Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Collagen X is produced by hypertrophic cartilage undergoing endochondral ossification. Transgenic mice expressing defective collagen X under the control of 4.7- or 1.6-kb chicken collagen X regulatory sequences yielded skeleto-hematopoietic defects (Jacenko O, LuValle P, Olsen BR: Spondylometaphyseal dysplasia in mice carrying a dominant-negative mutation in a matrix protein specific for cartilage-to-bone transition. Nature 1993, 365:56-61; Jacenko O, Chan D, Franklin A, Ito S, Underhill CB, Bateman JF, Campbell MR: A dominant interference collagen X mutation disrupts hypertrophic chondrocyte pericellular matrix and glycosaminoglycan and proteoglycan distribution in transgenic mice. Am J Pathol 2001, 159:2257-2269; Jacenko O, Roberts DW, Campbell MR, McManus PM, Gress CJ, Tao Z: Linking hematopoiesis to endochondral ossification through analysis of mice transgenic for collagen X. Am J Pathol 2002, 160:2019-2034). Current data indicate that the hematopoietic abnormalities do not result from extraskeletal expression of endogenous collagen X or the transgene. Organs from mice carrying either promoter were screened by immunohistochemistry, in situ hybridization, and Northern blot; transgene and mouse collagen X proteins and messages were detected only in hypertrophic cartilage. Likewise, reverse transcriptase-polymerase chain reaction revealed both transgene and mouse collagen X amplicons only in the endochondral skeleton of mice with the 4.7-kb promoter; however, in mice with the 1.6-kb promoter, multiple organs were transgene-positive. Collagen X and transgene amplicons were also detected in marrow, but likely resulted from contaminating trabecular bone; this was supported by reverse transcriptase-polymerase chain reaction analysis of rat tibial zones free of trabeculae. Our data demonstrate that in mice, the 4.7-kb chicken collagen X promoter restricts transcription temporo-spatially to that of endogenous collagen X, and imply that murine skeleto-hematopoietic defects result from transgene co-expression with collagen X. Moreover, the 4.7-kb hypertrophic cartilage-specific promoter could be used for targeting transgenes to this tissue site in mice.
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PMID:Chicken collagen X regulatory sequences restrict transgene expression to hypertrophic cartilage in mice. 1474 55

The biological mechanisms underlying bone-titanium integration and biomechanical properties of the integrated bone are poorly understood. This study assesses intrinsic biomechanical properties of mineralized tissue cultured on titanium having different surface topographies. The osteoblastic phenotypes associated with mineral deposition and collagen synthesis underlying the biomechanical modulation are also reported. Rat bone marrow-derived osteoblastic cells were cultured either on the machined titanium disc or acid-etched titanium disc. Nano-indentation study of day 28 culture revealed that the mineralized tissue on the acid-etched surface shows 3-3.5 times greater hardness than that on the machined surface (p < 0.01). Elastic modulus of the mineralized tissue was also 2.5-3 times greater on the acid-etched surface than on the machined surface (p < 0.01). After 28 days of culture, mineralized nodule area was significantly lower on the acid-etched surface than on the machined surface (p = 0.0105), while total calcium deposition did not differ between the two surfaces, indicating denser mineral deposition on the acid-etched surface. Osteopontin and osteocalcin gene expressions assayed by the reverse transcriptase-polymerase chain reaction were upregulated in the acid-etched titanium culture. Collagen synthesis measured by Sirius red stain-based colorimetry was 1.5-10 times higher on the acid-etched surface than on the machined surface in the initial culture period of day 1 to day 14 (p < 0.0001). The amount of collagen synthesis corresponded with the enhanced gene expression of prolyl 4-hydroxylase, a key enzyme for post-translational modification of collagen chains. Scanning electron microscopic images revealed that tissue cultured on the acid-etched titanium exhibited plate-like, compact surface morphology, while the tissue on the machined titanium appeared porous and was covered by fibrous and punctate structures. We conclude that culturing osteoblasts on rougher titanium surfaces enhances hardness and elastic modulus of the mineralized tissue, associated with condensed mineralization, accelerated collagen synthesis, and upregulated expression of selected bone-related genes.
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PMID:Enhanced intrinsic biomechanical properties of osteoblastic mineralized tissue on roughened titanium surface. 1565 12

