ISSN:0736-0266    

DOI:10.1002/jor.1100130202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThis study was carried out to quantify the potential associations between material strength and both collagen concentration and pyridinoline collagen crosslink density in the healing medial collateral ligament of the rabbit and to compare these parameters with those of normal ligaments. The right hindlimbs of 24 skeletally mature (12‐month‐old) New Zealand White rabbits were subjected to a standardized 4 mm midsubstance “gap” injury to the medial collateral ligament. The animals were killed in groups of six at postoperative intervals of 3, 6, 14, or 40 weeks, and the femur‐medial collateral ligament‐tibia complexes were mechanically tested in tension to failure. Subsequent to mechanical testing, the failure sites of the ligaments were assessed for concentrations of hydroxyproline and hydroxylysyl pyridinoline. Nine additional rabbits served as age‐matched normal controls. In healing ligaments, normal collagen concentrations were reached in less than 14 weeks, but the hydroxylysyl pyridinoline crosslink densities remained low and were only 45% of the control values after 40 weeks of healing. Similarly, mechanical values remained much less than the controls. Linear regression analysis of data on scar tissue alone showed a moderately strong positive correlation between hydroxyproline concentration and material strength (r2= 0.51, p = 0.0001) but no correlation between crosslink density and strength of scar tissue. A similar pattern of correlation was obtained between the elastic modulus of the scar tissue and the biochemical variables, but the r2values were lower. When control data were included, the results of stepwise regression showed a very high positive correlation between crosslink density and material strength (r2= 0.83, p<0.0001) and discriminant analysis demonstrated crosslink density to be the best classifier of group membership. Combined with hydroxyproline concentration, crosslink values correctly identified healing interval and group 90% of the time. These results suggest that although collagen concentration definitely plays a more important role in determining the early material behaviour of healing medial collateral ligaments, reduced crosslink density in collagen in scar tissue may offer a more specific explanation for the mechanical inferiority, in the rabbit, of healing medial collateral ligaments compared with normal ligame

ISSN:0736-0266    

DOI:10.1002/jor.1100130203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe adhesiveness of fibroblasts from the human anterior cruciate and medial collateral ligaments to the laminin molecule was studied, with particular emphasis on the intrinsic differences between fibroblasts from the two ligaments. Cellular adhesion strength, adhesion area, laminin concentration, and seeding time were examined. Cell adhesion to laminin anchored with poly‐D‐lysine to a cleaned cover glass was measured with a micropipette micromanipulation system after seeding. The adhesion strength of fibroblasts from the anterior cruciate ligament to laminin was greater than and significantly different from that of fibroblasts from the medial collateral ligament, depending on the laminin concentration. Fibroblasts from the anterior cruciate ligament also exhibited an increase in adhesion strength, dependent on laminin concentration of as much as 30 μg/ml, at which the laminin receptors were thought to be saturated. Fibroblasts from the medial collateral ligament did not show such an increase except at laminin concentrations of 5–10 μg/ml. There was no significant difference in adhesion area between fibroblasts from the two ligaments except after 45 minutes at a laminin concentration of 40 μg/ml. For both, the adhesion to laminin showed little correlation to seeding time during periods of as long as 60 minutes. Measurements of adhesion area also failed to show a significant correlation to seeding time for fibroblasts from either ligament at laminin concentrations of 20 and 40 μg/ml. Adhesion strength normalized by adhesion area had no correlation to seeding time. With all times taken into account, however, normalized adhesion strength for fibroblasts from the anterior cruciate ligament was approximately two times greater than and significantly different from that for fibroblasts from the medial collateral ligament at laminin concentrations of 20 and 40 μg/ml. Fibroblasts from the anterior cruciate ligament adhere more strongly to laminin than do those from the medial collateral ligament. This study may prove useful in the understanding of fibroblast adhesion to the basal lamina within the extracellular matrix and may provide insight into the natural healing processes of the anterior cruciate and medial collateral

