Doxorubicin is a commonly used anthracycline chemotherapeutic agent; however, its application is limited owing to its cardiotoxicity. Current clinical treatments cannot efficiently or fully prevent doxorubicin-induced toxicity, primarily because its pathogenesis and mechanisms of action remain unknown. In this study, we established a rat model of chronic doxorubicin-induced cardiotoxicity, in which the severity of cardiac fibrosis and hydroxyproline levels increased in a time-dependent manner. Doxorubicin damaged the mitochondria and blood vessels and induced autophagy. Cells undergoing endothelial-to-mesenchymal transition (EndoMT)and those expressing endothelial cell and myofibroblast markers were simultaneously observed in vitro and in rats treated with doxorubicin. The NF-κB pathway was activated during EndoMT, andp65 and p-p65 were strongly expressed in the nucleus of endothelial cells in vitro. Taken together, these results suggest that vascular injury and cardiac fibrosis are characteristic symptoms of doxorubicin-induced cardiotoxicity. The NF-κB pathway-associated EndoMT may influence the pathogenesis of doxorubicin-induced cardiotoxicity, and the constituents of this pathway may be potential therapeutic targets to prevent the development of this condition.

Background: Radiation-induced dermatitis is a serious side effect of radiotherapy, and very few effective treatments are currently available for this condition. We previously demonstrated that apoptosis is an important feature of radiation-induced dermatitis and adipose-derived stem cells (ADSCs) are one of the most promising types of stem cells that have a protective effect on acute radiation-induced dermatitis. Cathepsin F (CTSF) is a recently discovered protein that plays an important role in apoptosis. In this study, we investigated whether ADSCs affect chronic radiation-induced dermatitis, and the underlying mechanisms involved. Methods: ADSCs were isolated from male Sprague-Dawley (SD) rats and characterized. For in vivo studies, rats were randomly divided into control and ADSC-treated groups, and cultured ADSCs were transplanted into radiation-induced dermatitis model rats. The effects of ADSC transplantation were determined by skin damage scoring, histopathological analysis, electron microscopy, immunohistochemical staining, and western blotting analysis of apoptosis-related proteins. To evaluate the effects of ADSCs in vitro, radiation-induced apoptotic cells were treated with ADSC culture supernatant, and apoptosis-related protein expression was investigated by TUNEL staining, flow cytometry, and western blotting. Results: In the in vivo studies, skin damage, inflammation, fibrosis, and apoptosis were reduced and hair follicle and sebaceous gland regeneration were enhanced in the ADSC group compared with the control group. Further, CTSF and downstream pro-apoptotic proteins (Bid, BAX, and caspase 9) were downregulated, while anti-apoptotic proteins (Bcl-2 and Bcl-XL) were upregulated. In vitro, ADSCs markedly attenuated radiation-induced apoptosis, downregulated CTSF and downstream pro-apoptotic proteins, and upregulated anti-apoptotic proteins. Conclusion: ADSCs protect against radiation-induced dermatitis by exerting an anti-apoptotic effect through inhibition of CTSF expression. ADSCs may be a good therapeutic candidate to prevent the development of radiation-induced dermatitis.

Radiation‐induced dermatitis is a common and serious side effect after radiotherapy. Current clinical treatments cannot efficiently or fully prevent the occurrence of post‐irradiation dermatitis, which remains a significant clinical problem. Resolving this challenge requires gaining a better understanding of the precise pathophysiology, which in turn requires establishment of a suitable animal model that mimics the clinical condition, and can also be used to investigate the mechanism and explore effective treatment options. In this study, a single dose of 90 Gy irradiation to rats resulted in ulceration, dermal thickening, inflammation, hair follicle loss, and sebaceous glands loss, indicating successful establishment of the model. Few hair follicle cells migrated to form epidermal cells, and both the severity of skin fibrosis and hydroxyproline levels increased with time post‐irradiation. Radiation damaged the mitochondria and induced both apoptosis and autophagy of the skin cells. Therefore, irradiation of 90 Gy can be used to successfully establish a rat model of radiation‐induced dermatitis. This model will be helpful for developing new treatments and gaining a better understanding of the pathological mechanism of radiation‐induced dermatitis. Specifically, our results suggest autophagy regulation as a potentially effective therapeutic target.