Cardiac hypertrophy in response to hyperthyroidism is well known. However, the effects on cardiac microcirculation are still controversial in this model. The present study evaluated the effects of acute administration of two different thyroxine (T4) dose levels on the angiogenic response in the myocardium. Capillary density (CD), the CD to fiber density (FD) ratio (CD/FD), and intercapillary distance (ICD) were assessed, as was ventricle weight (VW) to body weight (BW) ratio (VW/BW). Collagen I and III messenger ribonucleic acid (mRNA) expression and VEGF-A expression were also determined by reverse transcriptase polymerase chain reaction (RT-PCR). Immunohistochemical detection of proliferating cell nuclear antigen (PCNA) expression in endothelial cell nuclei was also carried out. We simulated an acute hyperthyroidism situation in male Wistar rats by daily intraperitoneal injection of T4 (0.025 or 0.1 mg kg(-1) day(-1)) for 7 days. Hemodynamic parameters showed that T4 did not alter systolic blood pressure (SBP) but significantly increased heart rate (HR). Both T4 doses significantly increased VW. Morphologically, the higher T4 dose resulted in a 33% greater myocardial mass, which was not accompanied by alterations in collagen I and III mRNA expression. The CD and CD/FD parameters were significantly lower in the hyperthyroid rats treated with the higher dose than in the control animals, and PCNA-labeling analysis indicated total absence of marked capillary growth. However, although the acute treatment with T4 did not induce any alteration in capillary number and endothelial cell proliferation, the vascular endothelial growth factor (VEGF)-A mRNA and protein expression were significantly increased with the higher T4 dose. These data indicate that the cardiac hypertrophy induced by acute treatment with thyroid hormone precedes the angiogenic process, which probably occurs later.
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PMID:Early cardiac hypertrophy induced by thyroxine is accompanied by an increase in VEGF-A expression but not by an increase in capillary density. 1644 Jan 99

This study investigated the differential effects of ramped and steady applications of cyclic hydrostatic pressure (CHP) on chondrogenic differentiation of bone marrow-derived human mesenchymal stem cells (hMSCs) in 3-dimensional culture in the absence of transforming growth factor-beta (TGF-beta). A custom hydrostatic pressure system was designed and manufactured. hMSCs were seeded in agarose and exposed to steady (7.5 MPa) or ramped (1 MPa to 7.5 MPa over a 14-day period) CHP for 4 h/d at f = 1 Hz for 14 days. Real-time reverse transcriptase polymerase chain reaction analysis was performed on days 0, 4, 9, and 14 to determine changes in messenger ribonucleic acid (mRNA) expression levels of Sox9, aggrecan, collagen I, and collagen II. Collagen II and aggrecan mRNA expression remained unchanged. Collagen I increased at day 4 in CHP specimens before decreasing to levels at or below same-day unloaded controls at days 9 and 14. On average, ramped and steady regimens of CHP increased Sox9, with the largest upregulation occurring at day 4 in response to steady pressure. These findings indicate that hydrostatic pressure may induce chondrogenesis in hMSC-seeded agarose constructs without TGF-beta, and that hMSCs are capable of withstanding high initial pressures that may initiate chondrogenesis faster than lower pressures.
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PMID:Differential effects on messenger ribonucleic acid expression by bone marrow-derived human mesenchymal stem cells seeded in agarose constructs due to ramped and steady applications of cyclic hydrostatic pressure. 1751 10

