Effects of orally administered OP-1206 alpha-CD with loxoprofen-Na on walking dysfunction in the rat neuropathic intermittent claudication model

Prostaglandin E1 Treatment for Lumbar Spinal Canal Stenosis: Review of the Literature

BACKGROUND

The important pathophysiologic factor of neurogenic intermittent claudication (NIC) in lumbar spinal canal stenosis (LSCS) has been reported to be the reduction in intraneural blood flow and a state of relative ischemia in nerve tissues. Prostaglandin E1 (PGE1) presumably improves symptoms in patients with LSCS by improving the blood flow in the cauda equina and nerve roots through its vasodilation and antiplatelet aggregation effects. The purpose of the study was to summarize the results of previous studies regarding PGE1 treatment for LSCS and to describe the details of PGE1 treatment to all physicians who take care of patients with LSCS.

METHODS

Review of the literature.

RESULTS

There are 3 PGE1-related products that have been used clinically for the treatment of LSCS: PGE1, lipo-PGE1, and limaprost (PGE1 derivative). Experimental studies have been performed to verify the efficacy of PGE1 treatment for LSCS. Many studies have reported clinical outcomes of PGE1 treatment in patients with LSCS. Overall, previous studies examining PGE1 treatment for LSCS demonstrate improvement in several clinical outcome measures such as the visual analog scale, Japanese Orthopaedic Association score, and NIC distance, although most of the studies have only short-term follow-up.

CONCLUSIONS

Based on the results of previous studies, PGE1 treatment may be an option as a conservative treatment for LSCS. However, future studies with high-quality and long-term follow-up are necessary. Future studies also should include refinement of indications, administration period, as well as comparisons between PGE1 treatment and other conservative treatments such as epidural injection.

Therapeutic effect of epidurally administered lipo-prostaglandin e1 agonist in a rat spinal stenosis model

BACKGROUND

A lipo-prostaglandin E1 agonist is effective for the treatment of neurological symptoms of spinal stenosis when administered by an oral or intravenous route. we would like to reveal the therapeutic effect of an epidural injection of lipo-prostaglandin E1 on hyperalgesia in foraminal stenosis.

METHODS

A total of 40 male Sprague-Dawley rats were included. A small stainless steel rod was inserted into the L5/L6 intervertebral foramen to produce intervertebral foraminal stenosis and chronic compression of the dorsal root ganglia (DRG). The rats were divided into three groups: epidural PGE1 (EP) (n = 15), saline (n = 15), and control (n = 10). In the EP group, 0.15 µg.kg-1 of a lipo-PGE1 agonist was injected daily via an epidural catheter for 10 days from postoperative day 3. In the saline group, saline was injected. Behavioral tests for mechanical hyperalgesia were performed for 3 weeks. Then, the target DRG was analyzed for the degree of chromatolysis, chronic inflammation, and fibrosis in light microscopic images.

RESULTS

From the fifth day after lipo-PGE1 agonist injection, the EP group showed significant recovery from mechanical hyperalgesia, which was maintained for 3 weeks (P < 0.05). Microscopic analysis showed much less chromatolysis in the EP group than in the saline or control groups.

CONCLUSIONS

An epidurally administered lipo-PGE1 agonist relieved neuropathic pain, such as mechanical hyperalgesia, in a rat foraminal stenosis model, with decreasing chromatolysis in target DRG. We suggest that epidurally administered lipo-PGE1 may be a useful therapeutic candidate for patients with spinal stenosis.

Pathophysiology, diagnosis and treatment of intermittent claudication in patients with lumbar canal stenosis

Spinal nerve roots have a peculiar structure, different from the arrangements in the peripheral nerve. The nerve roots are devoid of lymphatic vessels but are immersed in the cerebrospinal fluid (CSF) within the subarachnoid space. The blood supply of nerve roots depends on the blood flow from both peripheral direction (ascending) and the spinal cord direction (descending). There is no hypovascular region in the nerve root, although there exists a so-called water-shed of the bloodstream in the radicular artery itself. Increased mechanical compression promotes the disturbance of CSF flow, circulatory disturbance starting from the venous congestion and intraradicular edema formation resulting from the breakdown of the blood-nerve barrier. Although this edema may diffuse into CSF when the subarachnoid space is preserved, the endoneurial fluid pressure may increase when the area is closed by increased compression. On the other hand, the nerve root tissue has already degenerated under the compression and the numerous macrophages releasing various chemical mediators, aggravating radicular symptoms that appear in the area of Wallerian degeneration. Prostaglandin E1 (PGE1) is a potent vasodilator as well as an inhibitor of platelet aggregation and has therefore attracted interest as a therapeutic drug for lumbar canal stenosis. However, investigations in the clinical setting have shown that PGE1 is effective in some patients but not in others, although the reason for this is unclear.

