Chronic radiation cystitis (CRC) is a disabling late adverse effect of pelvic irradiation, characterized by urothelial barrier loss, persistent inflammation, vascular alteration, and progressive fibrosis. No curative treatment exists. Mesenchymal stromal cells (MSCs) are investigated for their regenerative potential, however their long-term mechanisms of action in CRC remain incompletely elucidated. CRC was induced in rats by localized bladder irradiation (40 Gy). Animals were randomized into unirradiated controls, irradiated controls, and irradiated MSC-treated groups. The treated group received three intravenous injections of adipose-derived MSCs at 4.5, 5.0, and 5.5 months post-irradiation, during the pre-chronic phase. Bladders were analyzed up to 18 months post-irradiation by immunostaining and RT-qPCR for urothelial differentiation (Upk1a, Upk1b, Upk2, Upk3a, Upk3b), epithelial proliferation (CK14⁺/PCNA⁺) and fibrosis (collagen I and III). Immune activation (CD45⁺ leukocytes, neutrophils, mast cells, Gata3, Th1, Th2) was analyzed by flow cytometry and vascular integrity by cystoscopy and Cspg4, VegfA expression. At 18 months post-irradiation, irradiated bladders showed a 90

Hematopoietic stem cells (HSCs) are the rare cells responsible for the lifelong curative effects of hematopoi-etic cell (HC) transplantation. The demand for clinical-grade HSCs has increased significantly in recent de-cades, leading to major difficulties in treating patients. A promising but not yet achieved goal is the generation of HSCs from pluripotent stem cells. Here, we have obtained vector-and stroma-free transplantable HSCs by differentiating human induced pluripotent stem cells (hiPSCs) using an original one-step culture system. After injection into immunocompromised mice, cells derived from hiPSCs settle in the bone marrow and form a robust multilineage hematopoietic population that can be serially transplanted. Single-cell RNA sequencing shows that this repopulating activity is due to a hematopoietic population that is transcriptionally similar to human embryonic aorta-derived HSCs. Overall, our results demonstrate the generation of HSCs from hiPSCs and will help identify key regulators of HSC production during human ontogeny.

Background Cellular therapy seems to be an innovative therapeutic alternative for which mesenchymal stem cells (MSCs) have been shown to be effective for interstitial and hemorrhagic cystitis. However, the action of MSCs on chronic radiation cystitis (CRC) remains to be demonstrated. The aim of this study was to set up a rat model of CRC and to evaluate the efficacy of MSCs and their mode of action. Methods CRC was induced by single-dose localized irradiation of the whole bladder using two beams guided by tomography in female Sprague–Dawley rat. A dose range of 20–80 Gy with follow-up 3–12 months after irradiation was used to characterize the dose effect and the kinetics of radiation cystitis in rats. For the treatment, the dose of 40 Gy was retained, and in order to potentiate the effect of the MSCs, MSCs were isolated from adipose tissue. After expansion, they were injected intravenously during the pre-chronic phase. Three injections of 5 million MSCs were administered every fortnight. Follow-up was performed for 12 months after irradiation. Results We observed that the intensity and frequency of hematuria are proportional to the irradiation dose, with a threshold at 40 Gy and the appearance of bleeding from 100 days post-irradiation. The MSCs reduced vascular damage as well as damage to the bladder epithelium. Conclusions These results are in favor of MSCs acting to limit progression of the chronic phase of radiation cystitis. MSC treatment may afford real hope for all patients suffering from chronic radiation cystitis resistant to conventional treatments.

