Exosomes secreted from bone marrow-derived mesenchymal stem cells protect the intestines from experimental necrotizing enterocolitis

Therapeutic role of extracellular vesicles from human umbilical cord mesenchymal stem cells and their wide therapeutic implications in inflammatory bowel disease and other inflammatory disorder

The chronic immune-mediated inflammatory condition known as inflammatory bowel disease (IBD) significantly affects the gastrointestinal system. While the precise etiology of IBD remains elusive, extensive research suggests that a range of pathophysiological pathways and immunopathological mechanisms may significantly contribute as potential factors. Mesenchymal stem cells (MSCs) have shown significant potential in the development of novel therapeutic approaches for various medical conditions. However, some MSCs have been found to exhibit tumorigenic characteristics, which limit their potential for medical treatments. The extracellular vesicles (EVs), paracrine factors play a crucial role in the therapeutic benefits conferred by MSCs. The EVs consist of proteins, microRNAs, and lipids, and are instrumental in facilitating intercellular communication. Due to the ease of maintenance, and decreased immunogenicity, tumorigenicity the EVs have become a new and exciting option for whole cell treatment. This review comprehensively assesses recent preclinical research on human umbilical cord mesenchymal stem cell (hUC-MSC)-derived EVs as a potential IBD therapy. It comprehensively addresses key aspects of various conditions, including diabetes, cancer, dermal injuries, neurological disorders, cardiovascular issues, liver and kidney diseases, and bone-related afflictions.

Neuropilin-1high monocytes protect against neonatal inflammation

Neonates are susceptible to inflammatory disorders such as necrotizing enterocolitis (NEC) due to their immature immune system. The timely appearance of regulatory immune cells in early life contributes to the control of inflammation in neonates, yet the underlying mechanisms of which remain poorly understood. In this study, we identified a subset of neonatal monocytes characterized by high levels of neuropilin-1 (Nrp1), termed Nrp1high monocytes. Compared with their Nrp1low counterparts, Nrp1high monocytes displayed potent immunosuppressive activity. Nrp1 deficiency in myeloid cells aggravated the severity of NEC, whereas adoptive transfer of Nrp1high monocytes led to remission of NEC. Mechanistic studies showed that Nrp1, by binding to its ligand Sema4a, induced intracellular p38-MAPK/mTOR signaling and activated the transcription factor KLF4. KLF4 transactivated Nos2 and enhanced the production of nitric oxide (NO), a key mediator of immunosuppression in monocytes. These findings reveal an important immunosuppressive axis in neonatal monocytes and provide a potential therapeutic strategy for treating inflammatory disorders in neonates.

Therapeutic Prospects of Mesenchymal Stem Cell and Their Derived Exosomes in the Regulation of the Gut Microbiota in Inflammatory Bowel Disease

Mesenchymal stem cells (MSCs) have shown great potential in the treatment of several inflammatory diseases due to their immunomodulatory ability, which is mediated by exosomes secreted by MSCs (MSC-Exs). The incidence of inflammatory bowel disease (IBD) is increasing globally, but there is currently no long-term effective treatment. As an emerging therapy, MSC-Exs have proven to be effective in alleviating IBD experimentally, and the specific mechanism continues to be explored. The gut microbiota plays an important role in the occurrence and development of IBD, and MSCs and MSC-Exs can effectively regulate gut microbiota in animal models of IBD, but the mechanism involved and whether the outcome can relieve the characteristic dysbiosis necessary to alleviate IBD still needs to be studied. This review provides current evidence on the effective modulation of the gut microbiota by MSC-Exs, offering a basis for further research on the pathogenic mechanism of IBD and MSC-Ex treatments through the improvement of gut microbiota.

Maternal circadian rhythm disruption affects neonatal inflammation via metabolic reprograming of myeloid cells

Disruption of circadian rhythm during pregnancy produces adverse health outcomes in offspring; however, the role of maternal circadian rhythms in the immune system of infants and their susceptibility to inflammation remains poorly understood. Here we show that disruption of circadian rhythms in pregnant mice profoundly aggravates the severity of neonatal inflammatory disorders in both male and female offspring, such as necrotizing enterocolitis and sepsis. The diminished maternal production of docosahexaenoic acid (DHA) and the impaired immunosuppressive function of neonatal myeloid-derived suppressor cells (MDSCs) contribute to this phenomenon. Mechanistically, DHA enhances the immunosuppressive function of MDSCs via PPARγ-mediated mitochondrial oxidative phosphorylation. Transfer of MDSCs or perinatal supplementation of DHA relieves neonatal inflammation induced by maternal rhythm disruption. These observations collectively demonstrate a previously unrecognized role of maternal circadian rhythms in the control of neonatal inflammation via metabolic reprograming of myeloid cells.

Dual role of mesenchymal stem/stromal cells and their cell-free extracellular vesicles in colorectal cancer

Colorectal cancer (CRC) is one of the main causes of cancer-related deaths. However, the surgical control of the CRC progression is difficult, and in most cases, the metastasis leads to cancer-related mortality. Mesenchymal stem/stromal cells (MSCs) with potential translational applications in regenerative medicine have been widely researched for several years. MSCs could affect tumor development through secreting exosomes. The beneficial properties of stem cells are attributed to their cell-cell interactions as well as the secretion of paracrine factors in the tissue microenvironment. For several years, exosomes have been used as a cell-free therapy to regulate the fate of tumor cells in a tumor microenvironment. This review discusses the recent advances and current understanding of assessing MSC-derived exosomes for possible cell-free therapy in CRC.

A Review of the Use of Extracellular Vesicles in the Treatment of Neonatal Diseases: Current State and Problems with Translation to the Clinic

Neonatal disorders, particularly those resulting from prematurity, pose a major challenge in health care and have a significant impact on infant mortality and long-term child health. The limitations of current therapeutic strategies emphasize the need for innovative treatments. New cell-free technologies utilizing extracellular vesicles (EVs) offer a compelling opportunity for neonatal therapy by harnessing the inherent regenerative capabilities of EVs. These nanoscale particles, secreted by a variety of organisms including animals, bacteria, fungi and plants, contain a repertoire of bioactive molecules with therapeutic potential. This review aims to provide a comprehensive assessment of the therapeutic effects of EVs and mechanistic insights into EVs from stem cells, biological fluids and non-animal sources, with a focus on common neonatal conditions such as hypoxic-ischemic encephalopathy, respiratory distress syndrome, bronchopulmonary dysplasia and necrotizing enterocolitis. This review summarizes evidence for the therapeutic potential of EVs, analyzes evidence of their mechanisms of action and discusses the challenges associated with the implementation of EV-based therapies in neonatal clinical practice.

