Effect of Continuous Digital Hypothermia on Lamellar Inflammatory Signaling When Applied at a Clinically-Relevant Timepoint in the Oligofructose Laminitis Model

Continuous digital hypothermia for prevention and treatment of equine acute laminitis: A practical review

Laminitis is a severely debilitating and life-threatening condition that occurs as a consequence of different primary triggering factors. Continuous digital hypothermia (CDH) is recommended in horses at risk of, or diagnosed with, acute laminitis due to its several physiological and biochemical alterations that may be positive for the prevention and early treatment of the condition, representing a low risk of adverse effects. Modulation of the inflammatory response, profound vasoconstriction, and prevention of tissue damage are the most notable protective effects of cryotherapy on the lamellae. This practical review aims to summarize the published literature evaluating CDH efficacy in the prevention and early treatment of acute laminitis in horses, highlighting the most important clinical findings and discussing the best methods to provide cryotherapy. Nineteen publications evaluated different CDH methods, including the use of commercially available ice boots or fluid bags filled with iced water or crushed ice, as well as alternatives to immersion in ice, e.g., frozen gel packs and a perfused cuff prototype. Although some techniques were effective for cooling and maintaining the hooves below the optimal temperature of 10 °C, relevant limitations such as labor intensiveness, reliance on an ice source and price make its use impractical in some clinical situations. Twelve experimental studies assessed the efficacy of CDH on the prevention or early treatment of laminitis, finding multiple positive effects in terms of clinical improvement, immunological and inflammatory modulation, and histological protection. After the analysis of the literature, the clinical importance of CDH in different stages of laminitis remains clear. However, it also highlights the need for a safer, more user-friendly, and more effective method of cryotherapy that can be used both in a hospital and an ambulatory setting.

Enhanced Autophagy in Damaged Laminar Tissue of Acute Laminitis Induced by Oligofructose Overloading in Dairy Cows

This study was aimed at determining the autophagy activity in the laminar tissue of dairy cows with oligofructose-induced laminitis. Twelve healthy non-pregnant Holstein cows were randomly divided into two groups of six cows each, entitled the control group and the oligofructose overload group (OF group), respectively. At 0 h, cows in the OF group were gavaged with oligofructose (17 g/kg BW) dissolved in warm deionized water (20 mL/kg BW) through an oral rumen tube, and the dairy cows in the control group were gavaged with the same volume of deionized water by the same method. At -72 h before, as well as 0 h, 6 h, 12 h, 18 h, 24 h, 36 h, 48 h, 60 h, and 72 h after perfusion, clinical evaluations of both groups were monitored. After 72 h, the laminar tissues of the dairy cows in both groups were collected to examine the genes and proteins. The gene expression of ATG5, ATG12, and Beclin1 significantly increased (p < 0.05), whereas that of P62 and mTOR significantly decreased (p < 0.01) in the OF group relative to the control group. The protein expression of Beclin-1 significantly increased (p < 0.05), while that of LC3II significantly decreased (p < 0.05) in the OF group relative to the control group. However, the protein expression of P62 non-significantly reduced (p > 0.05) in the OF group comparative to the control group. Furthermore, the distribution of the Beclin1 protein in the laminar tissue significantly increased (p < 0.01), while that of the P62 protein significantly decreased (p < 0.05) in the OF group than the control group. These findings indicate that the imbalanced gene and protein-level status of autophagy-related markers may be the basic cause for the failure of the epidermal attachment. However, a more detailed gene and protein-level study is needed to further clarify the role of autophagy in the pathogenesis of bovine laminitis.

Laminitis Updates: Sepsis/Systemic Inflammatory Response Syndrome-Associated Laminitis

Sepsis or systemic inflammatory response syndrome (SIRS) -associated laminitis is a sequela to primary inflammatory conditions (eg, colitis, ischemic intestinal injury, pneumonia, metritis) and results from a dysregulated systemic inflammatory response that ultimately affects the digital lamellae. Local chemokine production, leukocyte migration, and proinflammatory mediator production occur within the lamellae that can lead to catastrophic lamellar failure. Controlling the primary disease, providing supportive care and anti-inflammatory therapy, applying digital cryotherapy, and providing mechanical support are cornerstones to the prevention of sepsis/SIRS-associated laminitis. Novel therapies targeting specific signaling pathways may provide additional therapeutic options in the future.

