Scientists Found the Endocannabinoid System in Connective Tissue Cells, With Implications for Pain and Bodywork | Research

The takeaway

Fibroblasts and other connective tissue cells express CB1 and CB2 receptors and endocannabinoid enzymes, suggesting the endocannabinoid system helps regulate pain, inflammation, and tissue remodeling in muscles and fascia.

Read this if you're interested in how the endocannabinoid system relates to muscle pain, fascia, and manual therapy.

Fibroblast CB1 receptor levels nearly equaled fat cell levels and increased with inflammation

What the researchers found

Using bioinformatics analysis of publicly available gene expression data, the researcher found that fibroblasts, myofibroblasts, chondrocytes, and synoviocytes all express CB1 receptors, CB2 receptors, and the enzymes that make and break down endocannabinoids.

Fibroblast CB1 levels were notably high, nearly matching adipocyte (fat cell) levels. CB1 expression increased when fibroblasts were exposed to inflammatory cytokines or mechanical stretching.

The endocannabinoid system in these tissues was found to affect fibroblast remodeling (through lipid rafts at focal adhesions), reduce cartilage destruction by decreasing metalloproteinase enzymes, and modulate pain and inflammation in myofascial tissues.

The author suggested this system may help explain the biological basis of myofascial trigger points and fibromyalgia symptoms, and that manual therapies, diet modifications, and pharmaceutical approaches can all influence endocannabinoid activity.

Why it matters

The discovery that connective tissue cells have a functional endocannabinoid system provides a biological framework for understanding how cannabis-based treatments might address musculoskeletal pain, and why manual therapies like massage may work partly through endocannabinoid mechanisms.

The numbers in context

Fibroblast CB1 levels nearly equaled adipocyte levels. CB1 upregulated by inflammatory cytokines and mechanical stretching. CB1, CB2, and endocannabinoid enzymes detected in fibroblasts, myofibroblasts, chondrocytes, and synoviocytes.

How the study worked

Bioinformatics review using microarray data from the GEO database (NCBI) to characterize endocannabinoid system expression in fibroblasts and related cells. Combined with a narrative review of endocannabinoid system biology relevant to bodywork and manual therapy.

What this study cannot tell us

The endocannabinoid system expression was identified through database mining of microarray data, not direct tissue measurements. The connections to trigger points and fibromyalgia were speculative. The claims about bodywork upregulating endocannabinoids were not directly tested.

How to read the evidence

This combines bioinformatics data mining with a narrative review. While the gene expression findings are real, the clinical implications for bodywork and trigger points are speculative.

When this study was published

Published in 2008. Research on peripheral endocannabinoid system function has expanded, with topical cannabinoid products now widely marketed for musculoskeletal pain.

The bigger picture

This study bridged cannabinoid science and manual therapy, proposing that the endocannabinoid system is part of how the body regulates pain and remodeling in connective tissues. This concept has gained traction in integrative medicine and pain research.

Questions still open

Does massage or manual therapy measurably increase endocannabinoid levels in treated tissues? Could topical cannabinoids effectively target the endocannabinoid system in fascia and muscle? Are endocannabinoid levels altered in fibromyalgia patients?

Common questions

Does this mean massage releases endocannabinoids?

The author proposed this possibility based on the finding that mechanical stretching upregulated CB1 in fibroblasts, but this was not directly tested in living tissue during massage. Some subsequent research has explored exercise-induced endocannabinoid release.

Could cannabinoids help with fibromyalgia?

The presence of endocannabinoid receptors in connective tissue provides a theoretical basis for this. Some clinical studies have explored cannabinoids for fibromyalgia with mixed results, and the topic remains under investigation.

Read the original research

Expression of the endocannabinoid system in fibroblasts and myofascial tissues.

Journal of bodywork and movement therapies, 12(2), 169-82

View on PubMed ↗Publisher’s paper ↗

Citation

McPartland, John M. (2008). Expression of the endocannabinoid system in fibroblasts and myofascial tissues.. Journal of bodywork and movement therapies, 12(2), 169-82. https://doi.org/10.1016/j.jbmt.2008.01.004