“This paper reviews the endocannabinoid system and focuses on the role of endocannabinoids in bone metabolism and their potential use in the management of conditions associated with bone loss.
The endocannabinoid system uses tissue-specific lipid ligands and G protein-coupled transmembrane receptors to regulate neurological, metabolic, and immune responses. Recent studies demonstrate that the endocannabinoid system influences bone metabolism. With the increasing use of endocannabinoid mimetics, e.g. tetrahydrocannabinol (THC) and cannabidiol (CBD), endocannabinoids’ involvement in bone growth and remodeling has become clinically relevant.
This literature review is based upon a search of Pubmed and Google Scholar databases, as of June 2019, for all English-language publications relating to cannabinoids and bone. We evaluated retrieved articles for relevance, experimental design, data acquisition, statistical analysis, and conclusions.
Preclinical studies establish a role for endocannabinoids in bone metabolism. These studies yield complex and often contradictory results attributed to differences in the specific experimental model examined. Studies using human cells or subjects are limited.
In vitro and animal models document that endocannabinoids participate in bone biology. The relevance of these observations to humans is not clear. The increasing chronic use of medical and recreational cannabis underscores the need to better understand the role of endocannabinoids in human bone metabolism. Moreover, it is important to evaluate the role of endocannabinoids as a therapeutic target to prevent and treat disorders associated with bone loss.”
“Osteoporosis is a skeletal disease with decreased bone mass and alteration in microarchitecture of bone tissue, and these changes put patients in risk of bone fracture. As a common symptom of osteoporosis and complication of osteoporotic fracture, chronic pain is a headache for clinicians. Nonsteroidal anti-inflammatory drugs (NSAIDs), selective COX-2 inhibitors and opioid drugs can temporarily reduce osteoporotic pain but have relevant side effects, such as addiction, tolerability and safety. The review summarized the recent advancements in the study of CB receptors in osteoporosis and osteoporotic pain and related mechanisms.
Recent studies indicated the two nociceptive receptors, cannabinoid receptor (CB) and transient receptor potential vanilloid type 1 (TRPV1) channel, are co-expressed in bone cells and play important role in the metabolism of bone cells, suggesting that dualtargeting these 2 receptors/channel may provide a novel approach for osteoporotic pain. In addition, both CB receptor and TRPV1 channel are found to be expressed in the glial cells which play vital role in mediating inflammation, chronic pain and metabolism of bone cells, suggesting a role of glial cells inosteoporotic pain.
Multiple-targeting against glial cells, CB receptors and TRPV1 channel may be one effective therapeutic strategy for osteoporotic pain in the future, following the elucidation of the complicated mechanism.”
“The endocannabinoid system (ECS) is an extensive endogenous signaling system with multiple elements, the number of which may be increasing as scientists continue to elucidate its role in human health and disease. The ECS is seemingly ubiquitous in animal species and is modulated by diet, sleep, exercise, stress, and a multitude of other factors, including exposure to phytocannabinoids, like Cannabidiol (CBD). Modulating the activity of this system may offer tremendous therapeutic promise for a diverse scope of diseases, ranging from mental health disorders, neurological and movement disorders, pain, autoimmune disease, spinal cord injury, cancer, cardiometabolic disease, stroke, TBI, osteoporosis, and others.”
“Bone is a dynamic tissue, whose homeostasis is maintained by a fine balance between osteoclast (OC) and osteoblast (OB) activity. The endocannabinoid/endovanilloid (EC/EV) system’s receptors are the cannabinoid receptor type 1 (CB1), the cannabinoid receptor type 2 (CB2), and the transient receptor potential cation channel subfamily V member 1 (TRPV1). Their stimulation modulates bone formation and bone resorption. Bone diseases are very common worldwide. Osteoporosis is the principal cause of bone loss and it can be caused by several factors such as postmenopausal estrogen decrease, glucocorticoid (GC) treatments, iron overload, and chemotherapies. Studies have demonstrated that CB1 and TRPV1 stimulation exerts osteoclastogenic effects, whereas CB2 stimulation has an anti-osteoclastogenic role. Moreover, the EC/EV system has been demonstrated to have a role in cancer, favoring apoptosis and inhibiting cell proliferation. In particular, in bone cancer, the modulation of the EC/EV system not only reduces cell growth and enhances apoptosis but it also reduces cell invasion and bone pain in mouse models. Therefore, EC/EV receptors may be a useful pharmacological target in the prevention and treatment of bone diseases. More studies to better investigate the biochemical mechanisms underlining the EC/EV system effects in bone are needed, but the synthesis of hybrid molecules, targeting these receptors and capable of oppositely regulating bone homeostasis, seems to be a promising and encouraging prospective in bone disease management.”
