The impact of aging on intestinal mucosal immune function and clinical applications

Sensor-integrated gut-on-a-chip for monitoring senescence-mediated changes in the intestinal barrier

The incidence of inflammatory bowel disease among the elderly has significantly risen in recent years, posing a growing socioeconomic burden to aging societies. Moreover, non-gastrointestinal diseases, also prevalent in this demographic, have been linked to intestinal barrier dysfunction, thus highlighting the importance of investigating aged-mediated changes within the human gut. While gastrointestinal pathology often involves an impaired gut barrier, the impact of aging on the human gastrointestinal barrier function remains unclear. To explore the effect of senescence, a key hallmark of aging, on gut barrier integrity, we established and evaluated an in vitro gut-on-a-chip model tailored to investigate barrier changes by the integration of an impedance sensor. Here, a microfluidic gut-on-a-chip system containing integrated membrane-based electrode microarrays is used to non-invasively monitor epithelial barrier formation and senescence-mediated changes in barrier integrity upon treating Caco-2 cells with 0.8 μg mL-1 doxorubicin (DXR), a chemotherapeutic which induces cell cycle arrest. Results of our microfluidic human gut model reveal a DXR-mediated increase in impedance and cell hypertrophy as well as overexpression of p21, and CCL2, indicative of a senescent phenotype. Combined with the integrated electrodes, monitoring ∼57% of the cultivation area in situ and non-invasively, the developed chip-based senescent-gut model is ideally suited to study age-related malfunctions in barrier integrity.

Achieving healthy aging through gut microbiota-directed dietary intervention: Focusing on microbial biomarkers and host mechanisms

BACKGROUND

Population aging has become a primary global public health issue, and the prevention of age-associated diseases and prolonging healthy life expectancies are of particular importance. Gut microbiota has emerged as a novel target in various host physiological disorders including aging. Comprehensive understanding on changes of gut microbiota during aging, in particular gut microbiota characteristics of centenarians, can provide us possibility to achieving healthy aging or intervene pathological aging through gut microbiota-directed strategies.

AIM OF REVIEW

This review aims to summarize the characteristics of the gut microbiota associated with aging, explore potential biomarkers of aging and address microbiota-associated mechanisms of host aging focusing on intestinal barrier and immune status. By summarizing the existing effective dietary strategies in aging interventions, the probability of developing a diet targeting the gut microbiota in future is provided.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review is focused on three key notions: Firstly, gut microbiota has become a new target for regulating health status and lifespan, and its changes are closely related to age. Thus, we summarized aging-associated gut microbiota features at the levels of key genus/species and important metabolites through comparing the microbiota differences among centenarians, elderly people and younger people. Secondly, exploring microbiota biomarkers related to aging and discussing future possibility using dietary regime/components targeted to aging-related microbiota biomarkers promote human healthy lifespan. Thirdly, dietary intervention can effectively improve the imbalance of gut microbiota related to aging, such as probiotics, prebiotics, and postbiotics, but their effects vary among.

Lifelong partners: Gut microbiota-immune cell interactions from infancy to old age

Our immune system and gut microbiota are intricately coupled from birth, both going through maturation during early life and senescence during aging almost in a synchronized fashion. The symbiotic relationship between the human host and microbiota is critically dependent on a healthy immune system to keep our microbiota in check, while the microbiota provides essential functions to promote the development and fitness of our immune system. The partnership between our immune system and microbiota is particularly important during early life, when microbial ligands and metabolites shape the development of the immune cells and immune tolerance; during aging, having sufficient beneficial gut bacteria is critical for the maintenance of intact mucosal barriers, immune metabolic fitness, and strong immunity against pathogens. The immune system during childhood is programmed, with the support of the microbiota, to develop robust immune tolerance, and limit autoimmunity and metabolic dysregulation, which are prevalent during aging. This review comprehensively explores the mechanistic underpinnings of gut microbiota-immune cell interactions during infancy and old age, with the goal to gain a better understanding of potential strategies to leverage the gut microbiota to combat age-related immune decline.

