Delayed cutaneous wound healing in aged rats compared to younger ones

Multifunctional Plasticized Hyaluronic-Acid-Based Nanogel Dressing for Accelerating Diabetic and Nondiabetic Wounds

Diabetic ulcers are associated with oxidative stress, inflammation, decreased synthesis of pro-healing mediators, and impaired vascularization, which convert the wound from acute to chronic and delay healing. An extended duration of wound healing raises the possibility of complications such as infection, sepsis, and even amputation. The objective of this study is the synthesis of a plasticized cross-linked hyaluronic acid (HA)-grafted poly(acrylamide-co-itaconic acid) nanogel as a nontoxic adhesive, swellable, antibacterial wound dressing with good mechanical properties to protect the wound from pathogens and accelerate the healing process, in addition to decreasing oxidative stress and inflammatory cytokines while increasing anti-inflammatory cytokines and angiogenesis. Nanogel H3 with a ratio (AM/IA) (3:1) showed excellent adhesion with good mechanical properties, biocompatibility, swelling, antioxidant, and antibacterial efficiencies. It showed great wound closure in vitro and in vivo with downregulation of inflammatory cytokines, upregulation of anti-inflammatory cytokines, and enhanced angiogenesis in vivo on diabetic and nondiabetic wounds.

The rat as an animal model in chronic wound research: An update

The increasing global prevalence of chronic wounds underscores the growing importance of developing effective animal models for their study. This review offers a critical evaluation of the strengths and limitations of rat models frequently employed in chronic wound research and proposes potential improvements. It explores these models in the context of key comorbidities, including diabetes, venous and arterial insufficiency, pressure-induced blood flow obstruction, and infections. Additionally, the review examines important wound factors including age, sex, smoking, and the impact of anesthetic and analgesic drugs, acknowledging their substantial effects on research outcomes. A thorough understanding of these variables is crucial for refining animal models and can provide valuable insights for future research endeavors.

Preparation and Characterization of Polycaprolactone (PCL) Antimicrobial Wound Dressing Loaded with Pomegranate Peel Extract

In recent years, medicinal plant extracts have received remarkable attention due to their wound-healing properties. In this study, polycaprolactone (PCL) electrospun nanofiber membranes incorporated with different concentrations of pomegranate peel extract (PPE) were prepared. The results of the SEM and FTIR experiments demonstrated that the morphology of nanofiber is smooth, fine, and bead-free, and the PPE was well introduced into the nanofiber membranes. Moreover, the outcomes of the mechanical property tests demonstrated that the nanofiber membrane made of PCL and loaded with PPE exhibited remarkable mechanical characteristics, indicating that it could fulfill the essential mechanical requisites for wound dressings. The findings of the in vitro drug release investigations indicated that PPE was instantly released within 20 h and subsequently released gradually over an extended period by the composite nanofiber membranes. Meanwhile, the DPPH radical scavenging test confirmed that the nanofiber membranes loaded with PPE exhibited significant antioxidant properties. Antimicrobial experiments showed higher PPE loading, and the nanofiber membranes showed higher antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans. The results of the cellular experiments showed that the composite nanofiber membranes were nontoxic and promoted the proliferation of L929 cells. In summary, electrospun nanofiber membranes loaded with PPE can be used as a wound dressing.

Age-Related Alterations in Macrophage Distribution and Function Are Associated With Delayed Cutaneous Wound Healing

Ageing-related delays and dysregulated inflammation in wound healing are well-documented in both human and animal models. However, cellular and molecular changes underlying this impairment in healing progression are not fully understood. In this study, we characterised ageing-associated changes to macrophages in wounds of young and aged mice and investigated transcriptomic differences that may impact the progression of wound healing. Full-thickness wounds created on the dorsum of C57BL/6J young and aged mice were excised on Days 3 and 7 post-wounding for analysis by immunohistochemistry, flow cytometry, and RNA sequencing. Our data revealed that macrophages were significantly reduced in aged wounds in comparison to young. Functional transcriptomic analyses showed that macrophages from aged wounds exhibited significantly reduced expression of cell cycle, DNA replication, and repair pathway genes. Furthermore, we uncovered an elevated pro-inflammatory gene expression program in the aged macrophages correlated with poor inflammation resolution and excessive tissue damage observed in aged wounds. Altogether, our work provides insights into how poorly healing aged wounds are phenotypically defined by the presence of macrophages with reduced proliferative capacity and an exacerbated inflammatory response, both of which are pathways that can be targeted to improve healing in the elderly.

