Are Cannabinoids the Next Generation of Bone Drugs?
Friday, June 11th, 2010The original version of this article first appeared in the Lab Bench Science Column of the West Coast Leaf NewsPaper on June 4th 2010.
The Lab Bench
By Jahan Marcu
A research team from the School of Medicine at Temple University, Philadelphia, presented their preliminary cannabinoid and bone data at a scientific meeting in Anaheim, CA in April. Our results add to a growing body of scientific evidence, suggesting a prominent role for the endocannabinoid system in bone development. For the last year, researchers have been trying to reproduce and build upon previous work on cannabinoids and bone, specifically, by characterizing the effects of removing the CB1 and CB2 receptors from mice.
Few labs have published new discoveries regarding cannabis and bone. However, those that have are surprising so far. Some findings are so profound that the upcoming International Cannabinoid Research Society (ICRS) meeting will have a special symposium to discuss the bone data produced by just a few laboratories.
Research shows that bone cells have cannabinoid receptors and produce endocannabinoids. Bone cells express a lot of CB2 receptors and nerves that traverse our bones produce CB1 receptors. The `anti-cannabinoid’ receptor, GPR55, is also expressed in bone.
These receptors appear to work together to regulate bone health. Some clinical evidence supports the role of cannabinoids in various diseases. The Clinical Endocannabinoid Deficiency (Russo 2004) is thought to underlie many treatment- resistant conditions such as irritable bowel syndrome, fibromyalgia, and chronic pain. Recently, CB1 receptor mutations were linked to migraines, bi-polar disorder, and major depression (Monteleone 2010).
Now CB2 receptor mutations may be linked to lower human bone density and hand-bone strength. Research from Japan and France shows that mutations correlate to osteoporosis in post-menopausal women. The two studies looked at 2,626 elderly adults with and without osteoporosis. A study out in Russia analyzed the hand-bone strength of 574 adults and found that those with CB2 receptor muta- tions had weaker hand-bone strength (Yamada 2007, Karsak 2005, 2009). These all suggest that a less functional receptor is related to poor bone health.
Researchers have been studying how the body responds to traumatic brain injuries (TBI). When TBI occurs in a mouse, endocannabinoids are made and new bone is formed. Thus, cannabinoids may enhance the healing of bones in some instances such as fractures.
Genetically modified mice without the cannabinoid receptors have a deregulated skeleton. Depending on genetic makeup, the animals make too much or too little bone. So, research has shown that cannabinoids can both increase and decrease bone mass. However, all mice without cannabinoid receptors eventually develop severe osteoporosis (Bab 2008).
Plant cannabinoids such as CBDV, CBG, CBN, THC, and THCV may increase the number of bone stem cells in rats (Scutt 2007). Conversely, Anandamide has been shown to increase bone turnover by acti- vating osteoclasts, the cells that remodel or dissolve bone. CBD can inhibit osteoclasts. The infamous diet drug Rimonabandt, or SR141716A, is thought to prevent bone loss in mice by activating GPR55, not the CB1 receptor. Additionally, derivatives like WIN55,212 and some JWH compounds appear to severely inhibit osteoclasts from remodeling bone. Researchers have already speculated that cannabinoids represent a new generation of drugs that could treat a variety of bone diseases. For more information check out this recent review of the scientific literature, which discusses the role of the endocannabinoid system in bone disease and pathology.
