Cannabis for Wounds and Injuries
Cannabis has been used to treat topical wounds such as cuts and burns for millennia. Now, modern research is investigating the science behind cannabis’ ability to treat topical injuries, and is discovering exactly how vast a role the endocannabinoid system plays in the maintenance of healthy skin and wound healing.
Cannabis and wound healing in history
The historical medical texts of various different cultures mention the use of cannabis in topical preparations to treat cuts, scrapes and burns. Egyptian papyri note the use of topical antiseptic preparations thought to be made from cannabis mixed with fat; Greek writers from the 1st century BCE record the use of cannabis to treat horses suffering from wounds and sores, as well as to treat nosebleed in humans.
The medieval French herbalist Ruellius recorded in his 1536 treatise De Natura Stirpium that cannabis extract could be used to treat wounds and ulcers; a few decades later, the renowned German botanist Tabernaemontanus recommended a mixture of butter and cannabis leaves to be applied to burns.
In 1649, the eminent British herbalist Nicholas Culpeper recorded that cannabis could be used to treat burns and bleeding, due to its antiseptic properties. In 1751, British herbalist Thomas Short wrote in his Medicina Britannica that a preparation of cannabis could be used to treat burns, wounds, insect bites and ulcers.
Modern research into wound healing & cannabis
In the modern era, researchers have investigated the ability of cannabis and cannabis preparations to reduce pain, swelling and bleeding associated with cuts and burns, and to aid in the repair of epidermal tissue.
Research conducted thus far has provided ample evidence that cannabis has a strong analgesic, anti-inflammatory and antiseptic effect. Indeed, it appears that the endocannabinoid system is fundamentally involved with the process of healing itself, and has a vital role to play in the formation of scar tissue.
Wound healing & the endocannabinoid system
The endocannabinoid system plays a major role throughout the entire process of wound healing. Immediately after an injury occurs, levels of anandamide in the affected tissues rise, and provide an analgesic effect by acting on the CB₁-receptors present in the peripheral nerves.
A 2010 study conducted at the University of California found that if a synthetic compound known as URB937 was administered to rats and mice with peripheral injuries, levels of anandamide increased and the analgesic effect became stronger. URB937 exerts this effect by inhibiting the fatty acid amide hydrolase (FAAH) enzyme, which is responsible for the degradation of anandamide.
Another 2010 study conducted at the China Medical University found that in mice inflicted with skin incisions, the number of cells expressing CB₁-receptors increased at the injury site. The increase in CB₁-expressing cells began six hours after injury occurred, peaked at five days post-injury, and reduced to baseline levels by fourteen days post-injury.
At first, the majority of new CB₁-expressing cells at the injury site were mononuclear cells (such as red blood cells and specialized immune cells known as monocytes) that are known to mediate inflammation and the immune response; after several days, fibroblastic cells (which are vital to wound healing and scar formation) began to dominate. While it is not clear exactly what mechanisms are at work, it is evident that anandamide and the CB₁-receptors are involved in the process.
Cannabis & wound healing in the internal organs
As well as wounds affecting the epidermis and cutaneous tissue, the endocannabinoid system has a role to play in the healing of injuries to the internal organs, particularly to the epithelium (the smooth layer of cells lining the surface of organs and other bodily structures).
In the human colon, the epithelial tissue expresses both CB₁ and CB₂-receptors. In normal tissue, CB₁-receptors are more commonly expressed, and in abnormal conditions (such as in individuals with inflammatory bowel disease) CB₂-receptors begin to dominate. The CB₁-receptors are routinely involved in the closure of wounds to the colonic epithelium; if damage is chronic, CB₂-receptors become crucial to ensuring that excess scarring does not occur.
In the corneas, injury to the epithelial tissue causes the local release of endogenous cannabinoid and vanilloid receptor agonists that are believed to assist in the process of wound-healing. In a 2010 study, researchers treated human corneal epithelial cells in vitro with WIN55,212-2 and capsaicin—a CB₁-receptor and a vanilloid-receptor agonist—to determine the role each receptor played. They found that activating either receptor led to the transactivation of the epidermal growth factor receptor, which is vitally important for the regeneration of damaged epidermal and epithelial tissue.
In periodontal tissue, an upsurge in cells expressing CB-receptors was also observed immediately subsequent to injury. As well as this, an increase in anandamide levels in patients who had just undergone periodontal surgery was noted. Administration of AM251 and AM630, synthetic selective antagonists of the CB₁ and CB₂-receptors respectively, was observed to cause significant reductions in fibroblast numbers—suggesting that agonists of the CB-receptors promote fibroblast survival and therefore expedite wound-healing.
Cannabinoids & cirrhosis of the liver
In the liver, chronic tissue damage and inflammation (such as that caused by alcoholism or hepatitis) promotes the wound-healing response, causing fibroblast cells to migrate to the damaged area and begin the process of fibrosis (scar formation). Over time, the overproduction of fibrous connective tissue causes cirrhosis, and inhibits the liver’s ability to function normally.
In this instance, presence of anandamide in high levels could increase the rate of fibrosis and therefore the severity of cirrhosis. Anandamide is an agonist of the CB-receptors; conversely, presence of a antagonist such as cannabidiol could block the effect and slow the rate of fibrosis.
A 2006 study on mice published in Nature Medicine demonstrated that administration of a synthetic CB₁-receptor antagonist, SR141716A, inhibited the wound-healing response to acute hepatic injury, and slowed progression of cirrhosis in three types of chronic injury—supporting the idea that CBD and similar antagonists can help to treat cirrhosis.
The CB₂-receptor & hepatic wound healing
Interestingly, the CB₂-receptor has its own unique role to play in the onset and progression of fibrosis in the liver. Usually present in lower concentrations than CB₁-receptors, their numbers increase dramatically during fibrogenesis (production of fibrous tissue) and after injury.
A 2007 study on mice showed that for mice genetically modified to lack CB₂-receptors, fibrosis was significantly worsened—indicating that presence of CB₂-receptors in typical mice inhibits fibrogenesis. It is thought that the CB₂-receptors exert this effect by causing apoptosis (programmed cell death) of the fibroblasts; when CB₂-receptors are limited in number or absent, the fibroblasts can accumulate and fibrous tissue can thus build up more rapidly .
Hemp seed oil for wound healing
Although hemp seed contains no cannabinoids (except residual traces from the production process), it may be useful in treating burns, cuts and other external wounds due to its unique balance of omega-3 and -6 essential fatty acids, which are present in optimum levels for human health.
Topical hemp seed oil preparations are also helpful for treating cuts and minor wounds
Although very few formal studies have been done into the ability of hemp seed itself to treat topical injuries, there have been multiple papers written on the ability to improve wound-healing of essential fatty acids in general. There has also been one clinical trial into the uses of topically-applied hemp seed oil, which concluded that it had a good ability to heal mucosal skin wounds after eye, nose and throat surgery.
Thus, cuts, burns, lacerations and other similar injuries may be treatable both with hemp seed oil and with cannabinoid-rich cannabis preparations. For injuries to the internal tissues or organs, cannabinoids have a definite role to play, but further investigation is required so that targeted therapies can be developed. With such a complex and finely-tuned system, incorrect dosages or cannabinoid ratios could cause the opposite effect to the intended one.