Cryotherapy Techniques: Best Protocols to Support the Foot in Health and Disease

Treatment of equine laminitis continues to be a challenge despite recent advancements in knowledge of the pathophysiology of laminitis. With more evidence supporting its use, distal limb hypothermia or cryotherapy has become a standard of care for both prevention of laminitis and treatment of the early stages of acute laminitis. Recent studies have demonstrated that cryotherapy reduces the severity of sepsis-related laminitis and hyperinsulinemic laminitis in experimental models and reduces the incidence of laminitis in clinical colitis cases. This article reviews the recent literature supporting the use of distal limb cryotherapy in horses.

Continuous digital hypothermia reduces expression of keratin 17 and 1L-17A inflammatory pathway mediators in equine laminitis induced by hyperinsulinemia

The euglycemic hyperinsulinemic clamp model (EHC) of equine endocrinopathic laminitis induces rapid loss of lamellar tissue integrity, disrupts keratinocyte functions, and induces inflammation similar to natural disease. Continuous digital hypothermia (CDH) blocks tissue damage in this experimental model, allowing identification of specific genes or molecular pathways contributing to disease initiation or early progression. Archived lamellar tissues (8 horses, 48 h EHC treatment, including CDH-treated front limbs) were used to measure relative expression levels of genes encoding keratin 17 (KRT17), a stress-induced intermediate filament protein, and genes upregulated downstream of keratin 17 and/or interleukin 17A (IL-17A), as mediators of inflammation. Compared to front or hind limbs at ambient temperature, CDH resulted in significantly lower expression of KRT17, CCL2, CxCL8, PTGS2 (encoding COX2), IL6, TNFα, S100A8 and MMP1. By immunofluorescence, COX2 was robustly expressed in lamellar keratinocytes from ambient limbs, but not in CDH-treated limbs. Genes not significantly reduced by CDH were IL17A, DEFB4B, S100A9 and MMP9. Overall, 8 of 12 genes were expressed at lower levels in the CDH-treated limb. These 8 genes are expressed by wounded or stress-activated keratinocytes in human disease or mouse models, highlighting the role of keratinocytes in equine laminitis.

Gene Expression of Metalloproteinases and Endogenous Inhibitors in the Lamellae of Dairy Heifers With Oligofructose-Induced Laminitis

Bovine laminitis leads to huge economic losses and animal welfare problems in the dairy industry worldwide. Numerous studies suggested that several metalloproteinases (MPs) may play vital roles in the failure of epidermal attachment. To the best of our knowledge, the present study is the first to investigate and characterize the gene-level changes in distinct MPs and endogenous inhibitors using oligofructose (OF)-induced bovine laminitis model. The objective of this study was to determine aberrant MPs and related inhibitors of bovine laminitis in gene level, and to provide reasonable directions for the further protein-level research. Twelve normal Chinese Holstein dairy heifers were randomly divided into treatment group (n = 6) and control group (n = 6). The heifers in the treatment group were administered with OF solutions at a dose of 17 g/kg of body weight via a stomach tube. The heifers were then humanely euthanized when they met the criteria of bovine laminitis. The heifers in the control group were administered with deionized water at a dose of 2 L/100 kg of body weight. They humanely euthanized at 72 h. The gene expressions of MPs and endogenous inhibitors, namely, matrix metalloproteinases (MMPs), A disintegrin and metalloproteinases (ADAMs), and A disintegrin and metalloproteinase with thrombospondin motifs (ADAMTs), and tissue inhibitors of metalloproteinases (TIMPs) in the lamellae from two groups were determined via real-time quantitative PCR. The gene expressions of MMP-2, MMP-9, ADAMTS-4, and ADAMTS-5 significantly increased (P < 0.05), whereas that of TIMP-2 significantly decreased (P < 0.05) in the treatment group relative to the control group. No significant difference was found in the gene expressions of ADAM-10, ADAM-17, TIMP-1, and TIMP-3. These results indicated that the gene-level imbalanced condition of MPs and their TIMPs may be the basic cause for the failure of epidermal attachment. At the same time, more detailed protein-level studies would be needed to further clarify the roles of MPs and TIMPs in the pathogenesis of bovine laminitis, especially to MMP-2, MMP-9, ADAMTS-4, ADAMTS-5, TIMP-2 as well as related substrates (e.g., aggrecan and versican).