Effects of Intestinal M Cells on Intestinal Barrier and Neuropathological Properties in an AD Mouse Model

Intestinal microfold cells (M cells) play a critical role in the immune response of the intestinal mucosa by actively taking up antigens, facilitating antigen presentation to immune cells, and promoting the production of secretory immunoglobulin A by B cells. Despite their known important functions in the gut, the effect of M cells on the central nervous system remains unclear. We investigated the expression of M cell-related factor genes and protein levels in Peyer's patches (PPs) of 3-month-old and 9-month-old APP/PS1 mice, as well as the expression of intestinal barrier proteins in the ileum and colon of these mice. Furthermore, we employed intestinal M cell conditional ablation mice (i.e., RankΔIEC mice) to assess the influence of M cells on the intestinal barrier and Alzheimer's disease (AD)-like behavioral and pathological features. Our findings revealed that compared to wild-type mice, APP/PS1 mice showed altered M cell-related genes and disrupted intestinal barriers. In addition, there is a significant decrease in glycoprotein 2 (GP2) mRNA levels in the PPs of 3-month-old APP/PS1 mice, with the relative expression of GP2 mRNA tending to zero. Parameters related to the intestinal barrier (IgA, MUC2, Claudin-5, ZO-1) were significantly downregulated in both 3-month-old and 9-month-old APP/PS1 mice compared to wild-type controls, and the differences were more pronounced in the 9-month-old mice. Moreover, M cell ablation in APP/PS1 mice (i.e., APP/PS1ΔMC mice) resulted in more severe intestinal barrier destruction. Notably, we observed through water maze experiments that APP/PS1ΔMC mice at 6 months of age exhibited significantly poorer spatial learning memory compared to APP/PS1 mice. And the neuropathological alterations were also observed in APP/PS1ΔMC mice at 6 months of age that when intestinal M cells are damaged in APP/PS1 mice, brain microglia are activated, Tau phosphorylation is exacerbated, and the number of neurons is reduced. Our results suggest for the first time that the absence of intestinal M cells might further aggravate intestinal leakage, lead to neuropathological damage, and subsequently cause the impairment of learning memory ability in AD mice. Our research highlights the impact of intestinal M cells on the intestinal barrier and AD neuropathogenesis in AD mouse model.

Immunosenescence in digestive system cancers: Mechanisms, research advances, and therapeutic strategies

Increasing lifespans and external environmental factors have contributed to the increase of age-related diseases, particularly cancer. A decrease in immune surveillance and clearance of cancer cells is the result of immunosenescence, which involves the remodeling of immune organs, the changes and functional decline of immune cell subsets, in association with systemic low-grade chronic inflammation. Stem cells aging in bone marrow and thymic involution are the most important causes of immunosenescence. Senescent cancer cells promote the differentiation, recruitment, and functional upregulation of immune-suppressive cell subsets e.g. regulatory T cells (Tregs), myeloid-derived suppressor cell (MDSC), tumor-associated macrophages (TAMS) through senescence-associated secretory phenotype (SASP) further exacerbating the immunosuppressive microenvironment. For digestive system cancers, age-related damage to the intestinal mucosal barrier, the aging of gut-associated lymphoid tissue (GALT), exposure to xenobiotic stimuli throughout life, and dysbiosis make the local immune microenvironment more vulnerable. This article systematically reviews the research progress of immunosenescence and immune microenvironment in digestive system cancers, as well as the exploration of related therapy strategies, hoping to point out new directions for research in the digestive system cancers.

Faecal intestinal permeability and intestinal inflammatory markers in older adults with age-related disorders: A systematic review and meta-analysis