Therapeutic potentials of mesenchymal stem cells in the treatment of inflammatory bowel disease in rats

Interleukin-1beta (IL-1β) and interleukin-17A (IL-17A) have strong pro-inflammatory activities that are involved in inflammatory bowel diseases (IBDs). Mesenchymal stem cell (MSC) therapy is considered a promising treatment for IBD. This study was performed to understand the role of rat Nlrp3 inflammasome, Hmgb1, and pro-inflammatory cytokines (IL-1β and IL-17a) in the pathogenesis of IBD. Also, to evaluate the role of human umbilical cord blood-MSCs (hUCB-MSCs) in the management of IBD. The rats were in four groups: normal controls, indomethacin-induced IBD group, indomethacin-induced IBD rats that received phosphate-buffered saline (PBS), and the IBD group that received hUCB-MSCs as a treatment. The messenger RNA (mRNA) expression levels of rat Nlrp3, Hmgb1, IL-1β, and IL-17a were evaluated by quantitative real-time polymerase chain reaction. Histopathological examination of the small intestinal tissues of the studied rats was performed. There was a significant upregulation of the rat Nlrp3, IL-1β, IL-17a mRNA expression (p < 0.001 for the three parameters), and Hmgb1 (p < 0.05) in the untreated IBD group compared to the normal control group. In the MSC-treated group, IL-1β, IL-17a, and rat Nlrp3 mRNA expression significantly decreased compared to both the untreated IBD group and PBS group (p < 0.05 for all). hUCB-MSCs ameliorated IBD in rats by downregulating the pro-inflammatory cytokines (IL-1β and IL-17a) and other inflammatory mediators such as Hmgb1 and rat Nlrp3.

Factors Influencing Neonatal Gut Microbiome and Health with a Focus on Necrotizing Enterocolitis

Maturational changes in the gut start in utero and rapidly progress after birth, with some functions becoming fully developed several months or years post birth including the acquisition of a full gut microbiome, which is made up of trillions of bacteria of thousands of species. Many factors influence the normal development of the neonatal and infantile microbiome, resulting in dysbiosis, which is associated with various interventions used for neonatal morbidities and survival. Extremely low gestational age neonates (<28 weeks' gestation) frequently experience recurring arterial oxygen desaturations, or apneas, during the first few weeks of life. Apnea, or the cessation of breathing lasting 15-20 s or more, occurs due to immature respiratory control and is commonly associated with intermittent hypoxia (IH). Chronic IH induces oxygen radical diseases of the neonate, including necrotizing enterocolitis (NEC), the most common and devastating gastrointestinal disease in preterm infants. NEC is associated with an immature intestinal structure and function and involves dysbiosis of the gut microbiome, inflammation, and necrosis of the intestinal mucosal layer. This review describes the factors that influence the neonatal gut microbiome and dysbiosis, which predispose preterm infants to NEC. Current and future management and therapies, including the avoidance of dysbiosis, the use of a human milk diet, probiotics, prebiotics, synbiotics, restricted antibiotics, and fecal transplantation, for the prevention of NEC and the promotion of a healthy gut microbiome are also reviewed. Interventions directed at boosting endogenous and/or exogenous antioxidant supplementation may not only help with prevention, but may also lessen the severity or shorten the course of the disease.

Development of a new treatment for preterm birth complications using amniotic fluid stem cell therapy

This paper describes the current status of studies and clinical trials on the use of mesenchymal stem cells (MSCs) and amniotic fluid stem cells (AFSCs) for complications of preterm birth (PTB), an urgent issue in the perinatal field. PTB is a serious challenge in clinical medicine that is increasing globally, and effective control of its complications is necessary for newborns' subsequent long life. Classical treatments are inadequate, and many patients have PTB complications. A growing body of evidence provided by translational medicine and others indicates that MSCs, and among them, the readily available AFSCs, may be useful in treating PTB complications. AFSCs are the only MSCs available prenatally and are known to be highly anti-inflammatory and tissue-protective and do not form tumors when transplanted. Furthermore, because they are derived from the amniotic fluid, a medical waste product, no ethical issues are involved. AFSCs are an ideal cell resource for MSC therapy in neonates. This paper targets the brain, lungs, and intestines, which are the vital organs most likely to be damaged by PTB complications. The evidence to date and future prospects with MSCs and AFSCs for these organs are described.

Human breast milk: A promising treatment for necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a severe gastrointestinal disorder occurring in newborns, with a mortality rate ranging from 20 % to 30 %. The existing therapeutic approaches for NEC are limited in their effectiveness. Various factors contribute to the development of NEC, including disruption of barrier function, dysregulation of the intestinal immune system, and abnormal colonization of the intestinal microbiota. Researchers have shown considerable interest in exploring the therapeutic potential of the constituents present in human breast milk (HBM) for treating NEC. HBM contains numerous bioactive components, such as exosomes, growth factors, and oligosaccharides. However, the precise mechanisms by which HBM exerts its protective effects against NEC remain incompletely understood. In this study, our objective was to comprehensively review the bioactive substances present in HBM, aiming to facilitate the development of novel therapeutic strategies for NEC.

A swift expanding trend of extracellular vesicles in spinal cord injury research: a bibliometric analysis

Extracellular vesicles (EVs) in the field of spinal cord injury (SCI) have garnered significant attention for their potential applications in diagnosis and therapy. However, no bibliometric assessment has been conducted to evaluate the scientific progress in this area. A search of articles in Web of Science (WoS) from January 1, 1991, to May 1, 2023, yielded 359 papers that were analyzed using various online analysis tools. These articles have been cited 10,842 times with 30.2 times per paper. The number of publications experienced explosive growth starting in 2015. China and the United States led this research initiative. Keywords were divided into 3 clusters, including "Pathophysiology of SCI", "Bioactive components of EVs", and "Therapeutic effects of EVs in SCI". By integrating the average appearing year (AAY) of keywords in VoSviewer with the time zone map of the Citation Explosion in CiteSpace, the focal point of research has undergone a transformative shift. The emphasis has moved away from pathophysiological factors such as "axon", "vesicle", and "glial cell" to more mechanistic and applied domains such as "activation", "pathways", "hydrogels" and "therapy". In conclusions, institutions are expected to allocate more resources towards EVs-loaded hydrogel therapy and the utilization of innovative materials for injury mitigation.

Stem cells as a therapeutic avenue for active and long-term complications of Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a devastating neonatal intestinal disease associated with significant morbidity and mortality. Although decades of research have been dedicated to understanding the pathogenesis of NEC and developing therapies, it remains the leading cause of death among neonatal gastrointestinal diseases. Mesenchymal stem cells (MSCs) have garnered significant interest recently as potential therapeutic agents for the treatment of NEC. They have been shown to rescue intestinal injury and reduce the incidence and severity of NEC in various preclinical animal studies. MSCs and MSC-derived organoids and tissue engineered small intestine (TESI) have shown potential for the treatment of long-term sequela of NEC such as short bowel syndrome, neurodevelopmental delay, and chronic lung disease. Although the advances made in the use of MSCs are promising, further research is needed prior to the widespread use of these cells for the treatment of NEC.

Necrotizing enterocolitis: recent advances in treatment with translational potential

Necrotizing enterocolitis (NEC) is one of the most prevalent and devastating gastrointestinal disorders in neonates. Despite advances in neonatal care, the incidence and mortality due to NEC remain high, highlighting the need to devise novel treatments for this disease. There have been a number of recent advancements in therapeutic approaches for the treatment of NEC; these involve remote ischemic conditioning (RIC), stem cell therapy, breast milk components (human milk oligosaccharides, exosomes, lactoferrin), fecal microbiota transplantation, and immunotherapy. This review summarizes the most recent advances in NEC treatment currently underway as well as their applicability and associated challenges and limitations, with the aim to provide new insight into the paradigm of care for NEC worldwide.

