Background & Aims

Chronic post-surgical pain (CPSP) is one of the most frequent complications of surgery. Nerve injury during surgery has been implicated in the development of CPSP and some (but not all) patients with CPSP have neuropathic pain1. Over-the-counter analgesics like non-steroidal anti-inflammatory drugs as well as corticosteroids such as dexamethasone are widely used following surgery. However, recent findings suggest that inhibiting the inflammatory response in acute pain states increases the odds of developing chronic pain2. We hypothesized that activated serum (also known as ACS), which effectively treats chronic pain disorders such as osteoarthritis3, trigeminal neuralgia4, and neuropathic spine disease5, will also be effective in chronic postoperative settings by restoring adaptive immune states.

Methods

The postoperative incision model was performed based on the Cowie et al. protocol6. Following the surgery, 6–8-week-old mice of both sexes received 0.5 mg/kg/day of the corticosteroid dexamethasone, or 1% DMSO subcutaneously for six consecutive days. To prepare ACS, 50 mL of whole blood was taken from each human subject using a special syringe (Orthogen, Dusseldorf, Germany). After incubation for 7 hours at 37 °C, the blood-filled syringes were centrifuged for 15 min at 5000 rpm then the serum supernatant was removed. On days 2 and 4, ACS and control serum were injected via the intraplantar (i.pl., 10 µl) or intraperitoneal (i.p., 0.2 ml) routes. Additionally, to investigate the effect of ACS on neuropathic pain, ACS was injected intrathecally in the mice having undergone spared nerve injury (SNI)7. Tactile allodynia was measured using von Frey filaments at regular intervals post-surgery using the up-and-down method of Dixon8, and 50% paw-withdrawal thresholds were calculated.

Results

We found that dexamethasone produced robust inhibition of allodynia on day 6 after incisional paw surgery (t6 = 10.5, p = 0.01). However, dexamethasone substantially delayed recovery to the baseline such that the duration of the overall pain episode was significantly prolonged after steroid treatment (t6 =2.4, p = 0.03), lasting 100 days instead of 20 days in saline-treated mice. Activated serum prevented dexamethasone-induced prolongation of pain when injected i.pl. (F4,33 = 6.4, p = 0.0006), and when injected i.p. (F5, 31 = 2.9, p = 0.03). Furthermore, when injected intrathecally, ACS significantly reduced SNI-induced mechanical allodynia.

Conclusions

Our results indicate that dexamethasone treatment results in long-lasting hyperalgesia in a commonly used mouse model of post-operative pain. ACS injections prevented long-lasting pain in the dexamethasone-induced chronic post-surgical model as well as the SNI model.

References

1.Haroutiunian, S., Nikolajsen, L., Finnerup, N. B. & Jensen, T. S. The neuropathic component in persistent postsurgical pain: a systematic literature review. Pain 154, 95–102 (2013).
2.Parisien, M. et al. Acute inflammatory response via neutrophil activation protects against the development of chronic pain. Sci Transl Med 14, eabj9954 (2022).
3.Motaal, F. K. A.-E., Elganzoury, A. M., Fathalla, M. M. & Abdulkareem, O. Low-dose intra-articular autologous conditioned serum in treatment of primary knee osteoarthritis. Egypt Rheumatol Rehabil 41, 98–102 (2014).
4.Aghamohammadi, D., Sharifi, S., Shakouri, S. K., Eslampour, Y. & Dolatkhah, N. Autologous conditioned serum (Orthokine) injection for treatment of classical trigeminal neuralgia: results of a single-center case series. J Med Case Reports 16, 183 (2022).
5.Godek, P. Use of Autologous Serum in Treatment of Lumbar Radiculopathy Pain. Pilot Study. Ortop Traumatol Rehabil 18, 11–20 (2016).
6.Cowie, A. M. & Stucky, C. L. A Mouse Model of Postoperative Pain. Bio Protoc 9, e3140 (2019).
7.Decosterd, I. & Woolf, C. J. Spared nerve injury: an animal model of persistent peripheral neuropathic pain. Pain 87, 149–158 (2000).
8.Chaplan, S. R., Bach, F. W., Pogrel, J. W., Chung, J. M. & Yaksh, T. L. Quantitative assessment of tactile allodynia in the rat paw. J Neurosci Methods 53, 55–63 (1994).

Presenting Author

Anahita Oveisi

Poster Authors

Anahita Oveisi, MSc

Graduate Student

McGill University

Lead Author

E-mail

Lucas V. Lima

PhD

McGill University

Lead Author

E-mail

Mohamad Karaky

McGill University

Lead Author

E-mail

Julio Reinecke

PhD

Orthogen AG

Lead Author

E-mail

Peter Wehling

PhD

Orthogen AG

Lead Author

E-mail

Jeffrey Mogil

McGill University

Lead Author

E-mail

Topics

  • Models: Chronic Pain - Neuropathic