Effect of intralesional platelet-rich plasma (PRP) treatment on clinical and ultrasonographic parameters in equine naturally occurring superficial digital flexor tendinopathies - a randomized prospective controlled clinical trial

Exogenous interleukin-1 beta stimulation regulates equine tenocyte function and gene expression in three-dimensional culture which can be rescued by pharmacological inhibition of interleukin 1 receptor, but not nuclear factor kappa B, signaling

We investigated how Interleukin 1 beta (IL-1β) impacts equine tenocyte function and global gene expression in vitro and determined if these effects could be rescued by pharmacologically inhibiting nuclear factor-κB (NF-KB) or interleukin 1 signalling. Equine superficial digital flexor tenocytes were cultured in three-dimensional (3D) collagen gels and stimulated with IL-1β for two-weeks, with gel contraction and interleukin 6 (IL6) measured throughout and transcriptomic analysis performed at day 14. The impact of three NF-KB inhibitors on gel contraction and IL6 secretion were measured in 3D culture, with NF-KB-P65 nuclear translocation by immunofluorescence and gene expression by qPCR measured in two-dimensional (2D) monolayer culture. In addition, daily 3D gel contraction and transcriptomic analysis was performed on interleukin 1 receptor antagonist-treated 3D gels at day 14. IL-1β increased NF-KB-P65 nuclear translocation in 2D culture and IL6 secretion in 3D culture, but reduced daily tenocyte 3D gel contraction and impacted > 2500 genes at day 14, with enrichment for NF-KB signaling. Administering direct pharmacological inhibitors of NF-KB did reduce NF-KB-P65 nuclear translocation, but had no effect on 3D gel contraction or IL6 secretion in the presence of IL-1β. However, IL1Ra restored 3D gel contraction and partially rescued global gene expression. Tenocyte 3D gel contraction and gene expression is adversely impacted by IL-1β which can only be rescued by blockade of interleukin 1 receptor, but not NF-KB, signalling.

Equine Musculoskeletal Pathologies: Clinical Approaches and Therapeutical Perspectives-A Review

Musculoskeletal injuries such as equine osteoarthritis, osteoarticular defects, tendonitis/desmitis, and muscular disorders are prevalent among sport horses, with a fair prognosis for returning to exercise or previous performance levels. The field of equine medicine has witnessed rapid and fruitful development, resulting in a diverse range of therapeutic options for musculoskeletal problems. Staying abreast of these advancements can be challenging, prompting the need for a comprehensive review of commonly used and recent treatments. The aim is to compile current therapeutic options for managing these injuries, spanning from simple to complex physiotherapy techniques, conservative treatments including steroidal and non-steroidal anti-inflammatory drugs, hyaluronic acid, polysulfated glycosaminoglycans, pentosan polysulfate, and polyacrylamides, to promising regenerative therapies such as hemoderivatives and stem cell-based therapies. Each therapeutic modality is scrutinized for its benefits, limitations, and potential synergistic actions to facilitate their most effective application for the intended healing/regeneration of the injured tissue/organ and subsequent patient recovery. While stem cell-based therapies have emerged as particularly promising for equine musculoskeletal injuries, a multidisciplinary approach is underscored throughout the discussion, emphasizing the importance of considering various therapeutic modalities in tandem.

Safety assessment of equine allogeneic tenogenic primed mesenchymal stem cells in horses with naturally occurring tendon and ligament injuries

Background

Mesenchymal stem cells provide a valuable treatment option in orthopedic injuries in horses.

Objectives

The aim of this study was to evaluate the hematological, biochemical, immunological and immunomodulatory parameters following intralesional treatment with tenogenic primed equine allogeneic peripheral blood-derived mesenchymal stem cells (tpMSCs) in client-owned horses with naturally occurring superficial digital flexor tendon (SDFT) and suspensory ligament (SL) injuries.

Methods

The immunogenicity and immunomodulatory capacities of tpMSCs were assessed in a modified mixed lymphocyte reaction, including peripheral blood mononuclear cells (PBMCs) of 14 horses with SDFT and SL injuries after treatment with tpMSCs. In a second study, 18 horses with SDFT and SL injuries received either an intralesional injection with tpMSCs (n = 9) or no treatment (n = 9).

Results

The tpMSCs did not provoke a cellular immune response (p < 0.001) and were able to immunomodulate stimulated T lymphocytes (p < 0.001) in vitro. Therapeutic use of tpMSCs did not result in relevant hematologic or biochemical abnormalities.

Main limitations

Both studies had a small sample size. No statistical analyses were performed in the second study. Fibrinogen was only analyzed in a single horse prior to treatment.

Conclusion

Co-incubation of tpMSCs and PBMCs of horses that have been previously exposed to tpMSCs did not elicit a cellular immune response and tpMSCs were able to immunomodulate stimulated T lymphocytes. Intralesional treatment with tpMSCs did not provoke abnormal changes in hematological and biochemical parameters.

Regenerative Medicine Applied to Musculoskeletal Diseases in Equines: A Systematic Review

Musculoskeletal injuries in horses have a great economic impact, predominantly affecting tendons, ligaments, and cartilage, which have limited natural regeneration. Cell therapy, which uses mesenchymal stem cells due to their tissue differentiation properties and anti-inflammatory and immunoregulatory effects, aims to restore damaged tissue. In this manuscript, we performed a systematic review using the Parsifal tool, searching the PubMed and Web of Science databases for articles on regenerative medicine for equine musculoskeletal injuries. Our review covers 17 experimental clinical studies categorized by the therapeutic approach used: platelet-rich plasma, conditioned autologous serum, mesenchymal stem cells, and secretome. These therapies reduce healing time, promote regeneration of fibrocartilaginous tissue, improve cellular organization, and improve joint functionality and sustainability. In conclusion, regenerative therapies using platelet-rich plasma, conditioned autologous serum, equine mesenchymal stem cells, and the emerging field of the secretome represent a promising and highly effective approach for the treatment of joint pathologies in horses, implying a valuable advance in equine healthcare.

Assessment of Hydroxyproline Content in Rabbit Achilles Tendon Treated with Platelet Rich Fibrin (PRF)

Tendon is similar to rope and consists of strong, flexible, dense connective tissue. Tendon disorder healing is challenging as it is an avascular tissue. The repaired tissue appears scar-like, and its biomechanical properties never ultimately return to their pre-injury state. This study aimed to evaluate the effects of platelet-rich fibrin (PRF) on the hydroxyproline content of the Achilles tendon after injury. For this purpose, 24 adult rabbits weighing 1.5-2 kg were used in this study. The animals were divided into three groups of eight, including the advanced-PRF (A-PRF) group in which the tendon defect was treated with xenogeneic A-PRF, the leukocyte-PRF (L-PRF) group in which xenogeneic L-PRF was used for tendon defect treatment, and a control group which was treated with normal saline. Hydroxyproline concentration was measured 1 and 2 months after the operation. Clinically, lameness was improved in the A-PRF group, compared to the L-PRF and control groups at the end of the third week after the surgery. Hydroxyproline level was significantly increased in the A-PRF group (50.33±1.44), compared to the L-PRF (44.70±1.12) and control (35.97±1.05) groups 2 months after the surgery (P<0.05). Moreover, the L-PRF group showed an increase in hydroxyproline content, compared to the control at the same period. The results of the current study demonstrated that A-PRF could enhance the hydroxyproline content of rabbit Achilles tendon after injury. Xenogenic PRF can be used as an alternative biomaterial to accelerate and regenerate tendon tissue.

