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J Lab Clin Med. 2002 Nov;140(5):329-35.
Nerve growth factor stimulates fibronectin-induced fibroblast migration.
Kohyama T, Liu X, Wen FQ, Kobayashi T, Abe S, Ertl R, Rennard SI.
Department of Respiratory Medicine, University of Tokyo, Japan.
Nerve growth factor (NGF), a polypeptide with well-known actions on neurons, is believed to play a role in the process of tissue repair. The aim of this study was to investigate the effect of NGF on human fetal lung fibroblast (HFL-1)-mediated type I collagen gel contraction and on chemotaxis of the cells with the use of the blind-well chamber technique. Neither collagen gel contraction nor the chemotaxis of HFL-1 cells was affected by NGF (100 ng/mL) alone. However, NGF significantly increased HFL-1 chemotaxis to human fibronectin (20 microg/mL) and platelet-derived growth factor-BB (PDGF-BB, 10 ng/mL), by 41.8% +/- 11.4% and 47.7% +/- 6.6%, respectively. Checkerboard analysis showed stimulation of both chemotaxis and chemokinesis. NGF appeared to affect the rate of migration. After 12 hours, control cells had migrated as much as NGF-treated cells. The effect of NGF was blocked by the tyrosine kinase receptor A inhibitor K-252a, suggesting that the biological action of NGF on fibroblast chemotaxis is mediated through this tyrosine kinase receptor. Our findings suggest that by increasing the rate at which fibroblasts migrate in response to chemoattractants, NGF can modulate the speed and intensity of a repair response and may therefore represent a valid therapeutic target for a variety of diseases.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12434134&dopt=Abstract
J Orthop Res. 2000 Jul;18(4):537-45.
Tenascin-C in tendon regions subjected to compression.
Mehr D, Pardubsky PD, Martin JA, Buckwalter JA.
Iowa City Veterans Administration Medical Center and Department of Orthopaedics, University of Iowa, USA.
Tendon regions subjected almost exclusively to tension differ from regions subjected to high levels of compression as well as tension. Regions not exposed to compression consist primarily of spindle-shaped fibroblasts surrounded by densely packed longitudinally oriented collagen fibrils formed principally from type-I collagen. In contrast, regions subjected to compression have a fibrocartilagenous structure and composition: they consist of spherical cells surrounded by a matrix containing hyaline cartilage proteoglycans (aggrecan) and type-II collagen as well as type-I collagen. Reducing their adhesion to the matrix may help cells in the latter regions establish and maintain a spherical shape and minimize their deformation when the tissue is subjected to mechanical stress. We hypothesized that expression of tenascin-C, an anti-adhesive protein, is part of the adaptation of tendon cells to compression that helps establish and maintain fibrocartilagenous regions. To test this hypothesis, we compared segments of bovine flexor tendons subjected to repetitive compression (distal) with segments that are not subjected to compression (proximal) to determine whether they differed in tenascin-C content and expression. RNA and protein analyses showed that tenascin-C expression was elevated in the distal tendon. Tendon cells from the distal segment expressed more tenascin-C mRNA than did cells from the proximal segments for as long as 4 days in cell culture, indicating that increased tenascin-C expression is a relatively stable feature of the distal cells. Moreover, purified tenascin-C inhibited the attachment of cultured tendon cells to fibronectin. These observations support the hypothesis that tenascin-C expression is a cellular adaptation to compression that helps establish and maintain fibrocartilagenous regions of tendons by decreasing cell-matrix adhesion.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11052489&dopt=Abstract
J Orthop Res. 2000 Jul;18(4):557-64.
Migration of cells from human anterior cruciate ligament explants into collagen-glycosaminoglycan scaffolds.
Murray MM, Martin SD, Spector M.
Department of Orthopaedic Surgery, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA. mmmurraartners.org
Regeneration of the human anterior cruciate ligament after complete rupture offers several theoretical advantages over reconstruction, including maintenance of the complex insertion sites and fan-shape of the ligament and preservation of remaining proprioceptive fibers within the ligament substance. Well vascularized connective tissues, such as dermis, heal as a result of migration of fibroblasts into a provisional scaffold, the fibrin clot. Wound closure is subsequently facilitated by a contractile cell phenotype. This study was designed to determine if fibroblasts intrinsic to the human anterior cruciate ligament were capable of migrating from their native extracellular matrix onto an adjacent provisional scaffold in vitro. Another objective was to determine whether any of the cells that successfully migrated into the scaffold expressed the contractile actin isoform, alpha-smooth muscle actin, associated with wound contraction in other tissues. The results demonstrated that the cells intrinsic to the human anterior cruciate ligament were able to migrate into a collagen-glycosaminoglycan scaffold, bridging a gap between transected fascicles in vitro. As a result of this cell migration and proliferation, areas in the scaffold contained cell number densities similar to those seen in the human anterior cruciate ligament in vivo. No extracellular matrix or tissue formation was seen in the gap between directly apposed transected ends of the anterior cruciate ligament explants cultured without an interposed collagen-glycosaminoglycan scaffold. The fascicle-collagen-glycosaminoglycan-fascicle constructs and the fascicle-fascicle explants displayed minimal adherence after 6 weeks in culture. Any disruption in the contact area between explant and scaffold, even as small a gap as 50 microm, prevented cell migration from the explant to the collagen-glycosaminoglycan scaffold at the area of loss of contact. All cells that migrated into the scaffold at early time periods expressed the alpha-smooth muscle actin isoform. These results demonstrate that cells that migrate into and proliferate within the collagen-glycosaminoglycan matrix have contractile potential as reflected in their expression of the alpha-smooth muscle actin isoform. The role of these contractile cells in the healing process warrants further investigation. Moreover, this study demonstrates the potential of cells intrinsic to the human anterior cruciate ligament to migrate into collagen-glycosaminoglycan scaffolds that may ultimately be investigated as implants to facilitate ligament healing and regeneration.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11052491&dopt=Abstract
J Orthop Res. 2000 Jul;18(4):585-92.
