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PubMed1996

Characterization of a large chondroitin sulfate proteoglycan present in bovine collateral ligament.

Bovine collateral ligament synthesized a 35S-labeled large proteoglycan species which eluted with a Kav of approximately 0.27 on Sepharose CL-2B and contained only chondroitin sulfate chains with a molecular mass of approximately 32 kDa. Fluorography of the 35S-labeled core proteins derived from the large ligament proteoglycan revealed a broad range of molecular masses above approximately 200 kDa, which was of comparable size to the four major endogenous core protein bands derived from this proteoglycan detected with 5/6/3-B-3, an antibody directed against terminal unsaturated chondroitin-6-sulfate disaccharides. The core proteins derived from the large ligament proteoglycan exhibited immunoreactivity of 12/21/1-C-6, an antibody specific for a peptide epitope common to both the G1 and G2 domains of aggrecan. Four major core protein bands with molecular masses greater than approximately 200 kDa derived from the large ligament proteoglycan, were detected using the antibodies raised against versican from bovine aorta or human fibroblasts. Compared with aggrecan, the 35S-labeled large ligament proteoglycan was distributed over a broader range of buoyant densities in an associative caesium chloride density gradient. This polydispersity may be indicative of differences in the degree of glycosylation as well as heterogeneity in the size of the large ligament proteoglycan core proteins. The 35S-labeled large ligament proteoglycan also demonstrated the ability to form complexes with an aggrecan aggregate preparation, the majority of which could not be dissociated by the presence of HA10-50. These findings indicate that the large chondrotin sulfate proteoglycan synthesized by bovine collateral ligament may be a versican-like proteoglycan which exhibited the potential to form like protein-stabilized complexes.

Aggrecans↗

PubMed1996

The postnatal development of the insertions of the medial collateral ligament in the rat knee.

Bone soft tissue remodelling at the femoral and tibial insertions of the medial collateral ligament (MCL) of the rat knee was monitored at regular intervals from birth to 120 days of age in 40 Sprague Dawley rats. At birth the femoral insertion originated from the perichondrium of the epiphysis. By day 8 the perichondrium within the insertion had turned into fibrocartilage. Secondary ossification of the femoral epiphysis had progressed in the region near to the insertion site by day 15. The epiphyseal cartilage was entirely replaced by bone by day 40 except for the fibrocartilage within the insertion. After that stage, no qualitative change in zonal insertion characteristics was observed, but only increase in size and decrease in cellularity. At birth, the tibial ligament inserted onto the thin cortical bone of the metaphysis via periosteum. At day 8, osteoclasts started to resorb the thin cortical bone at the ligament insertion, thus forming a metaphyseal depression between days 10 and 20. From days 20 to 120, the insertion remained qualitatively unchanged, showing three zones, the ligament, periosteum, and metaphyseal trabecular bone. The deep periosteal layer showed osteoclastic activity in the proximal part and osteoblastic activity in the distal part. The migration-mechanism of the ligament insertion during growth seems to be caused by this growth-related osteoclastic resorption of the proximal metaphyseal bone and by simultaneous osteogenic activity, which successively cements the distal part of the ligament to bone. The persistence of the periosteal layer and the metaphyseal depression for up to 120 days may be regarded as a sign of continuing growth in this animal model. This is the first investigation showing that the formation of the metaphyseal depression is a purely postnatal event, and suggests that this process might be initiated by the change in mode of growth and joint biomechanics after birth, enabling ligament development and migration in a growing and increasingly loaded weight-bearing joint. The mainly resorptive process, which takes place during development of the tibial MCL insertion, may account for the tensile failure of this ligament that commonly occurs at this site during growth. The pronounced morphological differences between the chondral femoral and the periosteal tibial attachment of the adult MCL are apparently caused by the different postnatal development processes at epiphyses and metaphyses.

Animals↗

PubMed1988

Innervation of periodontal ligament and dental pulp in the rat incisor: an immunohistochemical investigation of neurofilament protein and glia-specific S-100 protein.

Nervous elements in the periodontal ligament and dental pulp of rat incisors were investigated by means of immunohistochemistry for neurofilament protein (NFP) and glia-specific S-100 protein. The periodontal ligament in the incisors was densely innervated by NFP-immunoreactive nerve fibers; the distribution of the nerve fibers and their terminations differed markedly from those in molars. NFP-positive, thick nerve bundles entered the lingual periodontal ligament through slits located in the mid-region of the alveolar socket, and immediately formed numerous Ruffini-like corpuscles. In the labial periodontal ligament, all of the NFP-immunoreactive nerve fibers terminated in free endings. The restricted location of the stretch receptor, Ruffini-like corpuscle, in the lingual periodontal ligament appears to be an essential element, because this region is regularly extended during mastication. The nervous elements were restricted to the alveolar half of the periodontal ligament in every region; they avoided the dental half of the periodontal ligament, which presumably moves continuously with the tooth. Pulpal nerve fibers in incisors also showed a characteristic distribution different from those in molars; individual nerve fibers with beaded structures ran in the center of the pulp toward the incisal edge, and did not form the subodontoblastic nerve plexus of Raschkow. Immunostaining for S-100 protein revealed a distribution pattern of nervous elements similar to that for NFP, suggesting that the nerves supplying the periodontal ligament and dental pulp were mostly covered by a Schwann sheath.

Animals↗

PubMed1988

The role of the coracoacromial ligament in the impingement syndrome. A clinical, radiological and histological study.

Seventeen patients with a painful arc syndrome and tenderness over the coracoacromial ligament were selected to demonstrate the changes in the coracoacromial ligament in the impingement syndrome. Plain X-ray examination was normal and a preoperative subacromial bursogram demonstrated impingement in only three out of 17 patients. However, at operation the subacromial space under the coracoacromial ligament, which normally admits the tip of the little finger, appeared unusually tight and barely accessible in 15 out of 17 patients. Histological examination of the biopsied ligament showed degenerative changes but no increase in fibrous tissue. We conclude that in the absence of bony overgrowth the initial change is an increased volume of the soft tissues in the subacromial space. Consequently, the space is compromised by the swelling of its contents, which exert abnormal pressure on the overlying coracoacromial ligament and cause degenerative changes in the ligament. The symptoms of impingement appear because of the unyielding nature of the coracoacromial ligament. Subacromial bursography may not be a reliable test when the coracoacromial ligament is the site of impingement.

Adult↗

PubMed1985

The posterior cruciate ligament and rotatory knee instability. An experimental study.

The importance of the posterior cruciate ligament in relation to valgus-varus and axial rotatory stability in the knee joint was investigated. Mobility patterns were drawn from 20 osteoligamentous preparations after successive transection of the posterior cruciate ligament (PCL), the medial and lateral collateral ligaments, and the posterior joint capsule. The knee joint remained grossly stable after isolated transection of the PCL, and further cutting of either one of the collateral ligaments or of the posterior capsule yielded no greater instability than one should expect from isolated cutting of each of these structures. The posterior cruciate ligament was the stabilizing factor in flexion and external rotation after injury to the lateral collateral ligament and the posterolateral capsule, and it restricted internal rotation after cutting of the medial cruciate ligament and the posteromedial capsule. Valgus instability was markedly increased during the whole range of movement when PCL was included in injury to the medial compartment ligaments, and when included in a lateral compartment injury a further varus instability was found, though only in the flexed or semiflexed knee. No hyperextension could be demonstrated after these injuries.

Biomechanical Phenomena↗

PubMed1980

Biomechanic studies reinserting the medial collateral ligament to correct a chronic anteromedial instability of the knee joint.

One possibility to correct a chronic anteromedial instability of the knee joint is the osseous reinsertion and tightening of the medial collateral ligament. In experiments with a string model and strain gauges attached to the ligaments we investigated the advantages and/or disadvantages of the femoral and tibial reinsertion. Regarding the tension mechanism the medial collateral ligament reacts considerably more sensitivity to the femoral reinsection in proximal-dorsal direction than to the tibial-reinsertion in distal-ventral direction. An accurate knee flexion between 40 and 60 degrees has to be provided reinserting the ligament in proximal-dorsal direction to avoid excessive tension and resulting destruction of the ligament. However the reinsertion of the ligament in distal-ventral direction, independently from the flexion of the knee, always approximates the natural tension of the anterior and posterior margin of the untreated ligament. Biomechanically the reinsertion in distal-ventral direction to tighten the loose ligament seems to be preferable to the reinsertion in proximal-dorsal direction.

Biomechanical Phenomena↗

PubMed1997

Anatomic and MRI study of the subtalar ligamentous support.

The diagnosis of subtalar instability remains difficult both clinically and radiographically. The authors present an anatomic and MRI study of the subtalar ligamentous support. The anatomic study has consisted in dissections and sections of cryoconserved hindfeet (15 cases) which precises the organisation of ligamentous bundles in the lateral (sinus tarsi) and central (canalis tarsi) subtalar compartments, mainly represented by the trilayered inferior extensor retinaculum, the cervical talo-calcaneal ligament and the interosseous talo-calcaneal ligament. MRI study (1.5 tesla) of anatomic specimens was performed according to defined types of sections: sagittal, coronal, coronal oblique, axial transverse. The correlations of anatomic and MRI sections allowed a precise interpretation of the subtalar ligamentous support as anatomically described. A complementary clinical MRI study was performed which allowed the validation of "the inversion test": this test optimizes the visualization of the different ligamentous structures. Relative to the difficulties of conventional imaging procedures, MRI appears of clinical relevance in the diagnosis of subtalar instabilities. This technique allows direct visualization of ligaments (or their rupture) and therefore a better evaluation of subtalar involvement in ankle sprain. This paper present a functional concept in MRI articular ligamentous restraints concern.

Humans↗

PubMed2000

Effects of rectal mobilization and lateral ligaments division on colonic and anorectal function.

PURPOSE: Colonic and anorectal function are altered after posterior rectopexy. The aim of this randomized, prospective study was to evaluate the effects of rectal mobilization and division of the lateral ligaments on colonic and anorectal function. METHODS: Posterior rectopexy was performed in 18 patients with complete rectal prolapse. Anal manometry and measurement of rectal compliance, total and segmental colonic transit time, constipation score, and defecation frequency were performed preoperatively and three months postoperatively. Ligaments were divided in ten patients. RESULTS: Mean preoperative total transit time was similar between the two patient groups and doubled postoperatively (P = 0.03). Mean postoperative segmental transit time increased by a factor of 1.7 in segments I (ascending colon) and II (descending colon) and by a factor of 2.3 in segment III (rectosigmoid). The same pattern was found in both groups. Mean resting pressure decreased after division of the lateral ligaments and increased after preservation. Mean rectal compliance decreased after division of the ligaments and increased when they were preserved. Mean postoperative constipation score differed little from the preoperative score. Mean defecation frequency was decreased in the group with the ligaments preserved and increased in the group with the ligaments divided. None of the effects of rectal mobilization or division of the lateral ligaments on anorectal function reached statistical significance. CONCLUSION: Rectal mobilization had a statistically significant effect on colonic function. Total and segmental colonic transit times doubled. The effects on anorectal function were not significant. Division of the lateral ligaments did not significantly influence postoperative functional outcome.

Adult↗

PubMed1985

[Alloplastic reconstruction of the ligament of the knee in chronic rotation instabilities--technics and results].

During the years from 1980 through 1985, 23 patients with chronic rotation instabilities of the knee joint underwent alloplastic reconstruction of the knee ligament system at the Berufsgenossenschaftliche Unfallklinik Frankfurt am Main. Twenty out of these patients could be checked up after an observation period of more than four years. The examinations showed that in 90% of the patients an essentially improved ligament stability was achieved by the surgical intervention. The use of a textile strip made of polyethyleneterephtalate (Trevira hochfest type 730) affords a significantly better ligament stability than the application of autologous pedicle and free tissue grafts. This is especially true with respect to the alloplastic substitution of cruciate ligaments. Nevertheless the indication for alloplastic ligament prosthesis should still be subject to severe precautions. Actually we consider this method as indicated in patients having undergone repeated unsuccessful operations of the knee ligament in whom there is not - or no longer - enough autogenous tissue of sufficient quality. A precise implantation at the designated site as well as a stable fixation are necessary for the durable stability of the alloplastic ligament prosthesis. It is very important to observe the technique especially developed for this purpose, but the maintenance of function and stability is the decisive point. After having used textile synthetic ligaments (Trevira hochfest type 730) for about five years, our examination results suggest that the known problems of chronic rotation instability can be considerably reduced by applying this technique.

Adolescent↗

PubMed1985

[Alloplastic replacement in chronic isolated rupture of the cruciate ligament--technic and results].

A report is given on 48 inveterate isolated cruciate ligament ruptures of the knee joint which were treated by corrective reconstruction surgery with an alloplastic material made of polyethyleneterephtalate. 36 patients could be checked up almost five years after the implantation. It is of great importance that the described implantation technique is strictly observed. The therapy results obtained by alloplastic substitution of the cruciate ligament show that a considerably better stability of the ligament is achieved by this method than by the use of autologous pedicle or free tissue grafts (J. Mockwitz, H. Contzen). The alloplastic substitution of the isolated cruciate ligament rupture by means of a polyethyleneterephtalate ligament seems to be an "ideal" indication. Up to now, however, we have never made the decision to perform a primary alloplastic substitution in case of a recent rupture, e.g. of the anterior cruciate ligament, or to apply the textile ligament material in order to fix or to strengthen the sutured or reinserted ligament structures.

Adolescent↗

PubMed1992

[Damage to the knee ligament as a concomitant injury in femoral shaft fractures].

Knee ligament injuries associated with femoral shaft fractures can severely influence the functional results of treatment. In a follow-up of 59 operatively treated femoral shaft fractures 18.6% of the patients revealed ligamentous damages. In all cases one or both of the cruciate ligaments were injured. Especially polytraumatized car front-seat passengers are at higher risk with 30.8% ligament ruptures. While only 61.6% of the ligament injuries were primarily diagnosed, the testing of knee joint stability after osteosynthesis of a femoral fracture is essential. Furthermore arthroscopy should be performed if there is any hint of ligamentous damage. The ruptures of the anterior cruciate ligament and the ligamentous avulsion fractures can be successfully treated on by operative means.

Adolescent↗

PubMed2003

[The role of the tibiofibular syndesmotic and the deltoid ligaments in stabilizing Weber B type ankle joint fractures--an experimental investigation].

The purpose of the present biomechanical investigation was to check the functional importance of the syndesmosis ligaments and of the deltoid ligament for ankle fracture type B according to the AO-Weber classification. We constructed a special fixation clamp, with 12 fresh and unembalmed lower legs being tested for lateral shift (mm) and ten for tibiotalar rotation. All specimens were exposed in the same neutral position. Transverse loads (F(y)) varied between 0 and 150 N, axial loads (F(z)) between 0, 300, 600 and 1,000 N and rotational loads (F(r)) between 2.4 and 4.9 Nm. All series were repeated according to supination-eversion (SE) injury patterns of the Lauge-Hansen classification. Syndesmotic ligaments and the fibula were incrementally sectioned from anterior to posterior. Type SE I consisted of an isolated incision of the anterior syndesmosis ligament. Type SE II had an additional oblique fracture of the fibula at the height of the tibiofibular syndesmosis. In type SE III injuries, in addition to the fibular fracture, a complete rupture of the syndesmosis ligaments was present, and for type SE IV lesions the deltoid ligaments were incised. The transverse load-displacement curve was s-shaped in all uninjured joints,with the highest gradient between 10 and 20 N with no axial compression. Without axial compression in cases of F(y)=25 N transverse loads, the mean talus translation was 0.51 mm. Following type II injuries, the average talus translation was 0.68 mm (not significant) and rose to an average of 0.95 mm ( P <0.01) in type III injuries. After additional incision of the deltoid ligaments, the ankle joint subluxed permanently when more than 5-10 N transverse loads were applied. Axial loads of 300 N or more resulted in a considerable reduction in talus translations, indicating increased stability and congruency within the joint complex. In this way, the vertical loading of the ankle joints always contributed to joint stability. The average internal tibiotalar rotation reached with a torque of 2.4 Nm was 3.52 degrees and with 4.9 Nm 5.15 degrees when no axial compression was applied. External rotation measured -6.36 degrees and -8.62 degrees, respectively. Following the experimental protocol, significant increases were noted for external rotation at SE II degrees injuries ( P =0.003) and for internal rotation at SE III degrees ( P =0.03) injuries. Our data support the proposition that the deltoid ligaments and the posterior syndesmosis play a key role in the stability of ankle fractures for supination-eversion injuries. If these structures remain intact, conservative and early functional treatment are recommended in patients with minimal (<2 mm) or no fracture displacement. This concept is confirmed by the literature dealing with clinical mid- and long-term follow-up studies.

Ankle Injuries↗

PubMed2002

The anterior inferior tibiofibular ligament and talar impingement: a cadaveric study.

Impingement by the distal fascicle of the anterior inferior tibiofibular ligament (AITFL) is a relatively new entity among the known causes of anterolateral impingement syndromes of the ankle. This study investigated the anatomy of the anterior inferior tibiofibular ligament and its possible role in talar impingement in 47 ankles of 27 cadavers. The length, width, insertion point to the fibula and the interactions with talus were noted, as was the relationship of the fascicle and talus during different ankle movements before and after incision of the lateral ligaments. A distal fascicle of the AITFL was found in 39 of the 47 ankles (83%) and appeared as a single-complete ligament in the remaining 8 ankles (17%). The fascicle averaged 16.1+/-2.94 mm in length (range 10-21) and 4.2+/-1.00 mm in width (range, 3-7). The insertion point of the fascicle on the fibula averaged 10.3+/-2.27 mm (5-13) distal to the joint level. Contact between the ligament and the lateral dome of the talus was observed in 42 specimens (89.3%). Bending of the fascicle was observed in 8 of these 42 ankles with forced dorsiflexion. These 8 specimens were significantly wider and longer than the specimens without bending of the fascicle. Incision of the anterior talofibular ligament led to bending in dorsiflexion in additional 11 ankles. The total 19 fascicles with bending after incision of the anterior talofibular ligament were significantly longer and inserted more distally than the remaining 20 fascisles without bending. Manual traction simulating distraction during arthroscopic procedures relieved the contact. These findings show that the presence of the distal fascicle of the AITFL and its contact with the talus is a normal finding. However, it may become pathological due to anatomical variations and/or instability of the ankle resulting from torn lateral ligaments. When observed during an ankle arthroscopy, the surgeon should look for the criteria described in the present study to decide whether it is pathological and needs to be resected.

Biomechanical Phenomena↗

PubMed2001

Calcification of the alar ligament of the cervical spine: imaging findings and clinical course.

Ligamentous calcification of the cervical spine has been reported in the yellow ligament, anterior and posterior longitudinal ligaments and interspinous ligament. Calcification in the upper cervical spine is rare, although some cases with calcification of the transverse ligament of the atlas have been reported. Two patients with calcification of the alar ligament with an unusual clinical presentation and course are described. Examination by tomography and computed tomography (CT) showed calcification of the alar ligament and the transverse ligament of the atlas. CT documented decreased calcification as symptoms resolved. There may be a role for CT in the search for calcifications in the upper cervical spine in patients presenting with neck pain and pharyngodynia if radiographs are normal.

