Alterations of epidermal proliferation and cytokeratin expression in skin biopsies from heavy draught horses with chronic pastern dermatitis

The Estimation of Genetic Parameters for Chronic Progressive Lymphedema and Body Traits in the Rhenish German Draught Horse

Chronic progressive lymphedema (CPL) is a prevalent and progressive disease in Rhenish German draught horses. The objective of our follow-up study was to evaluate the heritability of this disease in Rhenish German draught horses using pedigree-based and genomic relationship matrices. We employed linear and threshold animal models. Models included the random animal effect and effects of breeding association, coat colour, sex, and age within sex, and farm-related factors, on CPL scores. In addition, we estimated heritabilities in models assuming censoring for data when horses were below an age of 1-15 years. The heritabilities of CPL scores across all ages were 0.595 ± 0.131 and 0.482 ± 0.105 in the threshold and linear animal model with pedigree-based relationship matrices, respectively. The restriction of data to horses with a minimum age at examination or accounting for censored data in younger animals showed an increase in heritabilities of CPL scores up to 0.788 ± 0.168 (threshold model) and 0.752 ± 0.153 (linear model) at an age of 7-8 years. Analyses including genomic relationship matrices yielded very similar estimates, but with smaller standard errors than pedigree-based analyses. Heritabilities in threshold models for CPL prevalence (CPL-bin-score) and the number of affected limbs (CPL-bin-sum) were 0.176-0.189 ± 0.061-0.064 and 0.375-0.433 ± 0.164-0.170, respectively. We were able to show moderately to highly positive genetic correlations between the CPL score and cannon bone circumference (0.529-0.825), height at withers (0.338-0.555), and skinfold thickness (0.241-0.517). Using the dichotomous trait for the CPL score and the genomic relationship matrix resulted in corresponding estimates of 0.868, 0.793, and 0.784, respectively. This study showed the great importance of additive genetic variation influencing the expression of chronic progressive lymphedema in Rhenish German draught horses. Therefore, further research is warranted to implement breeding programmes in a small breeding population that exploit the potential of additive genetic differences among animals for reducing the prevalence and severity of lesions of this incurable disease.

Airbrushed nanofibers with bioactive core and antibacterial shell for wound healing application

Acute and chronic wounds are vulnerable to infection and delayed healing and require critical care and advanced wound protection. To overcome the challenges, dual therapy of antibacterial and growth factors will be a novel wound care strategy. The present study explores airbrushed core-shell nanofiber for dual delivery of epidermal growth factor (EGF) and amoxicillin (AMOX) in a sustained manner. A blend of polycaprolactone (PCL)-polyethylene oxide (PEO) was used to prepare the shell compartment for amoxicillin loading and poly-DL-lactide (PDLLA) core for EGF loading by using a customized airbrush setup. Characterization result shows a uniform distribution of nanofibers ranging between 200 and 500 nm in diameter. Amoxicillin loading in the shell compartment offers an initial burst release followed by a sustained release for up to 14 days. Whereas EGF in the core part shows a continuous sustained release throughout the release study.In-vitrostudy indicates the biocompatibility of EGF-AMOX loaded core-shell nanofibers with human dermal fibroblast cell (HDF) cells and a higher cellular proliferation compared to control samples. Gene expression data show an increase in fold change of collagen I and tropoelastin expression, indicating the regenerative properties of EGF-AMOX encapsulated nanofiber. The combination of bioactive core (EGF) and antibiotic shell (amoxicillin) in an airbrushed nanofibrous scaffold is a novel approach, which is the first time explored to deliver sustainable therapy to treat skin wounds. Our results demonstrate that PCL-PEO-Amoxicillin/PDLLA-EGF-loaded core-shell nanofibers are promising dual therapy scaffolds to deliver effective skin wound care, with the possibility of direct deposition on the wound.

Chronic Progressive Lymphedema in Belgian Draft Horses: Understanding and Managing a Challenging Disease

Chronic progressive lymphedema (CPL) in draft horses is characterized by increased dermal thickness and fibrosis, with the development of skinfolds and nodules, hyperkeratosis, and ulcerations on the distal limbs of affected horses. Secondary bacterial, fungal, or parasitic infections frequently complicate and aggravate the lesions, as well as the progression of this disease. CPL has a particularly high prevalence of up to 85.86% in the Belgian draft horse breed. Due to the disease's progressive and incurable nature, affected horses are often euthanized prematurely. The treatment options are solely symptomatic, aimed at improving the horse's quality of life. Despite the severity of this condition, many uncertainties about its etiology and pathogenesis still remain to date. The established scientific research on CPL is rather limited, although there is an urgent need for strategies to tackle this disease. This review summarizes the available knowledge, serving as a guideline for practitioners, and provides perspectives for future research programs.

Prevalence of Chronic Progressive Lymphedema in the Rhenish German Draught Horse

Chronic progressive lymphedema (CPL) is a common disease in Rhenisch German draught horses. The objective of our study was to evaluate the prevalence of this disease and its progression with age in 493 Rhenish German draught horses from different regions in Germany. We employed generalized linear models with binomial, multinomial, and normal distributions to analyse the effects of breeding association, coat colour, sex and age within sex, time of examination, limb on which CPL was recorded, and farm-related factors on disease scores. The occurrence and severity of CPL were significantly influenced by breeding area, sex, coat colour, and interaction of age by sex. Males had significantly higher CPL-scores than geldings (1.92-fold) and females (5.02-fold) as well as a faster (1.85-fold) disease progression per year of life than females (1.44-fold) and geldings (1.25-fold). Regression on age within sex was still significant when age was restricted to a minimum of 7 years in the analysis. Bay horses exhibited 1.77-fold and 2.19-fold higher CPL-scores than chestnut and black horses. Keeping horses on pasture and keeping bedding clean reduced CPL-scores, whereas feeding of hay silage and concentrates during winter increased CPL-scores. Our analysis revealed significant regression coefficients of cannon bone circumference on CPL-scores. Relationships with hoof measures and skinfold diameter at the neck were not found. In conclusion, differences among breeding districts and sexes by age had the largest impact on CPL prevalence and scores. Disease progression was evident up to a mean age of 16 years in males and 20 years in females. The identification of risk factors and their effects on CPL should help to reduce the occurrence and progression of CPL.

Epidemiological observations on pastern dermatitis in young horses and evaluation of essential fatty acid spot-on applications with or without phytosphingosine as prophylactic treatment

Background - Equine pastern dermatitis (EPD) is a common multifactorial clinical syndrome in horses. Treatment can be difficult; pathogenesis and triggering factors cannot always be determined. Objectives - To assess risk factors for developing EPD in a large group of horses kept under the same conditions and to analyse whether or not a spot-on containing essential fatty acids and antimicrobial agents is able to prevent the development of EPD or accelerate the healing process. Conclusion and clinical importance - Moisture and lack of pigmentation predisposed to EPD. Topical application of the tested spot-on once weekly did not prevent the disease. A positive effect of both spot-on products on the severity of EPD lesions was detected.

Immunohistochemical Expression of Keratins in Normal Ovine Skin and in Chronic Dermatitis due to Sarcoptes scabiei

Hyperproliferation of epidermal keratinocytes is a major histopathological feature of chronic Sarcoptes scabiei dermatitis. We investigated the immunohistochemical expression of several keratins in scabietic dermatitis in sheep and in the skin of healthy sheep, using a panel of commercially available anti-human antibodies for keratins. Keratins AE1/AE3 and 34BE12 were expressed in all epithelial structures in healthy skin. Keratin MNF116 was expressed in the stratum basale and in the three lowest layers of the stratum spinosum, in follicular epithelium and in apocrine glands. Keratin K5/6 expression was seen in the stratum basale, in the two lowest cell layers of the stratum spinosum, in the outer root sheath of hair follicles and in myoepithelial cells of apocrine glands. K14 expression was observed in the stratum basale, in locally extensive regions of the two lowest cell layers of the stratum spinosum, in the outer root sheath of hair follicles and in sebaceous glands. Immunolabelling of K19 antigen was confined to apocrine glands. In scabietic skin, immunolabelling of keratin 34BE12 was seen in all layers of hyperplastic stratum spinosum and stratum granulosum but was restricted to some locally extensive regions in hyperkeratotic and parakeratotic stratum corneum. Keratin MNF116 was widely labelled in all layers of hyperplastic stratum spinosum and stratum granulosum. There was expansive labelling of K5/6 keratin in all layers of hyperplastic stratum spinosum and in locally extensive regions of stratum granulosum, as well as in hyperkeratotic or parakeratotic stratum corneum. Expansive labelling of K14 keratin was detected in all layers of hyperplastic stratum spinosum and in the layers of the hyperplastic stratum granulosum. K5/6 and K14 keratins were also labelled in the inner root sheath of occasional hair follicles.

The influence of clinical severity and topical antimicrobial treatment on bacteriological culture and the microbiota of equine pastern dermatitis

Background

Equine pastern dermatitis (EPD) is a common dermatological problem in horses, yet its aetiology and pathogenesis are poorly understood.

Objectives

This study aimed to investigate the effects of lesion severity and topical antimicrobial treatment on bacterial flora of EPD‐affected skin.

Animals

Sixteen horses with EPD were investigated.

Methods and materials

An observational study was conducted by assigning a clinical severity score ranging from 0 (macroscopically nonlesional) to 21 (severe), and sampling the most and least severely affected limbs of 16 horses (32 limbs) for bacteriological culture and 16S rRNA sequencing. Topical antimicrobial treatment in the month before sampling was recorded. The limbs were allocated to a nonlesional or mildly affected group (Group A, score 0–3) and a moderate to severely affected group (Group B, score 4–21).

Results

The most commonly cultured bacterial species was Staphylococcus aureus (one of 15 Group A versus nine of 17 Group B). Within Group B, S. aureus was found in three of six limbs treated with topical antimicrobials and in six of 11 untreated limbs. β‐haemolytic streptococci (three of 32) and Trueperella pyogenes (two of 32) also were cultured exclusively in the untreated limbs of Group B. Staphylococci and streptococci were found more often by 16S rRNA sequencing than in culture. Limbs with higher lesion severity and topical antimicrobial treatment appeared to have a lower alpha diversity and different beta diversity compared to milder and untreated lesions.

Conclusions and clinical importance

Observed differences in microbiota of equine skin are likely to be linked to the presence and severity of EPD and topical antimicrobial treatment. Further research is needed to establish causal bacteria.

Equine Hoof Canker: Bovine Papillomavirus Infection Is Not Associated With Impaired Keratinocyte Differentiation

Impaired keratinocyte differentiation has recently been suggested as a key event in equine hoof canker development. Koilocytotic appearance of keratinocytes, one of the most characteristic morphological alterations in hoof canker tissue, is also a common marker for papillomavirus (PV) infection, and bovine PV-1 and/or -2 (BPV-1/2) has previously been detected in equine canker patients. Therefore, the present study aimed to correlate the frequency and severity of koilocytotic keratinocytes with BPV detection in hoof canker samples. Hoof tissue of 5/18 canker-affected horses and 2/6 control horses tested positive for BPV-1/2 DNA using polymerase chain reaction. Thus, no association between the presence of BPV-1/2 papillomaviral DNA and koilocytotic appearance was found. Proteins associated with but not specific for PV infection were also investigated. Using immunohistochemistry, specific adhesion molecules (E-cadherin and β-catenin) and intermediate filaments (keratins 6 and 14) important for intact epidermal barrier function and keratinocyte differentiation were documented in control samples (n = 6) and in hoof canker tissue samples (n = 19). Altered expression patterns of intermediate filaments and adhesion molecules were demonstrated in canker tissue, confirming the importance of incomplete keratinocyte differentiation, as well as the crucial role of keratinocyte differentiation in hoof canker.

Chronic progressive lymphoedema in Friesian horses: suggestive phenotype of affected horses and genome-wide association study

BACKGROUND

Chronic progressive lymphoedema (CPL) is a disabling condition affecting various draft horse breeds, including Friesian horses.

HYPOTHESIS

The high incidence of CPL in Friesian horses suggests a genetic component and a predisposing phenotype.

ANIMALS

For the genomic study, 26 affected and 19 control horses were evaluated. Body measurements were taken from 28 affected and nine control Friesian horses.

METHODS AND MATERIALS

Axiom® Equine Genotyping Array with a total of 307,474 single nucleotide polymorphism (SNPs) was used for the case/control genome-wide association study (GWAS). Height, weight and leg measurements (seven different body measurements) were obtained and compared between groups.

RESULTS

No significant associations were identified with the GWAS. There were significant differences (P < 0.05) in gaskin length measurements between CPL-affected horses and controls.

CONCLUSION

The current study suggests that the potential genetic contribution to CPL in Friesian horses is complex and may include other SNP-associated factors. Significantly increased gaskin length of affected horses suggests a phenotype prone to developing CPL.

Morphological and immunohistochemical characteristics of the equine corneal epithelium

Objective

The morphology of the corneal epithelium in two age groups of horses is described. Distribution patterns of proliferation‐, differentiation‐, stem cell‐associated markers and cell junction proteins were assessed.

Methods

Corneal samples from 12 horses (six foals and six adult horses) were analyzed after H&E staining and immunohistochemistry using the following antibodies: E‐cadherin, β‐catenin, Connexin 43 (Cx43), tight junction protein 1 (TJP1), cytokeratin (CK) 14, CK 19, CK 3, CK 10, vimentin, Ki67, p63, nerve growth factor (NGF), ABCG2, and epithelial growth factor receptor. Semiquantitative analysis of crypt, limbal, peripheral, and central zone was performed. Semithin and ultrathin sections were used for ultrastructural evaluation of the epithelium.