TITLE: New therapeutic approaches in pediatric diseases: Mesenchymal stromal cell and mesenchymal stromal cell-derived extracellular vesicles as new drugs

Mesenchymal Stromal Cell (MSC) clinical applications have been widely reported and their therapeutic potential has been documented in several diseases. MSCs can be isolated from several human tissues and easily expanded in vitro, they are able to differentiate in a variety of cell lineages, and they are known to interact with most immunological cells, showing immunosuppressive and tissue repair properties. Their therapeutic efficacy is closely associated with the release of bioactive molecules, namely Extracellular Vesicles (EVs), effective as their parental cells. EVs isolated from MSCs act by fusing with target cell membrane and releasing their content, showing a great potential for the treatment of injured tissues and organs, and for the modulation of the host immune system. EV-based therapies provide, as major advantages, the possibility to cross the epithelium and blood barrier and their activity is not influenced by the surrounding environment. In the present review, we deal with pre-clinical reports and clinical trials to provide data in support of MSC and EV clinical efficacy with particular focus on neonatal and pediatric diseases. Considering pre-clinical and clinical data so far available, it is likely that cell-based and cell-free therapies could become an important therapeutic approach for the treatment of several pediatric diseases.

Stem Cell Therapy in Inflammatory Bowel Disease: A Review of Achievements and Challenges

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is a group of chronic inflammatory diseases of the gastrointestinal tract. Repeated inflammation can lead to complications, such as intestinal fistula, obstruction, perforation, and bleeding. Unfortunately, achieving durable remission and mucosal healing (MH) with current treatments is difficult. Stem cells (SCs) have the potential to modulate immunity, suppress inflammation, and have anti-apoptotic and pro-angiogenic effects, making them an ideal therapeutic strategy to target chronic inflammation and intestinal damage in IBD. In recent years, hematopoietic stem cells (HSCs) and adult mesenchymal stem cells (MSCs) have shown efficacy in treating IBD. In addition, numerous clinical trials have evaluated the efficiency of MSCs in treating the disease. This review summarizes the current research progress on the safety and efficacy of SC-based therapy for IBD in both preclinical models and clinical trials. We discuss potential mechanisms of SC therapy, including tissue repair, paracrine effects, and the promotion of angiogenesis, immune regulation, and anti-inflammatory effects. We also summarize current SC engineering strategies aimed at enhancing the immunosuppressive and regenerative capabilities of SCs for treating intestinal diseases. Additionally, we highlight current limitations and future perspectives of SC-related therapy for IBD.

Mesenchymal Stem Cell-derived Exosomes: Novel Therapeutic Approach for Inflammatory Bowel Diseases

As double membrane-encapsulated nanovesicles (30-150 nm), exosomes (Exos) shuttle between different cells to mediate intercellular communication and transport active cargoes of paracrine factors. The anti-inflammatory and immunomodulatory activities of mesenchymal stem cell (MSC)-derived Exos (MSC-Exos) provide a rationale for novel cell-free therapies for inflammatory bowel disease (IBD). Growing evidence has shown that MSC-Exos can be a potential candidate for treating IBD. In the present review, we summarized the most critical advances in the properties of MSC-Exos, provided the research progress of MSC-Exos in treating IBD, and discussed the molecular mechanisms underlying these effects. Collectively, MSC-Exos had great potential for cell-free therapy in IBD. However, further studies are required to understand the full dimensions of the complex Exo system and how to optimize its effects.

Harnessing the therapeutic potential of the stem cell secretome in neonatal diseases

Preterm birth and intrapartum related complications account for a substantial amount of mortality and morbidity in the neonatal period despite significant advancements in neonatal-perinatal care. Currently, there is a noticeable lack of curative or preventative therapies available for any of the most common complications of prematurity including bronchopulmonary dysplasia, necrotizing enterocolitis, intraventricular hemorrhage, periventricular leukomalacia and retinopathy of prematurity or hypoxic-ischemic encephalopathy, the main cause of perinatal brain injury in term infants. Mesenchymal stem/stromal cell-derived therapy has been an active area of investigation for the past decade and has demonstrated encouraging results in multiple experimental models of neonatal disease. It is now widely acknowledged that mesenchymal stem/stromal cells exert their therapeutic effects via their secretome, with the principal vector identified as extracellular vesicles. This review will focus on summarizing the current literature and investigations on mesenchymal stem/stromal cell-derived extracellular vesicles as a treatment for neonatal diseases and examine the considerations to their application in the clinical setting.

Clinical and histopathological correlates of intestinal repair in preterm infants following surgical necrotizing enterocolitis

OBJECTIVE

We sought to determine the clinical and histopathological factors linked with intestinal repair and its correlation with clinical outcomes in preterm infants following surgical necrotizing enterocolitis (NEC).

METHODS

A retrospective study has compared clinical and histopathological characteristics between preterm infants with histopathological reparative changes versus non-reparative changes in resected intestinal tissue following surgical treatment of NEC. Reparative changes were defined as microscopic evidence of neovascularization, increased fibroblasts or myofibroblasts, and epithelial regeneration during histopathological examination of the most affected area of resected intestinal tissue.

RESULTS

The infants with reparative changes (53/148) had significantly lower median birth weight (725 [650-963] vs. 920 [690-1320]; p = .018), higher likelihood of patent ductus arteriosus (38/53 [71.7%] vs. 48/95 [50.5%]; p = .012), longer TPN days (99 [56-147] vs. 76.5 [39-112.5]; p = .034), higher CRP levels (7.3 [3.2-13] vs. 2.6 [1.1-7.8]; p = .011) at NEC onset, and more short bowel syndrome (27/53 [54.0%] vs. 28/95 [32.2%]; p = .012). Those with reparative changes also received more Penrose drain therapy (21/53 [39.6%] vs. 14/95 [14.7%]; p = .011) and had a longer median time to laparotomy (108 h [28-216] vs. 24 [12-96]; p = .003). Epithelial regeneration observed in 6/53 (11.3%) infants lagged fibroblast proliferation and neovascularization changes in the submucosa/muscularis intestinal layers. On a multivariable logistic regression model which included histopathological and clinical factors, inflammation with a percentage <25% area involvement, time from NEC diagnosis to surgery, and Apgar score < 6 at 5 min were independently and significantly associated with higher odds reparative changes.

CONCLUSION

In neonates with surgical NEC, the histopathological findings in the resected bowel are significantly associated with clinical characteristics, other histopathological findings, and outcomes. The presence of reparative changes consistent with healing is significantly associated with Apgar score, Penrose drain therapy, longer time from NEC diagnosis to surgery, and lower burden of inflammation in the resected bowel tissue in multivariable analyses. Routine histopathological grading of resected bowel and optimal use of Penrose drain therapy warrant further investigation in the care of neonates with surgical NEC.

Mesenchymal Stromal/Stem Cell Extracellular Vesicles and Perinatal Injury: One Formula for Many Diseases

Over the past decades, substantial advances in neonatal medical care have increased the survival of extremely premature infants. However, there continues to be significant morbidity associated with preterm birth with common complications including bronchopulmonary dysplasia (BPD), necrotizing enterocolitis (NEC), neuronal injury such as intraventricular hemorrhage (IVH) or hypoxic ischemic encephalopathy (HIE), as well as retinopathy of prematurity (ROP). Common developmental immune and inflammatory pathways underlie the pathophysiology of such complications providing the opportunity for multisystem therapeutic approaches. To date, no single therapy has proven to be effective enough to prevent or treat the sequelae of prematurity. In the past decade mesenchymal stem/stromal cell (MSC)-based therapeutic approaches have shown promising results in numerous experimental models of neonatal diseases. It is now accepted that the therapeutic potential of MSCs is comprised of their secretome, and several studies have recognized the small extracellular vesicles (sEVs) as the paracrine vector. Herein, we review the current literature on the MSC-EVs as potential therapeutic agents in neonatal diseases and comment on the progress and challenges of their translation to the clinical setting.

