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Biomedical subjects

D Amiel

Publications and source records attributed to D Amiel.

At least 55 records · Page 3Linked to original sources
PubMed1998

Histomorphometric and biochemical effect of various hyaluronans on early osteoarthritis.

OBJECTIVE: To evaluate, histomorphometrically and biochemically, different protective effects of clinically used hyaluronans (HA). METHODS: An experimental osteoarthritis (OA) model was applied to 132 mature NZW rabbits by resecting the unilateral anterior cruciate ligament (ACL). The other knee, where ACL remained intact, served as the control. We used native HA with different molecular weights, HA-50 (MW 5-7.3 x 10(5)), HA-80 (MW 8 x 10(5)), HA-360 (MW 3.6 x 10(6)), and crosslinked HA (HA-CL). HA were injected into the joint once a week for 5 weeks (HA-50, HA-80, HA-360) or 3 weeks (HA-CL) beginning 4 weeks after ACL transection. Histomorphometric and biochemical assessment was performed 9 weeks post-transection for both the HA treated and nontreated groups. RESULTS: In gross morphological observation, cartilage degeneration was suppressed in HA treated groups, and this effect was superior in the groups receiving either HA-80 or HA-CL. Histomorphometric and biochemical analyses of the articular cartilage revealed similar results: the HA-80 and HA-CL groups showed no significant differences between the ACL transection and the control knees by histomorphometric variables, while the nontreated groups revealed significant degeneration. These evaluations were done in unblinded fashion. Biochemical analyses, including DNA synthesis in the synovium, also showed that articular cartilage and synovium in the HA-80 and HA-CL groups did not present significant changes compared to controls. CONCLUSION: In quantitative evaluation of this short term study using the OA model, native HA-80 and HA-CL presented a superior cartilage protective effect compared to the other native HA.

Animals↗
PubMed1998

Growth factor expression in healing rabbit medial collateral and anterior cruciate ligaments.

Exogenously administered growth factors such as platelet-derived growth factor (PDGF), transforming growth factor beta (TGF-beta) and basic fibroblast growth factor (bFGF) have been shown to affect connective tissue healing in vivo, but their intrinsic role in the healing response has not been established. In the present study, immunohistochemistry with antibodies directed against these growth factors showed that expression of PDGF, TGF-beta 1 and bFGF was increased in and around the wound site in the rabbit medial collateral ligament (MCL) seven days following surgical injury. The strong expression of PDGF correlated with the observed increased cellularity consistent with this growth factor's mitogenic and chemotactic properties. Expression of these growth factors was also increased in wounded rabbit anterior cruciate ligaments (ACL) at seven days following surgical injury, but such expression was limited to the edge of the ACL injury site and was of lesser intensity relative to the MCL. This study suggests that PDGF and TGF-beta 1, and to a lesser extent bFGF, are actively involved during the early stage of MCL healing, but have a more limited presence in the injured rabbit ACL.

Animals↗
PubMed1997

Physical properties of rabbit articular cartilage after transection of the anterior cruciate ligament.

The effect of unilateral transection of the anterior cruciate ligament on the confined compression and swelling properties of the distal femoral articular cartilage of skeletally mature rabbits at 9 weeks after surgery was determined. Gross morphological grading of the transected and contralateral control distal femora stained with India ink confirmed that cartilage degeneration had been induced by ligament transection. Osteochondral cores, 1.8 mm in diameter, were harvested from the medial femoral condyles. The modulus, permeability, and electrokinetic (streaming potential) coefficient of the articular cartilage of the osteochondral cores were assessed by confined compression creep experiments. The properties (mean +/- SD) of control cartilage were: confined compression modulus, 0.75 +/- 0.28 MPa; hydraulic permeability, 0.63 +/- 0.28 x 10(-15) m2/Pa*sec; and electrokinetic coefficient, 0.16 +/- 0.31 x 10(-9) V/Pa. In transected knees, the modulus was reduced by 18% (p = 0.04), while the permeability and electrokinetic coefficient were not detectably altered. The change in modulus was accompanied by a trend (p = 0.07) toward a decrease (-11%) in the glycosaminoglycan density within the tissue, a significant increase (p < 0.001) in the water content of the cartilage after equilibration in 1 x phosphate buffered saline from 70.3 +/- 4.1% in control knees to 75.2 +/- 4.0% in transected knees, and little further swelling after tissue equilibration in hypotonic saline. The compressive modulus of the cartilage from both control and transected knees was positively correlated with the density of tissue glycosaminoglycan. The alterations in the physical properties of the articular cartilage after transection of the anterior cruciate ligament in the rabbit show trends similar to those observed in human and other animal models of osteoarthritis and provide further support for the use of this model in the study of cartilage degeneration.

