Biomedical subjects

D Amiel

Publications and source records attributed to D Amiel.

At least 91 records · Page 5Linked to original sources

PubMed1992

Genetic expression for type I procollagen in the early stages of flexor tendon healing.

To determine the precise mechanism by which contact tendon healing occurs at the cellular level, the production of pro alpha (I) collagen messenger RNA (mRNA) produced by fibroblasts of healing intrasynovial flexor tendons was determined by an in situ hybridization technique. The repair site and the proximal and distal tendon stumps of repaired tendons treated with early controlled passive mobilization were fixed and buffered in formalin, 3, 7, 10, and 17 days after repair. A complimentary DNA (cDNA) probe corresponding to alpha (I) procollagen mRNA was labeled with [32P]d-CTP. After hybridization, autoradiography, and staining of the sections, the level of procollagen mRNA was assessed by microscopic examination. Rising levels of procollagen mRNA, indicating progressively increasing levels of synthetic collagen activity, were detected in the healing tendons through 10 days. A moderate decrease in procollagen mRNA was seen at 17 days. Genetic expression for procollagen mRNA was localized specifically to the epitenon cells on the tendon surface overlying the repair site and to cells in the gap between the tendon stumps. No detectable expression was noted in endotenon fibroblasts. The finding of high levels of expression for procollagen type I mRNA in the surface layer of healing tendons demonstrates that cells intrinsic to tendon epitenon contribute the greatest quantity of native tendon collagen to the repair site during these important early intervals after tendon suture.

Animals↗

PubMed1992

Magnetic resonance imaging in assessing cartilage changes in experimental osteoarthrosis of the knee.

Cartilage degeneration in osteoarthrosis (OA) of the knee generally is believed to precede osseous abnormalities. Because cartilage abnormalities are not readily detected by routine radiography, we investigated the role of magnetic resonance imaging (MRI) in assessing cartilage damage in a goat model for OA. Four goats had the anterior cruciate ligament of one knee severed surgically to create instability and accelerate OA. Two goats each were killed at 4 and 6 weeks, respectively, after walking on the unstable knees. MRI of the knees was performed with Hybrid fat suppression sequences. The images were correlated with gross anatomic sections and histologic analysis of the knees. On gross examination, the unstable knees showed rapid development of thinning, surface irregularity, and focal defects of the cartilage. These findings correlated well with abnormalities detected on the MRIs. In addition, areas of decreased signal intensity in cartilage correlated with histologic evidence of degenerative changes in the cartilage substance, including fragmentation, fibrillary and eosinophilic changes, and chondrocyte proliferation, indicating attempted cartilage repair. Precise correlation of pathologic and MRI data, however, was lacking, related in part to inability to match perfectly the level and orientation of the gross section with that on the MRI examination.

Animals↗

PubMed1992

Differential metabolic responses of periarticular ligaments and tendon to joint immobilization.

Parameters of collagen metabolic behavior were analyzed in the periarticular connective tissues, i.e., medial collateral ligament (MCL), anterior cruciate ligament (ACL), and patellar tendon (PT), of control and immobilized rabbit knees. Two periods of immobilization were studied: 9 and 12 wk. Collagen turnover and collagen cross-links were quantitatively assessed in the three tissues. The results showed that after 9 wk both synthesis and degradation were significantly increased in the MCL and ACL, whereas the PT showed lesser effects. After 12 wk all three tissues experienced significant losses of collagen mass, which resulted in tissue atrophy. The concentrations of the reducible collagen cross-links dihydroxylysinonorleucine and hydroxylysinonorleucine in the immobilized MCL and ACL were greater than their respective controls, indicating an increase in collagen synthesis, whereas concentrations of the nonreducible cross-link hydroxypyridinoline were observed to be decreased in these tissues. Of the reducible cross-links in the PT, only hydroxylysinonorleucine was found to be increased over control, whereas hydroxypyridinoline was slightly less concentrated. These results taken together have demonstrated that the ligamentous tissues are more susceptible to the effects of stress deprivation secondary to joint immobilization than the PT, and, in particular, the ACL of the three tissues studied appears to be most vulnerable.

Animals↗

PubMed1992

Intercalary flexor tendon grafts. A morphological study of intrasynovial and extrasynovial donor tendons.

Intercalary intrasynovial and extrasynovial flexor tendon graft donors were placed within the synovial sheaths of the medial and lateral forepaw digits of 22 dogs and treated with early controlled passive mobilization. Specimens were studied by light and transmission electron microscopy at 10 and 21 days. Early repair in the extrasynovial tendons occurred by an ingrowth of connective tissue from the digital sheath. Adhesions obliterated the gliding surface and occupied the space between the tendon's gliding surface and surrounding tissues. There was no epitenon response noted in the extrasynovial tendon grafts. While there was considerable new collagen fibril formation within the repair site at the ultrastructural level, there was a lack of longitudinal remodeling. In contrast, the intrasynovial tendon grafts showed early healing, with minimal adhesion formation, by a proliferation and migration of cells from the epitenon. These cells showed greater cellular activity and collagen production at 10 and 21 days compared to cells in extrasynovial tendons at the same intervals. The findings of this study suggest that the use of intrasynovial autogenous tendon graft donors, coupled with early controlled motion, stimulates an intrinsic repair process in both the tendon stump and autogeneous tendon graft. These findings differ significantly from the experimental findings in which extrasynovial, paratenon-covered grafts are used.

Animals↗

PubMed1992

Inhibitors of collagenase in ligaments and tendons of rabbits immobilized for 4 weeks.

Our laboratories have previously measured the capacity for collagenase production by normal and immobilized rabbit periarticular connective tissues (PCT), i.e., anterior cruciate ligaments (ACL), medial collateral ligament (MCL) and patellar tendon (PT). Rabbit limbs were immobilized for 4 weeks and then the tissues were cultured for 4 days. Collagenase and inhibitor (TIMP) were measured in the medium. Collagenase activity was significantly decreased in the medium from all experimental tissues, relative to the levels in contralateral control tissues. On the other hand there was no significant change in inhibitor levels in the three experimental tissues. These results support the idea that collagenase is decreased due to decreased enzyme expression and not to increased inhibitor production.

Animals↗

PubMed1992

Angiogenesis in healing autogenous flexor-tendon grafts.

On the basis of recent evidence that flexor tendon grafts may heal without the ingrowth of vascular adhesions, eighteen autogenous donor tendons of intrasynovial and extrasynovial origin were transferred to the synovial sheaths in the forepaws of nine dogs, and controlled passive mobilization was instituted early in the postoperative period. The angiogenic responses of the tendon grafts were determined with perfusion studies with India ink followed by cleaing of the tissues with the Spalteholz technique at two, four, and six weeks. A consistent pattern of neovascularization was noted in the donor tendons of extrasynovial origin. Vascular adhesions arising from the flexor digitorum superficialis and the tendon sheath enveloped the tendon grafts by two weeks. By six weeks, the vascularity of the tendon grafts of extrasynovial origin appeared completely integrated with that of the surrounding tissues. Examination of cross sections revealed that the segments of tendon had been completely vascularized by obliquely oriented intratendinous vessels. In contrast, the flexor tendon grafts of intrasynovial origin healed without ingrowth of vascular adhesions. Primary intrinsic neovascularization took place from the proximal and, to a lesser extent, distal sites of the sutures. Examination of cross sections revealed vessels extending through the surface layer of the tendon graft, with small vessels penetrating the interior of the tendons at regular intervals.

Animals↗

PubMed1992

Morphologic and biochemical study of sternal cartilage autografts for resurfacing induced osteochondral defects in horses.

Using biodegradable pins, sternal cartilage autografts were fixed into osteochondral defects of the distal radial carpal bone in ten 2 to 3-year-old horses. The defects measured 1 cm2 at the surface and were 4 mm deep. Control osteochondral defects of contralateral carpi were not grafted. After confinement for 7 weeks, horses were walked 1 hour daily on a walker for an additional 9 weeks. Horses were euthanatized at 16 weeks. Half of the repair tissue was processed for histologic and histochemical (H&E and safranin-O fast green) examinations. The other half was used for the following biochemical analyses: type-I and type-II collagen contents, total glycosaminoglycan content, and galactosamine-to-glucosamine ratio. On histologic examination, the repair tissue in the grafted defects consisted of hyaline-like cartilage. Repair tissue in the nongrafted defects consisted of fibrocartilaginous tissue, with fibrous tissue in surface layers. On biochemical analysis, repair tissue of grafted defects was composed predominantly of type-II collagen; repair tissue of non-grafted defects was composed of type-I collagen. Total glycosaminoglycan content of repair tissue of grafted defects was similar to that of normal articular cartilage. Total glycosaminoglycan content of nongrafted defects was 62% of that of normal articular cartilage (P less than 0.05). Repair tissue of all defects was characterized by galactosamine-to-glucosamine ratio significantly (P less than 0.05) higher than that of normal articular cartilage. These results at 16 weeks after grafting indicate that sternal cartilage may potentially constitute a suitable substitute for articular cartilage in large osteochondral defects of horses.