Autologous Platelet and Extracellular Vesicle-Rich Plasma as Therapeutic Fluid: A Review

The preparation of autologous platelet and extracellular vesicle-rich plasma (PVRP) has been explored in many medical fields with the aim to benefit from its healing potential. In parallel, efforts are being invested to understand the function and dynamics of PVRP that is complex in its composition and interactions. Some clinical evidence reveals beneficial effects of PVRP, while some report that there were no effects. To optimize the preparation methods, functions and mechanisms of PVRP, its constituents should be better understood. With the intention to promote further studies of autologous therapeutic PVRP, we performed a review on some topics regarding PVRP composition, harvesting, assessment and preservation, and also on clinical experience following PVRP application in humans and animals. Besides the acknowledged actions of platelets, leukocytes and different molecules, we focus on extracellular vesicles that were found abundant in PVRP.

Case report: Flexor carpi ulnaris tendinopathy in a lure-coursing dog treated with three platelet-rich plasma and platelet lysate injections

In the present case report a 7-year-old male Whippet competing in lure-coursing presented with third-degree recurrent lameness of the right forelimb, pain on palpation of the caudal aspect of the carpus and swelling of the forearm proximally to the accessory carpal bone. Clinical, radiographic, and ultrasonographic evaluation diagnosed a flexor carpi ulnaris (FCU) chronic tendinopathy unresponsive to previously attempted conservative treatments such as oral non-steroidal anti-inflammatory drugs (NSAIDs) administration along with padded palmar splint application and rest. The dog was subjected to one injection of autologous platelet-rich plasma (PRP) obtained using a double centrifugation tube method, followed by two platelet lysate (PL) injections. Treatment was administered at three-week intervals. The healing process was assessed through clinical and ultrasonographic imaging (US) on the day of the first injection (T0), and at week three (T1), six (T2), twelve (T3), fifty-two (T4), and one-hundred-and-four (T5). Fiber alignment score (FAS) and echogenicity score (ES) were developed by modifying a previously published US assessment scale. At T1, ES, and FAS improvement was detected, and at T2, further improvements in ES and FAS were observed. Ultrasonographic results were clinically consistent with the improvement in lameness: lameness grade 3/4 was detected at T0 and grade 2/4 at T1. A lameness grade of 1/4 was detected at T2, and grade 0/4 was observed at T3, T4, and T5. Moreover, at T5, the dog returned to competition, and no history of re-injury was reported. Our results suggest that the treatment of FCU tendinopathy in lure-coursing dogs with a combination of consecutive injections of autologous PRP and PL could be feasible. Additionally, no adverse reactions were observed.

Ultrasound-Guided Injection of Autologous Platelet-Rich Plasma for Refractory Lateral Epicondylitis of Humerus: Case Series

Refractory lateral epicondylitis (RLE) is a tendinopathy of the elbow with less effective conservation treatment. Platelet-rich plasma (PRP) is a new treatment option for RLE because of its repair-promoting effect on tissues. Although evidence demonstrates the efficacy of PRP in treating tendinopathies, the therapeutic utility of ultrasound-guided PRP injection for RLE is unknown. Here, we report two cases of RLE treated with PRP. The first patient was a 78-year-old man who received an unknown dose of local glucocorticoid injection at the local community clinic in June 2016. His pain recurred after exertion. The second patient was a 54-year-old woman who received a glucocorticoid injection (0.5 mL of compound betamethasone and 1.5 mL of 0.9% normal saline) in October 2020. Her pain could not be relieved. A physician diagnosed patients with RLE based on their medical history, symptoms, and clinical signs. The doctor injected PRP (the first patient in November 2020, the second in March 2021) under ultrasound guidance into the patient's attachment point of the extensor tendon at the lateral humeral epicondyle. The doctor evaluated the effectiveness of the treatment by ultrasonography, visual analogue scale, and the patient-rated tennis elbow evaluation. After four weeks of treatment, the pain was relieved, and functions continued to improve in the following three months. Moreover, the ultrasonography showed that the damaged tendons were repaired. Together, we demonstrate that ultrasound-guided PRP injection could considerably relieve pain, improve elbow joint functions in patients with RLE, and provide visible evidence that PRP repairs tendon damage.

Outcome following local injection of a liquid amnion allograft for treatment of equine tendonitis or desmitis – 100 cases

Background

Tendon and ligament injuries are significant causes of loss of use and early retirement in performance horses. Amniotic fluid and tissue are excellent sources of growth factors and cytokines important in tendon and ligament healing. Thus, an equine-origin liquid amnion allograft (ELAA) may be beneficial in the treatment of equine tendonitis and desmitis. Objectives of this study were to report the outcome achieved (i.e. ability to return to work) for horses diagnosed with tendonitis or desmitis lesions treated with local injection of ELAA and to compare these outcomes to those reported for other regenerative medicine modalities.

Methods

A prospective, multi-center, non-blinded clinical trial was conducted. Equine veterinarians at 14 sites were selected to participate in the data collection for the trial. Criterion for inclusion was a horse presenting with lameness which was attributed to tendonitis or desmitis by diagnostic anesthesia and/or imaging. These horses were subsequently treated by local injection of the lesion with ELAA by the attending veterinarian. Standardized questionnaires describing each horse’s signalment, discipline, ability to return to work, and any adverse events were completed and submitted by the attending veterinarian following a minimum of six months of follow-up. The current literature was reviewed to identify clinical studies reporting outcomes of equine tendonitis/desmitis lesions treated with other regenerative therapies. Contingency table analyses were performed comparing outcomes.

Results

Questionnaires for 100 horses with 128 tendonitis and desmitis lesions met the inclusion criteria. Of these, 72 horses with 94 lesions returned to or exceeded their original level of work, 10 horses with 13 lesions returned to work but could not perform to previous standards, and 18 horses with 20 lesions did not return to work as a result of the injury. No differences were observed when outcome of horses treated with ELAA were compared to those of similar studies using other regenerative therapies.

Conclusions

Treatment of tendonitis and desmitis lesions by local injection of ELAA resulted in similar outcomes for horses returning to previous level of performance as other regenerative modalities such as mesenchymal stem cells, platelet-rich plasma, and autologous conditioned serum; however, blinded placebo-controlled studies are indicated.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03480-5.

Intralesional bone marrow and superior check desmotomy is superior to conservative treatment of equine superficial digital flexor tendonitis

BACKGROUND

Superficial digital flexor tendon (SDFT) injury is common in racehorses and a significant cause of lost training days and wastage in the industry.

OBJECTIVES

To compare the post-injury performance of Thoroughbred and Standardbred racehorses diagnosed with SDFT tendonitis treated with intralesional bone marrow and superior check desmotomy or managed conservatively and further to compare this performance with that of uninjured racehorses.

STUDY DESIGN

Retrospective and case-controlled.

METHODS

Medical and race records of racehorses treated surgically or managed conservatively for SDFT tendonitis were collated. Signalment, lesion severity and treatment were identified and performance post-injury compared. Performance of the treatment groups was further assessed by comparison with uninjured racehorses matched for age, sex, number of starts pre-injury and randomly selected from the cases' last races.

RESULTS

The study population comprised 114 racehorses divided into surgical (39/114), conservative (38/114) and control groups (37/114). Horses that had surgery were more likely to return to racing than those managed conservatively (OR 4.7 95% CI [1.6-14.3], P = .006). Standardbreds were more likely to return to race compared with Thoroughbreds (OR 4.0 95% CI [1.2-13.3], P = .03). There was no statistically significant difference in the average number of placings, average number of wins and post-injury earnings between the surgically treated and conservatively managed groups (P = .9, P = .9 and P = .7, respectively). The average number of lifetime starts post-injury/post-selection between surgery, conservative and control groups were not statistically significantly different (P = .2). Surgically treated horses had a statistically significantly shorter time to start post-injury compared with the conservative group (P = .04).

MAIN LIMITATIONS

The retrospective nature of the study precludes an actual fit as a nonrandomised clinical trial and the nonrandomised nature of the allocation of the treatment groups is biased.

CONCLUSIONS

Surgical intervention of superficial digital flexor tendonitis in racehorses suffering flexor tendon injury showed a higher likelihood of return to racing than conservative treatment.

Applicability of ARFI elastography in detecting elasticity changes of the equine superficial digital flexor tendon with induced injury

The objectives of this prospective, experimental study were to describe changes in the stiffness of the equine superficial digital flexor tendon (SDFT) after induced injury, deep digital flexor tendon (DDFT), accessory ligament (AL-DDFT), and suspensory ligament (SL) during 90 days of healing using acoustic radiation force impulse (ARFI) elastography. Eight healthy horses were selected. Preinjury B mode and ARFI evaluations were performed bilaterally in the palmar metacarpal region. Injury was induced only on the left forelimb (G2) by a single injection of collagenase in SDFT, 15 cm distal to the accessory carpal bone. The right forelimb was used as a control (G1). Evaluations were performed at eight timepoints: one before injury (T0) and seven (T1-T7) after injury (3, 15, 30, 40, 60, 75, and 90 days post-induction). Tendinopathies were visualized as hypoechoic areas with loss of parallel tendon fiber pattern. Injured SDFTs presented mainly cool colors (soft) from T1 to T3, and from T4, there was an increase in warm colors (hard), close to the appearance of tendons of G1. In the first four timepoints, there was a decrease in stiffness compared to G1 (P < 0.001). On T1 and T2, a cutoff value <6.21 m/s to determine tendinopathy of the SDFT was established (75.8% sensitivity and 92.03% specificity). Stiffness changes in the DDFT, AL-DDFT, and SL of injured limbs occurred at different timepoints. Tendinopathy significantly altered the stiffness of the injured tendon and the adjacent tissues. ARFI made it possible to detect these changes, helping to monitor the reparation of this injury.

Platelet-Rich Plasma as an Orthobiologic: Clinically Relevant Considerations

Platelet-rich plasma (PRP) is an autologous blood-derived product processed to concentrate platelets and the associated growth factors. PRP has been shown to be relatively well-tolerated and safe to use for a number of conditions in humans, equines, and canines. There are multiple commercial systems that have been validated for canine use. These systems use a variety of methodologies to produce a PRP product. However, PRP products have been shown to differ greatly between systems. Further study is needed to fully elucidate optimal component concentrations for various indications.

Evaluation of a Standardized Protocol for Plasma Rich in Growth Factors Obtention in Cats: A Prospective Study

Introduction

Platelet-rich plasma (PRP) is an autologous plasma with platelet (PLT) concentration above that of whole blood (WB). PLTs contain growth factors (GFs) that promote tissular repair.

Objectives

To determine and compare the concentrations of PLT, red blood cells (RBC) and white blood cells (WBC) between WB samples, PRP and platelet poor plasma (PPP) samples; and to analyze the concentrations of platelet-derived growth factor BB (PDGF-BB) and transforming growth factor β1 (TGF-β1) in the PRP and PPP of healthy adult cats using a standardized protocol with PRGF®-Endoret® characteristics.

Material and Methods

WB was collected from 30 cats. PRP was obtained following three centrifugation protocols using PRGF®-Endoret® technology: 255, 260, and 265 g for 10 min each. The cellular components, RBC, WBC, PLT, and the concentrations of PDGF-BB and TGF-β1 in the PRP and PPP fractions were determined for each protocol.

Results

PLTs in the PRP fraction were statistically higher than WB, with no statistical differences between PPP and WB. In PRP fraction, PLT concentration was increased 1.4 times on average at 255 g; 1.3 times at 260 g and, 1.5 times at 265 g without statistical differences among them. The mean platelet volume (MPV) was significantly higher in WB compared to PRP and PPP fractions without significant differences between protocols. Compared to WB, the number of RBCs and WBCs was reduced by 99% and by more than 95% in PRP and PPP respectively, without significant differences between protocols. PDGF-BB concentrations were statistically higher in PRP than in PPP fractions, however, TGF-ß1 concentrations did not vary between fractions at 260 g. Comparing the three protocols within PRP and PPP fractions, no differences in PDGF-BB and TGF-ß1 concentrations were observed.

Clinical Relevance

The study shows scientific evidence regarding the obtention of PRP in cats using the PRGF®-Endoret® technology for the quantification of PDGF-BB and TGF-ß1. At 265 g for 10 min, PLT concentration was increased 1.5 times with unnoticeable erythrocytes and leukocytes in the samples. These results clearly show that the PRGF®-Endoret® methodology is suitable to obtain PRP in cats. Further studies are needed to determine the clinical efficacy of the obtained PGRF in the treatment of different pathologies in cats.