Animals↗
PubMed1997

Method of histomorphometric assessment of glycosaminoglycans in articular cartilage.

A method of image analysis has been developed for use in the semiquantitative histomorphometric assessment of glycosaminoglycans in articular cartilage stained with safranin O. The reliability of the methodology is reported along with its application to the assessment of articular cartilage in a model of osteoarthritis, i.e., transection of the anterior cruciate ligament in rabbits. With this system, specimens of normal and osteoarthritic articular cartilage were assessed histomorphometrically for the following parameters: total cartilage area, percentage of safranin O stained area, mean gray scale (average stain intensity), and gray scale index (the relative total amount of glycosaminoglycans). Reproducibility was established for 12 specimens of normal cartilage and found to have a SD of less than 8% of the mean for each parameter that was measured. Image analysis of osteoarthritic cartilage revealed each of the parameters, except for average stain intensity, to be significantly lower than that in control cartilage.

Animals↗
PubMed1997

Chondrogenic phenotype of perichondrium-derived chondroprogenitor cells is influenced by transforming growth factor-beta 1.

Our laboratory has developed a method for the repair of osteochondral defects by implanting cultured perichondrial cells attached to a biodegradable polylactic acid scaffold. The success of this approach depends in part on the proliferative characteristics and the phenotype of the implanted cells. Transforming growth factor-beta 1 has been reported to influence these parameters in several mesenchymal-derived tissues in vitro and in vivo. The chondrocytic phenotype is marked by an enhanced expression of the collagen type-II gene. In this study, cultures grown from explants of rabbit rib perichondrium were exposed to exogenously added transforming growth factor-beta 1 at concentrations of 0.1-10 ng/ml of media. Cell proliferation and collagen gene expression were measured. The expression of types I and II collagen genes was analyzed by Northern blot and reverse transcriptase-polymerase chain reaction. The exogenous addition of transforming growth factor-beta 1 at a concentration of 0.1-10 ng/ml resulted in tritiated thymidine uptake by perichondrial cells, with optimum proliferative effects at 0.1 ng/ml. Transforming growth factor-beta 1 added at concentrations of 0.1 and 0.5 ng/ml significantly upregulated the expression of type-II collagen mRNAs. The results suggest that, when the chondrocytic phenotype is defined by markedly enhanced type-II collagen gene expression, the chondrocytic phenotype of explant cultures of perichondrium-derived cells is enhanced by the exogenous addition of transforming growth factor-beta 1.

Animals↗
PubMed1997

The effects of hyaluronan during the development of osteoarthritis.

Ninety-nine mature New Zealand White (NZW) rabbits underwent unilateral anterior cruciate ligament transection (ACLT) and were divided into three groups. The contralateral non-operated knees served as controls. The first group (SA) received intra-articular injections of 0.3 ml hyaluronan (HA: MW; 8 x 10(5)) beginning 4 weeks after ACLT, once a week for 5 weeks. The second group (SV) was injected with vehicle (carrier of HA) in the same fashion as the SA group. The third group (SN) served as a nontreatment group post ACLT. All animals were killed 9 weeks post-surgery and were assessed by gross morphology, histomorphometry and biochemical analysis. Gross morphologic changes on the femoral cartilage in the SA group were less severe than those in the SV and SN groups. Cartilage thickness, cartilage area, and thickness of synovial lining cell layer histomorphometric parameters were measured, showing a positive effect of HA on the preservation of articular cartilage and synovial tissue. Similarly, the cartilage and synovial tissues from knees injected with HA did not demonstrate significant alterations from contralateral controls as measured by biochemical analysis [i.e., water content, pyridinoline concentration, glycosaminoglycan (GAG) content for the cartilage, and DNA concentration for the synovial tissue].