Animals↗

PubMed1992

Rib perichondrial autografts in full-thickness articular cartilage defects in rabbits.

This study investigated the resurfacing of full-thickness articular defects in the adult rabbit medial femoral condyle using a rib perichondrial graft. The graft was secured to a 4-mm-diameter bone core removed from the femoral condyle. Two postoperative treatment protocols were studied: one group had ad libitum cage activity (CAGE; n = 95) and the other group received two weeks of passive motion (PM; n = 73; eight hours per day, five days per week) followed by cage activity. Animals in both groups were killed at six, 12, 26, and 52 weeks. Repair tissue resembling hyaline cartilage formed in a majority of animals at all time periods and in both postoperative treatment groups. The overall success rates in which repair tissue formed were 58% in the CAGE group and 56% in the PM group. However, over time, a maturation of the neocartilage into nearly normal hyaline articular cartilage was noted with the percentage of Type II collagen increasing from 55% at six weeks to 82% at one year. The complex shear modulus of the repair tissue for both groups became similar to normal cartilage with increased healing time. There was no statistical difference in shear moduli between the two treatment modalities. These results show that cartilage repair tissue derived from rib perichondrium could mature into hyaline articular cartilage over time and would not degrade by one year after repair.

Animals↗

PubMed1991

The use of polylactic acid matrix and periosteal grafts for the reconstruction of rabbit knee articular defects.

In order to find a material that would improve cartilage repair, we investigated the use of porous polylactic acid matrix (PLA) with and without periosteal grafts in large articular defects in the medial femoral condyles of 18 New Zealand white rabbit knees. The right knee defect was filled with PLA, the left defect was filled with PLA and a periosteal graft. All animals were killed at 12 weeks. PLA allowed for the de novo growth of neocartilage at the articular surface in all specimens and appeared to serve as a scaffolding for cell migration and matrix formation. Histologically, small amounts of PLA remained under the neocartilage with the majority being replaced by bone. PLA was a suitable carrier for periosteal grafts with a high graft survival rate (89%) and proliferation of a neocartilage which was thicker and more closely resembled articular cartilage than PLA alone knees. Biochemically, there was more type II collagen in the grafted knees (83%) than in the PLA alone knees (65%). Biomechanical tests of the neocartilage included equilibrium displacement, aggregate modulus, and apparent permeability. These tests were not statistically different between PLA alone and grafted knees. Comparison to normal cartilage indicated that the neocartilage was less stiff but had similar permeability. A consistent repair of the articular defects was achieved with and without periosteal grafts resulting in a tissue that closely resembled hyaline articular cartilage.

Animals↗

PubMed1991

Type I procollagen gene expression in normal and early healing of the medial collateral and anterior cruciate ligaments in rabbits: an in situ hybridization study.

The purpose of this study was to compare the levels of procollagen type I messenger RNA (mRNA) in normal and healing medial collateral ligament (MCL) and anterior cruciate ligament (ACL) in a rabbit model. Our method of injury involved a surgical model with identical partial lacerations in the midsubstance of the MCL and ACL. Paraffin sections of normal ligaments, and ligaments 3, 7, 14, and 28 days postlaceration were studied by in situ hybridization to compare and follow the level of type I procollagen mRNA in the two ligaments. A complementary DNA (cDNA) probe corresponding to alpha 1(I) procollagen mRNA was labeled with [32P]d-CTP. After hybridization, autoradiography, and staining of the sections, the level of procollagen mRNA was assessed by microscopic examination. A higher level of procollagen mRNA was consistently detected in normal MCL than in normal ACL, suggesting higher collagen synthetic activity in the MCL. At the injury sites of the MCL and ACL, the levels of type I procollagen mRNA increased at all post-laceration periods, reaching its highest level at 14 days postsurgery. The MCL healing site had a considerably higher level of procollagen mRNA than the ACL healing site (i.e., injury site) at all postoperative intervals. The results demonstrate that procollagen mRNA levels in MCL tissue are higher than those in ACL tissue under normal conditions, as well as in response to injury. The differences in the procollagen mRNA levels of MCL and ACL may reflect the synthesis of collagen in these tissues, and may contribute to the differences in their healing capacities.