Current use of biologic therapies for musculoskeletal disease: A survey of board-certified equine specialists

Objective

To evaluate the use of mesenchymal stem cells (MSCs), autologous conditioned serum (ACS), platelet‐rich plasma (PRP), and autologous protein solution (APS) for the treatment of equine musculoskeletal disease by diplomates of the American College of Veterinary Surgery (ACVS), and American College of Veterinary Sports Medicine and Rehabilitation (ACVSMR).

Study design

Cross‐sectional study.

Sample population

Diplomates (n = 423).

Methods

An email link was sent to ACVS and ACVMR diplomates. A survey contained 59 questions regarding demographics, as well as indications, frequency, adverse effects, and limitations of use. Responses were analyzed using Fisher's exact test.

Results

One hundred and fifty four surveys were analyzed. Years in practice and type of practice were not associated with biologic therapy use. PRP was the most used therapy (120/137; 87.5%). PRP and MSCs were most often administered intralesionally while ACS and APS were most often administered intra‐articularly. ACS (50/104; 48.1%) treatment was repeated commonly within 2 weeks of initial injection. MSCs (39/90; 43.3%) and PRP (38/100; 38%) were commonly repeated 1‐2 months after initial injection and APS was typically repeated >4 months after initial injection (21/53; 39.6%). Local inflammation and expense were the most common adverse effect and limitation of use.

Conclusion

Diplomates most commonly utilized PRP and MSC intralesionally for soft‐tissue injuries, and ACS and ACP intra‐articularly for joint injury. Protocols for repeated administration varied widely. Local inflammation was a clinical concern with the use of biologics.

Clinical significance

Biologic therapies are used commonly by ACVS and ACVSMR diplomates for soft tissue and joint disease.

Case Report: Repeated Intralesional Injections of Autologous Mesenchymal Stem Cells Combined With Platelet-Rich Plasma for Superficial Digital Flexor Tendon Healing in a Show Jumping Horse

In the present case report a show jumping 10-year-old Sella Italiano gelding, presented with severe lameness, swelling and pain at palpation of the mid-metacarpal region of the left forelimb. Clinical and ultrasound examination diagnosed a chronic tendonitis of the central region of the superficial digital flexor tendon (SDFT). The lesion was a reoccurrence since it developed from a previously healed injury. The horse had to stop competing and was unresponsive to gold-standard treatments as Non-steroidal anti-inflammatory drugs (NSAIDs) and conservative management after 6 months of therapy. The animal was subjected to repeated intralesional injections of autologous adipose-derived mesenchymal stem cells (AD-MSCs) combined with autologous platelet-rich plasma (PRP). The combined treatment was administered twice in a 1-month interval. The healing process was assessed through clinical examination, ultrasound imaging and quantification of oxidative stress products and inflammatory mediators in blood plasma. After 2 weeks from first injection, a reduction of concentration of oxidative-derived products was observed, together with an increase of anti-inflammatory cytokines and pro-mitotic growth factors. These results were reflected clinically as the horse showed a reduction of lameness along with swelling and pain after 4 weeks. At the 1-year follow-up, the horse showed no signs of lameness and swelling. The ultrasonographic examination highlighted a compact fiber alignment with a normal echogenic tendon as observed in the sound contralateral limb. Moreover, the horse went back to the previous level of competition. Our results suggest the positive effects of a repeated intralesional injection of AD-MSCs and PRP for the treatment of a chronic tendonitis with long-term effects and an improvement for both equine quality of life and athletic performance.

Using Short Term of High Power Laser Therapy in Horse's Tendon Injuries

High-power laser therapy has been used as a treatment to cure sports injuries; however, there are no controlled standardized studies on its efficacy. Moreover, high-power laser therapy has been applied for the sport horses field. This study aimed to investigate whether high-power laser therapy can cure tendon disorders and reduce the pain in tendon lesions in injured horses and also to examine the effect of laser therapy on injured horses. This retroactive experiential clinical research was performed on50 racing horses between 5 and 15 years old. They were diagnosed with neither superficial digital flexor tendon nor deep digital flexor tendon injuries of the suspensory ligament on either hind or front limbs and were medicated with a high-power laser. The high-power laser was used with a maximum output power of 15000 MW and therapeutic effects were assessed using lameness graded and ultrasound the day after laser therapy (week 2) and 4weeks later (week 6). Results showed that laser treatment was effective and uncomplicated in all injured horses. In addition, significant improvement was observed in ultrasound scores and lameness following high-power laser treatment. There was a progressive correlation between the improvement of lameness and the following parameters; returning tendon survival, normality of tendon tissue and functions in rest, trot, or competition after treatment. According to the results, laser treatment is a good way to eliminate the complications caused by tendon damage.

Equine flexor tendon imaging part 1: Recent developments in ultrasonography, with focus on the superficial digital flexor tendon

Flexor tendon injuries are a major cause of lameness in performance horses and have considerable impact on equine welfare and the wider horse industry. Ageing and repetitive strain frequently cause varying degrees of tendon micro-damage prior to the recognition of clinical tendinopathy. Whilst B-mode ultrasonography is most commonly utilised for detection and monitoring of tendon lesions at the metacarpal/metatarsal level, the emphasis of recent research has focused on the identification of subclinical tendon damage in order to prevent further tendon injury and improve outcomes. The introduction of elastography, acoustoelastography and ultrasound tissue characterisation in the field of equine orthopaedics shows promising results and might find wider use in equine practice as clinical development continues. Based on the substantial number of research studies on tendon imaging published over the past decade this literature review aims to examine the currently used ultrasonographic imaging techniques and their limitations, and to introduce and critically appraise new modalities that could potentially change the clinical approach to equine flexor tendon imaging.

Use of autologous products for the treatment of joint and soft tissue disease in horses: A systematic review

BACKGROUND

Soft tissue injuries and joint disease are the predominate causes of lameness in the equine athlete and these pathologies carry a guarded prognosis for a return to previous performance. Recently the use of autologous products has become more widespread as a treatment in equine sports medicine. However, the efficacy of these products is yet to be fully established.

OBJECTIVE

To evaluate the current published evidence base regarding the efficacy of autologous products in soft tissue injuries and joint disease.

METHODS

A systematic review of English articles using MEDLINE, EMBASE and Web of Science databases from 1980 to 2017. The search strategy identified 1594 papers for review.

RESULTS

Fifty-eight papers were included in this review, 28 of which were randomised controlled trials. Significant benefit was reported under several parameters, most notably in the use of autologous chondrocytes in artificially induced cartilage defects on histology. One paper documented a significant clinical response under lameness examination.

CONCLUSION

The current literature shows that the treatment of soft tissue injury and cartilage disease with autologous products is safe and that the use of some products can give significant benefit on some outcome measures. True clinical significance is yet to be demonstrated with any product.

