Strong relationship between dyslipidemia and the ectopic ossification of the spinal ligaments

M1 macrophage-derived oncostatin M induces osteogenic differentiation of ligamentum flavum cells through the JAK2/STAT3 pathway

Background

M1 macrophages (Mφs) are involved in osteogenic differentiation of ligamentum flavum (LF) cells and play an important role in heterotopic ossification. However, the mechanism by which M1 Mφs influence osteogenic differentiation of LF cells has not been studied.

Methods

The effect of conditioned medium including secretions of M1 Mφs (CM-M1) on LF cells was analyzed by GeneChip profiling and ingenuity pathway analysis (IPA). THP-1 cells were polarized into M1 Mφs and CM-M1 was used to induce LF cells. In addition, LF cells were induced by CM-M1 in the presence of cyclooxygenase 2 (COX-2) inhibitors or oncostatin M (OSM)-neutralizing antibodies. Based on the presence of OSM, knockout of OSMR or GP130 receptors, or addition of the Janus kinase 2 (JAK2) inhibitor AZD1480 or signal transducer and activator of transcription 3 (STAT3) inhibitor Stattic were examined for effects on osteogenic differentiation of LF cells. OSM secretion was quantified by ELISA, while qPCR and western blot were used to evaluate expression of osteogenic genes and receptor and signaling pathway-related proteins, respectively.

Results

GeneChip and IPA results indicate that the OSM signaling pathway and its downstream signaling molecules JAK2 and STAT3 are significantly activated. ELISA results indicate that OSM is highly expressed in cells treated with CM-M1 and lowly expressed in cells treated with CM-M1 and a COX-2 inhibitor. Besides, CM-M1 induces osteogenic differentiation of LF cells, which is weakened when COX-2 inhibitors or OSM-neutralizing antibody are added to it. Recombinant OSM could induce osteogenic differentiation of LF cells and upregulate expression of OSMR, GP130, phosphorylated (P)-JAK2, and P-STAT3. Upon knockdown of OSMR or GP130, or the addition of AZD1480 or Stattic, P-JAK2 and P-STAT3 expression were decreased and osteogenic differentiation was reduced.

Conclusion

M1 Mφ-derived OSM induces osteogenic differentiation of LF cells and the JAK2/STAT3 signaling pathway plays an important role.

Multilevel ossification of the posterior longitudinal ligament causing cervical myelopathy: An observational series of North American patients

Background

Few studies regarding ossification of the posterior longitudinal ligament (OPLL) outside of Asia currently exist in the literature. A set of patients with multilevel cervical OPLL causing symptomatic myelopathy or radiculopathy from a North American sample is analyzed.

Objective

The objective of this study was to describe the demographics, radiographic findings, and surgical outcomes of a cohort of North American patients with degenerative spondylosis presenting for operative management of multilevel (>3 segments) cervical OPLL.

Materials and Methods

Forty-three patients diagnosed with multilevel cervical OPLL and degenerative spondylosis presenting with symptomatic cervical myelopathy or radiculopathy were surgically treated over a 9-year period at a single tertiary care academic medical center. Radiographic measurements were performed on preoperative computed tomography and magnetic resonance imaging images of the cervical spine. Clinical outcomes included pre- and postoperative Nurick scores, 90-day readmission, complication, and revision surgery rates.

Results

The mean age was 66.1 ± 10.9 years with a mean latest follow-up time of 32.7 ± 16.4 months. Most patients had previous diagnoses of obesity (70.7%) and hypertension (55.8%). At least one-quarter of patients were diagnosed with type 2 diabetes (34.9%), hyperlipidemia (41.9%), cardiovascular disease (25.6%), or chronic kidney disease (25.3%). The most common OPLL subtype was segmental (39.5%) and spanned a mean of 3.54 ± 1.48 segments. Myelopathic symptoms were present in 88.4% of patients. All patients experienced significant neurologic improvement at 3-week and latest follow-up (P < 0.001 for both).

Conclusions

Obesity, diabetes, and other metabolic derangements in patients with existing cervical spondylosis may be risk factors for a particularly aggressive form of multilevel OPLL. Various operative approaches may be employed to achieve adequate neurologic recovery. Further workup for OPLL in patients with these risk factors may prove beneficial to ensure appropriate operative management.