During radiotherapy, the radiation beam can affect healthy tissues in the field of irradiation, even if it specifically targets the tumor, causing sequelae in 10% of patients that can occur up to 20 years after treatment.In the abdominal-pelvic area, this results in severe pain and extremely disabling functional disorders of the bladder and bowel.Current treatments are mainly symptomatic, and some patients do not respond.For several years, Institut de Radioprotection et Sureté Nucléaire has been conducting research on cell therapy strategies using Mesenchymal Stromal Cells to repair radiation-damaged tissue.This experimental research, which is currently being carried out on different animal models, indicates that in the abdominal-pelvic area, Mesenchymal Stromal Cells stimulate the repair process after irradiation.They have thus made it possible to offer this treatment in a compassionate setting to human victims of the radiotherapy accident that occurred at the Jean Monnet Hospital in Epinal (Vosges, France).Four patients suffering from severe pelvic side effects due to excessive radiation dose after conformal radiotherapy for prostate adenocarcinoma received intravenous injections of allogeneic mesenchymal stromal cells.For treated patients, mesenchymal Stromal Cell therapy was effective on pain, diarrhea, hemorrhage, inflammation, fibrosis and limited fistulization.No toxicity was observed.We are now starting inclusion in a clinical research protocol of phase 2, for patients with post-radiation abdominal and pelvic complications who have not seen their symptoms improve after conventional treatments (NCT 02814864, PRISME).Patients included in this trial will receive injections of allogeneic Mesenchymal Stromal Cell (from intrafamily donors) and will be followed for 12 months at Hospital St-Antoine (Paris, France).At the end of this period, if the efficacy of the treatment is proven, a phase III trial including a larger number of patients over a longer period will be used to confirm the therapeutic properties of this treatment.

The demand for allogeneic Haematopoietic Stem Cells (HSCs) has significantly increased over the past decades with no parallel increase of the HSC offer. Despite progress, the production of clinical grade HSCs from non-hematopoietic sources is yet impossible.We recently developed a dedicated and tractable one step, transgene-free and stroma-free protocol to produce serially-transplantable HSCs in immunocompromised recipient mice from human-induced pluripotent stem cells. This procedure is based on the differentiation of embryoid bodies with morphogens and cytokines to generate HSCs over a 17-day culture period (Guyonneau et al., in preparation).Single cell RNA sequencing of the culture at different time points were compared to published scRNAseq data from the human embryo haematopoietic aorta (AGM), where the first HSCs are produced. The endothelial cells produced resemble those of the AGM with an APLNR+ “veinous” subcluster and a GJA5+ “arteriolar” subcluster suggesting that the graft-capable cells are close to the nascent HSCs or hemogenic endothelial cells. This means that our system faithfully reproduces the developmental events responsible for the generation of the earliest HSCs.This analysis also revealed that our culture contains cell derivatives from the 3 germ layers and extra-embryonic structures. As the presence of both intra and extra-embryonic populations is uncommon, we investigated the role of the plasma source in the diversity of cell types obtained. Our regular plasma was compared to BSA and to another plasma, viro-attenuated and prion reduced. Changing the protein source has a strong impact since the two latter conditions are lacking the ectodermic and extra-embryonic cell populations. In addition, these alternative protein sources seem to accelerate cell differentiation which could impact the ability of HSCs to perform a long-term engraftment.

Cystitis is a bladder disease with a high rate of prevalence in the world population. This report focuses on Interstitial Cystitis (IC), Hemorrhagic Cystitis (HC) and Chronic Radiation Cystitis. These pathologies have different etiologies, but they share common symptoms, for instance, pain, bleeding, and a contracted bladder. Overall, treatments are quite similar for abacterial cystitis, and include bladder epithelium protective or anti-inflammatory agents, alleviating pain and reducing bleeding. This review summarizes the mechanisms that the pathologies have in common, for instance, bladder dysfunction and inflammation. Conversely, some mechanisms have been described as present in only one pathology, such as neural regulation. Based on these specificities, we propose identifying a mechanism that could be common to all the above-mentioned pathologies.

Chronic radiation cystitis (CRC) is a consequence of pelvic radiotherapy and affects 5–10% of patients. The pathology of CRC is without curative treatment and is characterized by incontinence, pelvic pain and hematuria, which severely degrades patients’ quality of life. Current management strategies rely primarily on symptomatic measures and have certain limitations. Thanks to a better understanding of the pathophysiology of radiation cystitis, studies targeting key manifestations such as inflammation, neovascularization and cell atrophy have emerged and are promising avenues for future treatment. However, the mechanisms of CRC are still better described in animal models than in human models. Preclinical studies conducted to elucidate the pathophysiology of CRC use distinct models and are most often limited to specific processes, such as fibrosis, vascular damage and inflammation. This review presents a synthesis of experimental studies aimed at improving our understanding of the molecular mechanisms at play and identifying key processes in CRC.

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.

