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This study was conducted to determine whether a secretome from mesenchymal stem cells (MSC) modulated by hypoxic conditions to contain therapeutic factors contributes to salivary gland (SG) tissue remodeling and has the potential to improve irradiation (IR)-induced salivary hypofunction in a mouse model. Human adipose mesenchymal stem cells (hAdMSC) were isolated, expanded, and exposed to hypoxic conditions (O2 < 5%). The hypoxia-conditioned medium was then filtered to a high molecular weight fraction and prepared as a hAdMSC secretome. The hAdMSC secretome was subsequently infused into the tail vein of C3H mice immediately after local IR once a day for seven consecutive days. The control group received equal volume (500 μL) of vehicle (PBS) only. SG function and structural tissue remodeling by the hAdMSC secretome were investigated. Human parotid epithelial cells (HPEC) were obtained, expanded in vitro, and then irradiated and treated with either the hypoxia-conditioned medium or a normoxic control medium. Cell proliferation and IR-induced cell death were examined to determine the mechanism by which the hAdMSC secretome exerted its effects. The conditioned hAdMSC secretome contained high levels of GM-CSF, VEGF, IL-6, and IGF-1. Repeated systemic infusion with the hAdMSC secretome resulted in improved salivation capacity and increased levels of salivary proteins, including amylase and EGF, relative to the PBS group. The microscopic structural integrity of SG was maintained and salivary epithelial (AQP-5), endothelial (CD31), myoepithelial (α-SMA) and SG progenitor cells (c-Kit) were successfully protected from radiation damage and remodeled. The hAdMSC secretome strongly induced proliferation of HPEC and led to a significant decrease in cell death in vivo and in vitro. Moreover, the anti-apoptotic effects of the hAdMSC secretome were found to be promoted after hypoxia-preconditioning relative to normoxia-cultured hAdMSC secretome. These results show that the hAdMSC secretome from hypoxic-conditioned medium may provide radioprotection and tissue remodeling via release of paracrine mediators.

Nervous system injury is a frequent result of cancer therapy involving cranial irradiation, leaving patients with marked memory and other neurobehavioral disabilities. Here, we report an unanticipated link between bone marrow and brain in the setting of radiation injury. Specifically, we demonstrate that bone marrow-derived monocytes and macrophages are essential for structural and functional repair mechanisms, including regeneration of cerebral white matter and improvement in neurocognitive function. Using a granulocyte-colony stimulating factor (G-CSF) receptor knockout mouse model in combination with bone marrow cell transplantation, MRI, and neurocognitive functional assessments, we demonstrate that bone marrow-derived G-CSF-responsive cells home to the injured brain and are critical for altering neural progenitor cells and brain repair. Additionally, compared with untreated animals, animals that received G-CSF following radiation injury exhibited enhanced functional brain repair. Together, these results demonstrate that, in addition to its known role in defense and debris removal, the hematopoietic system provides critical regenerative drive to the brain that can be modulated by clinically available agents.

Radiotherapy can be limited by pneumonitis, which is impacted by innate immunity, including pathways regulated by TRAIL death receptor DR5. We investigated whether DR5 agonists could rescue mice from toxic effects of radiation and found that 2 different agonists, parenteral PEGylated trimeric TRAIL (TLY012) and oral TRAIL-inducing compound (TIC10/ONC201), could reduce pneumonitis, alveolar wall thickness, and oxygen desaturation. Lung protection extended to late effects of radiation including less fibrosis at 22 weeks in TLY012-rescued survivors versus unrescued surviving irradiated mice. Wild-type orthotopic breast tumor-bearing mice receiving 20 Gy thoracic radiation were protected from pneumonitis with disappearance of tumors. At the molecular level, radioprotection appeared to be due to inhibition of CCL22, a macrophage-derived chemokine previously associated with radiation pneumonitis and pulmonary fibrosis. Treatment with anti-CCL22 reduced lung injury in vivo but less so than TLY012. Pneumonitis severity was worse in female versus male mice, and this was associated with increased expression of X-linked TLR7. Irradiated mice had reduced esophagitis characterized by reduced epithelial disruption and muscularis externa thickness following treatment with the ONC201 analog ONC212. The discovery that short-term treatment with TRAIL pathway agonists effectively rescues animals from pneumonitis, dermatitis, and esophagitis following high doses of thoracic radiation exposure has important translational implications.