“Bone is a complex tissue of the with unique properties such as high strength and regeneration capabilities while carrying out multiple functions. Bone regeneration occurs both in physiological situations (bone turnover) and pathological situations (e.g. fractures), being performed by osteoblasts and osteoclasts. If this process is inadequate, fracture nonunion or aseptic loosening of implants occurs and requires a complex treatment.
Exogenous factors are currently used to increase bone regeneration process when needed, such as bisphosphonates and vitamin D, but limitations do exist. Cannabinoid system has been shown to have positive effects on bone metabolism. Cannabinoids at bone level mainly act on two receptors called CB-1 and CB-2, but GPR55, GPR119, TPRV1, TPRV4 receptors may also be involved. The CB-2 receptors are found in bone cells at higher levels compared to other receptors.
Endocannabinods represented by anandamide and 2-arachidonoylglycerol, can stimulate osteoblast formation, bone formation and osteoclast activity. CB-2 agonists including HU-308, HU-433, JWH133 and JWH015 can stimulate osteoblast proliferation and activity, while CB-2 antagonists such as AM630 and SR144528 can inhibit osteoclast differentiation and function. CB-1 antagonist AM251 has been shown to inhibit osteoclast differentiation and activity, while GPR55 antagonist cannabidiol increases osteoblast activity and decreases osteoclast function.
An optimal correlation of dose, duration, moment of action and affinity can lead to an increased bone regeneration capacity, with important benefits in many pathological situations which involve bone tissue. As adverse reactions of cannabinoids haven’t been described in patients under controlled medication, cannabinoids can represent future treatment for bone regeneration.”
“Some time ago a wrote a blog about the use of certain components of the marijuana plant. It was a fairly short blog which I will include here. More and more states are proposing the legalization of marijuana. There are numerous health claims about hemp oil which is a derivative of Cannabis. There may be merit to these claims possibly by the action of the Cannabis on stem cells. Below is the blog and I will expand more on it:
“We use to think that marijuana was bad for one’s health. Now we are not so sure about it. We need to clarify things a bit.
Cannabinoids, the active components of cannabis (Cannabis sativa) extracts, have attracted the attention of human civilizations for centuries for a variety of uses. The use of Cannabis or Marijuana (scientific name is Cannabis sativa) came before we were able to discover the active portion or substrate. This substrate is called endocannabinoid system. The endocannabbinoid system has a number of components. The system consists of lipids, the receptors for the lipids and certain metabolic enzymes. The Cannabinoid signaling regulates cell proliferation, differentiation and it reduces cell aptosis or death. These receptors are found in the very early stages of life. The results of the Cannabinoid receptors depend upon molecular targets and cellular context involved. There are two main receptors which are called CB1 and CB2 receptors. These receptors seem to be involved in neural degeneration. They seem to be involved in all three germ layer formations. . CB1 and CB2 show opposite patterns of expression, the former increasing and the latter decreasing along neuronal differentiation. It is thought that the CB2 receptors may be most important. Recently, endocannabinoid (eCB) signaling has also been shown to regulate proliferation and differentiation of hematopoietic and mesenchymal stem cells, with a key role in determining the formation of several cell types in peripheral tissues, including blood cells, adipocytes, osteoblasts/osteoclasts and epithelial cells. The developmental regulation of cannabinoid receptor expression and cellular/sub-cellular localization, together with their role in progenitor/stem cell biology, may have important implications in human health and disease. Bone marrow and stem cells make endocannabinoids, these endocannabinoids interact with the cannabinoid receptors (Cannabinoid receptors have been found in nearly every cell in the human body). If cannabinoids can enhance stem cell migration and proliferation, this could be a powerful therapy. For instance, if you can increase the numbers and movement of stem cells to an injured tissue, you could vastly enhance the healing process. Lastly, the synthetic cannabinoid HU-210 is about 100-1000x times more potent than THC from Cannabis and this synthetic agent has been found to be neurogenic. Meaning that HU-210 can cause new neurons (brain cells) in the brain to form. However this study was done in rats…and humans are different from rats. Will I prescribe medical marijuana for my stem cell patients? At present I do not think I have enough information to make an intelligent decision about this. I suspect if some day I do prescribe this it will be some derivative of Cannabis. There are certainly some intriguing aspects of Cannabis but I feel the jury is still out. I suspect we will certainly hear more about this. Thanks Dr. P”
