Genetic Background Dramatically Changed Whether Cannabinoid Receptor Knockouts Affected MS-Like Disease in Mice
The immune-modulating effects of CB2 receptor deletion on MS-like disease were completely dependent on mouse genetic background, disappearing when the knockout was bred into a different strain, with major implications for translating animal cannabinoid research to humans.
Quick Facts
What This Study Found
CB2 receptor knockout mice on a C57BL/6 background developed more severe EAE (MS model), consistent with prior reports. However, when the same CB2 knockout was bred into the Biozzi ABH background, the immune-enhancing effect of CB2 deletion was completely lost. Similarly, CB1 receptor and TRPV1 knockouts on the ABH background showed no disease alteration.
GPR55 knockout mice showed less severe disease on the C57BL/6 background (especially females) but only marginal effects on the ABH background. The authors concluded that non-psychoactive doses of medicinal cannabis have marginal influence on the MS immune response, with THC immunosuppression occurring only at sedative doses through CB1 rather than CB2 receptors.
Key Numbers
CB2 KO on C57BL/6: augmented EAE. CB2 KO on ABH: no effect. CB1 KO on ABH: no effect. TRPV1 KO on ABH: no effect. GPR55 KO on C57BL/6: reduced EAE (females). GPR55 KO on ABH: marginal effect.
How They Did This
EAE induction in multiple knockout mouse strains on two genetic backgrounds (C57BL/6 and Biozzi ABH). Gene knockouts: CB2 (two distinct knockouts), CB1, TRPV1, GPR55. Disease incidence and severity measured. Pharmacological THC challenge in both backgrounds.
Why This Research Matters
This study is a cautionary tale for cannabinoid research. Many conclusions about cannabinoid receptor roles in immunity come from one mouse strain. The finding that genetic background completely changes the outcome challenges the reliability of these conclusions and their translation to genetically diverse human populations.
The Bigger Picture
This study has profound implications for cannabinoid drug development. If receptor knockout effects vary this dramatically between mouse strains, predicting human responses from any single animal model is hazardous. It also suggests that the immune effects of cannabinoids in MS may be more modest than some preclinical studies suggest.
What This Study Doesn't Tell Us
Mouse EAE is an imperfect model of human MS. The ABH background may be more resistant to genetic perturbation generally. The knockout approach creates lifelong absence rather than acute modulation. Only EAE disease scores were used, not detailed immunological characterization on both backgrounds.
Questions This Raises
- ?Which mouse background better predicts human cannabinoid immune responses?
- ?Should all cannabinoid knockout studies be replicated on multiple backgrounds?
- ?Does the marginal immune effect mean cannabinoid treatments for MS work through mechanisms other than immune modulation?
Trust & Context
- Key Stat:
- CB2 knockout effects completely disappeared when bred into a different mouse strain
- Evidence Grade:
- Comprehensive multi-strain study with definitive negative findings; moderate evidence for the limitations of single-strain studies.
- Study Age:
- Published in 2013. This study has influenced how cannabinoid researchers design and interpret knockout studies.
- Original Title:
- Genetic background can result in a marked or minimal effect of gene knockout (GPR55 and CB2 receptor) in experimental autoimmune encephalomyelitis models of multiple sclerosis.
- Published In:
- PloS one, 8(10), e76907 (2013)
- Authors:
- Sisay, Sofia(2), Pryce, Gareth(10), Jackson, Samuel J(4), Tanner, Carolyn, Ross, Ruth A, Michael, Gregory J, Selwood, David L, Giovannoni, Gavin, Baker, David
- Database ID:
- RTHC-00735
Evidence Hierarchy
Tests effects in animals (usually mice or rats), not humans.
What do these levels mean? →Frequently Asked Questions
Does this mean cannabinoids do not help MS?
Not exactly. Sativex is approved for MS spasticity and clearly helps some patients. What this study shows is that the immune-modulating effects attributed to cannabinoid receptors in mouse models may be strain-specific and may not explain how cannabis helps MS patients. The benefits may be more symptomatic (anti-spastic, pain relief) than immune-modulating.
Why does genetic background matter so much?
Different mouse strains have different immune system characteristics, metabolism, and receptor expression patterns. When a gene is deleted, these background differences determine whether the loss is critical or compensated. This is why the same CB2 deletion caused more disease in one strain and had zero effect in another. Humans are far more genetically diverse than any mouse strain, making predictions even more challenging.
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Cite This Study
https://rethinkthc.com/research/RTHC-00735APA
Sisay, Sofia; Pryce, Gareth; Jackson, Samuel J; Tanner, Carolyn; Ross, Ruth A; Michael, Gregory J; Selwood, David L; Giovannoni, Gavin; Baker, David. (2013). Genetic background can result in a marked or minimal effect of gene knockout (GPR55 and CB2 receptor) in experimental autoimmune encephalomyelitis models of multiple sclerosis.. PloS one, 8(10), e76907. https://doi.org/10.1371/journal.pone.0076907
MLA
Sisay, Sofia, et al. "Genetic background can result in a marked or minimal effect of gene knockout (GPR55 and CB2 receptor) in experimental autoimmune encephalomyelitis models of multiple sclerosis.." PloS one, 2013. https://doi.org/10.1371/journal.pone.0076907
RethinkTHC
RethinkTHC Research Database. "Genetic background can result in a marked or minimal effect ..." RTHC-00735. Retrieved from https://rethinkthc.com/research/sisay-2013-genetic-background-can-result
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.