ISSN:0736-0266    

DOI:10.1002/jor.1100130204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe differential capacities of the anterior cruciate and medial collateral ligaments to heal may be related to differences in cellular function. This study tested the hypothesis that differential expression of integrins occurs in these ligaments after injury. The integrins are a family of cell surface receptors that mediate adhesion, migration, and other cellular functions critical to the healing of a wound. A similar complement and amount of the β1subfamily of integrins are known to be present on the unperturbed anterior cruciate and medial collateral ligaments in humans and rabbits. A partial laceration was surgically created in these two ligaments in 12 anesthetized New Zealand White rabbits. Immunohistochemistry was performed on sections from the ligaments at 1, 3, 7, and 10 days after injury, using monoclonal antibodies directed against the integrin subunits β1, α5, α6, and αv. Between 3 and 7 days, the wounded medial collateral ligament demonstrated a striking increase in staining for the β1, α5, and αvsubunits on the fibroblasts, within the repair site, and on capillary endothelium. Increased staining was most marked for the β1subunit and less marked for the α5and αvsubunits. The α6subunit stained exclusively vascular structures within the healing medial collateral ligament. In marked contrast, the anterior cruciate ligament, which does not mount an effective repair response, demonstrated no comparable alteration of integrin expression from baseline levels. This study demonstrates that increased expression of integrins occurs coincident with wound healing in the medial collateral ligament, whereas this expression remains at baseline levels in the nonhealing wounded anterior cruciate ligament. This observation suggests that a failure to alter expression of integrins subsequent to injury may play a role in the defective healing of the anterior crucia

ISSN:0736-0266    

DOI:10.1002/jor.1100130205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractGrowth factors have been shown to stimulate fibroblast division and thus may influence ligament healing. We analyzed the effects of individual growth factors on the proliferation of fibroblasts from the medial collateral and anterior cruciate ligaments of the rabbitin vitroin order to identify growth factors that might enhance proliferation of fibroblasts and to compare the responses of the fibroblasts from the two ligaments to these growth factors. Through measurement of the uptake of [3H]‐thymidine into DNA, fibroblasts from these ligaments that had been treated with epidermal growth factor and basic fibroblast growth factor were found to proliferate nearly eight times more than control fibroblasts. Additionally, the fibroblasts of both ligaments proliferated at similar rates when exposed to platelet‐derived growth factor‐AA, platelet‐derived growth factor‐BB, basic fibroblast growth factor, insulin‐like growth factor‐1, and interleukin‐1‐alpha. However, epidermal growth factor and transforming growth factor‐beta caused the fibroblasts from the medial collateral ligament to proliferate at a rate 1.3–1.4 times greater than that of fibroblasts from the anterior cruciate ligament. The reverse was true with acidic fibroblast growth factor, which stimulated the fibroblasts from the anterior cruciate ligament to proliferate at a rate 1.3–1.6 times greater than that of fibroblasts from the medial collateral ligament. This study demonstrated that growth factors can stimulate cell division in ligaments and may be effective in enhancing ligament healing but that these differences were not great enough to explain fully the clinical differences observed between healing of the medial collateral and ante

ISSN:0736-0266    

DOI:10.1002/jor.1100130206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effects of immobilization of the knee joint on the mechanical and ultrastructural properties of the anterior cruciate ligament have not been well documented. Our goal was to determine these effects in a rabbit model and to assess the effect of knee flexion angle during immobilization. The knee joint was immobilized in either 170° or 105° of flexion, and new methodologies were utilized to determine the mechanical properties of the anterior cruciate ligament. In specimens from knees that had been immobilized, the cross‐sectional area of the ligament was 74% of the control value. The stress‐strain curve was altered slightly, and the strain at failure increased 32–40%. The modulus and stress at failure did not decrease significantly. There was no significant difference between the mechanical properties of the knees immobilized at 170° and 105° of flexion. Histological and ultrastructural evaluation demonstrated changes in the shape and intracellular makeup of the fibroblasts from the ligament after immobilization. This cellular response may account for the alterations in the mechanical properties of the anterior cruciate

ISSN:0736-0266    

DOI:10.1002/jor.1100130207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractSince meniscal healing is region‐specific, we studied the regional (peripheral compared with central) response of meniscal explants to human, recombinant platelet‐derived growth factor‐AB. Mensical explants from the hindlimbs of both knees of mature sheep were sectioned and were cultured with variable doses of human, recombinant platelet‐derived growth factor‐AB, and incorporation of [3H]‐thymidine was measured. The mitogenic response was measured at different times in culture (48 or 96 hours) and by location (lateral or medial). In the absence of the growth factor, the peripheral third of both menisci incorporated 10‐fold more [3H]‐thymidine on a weight basis than did the central two‐thirds. Cellularity was equivalent in the two regions. Doses of less than 100 ng/ml of growth factor produced either no stimulation or a variable response. A dose of 100 ng/ml resulted in consistent, significant (p<0.05) stimulation in all groups in the peripheral region, and a dose of 200 ng/ml provided more than a 2.5‐fold increase. Multiple‐factor analysis of variance demonstrated that there were no significant differences between experiments, times in culture, or menisci. The central region did not respond to stimulation with the growth factor at any of the doses tested. These data suggest that regional differences (peripheral compared with central) in responsiveness to human, recombinant platelet‐derived growth factor‐AB may reflect a different level of signal transduction machinery for growth factor receptors and distinct fibrochondrocyte populations. These findings are consistent with the variable healing capcity of the meniscal regionsin vivoand suggest a pharmacological means to promote the repair of the p