Advances in extracellular vesicle functionalization strategies for tissue regeneration

Extracellular vesicles (EVs) are nano-scale vesicles derived by cell secretion with unique advantages such as promoting cell proliferation, anti-inflammation, promoting blood vessels and regulating cell differentiation, which benefit their wide applications in regenerative medicine. However, the in vivo therapeutic effect of EVs still greatly restricted by several obstacles, including the off-targetability, rapid blood clearance, and undesired release. To address these issues, biomedical engineering techniques are vastly explored. This review summarizes different strategies to enhance EV functions from the perspective of drug loading, modification, and combination of biomaterials, and emphatically introduces the latest developments of functionalized EV-loaded biomaterials in different diseases, including cardio-vascular system diseases, osteochondral disorders, wound healing, nerve injuries. Challenges and future directions of EVs are also discussed.

Adenosine Alleviates Necrotizing Enterocolitis by Enhancing the Immunosuppressive Function of Myeloid-Derived Suppressor Cells in Newborns

Necrotizing enterocolitis (NEC) is a common disorder in premature infants that is characterized by hyperinflammation and severe necrosis in the intestine. The pathogenesis of NEC remains to be elucidated. In this study, we demonstrate that adenosine, a metabolite more abundant in infants than in adults, plays an important role in the prevention of NEC. Administration of adenosine or its analog, adenosine-5'-N-ethyluronamide (NECA), dramatically relieved the severity of NEC in neonatal mice. Meanwhile, adenosine treatment significantly enhanced the immunosuppressive function, antibacterial activity, and migration of myeloid-derived suppressor cells (MDSCs). However, depletion of MDSCs or inhibition of their migration using the CXCR2 inhibitor SB225002 almost completely abrogated the protective effect of adenosine on NEC. Mechanistic studies showed that MDSCs in newborns expressed abundant adenosine receptor A2B (A2BR) that elicits intracellular cAMP signaling and its downstream target NF-κB. Importantly, intestinal tissues from patients with NEC showed significantly lower infiltration of A2BR-positive MDSCs than those from healthy donors. These observations revealed that adenosine-induced MDSCs represent an essential immune axis for intestinal homeostasis in newborns.

Human breast milk-derived exosomes through inhibiting AT II cell apoptosis to prevent bronchopulmonary dysplasia in rat lung

Human breast milk (HBM) effectively prevents and cures neonatal bronchopulmonary dysplasia (BPD). Exosomes are abundant in breast milk, but the function of HBM‐derived exosomes (HBM‐Exo) in BPD is still unclear. This study was to investigate the role and mechanism of HBM‐Exo in BPD. Overall lung tissue photography and H&E staining showed that HBM‐Exo improved the lung tissue structure collapse, alveolar structure disorder, alveolar septum width, alveolar number reduction and other injuries caused by high oxygen exposure. Immunohistochemical results showed that HBM‐Exo improved the inhibition of cell proliferation and increased apoptosis caused by hyperoxia. qPCR and Western blot results also showed that HBM‐Exo improved the expression of Type II alveolar epithelium (AT II) surface marker SPC. In vivo study, CCK8 and flow cytometry showed that HBM‐Exo improved the proliferation inhibition and apoptosis of AT II cells induced by hyperoxia, qPCR and immunofluorescence also showed that HBM‐Exo improved the down‐regulation of SPC. Further RNA‐Seq results in AT II cells showed that a total of 88 genes were significantly different between the hyperoxia and HBM‐Exo with hyperoxia groups, including 24 up‐regulated genes and 64 down‐regulated genes. KEGG pathway analysis showed the enrichment of IL‐17 signalling pathway was the most significant. Further rescue experiments showed that HBM‐Exo improved AT II cell damage induced by hyperoxia through inhibiting downstream of IL‐17 signalling pathway (FADD), which may be an important mechanism of HBM‐Exo in the prevention and treatment of BPD. This study may provide new approach in the treatment of BPD.

The therapeutic effect of exosomes from mesenchymal stem cells on colorectal cancer: Toward cell-free therapy

Colorectal cancer (CRC) is known for its high mortality rate and affects more men than women. The treatment requires invasive surgical interventions, however, the progression of CRC metastasis is difficult to control in most cases. Mesenchymal stem cells (MSCs) with their outstanding characteristics have been widely used in the treatment of degenerative diseases as well as cancers. They affect the tumor microenvironment through either cell-cell interactions or communications with their secretome. While stem cells may represent a dual role in tumor proliferation and progression, exosomes have attracted much attention as a cell-free therapy in CRC treatment. Exosomes derived from native or genetically modified MSCs, as well as exosomal microRNAs (miRNAs), have been evaluated on CRC progression. Moreover, MSC-derived exosomes have been used as a carrier to deliver anticancer agents in colorectal cancer. In this review, we overview and discuss the current knowledge in both stem cell-based and cell-free exosome therapy of CRC.

Mesenchymal Stem Cell Therapy for ALI/ARDS: Therapeutic Potential and Challenges

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a serious clinical common disease, which may be caused by a variety of pathological factors and can induce a series of serious complications. There is still no specific and effective method for the treatment of ALI/ARDS. Mesenchymal stem cells (MSCs) have been one of the treatment methods for ALI, which can regulate related signal pathways such as PI3K/AKT, Wnt, and NF-κB to reduce inflammation. MSCs exist in a variety of tissues and have the ability of self-renewal and differentiation, which can be activated by specific substances or environments and home to the site of tissue damage, where they differentiate into new tissue cells and repair the damage. Both exosomes and cytokines involving the paracrine mechanism of MSCs have benefits on the treatment of ALI. Lung organoids produced by 3D culture technology can simulate the characteristics of the lung and help to research the pathophysiological process of ALI. This review summarizes the mechanisms by which MSCs treat ALI/ARDS and expects to use 3D models for future challenges in this field.

Bench to bedside - new insights into the pathogenesis of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the leading cause of death and disability from gastrointestinal disease in premature infants. Recent discoveries have shed light on a unifying theorem to explain the pathogenesis of NEC, suggesting that specific treatments might finally be forthcoming. A variety of experiments have highlighted how the interaction between bacterial signalling receptors on the premature intestine and an abnormal gut microbiota incites a pro-inflammatory response in the intestinal mucosa and its underlying endothelium that leads to NEC. Central amongst the bacterial signalling receptors implicated in NEC development is the lipopolysaccharide receptor Toll-like receptor 4 (TLR4), which is expressed at higher levels in the premature gut than in the full-term gut. The high prenatal intestinal expression of TLR4 reflects the role of TLR4 in the regulation of normal gut development, and supports additional studies indicating that NEC develops in response to signalling events that occur in utero. This Review provides new evidence explaining the pathogenesis of NEC, explores new findings indicating that NEC development has origins before birth, and discusses future questions and opportunities for discovery in this field.

