The Involvement of SDF-1α/CXCR4 Axis in Radiation-Induced Acute Injury and Fibrosis of Skin

A Frog Skin-Derived Peptide Targeting SCD1 Exerts Radioprotective Effects Against Skin Injury by Inhibiting STING-Mediated Inflammation

The extensive application of nuclear technology has increased the potential of uncontrolled radiation exposure to the public. Since skin is the largest organ, radiation-induced skin injury remains a serious medical concern. Organisms evolutionally develop distinct strategies to protect against environment insults and the related research may bring novel insights into therapeutics development. Here, 26 increased peptides are identified in skin tissues of frogs (Pelophylax nigromaculatus) exposed to electron beams, among which four promoted the wound healing of irradiated skin in rats. Specifically, radiation-induced frog skin peptide-2 (RIFSP-2), from histone proteolysis exerted membrane permeability property, maintained cellular homeostasis, and reduced pyroptosis of irradiated cells with decreased TBK1 phosphorylation. Subsequently, stearyl-CoA desaturase 1 (SCD1) is identified, a critical enzyme in biogenesis of monounsaturated fatty acids (MUFAs) as a direct target of RIFSP-2 based on streptavidin-biotin system. The lipidomic analysis further assured the restrain of MUFAs biogenesis by RIFSP-2 following radiation. Moreover, the decreased MUFA limited radiation-induced and STING-mediated inflammation response. In addition, genetic depletion or pharmacological inhibition of STING counteracted the decreased pyroptosis by RIFSP-2 and retarded tissue repair process. Altogether, RIFSP-2 restrains radiation-induced activation of SCD1-MUFA-STING axis. Thus, the stress-induced amphibian peptides can be a bountiful source of novel radiation mitigators.

Targeting the CXCL12/CXCR4 pathway to reduce radiation treatment side effects

High precision, image-guided radiotherapy (RT) has increased the therapeutic ratio, enabling higher tumor and lower normal tissue doses, leading to improved patient outcomes. Nevertheless, some patients remain at risk of developing serious side effects.In many clinical situations, the radiation tolerance of normal tissues close to the target volume limits the dose that can safely be delivered and thus the potential for tumor control and cure. This is particularly so in patients being re-treated for tumor progression or a second primary tumor within a previous irradiated volume, scenarios that are becoming more frequent in clinical practice.Various normal tissue 'radioprotective' drugs with the potential to reduce side effects have been studied previously. Unfortunately, most have failed to impact clinical practice because of lack of therapeutic efficacy, concern about concurrent tumor protection or excessive drug-related toxicity. This review highlights the evidence indicating that targeting the CXCL12/CXCR4 pathway can mitigate acute and late RT-induced injury and reduce treatment side effects in a manner that overcomes these previous translational challenges. Pre-clinical studies involving a broad range of normal tissues commonly affected in clinical practice, including skin, lung, the gastrointestinal tract and brain, have shown that CXCL12 signalling is upregulated by RT and attracts CXCR4-expressing inflammatory cells that exacerbate acute tissue injury and late fibrosis. These studies also provide convincing evidence that inhibition of CXCL12/CXCR4 signalling during or after RT can reduce or prevent RT side effects, warranting further evaluation in clinical studies. Greater dialogue with the pharmaceutical industry is needed to prioritize the development and availability of CXCL12/CXCR4 inhibitors for future RT studies.

Deciphering the fibrotic process: mechanism of chronic radiation skin injury fibrosis

This review explores the mechanisms of chronic radiation-induced skin injury fibrosis, focusing on the transition from acute radiation damage to a chronic fibrotic state. It reviewed the cellular and molecular responses of the skin to radiation, highlighting the role of myofibroblasts and the significant impact of Transforming Growth Factor-beta (TGF-β) in promoting fibroblast-to-myofibroblast transformation. The review delves into the epigenetic regulation of fibrotic gene expression, the contribution of extracellular matrix proteins to the fibrotic microenvironment, and the regulation of the immune system in the context of fibrosis. Additionally, it discusses the potential of biomaterials and artificial intelligence in medical research to advance the understanding and treatment of radiation-induced skin fibrosis, suggesting future directions involving bioinformatics and personalized therapeutic strategies to enhance patient quality of life.