ISSN:0736-0266    

DOI:10.1002/jor.1100130208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractMandibular condyles in organ culture commonly have been used as a model system for examination of the factors that influence skeletal growth and development. The work reported here complements previously published histological studies by providing quantitative temporal information on growth and matrix accumulation. Condyles maintained for as long as 5 weeks in serum‐free and 1% serum‐supplemented culture media were found to remain viable and metabolically active as demonstrated by continued dimensional growth as well as cell and matrix accumulation. Growth occurred by a combination of cell proliferation, matrix synthesis and accumulation, and cell hypertrophy (with the latter two mechanisms dominating). Increase in tissue volume correlated directly with increased glycosaminoglycan content; both increased 7‐fold over 5 weeks. In comparison with serum‐free culture, after 35 days in medium containing 1% serum, glycosaminoglycan content was 24% lower and collagen content was 36% higher, whereas dry weight, condyle length, and DNA content were not significantly different; in addition, histological observation suggested that, for samples cultured with serum, chondrogenic phenotype had been lost from some regions. The temporal behavior for all growth parameters exhibited a transient phase 1–2 weeks in duration followed by a steady‐state period in which dimenssions and tissue constituents or content increased at a constant or near constant rate. Comparison of the rates of incorporation of [35S]sulfate with glycosaminoglycan content in serum‐free cultures suggests that the loss of glycosaminoglycan occurs only initially or is negligible; therefore, under these baseline conditions, cartilage glycosaminoglycan content reflects the biosynthetic rate. The high degree of reproducibility seen during steady‐state growth suggests that these data provide reliable baseline information and further supports the notion that this model system is useful for investigation of the effects of specific physical factors onin vitrogrowth

ISSN:0736-0266    

DOI:10.1002/jor.1100130209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractLongitudinal growth of bone involves a complex sequence of cellular events in the cartilaginous epiphysis. Whole blood serum has been shown previously to be a potent stimulus to the cells of the growth plate, as demonstrated by its ability to activate the inositol phosphate‐calcium second messenger system resulting in a rise in intracellular Ca2+. By manipulating the preparation of serum to functionally separate it into its constituent parts, we have shown that the processes of platelet lysis and activation of the clotting cascade are responsible for the generation of factors that stimulate this signaling mechanism in isolated bovine growth plate chondrocytes. Through a subsequent trial of bioactive agents generated in these processes, we identified and partially characterized several novel agonists of growth plate chondrocytes: adenosine triphosphate and adenosine diphosphate, the purine energy substrates, and bradykinin, the bioactive peptide generated in a side reaction of the clotting cascade, each induces a rise in intracellular Ca2+via release from intracellular ion stores. Additionally, the three distinct isoforms of platelet‐derived growth factor (AA, AB and BB), also released on platelet lysis, were compared with respect to their ability to stimulate the inositol phosphate‐calcium second messenger system in growth plate chondro

ISSN:0736-0266    

DOI:10.1002/jor.1100130210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe structure of chondroitin sulfate on aggrecan isolated from the rib and proximal tibial growth plates of bovine fetuses was investigated, and the previously reported increase in the hydrodynamic size of chondroitin sulfate chains between the reserve and hypertrophic zones of the rib was confirmed in the tibial growth plate. Superose 6 gel chromatography, calibrated for chondroitin sulfate chain length by monosaccharide analysis, showed that the average molecular mass of chondroitin sulfate in the reserve and maturing zones of both growth plates was 21,600 and 30,400, respectively. Determination by capillary zone electrophoresis of the disaccharide composition of chains following chondroitinase digestion showed that ΔDi‐0S, ΔDi‐4S, and ΔDi‐6S together accounted for more than 98% of the disaccharides in the digests from all zones of both growth plates; Δdisulfated and Δtrisulfated disaccharides were not detected. Furthermore, this analysis revealed a gradient in chondroitin sulfate composition from the reserve to the hypertrophic zone, characterized by a marked increase in the content of ΔDi‐6S (from about 32% to about 52%) and a marked decrease in the content of ΔDi‐4S (from about 53% to about 35%). Moreover, this altered pattern of sulfation was detected on chains of all sizes in the hypertrophic zone, suggesting that a proportion of the reserve zone aggrecan might be removed and replaced with aggrecan rich in chondroitin‐6‐sulfate synthesized during the proliferative and maturation stages of the resident chondrocytes. These data are discussed in relation to the biosynthetic mechanisms that control chondroitin sulfate chain length and sulfation on aggrecan and their modification during chondrocyte proliferation, maturation, and hypertrophy

ISSN:0736-0266    

DOI:10.1002/jor.1100130211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY