New aid to wound healing?

Polymerisation of the synthetic
epidermis spray (c) Paindaveine et al

Recent research suggests that a synthetic skin spray could aid in wound healing by limiting the
formation of exuberant granulation tissue.  

Due to their nature, horses are prone to injuring themselves. Wounds on the lower legs are particularly likely to heal slowly, often involving exuberant granulation tissue (EGT). This excessive tissue growth, commonly known as "proud flesh," poses a significant challenge to equine wound management, as it hampers further healing by protruding from the wound site. 

 

A team of researchers based in France has been investigating the efficacy of a novel synthetic epidermis spray (SES)* in promoting wound healing. Led by Charlotte C Paindaveine from the Ecole Nationale Vétérinaire de Lyon, the researchers conducted a small-scale clinical trial to compare the healing outcomes of experimental surgical wounds treated with SES spray versus those treated with a standard bandaging technique. 

 

The study, detailed in a report published in PLoS One, involved creating standardised surgical wounds on the lower limbs of six adult Standardbred mares. These wounds were then subjected to treatment with either SES or a traditional bandaging method.

 

Hypergranulation and exudation of
the lateral wounds (right leg) treated
with bandaging, compared with wounds 
on left leg treated with spray.
(c) Paindaveine et al 

For the SES treatment, the spray, which comprised  ultraviolet polymerizable methacrylate monomers, comonomers, crosslinker and a photoinitiator was applied to the wound. The researchers explain that this layer was then polymerised using a 395 nm, 20 x 30 cm, 40 mW/cm2 UV light for 60 seconds at a distance of approximately 30 cm (Fig 1). They repeated the same procedure to fix a second layer of the product. The SES was only applied on day 0. No further application was made.

 

The control treatment consisted of a nonadherent permeable dressing secured with conforming cotton gauze and held in place with a cohesive bandage, which would be a common treatment of choice for superficial wounds in a field setting. The control treatment was repeated every 4 days until the end of the study to mimic field veterinary follow-up.

 

Wounds were assessed daily for the SES treatment group, and every 4 days for the control / bandaged group.

 

The researchers report that the synthetic epidermal spray allowed healing without the production of EGT but it did not reduce the median wound healing time compared to a standard bandaging technique.

 

They add that the exuberant granulation tissue observed in the control group that did not receive the SES decreased without any trimming procedure during the 60-day period.

 

They conclude: “The SES is potentially an interesting alternative for the management of secondary intention wound healing of superficial and non-infected distal limb wounds in adult horses because of its economical and practical aspects. 

 

*Novacika®, Cohesive S.A.S, France

 

 

 

For more details, see: 

 

Charlotte C. Pandaveine, Benoit Bihin, Olivier M. Lepage (2024) 

The effects of a synthetic epidermis spray on secondary intention wound healing in adult horses. PLoS ONE 19(3): e0299990. 

https://doi.org/10.1371/journal.pone.0299990

Antibacterial actions of mesenchymal stromal cells

Infected wound healing could be helped by factors secreted by mesenchymal stromal cells. 

Mention “bacteria” and we tend to think of the individual microorganisms that we see growing in laboratory cultures (the so-called “planktonic” forms.) However, in nature it is more common for bacteria to form biofilms – communities of different microbes that become embedded in a slimy extracellular matrix. Biofilms protect the microbes from both antibacterial substances and the immune response of the host.

Biofilms contribute to chronic inflammation and delayed healing of wounds, and are not readily detectable using current routine diagnostic methods. However, biofilm infections should be suspected in equine limb wounds that are not healing as expected. Treatment is based on repeated debridement and application of topical antimicrobial therapy.

 

Mesenchymal stromal cells (MSCs) are cells, isolated from different sites, that can differentiate into other types of cells. They take part in the inflammatory, proliferative, and remodelling phases of tissue repair.

 

Previous work has shown that secretions from MSCs promote wound repair by stimulating fibroblast migration in the skin and promoting development of new blood vessels. They also have antibacterial properties. 

 

A recent study looked at the effect of mesenchymal stromal cells on biofilms.

 

Research by Charlotte Marx and colleagues at the Cornell University College of Veterinary Medicine looked at the effect of mesenchymal stromal cells on biofilms, using an equine skin explant model.

 

They found that secreted factors from equine MSC (collectively referred to as the MSC secretome) significantly decreased the viability of methicillin-resistant Staphylococcus aureus (MRSA) in mature biofilms.

 

They also showed that equine MSCs secrete the cytokine CCL2 that boosts the antimicrobial activity of equine keratinocytes by stimulating the production of cathelicidin and ß-defensin.

 

Reporting their work in the journal Tissue Engineering and Regenerative Medicine, they conclude: “Collectively, these data contribute to our understanding of the MSC secretome's anti-microbial properties, both directly by killing bacteria and indirectly by stimulating immune responses of surrounding resident skin cells, thus further supporting the value of MSC secretome-based treatments for infected wounds.”

 

 

For more details, see:

 

Mesenchymal stromal cell-secreted CCL2 promotes antibacterial defense mechanisms through increased antimicrobial peptide expression in keratinocytes 

Charlotte Marx, Sophia Gardner, Rebecca M. Harman, Bettina Wagner, Gerlinde R. Van de Walle.

Tissue Engineering and Regenerative Medicine (2021) Vol 10 (12) pp1666-1679

https://dx.doi.org/10.1002/sctm.21-0058

Effect of light on wound healing

 Do light emitting diodes (LEDs) emitting infrared or red light help wound healing?

 Research conducted at the Swedish University of Agricultural Science, Uppsala, Sweden looked at the effect of pulsating visible red light (wavelength 637nm) and near infrared light (NIR) (wavelength 956nm) on experimental skin wounds on horses.

 

Peter Michanek and colleagues used eight healthy adult standardbred horses in the randomised controlled study. The research team made a circular (2cm diameter) surgical skin wound on both sides of the neck of each horse.

 

The wound on one side was chosen at random to receive the light treatment. The opposite side was left untreated. Light therapy followed a standardised protocol and was given by the same operators throughout the study. Treatment was applied daily (comprising red light for 95 seconds and NIR light for 185 seconds) 5 days a week for 4 weeks. 

 

Wound healing was monitored by someone who did not know whether the wound had received light treatment or not.

 

The researchers found that the difference in wound area between treated and control wounds did not differ significantly at any stage of the study. It actually took longer for treated wounds to heal completely compared with the untreated wounds. The researchers point out that, although significant, the difference was small and probably not of clinical significance.

 

They conclude that, in this study, pulsating visible red light or NIR was no better than no treatment in promoting healing of experimental skin wounds.

 

For more details, see: 

 

Effect of infra-red and red monochromatic light on equine wound healing.

P Michanek, T Toth, E Bergström, H Treffenberg-Petterson, A Bergh.

Equine Vet J (20211) 53, 143

https://doi.org://10.1111/evj.13266

Medical Grade Honey prevents surgical site infections

Abdominal surgery is a major undertaking in horses, and not without significant risks to the patient. Colic operations, especially those that involve opening the gut wall, risk contaminating the wound with bacteria such that surgical site infection (SSI) is a potential complication.

Medical grade honey (MGH) has been used successfully to treat established infections in both humans and animals, and has been shown to improve wound healing of equine lacerations and significantly reduce infection rate.

 

Would the application of MGH help abdominal surgical wounds to heal?

 

A study by Gustafsson and colleagues investigated whether medical grade honey gel, applied on the linea alba during wound closure, would decrease the prevalence of incisional infections in horses undergoing colic surgery.

 

Figure 1: Example of intra-lesional application of
L-Mesitran Soft (MGH) following colic surgery

The linea alba is the fibrous band that runs along the midline of the belly, between the abdominal muscles.  Being composed of fibrous connective tissue it contains no major blood vessels making it a suitable site for incisions for abdominal surgery.

 

In this prospective randomized controlled trial, 108 horses that underwent colic surgery at Koret School of Veterinary Medicine in Israel were enrolled. Horses were randomized to control or treatment (MGH) group. In the treatment group, following closure of the linea alba, MGH gel (L-Mesitran Soft) was placed in the incision followed by routine closure of subcutaneous tissue and skin (Figure 1).

 

Horses were excluded from the study if they needed a second abdominal surgery (n=4) or did not survive for at least two weeks post-operatively (n=15).