Moringa oleifera Leaf Extract Promotes Healing of Infected Wounds in Diabetic Rats: Evidence of Antimicrobial, Antioxidant and Proliferative Properties

Moringa oleifera is known to possess wound healing activity. The present study evaluated the healing properties of methanolic extract of M. oleifera leaves in excision wounds infected with methicillin-resistant Staphylococcus aureus (MRSA) or P. aeruginosa in diabetic rats. An in vitro study was also carried out to determine the gene expression of VEGF and TGF-β1. Preliminary phytochemical and GC-MS analyses were carried out to determine different chemical constituents present in the extract. M. oleifera was applied locally as an ointment at two different concentrations. Wound contraction, period of epithelization, antioxidant enzyme activities and histological changes were determined. For the gene expression study, HaCaT cell lines were used. The formulation of M. oleifera extract improved wound contraction and decreased the period of epithelization, which was associated with an increase in antioxidant enzyme activities, epithelization, capillary density and collagen formation in MRSA-infected diabetic rats. However, this effect was reduced in diabetic animals infected with P. aeruginosa. An increase in the expression of VEGF and TGF-β1 was observed in HaCaT cell lines. M. oleifera extract promotes the healing of infected wounds in MRSA-infected diabetic rats but is less effective in the healing of wounds infected with P. aeruginosa in diabetic rats.

Supraphysiological testosterone supplementation improves granulation tissue maturation through angiogenesis in the early phase of a cutaneous wound healing model in rats

OBJECTIVE

The aim of this study was to evaluate the effects of both testosterone depletion and supraphysiological testosterone supplementation in the early phase of an animal cutaneous wound healing model in comparison with the physiological hormonal condition.

MATERIAL AND METHODS

Forty rats were distributed into the following four groups: Control, Orchiectomy (OCX), Durateston (Dura) and OCX+Dura. On day 1, the testicles were removed (OCX group) and the rats (Dura group) received a supraphysiological dose (250 mg/kg) of exogenous testosterone weekly. After 15 days a full-thickness excisional skin wound was created in all animals, which was healed by the second intention for 7 days. On day 22, the rats were euthanatized and the wounds were harvested for histopathological evaluation, immunohistochemistry analyses and multiplex immunoassay. One-way ANOVA and post-hoc Tukey tests were performed.

RESULTS

It was found that the supraphysiological testosterone level increased extracellular matrix deposition, promoted higher blood vessel formation and reduced wound contraction (p < 0.05). Additionally, it also stimulated PCNA-positive fibroblasts and KGF-positive cells (p < 0.05), while orchiectomy reduced the expression of IL-6 and TNF-α and increased VEGF and PDGF (p < 0.05) .

CONCLUSION

In conclusion, the results provide evidence that supraphysiological testosterone supplementation plays a positive role in the early phase of cutaneous wound healing, thus improving granulation tissue maturation through the enhancement of angiogenesis.

Evaluation the effect of testosterone on the number of endothelial progenitor cells and amount of SDF-1α, PDGF, bFGF, and NO

Background:

Recent therapeutic advances in cardiovascular disease, thanks to the discovery of endothelial progenitor cells (EPCs). Stromal cell-derived factor-1α (SDF-1α), platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), and nitric oxide (NO) play a role in migration, homing, and differentiation of EPCs into mature endothelial cells. The incidence of cardiovascular disease is higher in men than in women. This fact suggests the influence of sex hormones on incidence of cardiovascular disease.

Methods:

Twenty-four female wistar rats weighing 160–180 g were randomly divided into four groups (N = 6): 1. sham-treated by sesame oil, 2. ovariectomized (OVX)-treated by sesame oil, 3. OVX-treated by 10 μg/kg/day testosterone, and 4. OVX-treated by 100 μg/kg/day testosterone. After 21 days, the animals were euthanized and blood samples were saved for determination of EPC count and serum levels of SDF-1α, PDGF, bFGF, and NO production.

