Copper ion-doped multifunctional hydrogel with mild photothermal enhancement promotes vascularized bone regeneration.

The design and construction of a new and excellent synthetic graft is of great significance in the field of bone defect repair and reconstruction. In this study, a dopamine modified chitosan hydrogel doped with Cu ions with a mild photothermal effect was designed to provide a better microenvironment to advance the bone repair via promote the angiogenesis and osteogenesis. Characterizations showed the successful synthesis of the material while it also presented excellent biocompatibility and mild photothermal effect under the irradiation of near-infrared light. Further, it could enhance the angiogenesis of HUVECs cells through promoting the ability of migration and tube formation and enhance the osteogenic differentiation of MC3T3-E1 cells via increasing the content of vital osteogenic factors including Runx2, Col-1, OPN, OCN, OSX, etc. The in vivo experiment also testified that it could promote the bone defect repair in rat models. These results indicate the multifunctional hydrogel is an ideal material for the treatment of bone defects and has good clinical application potential.

[Role of SIRT1 in the protection of intestinal epithelial barrier under hypoxia and its mechanism].

OBJECTIVE: To observe the effect of SIRT1 on intestinal barrier function of epithelial Caco-2 cells under hypoxia and investigate its mechanism. METHODS: Caco-2 cells were randomly divided into three groups: normoxia group (Nx), hypoxia group (Hx,1%O2 for 6 h) and hypoxia plus 40 µmol/L Resveratrol (agonist of SIRT1) group (Hx+Res). Transepithelial electrical resistance (TER) was determined. mRNA and protein expressions of SIRT1 and tight junctions (ZO-1, Occludin, Claudin-1) were examined by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting. RESULTS: Both mRNA and protein expressions of SIRT1 were significantly reduced in Hx group as compared with Nx group (0.40±0.02 vs. 0.70±0.07, P=0.001; 0.37±0.03 vs. 0.76±0.03, P=0.001). The mRNA and protein expressions of SIRT1 were significantly increased in Hx+Res group as compared with Hx group(0.50±0.02 vs. 0.40±0.02, P=0.026; 0.54±0.02 vs. 0.37±0.03, P=0.011). The expression levels of ZO-1, Occludin and Claudin-1 in Hx group were lower than those in Nx group (P<0.05), however, pretreatment with Resveratrol could attenuate the decreased expression of above 3 molecules under hypoxia(P<0.05). TERs of Nx group, Hx group and Hx+Res group were (142±7) Ohm/cm(2), (94±3) Ohm/cm(2) and (119±7) Ohm/cm(2) respectively. Compare with the Nx group, the TER of Hx group was significantly decreased(P<0.05). TER of Hx+Res group was significantly increased compare with Hx group, but it was still significantly lower than that in Nx group(P<0.05). CONCLUSIONS: Expression of SIRT1 is significantly reduced under hypoxia. Activation of SIRT1 can maintain the epithelial barrier function through regulating the expression of tight junctions under hypoxia.

Interferon-γ-induced intestinal epithelial barrier dysfunction by NF-κB/HIF-1α pathway.

Interferon-γ (IFN-γ) plays an important role in intestinal barrier dysfunction. However, the mechanisms are not fully understood. As hypoxia-inducible factor-1 (HIF-1) is a critical determinant response to hypoxia and inflammation, which has been shown to be deleterious to intestinal barrier function, we hypothesized that IFN-γ induces loss of barrier function through the regulation of HIF-1α activation and function. In this study, we detected the expressions of HIF-1α and tight junction proteins in IFN-γ-treated T84 intestinal epithelial cell line. IFN-γ led to an increase of HIF-1α expression in time- and dose-dependent manners but did not change the expression of HIF-1ß. The IFN-γ-induced increase in HIF-1α was associated with an activation of NF-κB. Treatment with the NF-κB inhibitor, pyrolidinedithiocarbamate (PDTC), significantly suppressed the activation of NF-κB and the expression of HIF-1α. In addition, IFN-γ also increased intestinal epithelial permeability and depletion of tight junction proteins; inhibition of NF-κB or HIF-1α prevented the increase in intestinal permeability and alteration in tight junction protein expressions. Interestingly, we demonstrated that a significant portion of IFN-γ activation NF-kB and modulation tight junction expression is mediated through HIF-1α. Taken together, this study suggested that IFN-γ induced the loss of epithelial barrier function and disruption of tight junction proteins, by upregulation of HIF-1α expression through NF-κB pathway.

The jagged-2/notch-1/hes-1 pathway is involved in intestinal epithelium regeneration after intestinal ischemia-reperfusion injury.

BACKGROUND: Notch signaling plays a critical role in the maintenance of intestinal crypt epithelial cell proliferation. The aim of this study was to investigate the role of Notch signaling in the proliferation and regeneration of intestinal epithelium after intestinal ischemia reperfusion (I/R) injury. METHODS: Male Sprague-Dawley rats were subjected to sham operation or I/R by occlusion of the superior mesenteric artery (SMA) for 20 min. Intestinal tissue samples were collected at 0, 1, 2, 4, and 6 h after reperfusion. Proliferation of the intestinal epithelium was evaluated by immunohistochemical staining of proliferating nuclear antigen (PCNA). The mRNA and protein expression levels of Notch signaling components were examined using Real-time PCR and Western blot analyses. Immunofluorescence was also performed to detect the expression and location of Jagged-2, cleaved Notch-1, and Hes-1 in the intestine. Finally, the γ-secretase inhibitor DAPT and the siRNA for Jagged-2 and Hes-1 were applied to investigate the functional role of Notch signaling in the proliferation of intestinal epithelial cells in an in vitro IEC-6 culture system. RESULTS: I/R injury caused increased intestinal crypt epithelial cell proliferation and increased mRNA and protein expression of Jagged-2, Notch-1, and Hes-1. The immunofluorescence results further confirmed increased protein expression of Jagged-2, cleaved Notch-1, and Hes-1 in the intestinal crypts. The inhibition of Notch signaling with DAPT and the suppression of Jagged-2 and Hes-1 expression using siRNA both significantly inhibited the proliferation of IEC-6 cells. CONCLUSION: The Jagged-2/Notch-1/Hes-1 signaling pathway is involved in intestinal epithelium regeneration early after I/R injury by increasing crypt epithelial cell proliferation.