That was the blog I wrote some time ago. At this juncture I am getting closer to utilizing some component of Cannabis. I have further looked at the literature and there seems to be some very good science on the effect of Cannabis on stem cell workings. One of the intriguing aspects of the CB2 receptor is that it is found mostly in the immune system. At the University of South Carolina, a team discovered that THC could reduce the inflammation associated with autoimmune diseases by suppressing the activity of certain genes involved in the immune response. Its presence there interests scientists because the immune system triggers inflammation, and studies show marijuana can have an anti-inflammatory effect. When we start talking about the immune system we have a host of implications. We are aware that many diseases of aging may have some basis as an auto-immune disease. One of these that interests me is Osteoporosis. There may be both receptors at work. CB-2 works on the immune system while CB-1 is induced during osteogenic differentiation. As I have written in another blog, Very Small Embryonic Like Stem Cells may have a profound effect on the course of Osteoporosis. The next question is can we prime these cells additionally with Cannabis and take things to the next level. More to come I am sure. Dr. P.”
“During these last years, the CB2cannabinoid receptor has emerged as a potential anti-inflammatory target in diseases such as multiple sclerosis, amyotrophic lateral sclerosis, Huntington’s disease, ischemic stroke, autoimmune diseases, osteoporosis, and cancer. However, the development of clinically useful CB2 agonists reveals to be very challenging. Allosterism and biased-signaling mechanisms at CB2 receptor may offer new avenues for the development of improved CB2 receptor-targeted therapies. Although there has been some exploration of CB1 receptor activation by new CB1 allosteric or biased-signaling ligands, the CB2 receptor is still at initial stages in this domain. In an effort to understand the molecular basis behind these pharmacological approaches, we have analyzed and summarized the structural data reported so far at CB2 receptor.”
“In past years, medical interest in Δ9-tetrahydrocannabinol (THC), the major psychoactive ingredient of the Cannabis plant, has been renewed due to the elucidation of the endocannabinoid system and diverse other receptor targets involved in biological cannabinoid effects.
The present study therefore investigates the impact of THC on the migration of mesenchymal stem cells (MSCs) which are known to be involved in various regenerative processes such as bone healing.
Collectively, this study demonstrates THC to exert a promigratory effect on MSCs via a CB1 receptor-dependent activation of p42/44 MAPK phosphorylation. This pathway may be involved in regenerative effects of THC and could be a target of pharmacological intervention.” https://www.ncbi.nlm.nih.gov/pubmed/29285308
“Cannabinoid receptor 2 (CNR2) has a critical role in osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). CNR2 expression was found to be downregulated in osteoporotic patients.
The present study aimed to investigate the functionality of CNR2 in restoring osteogenic differentiation and mineralization of BMSCs isolated from osteoporotic patients.
The results demonstrated that overexpression of CNR2 in osteoporotic BMSCs increased ALP activity, promoted expression of osteogenic genes and enhanced deposition of mineralized extracellular matrix. In addition, phosphorylation of p38 MAPK was found to be increased by overexpression of CNR2.
In conclusion, the present study indicated that restoration of CNR2 recovered the osteogenic differentiation of BMSCs isolated from osteoporotic patients. This finding may provide a novel strategy for a treatment approach for osteoporosis.”
“Osteoporosis is a progressive bone disorder characterised by imbalance between bone building (anabolism) and resorption (catabolism). Most therapeutics target inhibition of osteoclast-mediated bone resorption, but more recent attention in early drug discovery has focussed on anabolic targets in osteoblasts or their precursors. Two marketed agents that display anabolic properties, strontium ranelate and teriparatide, mediate their actions via the G protein-coupled calcium-sensing and parathyroid hormone-1 receptors, respectively. This review explores their activity, the potential for improved therapeutics targeting these receptors and other putative anabolic GPCR targets, including Smoothened, Wnt/Frizzled, relaxin family peptide, adenosine, cannabinoid, prostaglandin and sphingosine-1-phosphate receptors.”