Results

The height of the epithelium varied between age groups and crypts were consistently present. In the peripheral and central epithelium, three types of basal cells resembling a pseudostratified epithelium were characterized. Potential stem cell markers (CK 14, p63, NGF, and ABCG2) were present in all zones with decreasing frequency toward the center. Cornea‐specific differentiation marker CK 3 was not expressed in the most basal cell layer of the limbal epithelium. E‐cadherin, β‐catenin, and Cx43 revealed a similar apico‐lateral signal pattern throughout the entire epithelium; only TJP1 was additionally seen at the basal surface.

Conclusions

This study presents a systematic semiquantitative evaluation of the equine corneal epithelium, showing the presence of crypts as potential stem cell niche with CK 14, p63, NGF, and ABCG2 as relevant markers for cells with regenerative capacity. The pseudostratified arrangement of the basal layer was a unique finding.

Normal microscopic anatomy of equine body and limb skin: A morphological and immunohistochemical study

INTRODUCTION

Information on microscopic anatomy of equine skin is sparse. In horses, limb wounds often become chronic and/or non-healing whereas body wounds heal normally. These dissimilarities in healing patterns might be a product of different phenotypic characteristics of body and limb skin. The objective of this study was to investigate microscopic anatomy, epidermal thickness, keratinocyte proliferation and differentiation as well as the presence of mast cells in normal equine skin of body and limb.

MATERIALS AND METHODS

The study involved body and limb skin biopsies from six horses. Histological characteristics of the epidermis were assessed and epithelial thickness measured. Immunohistochemistry was performed to investigate epidermal differentiation patterns of cytokeratin (CK) 10, CK14, CK16, loricrin, and peroxisome proliferator-activated receptor alpha (PPAR-α), epidermal proliferation (Ki-67 immunostaining), and mast cells distribution in the skin.

RESULTS

The epidermis was significantly thicker in the limb skin compared to body skin (p<0.01). Epidermal proliferation and CK distribution did not show differences in the two anatomical areas. Loricrin presence was focally found in the spinous layer in four out of six limb skin samples but not in body skin samples. Tryptase positive mast cells were detected in the dermis and their density (cell/mm²) was not different between body and limb.

DISCUSSION AND CONCLUSION

Here we report for the first time about the normal distribution of CK10, CK14, CK16, PPAR-α, and loricrin in equine limb and body skin as well as about epidermal proliferation rate and mast cell count. It will be relevant to investigate the distribution of the investigated epithelial differentiation markers and the role of mast cells during equine wound healing and/or other skin diseases.

Expression and localization of epithelial stem cell and differentiation markers in equine skin, eye and hoof

BACKGROUND

The limited characterization of equine skin, eye and hoof epithelial stem cell (ESC) and differentiation markers impedes the investigation of the physiology and pathophysiology of these tissues.

HYPOTHESIS/OBJECTIVES

To characterize ESC and differentiation marker expression in epithelial tissues of the equine eye, haired skin and hoof capsule.

METHODS

Indirect immunofluorescence microscopy and immunoblotting were used to detect expression and tissue localization of keratin (K) isoforms K3, K10, K14 and K124, the transcription factor p63 (a marker of ESCs) and phosphorylated p63 [pp63; a marker of ESC transition to transit-amplifying (TA) cell] in epithelial tissues of the foot (haired skin, hoof coronet and hoof lamellae) and the eye (limbus and cornea).

RESULTS

Expression of K14 was restricted to the basal layer of epidermal lamellae and to basal and adjacent suprabasal layers of the haired skin, coronet and corneal limbus. Coronary and lamellar epidermis was negative for both K3 and K10, which were expressed in the cornea/limbus epithelium and haired skin epidermis, respectively. Variable expression of p63 with relatively low to high levels of phosphorylation was detected in individual basal and suprabasal cells of all epithelial tissues examined.

CONCLUSIONS

To the best of the author's knowledge, this is the first report of the characterization of tissue-specific keratin marker expression and the localization of putative epithelial progenitor cell populations, including ESCs (high p63 expression with low pp63 levels) and TA cells (high expression of both p63 and pp63), in the horse. These results will aid further investigation of epidermal and corneal epithelial biology and regenerative therapies in horses.

