Proto-oncogene expression during fracture repair

The possibility that proto-oncogenes play a role in fracture repair has been investigated in this study. Closed fractures were created in the tibiae of NZW rabbits and treated with a plaster cast. At intervals of 1 and 2 weeks, sections of the fracture callus were obtained and stained using an immunocytochemical technique which localised c-myc and c-jun. Osteogenic cells of the periosteum, endosteum, Haversian canal and new bone trabeculae expressed proto-oncogenes while hypertrophic chondrocytes were generally immunoreactive negative. The results suggest that proto-oncogene expression may be involved in post-fracture osteogenesis but not in the chondrogenic processes which precede endochondral bone formation. This could be used as a tool for diagnosing slow healing in the early stages of fracture repair.     

软骨细胞老化过程中胞外基质表达水平的改变

目的研究猪耳软骨细胞在体外培养传代过程中,细胞老化相关基因和胞外基质相关基因表达水平的改变。方法取体外培养猪耳软骨细胞,通过光镜,对各代细胞的形态学变化进行观测。RT-PCR检测各代细胞中bcl-2、端粒酶、Ⅰ型胶原和Ⅱ型胶原在mRNA表达水平上的改变。结果体外培养软骨细胞随着老化的进程,逐渐显现衰老和凋亡的特征。凋亡抑制基因bcl-2和控制细胞分裂的端粒酶的表达显著下降(P<0.01)。软骨细胞的特征性基质分子Ⅱ型胶原在第3代时表达水平有显著下降(P<0.01),降至原代细胞的5.47%±1.04%,在第4代几乎不再表达。而Ⅰ型胶原在第5代时,有显著上升(P<0.01);在第9代时又显著下降(P<0.01)。结论猪软骨细胞经体外培养,由第4代起逐渐发生去分化,丧失软骨细胞的表型。同时,细胞的增殖分裂能力亦逐步减退,细胞凋亡现象明显增加。     

ELMO1 increases expression of extracellular matrix proteins and inhibits cell adhesion to ECMs

We have previously identified the engulfment and cell motility 1 (ELMO1) as a susceptibility gene for diabetic nephropathy. To elucidate the role of ELMO1 in the pathogenesis of chronic renal injury, we examined the expression of Elmo1 in the kidney of a rat model for chronic glomerulonephritis (uninephrectomy plus anti-Thy1.1 antibody [E30] injection). We found that the expression of the Elmo1 was significantly increased in the renal cortex and glomeruli of uninephrectomized rats injected with E30 compared to controls. By in situ hybridization, the expression of Elmo1 was shown to be elevated in the diseased kidney, especially in glomerular epithelial cells. In COS cells, the overexpression of ELMO1 resulted in a substantial increase in fibronectin expression, whereas the depletion of the ELMO1 by small interfering RNA (siRNA) targeting ELMO1 significantly suppressed the fibronectin expression in ELMO1 overexpressing and control cells. We also found that the expression of integrin-linked kinase (ILK) was significantly increased in ELMO1 overexpressing cells, and the ELMO1-induced increase in fibronectin was partially, but significantly, inhibited by siRNA targeting ILK. Furthermore, we identified that the cell adhesion to ECMs was considerably inhibited in cells overexpressing ELMO1. These results suggest that the ELMO1 contributes to the development and progression of chronic glomerular injury through the dysregulation of ECM metabolism and the reduction in cell adhesive properties to ECMs.     

Cell, matrix changes and alpha-smooth muscle actin expression in repair of the canine meniscus.

