Editorial: Understanding Diabetic Foot Disease: Current Status and Emerging Treatment Approaches

Nrf2 activation: a key mechanism in stem cell exosomes-mediated therapies

Exosomes are nano-sized membrane extracellular vesicles which can be released from various types of cells. Exosomes originating from inflammatory or injured cells can have detrimental effects on recipient cells, while exosomes derived from stem cells not only facilitate the repair and regeneration of damaged tissues but also inhibit inflammation and provide protective effects against various diseases, suggesting they may serve as an alternative strategy of stem cells transplantation. Exosomes have a fundamental role in communication between cells, through the transfer of proteins, bioactive lipids and nucleic acids (like miRNAs and mRNAs) between cells. This transfer significantly impacts both the physiological and pathological functions of recipient cells. Nuclear factor erythroid 2-related factor 2 (Nrf2), a transcription factor, is able to mitigate damage caused by oxidative stress and inflammation through various signaling pathways. The positive effects resulting from the activation of the Nrf2 signaling pathway in different disorders have been documented in various types of literature. Studies have confirmed that exosomes derived from stem cells could act as Nrf2 effective agonists. However, limited studies have explored the Nrf2 role in the therapeutic effects of stem cell-derived exosomes. This review provides a comprehensive overview of the existing knowledge concerning the role of Nrf2 signaling pathways in the impact exerted by stem cell exosomes in some common diseases.

A temperature and pH dual-responsive injectable self-healing hydrogel prepared by chitosan oligosaccharide and aldehyde hyaluronic acid for promoting diabetic foot ulcer healing

Chronic wound, such as skin defect after burn, pressure ulcer, and diabetic foot ulcer is very difficult to cure. Its pathological process is often accompanied with local temperature rise, pH decrease, and other phenomena. Owing to their outstanding hydrophilic, biocompatibility, and responsive properties, hydrogels could accelerate the healing process. In this study, we chose chitosan oligosaccharide (COS) grafted with Pluronic F127 (F127-COS). Aldehyde hyaluronic acid (A-HA) oxidized by NaIO4. And added boric acid (BA) to prepare a thermosensitive and pH-responsive injectable self-healing F127-COS/A-HA/COS/BA (FCAB) hydrogel, loaded with drug deferoxamine (DFO) in order to have an accurate release and promote angiogenesis of diabetic foot ulcer. In vitro experiments had verified that the FCAB hydrogel system loaded with DFO (FCAB/D) could promote migration and angiogenesis of HUVEC. A diabetes rat back wound model further confirmed its role in promoting angiogenesis in wound repair process. The results showed that the FCAB/D hydrogel exhibited unique physicochemical properties, excellent biocompatibility, and significantly enhanced therapeutic effects for diabetic foot ulcer.

Analysis of pre-hospital delay in Chinese patients with diabetic foot ulcers: Based on 46 cases

To study the causes of pre-hospital delay in Chinese patients with diabetic foot ulcers (DFUs). A retrospective study, investigating a case series of 46 DFUs treated at a single hospital, was conducted to evaluate wound condition, wound treatment, costs, and patients' complete medical records, and analyse the reasons causing the pre-hospital delay. We assessed 46 DFUs aged between 53 and 92 years old. The average pre-hospital delay was 5 months, with nearly 20% being delayed for more than 1 year. The average length of hospital stay in China was 21 days, with an average cost of $8672. Recurrence rate of DFUs was 21%, and three patients were recommended to transfer to upper-level hospital. Besides, the intervention was limited and homogenous and medical records were incomplete. Medical service users' limited understanding of diseases, high costs that patients need to afford, and unsatisfactory treatment by medical service providers are the main reasons for patients' delay in seeking treatment. Recommendations are offered to reduce the pre-hospital delay of Chinese patients with DFUs.

UCMSCs-derived exosomal circHIPK3 promotes ulcer wound angiogenesis of diabetes mellitus via miR-20b-5p/Nrf2/VEGFA axis

AIMS

Experiments confirmed that circular RNAs contributed to the pathogenesis of diabetic foot ulcers (DFUs). CircHIPK3 was upregulated in type 2 diabetes mellitus (T2DM), but its role in DFU remained unknown. Our study aimed to investigate the regulatory functions of exosomal circHIPK3 and its potential mechanisms in DFU.

