| Backzround and Objective: Apoptosis occurs within human intervertebraldiscs, but little is known about the pathologic significance of thisprocess. On the other hand, the cartilaginous endplate is known todecrease in thickness and to disappear with aging and degeneration. Thecause of this age-related change remains unclear. To study therelationship between apoptosisi of endplate chondrocytes anddegeneration of the intervertebral disc by seting up disc spondylosisanimal model, determing the effective of apoptosis in disc degeneration,to provide the new idea for preventing and curing cervical spondylosis.Methods: 24 mice were divided into experimental group and control grouprandomly. The experimental group model was established by resection allsupraspinous and interspinous ligaments, excision of parts ofzygapophysial joints, the posterior paravertebral muscles were alsodetached from posterior elements of the spine, accelerating discdegeneration. The control group was incised only the skin. At each timeperiod of 9 weeks, 18 weeks and 36 weeks after surgery, mice were killedby over anesthesia, to get all the vertebra completely, the sample werecut in midsagittal direction. To separating the disc and endplatechondrocytes. Cervical discs were evaluation according to Thompsoncriterion. Endplate sections were stained with Tunel procedure. Thenumber of apoptotic cells and vital cells were counted, the degree ofdegeneration were evaluated.Rusults:1. Histologic evaluation of cervical discThe degree of disc degeneration was evaluated by use of the hematoxylin and eosin stained sections. The mice discs of 9 weeks controlgroup are normal mainly. The mice discs of 9 weeks experimental groupare little degenerated. Cartilaginous tissue of anterior part of annularfibrosus hyperplasied. The sequence is not normal, nucleus pulposusdeviated to posterior. The edge of vertebral is smooth. The mice discsof 18 weeks control group are similar to the discs of 9 weeks. Nucleuspulposus shrinked. We can see anulus fibrosus gaps in anulus fibrosus.The mice discs of 18 weeks experimental group had degenerated obviously.The parts of anulus fibrosus are fibrotic. The boundary between anulusfibrosus and nucleus pulposus is too blurred. In Posterior of vertebrate,we can see the osteophyma. The mice discs of 9 weeks experimental groupdegenerated seriously, anulus fibrosus fibrous degenerated totally.nucleus pulposus disappeared.2. To observe apoptosis of discs by HE stained.While the mice become older and older, the degeneration processaccelerated. The texture of endplate have changed too much gradually.In earlier period, the change is not obvious, the endplate of controlgroup is thick, we can see some cartilage lacuna. 9 weeks after surgery,the endplate construction of two groups all disappeared partly. Celldensity degraded, there have some apoptotic body. 18 weeks after surgerydegenerated obviously. 36 weeks after surgery, endplate disapperednearly.3. To compare apoptosis rate between two groups by TUNEL stained.Although few apoptotic events occurred in earlier period, apoptosismainly occurred after 18 weeks. We can observed by photos, there havea little apoptosis cells in two groups of 9 weeks. In 18 weeks, there have a large different between two groups. Experimental group has moreapoptosis cells than control groups. But in 36 weeks, apoptosis cellshave no obvious different between two groups.Conclusion:1. Disc spondylosis animal model accelerated degeneration, quantity ofapoptosis cells increasd.2. Apoptosis cells of endplate chondrocytes gradually increased, more andmore endplate had destroyed, the degenerated progress also accelerated.So we considered that aged is the important factor for intervertebraldiscs degeneration.3. Apoptosis of endplate chondrocytes is the important reason forintervertebral discs degeneration.
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