Clinical and histological findings of cutaneous wound healing in the red-eared slider turtle (Trachemys scripta elegans) housed in unheated outdoor enclosures

A comprehensive exploration of diverse skin cell types in the limb of the desert tortoise (Testudo graeca) through light, transmission, scanning electron microscopy, and immunofluorescence techniques

The Greek tortoise, inhabiting harsh desert environments, provides a compelling case for investigating skin adaptations to extreme conditions. We have utilized light microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and immunofluorescence analysis to describe the structure of the arid-adapted limb skin in the Greek tortoise. Our aim was to identify the cell types that reflect the skin adaptation of this tortoise to arid conditions. Utilizing seven antibodies, we localized and elucidated the functions of various skin cells, shedding light on how the tortoise adapts to adverse environmental conditions. Our findings unveiled numerous scales on the limbs, varying in size and color, acting as protective armor against abrasions, bites, and other potential threats in their rocky habitats. The epidermis comprises four layers: stratum basalis, stratum spinosum, peri-corneous layer, and stratum corneum. Cytokeratin 14 (CK14) was explicitly detected in the basal layer of the epidermis, suggesting a role in maintaining epidermal integrity and cellular function. Langerhans cells were observed between epidermal cells filled with ribosomes and Birbeck granules. Numerous dendritic-shaped Langerhans cells revealed through E-Cadherin signify strong immunity in tortoises' skin. Melanophores were identified using the Melan-A antibody, labeling the cytoplasm, and the SOX10 antibody, labeling the nucleus, providing comprehensive insights into melanophores morphology and distribution. Two types of melanophores were found: dendritic below the stratum basalis of the epidermis and clustered oval melanophores in the deep dermal layer. Varied melanophores distribution resulted in a spotted skin pattern, potentially offering adaptive camouflage and protection against environmental challenges. Numerous myofibroblasts were discerned through alpha-smooth actin (α-SMA) expression, indicating that the Greek tortoise's skin possesses a robust tissue repair and remodeling capacity. B-cell lymphocytes detected via CD20 immunostaining exhibited sporadic distribution in the dermis, concentrating in lymphoid aggregates and around vessels, implying potential roles in local immune responses and inflammation modulation. Employing Tom20 to identify skin cells with abundant mitochondria revealed a notable presence in melanophores and the basal layer of the epidermis, suggesting high metabolic activity in these cell types and potentially influencing cellular functions. These findings contribute to our comprehension of tortoise skin anatomy and physiology, offering insights into the remarkable adaptations of this species finely tuned to their specific environmental habitats.

Reptilian Innate Immunology and Ecoimmunology: What Do We Know and Where Are We Going?

Reptiles, the only ectothermic amniotes, employ a wide variety of physiological adaptations to adjust to their environments but remain vastly understudied in the field of immunology and ecoimmunology in comparison to other vertebrate taxa. To address this knowledge gap, we assessed the current state of research on reptilian innate immunology by conducting an extensive literature search of peer-reviewed articles published across the four orders of Reptilia (Crocodilia, Testudines, Squamata, and Rhynchocephalia). Using our compiled dataset, we investigated common techniques, characterization of immune components, differences in findings and type of research among the four orders, and immune responses to ecological and life-history variables. We found that there are differences in the types of questions asked and approaches used for each of these reptilian orders. The different conceptual frameworks applied to each group has led to a lack of unified understanding of reptilian immunological strategies, which, in turn, have resulted in large conceptual gaps in the field of ecoimmunology as a whole. To apply ecoimmunological concepts and techniques most effectively to reptiles, we must combine traditional immunological studies with ecoimmunological studies to continue to identify, characterize, and describe the reptilian immune components and responses. This review highlights the advances and gaps that remain to help identify targeted and cohesive approaches for future research in reptilian ecoimmunological studies.

Effect of Canine Adipose Mesenchymal Stem Cell Secretome on a Model of Second-Intention Wound Healing in the Red-eared Slider Turtle (Trachemys scripta)

Mesenchymal stem cell (MSC) secretome refers to a variety of bioactive compounds that represents the more important pathway by which MSCs participate in tissue regeneration. Many of these compounds have shown variable functional activity even across nonmammalian vertebrate species, although MSCs in turtles have not yet been described. Canine adipose MSC secretome has been successfully used experimentally in skin healing. Our aim was to conduct a blinded controlled study to evaluate the effect of canine adipose MSC secretome (cS-MSC) as an alternative for the healing of soft skin, second intention wounds of red-eared slider turtles (Trachemys scripta). Under general anesthesia, one circular, 6-mm full thickness wound was made in each rear leg of 14 females. After randomization, cS-MSC was injected subcutaneously around one wound at days 1, 7, and 14, whereas the other wound acted as control. Biopsies from three animals' wounds were obtained at days 21, 28, 42, and 63. Differences in mean wound retraction at days 21 (n=14) and 28 (n=11) were statistically nonsignificant. The clinical and histopathologic scores performed blind by two different investigators were similar for treated and control wounds. In conclusion, we could not detect a significant functional activity of cS-MSC on wound healing of Trachemys scripta.

