Role of umbilical cord mesenchymal stromal cells in skin rejuvenation

Aging is the main cause of many degenerative diseases. The skin is the largest and the most intuitive organ that reflects the aging of the body. Under the interaction of endogenous and exogenous factors, there are cumulative changes in the structure, function, and appearance of the skin, which are characterized by decreased synthesis of collagen and elastin, increased wrinkles, relaxation, pigmentation, and other aging characteristics. skin aging is inevitable, but it can be delayed. The successful isolation of mesenchymal stromal cells (MSC) in 1991 has greatly promoted the progress of cell therapy in human diseases. The International Society for Cellular Therapy (ISCT) points out that the MSC is a kind of pluripotent progenitor cells that have self-renewal ability (limited) in vitro and the potential for mesenchymal cell differentiation. This review mainly introduces the role of perinatal umbilical cord-derived MSC(UC-MSC) in the field of skin rejuvenation. An in-depth and systematic understanding of the mechanism of UC-MSCs against skin aging is of great significance for the early realization of the clinical transformation of UC-MSCs. This paper summarized the characteristics of skin aging and summarized the mechanism of UC-MSCs in skin rejuvenation reported in recent years. In order to provide a reference for further research of UC-MSCs to delay skin aging.

Stem Cell-Based Tissue Engineering Approaches for Diabetic Foot Ulcer: a Review from Mechanism to Clinical Trial

Diabetic foot ulcer (DFU) is a complication from incomplete or prolonged wound healing, at times requires amputation, putting substantial health and socioeconomic burden. Wound healing is a dynamic overlapping process that can be regulated by arrays of molecular factors showing redundancy in function. However, dysregulation in the mechanism of angiogenesis, extra cellular matrix (ECM) formation and immune modulation are the major causes for impair wound healing in hyperglycaemic patients. Despite development of wound care research, there is a lack of well-accepted targeted therapy with multidisciplinary approach for DFU treatment. Stem cell therapy holds a promising outcome both in preclinical and clinical trials because of its ability to promote healing via regeneration and specialized tissue differentiation. Among different types of stem cells, regenerative potential of mesenchymal stem cell (MSC) is well demonstrated in both experimental and clinical trial. Still there is a huge knowledge gap among medical practitioners for deciding the best stem cell source, administration route, and safety. This review strengthens the fact that why stem cell therapy is a promising candidate to treat DFU and cited multiple tissue engineering and biomaterial-based approaches for delivering stem cells and their aftermath paracrine events. Based on the pre-clinical and clinical studies, the review tried to come up with optimum stem cell source and delivery route for the treatment of DFU. At last, the review glances on possible direction to enhance therapeutics strategy for the same, including different approaches like: phytocompounds, exosomes, scaffold geometry, cell preconditioning and licensing etc.

On the Potential Role of the Antioxidant Couple Vitamin E/Selenium Taken by the Oral Route in Skin and Hair Health

The relationship between oxidative stress and skin aging/disorders is well established. Many topical and oral antioxidants (vitamins C and E, carotenoids, polyphenols) have been proposed to protect the skin against the deleterious effect induced by increased reactive oxygen species production, particularly in the context of sun exposure. In this review, we focused on the combination of vitamin E and selenium taken in supplements since both molecules act in synergy either by non-enzymatic and enzymatic pathways to eliminate skin lipids peroxides, which are strongly implicated in skin and hair disorders.