The creation of tissue-engineered constructs with autologous cells is a central goal in regenerative medicine. With respect to ligament replacement, we have evaluated the influences of matrix and growth factors on hMSCs (human mesenchymal stromal cells). hMSCs were seeded in two different 3D (three-dimensional) systems consisting of either a collagen type I gel or a synthetic PLA [poly-(L-lactic acid)] scaffold. After cultivation for 14 days with rhTGFbeta1 (recombinant human transforming growth factor beta1), rhPDGF-BB (recombinant human platelet-derived growth factor homodimer of B-chain) or rhBMP13 (recombinant human bone morphogenetic protein 13), we assessed the proliferation potential, mRNA expression and protein expression of various matrix-interacting and matrix-degrading molecules by quantitative real-time RT (reverse transcriptase)-PCR, immunohistochemistry and gelatin zymography in comparison with unstimulated cells. Cellular reactions to the type of scaffold or soluble factors could be found in the expression of tenascin-C as well as integrin subunits alpha1, alpha3 and beta1. Collagen type X expression was induced by 3D culture and stimulated by rhTGFbeta1 on PLA. The expression of MMP-1 (matrix metalloproteinase 1) tended to increase, and MMP-13 was induced in the collagen culture system. The activation of MMP-2 was stimulated by the cultivation of MSCs within the collagenous matrix. These results demonstrated that various interactive effects of growth factors and scaffolds influence the cell-biological behaviour of MSCs. It is important to take these complex interactions, which partly differ from differentiated cells, into account in further tissue-engineering approaches.
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PMID:Interactive effects of growth factors and three-dimensional scaffolds on multipotent mesenchymal stromal cells. 1764 Jan 72

The knee meniscus contains a mixed population of cells that exhibit fibroblastic as well as chondrocytic characteristics. Tissue engineering studies and future therapies for the meniscus require a large population of cells that are seeded on scaffolds. To achieve this, monolayer expansion is often used as a technique to increase cell number. However, the phenotype of these cells may be significantly different from that of the primary population. The objective of this study was to investigate changes in meniscal fibrochondrocytes at the gene expression level over four passages using quantitative real-time reverse transcriptase polymerase chain reaction. Cells from the inner two-thirds of bovine medial menisci were used. Four extracellular matrix (ECM) molecules, commonly found in the meniscus, were investigated, namely collagen I, collagen II, aggrecan and cartilage oligomeric matrix protein (COMP). In addition, primary and passaged meniscus fibrochondrocytes were placed on surfaces coated with collagen I or aggrecan protein to investigate whether any gene expression changes resulting from passage could be reversed. Collagen I expression was found to increase with the number of passages, whereas collagen II and COMP expression decreased. Collagen I and aggrecan surface coatings were shown to downregulate and upregulate collagen I and COMP expression levels, respectively, in passaged cells. However, decreases in collagen II expression could not be reversed by either protein coating. These results indicate that although monolayer expansion results in significant changes in gene expression in meniscal fibrochondrocytes, protein coatings may be used to regain the primary cell expression of several ECM molecules.
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PMID:Passage and reversal effects on gene expression of bovine meniscal fibrochondrocytes. 1785 86