Results:

High-dose testosterone induced significant increase in EPC count in OVX rats (P < 0.05). Also 100 μg/kg/day testosterone increased serum level of SDF-1α more than OVX-treated by 10 μg/kg/day testosterone (P < 0.05). But 10 μg/kg/day testosterone increased significantly the serum level of PDGF >100 μg/kg/day testosterone-treated group (P < 0.05). The serum level of bFGF in sham-treated by sesame oil was equal with its concentration in OVX-treated by 100 μg/kg/day testosterone. And the serum concentration of NO production in testosterone-treated groups were significantly less than other groups (P < 0.05).

Conclusions:

This study suggests that testosterone might be effective on cardiovascular disease in females by increasing EPC count through SDF-1α and PDGF mechanisms which are some of the vascular healing factors.

Electrical stimulation shifts healing/scarring towards regeneration in a rat limb amputation model

Different species respond differently to severe injury, such as limb loss. In species that regenerate, limb loss is met with complete restoration of the limbs’ form and function, whereas in mammals the amputated limb’s stump heals and scars. In in vitro studies, electrical stimulation (EStim) has been shown to promote cell migration, and osteo- and chondrogenesis. In in vivo studies, after limb amputation, EStim causes significant new bone, cartilage and vessel growth. Here, in a rat model, the stumps of amputated rat limbs were exposed to EStim, and we measured extracellular matrix (ECM) deposition, macrophage distribution, cell proliferation and gene expression changes at early (3 and 7 days) and later stages (28 days). We found that EStim caused differences in ECM deposition, with less condensed collagen fibrils, and modified macrophage response by changing M1 to M2 macrophage ratio. The number of proliferating cells was increased in EStim treated stumps 7 days after amputation, and transcriptome data strongly supported our histological findings, with activated gene pathways known to play key roles in embryonic development and regeneration. In conclusion, our findings support the hypothesis that EStim shifts injury response from healing/scarring towards regeneration. A better understanding of if and how EStim controls these changes, could lead to strategies that replace scarring with regeneration.

Scarless wound healing: From development to senescence

An essential element of tissue homeostasis is the response to injuries, cutaneous wound healing being the most studied example. In the adults, wound healing aims at quickly restoring the barrier function of the skin, leading however to scar, a dysfunctional fibrotic tissue. On the other hand, in fetuses a scarless tissue regeneration takes place. During ageing, the wound healing capacity declines; however, in the absence of comorbidities a higher quality in tissue repair is observed. Senescent cells have been found to accumulate in chronic unhealed wounds, but more recent reports indicate that their transient presence may be beneficial for tissue repair. In this review data on skin wound healing and scarring are presented, covering the whole spectrum from early embryonic development to adulthood, and furthermore until ageing of the organism.

Photobiomodulation therapy action in wound repair skin induced in aged rats old: time course of biomarkers inflammatory and repair

Previous studies have discussed an inverse correlation between age and wound healing, because it relates to the association of aging with a gradual decrease in healing capacity. Treatment with photobiomodulation therapy (PBMT) improves wound healing by inducing increases in mitotic activity, numbers of fibroblasts, collagen synthesis, and neovascularization. Therefore, this study aimed to evaluate the effects of PBMT in cutaneous wound healing in aged rats. A punch biopsy of 8 mm in diameter was performed to produce a skin wound. The study included 45 male rats, of which 15 were young (30 days) and 30 were elderly (500 days). The 45 animals were distributed into 3 experimental groups, which were subjected to skin wounds and 1 aged group received PBMT, with a 30-mW laser beam (power density of 1.07 W/cm²), beam area of 0.028 cm², and λ660 nm produced through active phosphide Gallium-Aluminum-Indio (InGaAIP). The PBMT application took the form of a single-point transcutaneous method, with a total energy of 2 joules per wound site, energy density of 72 J/cm², and time of 1 min and 7 s. Analysis was performed to verify the effect of PBMT on the quantity of collagen I and III, metalloproteinase 3 and 9 (MMP-3 and MMP-9), tissue inhibitor of metalloproteinase-2 (TIMP-2) and of vascular endothelial growth factor (VEGF) at the wound site by immunohistochemistry, cytokine-induced neutrophil chemoattractant (CINC)-1, by enzyme-linked immunosorbent assay (ELISA) and interleukin (IL)-6 real-time polymerase chain reaction (RT-PCR). That we conclude LLLT is effective in the modulation of inflammatory mediators IL-6, CINC-1, VEGF, MMP-3, MMP-9 and TIMP-2 as well as increased collagen production in aged animals during different phases of the tissue regeneration process. However, the effects of PBMT obtained in the aged animals (aged LLLT group) suggest that new dosimetries should be tested to achieve better results.