S, Shetty P, Prakash Patil. Molecular signatures in diabetic foot ulcer by integrated gene expression profiling via bioinformatics analysis

Introduction and Aim: Diabetic foot ulcers (DFUs) are a common and debilitating diabetic consequence leading to lower-limb amputations, long-term disability, and reduced lifespan. There is a lack of clinical diagnosis expertise because of no adequate diagnostic signs for DFU. As a result, the current research aims to find out how differently expressed genes (DEGs) affect the DFU. Materials and Methods: Bioinformatics analysis was used to evaluate DEGs using the GSE132187 dataset of the NCBI-GEO database, which contained samples from three hyperglycemic and three normoglycemic macrophage-like cell lines. Following the discovery of DEGs, Gene Ontology (GO) and KEGG pathway enrichment analysis were used to investigate how genes are classified into preset bins based on their functional properties. To discover hub DEGs in DFU, a protein-protein interaction (PPI) network was built and five topological parameters such as degree, stress, Closeness centrality, betweenness centrality, and radiality were evaluated. Results: We found 547 DEGs using the GSE132187 dataset, comprising 79 upregulated DEGs and 468 downregulated DEGs. There were 434 nodes and 1724 edges in the PPI network. The giant network uncovered six modules that are significantly enriched in biological processes like positive JNK cascade regulation, positive interferon-gamma production regulation, negative cell proliferation regulation, cellular response to zinc ion, cellular response to lipopolysaccharide, wound healing, and inflammatory response. Conclusion: Bioinformatics analysis revealed the major differentially expressed hub-genes implicated in DFUs. These findings suggested that these genes could be used as a DFU prognostic, diagnostic, or therapeutic targets.

Phenomenological-based model of glucose transport from liver to abdominal subcutaneous adipose tissue

BACKGROUND

A good treatment for type 1 diabetes mellitus (T1DM) requires accurate measurements of blood glucose levels. Continuous glucose monitors (CGM) measure the glucose concentration in the interstitial fluid of the abdominal subcutaneous adipose tissue. However, glucose measured in the abdominal interstitial fluid does not represent blood glucose concentrations accurately due to the complex blood transport through the body and glucose diffusion in interstitial fluid.

METHODS

To gain insight into this problem, a phenomenological-based semiphysical model (PBSM) of glucose transport by volumetric flow and diffusion from the bloodstream to interstitial fluid was constructed. A published 10-step modeling procedure was used to obtain a model for glucose transport time through the blood vessels and from the blood capillaries to the interstitial fluid, glucose diffusion within the interstitial fluid, and glucose diffusion through the semipermeable coating of the sensor needle. For this model, a healthy person is considered at rest with average parameters.

RESULTS

The simulations performed using the PBSM allow obtaining the glucose transport time from the liver to the sensor needle. In this way, it is possible to reconstruct an accurate dynamic measurement of blood glucose from the measurements in the interstitial fluid of the abdominal subcutaneous adipose tissue.

CONCLUSIONS

PBSMs with parameters interpretability illustrate the connection of glucose concentrations in the interstitial fluid with that currently in the blood. Implementing this model in a CGM will result in more reliable measurements of blood glucose levels for T1DM treatment.

m6A reader YTHDC1 modulates autophagy by targeting SQSTM1 in diabetic skin

Dysregulation of macroautophagy/autophagy contributes to the delay of wound healing in diabetic skin. N⁶-methyladenosine (m⁶A) RNA modification is known to play a critical role in regulating autophagy. In this study, it was found that SQSTM1/p62 (sequestosome 1), an autophagy receptor, was significantly downregulated in two human keratinocyte cells lines with short-term high-glucose treatment, as well as in the epidermis of diabetic patients and a db/db mouse model with long-term hyperglycemia. Knockdown of SQSTM1 led to the impairment of autophagic flux, which was consistent with the results of high-glucose treatment in keratinocytes. Moreover, the m⁶A reader protein YTHDC1 (YTH domain containing 1), which interacted with SQSTM1 mRNA, was downregulated in keratinocytes under both the acute and chronic effects of hyperglycemia. Knockdown of YTHDC1 affected biological functions of keratinocytes, which included increased apoptosis rates and impaired wound-healing capacity. In addition, knockdown of endogenous YTHDC1 resulted in a blockade of autophagic flux in keratinocytes, while overexpression of YTHDC1 rescued the blockade of autophagic flux induced by high glucose. In vivo, knockdown of endogenous Ythdc1 or Sqstm1 inhibited autophagy in the epidermis and delayed wound healing. Interestingly, we found that a decrease of YTHDC1 drove SQSTM1 mRNA degradation in the nucleus. Furthermore, the results revealed that YTHDC1 interacted and cooperated with ELAVL1/HuR (ELAV like RNA binding protein 1) in modulating the expression of SQSTM1. Collectively, this study uncovered a previously unrecognized function for YTHDC1 in modulating autophagy via regulating the stability of SQSTM1 nuclear mRNA in diabetic keratinocytes.