Adult↗

PubMed2006

Anatomical evaluation and clinical importance of the tibiofibular syndesmosis ligaments.

The aim of this study was to describe the detailed anatomical arrangement of ligaments of the tibiofibular syndesmosis and to highlight the clinical aspects of fracture dislocations. This study was performed on 42 legs of adult human embalmed cadavers. Tibiofibular syndesmosis ligaments attachments and their mutual relationships were described and their dimensions were measured. The anterior tibiofibular ligament is usually composed of three parts. This ligament runs obliquely at laterodistaly direction making 35 degrees angle with horizontal plane and posteriorly 65 degrees angle with sagittal plane. The posterior tibiofibular ligament runs almost horizontally 20 degrees angle with horizontal plane. The mean thicknesses of tibial and fibular attachments are 6.38+/-1.91 mm and 9.67+/-1.74 mm, respectively. The inferior transverse ligament originates from just below the posterior tibiofibular ligament, which has variations on the shape and dimensions due to its attachment points. The average length is 36.60+/-9.51 mm. The network between the fibular notch and the distal fibula has been filled with the interosseous tibiofibular ligament whose fibers follow the laterodistal and anterior direction from the tibia to the fibula. It lies proximally 30-40 mm from the mortise. At the inferior view of the tibiofibular syndesmosis a pyramidal shaped cartilaginous facet was observed which was attached to the fibula. The length of this cartilage was variable. Some of synovial plicas from the ankle joints synovial membrane were observed at this view. We conclude that the results of this study may be useful to both orthopedic surgeons and radiologists for anatomic evaluation of the tibiofibular syndesmosis area.

Aged↗

PubMed2000

Activation of nuclear factor kappaB at the onset of ossification of the spinal ligaments.

We examined the correlation between the activation of nuclear factor kappaB (NFkappaB), stimulated by environmental factors involving cytokines and growth factors in ligament cells, and the onset of ossification of the spinal ligaments (OSL) or diffuse idiopathic skeletal hyperostosis (DISH). Aseptic samples were taken carefully from non-ossified sites during surgery (75 patients). We carried out preliminary hematoxylin and eosin and toluidine blue staining, using five portions of each specimen, and excluded samples containing chondrocytic, osteoblastic, or inflammatory cells (n = 25). We used specimens from the remaining 50 patients (35 men and 15 women, ranging in age from 45-81 years); average age, 59.5 years (18 nuchal ligament specimens, and 32 yellow ligament specimens). OSL or DISH had occurred in 25 patients, 20 patients were in the non-OSL group (8 with cervical spondylotic myelopathy, and 12 with lumbar canal stenosis), and the remaining 5 samples were collected from patients with injury. For culture study, we used portions of the 14 largest samples from the above 50 patients. We extracted nuclear proteins and cytoplasmic proteins from non-ossified spinal ligaments in 50 patients and detected p65RelA/NFkappaB by Western blotting. Tumor necrosis factor-alpha (TNF alpha), interleukin 1beta (IL-1beta), platelet-derived growth factor BB (PDGF-BB) and transforming growth factor-beta1 (TGF-beta1) in cytoplasm were quantified by enzyme-linked immunosorbent assays (ELISA). Cultured cells from the 14 samples were then stimulated with 10, 100, 250, or 500 ng/ml of recombinant human (rh)PDGF-B or TGFbeta1. A control experiment was performed without rhPDGF-BB or TGFbeta1 stimulation. Alkaline phosphatase (ALP) activity was standardized by the DNA content of the cells. The number of NFkappaB-positive samples was significantly higher in patients with OSL or DISH than in non-OSL patients. This tendency was obvious in the case of OSL or DISH with non-insulin-dependent diabetes mellitus (NIDDM). In OSL and in DISH patients, significantly greater amounts of PDGF-BB and TGFbeta1 were seen in ligament cells than in non-OSL patients (P < 0.05). There was a positive correlation between the detection of p65RelA/NFkappaB band and the content of PDGF-BB and TGFbeta1 in ligament cells (P < 0.05). ALP activity tended to be higher in cells in the OSL group not receiving any other treatment. Our results indicate the possibility that NFkappaB, stimulated by environmental factors involving PDGF-BB and TGFbeta1 in ligament cells, influences the osteoblastic differentiation of undifferentiated mesenchymal cells.