Animals↗
PubMed1997

Analysis of heat shock proteins and cytokines expressed during early stages of osteoarthritis in a mouse model.

OBJECTIVE: Osteoarthritis (OA) is a debilitating disease of the joints. The joints of affected individuals are characterized by a progressive degeneration of articular cartilage leading to inflammation and pain. The expression of heat shock proteins (HSPs) is a ubiquitous self-protective mechanism of all cells under stress, furthermore, the synovium of osteoarthritic individuals contains high levels of cytokines. This study seeks to establish the role of HSPs and cytokines in OA. METHODS: We have investigated the presence of HSPs and cytokines in articular cartilage during early stages of OA in a mouse that is known to develop spontaneous OA lesions (C57 black mouse). The articular cartilage from closely related mice (C57BL/6) was used as control. Messenger RNAs (mRNAs) for HSPs (HSP32, HSP47, HSP60, HSP70, HSP84 and HSP86) and cytokines [interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma)] were detected by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: The mRNA levels of HSP47, HSP70, HSP86, IL-6, and IFN-gamma were up-regulated in the cartilage of C57 black mice, whereas, the level of expression of HSP32, HSP60, HSP84 and IL-1 beta remained unchanged. Furthermore, the expression of IL-1 beta, IL-6, TNF-alpha and IFN-gamma mRNA was associated with expression of HSP60, HSP47, HSP70 and HSP70/HSP86 mRNA, respectively. CONCLUSIONS: The findings in this study suggest that chondrocytes are conditioned under non-physiological stress during early stages of OA, In addition, among HSPs, HSP70 was associated with two different highly expressed cytokines in C57 black mice, indicating the possible role of HSP70 as a characteristic indicator of early stage of OA.

Animals↗
PubMed1997

Quantitation and localization of cartilage degeneration following the induction of osteoarthritis in the rabbit knee.

OBJECTIVE: To develop and apply a new video imaging technique to quantify and localize Indian ink staining of cartilage of the rabbit femorotibial joint after the induction of osteoarthritis by unilateral transection of the anterior cruciate ligament (ACLT). METHODS: Nine weeks after surgery, femora and tibiae from 11 ACLT and contralateral control knees were harvested and positioned to obtain calibrated gray-scale images of the ink-painted articular cartilage surfaces that are opposed with the knee in 90 degrees flexion. Images were processed so that areas of normal cartilage gave a relatively high reflectance score, whereas ink-stained fibrillated cartilage and exposed bone gave low scores. RESULTS: Comparison of the medial and lateral femoral condyles and tibial plateaus (MFC, LFC, MTP, LTP) of control and ACLT knees showed that the area of the MTP not covered by the meniscus had a significantly lower reflectance score (P < 0.001) than other areas. ACLT led to an 11% decrease (P < 0.001) in the overall reflectance score. The reflectance score decreased as a traditional morphological grading of degeneration increased. ACLT-induced degeneration had a predilection for the posteromedial aspects of the joint, and to a lesser extent, the anterolateral aspects. In the tibial plateaus, ACLT caused significant degeneration in the covered, but not the uncovered, areas. Image scores of opposing cartilage surfaces (i.e., MFC vs MTP and LFC vs LTP) were significantly (R = 0.56-0.70, P < 0.001) correlated in ACLT and control knees. DISCUSSION: Identification and characterization of cartilage areas prone to degeneration may be particularly useful for further analysis of biochemical and biomechanical mechanisms in osteoarthritis, as well as the efficacy of therapeutic interventions.

Animals↗
PubMed1997

Osteochondral repair using perichondrial cells. A 1-year study in rabbits.