Abbreviations: ACTB: actin beta; AGEs: glycation end products; AL: autolysosome; AP: autophagosome; ATG: autophagy related; AKT: AKT serine/threonine kinase; ANOVA: analysis of variance; BECN1: beclin 1; Co-IP: co-immunoprecipitation; DEGs: differentially expressed genes; DM: diabetes mellitus; ELAVL1: ELAV like RNA binding protein 1; FTO: FTO alpha-ketoglutarate dependent dioxygenase; G: glucose; HaCaT: human keratinocyte; GO: Gene Ontology; GSEA: Gene Set Enrichment Analysis; HE: hematoxylin-eosin; IHC: immunohistochemical; IRS: immunoreactive score; KEAP1: kelch like ECH associated protein 1; KEGG: Kyoto Encyclopedia of Genes and Genomes; m⁶A: N⁶-methyladenosine; M: mannitol; MANOVA: multivariate analysis of variance; MAP1LC3: microtubule associated protein 1 light chain 3; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; MeRIP: methylated RNA immunoprecipitation; METTL3: methyltransferase 3, N6-adenosine-methytransferase complex catalytic subunit; MTOR: mechanistic target of rapamycin kinase; MTORC1: mechanistic target of rapamycin complex 1; NBR1: NBR1 autophagy cargo receptor; NFE2L2: nuclear factor, erythroid 2 like 2; NG: normal glucose; NHEK: normal human epithelial keratinocyte; OE: overexpressing; p-: phospho-; PI: propidium iodide; PPIN: Protein-Protein Interaction Network; RBPs: RNA binding proteins; RIP: RNA immunoprecipitation; RNA-seq: RNA-sequence; RNU6–1: RNA, U6 small nuclear 1; ROS: reactive oxygen species; siRNAs: small interfering RNAs; SQSTM1: sequestosome 1; SRSF: serine and arginine rich splicing factor; T2DM: type 2 diabetes mellitus; TEM: transmission electron microscopy; TUBB: tubulin beta class I; WT: wild-type; YTHDC1: YTH domain containing 1.

A review of diabetic wound models-Novel insights into diabetic foot ulcer

Diabetic foot ulcer (DFU) is a major debilitating complication of diabetes. Many research investigations have been conducted with the aims to uncover the diabetic wound healing mechanisms, develop novel therapeutics, and screen bioactive wound dressings in order to improve the current management of DFU. These would have not been possible without the utilization of an appropriate wound model, especially in a diabetic wound context. This review focuses on the different in vitro research models used in DFU investigations such as the 2D scratch wound assay, 3D skin model, and 3D angiogenesis model as well as their limitations. The current efforts and challenges to apply the 2D and 3D in vitro models in a hyperglycemic context to provide insights into DFU modeling will be reviewed. Perspectives of utilizing 3D bioprinting and skin-on-the-chip model as a diabetic wound model in the future will also be highlighted. By leveraging knowledge from past experiences and current research, an improved experimental model for DFU is anticipated to be established in near future.

Updates in Diabetic Wound Healing, Inflammation, and Scarring

Diabetic patients can sustain wounds either as a sequelae of their disease process or postoperatively. Wound healing is a complex process that proceeds through phases of inflammation, proliferation, and remodeling. Diabetes results in several pathological changes that impair almost all of these healing processes. Diabetic wounds are often characterized by excessive inflammation and reduced angiogenesis. Due to these changes, diabetic patients are at a higher risk for postoperative wound healing complications. There is significant evidence in the literature that diabetic patients are at a higher risk for increased wound infections, wound dehiscence, and pathological scarring. Factors such as nutritional status and glycemic control also significantly influence diabetic wound outcomes. There are a variety of treatments available for addressing diabetic wounds.