Cutaneous wound healing in aging small mammals: a systematic review

As the elderly population grows, so do the clinical and socioeconomic burdens of nonhealing cutaneous wounds, the majority of which are seen among persons over 60 years of age. Human studies on how aging effects wound healing will always be the gold standard, but studies have ethical and practical hurdles. Choosing an animal model is dictated by costs and animal lifespan that preclude large animal use. Here, we review the current literature on how aging effects cutaneous wound healing in small animal models and, when possible, compare healing across studies. Using a literature search of MEDLINE/PubMed databases, studies were limited to those that utilized full-thickness wounds and compared the wound-healing parameters of wound closure, reepithelialization, granulation tissue fill, and tensile strength between young and aged cohorts. Overall, wound closure, reepithelialization, and granulation tissue fill were delayed or decreased with aging across different strains of mice and rats. Aging in mice was associated with lower tensile strength early in the wound healing process, but greater tensile strength later in the wound healing process. Similarly, aging in rats was associated with lower tensile strength early in the wound healing process, but no significant tensile strength difference between young and old rats later in healing wounds. From studies in New Zealand White rabbits, we found that reepithelialization and granulation tissue fill were delayed or decreased overall with aging. While similarities and differences in key wound healing parameters were noted between different strains and species, the comparability across the studies was highly questionable, highlighted by wide variability in experimental design and reporting. In future studies, standardized experimental design and reporting would help to establish comparable study groups, and advance the overall knowledge base, facilitating the translatability of animal data to the human clinical condition.

Cutaneous tissue damage induces long-lasting nociceptive sensitization and regulation of cellular stress- and nerve injury-associated genes in sensory neurons

Tissue damage is one of the major etiological factors in the emergence of chronic/persistent pain, although mechanisms remain enigmatic. Using incision of the back skin of adult rats as a model for tissue damage, we observed sensitization in a nociceptive reflex enduring to 28days post-incision (DPI). To determine if the enduring behavioral changes corresponded with a long-term impact of tissue damage on sensory neurons, we examined the temporal expression profile of injury-regulated genes and the electrophysiological properties of traced dorsal root ganglion (DRG) sensory neurons. The mRNA for the injury/stress-hub gene Activating Transcription Factor 3 (ATF3) was upregulated and peaked within 4 DPI, after which levels declined but remained significantly elevated out to 28 DPI, a time when the initial incision appears healed and tissue-inflammation largely resolved. Accordingly, stereological image analysis indicated that some neurons expressed ATF3 only transiently (mostly medium-large neurons), while in others it was sustained (mostly small neurons), suggesting cell-type-specific responses. In retrogradely-traced ATF3-expressing neurons, Calcium/calmodulin-dependent protein kinase type IV (CAMK4) protein levels and isolectin-B4 (IB4)-binding were suppressed whereas Growth Associated Protein-43 (GAP-43) and Neuropeptide Y (NPY) protein levels were enhanced. Electrophysiological recordings from DiI-traced sensory neurons 28 DPI showed a significant sensitization limited to ATF3-expressing neurons. Thus, ATF3 expression is revealed as a strong predictor of single cells displaying enduring pain-related electrophysiological properties. The cellular injury/stress response induced in sensory neurons by tissue damage and indicated by ATF3 expression is positioned to contribute to pain which can occur after tissue damage.