Effectiveness of Platelet-Rich Plasma and Bone Marrow Aspirate Concentrate as Treatments for Chronic Hindlimb Proximal Suspensory Desmopathy

This retrospective study aimed to evaluate the clinical effect of bone marrow aspirate concentrate (BMAC) and leukocyte rich PRP (LR-PRP) compared to horses undergoing controlled exercise alone in horses with >3 months proximal suspensory desmopathy in hindlimbs (HPSD). Nighty-three horses were divided into three groups according to the treatment: a control (n = 22), LR-PRP (n = 46), and BMAC (n = 25) group. Lameness and ultrasound scores were recorded before treatment (T0) and at 6 months (T1) post-treatment. Records horses considered sound at evaluation and level of performance were additionally registered at 12 months (T2) and 18 months (T3) after treatment. The BMAC cytology profiles from 22 horses were also analysed and compared to clinical outcomes. The results at T1 showed that 9% (2/22) of the horses in the control group were sound compared to 59% (25/46) and 84% (21/25) in the LR-PRP and BMAC groups, respectively. Additionally, ultrasound scores at T1 in the BMAC and LR-PRP groups were improved in comparison with the control group (p = 0.02). At T2, 68% of the horses in the BMAC group and 39% of the horses in the LR-PRP group had returned to the previous performance level. At T3, a significantly higher percentage of horses in the LR-PRP (43%) and BMAC (72%) group were sound when compared to the control (4.6%) group (p = 0.02). Similarly, at T3, significantly more horses of the BMAC (16/25) and of the LR-PRP (15/46) group had returned to the previous or a higher performance level compared to the control (1/22) group (p = 0.01). No correlation was found between long-term clinical outcome and cytology profiles in the BMAC group. In conclusion, long-term outcomes of treatment with LR-PRP or BMAC are significantly better than conventional treatment of the hindlimb chronic PSD in horses. Additionally, BMAC yielded better lameness scores than LR-PRP at short- and long-term follow-up.

A Critical Overview of the Use of Platelet-Rich Plasma in Equine Medicine Over the Last Decade

In the 1990s, the role of platelets in inflammation and tissue healing was finally recognized. Since then, the clinical use of platelet-derived products (hemocomponents), such as, platelet-rich plasma (PRP), markedly increased. The promise of a more economical option of a disease-modifying treatment led to the intensive and continuous research of PRP products and to its widespread clinical use. A number of protocols and commercial kits have been developed with the intention of creating a more practical and reliable option for clinical use in equine patients. Still, the direct comparison between studies is particularly challenging due to the lack of standardization on the preparation methods and product composition. The incomplete reports on PRP cellular concentration and the poorly designed in vivo studies are additional matters that contest the clinical efficiency of this biomaterial. To overcome such challenges, several in vitro and in vivo studies have been proposed. Specifically, experiments have greatly focused in protocol optimization and its effect in different tissues. Additionally, in vivo studies have proposed different biological products envisioning the upgrade of the anti-inflammatory cytokines trusting to increase its anti-inflammatory effect. The individual variability and health status of the animal, type of tissue and condition treated, and protocol implemented are known to influence on the product's cell and cytokine composition. Such variability is a main clinical concern once it can potentially influence on PRP's therapeutic effects. Thus, lack of qualitative and quantitative evidence-based data supporting PRP's clinical use persists, despite of the numerous studies intended to accomplish this purpose. This narrative review aims to critically evaluate the main research published in the past decade and how it can potentially impact the clinical use of PRP.

The Use of Platelet-Rich Plasma for Treatment of Tenodesmic Lesions in Horses: A Systematic Review and Meta-Analysis of Clinical and Experimental Data

The use of platelet-rich plasma (PRP) to enhance tenodesmic lesion healing has been questioned over the years. The aim of this study was to evaluate current literature to establish the effectiveness of PRP for treating tenodesmic lesions through a systematic review, in accordance with the PRISMA guidelines, and a meta-analysis. Studies comparing PRP with placebo or other treatments for horses with tenodesmic injuries or evaluated PRP effect on tendon and ligament explants were included. Outcomes were clinical, ultrasound, histologic, molecular evaluation, and adverse effects. Two authors independently extracted data and assessed each study's risk of bias. Treatment effects were evaluated using risk ratios for dichotomous data, together with 95% CI. Data were pooled using the random-effects model. The quality of the evidence for each outcome was assessed using GRADE criteria. Twenty-four trials met inclusion criteria for systematic review, while fifteen studies were included in the meta-analysis. Results showed no significant differences in the outcomes between PRP and control groups. Finally, there is no definitive evidence that PRP enhances tendons and ligaments healing. Therefore, there is a need for more controlled trials to draw a firmer conclusion about the efficacy of PRP as a treatment for tenodesmic lesions in the horse.

Regenerative Medicine for Equine Musculoskeletal Diseases

Simple Summary

Lameness due to musculoskeletal disease is the most common diagnosis in equine veterinary practice. Many of these orthopaedic disorders are chronic problems, for which no clinically satisfactory treatment exists. Thus, high hopes are pinned on regenerative medicine, which aims to replace or regenerate cells, tissues, or organs to restore or establish normal function. Some regenerative medicine therapies have already made their way into equine clinical practice mainly to treat tendon injures, tendinopathies, cartilage injuries and degenerative joint disorders with promising but diverse results. This review summarises the current knowledge of commonly used regenerative medicine treatments and critically discusses their use.

Abstract

Musculoskeletal injuries and chronic degenerative diseases commonly affect both athletic and sedentary horses and can entail the end of their athletic careers. The ensuing repair processes frequently do not yield fully functional regeneration of the injured tissues but biomechanically inferior scar or replacement tissue, causing high reinjury rates, degenerative disease progression and chronic morbidity. Regenerative medicine is an emerging, rapidly evolving branch of translational medicine that aims to replace or regenerate cells, tissues, or organs to restore or establish normal function. It includes tissue engineering but also cell-based and cell-free stimulation of endogenous self-repair mechanisms. Some regenerative medicine therapies have made their way into equine clinical practice mainly to treat tendon injures, tendinopathies, cartilage injuries and degenerative joint disorders with promising results. However, the qualitative and quantitative spatiotemporal requirements for specific bioactive factors to trigger tissue regeneration in the injury response are still unknown, and consequently, therapeutic approaches and treatment results are diverse. To exploit the full potential of this burgeoning field of medicine, further research will be required and is ongoing. This review summarises the current knowledge of commonly used regenerative medicine treatments in equine patients and critically discusses their use.

Platelet and Leukocyte Concentration in Equine Autologous Conditioned Plasma Are Inversely Distributed by Layer and Are Not Affected by Centrifugation Rate

Background: Platelet rich plasma (PRP) is used extensively in equine regenerative medicine. Differences in preparation protocols give rise to significant variability in the cellular composition of PRP making it very difficult to establish a standard of care in the field. This study aimed to optimize the preparation protocol for leukocyte-reduced PRP (P-PRP).