The Involvement of Cysteine-X-Cysteine Motif Chemokine Receptors in Skin Homeostasis and the Pathogenesis of Allergic Contact Dermatitis and Psoriasis

Members of the C-X-C motif chemokine receptor (CXCR) superfamily play central roles in initiating the innate immune response in mammalian cells by orchestrating selective cell migration and immune cell activation. With its multilayered structure, the skin, which is the largest organ in the body, performs a crucial defense function, protecting the human body from harmful environmental threats and pathogens. CXCRs contribute to primary immunological defense; these receptors are differentially expressed by different types of skin cells and act as key players in initiating downstream innate immune responses. While the initiation of inflammatory responses by CXCRs is essential for pathogen elimination and tissue healing, overactivation of these receptors can enhance T-cell-mediated autoimmune responses, resulting in excessive inflammation and the development of several skin disorders, including psoriasis, atopic dermatitis, allergic contact dermatitis, vitiligo, autoimmune diseases, and skin cancers. In summary, CXCRs serve as critical links that connect innate immunity and adaptive immunity. In this article, we present the current knowledge about the functions of CXCRs in the homeostasis function of the skin and their contributions to the pathogenesis of allergic contact dermatitis and psoriasis. Furthermore, we will examine the research progress and efficacy of therapeutic approaches that target CXCRs.

Tissue fibrosis induced by radiotherapy: current understanding of the molecular mechanisms, diagnosis and therapeutic advances

Cancer remains the leading cause of death around the world. In cancer treatment, over 50% of cancer patients receive radiotherapy alone or in multimodal combinations with other therapies. One of the adverse consequences after radiation exposure is the occurrence of radiation-induced tissue fibrosis (RIF), which is characterized by the abnormal activation of myofibroblasts and the excessive accumulation of extracellular matrix. This phenotype can manifest in multiple organs, such as lung, skin, liver and kidney. In-depth studies on the mechanisms of radiation-induced fibrosis have shown that a variety of extracellular signals such as immune cells and abnormal release of cytokines, and intracellular signals such as cGAS/STING, oxidative stress response, metabolic reprogramming and proteasome pathway activation are involved in the activation of myofibroblasts. Tissue fibrosis is extremely harmful to patients' health and requires early diagnosis. In addition to traditional serum markers, histologic and imaging tests, the diagnostic potential of nuclear medicine techniques is emerging. Anti-inflammatory and antioxidant therapies are the traditional treatments for radiation-induced fibrosis. Recently, some promising therapeutic strategies have emerged, such as stem cell therapy and targeted therapies. However, incomplete knowledge of the mechanisms hinders the treatment of this disease. Here, we also highlight the potential mechanistic, diagnostic and therapeutic directions of radiation-induced fibrosis.

Establishment of image-guided radiotherapy of orthotopic hepatocellular carcinoma mouse model

BACKGROUND

Hepatocellular carcinoma (HCC) is the most common type of liver cancer. Recently, developments in radiotherapy technology have led to radiotherapy becoming one of the main therapeutics of HCC. Therefore, a suitable animal model for radiotherapy of the orthotopic HCC mouse model is urgently needed.

METHODS

In the present study, Hepa1-6 cells were injected into the liver of C57BL/6 mice in situ to mimic the pathological characteristics of the original HCC. Tumor formation was monitored by applying magnetic resonance imaging techniques and verified by H&E histopathological staining, AFP staining, and Ki67 staining. A single dose of 10 Gy X-ray was applied to simulate clinical radiotherapy plans using image-guided radiotherapy (IGRT) equipment. The efficiency of radiotherapy was then assessed by examining tumor size and weight one week after radiation. Cleaved-caspase3 staining and TUNEL were used to assess apoptosis in tumor tissues.

RESULTS

Intrahepatic tumor development was detected in the liver according using MRI. A high-density shadow could be seen 10 days after cell injection, which indicated the formation of HCC in vivo. The tumors grew steadily bigger, and underwent precision radiotherapy 20 days after injection. The typical pathological characteristics of HCC, such as large, deeply stained nuclei and irregular cell size, were visible with H&E staining. After radiotherapy, significantly higher expression of the immunohistochemical markers Ki67 and AFP were detected in tumor tissue than in the nearby normal tissue. Compared with the control group, the tumor volume (p = 0.05) and weight (p < 0.05) of the irradiated group were significantly reduced. In addition, a higher frequency of apoptosis was identified in irradiated HCC tumor tissue using the TUNEL and cleaved-caspase3 staining assay.

CONCLUSIONS

In a well-established orthotopic HCC model, MRI was utilized to monitor the formation of tumors, and IGRT was used to simulate clinical radiotherapy. The present study could provide a suitable preclinical system for HCC radiotherapy-related studies.