Diabetes and acute bacterial skin and skin structure infections

Acute bacterial skin and skin structures infections (ABSSSIs) are associated with high morbidity, costs and mortality in patients with diabetes mellitus. Their appropriate management should include several figures and a well-organized approach. This review aims to highlight the interplay between diabetes and ABSSSIs and bring out the unmet clinical needs in this area. Pathogenetic mechanisms underlying the increased risk of ABSSSIs in diabetes mellitus are multifactorial: high glucose levels play a crucial pathogenetic role in the tissue damage and delayed clinical cure. Moreover, the presence of diabetes complications (neuropathy, vasculopathy) further complicates the management of ABSSSIs in patients with diabetes. Multidrug resistance organisms should be considered in this population based on patient risk factors and local epidemiology and etiological diagnosis should be obtained whenever possible. Moreover, drug-drug interactions and drug-related adverse events (such as nephrotoxicity) should be considered in the choice of antibiotic therapy. Reducing unnecessary hospitalizations and prolonged length of hospital stay is of primary importance now, more than ever. To achieve these objectives, a better knowledge of the interplay between acute and chronic hyperglycemia, multidrug resistant etiology, and short and long-term outcome is needed. Of importance, a multidisciplinary approach is crucial to achieve full recovery of these patients.

Fibroblast Growth Factor in Diabetic Foot Ulcer: Progress and Therapeutic Prospects

Diabetic foot ulcer (DFU) is a combination of neuropathy and various degrees of peripheral vasculopathy in diabetic patients resulting in lower extremity infection, ulcer formation, and deep-tissue necrosis. The difficulty of wound healing in diabetic patients is caused by a high glucose environment and various biological factors in the patient. The patients' skin local microenvironment changes and immune chemotactic response dysfunction. Wounds are easy to be damaged and ulcerated repeatedly, but difficult to heal, and eventually develop into chronic ulcers. DFU is a complex biological process in which many cells interact with each other. A variety of growth factors released from wounds are necessary for coordination and promotion of healing. Fibroblast growth factor (FGF) is a family of cell signaling proteins, which can mediate various processes such as angiogenesis, wound healing, metabolic regulation and embryonic development through its specific receptors. FGF can stimulate angiogenesis and proliferation of fibroblasts, and it is a powerful angiogenesis factor. Twenty-three subtypes have been identified and divided into seven subfamilies. Traditional treatments for DFU can only remove necrotic tissue, delay disease progression, and have a limited ability to repair wounds. In recent years, with the increasing understanding of the function of FGF, more and more researchers have been applying FGF-1, FGF-2, FGF-4, FGF-7, FGF-21 and FGF-23 topically to DFU with good therapeutic effects. This review elaborates on the recently developed FGF family members, outlining their mechanisms of action, and describing their potential therapeutics in DFU.

HuskinDB, a database for skin permeation of xenobiotics

Skin permeation is an essential biological property of small organic compounds our body is exposed to, such as drugs in topic formulations, cosmetics, and environmental toxins. Despite the limited availability of experimental data, there is a lack of systematic analysis and structure. We present a novel resource on skin permeation data that collects all measurements available in the literature and systematically structures experimental conditions. Besides the skin permeation value k_p, it includes experimental protocols such as skin source site, skin layer used, preparation technique, storage conditions, as well as test conditions such as temperature, pH as well as the type of donor and acceptor solution. It is important to include these parameters in the assessment of the skin permeation data. In addition, we provide an analysis of physicochemical properties and chemical space coverage, laying the basis for applicability domain determination of insights drawn from the collected data points. The database is freely accessible under https://huskindb.drug-design.de or https://doi.org/10.7303/syn21998881 .