Increased matrix synthesis following adenoviral transfer of a transforming growth factor beta1 gene into articular chondrocytes.
Shuler FD, Georgescu HI, Niyibizi C, Studer RK, Mi Z, Johnstone B, Robbins RD, Evans CH.
Departments of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pennsylvania, USA.
Monolayer cultures of lapine articular chondrocytes were transduced with first-generation adenoviral vectors carrying lacZ or transforming growth factor beta1 genes under the transcriptional control of the human cytomegalovirus early promoter. High concentrations of transforming growth factor beta1 were produced by chondrocytes following transfer of the transforming growth factor beta1 gene but not the lacZ gene. Transduced chondrocytes responded to the elevated endogenous production of transforming growth factor beta1 by increasing their synthesis of proteoglycan, collagen, and noncollagenous proteins in a dose-dependent fashion. The increases in collagen synthesis were not accompanied by alterations in the collagen phenotype; type-II collagen remained the predominant collagen. Transforming growth factor beta1 could not, however, rescue the collagen phenotype of cells that had undergone phenotypic modulation as a result of serial passaging. These data demonstrate that chondrocytes can be genetically manipulated to produce and respond to the potentially therapeutic cytokine transforming growth factor beta1. This technology has a number of experimental and therapeutic applications, including those related to the study and treatment of arthritis and cartilage repair.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11052495&dopt=Abstract
J Orthop Res. 2000 Jul;18(4):637-46.
Pulsed electromagnetic field stimulation of MG63 osteoblast-like cells affects differentiation and local factor production.
Lohmann CH, Schwartz Z, Liu Y, Guerkov H, Dean DD, Simon B, Boyan BD.
Department of Orthopaedics, The University of Texas Health Science Center at San Antonio, 78229-3900, USA.
Pulsed electromagnetic field stimulation has been used to promote the healing of chronic nonunions and fractures with delayed healing, but relatively little is known about its effects on osteogenic cells or the mechanisms involved. The purpose of this study was to examine the response of osteoblast-like cells to a pulsed electromagnetic field signal used clinically and to determine if the signal modulates the production of autocrine factors associated with differentiation. Confluent cultures of MG63 human osteoblast-like cells were placed between Helmholtz coils and exposed to a pulsed electromagnetic signal consisting of a burst of 20 pulses repeating at 15 Hz for 8 hours per day for 1, 2, or 4 days. Controls were cultured under identical conditions, but no signal was applied. Treated and control cultures were alternated between two comparable incubators and, therefore, between active coils; measurement of the temperature of the incubators and the culture medium indicated that application of the signal did not generate heat above the level found in the control incubator or culture medium. The pulsed electromagnetic signal caused a reduction in cell proliferation on the basis of cell number and [3H]thymidine incorporation. Cellular alkaline phosphatase-specific activity increased in the cultures exposed to the signal, with maximum effects at day 1. In contrast, enzyme activity in the cell-layer lysates, which included alkaline phosphatase-enriched extracellular matrix vesicles, continued to increase with the time of exposure to the signal. After 1 and 2 days of exposure, collagen synthesis and osteocalcin production were greater than in the control cultures. Prostaglandin E2 in the treated cultures was significantly reduced at 1 and 2 days, whereas transforming growth factor-beta1 was increased; at 4 days of treatment, however, the levels of both local factors were similar to those in the controls. The results indicate enhanced differentiation as the net effect of pulsed electromagnetic fields on osteoblasts, as evidenced by decreased proliferation and increased alkaline phosphatase-specific activity, osteocalcin synthesis, and collagen production. Pulsed electromagnetic field stimulation appears to promote the production of matrix vesicles on the basis of higher levels of alkaline phosphatase at 4 days in the cell layers than in the isolated cells, commensurate with osteogenic differentiation in response to transforming growth factor-beta1. The results indicate that osteoblasts are sensitive to pulsed electromagnetic field stimulation, which alters cell activity through changes in local factor production.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11052501&dopt=Abstract
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