Jiangang Shi

PTEN deletion prevents ischemic brain injury by activating the mTOR signaling pathway

It is increasingly clear that the tumor suppressor PTEN (phosphatase and tensin homolog deleted on chromosome 10) is a negative regulator of neuronal cell survival. However, its molecular mechanisms remain poorly understood. Here we found that PTEN/mTOR is critical for controlling neuronal cell death after ischemic brain injury. Male rats were subjected to MCAO (middle cerebral artery occlusion) followed by pretreating with bpv (pic), a potent inhibitor for PTEN, or by intra-cerebroventricular infusion of PTEN siRNA. bpv (pic) significantly decreased infarct volume and reduced the number of TUNEL-positive cells. We further demonstrated that although bpv (pic) did not affect brain injury-induced mTOR protein expression, bpv (pic) prevented decrease in phosphorylation of mTOR, and the subsequent decrease in S6. Similarly, down-regulation of PTEN expression also reduced the number of TUNEL-positive cells, and increased phospho-mTOR. These data suggest that PTEN deletion prevents neuronal cell death resulting from ischemic brain injury and that its neuroprotective effects are mediated by increasing the injury-induced mTOR phosphorylation.

Increased miR‐195 aggravates neuropathic pain by inhibiting autophagy following peripheral nerve injury

Following peripheral nerve injury (PNI) microglia proliferates and adopts inflammation that contributes to development and maintenance of neuropathic pain. miRNAs and autophagy are two important factors in the regulation of inflammation. However, little is known about whether miRNAs regulate neuroinflammation and neuropathic pain by controlling autophagy. In the study, we demonstrated that miR‐195 levels were markedly increased in rats subjected to L5 spinal nerve ligation (SNL). Upregulated miR‐195 was also found in spinal microglia of rats with SNL. The overexpression of miR‐195 contributed to lipopolysaccharide‐induced expression of proinflammatory cytokines IL‐1β, TNF‐α, and iNOS in cultured microglia. Upregulated miR‐195 also resulted in increased mechanical and cold hypersensitivity after PNI, whereas miR‐195 inhibition reduced mechanical and cold sensitivity. We further demonstrated that PNI significantly inhibited microglial autophagy activation, whereas miR‐195 inhibitor treatment increased autophagy activation and suppressed neuroinflammation in vivo and in vitro. More important, autophagy inhibition impaired miR‐195 inhibitor‐induced downregulation of neuroinflammation and neuropathic pain. Additionally, ATG14 was identified as the functional target of miR‐195. Conclusions: These data demonstrated that miR‐195/autophagy signaling represents a novel pathway regulating neuroinflammation and neuropathic pain, thus offering a new target for therapy of neuropathic pain.

Surgical strategy for multilevel severe ossification of posterior longitudinal ligament in the cervical spine.

Study Design A retrospective clinical study was conducted. Objective To compare surgical outcome of anterior approach (corpectomy and fusion) with that of posterior approach (laminoplasty or laminectomy and instrumented fusion) for the treatment of multilevel severe ossification of the posterior longitudinal ligament (OPLL) in the cervical spine, and simultaneously to investigate the potential benefits of instrumented fusion after laminectomy by comparing it with laminoplasty. Summary of Background Data Surgical strategy for multilevel severe OPLL in the cervical spine still remains controversial. Although the advantages of anterior decompression and fusion have been reported earlier, it becomes more technically demanding and risky with the increasing narrowing rate and extent of ossification. Laminoplasty has been used to relieve cord decompression posteriorly, but results are not always good. It also has potential risks of ossification progression and kyphotic deformity after operation. Methods A total of 75 cervical patients with multilevel severe OPLL were included in this study. Twenty-two patients underwent anterior corpectomy and fusion. Among the patients undergoing posterior approach, laminectomy and instrumented fusion was performed on 28 patients and laminoplasty on 25 patients. The radiologic findings including plain radiographs, computed tomography scan, and magnetic resonance images were reviewed, and surgical outcome was assessed using the Japanese Orthopedic Association scoring system. The radiologic and clinical data were compared between 3 groups of different surgical processes. Results Radiologic studies showed preoperative cervical lordosis, occupying rate and extent of OPLL were comparable between 3 groups in this study, but the postoperative cervical lordosis after anterior corpectomy or laminectomy and instrumented fusion was significantly larger than that of after laminoplasty. Postoperative Japanese Orthopedic Association score and improvement rate of neurologic function after anterior corpectomy were significantly higher than those after laminoplasty, and the results after laminectomy and instrumented fusion were in the middle of results of above 2 processes. The main complication after anterior decompression was cerebrospinal fluid leakage, whereas posterior approach was complicated with a high incidence of C5 palsy and axial pain. Conclusions Anterior corpectomy and fusion was significantly more effective for multilevel severe OPLL when compared with posterior laminoplasty in the cervical spine. If having technical difficulties and posterior decompression was alternatively performed, instrumented fusion was recommended to help to restore cervical lordosis and produce better results according to this study.