The link between advanced glycation end products and apoptosis in delayed wound healing

Advanced glycation end products (AGEs) are naturally occurring molecules that start to accumulate from embryonic developmental stages and form as part of normal ageing. When reducing sugars interact with and modify proteins or lipids, AGE production occurs. AGE formation accelerates in chronic hyperglycemic conditions, and high AGE levels have been associated with the pathogenesis of various diseases. In addition, enhanced levels of AGEs have been linked to delayed wound healing as seen in patients with diabetes mellitus. Research has provided numerous ways in which a high AGE concentration results in impaired wound healing, including oxidative stress, structural and functional changes to proteins important in wound repair, an enhanced inflammatory response by activation of transcription factors, and possible exaggerated apoptosis of cells necessary to the wound repair process. Apoptosis is a naturally occurring cell death process that is significant for normal tissue functioning and plays an important role in wound repair by preventing a prolonged inflammatory response and excessive scar formation. Abnormal apoptosis affects wound healing, resulting in slow healing wounds. This review will summarize the role of AGEs in wound healing, focusing on the mechanisms by which AGEs lead to apoptosis in various cell types. The review provides the way forward for medical research and molecular studies as it focuses on the mechanisms by which AGEs induce apoptosis in various cell types, including fibroblasts, osteoblasts, neuronal cells, and endothelial cells. Reviewing the mechanisms of AGE-linked apoptosis is important in understanding the impact of high AGE levels in delayed wound healing in diabetic patients due to abnormal apoptosis of cells necessary to the wound healing process.

Following-up skin penetration of lidocaine from different vehicles by Raman spectroscopic mapping

The application of local anesthetics, usually administered by subcutaneous injection, is common in the course of diagnostic, therapeutic, and cosmetic dermatology procedures. The effective dermal delivery of lidocaine could offer a solution to many adverse effects caused by needle insertion, such as pain, local reactions or toxicity, and additionally, it avoids the disruption of anatomical landmarks. Therefore, novel dermal formulations of local anesthetics are needed to overcome the barrier function of the skin and provide sufficient and prolonged anesthesia. In our study, we aimed to investigate and compare the penetration profiles of four different lidocaine containing formulations (hydrogel, oleogel, lyotropic liquid crystal and nanostructured lipid carrier) by Raman microscopic mapping of the drug. The application of Raman spectroscopy provided information about the spatial distribution of lidocaine in the skin ex vivo. The penetration of lidocaine from lyotropic liquid crystal and nanostructured carrier reached deeper skin layers and a higher amount of the drug was diffused into the skin, compared with hydrogel and oleogel. This study confirmed that nanostructured carriers can improve skin penetration properties of lidocaine and proved the applicability of Raman spectroscopy in the research of dermatological preparations ex vivo as a nondestructive, relatively easy and fast technique.

Redox Signaling in Diabetic Wound Healing Regulates Extracellular Matrix Deposition

SIGNIFICANCE

Impaired wound healing is a major complication of diabetes, and can lead to development of chronic foot ulcers in a significant number of patients. Despite the danger posed by poor healing, very few specific therapies exist, leaving patients at risk of hospitalization, amputation, and further decline in overall health. Recent Advances: Redox signaling is a key regulator of wound healing, especially through its influence on the extracellular matrix (ECM). Normal redox signaling is disrupted in diabetes leading to several pathological mechanisms that alter the balance between reactive oxygen species (ROS) generation and scavenging. Importantly, pathological oxidative stress can alter ECM structure and function.

CRITICAL ISSUES

There is limited understanding of the specific role of altered redox signaling in the diabetic wound, although there is evidence that ROS are involved in the underlying pathology.

FUTURE DIRECTIONS

Preclinical studies of antioxidant-based therapies for diabetic wound healing have yielded promising results. Redox-based therapeutics constitute a novel approach for the treatment of wounds in diabetes patients that deserve further investigation. Antioxid. Redox Signal. 27, 823-838.

