Normal Ligament Tissue Research Articles

Association between magnetic resonance imaging characteristics and pathological findings in entire posterior cruciate ligament with mucoid degeneration.

Magnetic resonance imaging (MRI) findings of a tram-track appearance and celery stalk appearance in mucoid degeneration of the cruciate ligament are valuable; however, their pathological basis is unclear. Because these appearances are generally seen throughout the entire ligament, the association between MRI findings and pathological findings must be verified in specimens of the whole degenerated ligament, including the ligamentous attachments to bone. We herein report two cases of mucoid degeneration of the posterior cruciate ligament with osteoarthritis of the knee requiring total knee arthroplasty. The entire degenerated ligament, including the ligamentous attachments to bone, was removed and pathologically evaluated. On pathological examination, the central portion of the lesion showed typical mucoid degeneration, whereas the marginal and adherent portions showed normal ligament tissue, consistent with a tram-track appearance on T2-weighted MRI. The fibrous normal ligament tissues in the longitudinal direction in regions of mucoid degeneration were consistent with a celery stalk appearance on T2-weighted MRI. No mucoid degeneration was found in the attachment area. The tram-track appearance and celery stalk appearance of mucoid degeneration on MRI can be explained by the pathological findings.

The influence of interleukin-4 on ligament healing

Despite a complex cascade of cellular events to reconstruct the damaged extracellular matrix, ligament healing results in a mechanically inferior scarred ligament. During normal healing, granulation tissue expands into any residual normal ligamentous tissue (creeping substitution), resulting in a larger region of healing, greater mechanical compromise and an inefficient repair process. To control creeping substitution and possibly enhance the repair process, the antiinflammatory cytokine, interleukin-4 (IL-4), was administered to rats before and after rupture of their medial collateral ligaments. In vitro experiments showed a time-dependent effect on fibroblast proliferation after IL-4 treatment. In vivo treatments with IL-4 (100 ng/mL IV) for 5 days resulted in decreased wound size and type III collagen and increased type I procollagen, indicating a more regenerative early healing in response to the IL-4 treatment. However, continued treatment of IL-4 to day 11 antagonized this early benefit and slowed healing. Together, these results suggest that IL-4 not only influences the macrophages and T lymphocytes but also stimulates fibroblasts associated with the proliferative phase of healing in a dose-, cell-, and time-dependent manner. Although treatment significantly influenced healing in the first week after injury, IL-4 alone was unable to maintain this early regenerative response.

The influence of macrophage depletion on ligament healing

Despite a complex cascade of cellular events to reconstruct damaged extracellular matrix (ECM), ligament healing results in a mechanically inferior, scar-like tissue. During normal healing, the number of macrophages significantly increases within the wound site. Then, granulation tissue expands into any residual, normal ligamentous tissue (creeping substitution), resulting in a larger region of healing, greater mechanical compromise, and an inefficient repair process. To study the effects of macrophages on the repair process, bilateral, surgical rupture of their medial collateral ligaments (MCLs) was done on rats. Treatment animals received liposome-encapsulated clodronate, 2 days before rupture to ablate phagocytosing macrophages. Ligaments were then collected at days 5, 11, and 28 for immunohistochemistry (IHC) and/or mechanical testing. Clodronate treatment reduced both the M1 and M2 macrophages at day 5 and altered early healing. However, the macrophages effectively returned to control levels after day 5 and reinitiated a wound-healing response. Our results suggest that an early macrophage response, which is necessary for debridement of damaged tissue in the wound, is also important for cytokine release to mediate normal repair processes. Additionally, nonspecific inhibition of macrophages (without regard to specific macrophage populations) can control excessive granulation tissue formation but is detrimental to early matrix formation and ligament strength.

Histopathological evaluation of the uterosacral ligament: is this a dependable structure for pelvic reconstruction?

To explore, by histological examination, whether the uterosacral ligament complex is an adequate support structure for vaginal vault suspension and other reconstructive procedures of the female pelvis. We dissected 14 fresh hemipelves from seven adult female cadavers. The uterosacral complexes were excised from the pelvic sidewall immediately beneath the uterosacral pedicle. The specimens were stained with connective tissue-specific Movat stain and evaluated microscopically for the presence of collagen and/or elastin. Uterosacral tissue similar to that identified during pelvic reconstructive surgery was obtained in all cases. Six of the women had had a hysterectomy. A ligamentous structure with clearly aligned collagen and interspersed elastin was identified in only three specimens, two from one cadaver of a young woman who had not had a hysterectomy. The other specimens had an attenuated, poorly organized layer of collagen immediately beneath the peritoneum. We could not consistently identify normal ligamentous tissue in the uterosacral complexes. The overwhelming majority of specimens from women who had had a hysterectomy showed disorganized tissue with reduced cellularity. This reinforces doubts about the integrity of these tissues as structural supports in pelvic reconstructive surgery, particularly in elderly women who have had a hysterectomy.

Influence of exogenous growth factors on the synthesis and secretion of collagen types I and III by explants of normal and healing rabbit ligaments.