Obesity and Risk of Hip Fracture in Adults: A Meta-Analysis of Prospective Cohort Studies

Background Many observational studies assessed the association between obesity and risk of hip fracture in adults, but reported controversial results. Our goal was to evaluate the association between obesity and risk of hip fracture in adults by conducting a meta-analysis of prospective cohort studies. Methods Three databases, PubMed, Embase and Web of Science, were searched through May 2012 to identify eligible cohort studies. Either a fixed- or a random-effects model was used to calculate the pooled relative risk (RR) with its 95% confidence interval (95%CI). Results Fifteen prospective cohort studies involving a total 3,126,313 participants were finally included into this meta-analysis. Overall, adults with obesity compared with the normal weight group had a significantly decreased risk of hip fracture (RR: 0.66, 95% CI 0.57 to 0.77, P<0.001). Meta-analyses by the adjusted status of RRs also suggested adults with obesity compared with the reference group had a significantly decreased risk of hip fracture (adjusted RR: 0.48, 95% CI 0.39 to 0.58, P<0.001; unadjusted RR: 0.66, 95% CI 0.56 to 0.78, P<0.001). Subgroup analyses by gender suggested individuals with obesity had a significantly decreased risk for developing hip fracture compared with the reference group in both men (RR 0.54, 95% CI 0.48 to 0.60, P<0.001) and women (RR 0.70, 95% CI 0.58 to 0.84, P<0.001). No evidence of publication bias was observed in this meta-analysis. Conclusions This meta-analysis of prospective cohort studies suggests that obesity significantly decreases the risk of hip fracture in adults, and obesity is probably a protective factor of hip fracture in adults.

Upregulated miR-29b promotes neuronal cell death by inhibiting Bcl2L2 after ischemic brain injury

It is increasingly clear that microRNAs (miRNAs) play an important role in controlling cell survival. However, the functional significance of miRNAs in ischemic brain injury remains poorly understood. In the present study, we assayed the expression levels of miR-29b after ischemic brain injury, and defined the target genes and biological functions of miR-29b. We found that the miR-29b levels were significantly increased in rat brain after transient middle cerebral artery occlusion and neurons after oxygen–glucose deprivation. Moreover, ectopic expression of miR-29b promoted neuronal cell death, whereas its repression decreased cell death. Furthermore, we verified that miR-29b directly targeted and inhibited Bcl2L2 gene expression, and then increased neuronal cell death. Importantly, Bcl2L2 overexpression rescued neuronal cell death induced by miR-29b. These results suggest an important role of miR-29b in regulating neuronal cell death, thus offering a new target for the development of therapeutic agents against ischemic brain injury.