Interleukin-17A pathway target genes are upregulated in Equus caballus supporting limb laminitis

Supporting Limb Laminitis (SLL) is a painful and crippling secondary complication of orthopedic injuries and infections in horses, often resulting in euthanasia. SLL causes structural alterations and inflammation of the interdigitating layers of specialized epidermal and dermal tissues, the lamellae, which suspend the equine distal phalanx from the hoof capsule. Activation of the interleukin-17A (IL-17A)-dependent inflammatory pathway is an epidermal stress response that contributes to physiologic cutaneous wound healing as well as pathological skin conditions. As a first test of the hypothesis that hoof lamellae of horses diagnosed with SLL also respond to stress by activating the IL-17A pathway, the expression of IL-17A, IL-17 receptor subunit A and 11 IL-17A effector genes was measured by RT-PCR or qPCR. Lamellar tissue was isolated from Thoroughbreds euthanized due to naturally occurring SLL and in age and breed matched non-laminitic controls. By RT-PCR, the IL-17 Receptor A subunit was expressed in both non-laminitic and laminitic tissues, while IL-17A was primarily detectable in laminitic tissues. IL-17A target gene expression was undetectable in non-laminitic samples with the exception of weak detection of DEFB4B, S100A9 and PTSG2. In contrast, all target genes examined, except CCL20, were expressed by some or all laminitic samples. By qPCR, severe acute (n = 7) SLL expressed ~15–100 fold higher levels of DEFB4B and S100A9 genes compared to non-laminitic controls (n = 8). DEFB4B was also upregulated in developmental/subclinical (n = 8) and moderate acute (n = 7) by ~ 5-fold, and in severe chronic (n = 5) by ~15–200 fold. In situ hybridization (DEFB4) and immunofluorescence (calprotectin, a dimer of S100A9/S100A8 proteins) demonstrated expression in keratinocytes, primarily in suprabasal cell layers, from SLL samples. These data demonstrate upregulation of a cohort of IL-17A target genes in SLL and support the hypothesis that similarities in the response to stresses and damage exist between equine and human epidermal tissues.

Laminar Inflammation Responses in the Oligofructose Overload Induced Model of Bovine Laminitis

Bovine laminitis causes substantial economic losses and animal welfare problems in dairy farms worldwide. Previously published studies have reported that the inflammatory response plays a central role in the pathogenesis of the disease. To our knowledge, inflammation associated with bovine laminitis induced by high levels of exposure to oligofructose (OF) has not been reported and characterized. In fact, the disease manifestations in this model closely approximate those of clinical laminitis. The objective of this study was to characterize the inflammatory response in OF-induced bovine laminitis. A total of 12 Chinese Holstein dairy heifers were utilized in this study. The heifers were randomly divided into two groups, treatment (n = 6) and control (n = 6). The treatment group heifers were administered OF solutions via a stomach tube (dose: 17 g/kg of body weight). Upon development of a lameness score of 2 with consecutive positive reactions in the same claw, they would be humanely euthanized. Control heifers were administered deionized water (dose: 2 L/100 kg of body weight) and humanely euthanized at 72 h. Real-time quantitative PCR (qPCR) assays were performed to determine the messenger RNA (mRNA) concentrations of inflammatory mediators in the lamellae. Concentrations of interleukin (IL)-1β, IL-6, IL-8, C-X-C motif chemokine ligand-1 (CXCL-1), macrophage cationic peptide-2 (MCP-2), E-selectin, intercellular adhesion molecule-1 (ICAM-1), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase-1 (iNOS-1), and plasminogen activator inhibitor-1 (PAI-1) were significantly increased (P < 0.05) in the treatment group. No significant difference was found for tumor necrosis factor alpha (TNF-α), IL-10, CXCL-6, and MCP-1. These results demonstrated and characterized the laminar inflammatory response leading to the pathogenesis of bovine laminitis at the early stages.