Animals↗

PubMed1991

Vascular assessment of the periarticular ligaments of the rabbit knee.

While the rabbit is being extensively utilized in animal models for orthopaedic research, the vascular anatomy of the knee ligaments has not been thoroughly described in this species. This study demonstrates the blood supply to the infrapatellar fat pad, the cruciate ligaments, the medial collateral ligament (MCL), and the menisci, such that the effects of manipulating these tissues may be properly interpreted. Vascular injection with India ink and iodinated i.v. contrast dye was performed in 11 New Zealand white rabbits, and routine histology done on six. The large vessel anatomy is similar to that described for humans and dogs, with a descending geniculate artery, medial and lateral superior and inferior geniculate arteries, a posterior geniculate artery, and a recurrent anterior tibial artery. The microvascular anatomy is also similar in that the infrapatellar fat pad and synovial membrane are highly vascular, the menisci are vascularized from their periphery (being avascular centrally), and the medial collateral ligament is relatively well vascularized. A difference from dogs and humans is present in the anterior cruciate ligament (ACL), which is poorly vascularized, with a single artery on its anterior aspect. High magnification histologic evaluation reveals numerous capillaries in the substance of the MCL, while the ACL is nearly devoid of such vessels. The interspecies variation in vascular anatomy is a variable that must be taken into consideration in any surgical or traumatic animal model investigation of knee pathology.

Animals↗

PubMed1991

Fibroblast chemotaxis after tendon repair.

Healing canine flexor tendons were treated with early controlled passive mobilization. The repair site and proximal and distal tendon stumps were stained for fibronectin and examined by light microscopy at three, seven, eleven, and seventeen days. Fibronectin increased dramatically in the epitenon adjacent to the repair site seven days after repair, a time when epitenon cellular activity was at its peak. By seventeen days, fibronectin staining had decreased substantially, both at the repair site and in the tendon stumps. A delayed increase in fibronectin activity was noted in the endotenon adjacent to the repair site. Fibronectin production appears to be an important component of the early tendon repair process. Fibroblast chemotaxis and adherence to the substratum in the days after injury and repair appears to be related directly to fibronectin secretion. This study is the first to provide documentation of fibronectin localization in a clinically relevant tendon repair model.

Animals↗

PubMed1991

Fibronectin in healing flexor tendons subjected to immobilization or early controlled passive motion.

The medial and lateral forepaw flexor tendons of 20-adult mongrel dogs (n = 40) were transected and repaired with a modified Kessler suture. Post-operatively the dogs were subjected either to immobilization or early controlled passive digital motion. Sacrifices were at 3, 7, 10 and 17 days. The tendons of the contralateral limbs were left intact and used as controls. Urea-heparin-extracted fibronectin was quantitated by competitive ELISA in the tendons and sheaths at the four post-injury/repair time periods. In both groups (controlled passive motion and immobilization), fibronectin concentrations were higher in the injured tissues than in control tissues. However, peak fibronectin concentration (7-days post-injury/repair) was approximately twice as high in the controlled passive motion tissues as in the immobilized tissues. It was concluded, therefore, that, relative to early controlled passive motion, early immobilization depresses the accumulation of tissue fibronectin during the early stages of healing following injury.

Animals↗

PubMed1991

Age-related properties of medial collateral ligament and anterior cruciate ligament: a morphologic and collagen maturation study in the rabbit.

The medial collateral ligament (MCL) and anterior cruciate ligament (ACL) from New Zealand white rabbits ages 2, 12, and 36 mos were resected and utilized for analysis by light microscopy and electron microscopy, as well as for determinations of water content, collagen concentration, collagen crosslink (i.e., reducible, nonreducible) analysis, and collagen synthesis rates in vitro. Both modes of microscopy revealed substantial differences between the various age groups. Water content, as well as collagen concentration, decreased significantly from the 2-mo to the 12- or 36- mo groups. The concentration of the reducible crosslinks, associated with less mature tissue, was significantly greater in the younger tissues relative to the aged tissues. The nonreducible crosslink increased with maturation of the collagen in the 36-mo rabbits. Collagen synthesis rates fell from a highest value in the 2-mo group to the lowest in the 36-mo group.

Aging↗

PubMed1991

Ultrastructural differences between the cells of the medical collateral and the anterior cruciate ligaments.

