RESUMO
BACKGROUND:When the intervertebral disc is under stress, the hydraulic pressure generated inside the nucleus pulposus makes the annulus fibrosus extend outward and expand, and the annulus colagen fibers are stretched so that the extracelular matrix of annulus fibrosus cels is also under the pressure. In the intervertebral disc, aggrecan is the main component of proteoglycans, matrix metaloproteinase-2 is a major enzyme for extracelular matrix degradation, and tissue inhibitor of metaloproteinase is a multifunctional specific inhibition factor for matrix metaloproteinase activity. There is a mutual regulation between the latter two to keep the homeostasis between them. OBJECTIVE: To investigate the mechanism of cyclic tensile strain in the metabolism of intervertebral disc annulus matrix. METHODS:Rat anulus fibrosus cels were subjected to 2% or 10% cyclic tensile strain at 1.0 Hz for 2 and 12 hours using Flexcel4000 tension system. Then cels were colected and cultured in conditioned medium for gene and protein detection. Real-time quantitative PCR was used to detect mRNA expression of aggrecan, matrix metaloproteinases-2 and tissue inhibitor of metaloproteinase-2. Gelatin zymography was used to detect matrix metaloproteinases-2 activity. RESULTS AND CONCLUSION:The use of 2% cyclic tensile strain had no obvious effect on the stress fiber of actin cytoskeleton, whereas actin cytoskeleton was depolymerized in response to 10% cyclic tensile strain. The 2% cyclic tensile strain raised the expression of Aggrecan at 12 hours; whereas raised the matrix metaloproteinases-2 and tissue inhibitor of metaloproteinase-2 at 2 hours, both of which were in homeostasis; matrix metaloproteinases-2 activity had no significant changes. 10% cyclic tensile strain had no effect on the mRNA expression of Aggrecan. No matter stretching 2 or 12 hours, the matrix metaloproteinases-2 was up-regulated, and the tissue inhibitor of metaloproteinase-2 was down-regulated, both of which were not in balance. Moreover, the matrix metaloproteinases-2 activity was not significantly changed. These findings indicate that the mRNA expressions of Aggrecan, matrix metaloproteinases-2 and tissue inhibitor of metaloproteinase-2 alter in response to cyclic tensile strain in rat anulus fibrosus cels, and the tensile strain induces different mechano-responses in the actin cytoskeleton.
RESUMO
BACKGROUND:Percutaneous transforaminal endoscopic discectomy combined with radiofrequency annuloplasty is a minimaly invasive therapy for chronic discogenic low back pain, especialy suitable for lumbar disc herniation. OBJECTIVE:To evaluate the safety and short-term efficacy of percutaneous transforaminal endoscopic discectomy combined with radiofrequency annuloplasty for treatment of lumbar disc herniation. METHODS:Thirty-two patients with lumbar disc herniation were subjected to percutaneous transforaminal endoscopic discectomy combined with radiofrequency annuloplasty. Visual analogue scale and modified Macnab criteria were used to evaluate the relief of low back pain, and the Oswestry Disability Index was used for daily life evaluation of patients. Al the patients were folowed for 1-6 months, with an average of 3.5 months. RESULTS AND CONCLUSION:The operation was successfuly completed in al patients, and no complications such as damage to nerve and vascular systems occurred. Low back pain and living ability of the patients were improved obviously. Visual analog scale score and the Oswestry Disability Index were improved significantly after operation (P < 0.01); according to Macnnab's criteria, the results showed that at 1 week after the operation, the effective rate reached 94%; at 3 months after the operation, the effective rate was up to 97%. These findings indicate that percutaneous transforaminal endoscopic discectomy combined with radiofrequency annuloplasty in the treatment of lumbar disc herniation is confirmed in the short-term efficacy, and characterized as fewer complications and stable functional recovery.