Reduced Ang2 expression in aging endothelial cells

Aging endothelial cells are characterized by increased cell size, reduced telomere length and increased expression of proinflammatory cytokines. In addition, we describe here that aging reduces the migratory distance of endothelial cells. Furthermore, we observe an increase of the quiescence protein Ang1 and a decrease of the endothelial activation protein Ang2 upon aging. Supplementing Ang2 to aged endothelial cells restored their migratory capacity. We conclude that aging shifts the balance of the Ang1/Ang2 network favouring a quiescent state. Activation of endothelial cells in aging might be necessary to enhance wound healing capacities.

5α-Dihydrotestosterone enhances wound healing in diabetic rats

Wound healing involves a complex interaction between the cells, extracellular matrix and oxidative response.

AIMS

Analyze the effects of 5α-Dihydrotestosterone (5α-DTH) ointment in cutaneous wound healing by secondary intention in diabetic Wistar rats.

MAIN METHODS

Rats (302.23±26.23g, n=48) were maintained in cages with food and water ad libitum in accordance with the Guiding Principles in the Use of Animal Ethics Committee. Diabetes was induced by intraperitoneal injection of streptozotocin (60mg/kg). Three skin wounds (12mm diameter) were created on the animals' back, which were randomized into 6 groups according to the application received: VT group: Vehicle (lanolin), SA group: 0.9% saline solution, NC group: Non-diabetic, CP group: positive control (silver sulfadiazine 0001%), T1 group: Testosterone (10%), T2 group: Testosterone (20%) emulsified in lanolin. The applications were made daily within 21days, and tissues from different wounds were removed every 7days.

KEY FINDINGS

Both groups treated with testosterone (T1 and T2) showed a significantly higher proportion of type I and type III collagen fibers. Superoxide dismutase levels were significantly higher on days 7 and 14 in testosterone treated groups. Protein carbonyls and MDA were lower in both groups.

SIGNIFICANCE

We conclude that groups treated with 5α-DTH showed a better healing pattern with complete wound closure, and proved to have a positive effect on the morphology of the scar tissue as well as an antioxidant stimulating effect during secondhand intention skin wounds repair in diabetic rats.

Glycation: the angiogenic paradox in aging and age-related disorders and diseases

Angiogenesis is generally a quiescent process which, however, may be modified by different physiological and pathological conditions. The "angiogenic paradox" has been described in diabetes because this disease impairs the angiogenic response in a manner that differs depending on the organs involved and disease evolution. Aging is also associated with pro- and antiangiogenic processes. Glycation, the post-translational modification of proteins, increases with aging and the progression of diabetes. The effect of glycation on angiogenesis depends on the type of glycated proteins and cells involved. This complex link could be responsible for the "angiogenic paradox" in aging and age-related disorders and diseases. Using diabetes as a model, the present work has attempted to review the age-related angiogenic paradox, in particular the effects of glycation on angiogenesis during aging.

Consequences of age on ischemic wound healing in rats: altered antioxidant activity and delayed wound closure

Advertisements targeted at the elderly population suggest that antioxidant therapy will reduce free radicals and promote wound healing, yet few scientific studies substantiate these claims. To better understand the potential utility of supplemental antioxidant therapy for wound healing, we tested the hypothesis that age and tissue ischemia alter the balance of endogenous antioxidant enzymes. Using a bipedicled skin flap model, ischemic and non-ischemic wounds were created on young and aged rats. Wound closure and the balance of the critical antioxidants superoxide dismutase and glutathione in the wound bed were determined. Ischemia delayed wound closure significantly more in aged rats. Lower superoxide dismutase 2 and glutathione in non-ischemic wounds of aged rats indicate a basal deficit due to age alone. Ischemic wounds from aged rats had lower superoxide dismutase 2 protein and activity initially, coupled with decreased ratios of reduced/oxidized glutathione and lower glutathione peroxidase activity. De novo glutathione synthesis, to restore redox balance in aged ischemic wounds, was initiated as evidenced by increased glutamate cysteine ligase. Results demonstrate deficiencies in two antioxidant pathways in aged rats that become exaggerated in ischemic tissue, culminating in profoundly impaired wound healing and prolonged inflammation.