The pathological mechanisms of radiation ulcer remain unsolved and there is currently no effective medicine. Here, we demonstrate that persistent DNA damage foci and cell senescence are involved in radiation ulcer development. Further more, we identify cordycepin, a natural nucleoside analogue, as a potent drug to block radiation ulcer (skin, intestine, tongue) in rats/mice by preventing cell senescence through the increase of NRF2 nuclear expression (the assay used is mainly on skin). Finally, cordycepin is also revealed to activate AMPK by binding with the α1 and γ1 subunit near the autoinhibitory domain of AMPK, then promotes p62-dependent autophagic degradation of Keap1, to induce NRF2 dissociate from Keap1 and translocate to the nucleus. Taken together, our findings identify cordycepin prevents radiation ulcer by inhibiting cell senescence via NRF2 and AMPK in rodents, and activation of AMPK or NRF2 may thus represent therapeutic targets for preventing cell senescence and radiation ulcer. Radiation damage causes DNA foci to form and senescence, causing ulcers. Here, the authors show that a naturally occurring adenosine analogue, cordycepin, prevents cell senescence via an increase in AMPK/NRF2, so blocking ulcers caused by radiation on skin/intestine/tongue damage in rodents.

Fibrosis is a leading cause of death in occidental states. The increasing number of patients with fibrosis requires innovative approaches. Despite the proven beneficial effects of mesenchymal stem cell (MSC) therapy on fibrosis, there is little evidence of their anti-fibrotic effects in colorectal fibrosis. The ability of MSCs to reduce radiation-induced colorectal fibrosis has been studied in vivo in Sprague–Dawley rats. After local radiation exposure, rats were injected with MSCs before an initiation of fibrosis. MSCs mediated a downregulation of fibrogenesis by a control of extra cellular matrix (ECM) turnover. For a better understanding of the mechanisms, we used an in vitro model of irradiated cocultured colorectal fibrosis in the presence of human MSCs. Pro-fibrotic cells in the colon are mainly intestinal fibroblasts and smooth muscle cells. Intestinal fibroblasts and smooth muscle cells were irradiated and cocultured in the presence of unirradiated MSCs. MSCs mediated a decrease in profibrotic gene expression and proteins secretion. Silencing hepatocyte growth factor (HGF) and tumor necrosis factor-stimulated gene 6 (TSG-6) in MSCs confirmed the complementary effects of these two genes. HGF and TSG-6 limited the progression of fibrosis by reducing activation of the smooth muscle cells and myofibroblast. To settle in vivo the contribution of HGF and TSG-6 in MSC-antifibrotic effects, rats were treated with MSCs silenced for HGF or TSG-6. HGF and TSG-6 silencing in transplanted MSCs resulted in a significant increase in ECM deposition in colon. These results emphasize the potential of MSCs to influence the pathophysiology of fibrosis-related diseases, which represent a challenging area for innovative treatments.