Localization of human mesenchymal stem cells from umbilical cord blood and their role in repair of diabetic foot ulcers in rats

The aim of this study is to explore the localization of human mesenchymal stem cells from umbilical cord matrix (hMSCs-UC) and the role of these cells in the repair of foot ulcerate tissue in diabetic foot ulcers in rats. A diabetic rat model was established by administering Streptozotocin. Diabetic foot ulceration was defined as non-healing or delayed-healing of empyrosis on the dorsal hind foot after 14 weeks. hMSCs-UC were delivered through the left femoral artery. We evaluated the localization of hMSCs-UC and their role in tissue repair in diabetic foot ulcers by histological analysis, PCR, and immunohistochemical staining. A model for diabetes was established in 54 out of 60 rats (90% success rate) and 27 of these rats were treated with hMSCs-UC. The area of ulceration was significantly and progressively reduced at 7 and 14 days following treatment with hMSCs-UC. This gross observation was strongly supported by the histological changes, including newly developed blood vessels and proliferation of inflammatory cells at 3 days post-treatment, significant increase in granulation tissue at 7 days post-treatment and squamous epithelium or stratified squamous epithelium at 14 days post-treatment. Importantly, human leukocyte antigen type-I (HLA-1) was confirmed in ulcerated tissue by RT-PCR. The expression of cytokeratin 19 was significantly increased in diabetic model rats, with no detectable change in cytokeratin 10. Additionally, both collagens I and III increased in model rats treated with hMSCs-UC, but the ratio of collagen I/III was less significant in treated rats compared with control rats. These results suggest that hMSCs-UC specifically localize to the target ulcerated tissue and may promote the epithelialization of ulcerated tissue by stimulating the release of cytokeratin 19 from keratinocytes and extracellular matrix formation.

CD3+ and BLA.36+ cells do not occur in the epidermis and adnexal epithelia of normal equine skin

Summary A small population of resident T lymphocytes is present in the healthy human and murine epidermis. However, resident epidermal lymphocytes have not been reported in normal skin of the horse. Skin biopsy specimens from the normal skin of 27 horses were examined histologically and immunohistochemically for the presence of lymphocytes, CD3+ cells and BLA.36+ cells in epidermis and adnexal epithelia. All examinations were negative. It appears that lymphocytes occur rarely, if at all, in the epidermis and adnexal epithelia of normal horse skin. Hence, the presence of lymphocytes in these structures should be considered abnormal.

Impaired synthesis of erythropoietin, glutamine synthetase and metallothionein in the skin of NOD/SCID/gamma(c)(null) and Foxn1 nu/nu mice with misbalanced production of MHC class II complex

Most skin pathologies are characterized by unbalanced synthesis of major histocompatability complex II (MHC-II) proteins. Healthy skin keratinocytes simultaneously produce large amounts of MHC-II and regeneration-supporting proteins, e.g. erythropoietin (EPO), EPO receptor (EPOR), glutamine synthetase (GS) and metallothionein (MT). To investigate the level of regeneration-supporting proteins in the skin during misbalanced production of MHC-II, skin sections from nonobese diabetic/severe combined immunodeficient (NOD/SCID)/gamma (c) (null) and or Foxn1 nu/nu mice which are a priory known to under- and over-express MHC II, respectively, were used. Double immunofluorescence analysis of NOD/SCID/gamma (c) (null) skin sections showed striking decrease in expression of MHC-II, EPO, GS and MT. In Foxn1 nu/nu mouse skin, GS was strongly expressed in epidermis and in hair follicles (HF), which lacked EPO. In nude mouse skin EPO and MHC-II were over-expressed in dermal fibroblasts and they were completely absent from cortex, channel, medulla and keratinocytes surrounding the HF, suggest a role for EPO in health and pathology of hair follicle. The level of expression of EPO and GS in both mutant mice was confirmed by results of Western blot analyses. Strong immunoresponsiveness of EPOR in the hair channels of NOD/SCID/gamma (c) (null) mouse skin suggests increased requirements of skin cells for EPO and possible benefits of exogenous EPO application during disorders of immune system accompanied by loss MHC-II in skin cells.

Molecular characterization of the equine ATP2A2 gene

The mammalian ATP2A2 gene encodes a P-type cation pump located in the sarcoplasmic or endoplasmic reticula of muscle cells. We isolated one bacterial artificial chromosome (BAC) clone containing the equine ATP2A2 gene and determined the complete coding sequence of this gene. Cloning and characterization of the equine ATP2A2 gene revealed that the equine ATP2A2 gene consists of 20 exons. In total, 32 horses out of 16 breeds were analyzed for single nucleotide polymorphisms (SNPs). A mutation scan for SNPs included ten exons and their flanking introns. We detected in total 17 SNPs, 14 of which were located in introns, one in exon 9 and two in exon 20. In this report we provide the genomic organization and the equine ATP2A2 coding sequence and an association analysis for chronic pastern dermatitis using a sample of South German draft horses.