METHODS

Exosomal size and distribution, marker proteins, and circHIPK3 levels were evaluated by transmission electron microscope, ExoView R200, western blot, and qRT-PCR. Flow cytometry, MTT, Wound healing assays, and tube formation assays were used to assess the roles of exosomal circHIPK3 in high glucose (HG)-treated human umbilical vein endothelial cells (HUVECs). The relationships between Nrf2/VEGFA/circHIPK3 and miR-20b-5p, and between Nrf2 and VEGFA were determined by luciferase reporter assay and RNA immunoprecipitation. We used cell and mice models to investigate the mechanisms of exosomal circHIPK3 under diabetic conditions.

RESULTS

CircHIPK3 was significantly upregulated in exo-circHIPK3 rather than exo-vector. Exo-circHIPK3 remarkably inhibited cell apoptosis but promoted cell proliferation, migration, and tube formation in HG-treated HUVECs. Luciferase reporter and RIP assays showed that miR-20b-5p targeted and inhibited Nrf2 and VEGFA, and circHIPK3 acted as a ceRNA of miR-20b-5p to inhibit the binding to its downstream genes Nrf2 and VEGFA. Mechanistically, circHIPK3 promoted cell proliferation, migration, and angiogenesis via downregulating miR-20b-5p to upregulate Nrf2 and VEGFA. However, the overexpressed miR-20b-5p could abolish the promoting effects of circHIPK3 overexpression on cell proliferation, migration, and tube formation under HG conditions.

CONCLUSION

UCMSCs-derived exosomal circHIPK3 protected HG-treated HUVECs via miR-20b-5p/Nrf2/VEGFA axis. The exosomal circHIPK3 might be a therapeutic candidate to treat DFU.

Non-coding RNAs: Role in diabetic foot and wound healing

Diabetic foot ulcer (DFU) and poor wound healing are chronic complications in patients with diabetes. The increasing incidence of DFU has resulted in huge pressure worldwide. Diagnosing and treating this condition are therefore of great importance to control morbidity and improve prognosis. Finding new markers with potential diagnostic and therapeutic utility in DFU has gathered increasing interest. Wound healing is a process divided into three stages: Inflammation, proliferation, and regeneration. Non-coding RNAs (ncRNAs), which are small protected molecules transcribed from the genome without protein translation function, have emerged as important regulators of diabetes complications. The deregulation of ncRNAs may be linked to accelerated DFU development and delayed wound healing. Moreover, ncRNAs can be used for therapeutic purposes in diabetic wound healing. Herein, we summarize the role of microRNAs, long ncRNAs, and circular RNAs in diverse stages of DFU wound healing and their potential use as novel therapeutic targets.

[Effectiveness analysis of modified tibial transverse bone transport technique combined with vancomycin calcium phosphate bone cement local filling and covering in treatment of diabetic foot]

OBJECTIVE

To investigate the effectiveness of modified tibial transverse bone transport technique combined with vancomycin calcium phosphate bone cement local filling and covering in the treatment of diabetic foot (DF).

METHODS

The clinical data of 22 DF patients treated with modified tibial transverse bone transport technique combined with vancomycin calcium phosphate bone cement local filling and covering between October 2019 and December 2021 were retrospectively analyzed. There were 13 males and 9 females with an average age of 61.3 years (range, 41-74 years). The duration of diabetes mellitus was 8-30 years, with an average of 12.5 years, and the duration of DF was 10-42 days, with an average of 28.2 days. There were 2 cases of grade 3 and 20 cases of grade 4 according to Wagner classification. CT angiography was performed on both lower extremities of the patients, and the blood vessels of the affected extremities were narrowed to varying degrees and the blood supply was poor. The preoperative skin temperature of affected foot was (28.27±0.91)°C, the ankle brachial index (ABI) was 0.42±0.11, and the visual analogue scale (VAS) score was 7.7±0.6. Preoperative size of DF ulcer ranged from 2.5 cm×2.0 cm to 3.5 cm×3.0 cm. The skin temperature of affected foot, ABI, VAS score, and skin wound healing of the affected foot were recorded and compared between before operation and at 3 months after operation.