Regeneration in Reptiles Generally and the New Zealand Tuatara in Particular as a Model to Analyse Organ Regrowth in Amniotes: A Review

The ability to repair injuries among reptiles, i.e., ectothermic amniotes, is similar to that of mammals with some noteworthy exceptions. While large wounds in turtles and crocodilians are repaired through scarring, the reparative capacity involving the tail derives from a combined process of wound healing and somatic growth, the latter being continuous in reptiles. When the tail is injured in juvenile crocodilians, turtles and tortoises as well as the tuatara (Rhynchocephalia: Sphenodon punctatus, Gray 1842), the wound is repaired in these reptiles and some muscle and connective tissue and large amounts of cartilage are regenerated during normal growth. This process, here indicated as “regengrow”, can take years to produce tails with similar lengths of the originals and results in only apparently regenerated replacements. These new tails contain a cartilaginous axis and very small (turtle and crocodilians) to substantial (e.g., in tuatara) muscle mass, while most of the tail is formed by an irregular dense connective tissue containing numerous fat cells and sparse nerves. Tail regengrow in the tuatara is a long process that initially resembles that of lizards (the latter being part of the sister group Squamata within the Lepidosauria) with the formation of an axial ependymal tube isolated within a cartilaginous cylinder and surrounded by an irregular fat-rich connective tissue, some muscle bundles, and neogenic scales. Cell proliferation is active in the apical regenerative blastema, but much reduced cell proliferation continues in older regenerated tails, where it occurs mostly in the axial cartilage and scale epidermis of the new tail, but less commonly in the regenerated spinal cord, muscles, and connective tissues. The higher tissue regeneration of Sphenodon and other lepidosaurians provides useful information for attempts to improve organ regeneration in endothermic amniotes.

Effect of topical ozonated sunflower oil on second intention wound healing in turtles: a randomised experimental study

Background

Ozone is an antimicrobial agent that in experimental and case-control studies has been found to exert a positive effect on wound healing. Wild and pet chelonians frequently present insidious wounds exhibiting secondary infections and/or delayed healing.

Objectives

Evaluate the effects of topical ozonated sunflower oil on second-intention healing of acute experimental skin wounds in red-eared sliders (Trachemys scripta elegans).

Methods

Randomised within-subject controlled study; Group 1 (n = 24) was used to assess clinical healing features; Group 2 (n = 12) was used for histological evaluation in which two sets of wounds were biopsied at 2, 7, 14, 21, 28 and 42 days over the course of the cicatrisation process. A single 6 mm diameter wound was made on each rear limb and topical ozonated (950 peroxide value) and non-ozonated sunflower oil were applied daily for one week on treated and contralateral control wounds, respectively.

Results

Mean wound size was significantly lower in the ozone-treated group at day 28 (p < 0.0001) with differences of clinical relevance (74.04% vs. 93.05% reduction of initial wound size). Histologically, the acute inflammatory reaction was enhanced in treated wounds, with significantly higher numbers of heterophils (p = 0.0016), lymphocytes (p < 0.001) and fibroblasts (p < 0.001).

Conclusions

Daily topical application of ozonated sunflower oil over the course of one week improved the healing of acute, full-thickness skin wounds in chelonians. This clinical outcome was histologically correlated with an enhanced acute inflammatory reaction, as well as the production and remodelling of collagen fibres.

Tissue tolerance to cyanoacrylate adhesives for closure of surgical wounds in Trachemys scripta skin

BACKGROUND

The aim of this study was to evaluate the histological tolerance of medical cyanoacrylate adhesives (CAs), butyl-CA and octyl-CA, applied by two different methods in surgical skin incisions of T. scripta.

METHODS

A two-trial controlled blind study each one including 12 female adult T. scripta turtles. Two 1-cm long full-thickness surgical skin incisions were made on the dorsal aspect of each hind limb. In trial 1 CAs were applied superficially over the apposed wound edges; each animal's four wounds were closed using butyl-CA, octyl-CA and ethyl-CA or absorbable suture as controls. In trial 2 adhesives were applied holding wound edges everted, and octyl-CA was replaced by a non-sutured control wound. At each time point (2, 7, 14 and 21 days) all wounds from three randomly chosen animals were biopsied.

RESULTS

Medical grade CAs did not induce any sign of tissue damage and/or inflammatory reaction attributable to histotoxicity independently of the method of application. Wound dehiscence rate was higher when CAs were applied superficially over the apposed wound edges.

CONCLUSIONS

Octyl and butyl-CA are well tolerated by turtles' soft skin but because of their high rate of dehiscence they are not recommended in high tension wounds; use in low tension wounds needs further investigation.

Effects of topical insulin on second-intention wound healing in the red-eared slider turtle (Trachemys scripta elegans) - a controlled study

BACKGROUND

Compared with mammals, wound healing in reptiles is characterized by reduced wound contraction and longer healing times. The aim of this study is to describe the clinical and histopathological effects of topical insulin on second-intention healing of experimentally induced wounds in skin without dermal bony plates of Trachemys scripta elegans exposed to daily variations in ambient temperature and in an aquatic environment. Forty-four healthy adult females were assigned to two groups: Group 1 (n = 24) was used to assess clinical features such as wound contraction; Group 2 (n = 20) was used for histological evaluation and morphometric analysis. Topical porcine insulin (5 IU/ml diluted in glycerol) was applied daily 1 week. For each control time (2, 7, 14, 21 and 28 days post-wounding), re-epithelisation and wound remodelling were evaluated histologically and the number of main inflammatory cells (heterophils, macrophages, lymphocytes and fibroblasts) was scored.

RESULTS

Mean wound contraction was higher in the insulin-treated group at each time point and differences were significant at day 28 (P < 0.0001). Histologically, these clinical findings were associated with better re-epithelisation, inflammatory response, collagen synthesis and remodelling of the wounds. Morphometrically, insulin-treated wounds had significantly higher mean counts of heterophils (day 7), macrophages (days 2, 7 and 14) and fibroblasts (days 14 and 21), whereas lymphocyte counts were significantly lower at day 21. These results demonstrate that topical insulin modifies the inflammatory response of turtle skin up-regulating inflammatory cells at early stages and promoting wound healing.

CONCLUSIONS

Topical insulin is a potentially useful therapy in skin wounds of Trachemys scripta and should be evaluated in non-experimental wounds of turtles and other reptiles.