Autophagy gene Atg7 regulates the development of radiation-induced skin injury and fibrosis of skin

BACKGROUND

Radiation-induced skin injury, which may progress to fibrosis, is a severe side effect of radiotherapy in patients with cancer. However, currently, there is a lack of preventive or curative treatments for this injury. Meanwhile, the mechanisms underlying this injury remain poorly understood. Here, we elucidated whether autophagy is essential for the development of radiation-induced skin injury and the potential molecular pathways and mechanisms involved.

METHODS AND RESULTS

We used the myofibroblast-specific Atg7 knockout (namely, conditional Atg7 knockout) mice irradiated with a single electron beam irradiation dose of 30 Gy. Vaseline-based 0.2% rapamycin ointment was topically applied once daily from the day of irradiation for 30 days. On day 30 post irradiation, skin tissues were harvested for further analysis. In vitro, human foreskin fibroblast cells were treated with rapamycin (100 nM) for 24 h and pretreated with 3-MA (5 mM) for 12 h. Macroscopic skin manifestations, histological changes, and fibrosis markers at the mRNA and protein expression levels were measured. Post irradiation, the myofibroblast-specific autophagy-deficient (Atg7Flox/Flox Cre+ ) mice had increased fibrosis marker (COL1A1, CTGF, TGF-β1, and α-SMA) levels in the irradiated area and had more severe macroscopic skin manifestations than the control group (Atg7Flox/Flox Cre- ) mice. Treatment with an autophagy agonist rapamycin attenuated macroscopic skin injury scores and skin fibrosis marker levels with decreased epidermal thickness and dermal collagen deposition in Atg7Flox/Flox Cre+ mice compared with the vehicle control. Moreover, in vitro experiment results were consistent with the in vivo results. Together with studies at the molecular level, we found that these changes involved the Akt/mTOR pathway. In addition, this phenomenon might also relate to Nrf2-autophagy signaling pathway under oxidative stress conditions.

CONCLUSION

In conclusion, Atg7 and autophagy-related mechanisms confer radioprotection, and reactivation of the autophagy process can be a novel therapeutic strategy to reduce and prevent the occurrence of radiodermatitis, particularly skin fibrosis, in patients with cancer.

Impact of radiation therapy on healthy tissues

Radiation therapy has a fundamental role in the management of cancers. However, despite a constant improvement in radiotherapy techniques, the issue of radiation-induced side effects remains clinically relevant. Mechanisms of acute toxicity and late fibrosis are therefore important topics for translational research to improve the quality of life of patients treated with ionizing radiations. Tissue changes observed after radiotherapy are consequences of complex pathophysiology, involving macrophage activation, cytokine cascade, fibrotic changes, vascularization disorders, hypoxia, tissue destruction and subsequent chronic wound healing. Moreover, numerous data show the impact of these changes in the irradiated stroma on the oncogenic process, with interplays between tumor radiation response and pathways involved in the fibrotic process. The mechanisms of radiation-induced normal tissue inflammation are reviewed, with a focus on the impact of the inflammatory process on the onset of treatment-related toxicities and the oncogenic process. Possible targets for pharmacomodulation are also discussed.

NF-E2-Related Factor 2 (Nrf2) Ameliorates Radiation-Induced Skin Injury

Radiation-induced skin injury (RISI) commonly occur in cancer patients who received radiotherapy and is one of the first clinical symptoms after suffering from nuclear exposure. Oxidative damage is the major causes of RISI. Nuclear factor erythroid 2-related factor 2 (Nrf2) is considered as a key mediator of the cellular antioxidant response. However, whether Nrf2 can alleviate RISI after high-dose irradiation remains unknown. In this study, we demonstrated that Nrf2-deficient (Nrf2^-/-) mice were susceptible to high-dose irradiation and adenovirus-mediated overexpression of Nrf2 (ad-Nrf2) protected against radiation in skin cells. Overexpression of Nrf2 attenuated the severity of skin injury after high-dose electron beam irradiation. To uncover the mechanisms of Nrf2 involved in RISI, mRNA sequencing technology was performed to analyze the mRNA expression profiles of Ad-Nrf2 skin cells following radiation. The results revealed that a total of 127 genes were significantly changed, 55 genes were upregulated, and 72 genes were downregulated after Nrf2 overexpression. GSEA showed that Nrf2 was associated with positive regulation of genes involved in the reactive oxygen species pathway after radiation. Taken together, this study illustrated the role of Nrf2 in RISI and provided potentially strategies for ameliorating RISI.

