| Cervical spondylosis refers to cervical disc degeneration and its secondary pathological changes that may produce problems related to pressure on cervical spinal cord and nerve roots and blood vessels. This pressure can cause weakness and numbness and pain in various areas of the body. Now it has been widely accepted that cervical spondylosis and all its manifestations are a product of cervical disc degeneration. So far, most of the efforts to treat cervical spondylosis have mainly focused on decompression of cervical spinal cord and never roots, with little attention to disc degeneration itself. Moreover, anterior cervical discoidectomy and fusion is usually followed by postoperative degenerative changes at adjacent discs. So, it is necessary to find out some measures to slow down disc degeneration. However, the exact mechanism of cervical disc degeneration has still not been well understood.Degeneration is a process by which tissue deteriorates, loses functional activity and may become converted into or replaced by other kinds of tissue. It has been suggested that the imbalance between apoptosis and proliferation plays an important role in the development of some degenerative diseases such as osteoarthritis. Though the relationship between disc degeneration and apoptosis has received some attention in recent years, the signal transduction pathway of disc cells' apoptosis is still unclear. And furthermore, little attention has been paid to the relationship between disc degeneration and proliferation.Bax, as an apoptosis-related protein, can bind with the permeability transition channel of mitochondrion and induce the release of cytochrome C. As a result, the cycteinyl asparate-specific proteases will be activated. Activated Caspase-3 caninactivate apoptotic inhibitors, activate the regulating proteins which improve apoptosis, and hydrolyze cytoskeletal proteins and nucleoproteins, and finally lead to apoptosis. Some studies have reported the up-regulations of the expressions of Bax and Caspase-3 and the increasing activity of Caspsase-3 in some degenerative diseases such as osteoarthritis.PCNA is a useful marker for detecting proliferating cells. It has been reported that the proliferating activity is higher in degenerative tissues than in normally mature tissues, indicating that the increase of proliferating activity in degenerative tissues may be a repairing response to the internal or external injuries.Objective:To detect the cell density, apoptotic incidence and the expressions of PCNA, Bax and Caspase-3 in human cervical discs, and analyze their relationships to study the roles that apoptosis and proliferation play in the development of human cervical disc degeneration and the signal transduction pathway of disc cells' apoptosis. Thus the present study may help to furthermore understand the mechanism of human cervical disc degeneration and provide new idea for biologic treatment of it in future.Materials and methods:Thirty-three herniated human cervical discs were surgically collected from twenty-seven patients undergoing anterior cervical discoidectomy and fusion. All the cases were affirmed by MRI and they hadn't experienced discography, collagenolysis of nucleus pulposus and percutaneous laser disc decompression. The control group consisted of twenty-two human cervical discs harvested from six young men without spine-related condition immediately after their death. Apoptotic disc cells were detected by TUNEL and histomorphology, and immunohistochemical staining with S-P method was performed to exam the expressions of PCNA, Bax and Caspase-3 in all specimens. All the data were analyzed with SPSS10.0 statistical software. P<0.05 was considered the level of significance.Results:1. Cell densities in two groups: In control group, the cell density of cartilageend-plate, nucleus pulposus and the average cell density were 25.41 + 1.89/HP, 8.96±1.14/HP and 12.58 + 1.25 /HP, respectively. In patient group, the three corresponding numbers were 17.27 ± 1.82/HP, 6.30 ±1.54 /HP and 8.81 + 1.35/HP, respectively. The cell densities were higher in control group than in patient group(P<0.01).2. TUNEL positive incidences in two groups and the correlations between TUNEL positive incidences and cell densities: In control group, the TUNEL positive incidence of cartilage end-plate, nucleus pulposus and the average TUNEL positive incidence were 6.86%+1.42%, 7.02% ±1.26% and 6.93% ±1.09%, respectively. In patient group, the three corresponding numbers were 13.04%± 1.75%, 11.73%+1.36 %and 12.29+1.19%, respectively. The TUNEL positive incidences were higher in patient group than in control group(P<0.01). When analyzed the fifty-five specimens together, TUNEL positive incidences showed significant inverse correlations with their respectively corresponding cell densities(P<0.01).3. The expressions of PCNA in two groups and the correlations between PCNA positive incidences and cell densities: The PCNA positive incidences of cartilage end-plate were 6.47% ±1.31% in control group and 5.75% ±1.46% in patient group, respectively(P>0.05). The PCNA positive incidence of nucleus pulposus in control group was 4.55% ±1.54%, it was lower than that in patient group, which accounted for 8.38% ± 1.98%(P< 0.01). The average PCNA positive incidence in control group was 5.36%+1.10%, it was also lower than that in patient group, which accounted for 7.20%±1.23%(P<0.01). Only the PCNA positive incidence of nucleus pulposus and the average PCNA positive incidence in patient group showed significant positive correlations with their respectively corresponding cell densities(P<0.01).4. The expressions of Bax in two groups and the correlation between Bax positive incidence and TUNEL positive incidence: The Bax positive incidence of nucleus pulposus was 10.94% ± 1.72% in control group, it was lower than that in patientgroup, which accounted for 19.32%±1.95% (P<0.01). There were no Bax positive cells in the cartilage end-plate of all specimens. When analyzed the fifty-five specimens together, the Bax positive incidence of nucleus pulposus showed significant positive correlation with the TUNEL positive incidence of nucleus pulposus(P<0.01).5. The expressions of Caspase-3 in two groups and the correlation between Caspase-3 positive incidence and TUNEL positive incidence: The Caspase-3 positive incidence of nucleus pulposus was 8.92% ±1.48% in control group, it was lower than that in patient group, which accounted for 15.05% ±1.74% (P< 0.01). There were no Caspase-3 positive cells in the cartilage end-plate of all specimens. When analyzed the fifty-five specimens together, the Caspase-3 positive incidence of nucleus pulposus showed significant positive correlation with the TUNEL positive incidence of nucleus pulposus(P<0.01).Conclusions:1. The decrease of cell density is involved in the development of human cervical disc degeneration.2. The imbalance between apoptosis and proliferation could contribute to the decrease of cell density in human cervical disc.3. Bax and Caspase-3 might play a role in disc cells' apoptosis in nucleus pulposus of human cervical disc, indicating that these two genes may be the potential target genes to slow down human cervical disc degeneration by inhibiting disc cells'apoptosis in future. |
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