Differences in macrophage expression in induced membranes by fixation method - Masquelet technique using a mouse's femur critical-sized bone defect model

INTRODUCTION

Masquelet's induced membrane technique (MIMT) is an emerging method for reconstructing critical-sized bone defects. However, an incomplete understanding of the underlying biological and physical processes hinders further optimization. This study investigated the effect of different bone-defect fixation methods on macrophage expression in an induced membrane using a novel mouse plate-fixed Masquelet model.

METHODS

Mice were divided into Plate-fixed Masquelet (P-M), Intramedullary-fixed Masquelet (IM-M), Plate-fixed Control (P-C), and Back subfascial (B) groups. In the P-M and IM-M groups, a polymethylmethacrylate (PMMA) spacer was implanted into a 3 mm bone defect, while the defect in the P-C group remained unfilled. In group B, a spacer was inserted under the back fascia to examine membrane formation caused by a simple foreign body reaction. Tissues were collected at 1, 2, and 4 weeks postoperatively. Hematoxylin and eosin (H&E) staining and immunohistochemistry (CD68 and CD163: macrophage markers) were performed to assess macrophage expression within the membrane. qPCR was performed to measure the expression of CD68, CD163, and fibroblast growth factor 2 (FGF2).

RESULTS

Four weeks post-operation, the P-M group presented with minimal callus growth, whereas the IM-M group exhibited vigorous growth. The P-M and IM-M groups displayed a tri-layered membrane structure, which is consistent with the results of previous studies. The IM-M group had significantly thicker membranes, whereas the P-M group exhibited higher expression levels of CD68, CD163, and FGF2. Group P-C showed no osteogenesis, whereas group B maintained a thin, cell-dense membrane structure. The P-M group consistently showed higher gene expression levels than the P-C and P-B groups.

CONCLUSION

This study introduced a mouse plate fixation model for MIMT. The induced membranes could be adequately evaluated in this model. Induced membranes are formed by foreign body reactions to PMMA spacers; however, their properties are clearly different from those of simple foreign body reaction capsules and granulation tissues that infiltrate bone defects, suggesting that they are more complex tissues. The characteristics and expression of macrophages within these induced membranes varied according to the bone defect fixation method.

Rhinovirus replication causes RANTES production in primary bronchial epithelial cells

The mechanisms by which rhinovirus (RV) infections produce lower airway symptoms in asthmatic individuals are not fully established. To determine effects of RV infection on lung epithelial cells, primary human bronchial epithelial (BE) cells were infected with either RV16 or RV49, and viral replication, cell viability, and cell activation were measured. Both viral serotypes replicated in BE cells at 33 degrees C (DeltaTCID50 / ml = 2 to 2.5 log units) and at 37 degrees C (DeltaTCID50 /ml = 1.6 log units), but only high doses of RV49 (10(6) TCID50 /ml) caused cytopathic effects and reduced cell viability. In addition, regulated on activation, normal T cells expressed and secreted (RANTES) secretion was increased in epithelial cells infected with RV16 or RV49 (243 and 398 pg/ml versus 13 pg/ml uninfected control cells), and a similar pattern was seen for RANTES messenger RNA. RV infection also caused increased secretion of interleukin-8 and granulocyte macrophage colony-stimulating factor, but did not alter expression of either intercellular adhesion molecule-1 or human leukocyte-associated antigen-DR. These observations suggest that RVs can replicate in lower airway cells in vivo, and support epidemiologic studies that link RV with lower respiratory illnesses. Further, RV-induced secretion of RANTES and other cytokines could trigger antiviral immune responses in vivo, but these effects could also contribute to the pathogenesis of respiratory symptoms in subjects with asthma.

Effect of methotrexate on asthmatic reaction in sensitized guinea pigs

To understand the mechanism of antiasthmatic property of the antimetabolite agent, methotrexate (MTX), we examined its effect on time-related changes in specific airway resistance, bronchial responsiveness, and accumulation of lymphocytes and eosinophils in lung tissue and the bronchial lumen, before and after antigen challenge in ovalbumin (OA)-sensitized guinea pigs. Intraperitoneal administration of MTX significantly inhibited the antigen-induced late asthmatic responses (LAR) in actively sensitized animals in dose-dependent manner. Examination of bronchoalveolar lavage fluid (BALF) revealed that 0.25, 0.5 and 1.0 mg/kg body weight of MTX significantly inhibited the recruitment of eosinophils, lymphocytes (6 and 24 h after antigen challenge) and neutrophils (0.5, 6 and 24 h after antigen challenge) in the airways in a dose-dependent manner. Histological examination of lung tissue revealed that MTX significantly inhibited eosinophil infiltration into the airway (6 and 24 h after antigen challenge). Furthermore, MTX significantly inhibited the infiltrations of PKH-2-labeled peripheral blood mononuclear cells (mostly lymphocytes) into the airways (24 h after antigen challenge). MTX also inhibited airway hyperresponsiveness to methacholine following OA challenge in a dose-dependent manner. We conclude that the antiasthmatic effect of methotrexate is mainly due to inhibition lymphocytes and eosinophil infiltration into the airway.