La cystite radique chronique est une pathologie consécutive d'une irradiation pelvienne caractérisée, par une inflammation chronique évoluant parfois vers une fibrose, avec des symptômes tels que des douleurs et des saignements. Des études précédentes sur la rectite radique ont montré que les cellules souches mésenchymateuses peuvent moduler l'inflammation chronique et la fibrose après l'irradiation. Notre étude était divisée en deux parties, la modélisation de la cystite radique chronique chez le rat puis l'effet du traitement par les cellules souches mésenchymateuses. La cystite radique chronique a été induit par une irradiation localisée de l'intégralité de la vessie à l'aide du Small Animal Radiation Research Platform (SARRP). Une gamme de doses de 20 à 80 Gy a été délivrée et un suivi de 3 à 12 mois après l'irradiation a été réalisé. Pour le traitement nous avons retenu la dose de 40 Gy, suivie 4 mois après l'irradiation d'une injection intraveineuse de 5 millions de cellules souches mésenchymateuses, administrée toutes les deux semaines (trois injections en tout). Un suivi physiologique, histologique et moléculaire a été réalisé pendant 12 mois après l'irradiation. Les résultats ont montré l'apparition de la cystite radique chronique dès 6 mois après l'irradiation, avec une inflammation chronique, une hématurie, une désorganisation de l'urothélium et une fibrose, augmentant avec le temps. L'analyse transcriptomique a indiqué un profil en faveur d'une inflammation chronique par rapport au témoin non irradié, avec la surexpression des gènes CCL5 (5 fois ; valeur p < 0,05), IL1β (7 fois ; p < 0,001) et IL6 (7,5 fois ; p < 0,01), dès 6 mois après l'irradiation. La fibrose était observable à partir de 6 mois après l'irradiation et augmentait proportionnellement au temps et à la dose d'irradiation. Des lésions de l'urothélium (basées sur les zones sans urothélium avec une diminution de l'uroplakine III) apparaissent à 6 mois après l'irradiation. À dix mois, une régénération de l'urothélium semblait mise en évidence par la surexpression de la cytokératine 5 (marqueur des cellules souches basales). Cependant, cette régénération paraissait défectueuse, puisque à 12 mois, une hyperplasie a été confirmée chez les rats irradiés (p < 0,01). Nous avons observé que l'intensité et la fréquence de l'hématurie étaient proportionnelles à la dose d'irradiation avec un seuil à 40 Gy et l'apparition de saignements à partir de 60 jours après l'irradiation. Le traitement par les cellules souches mésenchymateuses retarde l'apparition des saignements jusqu'à 300 jours après l'irradiation. Ces résultats sont en corrélation avec la réduction des lésions vasculaires observables jusqu'à 12 mois après l'irradiation. Le traitement par les cellules souches mésenchymateuses semble diminuer l'hyperplasie par rapport au témoin irradié. Il permet également de retarder l'hématurie, de diminuer les lésions vasculaires et l'hyperplasie. L'analyse de l'effet des cellules souches mésenchymateuses sur l'inflammation et la régénération de l'urothélium est en cours.

The main difficulty of radiotherapy is to destroy cancer cells without depletion of healthy tissue [...].

La cystite radique chronique est une maladie parfois consécutive des radiothérapies pelviennes. Elle est caractérisée par une inflammation chronique, des lésions vasculaires et une hypoxie des tissus évoluant vers la fibrose. En clinique, la cystite radique chronique entraîne des douleurs, des saignements, de l’incontinence et dans les cas les plus graves des fistules. Il n’existe pas de traitement curatif. Nous proposons de tester une thérapie cellulaire utilisant les cellules stromales mésenchymateuses comme nouvelle approche thérapeutique. Nos études précédentes sur la rectite radique ont montré que les cellules stromales mésenchymateuses peuvent moduler l’inflammation chronique et la fibrose tissulaire après irradiation. Notre étude est divisée en deux parties, la modélisation de la cystite radique chronique puis l’effet d’un traitement par les cellules stromales mésenchymateuses. La modélisation préclinique de la cystite radique chronique chez le rat a été réalisée par irradiation localisée guidée par l’imagerie scanographique de la vessie entre 20 et 80 Gy avec un suivi de 3 à 15 mois après l’irradiation. L’évolution de la cystite radique chronique a été suivie au niveau de l’expression des gènes, des protéines, des paramètres histologiques et fonctionnels. La mesure des paramètres urinaires a révélé une hématurie transitoire augmentant avec le temps et la dose d’irradiation sans diminution du volume urinaire jusqu’à 6 mois. L’analyse transcriptomique indiquait une inflammation aiguë à 3 mois (augmentation de l’expression des gènes codant pour le chemokine [C-C motif] ligand [CCL]-2, CCL5, le tumour necrosis factor alpha [TNFα] et l’interleukine [IL]-1β). Elle était accompagnée d’une régénération tissulaire et vasculaire (augmentation de l’expression génique de l’epidermal growth factor [EGF] et du vascular endothelial growth factor [VEGF]) couplée à un remodelage de la matrice extracellulaire avec l’augmentation de l’expression génique de la métalloprotease MMP2, des inhibiteurs TIMP1/2/4, des collagènes Col1α2, Col3α1 et du protéoglycane Cspg4. A 6 mois, une deuxième phase d’inflammation (augmentation de l’expression des gènes codant pour CCL5, IL1β, IL6 et l’hypoxia-inducible factor 1-alpha [HIF1α]) a été observée. Elle était corrélée avec une désorganisation de l’urothélium mais sans régénération tissulaire et vasculaire, ni de remodelage de la matrice extracellulaire. Ces premiers résultats sont en faveur de la mise en place d’une cystite radique chronique 6 mois après l’irradiation, caractérisée par une inflammation chronique, des signes d’hypoxie, d’hématurie et de désorganisation de l’urothélium, sans diminution du volume urinaire. L’analyse de la cinétique sur des temps plus longs permettra de caractériser l’évolution vers une cystite radique chronique confirmée accompagnée de fibrose. La seconde phase de l’étude est en cours pour évaluer si le traitement par les cellules stromales mésenchymateuses pourrait limiter la fibrogénèse en inhibant les voies inflammatoires et en augmentant l’angiogenèse. Nos résultats fourniront des données concernant le potentiel antifibrotique des cellules stromales mésenchymateuses et le traitement de la cystite radique par les cellules stromales mésenchymateuses.

Les mécanismes des lésions radio-induites tardives sont la résultante de phénomènes multiples et complexes, avec de nombreux acteurs cellulaires et tissulaires intriqués. Le continuum biologique entre effets aigus et effets tardifs après irradiation sera décrit, avec en premier lieu une rupture d’homéostasie qui conduit à des redistributions cellulaires. De nouveaux éclairages sur la toxicité tardive seront enfin abordés. La radiosensibilité individuelle est un facteur primordial dans le développement de toxicité tardive, et les cliniciens ont un besoin urgent de disposer de tests prédictifs qui permettraient de proposer une radiothérapie réellement personnalisée. La mise au point est faite sur les différents tests fonctionnels et génétiques en cours de validation. La prise en charge des effets secondaires de la radiothérapie reste un problème fréquent pour l’oncologue radiothérapeute, et un point est fait sur les traitements qui peuvent être proposés dans certaines situations cliniques particulières. Enfin, une prise en charge innovante est développée pour les patients atteints d’effets secondaires importants après radiothérapie pelvienne, la greffe de cellules souches mésenchymateuses, avec la présentation du protocole « Prisme » actuellement ouvert au recrutement des patients.