Effect of digital hypothermia on lamellar inflammatory signaling in the euglycemic hyperinsulinemic clamp laminitis model

Background

Continuous digital hypothermia (CDH) prevents lamellar failure in the euglycemic hyperinsulinemic clamp (EHC) model of laminitis, but the protective mechanisms are unclear.

Hypothesis/Objectives

To determine if CDH inhibits lamellar inflammatory signaling in the EHC model of laminitis.

Animals

Eight Standardbred horses.

Methods

Prospective experimental study. Horses underwent an EHC, with 1 forelimb treated with CDH and the other kept at ambient temperature (AMB). Horses were euthanized 48 hours after initiation of the EHC and lamellar tissue was analyzed via polymerase chain reaction (pro‐inflammatory cytokine and chemokine genes—CXCL1, CXCL6, CXCL8, IL‐6, MCP‐1, MCP‐2, IL‐1β, IL‐11, cyclooxygenase 1 and 2, tumour necrosis factor‐alpha [TNF‐α], E‐selectin, and intercellular adhesion molecule‐1 [ICAM‐1]) and immunoblotting (phosphorylated and total signal transducer and activator of transcription 1 [STAT1] and STAT3).

Results

Compared to AMB, lamellar messenger ribonucleic acid (mRNA) concentrations of CXCL6 (P =.02), CXCL8 (P = .008), IL‐6 (P = .008), IL‐1β (P = .008), IL‐11 (P = .008), and cyclooxygenase‐2 (P = .008) were decreased in CDH. Cyclooxygenase‐1 (P = .008) was increased in CDH, while CXCL1 (P = .15), MCP‐1 (P = .05), MCP‐2 (P = .46), TNF‐α (P = .05), E‐selectin (P = .15), and ICAM‐1 (P = .15) mRNA were not significantly different. Compared to AMB, lamellar concentration of total STAT3 protein was decreased in CDH (P < .001), but there was no change in phosphorylated STAT3 (P‐STAT3 [S727] P = .19; P‐STAT3 [Y705] P = .05). There was no change in lamellar concentrations of total STAT1 (P = .75) or phosphorylated STAT1 (P‐STAT1 [S727], P = .25; P‐STAT1 [Y701], P = .64).

Conclusions and Clinical Importance

These data add further support for the use of CDH as a first aid treatment for severe acute laminitis associated with hyperinsulinemia in horses.

Differential Proteomic Expression of Equine Cardiac and Lamellar Tissue During Insulin-Induced Laminitis

Endocrinopathic laminitis is pathologically similar to the multi-organ dysfunction and peripheral neuropathy found in human patients with metabolic syndrome. Similarly, endocrinopathic laminitis has been shown to partially result from vascular dysfunction. However, despite extensive research, the pathogenesis of this disease is not well elucidated and laminitis remains without an effective treatment. Here, we sought to identify novel proteins and pathways underlying the development of equine endocrinopathic laminitis. Healthy Standardbred horses (n = 4/group) were either given an electrolyte infusion, or a 48-h euglycemic-hyperinsulinemic clamp. Cardiac and lamellar tissues were analyzed by mass spectrometry (FDR = 0.05). All hyperinsulinemic horses developed laminitis despite being previously healthy. We identified 514 and 709 unique proteins in the cardiac and lamellar proteomes, respectively. In the lamellar tissue, we identified 14 proteins for which their abundance was significantly increased and 13 proteins which were significantly decreased in the hyperinsulinemic group as compared to controls. These results were confirmed via real-time reverse-transcriptase PCR. A STRING analysis of protein-protein interactions revealed that these increased proteins were primarily involved in coagulation and complement cascades, platelet activity, and ribosomal function, while decreased proteins were involved in focal adhesions, spliceosomes, and cell-cell matrices. Novel significant differentially expressed proteins associated with hyperinsulinemia-induced laminitis include talin−1, vinculin, cadherin-13, fibrinogen, alpha-2-macroglobulin, and heat shock protein 90. In contrast, no proteins were found to be significantly differentially expressed in the heart of hyperinsulinemic horses compared to controls. Together, these data indicate that while hyperinsulinemia induced, in part, microvascular damage, complement activation, and ribosomal dysfunction in the lamellae, a similar effect was not seen in the heart. In brief, this proteomic investigation of a unique equine model of hyperinsulinemia identified novel proteins and signaling pathways, which may lead to the discovery of molecular biomarkers and/or therapeutic targets for endocrinopathic laminitis.