Processes in the repair of a crevice in the knee joint meniscus were investigated in 10 dogs. Two 2-mm cylindrical plugs from each medial meniscus were removed, rendered acellular by freezing and thawing, and then reinserted into the meniscus. Dogs were euthanized at intervals of 3-52 weeks after surgery. The crevice between the plug and meniscus at 3 weeks after surgery was filled with a tissue containing alpha-smooth muscle actin-positive cells. One year after surgery, the plug had remodeled and was populated with spindle-shaped and fibrochondrocyte-like cells. The plug had an appearance intermediate between that of hyaline and fibrocartilage at this time, with a seamless integration in sites between the remodeled plug and the surrounding meniscus. alpha-smooth muscle actin-positive cells were concentrated at the interface of the remodeled plug and adjacent meniscus and at the surface of the plug. Therefore, remodeling of both the plug and meniscal tissue and the participation of alpha-smooth muscle actin-positive cells appear essential for integration of the plug into the adjacent meniscal tissue. Cells in the superficial zone of the meniscus seem to be active in the repair process. A change in both the phenotype of the cells and the quality of the matrix toward a more hyaline state appears to be an integral part of the remodeling process in the meniscus.     

Role of extracellular matrix in kidney development and repair

Extracellular matrix (ECM) molecules and their receptors exert a dynamic role in cell-matrix interactions during kidney development and repair processes. They provide a physical substratum for the spatial organization of the cells, but also regulate cell growth and proliferation by interacting with growth factors. In addition, they can regulate signal transduction pathways by binding to integrins or by modulating the activity of signaling molecules such as Wnts. ECM and ECM-related molecules control multiple (if not all) steps of kidney development, including ureteric bud branching morphogenesis, mesenchymal condensation, nephron formation, terminal differentiation of renal tubules, and glomerular basement membrane assembly. Their role still needs to be better documented in renal repair. The emergence of conditionally mutated mice for basement membrane components will provide a useful tool to demonstrate further the involvement of ECM and ECM-related proteins in development and repair.     

Temporal expression of the chondrogenic and angiogenic growth factor CYR61 during fracture repair.

The repair of a fractured bone is a complex biological event that essentially recapitulates embryonic development and requires the activity of a number of different cell types undergoing proliferation, migration, adhesion, and differentiation, while at the same time expressing a host of different genes. To identify such genes, we employed differential display and compared messenger RNA (mRNA) populations isolated from postfracture (PF) day 5 calluses to those of intact rat femurs. One such gene in which expression was up-regulated at PF day 5 is identified as CYR61, a member of the CCN family of secreted regulatory proteins. CYR61 is a growth factor that stimulates chondrogenesis and angiogenesis. We show that its mRNA expression during fracture repair is regulated temporally, with elevated levels seen as early as PF day 3 and day 5, rising dramatically at PF day 7 and day 10, and finally declining at PF day 14 and day 21. At the highest peak of expression (PF day 7 and day 10, which correlates with chondrogenesis), CYR61 mRNA levels are approximately 10-fold higher than those detected in intact femurs. Similarly, high protein levels are detected throughout the reparative phase of the callus, particularly in fibrous tissue and periosteum, and in proliferating chondrocytes, osteoblasts, and immature osteocytes. The secreted form of CYR61 also was detected within the newly made osteoid. No labeling was detected in hypertrophic chondrocytes or in mature cortical osteocytes. These results suggest that CYR61 plays a significant role in cartilage and bone formation and may serve as an important regulator of fracture healing.     

Epidermal growth factor receptor expression correlates with histologic grade in resected esophageal adenocarcinoma

Activation of the epidermal growth factor receptor (EGFR) has a role in oncogenesis and may correlate with prognosis. The aim of this study was to examine EGFR expression in esophageal adenocarcinoma and correlate EGFR status with pathologic and clinical prognostic features. An exploratory retrospective review of 38 patients with surgically resected esophageal adenocarcinoma was performed. All patients underwent an esophagogastrectomy with regional lymphadenectomy; 24 patients underwent primary resection and 14 patients had surgery after preoperative chemoradiation therapy. Immunohistochemical analysis was performed on paraffin-embedded tissue samples using an EGFR monoclonal antibody. Low- and moderate-grade tumors were positive for EGFR expression in 2 of 15 patients; poorly differentiated tumors were positive for EGFR expression in 13 of 23 patients (p = 0.02). The median survival was 35 months (confidence interval [CI]: 29–40) for EGFR negative patients (n = 23) and 16 months (CI: 10–22) for EGFR positive patients (n = 13) (p = 0.10). Disease recurred in 3 of 21 EGFR negative patients and 6 of 13 EGFR positive patients (p = 0.06). Poorly differentiated adenocarcinomas of the esophagus demonstrated higher EGFR expression compared to low-grade tumors based upon immunohistochemical analysis. A trend toward improved disease-free and overall survival was seen in EGFR negative patients.     