Clinical classification of cauda equina syndrome for proper treatment

Background and purpose Cauda equina syndrome (CES) is a severe complication of lumbar spinal disorders; it results from compression of the nerve roots of the cauda equina. The purpose of this study was to evaluate the clinical usefulness of a classification scheme of CES based on factors including clinical symptoms, imaging signs, and electrophysiological findings. Methods The records of 39 patients with CES were divided into 4 groups based on clinical features as follows. Group 1 (preclinical): low back pain with only bulbocavernosus reflex and ischiocavernosus reflex abnormalities. Group 2 (early): saddle sensory disturbance and bilateral sciatica. Group 3 (middle): saddle sensory disturbance, bowel or bladder dysfunction, motor weakness of the lower extremity, and reduced sexual function. Group 4 (late): absence of saddle sensation and sexual function in addition to uncontrolled bowel function. The outcome including radiographic and electrophysiological findings was compared between groups. Results The main clinical manifestations of CES included bilateral saddle sensory disturbance, and bowel, bladder, and sexual dysfunction. The clinical symptoms of patients with multiple-segment canal stenosis identified radiographically were more severe than those of patients with single-segment stenosis. BCR and ICR improved in groups 1 and 2 after surgery, but no change was noted for groups 3 and 4. Interpretation We conclude that bilateral radiculopathy or sciatica are early stages of CES and indicate a high risk of development of advanced CES. Electrophysiological abnormalities and reduced saddle sensation are indices of early diagnosis. Patients at the preclinical and early stages have better functional recovery than patients in later stages after surgical decompression.

Surgical technique: Hemilaminectomy and unilateral lateral mass fixation for cervical ossification of the posterior longitudinal ligament.

BackgroundSurgical approaches for cervical ossification of the posterior longitudinal ligament (OPLL) include anterior, posterior, or combined decompression with or without fusion. The goal of surgery is to decompress the spinal cord while maintaining the stability and sagittal alignment of the cervical spine. C5 palsy has been reported as a postoperative complication of cervical laminectomy or laminoplasty characterized as motor weakness of the muscles supplied with C5 nerve roots. Several studies have shown this phenomenon was partially attributable to posterior shift of spinal cord.Description of TechniqueThe rationale for choosing hemilaminectomy is to control postoperative posterior shift of the spinal cord and afford more stability by preserving ligamentous attachments and posterior bony elements as much as possible. After a fixation system of lateral mass screws and rods is installed unilaterally, laminae are removed from the underlying dura using a high-speed burr and Kerrison laminectomy rongeur on the other side. The spinous processes are preserved.Patients and MethodsPatients with multilevel continuous/mixed cervical OPLL are good candidates for this technique. We retrospectively reviewed 146 patients who had multilevel continuous/mixed cervical OPLL and underwent surgery from January 2006 to January 2010. Neurologic condition was evaluated using the improvement ratio (IR) of the Japanese Orthopaedic Association (JOA) score for cervical myelopathy.ResultsThe mean JOA score increased from 10 points before surgery to 14 points at last followup. The mean IR of neurologic function (JOA score) was 59%. C5 palsy was not observed in any patient after decompression, and cervical lordosis changed from 8.7° preoperatively to 9.1° at last followup.ConclusionsFor patients with multilevel continuous/mixed cervical OPLL without fixed kyphosis, multilevel hemilaminectomy with unilateral lateral mass fixation is an effective alternative technique.Level of EvidenceLevel IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Intervertebral thoracic disc calcification associated with ossification of posterior longitudinal ligament in an eleven-year-old child.

Study Design. Intervertebral disc calcification of T6–T7, T7–T8 discs associated with ossification of posterior longitudinal ligament (OPLL) in a child is reported. Objective. To discuss the natural history and management of calcification of T6–T7, T7–T8 discs with OPLL. Summary of Background Data. Calcified intervertebral discs are rare in children. Cervical disc calcification has already been described. However, thoracic disc calcification associated with OPLL has not been reported. Methods. An 11-year-old boy presented with progressive back pain for 6 months. Neurologic examination showed numbness in both lower extremities. The knee jerk reflex of the patient was hypertonic. The muscle strength of both lower extremities were Grade 4, with reduction. He was treated with a lumbar belt for 2 weeks. Results. Initial thoracic spine radiograph and CT scan showed two adjacent calcified discs of T6–T7, T7–T8 associated with T6–T7 OPLL, resulting in marked spinal canal stenosis. His neurologic symptoms subsided and his back pain disappeared after a 2-week conservative treatment. Three months later CT scan showed that the calcification of T6–T7, T7–T8 discs was aggravated, but the T6–T7 OPLL was relieved. Conclusion. The natural history of intervertebral disc calcification is usually benign. In this case, the improvement of OPLL is associated with the stabilization of the maturely fused calcified disc. Spontaneous resolution of the OPLL and recovery of normal neurologic function can be expected with conservative treatment.