Les proctopathies et les cystites radiques sont des maladies consécutives aux radiothérapies pelviennes qui peuvent être réfractaires à une thérapie standard. Notre groupe a confirmé dans des modèles animaux et lors d’un essai clinique de phase 1 que la thérapie cellulaire représente une option sûre qui peut apporter un bénéfice thérapeutique lorsque les autres traitements ont échoué. Quatre patients souffrant d’effets secondaires pelviens graves en raison d’une dose excessive d’irradiation après une radiothérapie conformationnelle pour un adénocarcinome de la prostate (accident d’Épinal) ont reçu des injections intraveineuses de cellules stromales mésenchymateuses allogéniques. L’état clinique des patients s’est amélioré après l’injection de cellules stromales mésenchymateuses. Deux patients ont révélé une réponse clinique confirmée pour la douleur et l’hémorragie. La fréquence des diarrhées douloureuses a diminué de 6 jours à 3 jours après la première injection et 2 jours après la seconde injection chez un patient. Un processus de fistulisation a pu être arrêté chez un patient, ce qui a permis une rémission stable pendant plus de 3 ans. Une modulation des sous-populations de lymphocytes vers un schéma de régulation et une diminution des cellules T activées a accompagné la réponse clinique. La thérapie par les cellules stromales mésenchymateuses a été efficace sur la douleur, la diarrhée, l’hémorragie, l’inflammation, la fibrose et la fistulisation. Aucune toxicité n’a été observée. Un essai clinique de phase 2 est en cours d’inclusion pour des patients souffrant de complications abdominales et pelviennes après radiothérapie qui n’ont pas vu leurs symptômes s’améliorer après les traitements classiques (NCT02814864, essai évaluant l’efficacité des injections systémiques de cellules stromales mésenchymateuses pour le traitement des complications abdominales et pelviennes graves et chroniques réfractaires au traitement standard, induites par la radiothérapie [Prisme]). Il implique la participation de six services de radiothérapie pour le recrutement de 12 patients. Ils seront tous pris en charge et suivis dans le service d’hématologie de l’hôpital Saint-Antoine. Les cellules seront préparées dans deux centres (EFS Mondor et CTSA Clamart) appartenant au réseau national EcellFrance de médecine régénératrice et de thérapie cellulaire à base de cellules stromales mésenchymateuses. Les critères d’éligibilité sont un grade supérieur à 2 pour la rectorragie ou l’hématurie à l’inclusion et l’absence de cancer actif. Chaque patient recevra trois injections de cellules stromales mésenchymateuses à 7 jours d’intervalle. Les patients seront suivis sur une période de 12 mois. L’objectif principal est une diminution d’un grade sur l’échelle Late Effects Normal Tissue ; Subjective, Objective, Management, Analytic (LENT SOMA) pour la rectorragie ou l’hématurie. L’objectif secondaire est de réduire la fréquence des diarrhées, la consommation d’analgésiques, la douleur et l’amélioration de la qualité de vie.

Background & Aim Chronic radiocystitis (CRC) is a pathology resulting from irradiation of the pelvic area without long term effective treatment. CRC is characterized by chronic inflammation progressing to fibrosis, fistulas and cystectomy in the most severe cases. Our laboratory have previously demonstrated that MSC treatment reverse similar damages in irradiated colon. Furthermore in a clinical phase 1/2 treatments using MSCs for hemorrhagic cystitis, which is pathology similar to CRC, was sucessfull (Ringden O et al., 2007). Based on these previous results, our objective is to evaluate whether adipose derived mesenchymal stem cells (MSCs) could be an innovative treatment of CRC. Methods, Results & Conclusion Preclinical modeling of CRC in rats (Sprague Dawley) was established by irradiating the entire bladder with a single dose of 40 Gray using the Small Animal Radiation Research Platform (SARRP, figure 1)). At four months after irradiation, animals received a treatment consisting in tree intravenous injections of 5 million of MSCs every two weeks. After irradiation and treatment, a physiological, histological and molecular follow-up was performed on 14 months (figure 2). Results have shown, without MSC treatment, an initiation of CRC at 6 months, with chronic inflammation, hypoxia, hematuria, disorganization of the urothelium and fibrosis. Analysis of urinary parameters has revealed hematuria increasing with time. Transcriptomic analysis indicates chronic inflammation (IL1β, CCL2, IL6) and hypoxia (HIF1α). Histological observations reveal a disorganization of the urothelium with loss of superficial cells and fibrosis (figure 3). Study is in progress to evaluate whether MSC treatment could limite fibrogenesis by inhibiting the inflammatory pathways and increasing angiogenesis, in our model CRC preclinical model. Our results will provide data regarding the anti-fibrotic potential of MSCs and could support their use in the treatment of CRC. Ringden O, Uzunel M, Sundberg B, et al. Tissue repair using allogeneic mesenchymal stem cells for hemorrhagic cystitis, pneumomediastinum and perforated colon. Leukemia 2007: 21: 2271–2276. Chronic radiocystitis (CRC) is a pathology resulting from irradiation of the pelvic area without long term effective treatment. CRC is characterized by chronic inflammation progressing to fibrosis, fistulas and cystectomy in the most severe cases. Our laboratory have previously demonstrated that MSC treatment reverse similar damages in irradiated colon. Furthermore in a clinical phase 1/2 treatments using MSCs for hemorrhagic cystitis, which is pathology similar to CRC, was sucessfull (Ringden O et al., 2007). Based on these previous results, our objective is to evaluate whether adipose derived mesenchymal stem cells (MSCs) could be an innovative treatment of CRC. Preclinical modeling of CRC in rats (Sprague Dawley) was established by irradiating the entire bladder with a single dose of 40 Gray using the Small Animal Radiation Research Platform (SARRP, figure 1)). At four months after irradiation, animals received a treatment consisting in tree intravenous injections of 5 million of MSCs every two weeks. After irradiation and treatment, a physiological, histological and molecular follow-up was performed on 14 months (figure 2).