The effect of continuous digital hypothermia on lamellar energy metabolism and perfusion during laminitis development in two experimental models

BACKGROUND

Continuous digital hypothermia (CDH) prevents lamellar failure in the euglycaemic hyperinsulinaemic clamp (EHC) and oligofructose (OF) laminitis models, but the mechanisms remain unclear.

OBJECTIVES

To evaluate the effects of CDH on lamellar energy metabolism and perfusion in healthy horses and during EHC and OF laminitis models.

STUDY DESIGN

In vivo experiment.

METHODS

Archived samples were used from Standardbred geldings that received no treatment (CON) (n = 8) or underwent EHC (n = 8) or OF (n = 6) laminitis models. Both forelimbs were instrumented with a lamellar microdialysis system, and one forelimb was cooled (CDH) with the other maintained at ambient temperature (AMB). Microdialysate was collected every 6 hours and analysed for glucose, lactate and pyruvate concentrations and lactate to pyruvate ratio (L:P). Microdialysis urea clearance was used to estimate lamellar tissue perfusion. Data were analysed using a mixed-effects linear regression model.

RESULTS

Glucose did not change in CDH limbs relative to AMB in CON (P = .3), EHC (P = .3) or OF (P = .6) groups. There was a decrease in lactate (P < .001) and pyruvate (P < .01) in CDH limbs relative to AMB in all groups. L:P decreased in CON CDH relative to CON AMB (P < .001) but was not different in EHC (P = .6) and OF (P = .07) groups. Urea clearance decreased in CDH limbs relative to AMB in CON (P = .002) and EHC (P < .001), but not in OF (P = .4).

MAIN LIMITATIONS

The EHC model may not mimic natural endocrinopathic laminitis.

CONCLUSIONS

CDH caused a marked decrease in lamellar glucose metabolism (CON, EHC and OF) and perfusion (CON and EHC) without affecting lamellar glucose concentration. Although cellular energy failure is not a primary pathophysiological event in EHC and OF laminitis models, CDH may act by limiting energy supply to pathologic cellular processes whilst preserving those critical to lamellar homoeostasis.

Influence of digital hypothermia on lamellar events related to IL-6/gp130 signalling in equine sepsis-related laminitis

BACKGROUND

Interleukin-6 (IL-6) is consistently increased in the digital lamellae in different studies of sepsis-related laminitis (SRL). IL-6 signalling through the gp130 receptor activates similar signalling (i.e. mTORC1-related signalling) previously reported to be activated in models of endocrinopathic laminitis.

OBJECTIVES

To assess the activation state of signalling proteins downstream of IL-6/gp130 receptor complex activation in an experimental model of SRL.

STUDY DESIGN

Randomised experimental study.

METHODS

Lamellar phospho-(P) protein concentrations downstream of the IL-6/gp130 receptors were assessed in the oligofructose (OF) model of SRL. Fifteen Standardbred horses were administered water (CON, n = 8) or oligofructose (OF, n = 7) via a nasogastric tube. At 12 h post-OF/water administration, one randomly assigned forelimb was exposed to continuous digital hypothermia (CDH) by placement in ice water (ICE, maintained at <7°C); the other forelimb was maintained at ambient temperature (AMB). Lamellar tissue samples were collected after 24 h of CDH from both ICE and AMB forelimbs and immediately snap-frozen. Lamellar proteins of interest were assessed by immunoblotting and immunofluorescence.