This systematic review and meta-analysis appraised previous findings to uncover potential faecal intestinal permeability and intestinal inflammatory markers in older adults. A comprehensive literature search led to the identification of ten eligible studies with findings of potential faecal intestinal permeability (zonulin and alpha-1-antitrypsin) and intestinal inflammatory markers [calprotectin, lactoferrin and neutrophil gelatinase-associated lipocalin (NGAL)]. Most of the cases (n > 2) [Parkinson's disease (PD) and Alzheimer's disease (AD)] exhibited higher faecal alpha-1-antitrypsin, zonulin and calprotectin levels. The present meta-analysis confirmed significantly higher faecal alpha-1-antitrypsin in older persons with PD compared to non-PD [MD = 22.92 mg/dL; 95 % CI = 14.02-31.81, p < 0.00001; I2 = 0 % (p = 0.73)]. There was, however, no significant difference in faecal zonulin between PD and non-PD individuals [MD = 26.88 ng/mL; 95 % CI = -29.26-83.01, p = 0.35; I2 = 94 % (p < 0.0001)]. Meanwhile, faecal calprotectin was higher in older adults with GI symptoms, multiple system atrophy (MSA) or PD than the healthy controls [MD = 9.51 μg/g; 95 % CI = 0.07-18.95, p = 0.05; I2 = 84 % (p < 0.00001)]. Altogether, faecal calprotectin appears to be a potential intestinal inflammatory marker whereas previous findings on faecal alpha-1-antitrypsin as an intestinal permeability marker remain limited and require further validation.

Gut aging: A wane from the normal to repercussion and gerotherapeutic strategies

Globally, age-related diseases represent a significant public health concern among the elderly population. In aging, healthy organs and tissues undergo structural and functional changes that put the aged adults at risk of diseases. Some of the age-related diseases include cancer, atherosclerosis, brain disorders, muscle atrophy (sarcopenia), gastrointestinal (GIT) disorders, etc. In organs, a decline in stem cell function is the starting point of many conditions and is extremely important in GIT disorder development. Many studies have established that aging affects stem cells and their surrounding supportive niche components. Although there is a significant advancement in treating intestinal aging, the rising elderly population coupled with a higher occurrence of chronic gut ailments necessitates more effective therapeutic approaches to preserve gut health. Notable therapeutic strategies such as Western medicine, traditional Chinese medicine, and other health-promotion interventions have been reported in several studies to hold promise in mitigating age-related gut disorders. This review highlights findings across various facets of gut aging with a focus on aging-associated changes of intestinal stem cells and their niche components, thus a deviation from the normal to repercussion, as well as essential therapeutic strategies to mitigate intestinal aging.

The Combination of Host-Associated Bacillus megaterium R32 and Stachyose Promotes the Intestinal Health of Turbot (Scophthalmus maximus. L)

An 8-week feeding trial was conducted to investigate the effects of host-associated Bacillus megaterium R32 and stachyose on the intestinal mucosal defense system of turbot (Scophthalmus maximus. L). Three isonitrogenous and isolipidic diets were formulated: control diet (C), control diet with 1.0 × 108 CFU/g B. megaterium R32 (RC), and 1.0 × 108 CFU/g B. megaterium R32 + 1.5% stachyose (RS) supplementation separately. The results showed that diets RS and RC significantly inhibited the expression of cell development and apoptosis-related genes (β-catenin, CyclinD1, BAX, Bid); diets RS and RC significantly increased the expression of intestinal tight junction protein claudin-4, while RS group significantly decreased the expression of myosin light chain kinase; diets RS and RC significantly decreased the expression of proinflammatory factors (IL-13, IL-15, IFN- γ), diet RS also significantly decreased the expression of TNF-α and AP-1, and increased the expression of TGF-β. 16s rRNA gene sequencing results showed that diets RS and RC significantly decreased the abundance of conditional pathogenic bacteria (Corynebacterium, Desulfovibrio, Escherichia-Shigella). Among them, the abundance of Bacillus in the RS group was the highest. It is concluded that the combination of stachyose and B. megaterium R32 had a more positive effect on intestinal cell development and barrier function and strengthened the intestinal mucosal defense system of turbot.

Umbilical cord mesenchymal stem cells in ulcerative colitis treatment: efficacy and possible mechanisms

BACKGROUND

Mesenchymal stem cells (MSCs) possess powerful immunomodulatory ability. This study aimed to assess the efficacy and safety of human umbilical cord-derived mesenchymal stem cells (UMSCs) in patients with ulcerative colitis (UC) and to explore the potential mechanisms.