Actins↗

PubMed1982

A stereologic analysis of collagen phagocytosis by periodontal ligament fibroblasts during occlusal hypofunction in the rat.

Maxillary molars were extracted unilaterally from 4 young male rats so as to leave the agonist mandibular molars in hypofunction. The mandibular molars on the opposite side of the mouth acted as controls. Three days later, the animals were killed by perfusion and all mandibular molars removed en bloc. After demineralization, each block was trimmed, prepared for electron microscopy and embedded in Epon. The Epon blocks were trimmed so as to comprise the middle-third of the buccal periodontal ligament of the mesio-buccal root of the first molar together with some cementum and alveolar bone as landmarks. Two light-gold sections were cut from each trimmed block and systematically photographed in the electron microscope. The photographs were analysed stereologically so as to quantitate phagocytosed collagen (ICC), cytoplasm (CC) and extracellular fibrillar collagen (ECC). The results for the hypofunctional and contralateral control ligaments were compared with each other and with earlier results from similar but untreated (baseline) animals. The results were expressed as mean values for ICC, CC and ECC, and as the ratios ICC/ECC (the fraction of extracellular collagen phagocytosed), ICC/CC (collagen phagocytic activity per unit cytoplasm) and CC/ECC (cell density per unit extracellular collagen fibril). Significant differences were found for all measurements except ICC/ECC which remained the same in the three states of the ligament. The hypofunctional ligaments had the lowest collagen phagocytic activity and the highest cell density, whereas the ligaments from the untreated animals had the highest collagen phagocytic activity and the lowest cell density. The values for the contralateral control ligaments were intermediate between those for the other two states of the ligament. There was also a significant loss of recognizable, extracellular fibrillar collagen in the hypofunctional ligament. It is suggested that this loss of ECC and its replacement by less organized, pre-fibrillar forms of collagen may be an important mechanism in tooth eruption.

Animals↗

PubMed1988

Terminal differentiation of nuchal ligament fibroblasts: characterization of synthetic properties and responsiveness to external stimuli.

The temporal expression of elastogenesis is unique among connective tissues in that elastin production occurs primarily during late fetal and early neonatal periods and is essentially fully repressed once fiber assembly is completed. To test whether elastin synthesis in adult nuchal ligament fibroblasts is permanently repressed or whether the cells retain the ability to reinitiate production upon proper stimulation, we examined in adult ligament cells various parameters known to be involved in the regulation of elastin production. Elastin synthetic capacity, as determined by the levels of steady-state tropoelastin mRNA, of adult tissue was significantly decreased relative to fetal tissue. Likewise, fibroblasts grown from explants of adult ligament had about a fourfold decrease in elastin production and elastin-specific mRNA levels. On the other hand, adult cells were similar to fetal ligament cells in that they were sensitive to glucocorticoid stimulation and demonstrated chemotactic responsiveness to elastin peptides. Since our previous studies have shown that the extracellular matrix (ECM) plays an important role in influencing elastin phenotypic expression, fetal and adult fibroblasts were grown on slices of nonviable adult ligament to test if repression of elastin production was directed by factors in ECM of adult tissues. No change in elastin synthesis was detected with either cell type grown on adult ligament, whereas both fetal and adult cells demonstrated increased elastin production in response to contact with fetal ligament. These results suggest that adult ligament ECM does not provide a metabolic signal to shut off the elastin gene and that adult cells remain responsive to external stimuli that may reinitiate high levels of elastin synthesis.

Animals↗