Reactive Oxygen Species and NOX Enzymes Are Emerging as Key Players in Cutaneous Wound Repair

Our understanding of the role of oxygen in cell physiology has evolved from its long-recognized importance as an essential factor in oxidative metabolism to its recognition as an important player in cell signaling. With regard to the latter, oxygen is needed for the generation of reactive oxygen species (ROS), which regulate a number of different cellular functions including differentiation, proliferation, apoptosis, migration, and contraction. Data specifically concerning the role of ROS-dependent signaling in cutaneous wound repair are very limited, especially regarding wound contraction. In this review we provide an overview of the current literature on the role of molecular and reactive oxygen in the physiology of wound repair as well as in the pathophysiology and therapy of chronic wounds, especially under ischemic and hyperglycemic conditions.

MicroRNA-155 Inhibition Promoted Wound Healing in Diabetic Rats

Diabetes leads to amputation in approximately 15% to 20% of patients and is associated with high morbidity and mortality. Thus, improving the quality of wound healing in this condition is essential. Diabetes is associated with acute/chronic inflammation affecting all organs especially the foot, while, inhibition of microRNA-155 (miR-155) has been reported to improve or reduce inflammatory situation. However, the role of miR-155 inhibition in promoting diabetic wound healing is not clear. To further study the potential benefit of miR-155 inhibition, a study of male Sprague-Dawley rats was conducted and diabetes was induced by injection of streptozotocin. Real-time polymerase chain reaction (PCR), hematoxylin and eosin staining and immunohistochemistry were then performed. The PCR results confirmed that miR-155 expression was lower after miR-155 inhibition on days 3, 7, and 13 (all Ps <.05). The wound healing rate between the normal glucose group (N group), diabetic PBS group (PBS group) and the topical miR-155 inhibitor group was compared. Faster healing of cutaneous wounds was observed in the miR-155 inhibitor group than in the PBS group and normal glucose group ( P < .05). In addition, downregulation of inflammatory cells, including neutrophils (MPO-positive) and macrophages (CD68-positive), and upregulation of the angiogenic protein CD31 and markers indicative of fibroblast proliferation and collagen deposition, such as collagen 1, TGF-β1, and α-SMA, were observed. These data permit the observation that miR-155 inhibition possesses the potential to reduce inflammation in acute wounds. This property may benefit the healing of diabetic foot wounds.

Clinical application prospect of umbilical cord-derived mesenchymal stem cells on clearance of advanced glycation end products through autophagy on diabetic wound

Nowadays, wound healing delay due to diabetes is considered to be closely related to the accumulation of advanced glycation end products (AGEs). Although mesenchymal stem cells (MSCs) exhibit positive effects on diabetic wound healing, related mechanisms are still not fully elucidated. It has been reported that MSCs can improve the activity of autophagy in injured tissues, thereby playing an important role in wound healing. The autophagy induced by MSCs may be beneficial to diabetic wound healing via removing AGEs, which provide new ideas for clinical treatment of diabetic wounds with the potential of broad application prospects. In this study, the current research situation and application prospect of umbilical cord-derived MSCs on the clearance of AGEs in diabetic wound were reviewed.

The Abnormal Architecture of Healed Diabetic Ulcers Is the Result of FAK Degradation by Calpain 1

Delayed wound healing is a major complication of diabetes occurring in approximately 15% of chronic diabetic patients. It not only significantly affects patients' quality of life but also poses a major economic burden to the health care system. Most efforts have been focused on accelerating wound reepithelialization and closure. However, even after healing the quality of healed tissue in diabetics is abnormal and recurrence is common (50-75%). Thus, understanding how diabetes alters the ultimate mechanical properties of healed wounds will be important to develop more effective approaches for this condition. Focal adhesion kinase is an intracellular protein kinase that plays critical roles in cell migration, focal adhesion formation, and is an important component of cellular mechanotransduction. We have found that focal adhesion kinase expression is downregulated under a high glucose condition both in vitro and in vivo. This is secondary to increased activity of calpain 1, the primary enzyme responsible for focal adhesion kinase degradation, which becomes induced in hyperglycemia. We demonstrate that selective inhibition of calpain 1 activation improves wound healing and normalizes the mechanical properties of diabetic skin, suggesting a new therapeutic approach to prevent diabetic wound recurrence.