Radiation-induced muscle fibrosis is a long-term side effect of radiotherapy that significantly affects the quality of life and even reduces the survival of cancer patients. We have demonstrated that radiation induces satellite cell (SC) activation at the molecular level; however, cellular evidence in a rat model of radiation-induced muscle fibrosis was lacking. In this study, we evaluated SC activation in vivo and investigated whether radiation affects the proliferation and differentiation potential of SCs in vitro. For in vivo studies, Sprague-Dawley rats were randomly divided into six groups (n = 6 per group): non-irradiated controls, 90 Gy/1 week-, 90 Gy/2 weeks-, 90 Gy/4 weeks-, 90 Gy/12 weeks- and 90 Gy/24 weeks-postirradiation groups. Rats received a single dose of radiation in the left groin area and rectus femoris tissues were collected in the indicated weeks. Fibrosis, apoptosis, and autophagy were evaluated by Masson's trichrome staining, TUNEL staining, and electron microscopy, respectively. SC activation and central nuclear muscle fibers were evaluated by immunofluorescence staining and hematoxylin and eosin staining. IL-1β concentrations in serum and irradiated muscle tissue samples were determined by ELISA. For in vitro studies, SCs were isolated from rats with radiation-induced muscle fibrosis and their proliferation and differentiation were evaluated by immunofluorescence staining. In vivo, fibrosis increased over time postirradiation. Apoptosis and autophagy levels, IL-1β concentrations in serum and irradiated skin tissues, and the numbers of SCs and central nuclear muscle fibers were increased in the irradiated groups when compared with the control group. In vitro, cultured SCs from irradiated muscle were positive for the proliferation marker Pax7, and differentiated SCs were positive for the myogenic differentiation marker MyHC. This study provided cellular evidence of SC activation and proliferation in rats with radiation-induced muscle fibrosis.

Background: Radiation-induced muscle fibrosis (RIF) is a severe late-stage side effect of radiotherapy in adjacent normal tissues, significantly affecting anticancer therapeutic efficacy and potentially being life-threatening. Previous studies have shown that satellite cells (SCs) become activated after ionizing radiation to facilitate muscle tissue repair. However, the acceleration and strengthening of this process have received little attention until recently. Adipose-derived stem cells (ADSCs), a type of mesenchymal stem cell, have emerged as a promising therapeutic option in regenerative medicine due to their accessibility, abundance, and plasticity in adult organisms. In this study, we explored whether ADSCs could enhance SC proliferation and differentiation after radiation therapy. Methods: ADSCs were harvested, cultured, and passaged from male Sprague–Dawley rats and characterized in vitro . In vivo , rats were randomly assigned to control and ADSC-treated groups (n = 6). ADSCs were transplanted into RIF rat models at different time points (4, 12, and 24 w). The therapeutic effects of transplanted ADSCs were assessed via Masson’s trichrome staining, electron microscopy, and hematoxylin–eosin (H&E) staining. SC activation, proliferation, and central nuclear immigration following ADSC transplantation therapy were evaluated via real-time polymerase chain reaction and H&E staining. Results: In vivo , fibrosis was markedly alleviated over time following ADSC treatment. In the RIF rat model, ultrastructural histopathological changes, including mitochondrial edema and vacuolization, myofilament dissolution, and vascular endothelial swelling, were notably attenuated by ADSC transplantation. Additionally, SCs exhibited a significant increase in activation and proliferation in the ADSC-treated groups, accompanied by a decrease in fibrotic symptoms. Conclusion: Our study provides evidence that ADSCs protect against RIF by promoting SC activation, proliferation, and differentiation in vivo . ADSCs may represent a promising therapeutic candidate for restoring muscle dysfunction and abnormalities caused by RIF.

Background: Radiation-induced muscle fibrosis is a long-term side effect of radiotherapy that significantly affect the quality of life and even reduces the survival of cancer patients. We have demonstrated that radiation induces satellite cell (SC) activation at the molecular level; however, cellular evidence in a rat model of radiation-induced muscle fibrosis was lacking. In this study, we evaluated SC activation in vivo and investigated whether radiation affects the proliferation and differentiation potential of SCs in vitro. Methods: For in vivo studies, Sprague-Dawley rats were randomly divided into six groups (n = 6 per group): a non-irradiated control group and 90 Gy-1 w, 90 Gy-2 w, 90 Gy-4 w, 90 Gy-12 w, and 90 Gy-24 w groups.Left groin area of the rats received a single dose of irradiation and rectus femoris tissues were collected in the indicated weeks. Fibrosis, apoptosis, and autophagy were evaluated by Masson’s trichrome staining, TUNEL staining, and electron microscopy, respectively. SC activation and central nuclear muscle fibers were evaluated by immunofluorescence staining and hematoxylin and eosin staining. IL-1β concentrations in serum and irradiated muscle tissue samples were determined by ELISA. For in vitro studies, SCs were isolated from rats with radiation-induced muscle fibrosis and their proliferation and differentiation were evaluated by immunofluorescence staining.Results: In vivo, fibrosis increased over time following irradiation. Apoptosis and autophagy levels, IL-1β concentrations in serum and irradiated skin tissues, and the numbers of SCs and central nuclear muscle fibers were increased in the irradiated groups when compared with control group. In vitro, cultured SCs from irradiated muscle were positive for proliferation marker Pax7, and differentiated SCs were positive for myogenic differentiation marker MyHC.Conclusion: This study provided cellular evidence of SC activation and proliferation in rats with radiation-induced muscle fibrosis. Radiation does not affect the proliferation and differentiation potential of SCs in vitro.