 

The clinicians report that a single intra-incisional application of MGH gel strongly reduced incisional infection rate from 32.5% (13/40) in the control group to 8.2% (4/49) in the treatment group (p=0.02).

 

No adverse reactions were observed with the subcutaneous application of MGH after colic surgery.

 

A full report is published in the Equine Veterinary Journal.

 

The authors conclude that intra-incisional application of MGH gel on the linea alba is a simple and rapid procedure that was safe and did not result in any adverse effects. A single local prophylactic treatment with MGH in the abdominal incision during surgery significantly decreased the prevalence of incisional infections in horses undergoing colic surgery. They suggest that more research is necessary to explore this promising approach in indications outside the equine colic field, e.g., in surgeries with a high risk of SSIs.

 

For more details, see:

 

Intra‐incisional medical grade honey decreases the prevalence of incisional infection in horses undergoing colic surgery: a prospective randomised controlled study.

Gustafsson, K., Tatz, A.J., Slavin, R.A., Sutton, G.A., Dahan, R., Abu Ahmad, W. and Kelmer, G.

Equine Veterinary Journal (2020)

https://doi.org/10.1111/evj.13407

 

An interview with Dr Gustafsson is available on YouTube:

https://youtu.be/q2yf7a0f5Ds

Blankets and food intake

Horses wearing a blanket or rug in the winter ate less hay than did their non-blanketed neighbours, a recent study found.

Healthy horses maintain their body temperature within a narrow range (98.5°F to 101°F / 36.9°C to 38.3°C) despite a wide variation in environmental conditions.

In cold weather they use various physiological and behavioural methods to conserve body heat, such as piloerection, shivering, facing away from the wind. Eating roughage generates heat and so helps maintain body temperature.

Research by Michelle De Boer and others at the University of Wisconsin–River Falls, assessed the effect of wearing a blanket on horses’ feed intake, body weight (BW), and body condition scores (BCSs). A report of the work is published in the Journal of Equine Veterinary Science,

The project was carried out over the winter of 2019-2020, when environmental temperatures typically average about -10°C.

Sixteen adult horses were recruited to the study: eight wore a medium weight blanket; the others did not. All horses lived in a dry lot and were fed grass-legume hay ad lib. The researchers recorded hay intake and monitored horses’ body weight and condition score before during and at the end of the study.

Horses without blankets maintained their body weight and condition score despite the cold weather.

The researchers found that the average estimated dry matter intake (DMI) was lower for blanketed horses (2.31% BW) than for non-blanketed ones (2.51% BW) – equivalent to an average of 1kg daily.

The results suggest horses wearing blankets conserve energy leading to decreased feed intake. Horse owners may save (a small amount of) money from reduced hay and labour costs when using a blanket.

The researchers emphasised that, when blanketing a horse, it is important to monitor them regularly to evaluate health, welfare, and BW and condition.

For more details, see:

Dry Matter Intake, Body Weight, and Body Condition Scores of Blanketed and Nonblanketed Horses in the Upper Midwest
Michelle De Boer, Alexandra Konop, Bailey Fisher, Krishona Martinson
Journal of Equine Veterinary Science (2020) vol 94, 103239 

https://doi.org/10.1016/j.jevs.2020.103239

Potential new treatment for joint infections

A new therapy could help overcome joint infections in horses. Researchers at North Carolina State University developed a platelet-rich plasma (PRP) lysate that, when teamed with antibiotics, can eradicate bacterial biofilms common in joint infections. The work, which received funding from the Morris Animal Foundation, has been published in the Journal of Orthopaedic Research.

"This could really provide a more effective way of clearing a joint infection quickly so that the horse does not suffer long-term consequences of joint damage," said Dr. Lauren Schnabel, Associate Professor of Equine Orthopaedic Surgery at North Carolina State University, a primary investigator of the study. "For any horse's well-being, it's important to make them as comfortable as possible, as quickly as possible to avoid laminitis and other complications."

Penetrating wounds of the joint in horses are potentially life-threatening. Joint infection is a challenge to overcome, frequently requiring repeated flushing and prolonged antibiotic treatment. Even if the infection is cleared, it may leave permanent damage, resulting in degenerative joint disease.

Successful treatment is hindered by the tendency for some bacteria to form biofilms in the joint. A biofilm is a sticky, slimy shield that forms around bacteria. It protects them from the body’s immune cells. The bacteria in the biofilm tend to be metabolically inactive, which makes them more resistant to antibiotics.