The focus of this study was a new adult pluripotent cell derived from human peripheral blood monocytes identified as a "programmable cell of monocytic origin" (PCMO). In contrast to bone marrow-derived stem cells, these cells can be harvested from peripheral venous blood without aspiration of the bone marrow and have multilineage potential comparable to that of mesenchymal stem cells (MSC). The aim of this study was to evaluate the potential of PCMOs to differentiate into collagen type II-producing chondrocytes using various extrinsic cues (TGFbeta-1, IGF-1, BMP-2, and BMP-7). Collagen type I and II proteins were localized using immunohistochemistry and quantified by enzyme-linked immunosorbent assays (ELISA). The shape of the differentiating PCMOs was monitored with electron microscopy. Collagen type I and II messenger RNA expression was analyzed using real-time reverse transcriptase-polymerase chain reaction (RT PCR) and regular RT PCR. Immunohistochemistry revealed a strong accumulation of collagen type II after a 6-week incubation period with BMP-2, BMP-7, TGF-beta, IGF-I, and TGF-beta, and IGF-1. Collagen type I was only mildly induced by the applied stimulants. Electron microscopy findings showed a shift from a monocyte-like structure to a chondrocyte-like structure after 2 weeks of stimulation. Stimulation of PCMOs with BMP-2, BMP-7, TGF-beta, IGF-I, and TGF-beta, and IGF-1 induced a chondrogenic differentiation with continuous expression of collagen type II mRNA and protein over several weeks time. Collagen type I and II expression in undifferentiated PCMOs or in control cells incubated without any stimulant was not detected. PCMOs have the potential to differentiate into collagen type II synthesizing chondrocytes. The ability to reprogram and differentiate PCMOs from peripheral blood into sizable quantities might enable their clinical application in cartilage repair after mechanical injury or in cases of osteoarthritis.
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PMID:Programmable cells of monocytic origin (PCMO): a source of peripheral blood stem cells that generate collagen type II-producing chondrocytes. 1796 14

The aim of this study was to test the efficacy of transplantation of bone marrow-derived mesenchymal stem cells (BMSCs) expressing human platelet-derived growth factor A (hPDGF-A) and human beta-defensin2 (hBD2) in accelerating wound healing of combined radiation-wound injury. Recombinant adenovirus vector simultaneously expressing hPDGF-A and hBD2 was constructed and packaged into virus particles that were used to infect rat BMSCs. The expressions of the exogenous in BMSCs were determined by reverse transcriptase (RT)-PCR and western -blot, whereas the functions were determined by cell counting kit (CCK), wound-healing assay on monolayer cells and Kleihauer-Betke (K-B) test. The recombinant adenovirus-infected BMSCs (1 x 10(7)) were subcutaneously transplanted into the wound bed and wound healing was observed for the indicated duration. Rats with combined total body ionizing radiation (6 Gy) and full-thickness skin excision (2% of total body surface area) wound injury were treated with normal BMSCs (group N), BMSCs infected with recombinant adenovirus expressing hPDGF-A and hBD2 (group T) or phosphate-buffered saline (PBS) (group S). The mean wound healing time, percentage of residual wound area (n=8), blind pathological observation (n=3 per time point for each group) and the amount of bacteria under the scar (the same sample was used in the pathological study, n=3) were used for evaluating wound healing. Collagen was visualized by Sirius red staining. Exogenous hPDGF-A and hBD2 were expressed in BMSCs as indicated by RT-PCR and western blot. Faster wound healing of scratched monolayer cells was demonstrated in hPDGF-A/hBD2 gene-modified BMSCs (T-MSCs) when compared with the corresponding control (P<0.01), and conditioned culture medium from T-MSCs showed stimulative effect on BMSC proliferation and in vitro antibiotic effect in the presence of trypsin. Neutralizing antibody interfering in vitro demonstrated that secreted hPDGF-A was the main factor stimulating cell proliferation. In an in vivo test, the radiation-wound combined injury exhibited shorter healing time (21 days). Histologically, there was better granulation formation/maturation and skin-dependent regeneration, as well as more collagen deposition (P<0.01) in rats of group T than in other groups. The deposition and remodeling of collagen in wounds were ranked in the following order: group T>group N>group S. Significantly less bacterial colony formation in the cultured under-scar samples in the rats of group T was observed (P<0.01) at day 7 and thereafter when compared with control. After transplantation, the BMSCs expressed exogenous genes in the wound for at least 2 weeks, as indicated by the reporter gene. Topical transplantation of gene-modified BMSCs promoted wound healing, which may be the benefit of the secretion of antibacterial hBD2 and mitogenic hPDGF-A, resulting in better granulation formation/maturation and skin appendage regeneration in wound. These data demonstrated the potential application of this combination of cell therapy and gene therapy on refractory wound healing.
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PMID:Transplantation of BMSCs expressing hPDGF-A/hBD2 promotes wound healing in rats with combined radiation-wound injury. 1870 14