Liver damage caused by radiotherapy is associated with a high mortality rate, but no established treatment exists. Adipose-derived mesenchymal stem cells (ADSCs) are capable of migration to injured tissue sites, where they aid in the repair of the damage. Hepatocyte growth factor (HGF) is critical for damage repair due to its anti-apoptotic, anti-fibrotic and cell regeneration-promoting effects. This study was performed to investigate the therapeutic effects of HGF-overexpressing ADSCs on radiation-induced liver damage (RILD). ADSCs were infected with a lentivirus encoding HGF and HGF-shRNA. Sprague-Dawley (SD) rats received 60Gy of irradiation to induce liver injury and were immediately given either saline, ADSCs, ADSCs + HGF or ADSCs + shHGF. Two days after irradiation, a significant reduction in apoptosis was observed in the HGF-overexpressing ADSC group compared with the RILD group, as assessed by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Scanning electron microscopy showed chromatin condensation after irradiation, which was ameliorated in the group that received ADSCs and was reversed in the group that received HGF-overexpressing ADSCs. HGF-overexpressing ADSCs ameliorated radiation- induced liver fibrosis through down regulation of α-SMA and fibronectin. Hepatocyte regeneration was significantly improved in rats treated with ADSCs compared with rats from the RILD group), as assessed by Ki-67 immunohistochemistry. Rats that received HGF-overexpressing ADSCs showed an even greater level of hepatocyte regeneration. HGF-overexpressing ADSCs completely blocked the radiation-induced increase in the enzymes ALT and AST. The effect of mitigating RILD was compromised in the ADSC + shHGF group compared with the ADSC group. Altogether, these results suggest that HGF-overexpressing ADSCs can significantly improve RILD in a rat model, which may serve as a valuable therapeutic alternative.

For preparedness for some scenarios such as unintentional accidents or intentional malicious events, it is of critical importance to develop effective medical countermeasures against normal tissue injury from exposure to ionizing radiation. To this end, agents that are effective when administered after radiation exposure need to be developed. Considering that vascular injury is among the upstream events of radiation toxicity in various tissues, the present study was undertaken to investigate whether post-irradiation implantation of human mesenchymal stem/stromal cells (MSCs) restore vascular injury induced by acute irradiation. MSCs were obtained from human adipose tissue. For in vivo experiments, young adult male C57BL/6J mice ( n  = 8/group) were received intravenous injection of 5 × 10 4 MSCs or vehicle at 6 h after irradiation with 5 Gy (sublethal dose) of 137 Cs γ-rays. Control mice were sham-irradiated and received vehicle injection. At four weeks after irradiation, the aorta was collected, and subjected to scanning electron microscopy, immunofluorescence and histochemistry staining. Irradiation led to various changes in the aorta of mice, such as detachment and partial loss of the endothelium, decreases in vascular endothelial cadherin and endothelial nitric oxide synthase, vascular endothelial and smooth muscle cell death, inflammation (evidenced by increases in CD68, F4/80 and CD3) and fibrosis (evidenced by increases in transforming growth factor β1 and collagen). Post-irradiation MSC implantation restored such radiation-induced vascular damage.

To investigate the efficacy of Nintedanib in treating acute and chronic radiation-induced lung injury and its mechanism of action. A radiation-induced lung injury model was established in mice using 6MV X-rays at 18Gy to irradiate the lungs. The mice were randomly divided into four groups: control group, radiation therapy group, low-dosage Nintedanib + radiation therapy group, and high dosage Nintedanib + radiation therapy group. The mice were euthanized on day 14 and 3 months post-radiation to observe changes in acute and chronic inflammation and the expression of related proteins. Compared to the radiation therapy group, the low and high-dosage Nintedanib groups showed varying degrees of improvement in mental state, responsiveness, food and water intake, and fur condition. During the acute inflammatory phase, HE staining revealed inflammatory changes in the lung tissues of both Nintedanib groups, but the pathology was less severe than in the radiation group, with the high-dosage group showing more significant reduction. Serum levels of IL-6, TNF-α and TGF-β1 were significantly reduced (P < 0.05), suggesting that Nintedanib can decrease the expression of serum inflammatory factors. The percentage of Smad2-positive area in the low and high-dosage Nintedanib groups was (7.395 ± 0.90)% and (5.577 ± 1.56)%, respectively, both significantly lower than the radiation group (P < 0.05). At 3 months post-radiation, Masson's trichrome staining showed that the Ashcroft score in the Nintedanib groups was significantly lower than in the radiation group (P < 0.05). There were statistically significant differences between the low and high-dosage groups in the percentage of Smad2 and αSMA-positive areas and the levels of serum TGF-β1 (all P < 0.05), and both were significantly lower compared to the radiation group (P < 0.05). (1) Nintedanib can improve the general condition of mice with acute and chronic radiation-induced lung injury and reduce pathological damage to lung tissue. (2) Nintedanib may exert a protective effect on mice with acute and chronic radiation-induced lung injury by downregulating the TGF-β1/Smad2 signaling pathway, thereby inhibiting inflammatory and fibrotic responses.

