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Due to immunosuppressive properties and confirmed tropism towards cancer cells mesenchymal stromal cells (MSC) have been used in many trials. In our study we used these cells as carriers of IL-12 in the treatment of mice with primary and metastatic B16-F10 melanomas. IL-12 has confirmed anti-cancer activity, induces a strong immune response against cancer cells and acts as an anti-angiogenic agent. A major limitation of the use of IL-12 in therapy is its systemic toxicity. The aim of the work was to develop a system in which cytokine may be administered intravenously without toxic side effects. In this study MSC were used as carriers of the IL-12. We confirmed antitumor effectiveness of the cells secreting IL-12 (MSC/IL-12) in primary and metastatic murine melanoma models. We observed inhibition of tumor growth and a significant reduction in the number of metastases in mice after MSC/IL-12 administration. MSC/IL-12 decreased vascular density and increased the number of anticancer M1 macrophages and CD8+ cytotoxic T lymphocytes in tumors of treated mice. To summarize, we showed that MSC are an effective, safe carrier of IL-12 cytokine. Administered systemically they exert therapeutic properties of IL-12 cytokine without toxicity. Therapeutic effect may be a result of pleiotropic (proinflammatory and anti-angiogenic) properties of IL-12 released by modified MSC.

Simple Summary The growth of tumors depends on the development of their abnormal vasculature. Targeting tumor blood vessels could be an effective approach to anti-cancer therapy. One of the strategies is targeting existing tumor blood vessels—anti-vascular therapy. Anti-vascular drugs destroy the core of the tumor but leave the rim of viable cells at the periphery of the tumor. These viable cells, so-called tumor rim cells, are resistant to elimination and are responsible for tumor regrowth and therapy failure. Our work aimed to find the correct sequencing of the vascular disrupting agent—DMXAA with radiotherapy (brachytherapy) to improve therapeutic efficacy. Throughout the manuscript, we attempt to explain the importance of immune cells’ activation in such therapy and prove the significance of sequential therapeutic agent administration. Abstract Vascular disrupting agents (VDAs), such as DMXAA, effectively destroy tumor blood vessels and cause the formation of large areas of necrosis in the central parts of the tumors. However, the use of VDAs is associated with hypoxia activation and residues of rim cells on the edge of the tumor that are responsible for tumor regrowth. The aim of the study was to combine DMXAA with radiotherapy (brachytherapy) and find the appropriate administration sequence to obtain the maximum synergistic therapeutic effect. We show that the combination in which tumors were irradiated prior to VDAs administration is more effective in murine melanoma growth inhibition than in either of the agents individually or in reverse combination. For the first time, the significance of immune cells’ activation in such a combination is demonstrated. The inhibition of tumor growth is linked to the reduction of tumor blood vessels, the increased infiltration of CD8+ cytotoxic T lymphocytes and NK cells and the polarization of macrophages to the cytotoxic M1 phenotype. The reverse combination of therapeutic agents showed no therapeutic effect and even abolished the effect of DMXAA. The combination of brachytherapy and vascular disrupting agent effectively inhibits the growth of melanoma tumors but requires careful planning of the sequence of administration of the agents.

Radiotherapy (RT) is one of the major methods of cancer treatment. RT destroys cancer cells, but also affects the tumor microenvironment (TME). The delicate balance between immunomodulation processes in TME is dependent, among other things, on a specific radiation dose. Despite many studies, the optimal dose has not been clearly determined. Here, we demonstrate that brachytherapy (contact radiotherapy) inhibits melanoma tumor growth in a dose-dependent manner. Doses of 10Gy and 15Gy cause the most effective tumor growth inhibition compared to the control group. Brachytherapy, at a single dose of &ge, 5Gy, resulted in reduced tumor blood vessel density. Only a dose of 10Gy had the greatest impact on changes in the levels of tumor-infiltrating immune cells. It most effectively reduced the accumulation of protumorogenic M2 tumor-associated macrophages and increased the infiltration of cytotoxic CD8+ T lymphocytes. To summarize, more knowledge about the effects of irradiation doses in anticancer therapy is needed. It may help in the optimization of RT treatment. Our results indicate that a single dose of 10Gy leads to the development of a robust immune response. It seems that it is able to convert a tumor microenvironment into an &ldquo, in situ&rdquo, vaccine and lead to a significant inhibition of tumor growth.

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Objectives Application of non‐invasive imaging methods plays an important role in the assessment of cellular therapy effects in peripheral artery disease. The purpose of this work was to evaluate the kinetics of MRI‐derived parameters characterizing ischaemic hindlimb muscle after administration of human mesenchymal stromal cells derived from adipose tissue (hADSC) in mice. Materials and methods MRI experiments were performed on a 9.4T Bruker system. The measurement protocol included transverse relaxation time mapping and diffusion tensor imaging. The monitoring period encompassed 14 days after femoral artery ligation and subsequent cell administration. The effect of hADSC transplantation was compared with the effect of normal human dermal fibroblasts (NHDFs) and phosphate‐buffered saline injection. Results The most significant differences between the hADSC group and the remaining ones were observed around day 3 after ischaemia induction (increased transverse relaxation time in the hADSC group in comparison with the control group) and around day 7 (increased transverse relaxation time and decreased third eigenvalue of the diffusion tensor in the hADSC group in comparison with the control and NHDF groups) at the site of hADSC injection. Histologically, it was associated with increased macrophage infiltration at days 3‐7 and with the presence of small regenerating fibres in the ischaemic tissue at day 7. Conclusions Our results underscore the important role of macrophages in mediating the therapeutic effects of hADSCs and confirm the huge potential of magnetic resonance imaging in monitoring of cellular therapy effects.