The effects of advanced glycation end products (AGEs) on dermal wound healing and scar formation: a systematic review

Introduction:

With ageing, the skin gradually loses its youthful appearance and functions like wound healing and scar formation. The pathophysiological theory of Advanced Glycation End products (AGEs) has gained traction during the last decade. This review aims to document the influence of AGEs on the mechanical and physiologic properties of the skin, how they affect dermal wound healing and scar formation in high-AGE populations like elderly patients and diabetics, and potential therapeutic strategies.

Methods:

This systematic literature study involved a structured search in Pubmed and Web of Science with qualitative analysis of 14 articles after a three-staged selection process with the use of in- and exclusion criteria.

Results:

Overall, AGEs cause shortened, thinned, and disorganized collagen fibrils, consequently reducing elasticity and skin/scar thickness with increased contraction and delayed wound closure. Documented therapeutic strategies include dietary AGE restriction, sRAGE decoy receptors, aminoguanidine, RAGE-blocking antibodies, targeted therapy, thymosin β4, anti-oxidant agents and gold nanoparticles, ethyl pyruvate, Gal-3 manipulation and metformin.

Discussion:

With lack of evidence concerning scars, no definitive conclusions can yet be made about the role of AGEs on possible appearance or function of scar tissue. However, all results suggest that scars tend to be more rigid and contractile with persistent redness and reduced tendency towards hypertrophy as AGEs accumulate.

Conclusion:

Abundant evidence supports the pathologic role of AGEs in ageing and dermal wound healing and the effectiveness of possible therapeutic agents. More research is required to conclude its role in scar formation and scar therapy.

Our skin is the body’s first line of defense. It is the barrier that protects us from chemical and biological threats such as viruses, bacteria or corrosive liquids. It is the sensor that allows us to detect physical threats like extreme temperatures, pressure and pain. And when these preventative measures fail, the skin has yet another property: the ability to heal.

Skin changes visibly with age, most notably with the appearance of wrinkles. However, there is more to ageing than meets the eye; invisible alterations cause the decline of various functions of the skin, such as wound healing and scar formation. An array of non-conclusive research has been done in this field. One theory that has gained traction during the last decade is the Advanced Glycation End products (AGEs) theory. The theory states that AGEs play an important role in skin aging, wound healing and the effectiveness of different therapeutic options. Their presence supposedly indicates a diminished ability for wound healing and scar formation.

AGEs are proteins to which sugar molecule is bound. The sugar molecule inhibits the original protein from functioning properly. As skin contains many proteins like collagen, the formation of these AGEs could be a viable explanation for the diminished functioning with ageing. In this review, we investigated whether the accumulation of AGEs affects wound healing and scar formation.

Normal scar formation results in a thin scar. However, it may happen that scarring results in thick, large, painful and itchy scars. We investigated whether people with a high AGE content in their skin, like diabetics and elderly, have difficulties forming aesthetically pleasing scars. Secondly, we investigated which therapies reduce the AGE content and, if so, whether these therapies can improve wound healing and scarring. This literature study involved research in scientific databases with qualitative analysis of 14 articles after a three-staged selection process with the use of set criteria.

We found the different ways in which AGEs affect skin properties and wound healing. Collagen, one of the most important proteins in the skin, is affected by these AGEs. Once a sugar binds to it, the collagen strings becomes thinner and shorter, and the different collagen proteins cross-link with each other in an unstructured way. The result of these alterations is a reduced elasticity, i.e. the skin becomes stiffer. The scar will be thinner and the time for wounds to close is longer. We also found strategies to diminish the AGE content, including dietary AGE restriction and Metformin, a drug used in diabetes.

We can conclude that there is proof of AGEs playing an important role in skin ageing, wound healing and the effectiveness of different therapeutic options. However, more research is required to conclude the exact role of AGEs in scar formation and scar therapy.

