The Microbiome and Major Ligament Injuries

A brand new topic today for The Biome Buzz, but after hearing the sports news earlier  this week, this really struck me as interesting and odd, so here goes…

This past Sunday, September 20^th, 7 players in the National Football League here in the USA tore their anterior cruciate ligaments (ACL).  7 in one day!   What on earth is going on though that make this injury so unbelievably common these days?!  As a big fan of sports, this has been a real bee in my bonnet these last few years.

Another anecdote, this one back in time:  10 years ago or so, one of my dogs tore his doggie version of an ACL just running outside to play.  When I met with the surgeon who was to repair Apollo’s leg, he told me flat out that veterinarians have been talking for the past few years about how much more common the injury has become and they have no idea why.  “He’ll likely tear the other hind leg at some point too,” he warned me, “Once one goes, so does the other.”  Sure enough, 3 or 4 years later leg #2 popped, with my poor dog doing nothing but walking across the lawn.

Why these injuries are becoming more common is unknown but a new article really got me to thinking after reading this new research.[i]   According to the paper, it’s important to know that 50% of patients who tear an ACL will develop osteoarthritis in the injured limb, called post-traumatic osteoarthritis (PTOA).  The veterinarian surgeon warned me about this too, by the way.  Anyway, I find it fascinating that in this newly published paper, researchers found that giving rodents oral antibiotics before such an injury reduces inflammation in the injured joint and slows down the progression of PTOA.

We already know that changes to the bacterial microbiome may reduce osteoarthritis inflammation, but next-to-nothing is known about changes to that biome prior to an injury.

The scientists gave antibiotics (an ampicillin/neomycin cocktail) to the animals for 6 weeks prior to the ACL rupture.  A microscopic examination 6 weeks after the injury showed that the animals  treated with antibiotics had less loss of cartilage at the injury site than did the untreated controls.  There was less inflammation in the treated animals, and present at the wound site were more macrophages, which are immune cells associated with healing.  What I think is actually the most interesting part of this research is that the antibiotics led to less inflammation in UNINJURED joints as well.

A summary of the research, which appears on Medical Express, points out that antibiotics are often prescribed for teens and young adults, who actively participate in sports, at the rate of 790 prescriptions per 1000 people.  I admit to being shocked by this sentence: “…therefore, gut dysbiosis (a microbial imbalance) may be more common than expected in young athletes suffering an articular injury. In this scenario, the gut dysbiosis may provide a benefit to these young people, if they suffer a joint injury.”[ii]  Wait…what?!

The overuse of antibiotics is already a major issue in this country and biome depletion is a known leading cause of many health issues, as you all know.  Call me crazy but doesn’t this seem an odd way of assessing this new data!  Bearing in mind, as I said above, that , “The results show that this particular antibiotic regime had a beneficial effect on the health of injured and uninjured joints…”  – would that not imply that there is some component of the microbiome that is causing joint inflammation, which may LEAD to the increase in these severe injuries?  We know these ligament tears are increasing in prevalence; in this study, giving antibiotics leads to better outcomes after surgically creating an injury, i.e. giving antibiotics reduces join inflammation.  To me this implies that the next step to study (apart from the obvious question: will giving antibiotics after the injury help speed healing, which the scientists say they will look at in future work) is can antibiotics prevent the injuries in the first place?  Or better still:  what bacteria are being shifted in giving the antibiotic that cause improve joint health?  But what do I know.

I’m really interested in these answers so stay tuned:  I’m watching this space to see where this research leads.

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[i] Melanie E. Mendez et al. Antibiotic Treatment Prior to Injury Improves Post-Traumatic Osteoarthritis Outcomes in Mice, International Journal of Molecular Sciences (2020). DOI: 10.3390/ijms21176424

[ii] https://medicalxpress.com/news/2020-09-antibiotic-pre-treatment-joint-inflammation.html