Methods: Blood (100 mL) was collected from horses (n = 5) and divided into 2 purple top EDTA tubes and 6 (15 mL) double syringes^a with a final concentration of 10% acid citrate dextrose anticoagulant. Six double syringes^a were collected from each horse; PRP samples were prepared in duplicate and centrifuged at 1,100 rpm (188 × g), 1,300 rpm (263 × g), or 1,500 rpm (350 × g). Duplicates were subjected to +/– braking at the end of centrifugation. The total volume of PRP generated was measured and divided into thirds. Each third (top, middle, and bottom) were drawn off separately using the inner (6 mL syringe) and placed in purple top EDTA tubes. Automated complete blood counts were performed on all peripheral whole blood and PRP samples.

Results: The concentration of leukocytes was higher in the bottom layer of PRP compared to the top and middle layers (p < 0.0001). The concentration of platelets was slightly lower in the bottom layer of PRP than the middle layer (p = 0.02). Centrifugation braking increased the leukocyte concentration in the top (p = 0.03) and middle layers of PRP (p = 0.001). Centrifugation rate had no effect on the cellular composition of PRP (p = 0.1–0.6).

Conclusions: Because layer of plasma affected both platelet and leukocyte concentrations in PRP, the most important modification for the current single spin, double syringe, plasma based PRP preparation protocols is to exclude the bottom 1/3 layer of PRP.

Microvesicles isolated from 5-azacytidine-and-resveratrol-treated mesenchymal stem cells for the treatment of suspensory ligament injury in horse-a case report

BACKGROUND

In athlete horses, suspensory ligament (SL) injuries are the most common cause of lameness. Healing of SL injury is still problematic, and even proper rehabilitation and pharmacological therapy do not guarantee returning to the initial performance level. In our previous studies, we have shown that a combination of 5-azacytidine (AZA) and resveratrol (RES) exerts beneficial, rejuvenating effects on metabolic syndrome derived adipose-derived stem cells (ASCs). Thus, in the presented research, we investigate whether not only rejuvenated ASC but also microvesicles (MVsAZA/RES) secreted by them possess enhanced regenerative properties in SL injury.

METHODS

In the presented study, a 6-year-old Dutch Warmblood gelding, working in jumping, was diagnosed with SL injury using ultrasonography, Doppler, real-time elastography and thermography. As a therapeutic strategy, the affected animal was treated with extracellular microvesicles derived from ASC treated with the combination of 5-azacytydine (AZA) and resveratrol (RES) (MVsAZA/RES). RESULTS: First, anti-apoptotic effects of MVsAZA/RES were tested in co-culture with metabolic syndrome derived ASC. The proliferation of cells and expression of pro-apoptotic genes were investigated. Then, MVsAZA/RES were injected directly into the injured SL of the Dutch Warmblood gelding. In vitro assays revealed that MVsAZA/RES enhance the proliferation of ASC and exert an anti-apoptotic effect. In the affected horse, the application of MVsAZA/RES resulted in increased lesion filling and improvement of angiogenesis and elasticity in injured tissue.

CONCLUSIONS

As MVsAZA/RES mimic several of the biological actions exerted by ASC, they have become an alternative for stem cell-based therapies and can be effectively applied for the treatment of SL injury in horses.

Platelet-Rich Products and Their Application to Osteoarthritis

Autologous platelet-rich plasma (PRP) is a biological preparation made from the patient's own plasma that contains a platelet concentration above the whole blood baseline. Owing to the release of growth factors and other cytokines after degranulation, platelets have a central role in inflammation and in different stages of the healing process. For this reason, PRP-derived products have been used to enhance healing of musculoskeletal injuries and modulate progression of inflammatory processes, including osteoarthritis (OA). Osteoarthritis is one of the main causes of musculoskeletal disabilities in horses, and currently, there is no effective treatment for this disease. Treatments that focus on the modulation of inflammation and disease progression offer new hope for OA. Platelet-rich plasma provides a more practical and accessible option of therapy compared to other forms of biological treatment (i.e., stem cell therapies) and is believed to induce the production of functional matrix. However, several factors related to PRP production, including methods of preparation and application, and intraindividual variability, lead to an inconsistent product, precluding reliable conclusions about its efficacy for clinical use. The aim of this study was to review the benefits related to the clinical use of PRP in OA as well as factors that influence its use, the limitations of this treatment, and future directions of PRP research and therapy.

Suppression of PDGF induces neuronal apoptosis after neonatal cerebral hypoxia and ischemia by inhibiting P-PI3K and P-AKT signaling pathways

Neonatal hypoxic-ischemic encephalopathy (HIE) always results in severe neurologic dysfunction, nevertheless effective treatments are limited and the underlying mechanism also remains unclear. In this study, we firstly established the neonatal HIE model in the postnatal day 7 SD rats, Zea-Longa score and TTC staining were employed to assess the neurological behavior and infarct volume of the brain after cerebral hypoxia-ischemia (HI). Afterwards, protein chip was adopted to detect the differential proteins in the right cortex, hippocampus and lung, ultimately, PDGF was noticed. Then, immunohistochemistry, immunofluorescence double staining of NeuN/PDGF, and western blot were used to validate the expression level of PDGF in the cortex and hippocampus at 6 hours (h), 12 h and 24 h after HI. To determine the role of PDGF, the primary cortical neurons were prepared and performed PDGF shRNA administration. The results showed that HIE induced a severe behavioral dysfunction and brain infarction in neonatal rats, and the expression of PDGF in right cortex and hippocampus was remarkably increased after HI. Whereas, suppressing PDGF resulted in a significant loss of neurons and inhibition of neurite growth. Moreover, the protein level of P-PI3K and P-AKT signaling pathways were largely decreased following PDGF-shRNA application in the cortical neurons. In conclusion, PDGF suppression aggravated neuronal dysfunction, and the underlying mechanism is associated with inhibiting the phosphorylation of P-PI3K and P-AKT. Together, PDGF regulating PI3K and AKT may be an important panel in HIE events and therefore may provide possible strategy for the treatment of HIE in future clinic trail.

Effect of L-PRP treatment on wound healing after surgical skin incision in an experimental animal model

AIM OF THE STUDY

The aim of the study was to evaluate the effect of leukocyte- and platelet-rich plasma (L-PRP) treatment on a noncomplicated would healing after surgical skin incision in an experimental animal model.

MATERIALS AND METHODS

The blood from 64 male Wistar rats was used to prepare L-PRP before a transverse dorsal incision was made and consecutively closed. At the same time after the surgery was completed, autologous L-PRP in the rats from the L-PRP group (n = 32) and NaCl in the control group (n = 32) were injected subcutaneously into the wound. The examination included clinical observations, laboratory examination, and examination of biopsy specimens taken from sacrificed animals on the second, third, fourth, and sixth days after the surgery (histopathological examination, immunochemistry, molecular examination).