Neovascularization, the process of new blood vessels formation in response to hypoxia induced signals, is an essential step during wound healing or ischemia repair. It follows as a cascade of consecutive events leading to new blood vessels formation and their subsequent remodeling to a mature and functional state, enabling tissue regeneration. Any disruption in consecutive stages of neovascularization can lead to chronic wounds or impairment of tissue repair. In the study we try to explain the biological basis of accelerated blood vessels formation in ischemic tissue after adipose tissue-derived stromal cells (ADSCs) administration. Experiments were performed on mouse models of hindlimb ischemia. We have evaluated the level of immune cells (neutrophils, macrophages) infiltration. The novelty of our work was the assessment of bone marrow-derived stem/progenitor cells (BMDCs) infiltration and their contribution to the neovascularization process in ischemic tissue. We have noticed that ADSCs regulated immune response and affected the kinetics and ratio of macrophages population infiltrating ischemic tissue. Our research revealed that ADSCs promoted changes in the morphology of infiltrating macrophages and their tight association with forming blood vessels. We assume that recruited macrophages may take over the role of pericytes and stabilize the new blood vessel or even differentiate into endothelial cells, which in consequence can accelerate vascular formation upon ADSCs administration. Our findings indicate that administration of ADSCs into ischemic muscle influence spatio-temporal distribution of infiltrating cells (macrophages, neutrophils and BMDCs), which are involved in each step of vascular formation, promoting effective ischemic tissue neovascularization.

Background Adipose-derived mesenchymal stromal cells (ADSCs) are multipotent stromal cells. The cells secrete a number of cytokines and growth factors and show immunoregulatory and proangiogenic properties. Their properties may be used to repair damaged tissues. The aim of our work is to explain the muscle damage repair mechanism with the utilization of the human adipose-derived mesenchymal stromal cells (hADSCs). Methods For the hADSCs isolation, we used the subcutaneous adipose tissue collected during the surgery. The murine hind limb ischemia was used as a model. The unilateral femoral artery ligation was performed on 10–12-week-old male C57BL/6NCrl and NOD SCID mice. The mice received PBS− (controls) or 1 × 106 hADSCs. One, 3, 7, 14 and 21 days after the surgery, we collected the gastrocnemius muscles for the immunohistochemical analysis. The results were analyzed with relevant tests using the Statistica software. Results The retention time of hADSCs in the limb lasted about 14 days. In the mice receiving hADSCs, the improvement in the functionality of the damaged limb occurred faster than in the control mice. More new blood vessels were formed in the limbs of the mice receiving hADSCs than in limbs of the control mice. hADSCs also increased the infiltration of the macrophages with the M2 phenotype (7-AAD−/CD45+/F4/80+/CD206+) into the ischemic limbs. hADSCs introduced into the limb of mice secreted interleukin-6. This cytokine stimulates the emergence of the proangiogenic M2 macrophages, involved, among others, in the repair of a damaged tissue. Both macrophage depletion and IL-6 blockage suppressed the therapeutic effect of hADSCs. In the mice treated with hADSCs and liposomes with clodronate (macrophages depletion), the number of capillaries formed was lower than in the mice treated with hADSCs alone. Administration of hADSCs to the mice that received siltuximab (human IL-6 blocker) did not cause an influx of the M2 macrophages, and the number of capillaries formed was at the level of the control group, as in contrast to the mice that received only the hADSCs. Conclusions The proposed mechanism for the repair of the damaged muscle using hADSCs is based on the activity of IL-6. In our opinion, the cytokine, secreted by the hADSCs, stimulates the M2 macrophages responsible for repairing damaged muscle and forming new blood vessels.

Vascular disrupting agents as DMXAA inhibit tumor growth only for a short period of time followed by rapid tumor regrowth. Among others, hypoxia and presence of transcription factor HIF-1α are responsible for tumors regrowth. The aim of our study was to investigate the inhibition of murine melanoma growth by combining two agents: anti-vascular - DMXAA and the HIF-1α inhibitor - digoxin and explaining the mechanism of action of this combination. After DMXAA treatment tumor size was reduced only for a limited time. After 7 days regrowth of tumors was observed and number of vessels was increased especially in tumor’s peripheral areas. DMXAA also induced an influx of immune cells: macrophages, CD8+ cytotoxic lymphocytes, NK cells, CD4+ lymphocytes. Administration of digoxin alone inhibited the growth of tumors. Administration of both agents in the proper sequence significantly inhibited the regrowth of tumors better than either agents alone. Combination therapy reduced number of newly formed vessels. In tumors of mice treated with combination therapy, the number of macrophages M1, CD8+ cytotoxic lymphocytes, NK cells and to a lesser extent CD4+ cells was increased. The combination of anti-vascular agents with HIF-1α inhibitors appears to be an effective therapeutic option.