METHODS

This prospective, self-controlled clinical study was conducted at Henan Provincial People's Hospital. Patients with moderate-to-severe active UC, unresponsive to traditional drugs were continuously enrolled from September 2018 to March 2023. UMSCs were administered intravenously monthly for two months at a cell dosage of 1 × 106 per kg. The primary outcome was a clinical response at 2 months. The levels of cytokines and progerin in the plasma of the patients were analyzed using enzyme-linked immunosorbent assay kits, and longitudinal data was analyzed using generalized estimation equation.

RESULTS

Forty-one patients were enrolled and received UMSC therapy. At 2 months, 73.2% (30/41) of patients achieved a clinical response, and 41.5% (17/41) achieved a clinical remission. At 6 months, 2 patients were lost to follow-up; the corresponding figures were 70.0% (25/41) and 34.2% (14/41), respectively. After UMSC therapy, the Mayo score, Mayo endoscopy score, mean and maximum values of Ulcerative Colitis Endoscopic Index of Severity and Nancy index were significantly reduced compared with baseline values. Additionally, the levels of progerin and inflammatory markers, such as interleukin (IL)-1β, IL-6, IL-8, IL-12, and IL-17 A decreased, while hemoglobin, albumin, and IL-10/IL-17 A ratio increased, particularly in the response group. Multiple stepwise logistic regression analysis showed age was an independent risk factor affecting efficacy (odds ratio, 0.875 (95% confidence interval (0.787, 0.972)); the area under the receiver operating characteristic curve for age was 0.79. No serious adverse events were observed during or after UMSC therapy.

CONCLUSION

UMSCs are safe and effective for patients with UC, with age being an independent risk factor affecting efficacy. Mechanistically, UMSC treatment may ameliorate cell senescence and suppress the secretion of pro-inflammatory cytokines.

TRIAL REGISTRATION

The study was retrospectively registered at www.chictr.org.cn/ (ChiCTR1900026035) on September 18, 2019.

Detection and consistency of mucosal fluid T lymphocyte phenotypes and their relationship with blood, age and gender

Innate and adaptive immune responses at mucosal surfaces play a role in protection against most infectious diseases. However, the relative importance either of mucosal versus systemic, or of cellular versus humoral immunity in protection against such infections remains unclear. We aimed to determine the relative percentages and reproducibility of detection of five major T lymphocyte phenotypes in stimulated whole mouth fluid (SWMF); to compare matched mucosal and blood phenotypes; to evaluate the consistency of phenotypes in SWMF over time; and to determine any associations with age or gender. Peripheral blood and SWMF samples were collected from 194 participants and sequential concomitant samples were collected from 27 of those and from 12 subjects living with HIV. CD3, CD4, CD8, Th1 and Th2 T lymphocyte phenotypes were determined by FACS. All the five T lymphocyte phenotypes were detected consistently by FACS in PBMC and SWMF with experimental replicates (N = 10; PBMC CV: 3-30%; SWMF CV: 12-36%). In longitudinal samples detection rates were reproducible in both fluids but variations were higher in SWMF (CV: 23-79.6%) than PBMC (CV: 9.7-75%). Statistically significant correlations of the percentages of all the T lymphocyte phenotypes except CD8 was seen between the two fluids. In PBMCs a negative correlation with age was found with CD3, CD4 and CD8 phenotypes, whilst a positive correlation was found in both SWMF and PBMC with the Th2 phenotype. CD3, CD4 and CD8 phenotypes in SWMF and PBMCs from an HIV-positive cohort were not significantly correlated in contrast with the HIV-negative controls. Our study provides a robust FACS protocol for the detection of the five major T lymphocyte phenotypes in SWMF which should prove useful for research with other mucosal fluids.

Unravelling the Oral-Gut Axis: Interconnection Between Periodontitis and Inflammatory Bowel Disease, Current Challenges, and Future Perspective

As the opposite ends of the orodigestive tract, the oral cavity and the intestine share anatomical, microbial, and immunological ties that have bidirectional health implications. A growing body of evidence suggests an interconnection between oral pathologies and inflammatory bowel disease [IBD], implying a shift from the traditional concept of independent diseases to a complex, reciprocal cycle. This review outlines the evidence supporting an 'oral-gut' axis, marked by a higher prevalence of periodontitis and other oral conditions in IBD patients and vice versa. We present an in-depth examination of the interconnection between oral pathologies and IBD, highlighting the shared microbiological and immunological pathways, and proposing a 'multi-hit' hypothesis in the pathogenesis of periodontitis-mediated intestinal inflammation. Furthermore, the review underscores the critical need for a collaborative approach between dentists and gastroenterologists to provide holistic oral-systemic healthcare.