RESULTS

In all cases, no healing process complications were noted. The intergroup comparison revealed no statistically significant differences in terms of histopathological, immunohistochemical, and molecular examinations results. In the intragroup analysis, statistically significant differences were observed within each group between periods of observations in terms of immunohistochemical and molecular examinations results.

CONCLUSIONS

L-PRP treatment does not significantly accelerate a noncomplicated wound healing after surgical skin incision in an experimental animal model.

Equine suspensory ligament and tendon explants cultured with platelet-rich gel supernatants release different anti-inflammatory and anabolic mediators

The aim of this study was to evaluate the release of pro- and anti-inflammatory as well as anabolic mediators stimulated by a leukocyte-reduced platelet-rich gel supernatant (Lr-PRGS) and a leukocyte-reduced plasma supernatant (Lr-PL) at two concentrations (25 and 50%) on normal equine suspensory ligament explants (SLEs) and tendon explants (TEs). SLEs and TEs from six horses were independently incubated for 48 h with Lr-PRGS and Lr-PL at concentrations of 25 and 50%, respectively. Samples were collected from the incubated tissues at 1 h and 48 h, which were employed for ELISA determination of interleukin 1 beta (IL-1β), tumor necrosis factor alpha (TNF-α),  IL-4, IL-1 receptor antagonist (IL-1ra), platelet-derived growth factor isoform BB (PDGF-BB), transforming growth factor beta-1 (TGF-β₁, and hyaluronic acid (HA). Overall, 50% Lr-PRGS induced significantly less IL-1β release than the other hemoderivatives in both tissues. At 48 h, both Lr-PRGS and 25% Lr-PL induced significantly higher TNF-α concentrations in SLEs when compared to TEs, whereas both Lr-PRGS concentrations induced significantly higher IL-4 concentrations in SLEs in comparison to TEs. IL-1ra release was not different between tissues. However, this cytokine was significantly higher in tissue explants cultured with both Lr-PRGS concentrations. HA concentration was lower in tissue explants cultured with all hemoderivatives at two concentrations when compared to the control group. The positive effects observed for ligaments and tendons treated with Lr-PRGS may be mediated by the inhibition of IL-1β release of and increased release of IL-4 and IL-1ra. Furthermore, PDGF-BB could be a polypeptide responsible for mediating the release of anti-inflammatory cytokines in SLEs and TEs incubated with Lr-PRGS.

Randomized controlled trial demonstrates the benefit of RGTA® based matrix therapy to treat tendinopathies in racing horses

A randomized controlled trial was performed on racing horses, to evaluate the efficacy of a new class of therapeutic agents in regenerative medicine—ReGeneraTing Agents^® (RGTA^®), to treat tendinopathies. Preliminary uncontrolled studies on tendon healing in racing horses with RGTA^® (OTR4131)—Equitend^® showed encouraging results, justifying performing a randomized, controlled, multicenter study with a two-year racing performance follow up. The objective of this study was to evaluate the effect of Equitend^® versus placebo on acute superficial digital flexor tendonitis in racing French Standardbred Trotters (ST). Twenty-two ST were randomly and blindly assigned to receive with a ratio of 2 to 1, a single Equitend^® (n = 14) or placebo (n = 8) intralesional injection under ultrasonographic guidance. Horses were evaluated over 4 months, by clinical and ultrasonographic evaluations (day 0, months 1, 2, 4), and their racing performances followed up over the 2 years after treatment. During the first month of treatment, a significant decrease in the cross-sectional area (CSA) was found in the Equitend^® group (p = 0.04). After 4 months, the number of Equitend^® treated horses with an improved CSA was significantly higher than the placebo-treated horses (p = 0.03571). The Equitend^® group returned to their pre-injury performance level, racing in, and winning, significantly more races than the placebo group (p = 0.01399 and 0.0421, respectively). Furthermore, recurrence was significantly higher in the placebo group than in the Equitend^® group (71.4% vs 16.6%, p = 0.02442). In conclusion, we measured a significant, short-term, reduction effect on CSA and demonstrated a long-term beneficial effect of intralesional injection of Equitend^® for the treatment of superficial digital flexor tendonitis on racing ST, racing 2. 3 times more often than placebo, with 3.3 times fewer recurrences maintaining pre-injury performance level. This study may open the way for the development of a human treatment of tendonitis.

Effects of bone marrow aspirate concentrate and platelet-rich plasma on patients with partial tear of the rotator cuff tendon

Background

We compared the clinical course of rotator cuff tears between rotator cuff exercise and bone marrow aspirate concentration (BMAC)-platelet rich plasma (PRP) injection to identify the therapeutic effects of BMAC-PRP on partial tear of the rotator cuff tendon.

Methods

Twenty-four patients with partial tear of the rotator cuff tendon participated in this study. Twelve patients underwent extraction of BMACs and PRP and received the injection of BMAC-PRP at the tear site under ultrasound guidance. Twelve patients in the control group were asked to perform the rotator cuff exercise for 3 months. Visual analog scale (VAS) and manual muscle test (MMT) scores of the supraspinatus muscle were measured, and the American Shoulder and Elbow Surgeons (ASES) score was recorded before, 3 weeks, and 3 months after injection. Tear size was measured by the greatest longitudinal tear length.

Results

The change in the VAS differed between groups at 3 months (P = 0.039) but not at 3 weeks (P = 0.147). The ASES scores in the BMAC-PRP group changed from 39.4 ± 13.0 to 54.5 ± 11.5 at 3 weeks and 74.1 ± 8.5 at 3 months while those in the control group changed from 45.9 ± 12.4 to 56.3 ± 12.3 at 3 weeks (P = 0.712) and 62.2 ± 12.2 at 3 months (P = 0.011). The tear size decreased at 3 weeks or 3 months after the BMAC-PRP injection but was not significantly different from that in the control group.

Conclusions

BMAC-PRP improved pain and shoulder function in patients with partial tear of the rotator cuff tendon.

Trial registration

The patients were registered in the institutional board registry of Samsung Medical Center (registry number 2014-07-173).

Electronic supplementary material

The online version of this article (10.1186/s13018-017-0693-x) contains supplementary material, which is available to authorized users.