Prediction of High Bell Stages of Necrotizing Enterocolitis Using a Mathematic Formula for Risk Determination

Necrotizing enterocolitis (NEC) continues to cause high morbidity and mortality. Identifying early predictors for severe NEC is essential to improve therapy and optimize timing for surgical intervention. We present a retrospective study of patients with NEC, treated between 2010 and 2020, trying to identify factors influencing the severity of NEC. Within the study period, 88 affected infants with NEC or NEC-like symptoms are analyzed. A multiple logistic regression analysis reveals the following three independent predictors for NEC in Bell stage III: red blood cell transfusion (p = 0.027 with odds ratio (OR) = 3.298), sonographic findings (p = 0.037; OR = 6.496 for patients with positive vs. patients without pathological findings) and cardiac anatomy (p = 0.015; OR = 1.922 for patients with patent ductus arteriosus (PDA) vs. patients with congenital heart disease (CHD); OR = 5.478/OR = 2.850 for patients with CHD/PDA vs. patients without cardiac disease). Results are summarized in a clinical score for daily application in clinical routine. The score is easy to apply and combines clinically established parameters, helping to determine the timing of surgical intervention.

Treatment of inflammatory bone loss in periodontitis by stem cell-derived exosomes

Periodontitis is the primary cause of tooth loss, but there is no effective treatment to repair inflammatory bone loss in periodontitis. Exosomes emerge as essential paracrine factors of mesenchymal stem cells (MSCs) that mediated tissue regeneration. Here, we investigated the potential of exosomes secreted by periodontal ligament stem cells (PDLSCs) as therapeutics for the bone defect in periodontitis. Exosomes secreted from PDLSCs derived from healthy periodontal ligaments (h-PDLSCs) and their function were evaluated on PDLSCs isolated from the inflammatory periodontal ligament of periodontitis patients (i-PDLSCs). Treatment of exosomes of h-PDLSCs led to an increase in the formation of mineralized nodules and the expressions of osteogenic genes and proteins in i-PDLSCs. Mechanistically, h-PDLSCs-exosomes suppressed the over-activation of canonical Wnt signaling to recover the osteogenic differentiation capacity of i-PDLSCs. To evaluate the therapeutic of exosomes on inflammatory bone loss, h-PDLSCs-exosomes loaded with Matrigel or β-TCP were employed to repair bone defects in rat models of periodontitis. Compared to the vehicle-treated control group, h-PDLSCs-exosomes-treated rats resulted in more bone formation in the defect of alveolar bone. In conclusion, these results demonstrated that exosomes derived from healthy PDLSCs could rescue the osteogenesis capacity of endogenous stem cells under an inflammatory environment and promote regeneration of alveolar bone. Our findings suggest that MSCs-derived exosome is an effective and practical cell-free MSC therapeutic for the treatment of periodontitis. STATEMENT OF SIGNIFICANCE: There is no effective treatment to repair inflammatory bone loss in periodontitis. As essential paracrine factors of PDLSCs, exosomes might mediate tissue regeneration during stem cell therapy. Here, we reported that exosomes secreted from healthy PDLSCs promoted the osteogenic differentiation of PDLSCs derived from periodontitis tissue. Healthy PDLSCs-exosomes treatment resulted in accelerated bone formation in the defect of alveolar bone in rat models of periodontitis. Mechanistically, h-PDLSCs-exosomes suppressed the over-activation of canonical Wnt signaling to recover the osteogenic differentiation capacity of inflammatory PDLSCs. These findings suggest that MSCs-derived exosome is an effective and practical cell-free MSC therapeutic for the treatment of periodontitis.

Necrotizing enterocolitis: Bench to bedside approaches and advancing our understanding of disease pathogenesis

Necrotizing enterocolitis (NEC) is a devastating, multifactorial disease mainly affecting the intestine of premature infants. Recent discoveries have significantly enhanced our understanding of risk factors, as well as, cellular and genetic mechanisms of this complex disease. Despite these advancements, no essential, single risk factor, nor the mechanism by which each risk factor affects NEC has been elucidated. Nonetheless, recent research indicates that maternal factors, antibiotic exposure, feeding, hypoxia, and altered gut microbiota pose a threat to the underdeveloped immunity of preterm infants. Here we review predisposing factors, status of unwarranted immune responses, and microbial pathogenesis in NEC based on currently available scientific evidence. We additionally discuss novel techniques and models used to study NEC and how this research translates from the bench to the bedside into potential treatment strategies.

Current therapy option for necrotizing enterocolitis: Practicalities and challenge

Necrotizing enterocolitis (NEC) is one of the most prevalent neonatal gastrointestinal disorders. Despite ongoing breakthroughs in its treatment and prevention, the incidence and mortality associated with NEC remain high. New therapeutic approaches, such as breast milk composition administration, stem cell therapy, immunotherapy, and fecal microbiota transplantation (FMT) have recently evolved the prevention and the treatment of NEC. This study investigated the most recent advances in NEC therapeutic approaches and discussed their applicability to bring new insight to NEC treatment.

Exosomal microRNA⁃93⁃3p secreted by bone marrow mesenchymal stem cells downregulates apoptotic peptidase activating factor 1 to promote wound healing

Wounds are soft tissue injuries, which are difficult to heal and can easily lead to other skin diseases. Bone marrow mesenchymal stem cells (BMSCs) and the secreted exosomes play a key role in skin wound healing. This study aims to clarify the effects and mechanisms of exosomes derived from BMSCs in wound healing. Exosomes were extracted from the supernatant of the BMSCs. The expression of the micro-RNA miR-93-3p was determined by qRT-PCR analysis. HaCaT cells were exposed to hydrogen peroxide (H₂O₂) to establish a skin lesion model. MTT, flow cytometry, and transwell assays were conducted to determine cellular functions. The binding relationship between miR-93-3p and apoptotic peptidase activating factor 1 (APAF1) was measured using a dual luciferase reporter gene assay. The results showed that BMSC-derived exosomes or BMSC-exos promoted proliferation and migration and suppressed apoptosis in HaCaT cells damaged by H₂O₂. However, the depletion of miR-93-3p in BMSC-exos antagonized the effects of BMSC-exos on HaCaT cells. In addition, APAF1 was identified as a target of miR-93-3p. Overexpression of APAF1 induced the dysfunction of HaCaT cells. Collectively, the results indicate that BMSC-derived exosomes promote skin wound healing via the miR-93-3p/APAF1 axis. This finding may help establish a new therapeutic strategy for skin wound healing.

An Update on the Role of Extracellular Vesicles in the Pathogenesis of Necrotizing Enterocolitis and Inflammatory Bowel Diseases

Some of the most fundamental influences of microorganisms inhabiting the human intestinal tract are exerted during infant development and impact the maturation of intestinal mucosa and gut immune system. The impact of bacteria on the host gut immune system is partially mediated via released extracellular vesicles (EVs). The heterogeneity in EV content, size, and bacterial species origin can have an impact on intestinal cells, resulting in inflammation and an immune response, or facilitate pathogen entry into the gut wall. In mammals, maintaining the integrity of the gut barrier might also be an evolutionary function of maternal milk EVs. Recently, the usage of EVs has been explored as a novel therapeutic approach in several pathological conditions, including necrotizing enterocolitis (NEC) and inflammatory bowel disease (IBD). In this review, we attempt to summarize the current knowledge of EV biology, followed by a discussion of the role that EVs play in gut maturation and the pathogenesis of NEC and IBD.