The anterior cruciate ligament (ACL) does not heal after an interstitial tear, in contrast to the medial collateral ligament (MCL), whose interstitial tears heal readily. The light microscopic and ultrastructural differences between the cells of the two ligaments were studied in rabbit knees to observe the healing characteristics of the two ligaments. A rabbit knee was chosen because the rabbit ACL, like that of humans, does not heal following interstitial injury. The cells populating the MCL have the characteristics of fibroblasts. The cells of the ACL resemble fibrocartilage cells. The phenotypic differences in the cells of the two ligaments may be important determinants of the differences in healing.

Animals↗

PubMed1991

Healing of digital flexor tendons: importance of the interval from injury to repair. A biomechanical, biochemical, and morphological study in dogs.

The effect of an elapsed interval of time between injury and operative repair of the flexor tendons was investigated in a canine model. Transected intrasynovial flexor tendons were repaired either immediately or after a delay of seven or twenty-one days. The biomechanical, biochemical, and morphological characteristics were compared at three and six weeks. The values for angular rotation, linear excursion, ultimate load, and linear slope were determined; concentrations of collagen and reducible collagen cross-links, an index of newly synthesized collagen, were measured; and the ultrastructural morphology of the tendons was examined by high-voltage electron microscopy. For the tendons that were repaired immediately, the values for angular rotation were 9.4 +/- 3.2 and 13.0 +/- 3.7 degrees at three and six weeks; for those that were repaired at seven days, 4.1 +/- 1.3 and 2.5 +/- 1.4 degrees; and for those that were repaired at twenty-one days, 2.7 +/- 0.8 and 4.7 +/- 0.7 degrees. There was a significant effect of the delay until repair on the angular rotation and linear excursion in all three groups (p less than 0.005 for both). Tensile testing of the bone-tendon complex revealed no significant effect of the delay on the values for ultimate load (p greater than 0.05). There were no significant differences in total concentration of collagen at the sites of repair or in the levels of reducible Schiff-base cross-links (indicators of newly synthesized cross-links) in tendons from the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

The early effect of high molecular weight hyaluronan (hyaluronic acid) on anterior cruciate ligament healing: an experimental study in rabbits.

The purpose of this study was to assess, morphologically and biochemically, the effect of hyaluronan (HA) on the early repair process of the anterior cruciate ligament (ACL). Following partial bilateral laceration in the midsubstance of the cruciate ligament, a single dose of HA (MW of 3.6 x 10(6] was injected in one knee and saline in the contralateral knee. Postsurgery, the rabbits were allowed normal (nonimmobilized) cage activity, and were killed after 4 (n = 11) and 12 (n = 10) weeks. The ligaments were evaluated by gross morphology and graded according to the degree of repair. We used grades 1,2, and 3 for uncovered, partially covered, and totally covered lacerations, respectively. Five of the HA-treated ligaments at each time studied were completely covered, compared to 0 at 4 weeks, and 1 at 12 weeks in the saline group. Paired evaluations of the lacerated ACLs showed that the HA-treated ligaments received a healing grade higher than the ligaments exposed to saline in 14 of the 21 animals. In the remaining animals, there was no difference between the sides. The repaired tissue of the ACLs was also examined by light and electron microscopy. When compared qualitatively with saline controls, HA-treated ligaments exhibited a more pronounced repair, with an increased angiogenesis and less inflammatory response. Biochemical analysis demonstrated a mean higher value of type III collagen in the HA-treated injured ACL than in saline-treated injured ACL (13.4 +/- 1.1% and 11.0 +/- 0.8%, respectively). This increased synthesis of type III collagen in the HA-treated injured ACL was statistically higher (p less than 0.05) when compared to the saline-treated injured ACL.

Animals↗

PubMed1990

Acute hemarthrosis: a histological, biochemical, and biomechanical correlation of early effects on the anterior cruciate ligament in a rabbit model.

The early histological, biochemical, and biomechanical characteristics of the anterior cruciate ligament (ACL) were determined in a rabbit model of acute hemarthrosis. The ACLs of 19 rabbits were given seven consecutive daily knee injections of 2 ml of fresh autologous blood, and then compared to contralateral ACLs from control knees injected with 2 ml of lactated Ringer's solution daily for 7 days. The rabbits were then sacrificed. Synovial proliferation with iron deposition within synoviocytes was observed; however, the architecture of the ACL was maintained. Additionally, the total collagen content, collagenase activity, and biomechanical properties of the ACL were unaltered.

Acute Disease↗