.2±3.7)% of OECs showed Schwann cell-like morphology, and (4.8±3.7)% of OECs showed astrocyte-like morphology; however, under 10% serum media, (42.5±10.4)% of OECs exhibited Schwann cell-like morphology, and (57.5±10.4)% of OECs exhibited astrocyte-like morphology. When media was changed back to serum free media for 24 h, (94.8±5.0)% of OECs showed Schwann cell-like morphology, and (5.2±5.0)% of OECs showed astrocyte-like morphology. Furthermore, culture condition with or without serum did not affect the expression of OEC cell marker, p-75 and S-100. Finally, dB-cAMP, an analog of cAMP, through inhibiting the formation of F-actin stress fibers and focal adhesion, induced the morphology switch from astrocyte-like to Schwann cell-like morphology under serum condition, promoted the branches and the growth of processes. These results suggest that serum induces the morphology plasticity of cultured OECs, which is mediated by cytoplasmic cAMP level through regulating the formation of F-actin stress fibers and focal adhesion.