Mechanism and Potential of Extracellular Vesicles Derived From Mesenchymal Stem Cells for the Treatment of Infectious Diseases

Extracellular vesicles (EVs) are nano-sized membrane vesicles secreted by cells. EVs serve as a mediator for cell-to-cell communication by regulating the exchange of genetic materials and proteins between the donor and surrounding cells. Current studies have explored the therapeutic value of mesenchymal stem cells-derived EVs (MSC-EVs) for the treatment of infectious diseases extensively. MSC-EVs can eliminate the pathogen, regulate immunity, and repair tissue injury in contagious diseases through the secretion of antimicrobial factors, inhibiting the replication of pathogens and activating the phagocytic function of macrophages. MSC-EVs can also repair tissue damage associated with the infection by upregulating the levels of anti-inflammatory factors, downregulating the pro-inflammatory factors, and participating in the regulation of cellular biological behaviors. The purpose of this mini-review is to discuss in detail the various mechanisms of MSC-EV treatment for infectious diseases including respiratory infections, sepsis, and intestinal infections, as well as challenges for implementing MSC-EVs from bench to bedside.

Regenerative medicine for childhood gastrointestinal diseases

Several paediatric gastrointestinal diseases result in life-shortening organ failure. For many of these conditions, current therapeutic options are suboptimal and may not offer a cure. Regenerative medicine is an inter-disciplinary field involving biologists, engineers, and clinicians that aims to produce cell and tissue-based therapies to overcome organ failure. Exciting advances in stem cell biology, materials science, and bioengineering bring engineered gastrointestinal cell and tissue therapies to the verge of clinical trial. In this review, we summarise the requirements for bioengineered therapies, the possible sources of the various cellular and non-cellular components, and the progress towards clinical translation of oesophageal and intestinal tissue engineering to date.

Mesenchymal Stem Cells: Potential Therapeutic Prospect of Paracrine Pathways in Neonatal Infection

Infection is the leading cause of admission and mortality in neonatal intensive care units. Immature immune function and antibiotic resistance make the treatment more difficult. However, there is no effective prevention for it. Recently, more and more researches are focusing on stem cell therapy, especially mesenchymal stem cells (MSCs); their potential paracrine effect confer MSCs with a major advantage to treat the immune and inflammatory disorders associated with neonatal infection. In this review, we summarize the basal properties and preclinical evidence of MSCs and explore the potential mechanisms of paracrine factors of MSCs for neonatal infection.

Human breast milk-derived exosomes may help maintain intestinal epithelial barrier integrity

BACKGROUND

This study explores the functions of exosomes derived from human breast milk (HBM) in vivo and in vitro.

METHODS

HBM-derived exosomes were collected from healthy lactating mothers. In vitro analysis were divided into five groups: (1) a control with no added agents, (2) exosomes added, (3) stimulated with lipopolysaccharide (LPS), (4) pretreated with exosomes and stimulated with LPS, and (5) pretreated with exosome-free HBM and stimulated with LPS. For in vivo analysis, mouse pups were randomly assigned to four groups: (1) a control group of breastfed pups, (2) necrotizing enterocolitis-induced (NEC) pups, (3) pups pretreated with HBM-derived exosomes 6 h before being induced by NEC, and (4) pups pretreated with exosome-free HBM 6 h before NEC induction.

RESULTS

Expression of zonula occludens-1 (ZO-1), claudin-1, and occludin were decreased in groups 3 and 5. In the animal model, mice pups in group 3 showed milder intestinal tissue injury than those in group 2 or 4 and had lower levels of the proinflammatory cytokines and higher levels of epithelial tight-junction proteins than groups 2 and 4.

CONCLUSIONS

HBM-derived exosomes exert beneficial effects in preventing NEC by reducing inflammation and injury to the intestinal epithelium as well as by restoring intestinal tight-junction proteins.

IMPACT

HBM-derived exosomes can help protect the epithelial tight-junction proteins ZO-1, claudin, and occludin from inflammatory attack. This study sought (1) to analyze whether there were differences in exosome levels between the human breast milk (HBM) of mothers who had delivered preterm or at term and (2) to investigate whether these exosomes could help sustain the intestinal epithelial tight-junction proteins ZO-1, claudin-1, and occludin in the presence of NEC in vitro and in vivo.

Protective Effects of Human Milk-Derived Exosomes on Intestinal Stem Cells Damaged by Oxidative Stress

Breastfeeding has been shown to have a protective effect on the occurrence of necrotizing enterocolitis (NEC), but the mechanism remains unclear. In the context of NEC pathogenesis, many of the protective properties of exosomes on the intestinal epithelial compartment make it an ideal therapeutic target. In the present study, our hypothesis was that intestinal stem cells (ISCs) would be protected from injury by human milk-derived exosomes (HMDEs). Human breast milk was collected, and exosomes were isolated using ExoQuick reagent. Magnetic-activated cell sorting isolation of prominin-1⁺ ISCs was performed from small intestines of neonatal rat. ISCs were treated with or without H₂O₂, and HMDEs, an equal volume of HMDE-free milk, or a control solution [phosphate-buffered solution (PBS)] was added, respectively. In the absence of HMDEs, exposure of ISCs to H₂O₂ led to decreased cell viability. However, addition of HMDEs to ISCs exposed to H₂O₂ led to significantly increased ISC viability. There was a significant upregulation of mRNA expression of Axin2, c-Myc, and Cyclin D1 genes of the Wnt/β-catenin axis in ISCs treated with HMDEs (6.99 ± 2.34, 4.21 ± 1.68, 6.17 ± 2.22, respectively, P < 0.05 for all), as compared to control. In the presence of carnosic acid (a specific Wnt/β-catenin signaling inhibitor), the cell viability was significantly decreased. Thus, HMDEs protect ISCs from oxidative stress injury in vitro, which were possibly mediated via the Wnt/β-catenin signaling pathway. Our findings indicate that oral administration of HMDEs might be a promising measure in treating NEC or in preventing the development of NEC in high-risk infants when breast milk is not available.

Stem cells and exosomes: promising candidates for necrotizing enterocolitis therapy

Necrotizing enterocolitis (NEC) is a devastating disease predominately affecting neonates. Despite therapeutic advances, NEC remains the leading cause of mortality due to gastrointestinal conditions in neonates. Stem cells have been exploited in various diseases, and the application of different types of stem cells in the NEC therapy is explored in the past decade. However, stem cell transplantation possesses several deficiencies, and exosomes are considered potent alternatives. Exosomes, especially those derived from stem cells and breast milk, demonstrate beneficial effects for NEC both in vivo and in vitro and emerge as promising options for clinical practice. In this review, the function and therapeutic effects of stem cells and exosomes for NEC are investigated and summarized, which provide insights for the development and application of novel therapeutic strategies in pediatric diseases. Further elucidation of mechanisms, improvement in preparation, bioengineering, and administration, as well as rigorous clinical trials are warranted.