In this investigation it has been demonstrated that specific growth factors are able to modify collagen secretion in explants from healing rabbit medial collateral ligaments. The addition of 2.5 ng transforming growth factor beta 1 (TGF-beta 1)/mL to 3-week-old scar explants resulted in an increase in the total amount of collagen secreted. Analysis of collagen types I and III individually revealed that the increase mediated by TGF-beta 1 was due primarily to an increase in collagen type I secretion. This led to a ratio of type I:type III that is closer to that found in normal ligament tissue. The addition of 100 ng insulin-like growth factor 2 (IGF-2) to explant cultures of 3-week-old scar tissue also led to an increase in the quantity of collagen secreted, but the increase was in both type I and III collagens. These effects were observed to a lesser degree in 6-week-old scar tissue, and by 12 weeks postinjury, minimal effects of the growth factors on collagen synthesis was detected. Neither growth factor influenced collagen secretion by normal ligament or synovium. In contrast, IGF-1 (100 ng/mL) or basic fibroblast growth factor (bFGF) (10 ng/mL) did not exert a detectable effect on collagen secretion by any of the normal or healing tissues. These results indicate that TGF-beta 1 and IGF-2 can modify the metabolic activity of cells in explants of healing ligaments early after injury and may enhance the repair process leading to improved function.

Quantitative analysis of the fine vascular anatomy of articular ligaments.

An image analysis technique has been developed to quantitatively describe the fine vascular patterns observed in ligament tissue. The longitudinal orientational distribution and total vessel volume of India-ink-perfused blood vessel segments in normal and healing ligaments were determined. The methods involved special vascular preparation of adult rabbit knee medial collateral ligaments (MCL) by India-ink perfusion. Black and white microscope images of ink-perfused tissue sections were subjected to a thresholding procedure to binarize digitized ligament images, which were then skeletonized and analyzed for directional distribution based on the least-squares technique. Analysis of medial collateral ligaments in New Zealand White rabbits using this method has shown that scarred tissue is more vascular and has a more chaotic angular distribution of blood-vessel segments than normal ligament tissue.

Immunoreactive Neuropeptides in Nerves in Ligamentous Tissue

A search for neuropeptide nerves in the healing of the experimentally ruptured medial collateral ligament (MCL) of the rabbit knee used specific antisera to the neuropeptides Substance P, calcitonin gene-related peptide (CGRP), and galanin. Sutured and unsutured MCLs were studied four and 14 weeks postoperatively. Both fluorescent thin nerve strands and small dotlike nerve terminals were regularly seen in the healing zone and in the adjacent normal ligamentous tissue, suggesting innervation of such structures by neuropeptide nerves. All three neuropeptides were more abundant in sutured ligaments than in unsutured ligaments, which may suggest beneficial effects of the apposition of the torn ligament ends on local nerve regeneration. Active involvement of the neural elements in the healing process was also suggested by kinetic studies showing a decrease in Substance P and CGRP staining as well as an increase in galanin staining during the study period. These changes in the periphery parallel the reactive changes earlier described in the dorsal root ganglion and dorsal horn cells occurring after a peripheral nerve injury. This may depend on the antidromic transport to the periphery of neuropeptides synthesized in the central nervous system. This experimental neuroimmunohistochemical mapping study and the known effects of neuropeptides on blood vessels, macrophages, and fibroblasts should stimulate further work on the role of innervation in ligamentous healing.

Healing of the transected anterior cruciate ligament in the rabbit.

Healing of the anterior cruciate ligament was studied in 170 male rabbits. One group included immature animals that had open epiphyses, and a second group consisted of only mature animals. In one knee of each animal, the anterior cruciate ligament was transected either completely or partially, and in the contralateral knee a sham operation was carried out. Mechanical testing and histological studies of the ligaments were done immediately postoperatively and at two weeks, six weeks, three months, and one year. As we expected, there was no regeneration after complete transection of the anterior cruciate ligament, and all of the animals in which this procedure was done had severe osteoarthrosis of the joint at three months. Postoperatively, the partially sectioned ligaments exhibited one-third of the strength of the ligaments on the side on which the sham operation had been done in the immature animals and one-fourth of the strength of the ligaments on the side on which the sham operation had been done in the mature animals. Subsequently, there was secondary complete rupture of 20 per cent of the partially sectioned ligaments. The remaining 80 per cent of the partially sectioned ligaments were clearly weaker two weeks after the operation than immediately postoperatively, but this was also true on the side on which the sham operation had been done. At six weeks, the initial postoperative strength of the partially sectioned ligaments had been regained. At one year, the ligaments of the immature animals were two-thirds as strong as those on the contralateral side, and those of the mature animals were three-fourths as strong as those on the contralateral side. The ligaments were markedly elongated, especially in the mature animals. At three months, stiffness of the ligaments returned to normal. Histologically, the defect was filled with tissue that was still somewhat different from normal ligamentous tissue.

Cruciate ligament replacement using a meniscus. An experimental study.

In 30 rabbits, the medial meniscus was used to replace the anterior or posterior cruciate ligament. The changes that took place were followed in histological sections, obtained both from the area of insertion into bone and from the intra-articular part of the graft. There was a gradual differentiation to chondroid tissue, with subsequent calcific deposition and no appearance of normal ligamentous tissue. The strength of the graft after 52 weeks was only one-quarter of that of the normal ligament. Our results do not justify the use of the meniscus to replace a torn cruciate ligament.