Platelets are a rich source of protein growth factors that promote healing. Platelet Rich Plasma (PRP) is made by processing a sample of the patient’s own blood to increase the number of platelets and growth factors it contains. PRP has found various uses in regenerative medicine, including the treatment of tendon and ligament injuries.

To create their PRP lysate, the research team took blood from their small herd of horses and isolated the platelets. Then they packed 50 times the number of platelets that would be found in an equal amount of blood into their product. This is over 10x the concentration of platelets typically found in conventional PRP. They felt that this super-concentrated product would be more effective at stopping infections.

The researchers lysed the platelets to release antimicrobial peptides - proteins that attack bacteria. They separated out the antimicrobial peptides and then, after testing them against common bacteria, all the horses' peptides were pooled together for one lysate product. 

Then, samples of synovial fluid were seeded with bacteria in the laboratory to produce bioflilms.

The researchers tested three methods to attack the biofilms; antibiotics alone, lysate alone and a combination of antibiotics and lysate.

They found that antibiotics alone were completely ineffective. The lysate alone significantly decreased the bacterial load. The antibiotic and lysate combination, however, completely eradicated the biofilms and bacteria.

Dr. Schnabel added that her team has used this experimental therapy on horses with great results. Because the process to create the lysate is both complicated and expensive, her team is trying to find a way to produce it more efficiently. They also are trying to identify the exact peptides responsible for the antibacterial properties, so they can be synthesized and production scaled up to reach the greatest number of horses.

If successful, this approach also has the potential to help other species, including humans. For example, biofilm formation and infection are a significant problem for people with metal implants, such as those used in joint replacement surgeries.

Dr. Jessica Gilbertie, first author on this publication and former Morris Animal Foundation Fellowship trainee under the mentorship of Dr. Schnabel, is working on making PRP lysate from other species, including dogs, because they also can suffer from biofilm formations related to surgical procedures.

For more details, see:

Platelet‐rich plasma lysate displays antibiofilm properties and restores antimicrobial activity against synovial fluid biofilms in vitro

Jessica M. Gilbertie, Thomas P. Schaer, Alicia G. Schubert, Megan E. Jacob, Stefano Menegatti, R. Ashton Lavoie, Lauren V. Schnabel

Journal of Orthopaedic Research (2020)

https://doi.org/10.1002/jor.24584

Repairing wounds with honey

Horses are renowned for their ability to attract wounds.  Under ideal conditions, surgical repair may lead to rapid (“first intention”) healing. However, wound breakdown is not uncommon, particularly in lower limb injuries. Factors such as infection and movement are significant problems.

Research from Israel suggests that applying medical grade honey to the wound, as it is repaired, may help control infection and reduce wound breakdown.

The study, from the Koret School of Veterinary Medicine, at the Hebrew University of Jerusalem, has been published in the Equine Veterinary Journal.

Eleven veterinarians were involved – between them treating 127 lacerations. Most wounds (30%) were on the lower limb. Upper limb wounds accounted for 28% and head wounds a further 24%.

Wounds were repaired using a standardised protocol, with some being chosen at random to have medical grade honey (MGH*) applied to the wound. (Medical grade honey has been sterilised by gamma radiation to eradicate any bacterial spores - such as Bacillus spp and Clostridium spp - that may be found in raw honey.)

In all, 69 wounds received an application of MGH; 58 did not.

The study’s authors report that, compared to control horses, those treated with MGH were more likely to heal completely, and to have no signs of infection. No adverse effects of the MGH were reported.

They conclude that intralesional application of MGH to lacerations before closure may help prevent infection and wound breakdown. 

They point out that this was a non-blinded clinical trial relying on subjective assessments of wound healing and as such was open to bias. They suggest that larger, blinded studies focusing on wounds at a specific location with more objective assessment should be pursued.

For more details, see:

Intralesional application of medical grade honey improves healing of surgically treated lacerations in horses

H. H. Mandel, G. A. Sutton, E. Abu, G. Kelmer.

Equine Veterinary Journal 2019

https://doi.org/10.1111/evj.13111

*L‐mesitran soft^® Triticum, Maastricht, the Netherlands.