Extracellular Vesicles for the Treatment of Radiation Injuries

Normal tissue injury from accidental or therapeutic exposure to high-dose radiation can cause severe acute and delayed toxicities, which result in mortality and chronic morbidity. Exposure to single high-dose radiation leads to a multi-organ failure, known as acute radiation syndrome, which is caused by radiation-induced oxidative stress and DNA damage to tissue stem cells. The radiation exposure results in acute cell loss, cell cycle arrest, senescence, and early damage to bone marrow and intestine with high mortality from sepsis. There is an urgent need for developing medical countermeasures against radiation injury for normal tissue toxicity. In this review, we discuss the potential of applying secretory extracellular vesicles derived from mesenchymal stromal/stem cells, endothelial cells, and macrophages for promoting repair and regeneration of organs after radiation injury.

Extracellular vesicles isolated from milk can improve gut barrier dysfunction induced by malnutrition

Malnutrition impacts approximately 50 million children worldwide and is linked to 45% of global mortality in children below the age of five. Severe acute malnutrition (SAM) is associated with intestinal barrier breakdown and epithelial atrophy. Extracellular vesicles including exosomes (EVs; 30-150 nm) can travel to distant target cells through biofluids including milk. Since milk-derived EVs are known to induce intestinal stem cell proliferation, this study aimed to examine their potential efficacy in improving malnutrition-induced atrophy of intestinal mucosa and barrier dysfunction. Mice were fed either a control (18%) or a low protein (1%) diet for 14 days to induce malnutrition. From day 10 to 14, they received either bovine milk EVs or control gavage and were sacrificed on day 15, 4 h after a Fluorescein Isothiocyanate (FITC) dose. Tissue and blood were collected for histological and epithelial barrier function analyses. Mice fed low protein diet developed intestinal villus atrophy and barrier dysfunction. Despite continued low protein diet feeding, milk EV treatment improved intestinal permeability, intestinal architecture and cellular proliferation. Our results suggest that EVs enriched from milk should be further explored as a valuable adjuvant therapy to standard clinical management of malnourished children with high risk of morbidity and mortality.

Lactobacillus reuteri in its biofilm state promotes neurodevelopment after experimental necrotizing enterocolitis in rats

Necrotizing enterocolitis (NEC) is a devastating disease affecting premature newborns with no known cure. Up to half of survivors subsequently exhibit cognitive impairment and neurodevelopmental defects. We created a novel probiotics delivery system in which the probiotic Lactobacillus reuteri (Lr) was induced to form a biofilm [Lr (biofilm)] by incubation with dextranomer microspheres loaded with maltose (Lr-DM-maltose). We have previously demonstrated that a single dose of the probiotic Lr administered in its biofilm state significantly reduces the incidence of NEC and decreases inflammatory cytokine production in an animal model of the disease. The aim of our current study was to determine whether a single dose of the probiotic Lr administered in its biofilm state protects the brain after experimental NEC. We found that rat pups exposed to NEC reached developmental milestones significantly slower than breast fed pups, with mild improvement with Lr (biofilm) treatment. Exposure to NEC had a negative effect on cognitive behavior, which was prevented by Lr (biofilm) treatment. Lr administration also reduced anxiety-like behavior in NEC-exposed rats. The behavioral effects of NEC were associated with increased numbers of activated microglia, decreased myelin basic protein (MBP), and decreased neurotrophic gene expression, which were prevented by administration of Lr (biofilm). Our data indicate early enteral treatment with Lr in its biofilm state prevented the deleterious effects of NEC on developmental impairments.

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Early treatment with Lr in its biofilm state improves cognitive function in pups that survive experimental NEC.

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Lr in its biofilm state reduces microglia activation and MBP loss, and maintains memory and learning-related gene expression.

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Administration of Lr in its biofilm state protects the brain, as well as intestines, during experimental NEC.

Mesenchymal stem cell-derived secretomes for therapeutic potential of premature infant diseases

Preterm birth is a complex syndrome and remains a substantial public health problem globally. Its common complications include periventricular leukomalacia (PVL), bronchopulmonary dysplasia (BPD), necrotizing enterocolitis (NEC) and retinopathy of prematurity (ROP). Despite great advances in the comprehension of the pathogenesis and improvements in neonatal intensive care and associated medicine, preterm birth-related diseases remain essentially without adequate treatment and can lead to high morbidity and mortality. The therapeutic potential of mesenchymal stem/stromal cells (MSCs) appears promising as evidenced by their efficacy in preclinical models of pathologies relevant to premature infant complications. MSC-based therapeutic efficacy is closely associated with MSC secretomes and a subsequent paracrine action response to tissue injuries, which are complex and abundant in response to the local microenvironment. In the current review, we summarize the paracrine mechanisms of MSC secretomes underlying diverse preterm birth-related diseases, including PVL, BPD, NEC and ROP, are summarized, and focus is placed on MSC-conditioned media (CM) and MSC-derived extracellular vesicles (EVs) as key mediators of modulatory action, thereby providing new insights for future therapies in newborn medicine.

Administration of extracellular vesicles derived from human amniotic fluid stem cells: a new treatment for necrotizing enterocolitis

PURPOSE

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal disease. Amniotic fluid stem cells (AFSC) improve NEC injury but human translation remains difficult. We aimed to evaluate the use of extracellular vesicles (EV) derived from human AFSC.

METHODS

Human AFSC (hAFSC) were cultured according to the protocol (Celprogen Inc., California, U.S.A.). Conditioned medium was obtained, ultra-centrifuged, and EV were suspended in phosphate-buffered saline (PBS). C57BL/6 pups were grouped into: (1) breast-fed (Control, n = 11); (2) NEC + placebo (NEC + PBS; n = 10); and (3) NEC + treatment (NEC + EV; n = 11). NEC was induced post-natal days P5-9 by (A) gavage feeding hyperosmolar formula; (B) hypoxia for 10 min; and (C) lipopolysaccharide. Intra-peritoneal injections of PBS or hAFSC-EV were given on P6-7. All animals were sacrificed on P9 and terminal ileum harvested.

RESULTS

hAFSC-EV administration reduced intestinal injury (p = 0.0048), NEC incidence (score ≥ 2), and intestinal inflammation (IL-6 p < 0.0001; TNF-α p < 0.0001). Intestinal stem cell expression (Lgr5 +) and cellular proliferation (Ki67) were enhanced above control levels following hAFSC-EV administration (Lgr5 p = 0.0003; Ki67 p < 0.0001).

CONCLUSION

hAFSC-EV administration reduced intestinal NEC injury and inflammation while increasing stem cell expression and cellular proliferation. hAFSC-EV administration may induce similar beneficial effects to exogenous stem cells.

TFF3 mediates the NF-κB/COX2 pathway to regulate PMN-MDSCs activation and protect against necrotizing enterocolitis

Intestinal trefoil factor 3 (TFF3) plays an important role in repairing the intestinal mucosa. However, the detailed mechanism regarding immune regulation by TFF3 is not well defined. Here, we reported that treatment of mouse BM cells and human peripheral blood mononuclear cells from healthy volunteers with TFF3 activated polymorphnuclear myeloid-derived suppressor cells (PMN-MDSCs) in vitro. We also found that prostaglandin E2 is a major TFF3-mediated MDSC target, and that NF-κB/COX2 signaling was involved in this process. Moreover, TFF3 treatment or transfer of TFF3-derived PMN-MDSCs (TFF3-MDSCs) to experimental necrotizing enterocolitis (NEC) mice caused PMN-MDSC accumulation in the lamina propria (LP), which was associated with decreased intestinal inflammation, permeability, bacterial loading, and prolonged survival. Interestingly, no NEC severity remission was observed in Rag1 KO mice that were given TFF3-MDSCs, but coinjection with CD4⁺ T cells significantly relieved NEC inflammation. Overall, TFF3 mediates the NF-κB/COX2 pathway to regulate PMN-MDSC activation and attenuates NEC in a T-cell-dependent manner, which suggests a novel mechanism in preventing NEC occurrence.