Activated Beta-Catenin Signaling Ameliorates Radiation-Induced Skin Injury by Suppressing Marvel D3 Expression

Radiation-induced skin injury remains a serious concern for cancer radiotherapy, radiation accidents and occupational exposure, and the damage mainly occurs due to apoptosis and reactive oxygen species (ROS) generation. There is currently no effective treatment for this disorder. The β-catenin signaling pathway is involved in the repair and regeneration of injured tissues. However, the role of the β-catenin signaling pathway in radiation-induced skin injury has not been reported. In this study, we demonstrated that the β-catenin signaling pathway was activated in response to radiation and that its activation by Wnt3a, a ligand-protein involved in the β-catenin signaling pathway, inhibited apoptosis and the production of ROS in irradiated human keratinocyte HaCaT cells and skin fibroblast WS1 cells. Additionally, Wnt3a promoted cell migration after irradiation. In a mouse model of full-thickness skin wounds combined with total-body irradiation, Wnt3a was shown to facilitate skin wound healing. The results from RNA-Seq revealed that 24 genes were upregulated and 154 were downregulated in Wnt3a-treated irradiated skin cells, and these dysregulated genes were mainly enriched in the tight junction pathway. Among them, Marvel D3 showed the most obvious difference. We further found that the activated β-catenin signaling pathway stimulated the phosphorylation of JNK by silencing Marvel D3. Treatment of irradiated cells with SP600125, a JNK inhibitor, augmented ROS production and impeded cell migration. Furthermore, treatment with Wnt3a or transfection with Marvel D3-specific siRNAs could reverse the above effects. Taken together, these findings illustrate that activated β-catenin signaling stimulates the activation of JNK by negatively regulating Marvel D3 to ameliorate radiation-induced skin injury.

Conditioned medium of human bone marrow-derived stem cells promotes tendon-bone healing of the rotator cuff in a rat model

Rotator cuff repair is a common surgery in sports medicine. During the surgery, torn tendon was re-fixed onto the bony surface. The majority of patients gain good results. However, re-tear occurs in some patients. The reason under this phenomenon is that the normal tendon-bone enthesis cannot be reconstructed. In order to strengthen the tendon-bone healing and promote enthesis regeneration, numerous manners are tested, among which stem cell related therapies are preferred. Stem cells, due to the ability of multi-lineage differentiation, are widely used in regenerative medicine. However, safety and ethics concerns limit its clinical use. Recent studies found that it is the secretome of stem cells that is biologically effective. On ground of this, we, in the current study, collected the conditioned medium of human bone marrow-derived stem cells (hBMSC-CM) and tested whether this acellular method could promote tendon-bone healing in a rat model of rotator cuff repair. By using histological, radiological, and biomechanical methods, we found that hBMSC-CM promoted tendon-bone healing of the rat rotator cuff. Then, we noticed that hBMSC-CM exerted an impact on macrophage polarization both in vivo and in vitro by inhibiting M1 phenotype and promoting M2 phenotype. Further, we proved that the benefit of hBMSC-CM on tendon-bone healing was related to its regulation on macrophage. Finally, we proved that, hBMSC-CM influenced macrophage polarization, which was, at least partially, related to Smad2/3 signaling pathway. Based on the experiments above, we confirmed the benefit of hBMSC-CM on tendon-bone healing, which relied on its immune-regulative property. Considering the accessibility and safety of acellular hBMSC-CM, we believe it is a promising candidate clinically for tendon-bone healing.

Extracellular Vesicles From Liver Progenitor Cells Downregulates Fibroblast Metabolic Activity and Increase the Expression of Immune-Response Related Molecules

Extracellular vesicles (EVs) mediate cell-to-cell crosstalk whose content can induce changes in acceptor cells and their microenvironment. MLP29 cells are mouse liver progenitor cells that release EVs loaded with signaling cues that could affect cell fate. In the current work, we incubated 3T3-L1 mouse fibroblasts with MLP29-derived EVs, and then analyzed changes by proteomics and transcriptomics. Results showed a general downregulation of protein and transcript expression related to proliferative and metabolic routes dependent on TGF-beta. We also observed an increase in the ERBB2 interacting protein (ERBIN) and Cxcl2, together with an induction of ribosome biogenesis and interferon-related response molecules, suggesting the activation of immune system signaling.