The percutaneous permeability and absorption of dexamethasone esters in diabetic rats: a preliminary study

To evaluate the influence of diabetes on the permeation of dexamethasone acetate (DA) and dexamethansone sodium phosphate (DSP), the two major dexamethansone esters in clinical practice, when applied percutaneously, histochemical staining was used to determine the skin morphology; improved Franz diffusion cells and microdialysis were used to assess the percutaneous permeation of DA and DSP in normal and diabetic rats. Histopathological examination showed that the epidermal tissue of diabetic rat was much thinner, the epidermal cell layer was less clear and the stratified arrangement of epidemic cell had almost disappeared and progressive atrophy were developed on the subcutaneous fat. In vitro studies showed that the cumulative and the penetrated DSP amount in Group DM were higher. The mean flux value and the mean depositional amount of Group DM were increased significantly compared to those of Group CTL, whereas the amount of DA penetrating was of no difference. Microdialysis indicated that there was no significant difference between Group CTL and Group DM for all the pharmacokinetic parameters of DA. In contrast, the subcutaneous AUCall values and the C(max) of DSP were significantly increased compared to the control. In conclusion, diabetic rat skin significantly increased the percutaneous permeation of DSP but had no effect on that of DA. It suggests that patients with diabetes should consider the dose of administration when using DA, DSP or other glucocorticoids topically, as different liposolubilities may play some role in the permeability of these compounds via diabetic skin.

Advanced glycation end products assessed by skin autofluorescence: a new marker of diabetic foot ulceration

BACKGROUND

Accumulation of advanced glycation end products (AGEs) may contribute to diabetic foot ulceration (DFU). Our goal was to determine whether AGEs measurement by skin autofluorescence (SAF) would be an additional marker for DFU management.

PATIENTS AND METHODS

We performed SAF analysis in 66 patients with a history of DFU prospectively included and compared the results with those of 84 control patients with diabetic peripheral neuropathy without DFU. We then assessed the prognostic value of SAF levels on the healing rate in the DFU group.

RESULTS

Mean SAF value was significantly higher in the DFU group in comparison with the control group, even after adjustment for other diabetes complications (3.2±0.6 arbitrary units vs. 2.9±0.6 arbitrary units; P=0.001). In the DFU group, 58 (88%) patients had an active wound at inclusion. The mean DFU duration was 14±13 weeks. The healing rate was 47% after 2 months of appropriate foot care. A trend for a correlation between SAF levels and healing time in DFU subjects was observed but was not statistically significant (P=0.06).

CONCLUSIONS

Increased SAF levels are associated with neuropathic foot complications in diabetes. Use of SAF measurement to assess foot vulnerability and to predict DFU events in high-risk patients appears to be promising.

Hyperglycemia increases susceptibility to ischemic necrosis

Diabetic patients are at risk for spontaneous foot ulcers, chronic wounds, infections, and tissue necrosis. Current theories suggest that the development and progression of diabetic foot ulcers are mainly caused by arteriosclerosis and peripheral neuropathy. Tissue necrosis plays a primordial role in the progression of diabetic foot ulcers but the underlying mechanisms are poorly understood. The aim of the present study was to investigate the effects of hyperglycemia per se on the susceptibility of ischemic tissue to necrosis, using a critical ischemic hind limb animal model. We inflicted the same degree of ischemia in both euglycemic and streptozotocin-induced hyperglycemic rats by resecting the external iliac, the femoral, and the saphenous arteries. Postoperative laser Doppler flowmetry of the ischemic feet showed the same degree of reduction in skin perfusion in both hyperglycemic and euglycemic animals. Nevertheless, we found a significantly higher rate of limb necrosis in hyperglycemic rats compared to euglycemic rats (71% versus 29%, resp.). In this study, we revealed that hyperglycemia per se increases the susceptibility to limb necrosis in ischemic conditions. Our results may help to better understand the physiopathology of progressive diabetic wounds and underline the importance of strict glycemic control in patients with critical limb ischemia.