Background Radiation cystitis (RC) is a major complication of pelvic radiotherapy, leading to inflammation, vascular damage, and fibrosis. While mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) show promise in regenerative medicine, their therapeutic effects on RC remain unclear. This study evaluates the efficacy of human umbilical cord MSC-EVs (huMSC-EVs) in mitigating Radiation-induced bladder damage. Methods Animal models of RC were established using 20 Gy pelvic irradiation. Forty-four female Sprague-Dawley rats were divided into four groups: negative control (NC, no radiation), positive control (PC, radiation only), local treatment (LT, huMSC-EVs injected into the bladder wall), and systemic treatment (ST, intravenous huMSC-EVs). Bladder function and compliance were assessed via metabolic cage and urodynamic studies (UDS) at 6 and 24 weeks. Histopathological changes and inflammatory cytokine levels were evaluated at multiple time points. Results Administration of huMSC-EVs significantly improved urinary frequency and hematuria. Histological analysis showed reduced urothelial disintegration and edema in the early phase, and improved urothelial integrity, reduced hyperplasia and vascular lesions, and restored bladder architecture in the late phase, in the treated groups. UDS demonstrated preserved bladder compliance and voiding efficiency in LT rats, with significantly higher voided volume ( p  < 0.01) and lower post-voiding residue ( p  < 0.05) compared to the PC group 24 weeks post-irradiation. Pro-inflammatory cytokines TNF-α, IL-1ß, and IL-6 were markedly lowered and their levels were similar to the non-radiated NC group in LT-treated rats ( p  = 1.00, p  = 0.22, p  = 0.16), 24 weeks post-irradiation. Conclusions Local huMSC-EVs therapy effectively reduces RC-related bladder injury and preserves function, likely by modulating inflammatory response and epithelial regeneration. These findings highlight huMSC-EVs as a promising strategy to prevent chronic RC, warranting further clinical exploration.

Radiation-induced pulmonary fibrosis is a common disease and has a poor prognosis owing to the progressive breakdown of gas exchange regions in the lung. Recently, a novel strategy of administering mesenchymal stem cells for pulmonary fibrosis has achieved high therapeutic efficacy. In the present study, we attempted to use human adipose tissue-derived mesenchymal stem cells to prevent disease in Sprague-Dawley rats that received semi-thoracic irradiation (15 Gy). To investigate the specific roles of mesenchymal stem cells in ameliorating radiation-induced pulmonary fibrosis, we treated control groups of irradiated rats with human skin fibroblasts or phosphate-buffered saline. After mesenchymal stem cells were infused, host secretions of hepatocyte growth factor (HGF) and prostaglandin E2 (PGE2) were elevated compared with those of the controls. In contrast, tumour necrosis factor-alpha (TNF-α) and transforming growth factor-beta1 (TGF-β1) levels were decreased after infusion of mesenchymal stem cells. Consequently, the architecture of the irradiated lungs was preserved without marked activation of fibroblasts or collagen deposition within the injured sites. Moreover, mesenchymal stem cells were able to prevent the irradiated type II alveolar epithelial cells from undergoing epithelial-mesenchymal transition. Collectively, these data confirmed that mesenchymal stem cells have the potential to limit pulmonary fibrosis after exposure to ionising irradiation.