Equine lumican (LUM) cDNA sequence and spatio-temporal expression in an experimental model of normal and pathological wound healing

The granulation (t)issue: A narrative and scoping review of basic and clinical research of the equine distal limb exuberant wound healing disorder

Exuberant granulation tissue (EGT) is often observed during second intention wound healing in horses. Despite its impact on wound care, the basic mechanisms leading to EGT are still unclear and effective strategies to prevent and/or treat EGT are lacking. The development of EGT is a poorly understood, multifactorial process involving hyperproliferating fibroblasts and malfunctional differentiation of keratinocytes, suboptimal wound contraction, dysfunctional vascularisation, and chronic inflammation. To consolidate and describe basic and clinical research literature on EGT and to identify knowledge gaps and opportunities for future research, a search was systematically conducted using predefined search terms. Subsequently, a scoping review was conducted using specific criteria to select the peer-reviewed literature that described methods to treat and/or prevent EGT. Proposed mechanisms of effects as well as results and main conclusions were extracted and tabulated. The systematic search resulted in 1062 publications in PubMed and 767 in Web of Science. Twenty additional studies were later included. Of these, 327 studies were reviewed for the narrative review on basic research and 35 controlled clinical trials were eligible for the scoping review. All 35 studies were conducted in university hospitals, and all but one involved surgically induced non-infected wounds. The study population was predominantly horses (n = 230) with a small number of ponies (n = 18) and donkeys (n = 14). In conclusion, there remains a strong need for evidence-based recommendations on EGT treatment, preferably using multi-centre studies that represent the general population of horses, include higher numbers of animals, and are performed in naturally occurring wounds. This narrative and scoping review also emphasises the importance of incorporating basic research knowledge in the study design of clinical trials.

Absorbance or organization into ankylosis: a microarray analysis of haemarthrosis in a sheep model of temporomandibular joint trauma

Background

Traumatic haemarthrosis was hypothesized to be the etiology of temporomandibular (TMJ) ankylosis. Here, taking haematoma absorbance as a control, we aimed to reveal the molecular mechanisms involved in haematoma organizing into ankylosis using transcriptome microarray profiles.

Material/methods

Disk removal was performed to building haematoma absorbance (HA) in one side of TMJ, while removal of disk and articular fibrous layers was performed to induced TMJ ankylosis through haematoma organization (HO) in the contralateral side in a sheep model. Haematoma tissues harvested at days 1, 4 and 7 postoperatively were examined by histology, and analyzed by Affymetrix OviGene-1_0-ST microarrays. The DAVID were recruited to perform the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis for the different expression genes (DEGs). The DEGs were also typed into protein–protein interaction (PPI) networks to get the interaction data. Six significant genes screened from PPI analysis, were confirmed by real-time PCR.

Results

We found 268, 223 and 17 DEGs at least twofold at days 1, 4 and 7, respectively. At day 1, genes promoting collagen ossification (POSTN, BGN, LUM, SPARC), cell proliferation (TGF-β), and osteogenic differentiation of mesenchymal stem cells (BMP-2) were up-regulated in the HO side. At day 4, several genes involved in angiogenesis (KDR, FIT1, TEK) shower higher expression in the HO side. While HA was characterized by a continuous immune and inflammatory reaction.

Conclusions

Our results provide a comprehensive understanding of the role of haematoma in the onset and progress of TMJ ankylosis. The study will contribute to explaining why few injured TMJs ankylose and most do not from the molecular level.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-02033-w.

The Horse as a Model for the Study of Cutaneous Wound Healing

Significance: Cutaneous wounds are a major problem in both human and equine medicine. The economic cost of treating skin wounds and related complications in humans and horses is high, and in both species, particular types of chronic wounds do not respond well to current therapies, leading to suffering and morbidity. Recent Advances: Conventional methods for the treatment of cutaneous wounds are generic and have not changed significantly in decades. However, as more is learned about the mechanisms involved in normal skin wound healing, and how failure of these processes leads to chronic nonhealing wounds, novel therapies targeting the specific pathologies of hard-to-heal wounds are being developed and evaluated. Critical Issues: Physiologically relevant animal models are needed to (1) study the mechanisms involved in normal and impaired skin wound healing and (2) test newly developed therapies. Future Directions: Similarities in normal wound healing in humans and horses, and the natural development of distinct types of hard-to-heal chronic wounds in both species, make the horse a physiologically relevant model for the study of mechanisms involved in wound repair. Horses are also well-suited models to test novel therapies. In addition, studies in horses have the potential to benefit veterinary, as well as human medicine.

Time-dependent conformational analysis of ALK5-lumican complex in presence of graphene and graphene oxide employing molecular dynamics and MMPBSA calculation

Lumican, an extracellular matrix protein avails wound healing by binding to ALK5 membrane receptor (TGF-beta receptor I). Their interaction enables epithelialization and substantiates rejuvenation of injured tissue. To enrich permanence of ALK5-lumican interaction, we employed graphene and graphene oxide co-factors. Herein, this study explicates concomitancy of graphene and graphene oxide with ALK5-lumican. We performed an in silico approach involving molecular modelling, molecular docking, molecular dynamics for 200 ns, DSSP analysis and MMPBSA calculations. Results of molecular dynamics indicate cofactors influential in altering bioactive site of lumican than ALK5. Similarly, MMPBSA calculations unveiled binding energy of apoenzyme as -108.09 kcal/mol, holoenzyme (G) as -79.20 kcal/mol and holoenzyme (GO) as -114.33 kcal/mol. This concludes graphene oxide lucrative in enhancing binding energy of ALK5-lumican in holoenzyme (GO) via coil formation of Lum C₁₃ domain. In contrast, graphene reduced binding energy of ALK5-lumican in holoenzyme (G) modifying Lum C₁₃ into beta sheets. MMPBSA residual contribution analysis of Lum C₁₃ residues revealed binding energy of -13.9 kcal/mol for apoenzyme, -6.8 kcal/mol for holoenzyme (G) and -19.5 kcal/mol for holoenzyme (GO). This supports coil formation propitious for better ALK5-Lum interaction. Highest SASA energy of -21.05 kcal/mol of holoenzyme (G) assures graphene reasonable for improved ALK5-lumican hydrophobicity. As per the motive of the study, graphene oxide enriches permanence of ALK5-lumican. This provides counsel for plausible exploitation of lumican and graphene oxide as targeted/nano drug delivery system to reinstate acute wounds, chronic wounds, corneal wounds, hypertrophic scars and keloids in near future. Communicated by Ramaswamy H. Sarma.

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.

Lumican as a multivalent effector in wound healing

Wound healing, a complex physiological process, is responsible for tissue repair after exposure to destructive stimuli, without resulting in complete functional regeneration. Injuries can be stromal or epithelial, and most cases of wound repair have been studied in the skin and cornea. Lumican, a small leucine-rich proteoglycan, is expressed in the extracellular matrices of several tissues, such as the cornea, cartilage, and skin. This molecule has been shown to regulate collagen fibrillogenesis, keratinocyte phenotypes, and corneal transparency modulation. Lumican is also involved in the extravasation of inflammatory cells and angiogenesis, which are both critical in stromal wound healing. Lumican is the only member of the small leucine-rich proteoglycan family expressed by the epithelia during wound healing. This review summarizes the importance of lumican in wound healing and potential methods of lumican drug delivery to target wound repair are discussed. The involvement of lumican in corneal wound healing is described based on in vitro and in vivo models, with critical emphasis on its underlying mechanisms of action. Similarly, the expression and role of lumican in the healing of other tissues are presented, with emphasis on skin wound healing. Overall, lumican promotes normal wound repair and broadens new therapeutic perspectives for impaired wound healing.

Osteopontin expression in healing wounds of horses and in human keloids

REASONS FOR PERFORMING STUDY

Convincing evidence shows that persistent or excessive expression of osteopontin (OPN) is linked to fibroproliferation of various organs in laboratory animals and in man, such that its downregulation is a logical therapeutic objective.

OBJECTIVES

To investigate OPN expression in an equine model of wound healing and in clinical specimens of equine exuberant granulation tissue and human keloids in an effort to better understand the contribution of this protein to inflammation-associated skin fibrosis.

STUDY DESIGN

Description of gene and protein expression in an experimental equine model of wound healing and clinical specimens in horse and man.

METHODS

Osteopontin gene expression was evaluated by quantitative PCR, while protein expression was investigated by means of immunohistochemical staining.

RESULTS

Quantitative PCR showed that the OPN gene is expressed in normal intact skin of horses and continues to be expressed during the wound-healing process. An increase in gene expression was observed throughout the phases of wound healing, with a final decrease at wound closure. The protein was not detected in normal skin. Keratinocytes in wound-edge samples did not express the protein, whereas dermal immunoreactivity was confined to inflammatory cells. Healed wounds were devoid of staining. Equine exuberant granulation tissue showed immunoreactivity of the surrounding epidermis, infiltrating neutrophils, mononuclear cells, endothelial cells and fibroblasts. Human keloids showed OPN immunoreactivity throughout the epidermis as well as in mononuclear cells and scattered fibroblasts.

CONCLUSIONS

Immunohistochemical data show a different pattern of expression between normally healing and fibrotic wounds (exuberant granulation tissue and keloids), thus suggesting a role in fibroproliferation in horses and man.

Proteomic analysis of equine amniotic membrane: characterization of proteins

INTRODUCTION

Human amniotic membrane (AM) has been used as a biomaterial for surgical wound skin and ocular surface reconstruction for several years. Currently, equine AM has been used for corneal reconstruction in several animal species, and appears to have the same properties as human AM. Despite the observed positive healing abilities of this tissue in horses with ulcerative keratitis the proteins of equine AM have not been described.

OBJECTIVE

To identify proteins known to be associated with corneal healing from frozen equine AM.