Optical coherence tomography grading correlates with MRI T2 mapping and extracellular matrix content

Optical coherence tomography (OCT) and T2 mapping are emerging clinical imaging technologies with potential to detect subsurface changes in cartilage retaining a macroscopically intact articular surface. This study tests the hypothesis that OCT correlates with magnetic resonance imaging (MRI) T2 values, and that OCT signal is sensitive to cartilage matrix degeneration. Forty‐five osteochondral cores were harvested from five human tibial plateau explants after MRI T2 mapping. Cores underwent OCT imaging and were graded as follows: A, obvious birefringence; B, no birefringence; C, subsurface voids and/or irregular surface. Extracellular matrix content was determined and cores underwent histologic and polarized light microscopy (PLM) evaluation. Grade B and C cores had 25% higher superficial T2 values (p = 0.047) and 50% higher deep T2 values (p = 0.012) than grade A cores. Grade B and C cores had 36% higher glycosaminoglycan (GAG) content compared to grade A cores (p = 0.009). Histology and PLM demonstrated increased surface irregularity and structural disorganization with increasing OCT grade. OCT grade and T2 value increased with increasing collagen disorganization, suggesting that MRI T2 mapping and OCT are sensitive to changes in collagen structure. Our results demonstrate the ability of OCT and T2 mapping to detect early cartilage degeneration in clinically normal appearing cartilage. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:546–552, 2010     

血吸虫病鼠肝纤维化早期肝脏细胞外基质的改变

以免疫组化法（ＬＳＡＢ法），辅以电镜，观察感染血吸虫尾蚴６、８周小鼠肝脏细胞外基质（ＥＣＭ）中Ⅰ、Ⅲ型胶原、纤粘连蛋白（ＦＮ）、层粘连蛋白（ＬＮ）的表达与分布。发现肝门管区、肝窦壁及中央静脉壁有ＥＣＭ异常聚积，电镜可见Ｄｉｓｓｅ腔有纤维束，可形成门管区纤维化、肝窦毛细血管化和中央静脉硬化。表明ＥＣＭ在血吸虫病性肝纤维化的形成与发展中起重要作用。     

Accelerated repair of cortical bone defects using a synthetic extracellular matrix to deliver human demineralized bone matrix.

Injectable hydrogel and porous sponge formulations of Carbylan-GSX, a crosslinked synthetic extracellular matrix (ECM), were used to deliver human demineralized bone matrix (DBM) in a rat femoral defect model. A cortical, full-thickness 5-mm defect was created in two femurs of each rat. Six rats were assigned to each of five experimental groups (thus, 12 defects per group). The defects were either untreated or filled with Carbylan-GSX hydrogel or sponges with or without 20% (w/v) DBM. Radiographs were obtained on day 1 and at weeks 2, 4, 6, and 8 postsurgery of each femur. Animals were sacrificed at week 8 postsurgery and each femur was fixed, embedded, sectioned, and processed for Masson's Trichrome staining. The bone defects were measured from radiographs and the fraction of bone healing was calculated. The average fractions of bone healing for each group were statistically different among all groups, and all treatment groups were significantly better than the control group. The Carbylan-GSX sponge with DBM was superior to the sponge without DBM and to the hydrogel with DBM. Histology showed that defects treated with the Carbylan-GSX sponge plus DBM were completely filled with newly generated bone tissue with a thickness comparable to native bone. Carbylan-GSX sponge was an optimal delivery vehicle for human DBM to accelerate bone healing.     