RESULTS

All patients were followed up 3-18 months, with an average of 10.5 months. The infection of 1 patient with Wagner grade 4 did not improve significantly after operation, and there was a trend of further deterioration, and the amputation of the left leg was finally performed at 22 days after operation.The remaining 21 patients recovered well after operation, the external fixator was removed at 1 month after operation, the wound healed at 3 months after operation, and there was no recurrence of ulcer in situ or other sites during follow-up. At 3 months after operation, the skin temperature of affected foot was (31.76±0.34)°C, the ABI was 0.94±0.08, and the VAS score was 2.1±0.3, which significantly improved when compared with those before operation ( t=25.060, P<0.001; t=32.412, P<0.001; t=-51.746, P<0.001).

CONCLUSION

Modified tibial transverse bone transport technique combined with vancomycin calcium phosphate bone cement local filling and covering for DF patients can effectively improve the blood supply of the affected limb, promote wound healing, and improve effectiveness.

Does Obstructive Sleep Apnoea Syndrome Influence the Development and Treatment of Diabetic Foot? A Brief Narrative Review

Both obstructive sleep apnoea syndrome (OSAS) and diabetes mellitus (DM) are common conditions that often coexist and share many similar risk factors. Diabetic foot is a common complication of DM, which may lead to lower-limb amputation. OSAS is considered a risk factor for type 2 DM (T2DM). There is also evidence that OSAS may be linked with the development, as well as the healing of diabetic foot. Multiple mechanisms triggered by sleep fragmentation and intermittent hypoxaemia in OSAS could contribute to the development of diabetic foot ulcers (DFUs). More interestingly, emerging evidence implies a favourable impact of continuous positive airway pressure (CPAP) treatment on DFU healing. Healing DFUs and minimising recurrence rates remains a challenge for health care professionals. In this context, management of OSAS might prove a useful therapeutic adjunct for DFUS. However, data is still limited and randomised controlled trials are needed to further explore this interesting potential.

Effect of the Human Amniotic Membrane on the Umbilical Vein Endothelial Cells of Gestational Diabetic Mothers: New Insight on Inflammation and Angiogenesis

One of the most relevant diabetes complications is impaired wound healing, mainly characterized by reduced peripheral blood flow and diminished neovascularization together with increased inflammation and oxidative stress. Unfortunately, effective therapies are currently lacking. Recently, the amniotic membrane (AM) has shown promising results in wound management. Here, the potential role of AM on endothelial cells isolated from the umbilical cord vein of gestational diabetes-affected women (GD-HUVECs), has been investigated. Indeed, GD-HUVECs in vivo exposed to chronic hyperglycemia during pregnancy compared to control cells (C-HUVECs) have shown molecular modifications of cellular homeostasis ultimately impacting oxidative and nitro-oxidative stress, inflammatory phenotype, nitric oxide (NO) synthesis, and bioavailability, thus representing a useful model for studying the mechanisms potentially supporting the role of AM in chronic non-healing wounds. In this study, the anti-inflammatory properties of AM have been assessed using a monocyte–endothelium interaction assay in cells pre-stimulated with tumor necrosis factor-α (TNF-α) and through vascular adhesion molecule expression and membrane exposure, together with the AM impact on the nuclear factor kappa-light-chain-enhancer of activated B cell (NF-kB) pathway and NO bioavailability. Moreover, GD-HUVEC migration and tube formation ability were evaluated in the presence of AM. The results showed that AM significantly reduced TNF-α-stimulated monocyte–endothelium interaction and the membrane exposure of the endothelial vascular and intracellular adhesion molecules (VCAM-1 and ICAM-1, respectively) in both C- and GD-HUVECs. Strikingly, AM treatment significantly improved vessel formation in GD-HUVECs and cell migration in both C- and GD-HUVECs. These collective results suggest that AM positively affects various critical pathways in inflammation and angiogenesis, thus providing further validation for ongoing clinical trials in diabetic foot ulcers.