RESULTS

Immunoblotting revealed increase (P<0.05) in the phosphorylation states of Akt (Ser 473), RPS6 (Ser235/236), RPS6 (Ser240/244), STAT3 (Ser727) and STAT3 (Tyr705) in lamellar tissue from OF-treated animals (AMB OF vs. AMB CON limbs); CDH resulted in decreased (P<0.05) lamellar concentrations of phosphorylated Akt, p70S6K, RPS6 (235/236), RPS6 (240/244) and STAT3 (S727) in OF-treated animals (AMB OF vs. ICE OF). Immunofluorescence showed that activated/phosphorylated forms of RPS6 and STAT3 were primarily localised to lamellar epithelial cells.

MAIN LIMITATIONS

The nature, sequence and timing of sub-cellular events in this experimental model may differ from those that accompany naturally occurring sepsis.

CONCLUSIONS

There were increased lamellar concentrations of activated signalling proteins downstream of the IL-6/Gp130 receptor complex in OF-treated horses; CDH inhibited this activation for the majority of the proteins assessed. These results demonstrate similar lamellar signalling (e.g. mTORC1-related signalling) and, therefore, possible therapeutic targets occurring in sepsis-related laminitis as previously reported in models of endocrinopathic laminitis.

A "modified Obel" method for the severity scoring of (endocrinopathic) equine laminitis

BACKGROUND

Laminitis is a common equine disease characterized by foot pain, and is commonly diagnosed using a five-grade Obel system developed in 1948 using sepsis-related cases. However, endocrinopathic laminitis is now the most common form of the disease and clinical signs may be mild, or spread across two Obel grades. This paper describes a modified method which assigns scores to discreet clinical signs, providing a wider scale suitable for use in a research setting.

METHODS

The "modified Obel" method was developed using an iterative process. First, a prototype method was developed during the detailed observation of 37 ponies undergoing a laminitis induction experiment. The final method was refined and validated using video footage taken during the induction study and from a clinical trial of naturally occurring endocrinopathic laminitis cases. The Obel method was deconstructed and key laminitis signs were evaluated to develop a three-stage, five criteria method that employs a severity scale of 0-12. Veterinarians (n = 28) were recruited to watch and assess 15 video recordings of cases of varying severity, using the Obel and "modified Obel" methods. The inter-observer agreement (reproducibility) was determined using Kendall's coefficient of concordance (Kendall W) and Krippendorf's alpha reliability coefficient. A total of 14 veterinarians repeated the exercise 2-4 weeks after their original assessment, to determine intra-observer agreement (repeatability), assessed using a weighted kappa statistic (kw). Agreement between methods was calculated by converting all "modified Obel" scores to Obel grades and calculating the mean and distribution of the differences.

RESULTS

The "modified Obel" and Obel methods showed excellent and similar inter-observer agreement based on the Kendall W value (0.87, P < 0.001 vs. 0.85, P < 0.001) and Krippendorf's alpha (95% CI) value (0.83 [0.53-0.90] vs. 0.77 [0.55-0.85]). Based on the kw value, the "modified Obel" method also had substantial repeatability, although slightly less than the Obel method, (0.80 vs. 0.91). Excellent agreement between the methods was found, with the mean difference (95% CI), comparing the Obel grade, with the "modified Obel" score converted to an Obel grade, being -0.12 (-0.19 to -0.06) grades. The Obel and converted "modified Obel" grades were identical 62% of the time (259/420) and a difference of one grade (higher or lower) occurred in 35% of cases (148/420).

CONCLUSION

Both methods show excellent agreement, reproducibility and repeatability when used to diagnose endocrinopathic laminitis. The "modified Obel" method is a three-step examination process for severity-scoring of endocrinopathic laminitis, initially proposed for use within a research setting. When using the modified method a diagnosis of laminitis also requires clinical acumen. The allocation of scores for specific clinical signs should be particularly useful in research trials monitoring laminitis recovery.