Articular cartilage repair remains a clinical and scientific challenge with increasing interest focused on the transplantation of chondrogenic cells. This study evaluated the repair response during a 1-year period after implantation of allogenic perichondrium cell polylactic acid composite grafts into 3.7 x 5 mm osteochondral defects drilled into the medial femoral condyles of 82 adult New Zealand White rabbits. The repair tissue was evaluated grossly, histologically, histomorphometrically, biochemically, and biomechanically at 6 weeks, 12 weeks, 6 months, and 1 year after implantation. After gross evaluation, cartilaginous material appeared to fill the defect in 70 experimental knees, for an overall repair frequency of 85%. The histomorphometric results and the histologic appearances were variable. None of the specimens were completely normal at 1 year. Only specimens with subchondral bone reformation displayed a definable cartilage appearing surface with chondrocytes surrounded by dense matrix. Subchondral bone reformation was inconsistent, reaching 50% at 1 year. Biochemically, the repair tissue matured during a 1-year period into a hyaline Type II collagen dominant tissue, whereas glycosaminoglycan content remained low at all time periods. The measured compressive properties of the repair tissue at 1 year were not significantly different from those of the contralateral knee that was not surgically treated. The treatment of osteochondral defects in the rabbit knee with allogenic perichondrium cell polylactic acid composite grafts yielded a high percentage of grossly successful repairs that showed inconsistent subchondral bone reformation. These results suggest that healthy subchondral bone is important to articular cartilage repair. They also highlight that a cartilaginous appearing tissue at gross inspection may not represent structurally normal articular cartilage. Continued multidisciplinary studies on the arthroplastic potential of rib perichondrial cells are needed before human studies, which rarely can extend beyond gross assessment of repair tissue appearance can be undertaken.

Animals↗
PubMed1997

Decrease in fibronectin occurs coincident with the increased expression of its integrin receptor alpha5beta1 in stress-deprived ligaments.

Stress deprivation secondary to immobilization leads to atrophic changes in periarticular soft tissues. The changes in ligaments include a disorganization of collagen and cellular ultrastructure with varied biochemical alterations resulting in a functionally weaker tissue. This study tests the hypothesis that alterations in fibronectin (Fn) and the expression of its integrin receptor alpha5beta1 in ligament fibroblasts accompany the extracellular matrix remodeling which occurs in stress-deprived knee ligaments. The left knees of eighteen New Zealand white rabbits were surgically immobilized in acute flexion. Fibroblasts within three nine week and three twelve week stress-deprived anterior cruciate ligaments (ACLs) and medial collateral ligaments (MCLs) demonstrated markedly increased immunostaining for the beta1 and alpha5 integrin subunits, as compared to fibroblasts in the contralateral unoperated control ligaments. The effects of stress deprivation on the concentration of Fn was measured by competitive ELISA on the remaining twelve rabbits. Decreases in Fn of 54.0 percent and 63.7 percent occurred in the ACL after nine and twelve weeks of stress deprivation when compared to contralateral controls. The MCL had less of a decrease, losing 37.7 percent and 41.7 percent at nine and twelve weeks, respectively. These results suggest an important role for the Fn-specific integrin receptor alpha5beta1 in remodeling stress-deprived periarticular ligamentous tissue, and the importance of maintaining normal stresses on periarticular ligaments to prevent the degradation of extracellular matrix components such as Fn.

Animals↗
PubMed1997

The Marshall R. Urist Young Investigator Award. Autogenous flexor tendon grafts. Biologic mechanisms for incorporation.

To examine the hypothesis that different types of dense regular connective tissue may have different repair mechanisms within the synovial space, intrasynovial and extrasynovial autogenous donor flexor tendon grafts were placed within the synovial sheaths of the medial and lateral forepaw digits of dogs. Histologic, ultrastructural, biochemical, and biomechanical analyses were done between 10 days and 6 weeks after tendon grafting. Intrasynovial tendon grafts remained viable when transferred to the synovial space and appeared to heal through an intrinsic process with preservation of the gliding surface and improved functional characteristics. Extrasynovial tendon grafts functioned as a scaffolding for the early ingrowth of new vessels and cells. Early cellular necrosis consistently was followed by the ingrowth of fibrovascular adhesions from the periphery. The formation of dense peripheral adhesions, obliterating the gliding surface of the tendon, led to diminished tendon excursion and proximal interphalangeal joint rotation.

Animals↗
PubMed1996

Signal pathways and ligament cell adhesiveness.