PROCEDURES

Placentas were acquired from healthy live foal births from a local Thoroughbred breeding farm. The amnion was removed from the chorion by blunt dissection, washed with phosphate-buffered saline (PBS), and treated with 0.05% trypsin and 0.02% ethylene diaminetetraacetic acid in PBS. Amnion was attached to nitrocellulose paper (epithelial side up), and cut into 4 × 4 cm pieces. The sheets were frozen at -80 °C. The protein samples were solubilized, and analyzed by 2D gel electrophoresis and shotgun proteomics.

RESULTS

A reference identification map of the equine AM proteins was produced and 149 different proteins were identified. From gel-based proteomics, 49 spots were excised and 43 proteins identified by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Shotgun proteomics identified 116 proteins with an overlap of 10 proteins in both analyses.

CONCLUSIONS

We have described a reference map for equine AM proteins that may provide a background to explain the positive results found in horses with ulcerative keratopathies using this biomaterial.

Morphometric Evaluation of Interrenal Gland and Kidney Macrophages Aggregates in Normal Healthy Rainbow Trout (Oncorhynchus mykiss) and after Bacterial Challenge with Yersinia ruckeri

Macrophage aggregates (MA) occur in various organs of fish as discrete aggregations of pigmented macrophages. The study presented herein investigates the quantitative modifications from normal anatomical condition, of interrenal gland (IG) and kidney MA in six treatment groups of adult rainbow trout submitted to either specific or aspecific immune stimulation and subsequently challenged with Yersinia ruckeri. Routinely stained tissue sections from both IG and kidney were analysed. The percentage of tissues occupied by MA and the MA density (number/mm²) were calculated on at least 10 randomly selected nonoverlapping fields taken from each tissue section. MA morphometric findings from challenged fish were compared to those from a control group. Results showed that fish from control group displayed a statistically significant (P < 0.05) higher percentage of tissue occupied by MA and MA density. Among different treatment groups, anti-Yersinia ruckeri immunized fish, which did not show clinical signs of disease after bacterial challenge, displayed higher values of morphometric parameters compared with symptomatic fish from other groups. Our study demonstrates that the quantification of the area occupied by MA might be an efficient parameter to evaluate the general condition of a salmonid population since it positively correlates with the health status and negatively with stress factor such as the acute bacterial infection.

Aberrant wound healing in the horse: naturally occurring conditions reminiscent of those observed in man

Impaired wound healing represents an enormous clinical and financial problem for companion animals and humans alike. Unfortunately, most models used to study healing rely on rodents, which have significant differences in the healing and scarring process and rarely develop complications. In order to better simulate impaired healing, the model should strive to reproduce the natural processes of healing and delayed healing. Wounds on the limbs of horses display similarities to wounds in humans in their epithelialization/contraction ratio, genetic influence as well as dysregulated cytokine profile and the spontaneous development of fibroproliferative disorders. Veterinarians have access to advanced wound therapies that are often identical to those provided to human patients. Wound research in large animals has resulted in new wound models as well as a better understanding of the physiology, immunology, and local environmental impact on both normal and aberrant wound healing. One such model reproduces the naturally occurring fibroproliferative disorder of horses known as exuberant granulation tissue. Comparisons between the normally healing and impaired wounds provide insight into the repair process and can facilitate product development. A better understanding of the wound healing physiopathology based on clinically accurate animal models should lead to the development of novel therapies thereby improving outcomes in both human and veterinary patients.

Lumican is a major small leucine-rich proteoglycan (SLRP) in Atlantic cod (Gadus morhua L.) skeletal muscle

Knowledge on fish matrix biology is important to ensure optimal fish -quality, -growth and -health in aquaculture. The aquaculture industry face major challenges related to matrix biology, such as inflammations and malformations. Atlantic cod skeletal muscle was investigated for collagen I, decorin, biglycan, and lumican expression and distribution by real-time PCR, immunohistochemical staining and Western blotting. Immunohistochemical staining and Western immunoblotting were also performed using antibodies against glycosaminoglycan side chains of these proteoglycans, in addition to fibromodulin. Real-time PCR showed highest mRNA expression of lumican and collagen I. Collagen I and proteoglycan immunohistochemical staining revealed distinct thread-like structures in the myocommata, with the exception of fibromodulin, which stained in dense structures embedded in the myocommata. Chondroitinase AC-generated epitopes stained more limited than cABC-generated epitopes, indicating a stronger presence of dermatan sulfate than chondroitin sulfate in cod muscle. Lumican and keratan sulfate distribution patterns were strong and ubiquitous in endomysia and myocommata. Western blots revealed similar SLRPs sizes in cod as are known from mammals. Staining of chondroitin/dermatan sulfate epitopes in Western blots were similar in molecular size to those of decorin and biglycan, whereas staining of keratan sulfate epitopes coincided with expected molecular sizes of lumican and fibromodulin. In conclusion, lumican was a major proteoglycan in cod muscle with ubiquitous distribution overlapping with keratan sulfate. Other leucine-rich proteoglycans were also present in cod muscle, and Western blot using antibodies developed for mammalian species showed cross reactivity with fish, demonstrating similar structures and molecular weights as in mammals.