A Comparative Review of Equine SIRS, Sepsis, and Neutrophils

The most recent definition of sepsis in human medicine can be summarized as organ dysfunction caused by a dysregulated host response to infection. In equine medicine, although no consensus definition is available, sepsis is commonly described as a dysregulated host systemic inflammatory response to infection. Defense against host infection is the primary role of innate immune cells known as neutrophils. Neutrophils also contribute to host injury during sepsis, making them important potential targets for sepsis prevention, diagnosis, and treatment. This review will present both historical and updated perspectives on the systemic inflammatory response (SIRS) and sepsis; it will also discuss the impact of sepsis on neutrophils, and the impact of neutrophils during sepsis. Future identification of clinically relevant sepsis diagnosis and therapy depends on a more thorough understanding of disease pathogenesis across species. To gain this understanding, there is a critical need for research that utilizes a clearly defined, and consistently applied, classification system for patients diagnosed with, and at risk of developing, sepsis.

Continuous digital hypothermia prevents lamellar failure in the euglycaemic hyperinsulinaemic clamp model of equine laminitis

BACKGROUND

Continuous digital hypothermia can prevent the development and progression of laminitis associated with sepsis but its effects on laminitis due to hyperinsulinaemia are unknown.

OBJECTIVES

To determine the effects of continuous digital hypothermia on laminitis development in the euglycaemic hyperinsulinaemic clamp model.

STUDY DESIGN

Randomised, controlled (within subject), blinded, experiment.

METHODS

Eight clinically normal Standardbred horses underwent laminitis induction using the euglycaemic hyperinsulinaemic clamp model (EHC). At initiation of the EHC, one forelimb was continuously cooled (ICE), with the other maintained at ambient temperature (AMB). Dorsal lamellar sections (proximal, middle, distal) were harvested 48 h after initiation of the EHC and were analysed using histological scoring (0-3) and histomorphometry. Cellular proliferation was quantified by counting epidermal cell nuclei staining positive with an immunohistochemical proliferation marker (TPX2).

RESULTS

Severe elongation and disruption of SEL with dermo-epidermal separation (score of 3) was observed in all AMB feet at one or more section locations, but was not observed in any ICE sections. Overall 92% of the AMB sections received the most severe histological score (grade 3) and 8% were grade 2, whereas ICE sections were classified as either grade 1 (50%) or grade 2 (50%). Relative to AMB feet, ICE sections were 98% less likely to exhibit grades 2 or 3 (OR: 0.02, 95% CI 0.001, 0.365; P<0.01). Histomorphometry measurements of total and nonkeratinised primary epidermal lamellar length were significantly increased (P<0.01) in AMB limbs compared with ICE. TPX2 positive cell counts were significantly increased (P<0.01) in AMB limbs compared with ICE.

MAIN LIMITATIONS

Continuous digital hypothermia was initiated before recognition of laminitis and therefore the clinical applicability requires further investigation.

CONCLUSIONS

Continuous digital hypothermia reduced the severity of laminitis in the EHC model and prevented histological lesions compatible with lamellar structural failure.

Whole body and partial body cryotherapies - lessons from human practice and possible application for horses

Whole body and partial body cryotherapies (WBC and PBC) have been successfully used in human medicine, and currently also are being proposed in veterinary practice.

In horses, only the partial body cryotherapy provided in cryosauna is considered, due to the technical conditions. These therapies have been dedicated to human patients with rheumatic and inflammatory diseases as well as an assistance during training in athletes. The anti-inflammatory effects have been demonstrated clinically and indicated by the changes in several hematological and immunological parameters, however, various patterns have been described, depending on the protocols and the treating subjects. The numbers of white blood cells and the differential counts either increased or remained unchanged but the cytokine concentrations generally changed towards various anti-inflammatory profiles and the modifications of immunological molecules having paracrine effects have been reported.

In equine practice, local cold therapies have been successfully used, so the therapy in cryosauna, which allows for a much shorter procedure with much lower temperature seems promising.