In vivo cartilage reconstruction at an ectopic site was not successful in immunocompetent animals, possibly because of immunoreaction and the failure of material design. A diffusion chamber, which has been predominantly adopted to study cell differentiation, was effective in preventing host immune rejection, host cell invasion, and vascular invasion. In this study, we proposed to regenerate ectopic cartilage tissue in rabbits by implanting a diffusion-chamber system subcutaneously for 8 weeks. Inside the chamber, biomimetic scaffolds loaded with allogenous chondrocytes from newborn rabbits were enclosed. Tissue with characteristics of cartilage was formed inside the chamber with collagen gel as a scaffold, which was demonstrated using histological, immunohistochemical, and reverse transcriptase polymerase chain reaction assays. In contrast, for implant without diffusion chamber, vascular invasion was observed and results showed much less expression of cartilage extracellular matrix (ECM). Collagen type I hydrogel and sponge were compared as scaffolds. No cartilage tissue was found in the collagen sponge inside the chamber, presumably because of the different cell-seeding characteristics of gel. In addition, allogenous chondrocytes were adopted as a cell resource and were proved viable for the regeneration of cartilage tissue in this model. The results revealed that the diffusion chamber and scaffold design are both important in providing a more favorable biomimetic microenvironment for the formation of cartilage in vivo at an ectopic site, even with allogenous cells. Moreover, preliminary repair of a cartilage defect using the engineered tissue for 4 weeks showed the growth of new cartilage, obtaining a satisfactory interface with the original cartilage inside the defect. The model of engineering cartilage in vivo was proven to be useful. This study is the preliminary exploration for the reconstruction of ectopic cartilage in an immunocompetent host to be applied for cartilage repair. It may provide a valuable reference for the clinical application of cartilage repair.
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PMID:In vivo cartilage engineering with collagen hydrogel and allogenous chondrocytes after diffusion chamber implantation in immunocompetent host. 1932 67

To investigate the mechanism how Transforming growth factor-beta(TGF-beta) represses Interleukin-1beta (IL-1beta)-induced Proteinase-Activated Receptor-2 (PAR-2) expression in human primary synovial cells (hPSCs). Human chondrocytes and hPSCs isolated from cartilages and synovium of Osteoarthritis (OA) patients were cultured with 10% fetal bovine serum media or serum free media before treatment with IL-1beta, TGF-beta1, or Connective tissue growth factor (CTGF). The expression of PAR-2 was detected using reverse transcriptase-polymerase chain reaction (RT-PCR) and western blotting. Collagen zymography was performed to assess the activity of Matrix metalloproteinases-13 (MMP-13). It was demonstrated that IL-1beta induces PAR-2 expression via p38 pathway in hPSCs. This induction can be repressed by TGF-beta and was observed to persist for at least 48 hrs, suggesting that TGF-beta inhibits PAR-2 expression through multiple pathways. First of all, TGF-beta was able to inhibit PAR-2 activity by inhibiting IL-1beta-induced p38 signal transduction and secondly the inhibition was also indirectly due to MMP-13 inactivation. Finally, TGF-beta was able to induce CTGF, and in turn CTGF represses PAR-2 expression by inhibiting IL-1beta-induced phospho-p38 level. TGF-beta could prevent OA from progression with the anabolic ability to induce CTGF production to maintain extracellular matrix (ECM) integrity and to down regulate PAR-2 expression, and the anti-catabolic ability to induce Tissue inhibitors of metalloproteinase-3 (TIMP-3) production to inhibit MMPs leading to avoid PAR-2 over-expression. Because IL-1beta-induced PAR-2 expressed in hPSCs might play a significantly important role in early phase of OA, PAR-2 repression by exogenous TGF-beta or other agents might be an ideal therapeutic target to prevent OA from progression.
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PMID:TGF-beta inhibits IL-1beta-activated PAR-2 expression through multiple pathways in human primary synovial cells. 1985 94


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