Intestinal Stem Cell Development in the Neonatal Gut: Pathways Regulating Development and Relevance to Necrotizing Enterocolitis

The intestine is extremely dynamic and the epithelial cells that line the intestine get replaced every 3–5 days by highly proliferative intestinal stem cells (ISCs). The instructions for ISCs to self-renew or to differentiate come as cues from their surrounding microenvironment or their niche. A small number of evolutionarily conserved signaling pathways act as a critical regulator of the stem cells in the adult intestine, and these pathways are well characterized. However, the mechanisms, nutritional, and environmental signals that help establish the stem cell niche in the neonatal intestine are less studied. Deciphering the key signaling pathways that regulate the development and maintenance of the stem cells is particularly important to understanding how the intestine regenerates from necrotizing enterocolitis, a devastating disease in newborn infants characterized by inflammation, tissues necrosis, and stem cell injury. In this review, we piece together current knowledge on morphogenetic and immune pathways that regulate intestinal stem cell in neonates and highlight how the cross talk among these pathways affect tissue regeneration. We further discuss how these key pathways are perturbed in NEC and review the scientific knowledge relating to options for stem cell therapy in NEC gleaned from pre-clinical experimental models of NEC.

Delivery Efficacy Differences of Intravenous and Intraperitoneal Injection of Exosomes: Perspectives from Tracking Dye Labeled and MiRNA Encapsulated Exosomes

BACKGROUND

Exosomes are cell-derived nanovesicles that play vital roles in intercellular communication. Recently, exosomes are recognized as promising drug delivery vehicles. Up till now, how the in vivo distribution of exosomes is affected by different administration routes has not been fully understood.

METHODS

In the present study, in vivo distribution of exosomes following intravenous and intraperitoneal injection approaches was systemically analyzed by tracking the fluorescence-labeled exosomes and qPCR analysis of C. elegans specific miRNA abundance delivered by exosomes in different organs.

RESULTS

The results showed that exosomes administered through tail vein were mostly taken up by the liver, spleen and lungs while exosomes injected intraperitoneally were more dispersedly distributed. Besides the liver, spleen, and lungs, intraperitoneal injection effectively delivered exosomes into the visceral adipose tissue, making it a promising strategy for obesity therapy. Moreover, the results from fluorescence tracking and qPCR were slightly different, which could be explained by systemic errors.

CONCLUSION

Together, our study reveals that different administration routes cause a significant differential in vivo distribution of exosomes, suggesting that optimization of the delivery route is prerequisite to obtain rational delivery efficiency in detailed organs.

Mesenchymal Stem Cell-Derived Exosomes: Biological Function and Their Therapeutic Potential in Radiation Damage

Radiation-induced damage is a common occurrence in cancer patients who undergo radiotherapy. In this setting, radiation-induced damage can be refractory because the regeneration responses of injured tissues or organs are not well stimulated. Mesenchymal stem cells have become ideal candidates for managing radiation-induced damage. Moreover, accumulating evidence suggests that exosomes derived from mesenchymal stem cells have a similar effect on repairing tissue damage mainly because these exosomes carry various bioactive substances, such as miRNAs, proteins and lipids, which can affect immunomodulation, angiogenesis, and cell survival and proliferation. Although the mechanisms by which mesenchymal stem cell-derived exosomes repair radiation damage have not been fully elucidated, we intend to translate their biological features into a radiation damage model and aim to provide new insight into the management of radiation damage.

Stem Cells as Therapy for Necrotizing Enterocolitis: A Systematic Review and Meta-Analysis of Preclinical Studies

Background: Necrotizing enterocolitis (NEC) is the most common life-threatening gastrointestinal condition among very and extremely preterm infants. Stem cell therapy has shown some promising protective effects in animal models of intestinal injury, including NEC, but no systematic review has yet evaluated the preclinical evidence of stem cell therapy for NEC prevention or treatment. Methods: PubMed and EMBASE databases were searched for studies using an animal model of NEC with stem cells or their products. The SYRCLE tool was used for the assessment of risk of bias. A random-effects model was used to pool odds ratios (ORs) and 95% confidence interval (CI). Results: We screened 953 studies, of which nine (eight rat and one mouse models) met the inclusion criteria. All animal models induced NEC by a combination of hypothermia, hypoxia, and formula feeding. Risk of bias was evaluated as unclear on most items for all studies included. Meta-analysis found that both mesenchymal and neural stem cells and stem cell-derived exosomes reduced the incidence of all NEC (OR 0.22, 95% CI 0.16-0.32, k = 16), grade 2 NEC (OR 0.41, 95% CI 0.24-0.70, k = 16), and grade 3-4 NEC (OR 0.28, 95% CI 0.19-0.42, k = 16). k represents the number of independent effect sizes included in each meta-analysis. The effect of the exosomes was similar to that of the stem cells. Stem cells and exosomes also improved 4-day survival (OR 2.89 95% CI 2.07-4.04, k = 9) and 7-day survival (OR 3.96 95% CI 2.39-6.55, k = 5) after experimental NEC. Meta-analysis also found that stem cells reduced other indicators of intestinal injury. Conclusion: The data from this meta-analysis suggest that both stem cells and stem cell-derived exosomes prevented NEC in rodent experimental models. However, unclear risk of bias and incomplete reporting underline that poor reporting standards are common and hamper the reliable interpretation of preclinical evidence for stem cell therapy for NEC.

Ginsenoside RG1 enhances the paracrine effects of bone marrow-derived mesenchymal stem cells on radiation induced intestinal injury

Content and aims: Ginsenoside RG1 (RG1) is thought to enhance proliferation and differentiation of stem cell, however, its role on paracrine efficacy of stem cell remains unclear. Here we examined if and how RG1 enhances the paracrine effects of bone marrow-derived mesenchymal stem cells (BM-MSCs) on radiation induced intestinal injury (RIII).

METHOD

Irradiated rats randomly received intraperitoneal injection of conditioned medium (CM) derived from non-activated BM-MSCs (MSC-CM) or BM-MSCs pre-activated by RG-1 (RG1-MSC-CM). Intestinal samples were collected, followed by the evaluation of histological and functional change, apoptosis, proliferation, inflammation, angiogenesis and stem cell regeneration. The effects of heme oxygenase-1 (HO-1) were investigated using HO-1 inhibitor or siRNA.

RESULT

RG1 enhanced the paracrine efficacy of BM-MSCs partially through upregulation of HO-1. RG1-MSC-CM rather than MSC-CM significantly improved the survival and intestinal damage of irradiated rats via improvement of intestinal proliferation/apoptosis, inflammation, angiogenesis and stem cell regeneration in a HO-1 dependent mechanism. The mechanism for the superior paracrine efficacy of RG1-MSC-CM is related to a higher release of two pivotal cytokines VEGF and IL-6.

CONCLUSION

Our study revealed that RG1 enhances paracrine effects of BM-MSCs on RIII, providing a novel method for maximizing the paracrine potential of MSCs.