Analysis of cartilage-derived retinoic acid-sensitive protein in cerebrospinal fluid from patients with spinal diseases

Study Design. The expression of cartilage-derived retinoic acid-sensitive protein (CD-RAP) was measured in cerebrospinal fluid from patients with spinal diseases. Objectives. To quantify the levels of CD-RAP in human cerebrospinal fluid and to clarify its character. Summary of Background Data. Cartilage-derived retinoic acid-sensitive protein is a newly discovered, secreted molecule that is expressed during the chondrogenesis phase of endochondral bone formation and in articular cartilage. In recent studies CD-RAP has been detected in the serum of patients with melanoma and breast cancer, and it has been used to monitor tumor activity. However, the function of CD-RAP is unknown, and the expression of CD-RAP in human cerebrospinal fluid has never been reported. Methods. The concentration of CD-RAP in human cerebrospinal fluid was measured by enzyme-linked immunosorbent assay with antihuman CD-RAP antibodies. Cerebrospinal fluid samples were collected from two groups of patients. Group 1, the control group, consisted of 40 patients: 22 with trauma and 18 with gynecologic diseases. Group 2 consisted of 172 patients with spinal diseases: 5 with meningioma, 5 with neurinoma, 5 with arachnoid cyst, 30 with cervical spondylotic myelopathy, 35 with lumbar disc herniation, 56 with lumbar canal stenosis, and 36 with scoliosis. Results. The concentration of CD-RAP in the control group was 16.5 ± 8.3 ng/mL. The concentrations of CD-RAP in Group 2 were: 35.3 ± 14.7 ng/mL in meningioma, 23.5 ± 7.41 ng/mL in neurinoma, 26.0 ± 22.2 ng/mL in arachnoid cyst, 41.7±22.3 ng/mL in cervical myelopathy, 27.8 ± 14.7 ng/mL in lumbar disc herniation, 36.5 ± 18.4 ng/mL in lumbar canal stenosis, and 13.4 ± 7.48 ng/mL in scoliosis. The concentrations of CD-RAP in cervical myelopathy, lumbar canal stenosis, and lumbar disc herniation were significantly higher than in the control group (P < 0.001). Conclusions. The CD-RAP concentration was low in the control group, whereas it was significantly higher in spinal diseases that cause spinal stenosis. CD-RAP is expressed in cerebrospinal fluid as a result of damage to or stressing of neural structures and could be a marker for spinal diseases.