Mesenchymal Stem cells (MSCs) has fascinating immunomodulatory effect in vitro and in vivo. This effect has been documented by interesting researches worldwide. However the protocols of MSCs culture are different. This difference is translated on different results regarding the mediators as well as on potency of immunomodulatory effect in both vitro and in vivo. In this article we will analyze and discussing the effect of culture environment on MSC immunomodulatory effect.

Background & Aim Healthy tissues surrounding pelvic tumours may be impaired during radiotherapy (RT) and could lead to chronic gastrointestinal complications with substantial mortality. Injection of Adipose-derived Mesenchymal Stromal Cells (Ad-MSC) represents a promising therapeutic strategy. However, many stem cell clinical trials do not confer expected beneficial effect, suggesting a real need to accelerate research towards the successful clinical application. We hypothesized that heparan sulfate (HS)-mimetic injections that restore the extracellular matrix network and enhance the biological activity of growth factors, associated with local injection of MSC protected in a hydrogel that improves cell engraftment and cell survival, could improve the therapeutic benefit of MSC treatment. Methods, Results & Conclusion We used an experimental model of radiation proctitis developed in rats that reproduces severe colonic mucosal damages and fibrosis similar to those observed in patients treated by radiotherapy. We tested injections of HS-m, local injection through endoscopy of Ad-MSC embedded in Si-HPMC hydrogel as well as combinations of these various treatments. The therapeutic benefit was evaluated by endoscopy, histology and functional parameters as epithelial barrier were also tested. We demonstrated that hydrogel loaded-Ad-MSCs were viable, able to secrete trophic factors and responsive to the inflammatory environment. In animal model, Ad-MSC+Si-HPMC improve colonic epithelial structure and hyperpermeability. This therapeutic benefit is associated with greater engraftment of Si-HPMC-embedded Ad-MSCs in the irradiated colonic mucosa. We demonstrated that combination of HS-m to hydrogel-embedded MSC treatment enhances the therapeutic benefit of MSC therapy alone. We also demonstrated that the combined treatment favored the epithelial regenerative process. Finally, using an animal model of colonic surgery after irradiation, we demonstrated that the combined treatment improved rat survival, healing of the anastomosis and scar quality assessed by collagen deposit. In this study, we identified a new way, clinically applicable, to optimize stem-cell therapy and could be proposed to patients suffering from severe colonic defect after RT. Healthy tissues surrounding pelvic tumours may be impaired during radiotherapy (RT) and could lead to chronic gastrointestinal complications with substantial mortality. Injection of Adipose-derived Mesenchymal Stromal Cells (Ad-MSC) represents a promising therapeutic strategy. However, many stem cell clinical trials do not confer expected beneficial effect, suggesting a real need to accelerate research towards the successful clinical application. We hypothesized that heparan sulfate (HS)-mimetic injections that restore the extracellular matrix network and enhance the biological activity of growth factors, associated with local injection of MSC protected in a hydrogel that improves cell engraftment and cell survival, could improve the therapeutic benefit of MSC treatment. We used an experimental model of radiation proctitis developed in rats that reproduces severe colonic mucosal damages and fibrosis similar to those observed in patients treated by radiotherapy. We tested injections of HS-m, local injection through endoscopy of Ad-MSC embedded in Si-HPMC hydrogel as well as combinations of these various treatments. The therapeutic benefit was evaluated by endoscopy, histology and functional parameters as epithelial barrier were also tested.