Inflammaging: The Next Challenge-Exploring the Role of Gut Microbiota, Environmental Factors, and Sex Differences

The term 'inflammaging' has been coined to describe the chronic state of inflammation derived from ongoing cycles of tissue damage and the subsequent immune responses. This inflammatory status contributes to the decline of organs and physiological functions, accelerates the aging process, and increases the risk of age-related illnesses and death. During aging, the gut microbiota (GM) undergoes significant changes, including a decreased diversity of species, a decline in beneficial bacteria, and a rise in proinflammatory ones, resulting in persistent low-grade inflammation. Moreover, environmental factors, such as diet and medications, contribute to age-related changes in GM and immune function, preventing or promoting inflammaging. This narrative review aims to clarify the underlying mechanisms of inflammaging and to specifically investigate the influence of GM and several environmental factors on these mechanisms, while also exploring potential differences related to sex. Moreover, lifestyle and pharmacological interventions will be suggested to promote healthy aging.

Changes in M6A methylation: A key factor in the vicious cycle of flora -gut aging

The aging process significantly impacts the gastrointestinal tract and various bodily systems, exacerbating age-related diseases. Research suggests a correlation between an imbalance in intestinal flora and gut aging, yet the precise mechanism remains incompletely elucidated. Epigenetic modifications, particularly m6A methylation, play a pivotal role in driving aging and are closely associated with gut aging. Maintaining a healthy balance of intestinal microbes is contingent upon m6A methylation, which is believed to be crucial in the vicious cycle of gut aging and intestinal flora. This article highlights the importance of m6A methylation in the nexus between gut aging and flora. It proposes the potential for targeted m6A methylation to break the vicious cycle of gut aging and flora imbalance, offering novel perspectives on attenuating or reversing gut aging.

COVID-19: Post infection implications in different age groups, mechanism, diagnosis, effective prevention, treatment, and recommendations

SARS-CoV-2 is a highly contagious pathogen that predominantly caused the COVID-19 pandemic. The persistent effects of COVID-19 are defined as an inflammatory or host response to the virus that begins four weeks after initial infection and persists for an undetermined length of time. Chronic effects are more harmful than acute ones thus, this review explored the long-term effects of the virus on various human organs, including the pulmonary, cardiovascular, and neurological, reproductive, gastrointestinal, musculoskeletal, endocrine, and lymphoid systems and found that SARS-CoV-2 adversely affects these organs of older adults. Regarding diagnosis, the RT-PCR is a gold standard method of diagnosing COVID-19; however, it requires specialized equipment and personnel for performing assays and a long time for results production. Therefore, to overcome these limitations, artificial intelligence employed in imaging and microfluidics technologies is the most promising in diagnosing COVID-19. Pharmacological and non-pharmacological strategies are the most effective treatment for reducing the persistent impacts of COVID-19 by providing immunity to post-COVID-19 patients by reducing cytokine release syndrome, improving the T cell response, and increasing the circulation of activated natural killer and CD8 T cells in blood and tissues, which ultimately reduces fever, nausea, fatigue, and muscle weakness and pain. Vaccines such as inactivated viral, live attenuated viral, protein subunit, viral vectored, mRNA, DNA, or nanoparticle vaccines significantly reduce the adverse long-term virus effects in post-COVID-19 patients; however, no vaccine was reported to provide lifetime protection against COVID-19; consequently, protective measures such as physical separation, mask use, and hand cleansing are promising strategies. This review provides a comprehensive knowledge of the persistent effects of COVID-19 on people of varying ages, as well as diagnosis, treatment, vaccination, and future preventative measures against the spread of SARS-CoV-2.