Differential expression patterns of the dentin matrix proteins during mineralized tissue formation

Sequential and reciprocal interactions between the oral ectoderm and neural crest-derived mesenchyme are responsible for tooth development. During dentin formation, there are three components that are necessary for proper mineralization, namely, collagen which forms a scaffold, noncollagenous proteins that can specifically bind to the collagen template and function as a mineral nucleator and crystalline calcium phosphate deposited in an ordered manner. It is well established that noncollagenous proteins play an important role during mineralized tissue formation. Here we demonstrate by in situ hybridization techniques that the noncollagenous dentin matrix proteins 1, 2 (DMP1, 2) and dentin sialoprotein (DSP) have characteristic temporal and spatial expression patterns within odontogenic tissues during dentin mineralization. DMP1, DMP2 and DSP mRNA are expressed in the odontoblasts at specific and overlapping time points and are thus presumably used for different functions during dentin formation. In developing rat incisors and molars, high levels of expression of DMP2 mRNA were seen in polarized odontoblasts and preameloblasts, while DSP mRNA was expressed at significantly lower levels and was expressed by highly differentiated odontoblasts. However, their expression was continuously maintained during the mineralization of the organic matrix. In the adult rats, DMP2 and DSP mRNA was also detected in the osteoblasts. The expression of DMP1 mRNA was found to coincide with the start of the mineral nucleation process and gradually decreased during the maturation of the mineralized matrix during odontogenesis. In this study, we have also correlated the expression of these proteins relative to the presence of type I collagen and calcium phosphate crystals. Thus, the temporal and spatial differences between DMP1, DMP2 and DSP might implicate a direct demonstration of the functional difference between these three genes during calcified tissue formation.     

Glycation of extracellular matrix proteins impairs migration of immune cells

The immune response during aging and diabetes is disturbed and may be due to the altered migration of immune cells in an aged tissue. Our study should prove the hypothesis that age and diabetes‐related advanced glycation end products (AGEs) have an impact on the migration and adhesion of human T‐cells. To achieve our purpose, we used in vitro AGE‐modified proteins (soluble albumin and fibronectin [FN]), as well as human collagen obtained from bypass graft. A Boyden chamber was used to study cell migration. Migrated Jurkat T‐cells were analyzed by flow cytometry and cell adhesion by crystal violet staining. Actin polymerization was determined by phalloidin‐Alexa‐fluor 488‐labeled antibody and fluorescence microscopy. We found that significantly fewer cells (50%, p = 0.003) migrated through methylglyoxal modified FN. The attachment to FN in the presence of AGE‐bovine serum albumin (BSA) was also reduced (p < 0.05). In ex vivo experiments, isolated collagen from human vein graft material negatively affected the migration of the cells depending on the grade of AGE modification of the collagen. Collagen with a low AGE level reduced the cell migration by 30%, and collagen with a high AGE level by 60%. Interaction of the cells with an AGE‐modified matrix, but not with soluble AGEs like BSA‐AGE per se, was responsible for a disturbed migration. The reduced migration was accompanied by an impaired actin polymerization. We conclude that AGEs‐modified matrix protein inhibits cell migration and adhesion of Jurkat T‐cells.     

Microsurgical anatomy of membranous layers of the pituitary gland and the expression of extracellular matrix collagenous proteins

Background  

There are several reports about the microanatomical and histological features of sellar and parasellar membranous structures and clinical studies about MMP proteinase as a predictive factor. However, studies on collagen contents of sellar and parasellar membranous structures are limited. We demonstrated the membranous structures surrounding the pituitary gland and defined extracellular matrix (ECM) collagenous proteins, collagen I-IV expression patterns of sellar and parasellar connective tissues.