Background & Aim The late adverse effects of pelvic radiotherapy concern 5 to 10% of patients, which could be life threatening. However, a clear medical consensus concerning the clinical management of such healthy tissue sequelae does not exist. Our group has demonstrated in preclinical animal models that systemic mesenchymal stromal stem cells (MSCs) injection is a promising approach for the medical management of gastrointestinal disorder after irradiation. Methods, Results & Conclusion In a phase 1 clinical trial, we have shown that the clinical status of four first patients suffering from severe pelvic side effects (Epinal accident) was improved following MSC injection (figure 1 and 2). Two patients revealed a substantiated clinical response for pain and hemorrhage after MSC therapy. The frequency of painful diarrhea diminished from 6/d to 3/d after the first and 2/d after the 2nd MSC injection in one patient. A beginning fistulization process could be stopped in one patient resulting in a stable remission for more than 3 years of follow-up. A modulation of the lymphocyte subsets towards a regulatory pattern and diminution of activated T cells accompanies the clinical response. MSC therapy was effective on pain, diarrhea, hemorrhage, inflammation, fibrosis and limited fistulization. No toxicity was observed (Table). We are now starting a clinical research protocol for patients with post-radiation abdominal and pelvic complications (figure 3) who have not seen their symptoms improve after conventional treatments (NCT02814864, Trial evaluating the efficacy of systemic MSC injections for the treatment of severe and chronic radiotherapy-induced abdomino-pelvic complications refractory to standard therapy (PRISME). It involves the participation of 6 radiotherapy services for the recruitment of 12 patients. They will all be treated and followed up in the hematology department of Saint Antoine Hospital. The cells will be prepared in two production centers (EFS Mondor and CTSA). Treatment is a suspension of allogeneic MSCs. Eligible patients must have a grade greater than 2 for rectoragy or hematuria at inclusion and absence of active cancer. Each patient receives 3 injections of MSCs at 7-day intervals. Patients will be followed up over a 12-month period. The main objective is a decrease of one grade on the LENT SOMA scale for rectorrhagia or hematuria. The secondary objective is to reduce the frequency of diarrhea; analgesic consumption, pain and improved quality of life. The late adverse effects of pelvic radiotherapy concern 5 to 10% of patients, which could be life threatening. However, a clear medical consensus concerning the clinical management of such healthy tissue sequelae does not exist. Our group has demonstrated in preclinical animal models that systemic mesenchymal stromal stem cells (MSCs) injection is a promising approach for the medical management of gastrointestinal disorder after irradiation. In a phase 1 clinical trial, we have shown that the clinical status of four first patients suffering from severe pelvic side effects (Epinal accident) was improved following MSC injection (figure 1 and 2). Two patients revealed a substantiated clinical response for pain and hemorrhage after MSC therapy. The frequency of painful diarrhea diminished from 6/d to 3/d after the first and 2/d after the 2nd MSC injection in one patient. A beginning fistulization process could be stopped in one patient resulting in a stable remission for more than 3 years of follow-up. A modulation of the lymphocyte subsets towards a regulatory pattern and diminution of activated T cells accompanies the clinical response. MSC therapy was effective on pain, diarrhea, hemorrhage, inflammation, fibrosis and limited fistulization. No toxicity was observed (Table).

Cell therapy was demonstrated of main importance in the management of normal tissue radiation damage. Preclinical and clinical trial data suggest that mesenchymal stem cells (MSCs) are a practical and safe source of cells for stem cell-based therapies of severe tissue damage consecutive to radiation overexposure. MSCs were shown to migrate to damaged tissues supporting wound healing through a “cell drug” mode of action restoring skin and gut functions after irradiation. However, technical limits associated with large-scale ex vivo expansion indicate that alternative source is required to obtain sufficient cell numbers of the appropriate lineage to treat patients with severe disease.Based on this pluripotency and unlimited expansion potential, induced pluripotent stem cells (iPSCs) are considered a promising resource for regenerative medicine. Like naturally occurring stem cells, these artificially induced cells can self-renew and develop into almost any cell in the body (pluripotency). Clinical iPSC banks of selected universal donors should allow their use for large scale allogeneic grafts. Our consortium describes a GMP-grade system to produce hiPSCs, a cell population capable of reconstituting human hematopoiesis. We demonstrate that i) hiPSC-derived hematopoietic stem cells (HSCs) from healthy donor are capable of reconstituting a functional human hematopoiesis in a radio-induced aplasia preclinical model, ii) hiPSC-derived HSCs from aplastic anemia patients or acute leukemia affected patients retain this ability.Our study prepares a new approach of autologous graft (from the cells of the patient) of cells for healthy tissue damage after radiation exposure. It could potentially pave the way to the constitution of universal banks of stem cells, which would radically increase the capacity of support and treatment of tissue exposed to high doses of ionizing radiation and in the management of chronic late radiotherapy side effects.