Prediction of the risk of severe small bowel obstruction and effects of Houpu Paiqi mixture in patients undergoing surgery for small bowel obstruction

AIM

Small bowel obstruction is a common condition that requires emergency surgery. Slow recovery of bowel function after surgery or the occurrence of one or more complications can exacerbate the disease and result in severe small bowel obstruction (SSBO), significantly impacting recovery. It is characterized by a failure to regain enteral nutrition promptly, requiring long-term intensive care. Therefore, it is necessary to identify factors that predict SSBO, to allow early intervention for patients likely to develop this condition.

METHODS

Of the 260 patients who underwent emergency or elective surgery for small bowel obstruction between January 2018 and December 2022, 45 developed SSBO. The least absolute shrinkage and selection operator regression model was applied to optimize factor selection and multivariable logistic regression analysis was used to construct a predictive model. The performance and clinical utility of the nomogram were determined and internal validation was conducted. In addition, the effects of the Houpu Paiqi mixture on postoperative recovery were analyzed by comparing the clinical data of 28 patients who were treated with the mixture and 61patients who did not receive it.

RESULTS

The predictors included in the prediction nomogram were age, peritonitis, intestinal resection and anastomosis, complications, operation time, Acute Physiology and Chronic Health Evaluation II score, white blood cell count, and procalcitonin level. The model had an area under the receiver operating characteristic curve of 0.948 (95% confidence interval: 0.814-0.956). Decision curve analysis demonstrated that the SSBO risk nomogram had a good net clinical benefit. In addition, treatment with the Houpu Paiqi mixture reduced postoperative exhaust time, postoperative defecation time, time to first postoperative liquid feed, and length of stay in hospital.

CONCLUSIONS

We developed a nomogram that can assist clinicians in identifying patients at greater risk of SSBO, which may aid in early diagnosis and intervention. Additionally, we found that the Houpu Paiqi mixture promoted postoperative recovery.

Unraveling the Link between Periodontitis and Inflammatory Bowel Disease: Challenges and Outlook

Periodontitis and Inflammatory Bowel Disease (IBD) are chronic inflammatory conditions, characterized by microbial dysbiosis and hyper-immunoinflammatory responses. Growing evidence suggest an interconnection between periodontitis and IBD, implying a shift from the traditional concept of independent diseases to a complex, reciprocal cycle. This review outlines the evidence supporting an "Oral-Gut" axis, marked by a higher prevalence of periodontitis in IBD patients and vice versa. The specific mechanisms linking periodontitis and IBD remain to be fully elucidated, but emerging evidence points to the ectopic colonization of the gut by oral bacteria, which promote intestinal inflammation by activating host immune responses. This review presents an in-depth examination of the interconnection between periodontitis and IBD, highlighting the shared microbiological and immunological pathways, and proposing a "multi-hit" hypothesis in the pathogenesis of periodontitis-mediated intestinal inflammation. Furthermore, the review underscores the critical need for a collaborative approach between dentists and gastroenterologists to provide holistic oral-systemic healthcare.

The antioxidant effects of hedysarum polybotrys polysaccharide in extending lifespan and ameliorating aging-related diseases in Drosophila melanogaster

Hedysarum polybotrys polysaccharide (HPS) is one of the main active ingredients of Hedysarum with many health-beneficial properties, including antioxidant property, immunomodulatory, anti-inflammatory, and anti-tumor. However, the effect of HPS on anti-aging is still unclear. This study was to explore the protective function of HPS on aging and age-related diseases using Drosophila melanogaster. The results demonstrated that HPS supplementation promoted hatchability and prolonged lifespan by enhancing the antioxidative capacity. Administraction of HPS ameliorated age-related symptoms such as imbalanced intestinal homeostasis, sleep disturbances, and beta-amyloid (Aβ) induced Alzheimer's disease (AD) in flies, but did not modulate neurobehavioral deficits in the AD model of tauopathy and the Parkinson's disease (PD) model of Pink1 mutation. Overall, this study reveals that HPS has strong potential in the prevention of aging and age-related diseases, and provided a new candidate for the development of anti-aging drugs.