Ultrasonographic scoring system for superficial digital flexor tendon injuries in horses: intra- and inter-rater variability

Superficial digital flexor tendon (SDFT) tendinopathy is an important musculoskeletal problem in horses. The study objective was to validate an ultrasonographic scoring system for SDFT injuries. Ultrasonographic images from 14 Thoroughbred racehorses with SDFT lesions (seven core; seven diffuse) and two controls were blindly assessed by five clinicians on two occasions. Ultrasonographic parameters evaluated were: type and extent of the injury, location, echogenicity, cross-sectional area and longitudinal fibre pattern of the maximal injury zone (MIZ). Inter-rater variability and intra-rater reliability were assessed using Kendall's coefficient of concordance (KC) and Lin's concordance correlation coefficient (LC), respectively. Type of injury (core vs. diffuse) had perfect inter/intra-rater agreement. Cases with core lesions had very strong inter-rater agreement (KC ≥0.74, P<0.001) and intra-rater reliability (LC ≥0.73) for all parameters apart from echogenicity. Cases with diffuse lesions had strong inter-rater agreement (KC ≥0.62) for all parameters, but weak agreement for echogenicity (KC=0.22); intra-rater reliability was excellent for MIZ location and fibre pattern (LC ≥0.82), and moderate (LC ≥0.58) for cross-sectional area and number of zones affected. This scoring system was reliable and repeatable for all parameters, except for echogenicity. A validated scoring system will facilitate reliable recording of SDFT injuries and inter-study meta-analyses.

Extracorporeal Shockwave Therapy Increases Growth Factor Release from Equine Platelet-Rich Plasma In Vitro

Introduction

Extracorporeal shockwave therapy (ESWT) and platelet-rich plasma (PRP) are common treatments for soft tissue injuries in horses. Shockwave triggers cell specific responses to promote healing. Growth factors released from PRP also promote healing. It has been hypothesized that greater growth factor release would amplify the healing process. The combination of ESWT and PRP could promote healing in injured tendons and ligaments in the horse. The objective of this study was to determine if application of shockwaves to PRP samples increases the concentration of transforming growth factor-β₁ (TGF-β₁) and platelet-derived growth factor ββ (PDGF-ββ) released from the platelets in vitro.

Materials and methods

PRP was produced from blood drawn from six horses. The PRP from each horse was exposed to the following treatments: (1) positive control (freeze-thaw cycle), (2) untreated negative control, or shockwaves with either (3) a "standard probe" (ESWT-S) with a 2 cm focal width and medium energy density or (4) a "power probe" (ESWT-P) with a 1 cm focal width and high energy density. After each treatment, the samples were centrifuged, and the supernatant was harvested. The supernatant was then used for growth factor quantification via commercially available ELISA kits for TGF-β₁ and PDGF-ββ.

Results

Concentrations of TGF-β₁ and PDGF-ββ in PRP that underwent a freeze-thaw cycle were significantly increased compared with all other treatments. Both ESWT-S and ESWT-P resulted in significantly increased TGF-β₁ concentrations, 46 and 33%, respectively, when compared with the negative control. Both ESWT-S and ESWT-P resulted in significantly increased PDGF-ββ concentrations, 219 and 190%, respectively, when compared with the negative control.

Discussion

These data indicate that the application of ESWT to PRP increases the expression of growth factors in vitro. This suggests that the combination therapy of local PRP injection followed by ESWT may stimulate release of growth factors from platelets after they have been injected into the area of injury.

Conclusion

The combination of PRP and ESWT might result in synergism of two modalities previously utilized individually for tendon and ligament injuries in horses.

Effects of three blood derived products on equine corneal cells, an in vitro study

BACKGROUND

Despite advances in therapy of corneal ulcerative diseases in horses, a vast number of cases require surgical intervention, due to poor response to treatment. Topical application of serum has been used for many years, based on its anticollagenolytic properties and the presence of growth factors promoting corneal wound healing. However, although other blood derived products i.e. platelet rich plasma (PRP), plasma rich in growth factors (PRGF) have been widely used in equine orthopaedics and in human ophthalmology, no reports of the effects of these blood derived products exist in equine ophthalmology.

OBJECTIVES

To determine in vitro effects of PRGF and PRP on equine corneal cells compared with serum.

STUDY DESIGN

Prospective controlled cohort study.

METHODS

Blood from 35 healthy horses was used to produce serum, PRGF (Endoret^® ), and PRP (E-PET™). Limbal- and stromal cells were isolated from healthy corneas of six horses and treated with 20% serum, 20% PRGF or 20% PRP. Proliferation rates and migration capacity were analysed in single cell cultures as well as co-culture systems.

RESULTS

Cell proliferation increased with PRP treatment, remained constant in PRGF treated cells, and declined upon serum treatment over a period of 48 h. Migration capacity was significantly enhanced with PRP treatment, compared with PRGF treatment. Intact leucocytes, mainly eosinophils, were only detected in PRP.

MAIN LIMITATIONS

Due to the study design use of autologous blood products on corneal cells was not possible.

CONCLUSIONS

The results demonstrate beneficial effects of PRP on proliferation as well as migration capacity of equine corneal cells in vitro. In vivo studies are warranted to determine further beneficial effects of PRP in horses with corneal ulcers.

Effect of single intralesional treatment of surgically induced equine superficial digital flexor tendon core lesions with adipose-derived mesenchymal stromal cells: a controlled experimental trial

Background

Adipose tissue is a promising source of mesenchymal stromal cells (MSCs) for the treatment of tendon disease. The goal of this study was to assess the effect of a single intralesional implantation of adipose tissue-derived mesenchymal stromal cells (AT-MSCs) on artificial lesions in equine superficial digital flexor tendons (SDFTs).

Methods

During this randomized, controlled, blinded experimental study, either autologous cultured AT-MSCs suspended in autologous inactivated serum (AT-MSC-serum) or autologous inactivated serum (serum) were injected intralesionally 2 weeks after surgical creation of centrally located SDFT lesions in both forelimbs of nine horses. Healing was assessed clinically and with ultrasound (standard B-mode and ultrasound tissue characterization) at regular intervals over 24 weeks. After euthanasia of the horses the SDFTs were examined histologically, biochemically and by means of biomechanical testing.

Results

AT-MSC implantation did not substantially influence clinical and ultrasonographic parameters. Histology, biochemical and biomechanical characteristics of the repair tissue did not differ significantly between treatment modalities after 24 weeks. Compared with macroscopically normal tendon tissue, the content of the mature collagen crosslink hydroxylysylpyridinoline did not differ after AT-MSC-serum treatment (p = 0.074) while it was significantly lower (p = 0.027) in lesions treated with serum alone. Stress at failure (p = 0.048) and the modulus of elasticity (p = 0.001) were significantly lower after AT-MSC-serum treatment than in normal tendon tissue.

Conclusions

The effect of a single intralesional injection of cultured AT-MSCs suspended in autologous inactivated serum was not superior to treatment of surgically created SDFT lesions with autologous inactivated serum alone in a surgical model of tendinopathy over an observation period of 22 weeks. AT-MSC treatment might have a positive influence on collagen crosslinking of remodelling scar tissue. Controlled long-term studies including naturally occurring tendinopathies are necessary to verify the effects of AT-MSCs on tendon disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0564-8) contains supplementary material, which is available to authorized users.