MicroRNA-320a Regulates the Osteogenic Differentiation of Human Bone Marrow- Derived Mesenchymal Stem Cells by Targeting HOXA10

Background/Aims: Human bone marrow-derived mesenchymal stem cells (hMSCs) are a promising cell source for bone engineering owing to their high potential to differentiate into osteoblasts. The bone morphogenetic protein-inducible gene homeobox a10 (HOXA10) is a critical regulator of osteogenesis. The objective of the present study was to identify microR-NAs (miRNAs) targeting HOXA10 and examine the effects on the osteogenic differentiation of hMSCs. Methods: Based on in silico analysis, HOXA10-targeting miRNAs were selected and their regulatory roles in osteoblast differentiation were investigated. Results: Six HOXA10-targeting miRNAs were identifIed by computational analysis, of which miR-320a was selected for further analysis because it was downregulated during osteogenic induction. Overexpression of miR-320a downregulated HOXA10 and significantly inhibited osteogenesis in hMSCs, as determined by the downregulation of the osteogenic markers Runx2, ALP, and OC and the inhibition of ALP activity and matrix mineralization, whereas miR-320a inhibition had the opposite effects. Furthermore, ectopic expression of HOXA10 (not including 3′-UTR) rescued the effects of miR-320a on osteogenic differentiation. Conclusion: These results suggest that miR-320a acts as a critical regulator of osteogenic differentiation of hMSCs by repressing its target HOXA10.

Study design: in vitro and in vivo assessment of bone morphogenic protein 2 combined with platelet-rich plasma on treatment of disc degeneration

ObjectiveOur aim was to investigate the biological effects of bone morphogenic protein 2 (BMP2) on the differentiation of bone marrow mesenchymal stem cells (BMSCs) into chondrocyte-like cells in platelet-rich plasma (PRP) gel in vitro. In addition, the effectiveness of BMP2-transduced BMSCs in combined with PRP gel to repair the degenerated intervertebral disc in a rabbit model was also evaluated.Summary of background dataPrevious studies have shown that tissue engineering provides many promising advantages to treating disc degeneration and may reverse the pathological process of disc degeneration.MethodsThe expressions of types I, II and X collagen, aggrecan and Sox9 of the BMP2-transduced BMSCs in monolayer or PRP gel were examined by reverse transcriptase polymerase chain reaction (RT-PCR). Sixty New Zealand white rabbits were divided into five groups: 12 normal controls; 12 puncture operated with only disc degeneration being induced; 12 PRP transplantation animals; 12 BMSC and PRP-transplantation animals; 12 BMP2-transduced BMSCs and PRP-transplantation animals. The effect of BMP2-transduced BMSCs on degenerated discs were evaluated by magnetic resonance image (MRI) scan, histology, immunohistochemistry and Western blot analysis.ResultsBMP2 could facilitate chondrogenic differentiation of BMSCs in monolayer or PRP gel. The discs treated with BMP2-transduced BMSCs exhibited relatively well-preserved nucleus pulposus (NP) structure. Significantly higher T2-weighted signal intensity and a greater amount of extracellular matrix were observed in the BMP2-transduced BMSC group compared with other groups. In addition, the presences of BMP2-transduced BMSCs were identified at week 12 postoperatively in vivo.ConclusionsBMP2-transduced BMSCs can maintain the chondrocyte-like phenotype in PRP gel in vitro, and the combined use of these two agents can significantly promote repair of the degenerated discs in vivo.