The influence of signal pathways involved in the adhesion of fibroblasts from the anterior cruciate and medial collateral ligaments to fibronectin was investigated. Specific emphasis was paid to the cyclic adenosine monophosphate and Ca2+/phospholipid pathways to determine the signaling mediated by integrin receptors during cell binding and spreading on a fibronectin-coated glass surface and to compare the roles of these two pathways in integrin-mediated adhesion in fibroblasts from the two ligaments. Individual cell adhesion strengths were determined using a micropipette-micromanipulation system after the cells were treated with signal pathway inhibiting agents. Adhesion in fibroblasts from the medial collateral ligament was significantly reduced by inhibiting agents for Gi protein, protein kinase A, protein kinase C, protein kinase G, phospholipase C, and calmodulin, which suggests a crucial role for cyclic adenosine monophosphate and Ca2+/phospholipid signaling in integrin-mediated adhesion of these fibroblasts. Adhesion in fibroblasts from the anterior cruciate ligament, however, was reduced only by a protein kinase C inhibiting agent and was increased by inhibiting agents for protein kinase A, protein kinase G, and calmodulin, which suggests only a partial role of Ca2+/phospholipid signaling in integrin-mediated adhesion of these fibroblasts. On the basis of additional parallel studies on the role of intracellular calcium in integrin-mediated adhesion, medial collateral ligament and anterior cruciate ligament fibroblast adhesion was calcium dependent throughout the 60 minute time course of adhesion experiments. Fibroblasts from the medial collateral ligament demonstrated a 2.2-fold increase in cytosolic free calcium upon binding to fibronectin, whereas fibroblasts from the anterior cruciate ligament demonstrated no significant increase in calcium. Overall, the study of the intrinsic differences between anterior cruciate ligament and medial collateral ligament fibroblasts in their signal pathways upon binding to fibronectin may reveal information important for further explaining the lack of functional healing response in the anterior cruciate ligament after injury.

Adult↗
PubMed1996

Relationship between joint motion and flexor tendon force in the canine forelimb.

To increase in vivo tendon force and gliding after flexor tendon repair, a variety of modifications to the methods by which protective passive motion is administered have been advocated. To determine the relationship between the prime variables, wrist and digital position, muscle activation, and in vivo tendon force, a clinically relevant canine model was developed. Force was measured in the flexor tendon during several joint manipulation paradigms: single-finger flexion-extension with the wrist flexed (group 1F), single-finger flexion-extension with the wrist extended (group 1E), four-finger flexion-extension with the wrist flexed (group 4F), four-finger flexion-extension with the wrist extended (group 4E), and synergistic wrist and finger motion where wrist extension and finger flexion were performed simultaneously, followed by wrist flexion and finger extension (group SYN). In addition, tendon force was measured during electric stimulation of the proximal flexor muscle mass. Passive tendon force with the wrist extended (groups 1E and 4E) was two to three times greater than that measured with the wrist flexed, independent of the number of digits moved. With the wrist extended, peak tendon force reached 1,997 g +/- 194 g during single-digit manipulation (group 1E), compared to only 853 g +/- 104 g with the wrist flexed during the same maneuver (group 1F). Statistical comparison between means revealed that groups 1E and 4E were significantly different from groups 1F, 4F, and SYN (p < .005). There were no significant differences between groups 1E and 4E or between groups 1F, 4F, and SYN (p > .200). Active muscle force elicited by electrical stimulation and passive force varied dramatically as the wrist was flexed from full extension 3460 g +/- 766 g to full flexion 427 g +/- 239 g (p < .001). Simultaneously, passive tension decreased from 940 g +/- 143 g with wrist extended to 76 g +/- 37 g with the wrist flexed. These data indicate that wrist position has the greatest effect on flexor tendon force during motions that are commonly used to rehabilitate flexor tendon repairs. Thus, if force is to be controlled during passive motion, wrist-joint angle will have the dominant effect, while the number of digits manipulated will have much less of an effect. If the clinical goal is to minimize tendon force, rehabilitation could be carried out with the wrist flexed, whereas if the goal is to increase tendon force, rehabilitation could include exercise programs that use a greater degree of wrist extension.

Animals↗
PubMed1996

Characterization of a model of osteoarthritis in the rabbit knee.