Blood flow analysis of compressed nerve root after intravenous injection of lipo-prostaglandin E1

Prostaglandin E(1) (PGE(1)) is a potent vasodilator as well as an inhibitor of platelet aggregation and has therefore attracted interest as a therapeutic drug for lumbar canal stenosis. However, investigations in the clinical setting have shown that PGE(1) is effective in some patients but not in others, although the reason for this is unclear. The aim of the present study was to measure changes in intraradicular blood flow after intravenous injection of lipo-PGE(1) (0.15 microg/kg) using a laser Doppler flow meter in control model and nerve root compression model. Then, the nerve root in which blood flow was measured was removed and examined histologically. Intravenous injection of lipo-PGE(1) also resulted in marked increase of blood flow in the uncompressed nerve roots of the control group, but caused minimal enhancement of blood flow at the sites of nerve root compression exhibiting Wallerian degeneration. It is concluded that lipo-PGE(1) has less effect on markedly degenerated nerve roots than it does on those that are normal.

The efficacy of prostaglandin E1 derivative in patients with lumbar spinal stenosis

STUDY DESIGN

Randomized controlled trial.

OBJECTIVE

To examine the effect of limaprost, an oral prostaglandin (PG) E1 derivative, on health-related quality of life (HRQOL) in patients with symptomatic lumbar spinal stenosis (LSS), compared to etodolac, a NSAID.

SUMMARY OF BACKGROUND DATA

Limaprost, an oral PGE1 derivative, was developed in Japan to treat numerous ischemic symptoms of thromboangiitis obliterans (TAO) and LSS. Previous studies have demonstrated the effectiveness of limaprost in the symptoms in patients with LSS. However, the evidence for effect on patient-reported outcomes, such as patient's HRQOL or satisfaction, is limited.

METHODS

This study was conducted at 4 study sites in Japan. Briefly, inclusion criteria were: age between 50 and 85 years; presence of both neurogenic intermittent claudication (NIC) and cauda equina symptoms (at least presence of bilateral numbness in the lower limbs); and MRI-confirmed central stenosis with acquired degenerative LSS. Limaprost (15 microg/d) or etodolac (400 mg/d) was administered for 8 weeks. The primary outcome was Short Form (SF)-36, and the secondary outcomes were the verbal rating scale of low back pain and leg numbness, walking distance, subjective improvement, and satisfaction.

RESULTS

A total of 79 participants were randomized (limaprost:etodolac = 39:40). Thirteen participants withdrew from the study (limaprost:etodolac = 5:8) and 66 completed the study (limaprost:etodolac = 34:32). Comparisons showed that limaprost resulted in significantly greater improvements in the SF-36 subscales of physical functioning, role physical, bodily pain, vitality, and mental health. Limaprost was also significantly better than etodolac for leg numbness, NIC distance, and subjective improvement and satisfaction. In the subgroup analysis stratified by symptom severity, limaprost seemed more effective for milder symptoms. No serious adverse effects were reported in either treatment group.

CONCLUSION

In this study, limaprost was found to be efficacious on most outcome measures, such as HRQOL, symptoms and subjective satisfaction, in LSS patents with cauda equina symptoms.

Compensatory neovascularization after cauda equina compression in rats

STUDY DESIGN

An experimental study of compensatory neovascularization after cauda equina compression in rats.

OBJECTIVE

To explore the possibility that cauda equina compression induces compensatory neovascularization accompanied by an increase in the expression of vascular endothelial growth factor (VEGF).

SUMMARY OF BACKGROUND DATA

VEGF is a potent promoter of neovascularization that follows ischemia. Studies suggest that compression of the cauda equina causes ischemic changes that in turn cause an increase in VEGF expression that induces neovascularization. The mechanisms by which neovascularization develops in a compressed cauda equina are unknown.

METHODS

Two rectangular-solid pieces of silicone rubber were implanted in the fourth and sixth epidural spaces of rats (1 piece in each space); in the sham control group, no rubber was implanted. VEGF expression in the compressed cauda equina was assessed by immunohistochemistry and Western blotting. Ischemia and neovascularization of the cauda equina were assessed by immunostaining for hypoxia-inducible factor-1 alpha (HIF-1 alpha) and 5-bromodeoxyuridine (BrdU). The unpaired Student t test was used for statistical analysis (P < 0.05).

RESULTS

At 14 and 21 days after surgery, ischemic changes were observed, as indicated by expression of HIF-1 alpha. In the compression group at 21 and 28 days after surgery, Western blot analysis showed a significant increase in VEGF expression (P < 0.05). VEGF was localized to pericytes, Schwann cells, and macrophages. In the compression group at 21 days after surgery, neovascularization was observed, as indicated by an increase in the number of proliferating endothelial cells (which stained positive for BrdU).

CONCLUSION

Cauda equina compression seems to induce compensatory neovascularization of the cauda equina accompanied by an increase in VEGF expression.