A new computerized method of histomorphometry was used to assess the development of osteoarthritis (OA) in a rabbit model. Three groups of 10 New Zealand White rabbits with closed epiphyses underwent unilateral anterior cruciate ligament transection (ACLT) and contralateral arthrotomy (sham). Groups were killed at 4, 8 and 12 weeks. At the time of death the femoral condyles were assessed grossly following the application of India ink using the following grading scale. Grade 1: intact surface; grade 2: minimal fibrillation; grade 3: overt fibrillation; grade 4: erosion. All histological sections were assessed using a color image analysis system. The mean thickness and area were measured for a defined cartilage region. The root mean square surface roughness (based on deviations from an idealized smooth surface) was calculated to assess the surface profile of the articular cartilage. The results were as follows. After ACLT, no full-thickness ulceration was noted at 4 weeks. Four of the medial femoral condyles at 8 weeks and six at 12 weeks showed full-thickness ulceration of the articular cartilage. The per cent cartilage area and cartilage thickness (ACLT divided by sham) in almost all regions showed decreases with time, indicating progressive erosion. The surface of the ACLT knees was much rougher than that of sham of the knees. These results demonstrate the usefulness of a quantitative methodology using a computerized video analysis system to assess the articular cartilage following ACLT in a rabbit model for the development of OA.

Animals↗
PubMed1995

Articular cartilage repair using allogeneic perichondrocyte-seeded biodegradable porous polylactic acid (PLA): a tissue-engineering study.

Efforts to expand treatment options for articular cartilage repair have increasingly focused on the implantation of cell-polymer constructs. The purpose of this study is to determine the suitability of porous D,D-L,L-polylactic acid as a carrier for delivering repair cells obtained from rib perichondrium into full-thickness articular cartilage defects. In vitro characterization of perichondrocyte-polylactic acid composite grafts was combined with in vivo assessment of the early articular cartilage repair in a clinically relevant model. Using a fluorescent double-stain protocol to visualize live and dead cells in situ, primary cells cultured from perichondrium were found to be capable of attaching to and surviving within a porous D,D-L,L-polylactic acid matrix. These perichondrocyte-polylactic acid composite grafts were then implanted within osteochondral defects drilled into the left medial femoral condyles of 16 adult New Zealand white rabbits. Experimental animals were sacrificed 6 weeks after implantation and the repair tissue was evaluated grossly, histologically, and biochemically. Grossly, 96% (15/16) of the experimental animals demonstrated repairs consisting of a smooth, firm neocartilage which appeared similar in color and texture to the surrounding articular surface. Matrix staining for cartilaginous protein was seen surrounding chondrocyte-like cells in the cartilage regions of the repair. Cellular alignment was found to be related to scaffold architecture. These results suggest that scaffolds composed of porous D,D-L,L-polylactic acid support the growth of cartilaginous repair tissue and are compatible with both in vitro and in vivo survival of chondrogenic cells.

Absorption↗
PubMed1995

Autogenous flexor tendon grafts: fibroblast activity and matrix remodeling in dogs.

To investigate rates of cellular proliferation and matrix turnover in autogenous flexor tendon grafts, hindlimb intrasynovial (flexor digitorum profundus) and extrasynovial (peroneus longus) tendons were placed within the synovial sheaths of the medial and lateral forepaw digits of 18 dogs and treated with controlled early passive motion. After the dogs had been killed, short-term culture and labeling in vitro were utilized to determine rates of DNA, proteoglycan, collagen, and noncollagen protein synthesis. Schiff base covalent collagen crosslink concentrations and total collagen and protein content also were evaluated at intervals through 6 weeks. Tendon grafts of extrasynovial origin showed greater rates of DNA synthesis and significantly elevated levels of proteoglycan, collagen, and noncollagen protein synthesis and Schiff base covalent collagen crosslink concentrations (dihydroxylysinonorleucine) compared with intrasynovial tendon grafts. It was not clear to what extent the increased activity in the extrasynovial graft was due to actual differences between the intrasynovial and extrasynovial tendons or to the responses of the connective tissue surrounding the extrasynovial tendon graft. Since both types of grafts demonstrated similar unaltered levels of collagen and protein content over time, these data suggest greater rates of matrix turnover in tendon grafts of extrasynovial origin than in those of intrasynovial origin. Coupled with previous findings showing increased cellular proliferation in extrasynovial tendon grafts, these data indicate that the process of translation to an intrasynovial environment necessitates a more active process of soft-tissue repair and remodeling when extrasynovial donor tendons are used.

Animals↗