Inteins are unique protein insertion sequences capable of self-excision, enabling the covalent ligation of flanking extein peptides via amide bond formation. This process proceeds spontaneously without requiring external enzymes, cofactors, or chemical reagents, granting inteins exceptional biocompatibility and traceless performance in protein engineering applications. Split inteins represent a specialized and versatile subclass whose splicing domains are encoded by two separate gene fragments rather than a single continuous open reading frame. These fragments, known as the N-terminal (IntN) and C-terminal (IntC) split inteins, associate through non-covalent interactions including hydrophobic forces, hydrogen bonds, and van der Waals forces to assemble into an active three-dimensional structure, which then drives efficient extein ligation and enables protein trans-splicing. Protein trans-splicing mediated by split inteins has become a cornerstone for traceless protein ligation owing to its high specificity and irreversibility, fundamentally reshaping strategies for protein modification, assembly, and functional regulation. Compared with traditional chemical ligation methods, split intein systems require no complex chemical derivatization of peptide fragments and can operate efficiently at micromolar concentrations under physiological conditions, thus avoiding structural and functional damage caused by organic reagents. In contrast to enzymatic ligation tools such as sortase, split inteins eliminate the need for additional enzymes or cofactors, simplifying reaction systems, reducing costs, and minimizing non-specific side products. These distinctive advantages render split inteins highly promising for applications in chemical biology, synthetic biology, and biopharmaceutical development. In recent years, deepened mechanistic understanding has established structure-guided rational design as the primary approach to overcoming key limitations of split inteins, including intrinsic aggregation propensity, strict extein sequence dependence, and limited splicing efficiency. Bioinformatic tools have been used to identify aggregation-prone regions in the IntN fragment, and site-directed mutagenesis of hydrophobic residues, relocation of split sites, or removal of misfolding-prone sequences has substantially reduced in vitro aggregation and improved soluble expression and assembly activity. Rational engineering of catalytic residues and adjacent flexible loops has relaxed strict amino acid preferences at extein junctions, enhancing sequence tolerance and reducing the risk of functional impairment in target proteins. Consensus design based on multiple sequence alignments has yielded ultra-fast splicing variants such as Cfa DnaE and Cat-TerL, which exhibit significantly accelerated kinetics and improved tolerance to denaturing conditions. Meanwhile, advances in structural biology have further clarified the conformational dynamics and catalytic mechanisms of splicing, supporting the precise design of high-performance intein modules. On this basis, electrostatic interaction tuning and metagenomic screening have yielded multiple mutually orthogonal split intein pairs, enabling selective multi-fragment protein ligation and providing new routes for the efficient synthesis of large multi-domain functional proteins. With these engineered split inteins offering continuously improved performance and expanded applicability, protein trans-splicing has been widely applied in numerous cutting-edge areas of protein research and biomedicine. In gene delivery, split intein-based systems overcome the packaging limit of adeno-associated viral vectors, enabling the accurate reconstitution of large therapeutic proteins and base editors in target cells, thereby enhancing the efficacy and scope of gene therapy for genetic diseases. In internal protein sequence editing, split inteins mediate precise sequence replacement and modification in flexible regions or loops of target proteins, without the need for complex multi-step ligation and protein refolding involved in traditional protein semisynthesis. In protein-protein interaction studies, intein-mediated splicing covalently captures transient and weak intracellular complexes, enabling sensitive, high-throughput interaction detection and drug screening. In synthetic biology, conditionally controllable splicing systems support the construction of diverse intracellular and cell-surface biological logic gates for the precise regulation of cellular behavior. In mechanistic biochemical research, split inteins enable photocatalytic proximity labeling and site-specific tagging, allowing the preparation of homogeneous protein samples carrying precise post-translational modifications such as ubiquitination and polyglutamylation for chromatin interactome analysis and epigenetic studies. Moreover, covalent trapping strategies using split inteins stabilize transient enzymatic intermediates, providing unprecedented insights into molecular mechanisms such as nucleosome ubiquitination that are difficult to elucidate using conventional methods. This review systematically summarizes key technological advances in split inteins over the past decade, highlighting engineering strategies, mechanistic insights, and the development of orthogonal components. It comprehensively surveys emerging applications at the frontiers of protein research, analyzes current core challenges, and proposes future directions, particularly emphasizing artificial intelligence-driven de novo design and novel splicing pathways to break existing technical bottlenecks. By enabling traceless, efficient, and versatile protein manipulation, split inteins continue to serve as indispensable tools that drive innovation in protein engineering and fundamental life science research.

ObjectiveTo investigate the therapeutic effect of paeoniflorin on metabolic dysfunction-associated fatty liver disease （MASLD） combined with insulin resistance （IR）， and to elucidate its regulatory mechanisms on the Toll-like receptor 4 （TLR4）/nuclear transcription factor （NF）-κB-insulin receptor substrate 1 （IRS1） inflammation-insulin signaling axis. MethodsMASLD mouse model was established using a 60% high-fat diet. Mice were randomly assigned to a normal control group， a MASLD model group， and paeoniflorin groups （low dose： 25 mg·kg^-1·d^-1， medium dose： 50 mg·kg^-1·d^-1， high dose： 100 mg·kg^-1·d^-1）， receiving intragastric administration for consecutive 12 weeks. Concurrently， a palmitic acid/oleic acid （PA/OA）-induced lipid deposition model was established in HepG2 cells. Cell counting kit-8 （CCK-8） assay was performed to determine the optimal concentrations of PA/OA and paeoniflorin for intervention. Mice body weight， liver index， and serum levels of alanine aminotransferase （ALT）， aspartate aminotransferase （AST）， triglycerides （TG）， and total cholesterol （TC） were measured. Fasting blood glucose （FBG） and fasting insulin （FINS） levels were measured， and the homeostatic model assessment of insulin resistance （HOMA-IR） was calculated， while an oral glucose tolerance test （OGTT） was performed to evaluate glucose metabolism. Hematoxylin and eosin （HE） staining was used to observe pathological changes and inflammatory cell infiltration in liver tissue， and oil red O staining was used to evaluate lipid droplet deposition in liver tissue and HepG2 cells. Potential targets were screened using network pharmacology and molecular docking. Western blot analysis was performed to detect the expression of HSP90AA1， TLR4， p-NF-κB p65， p-IRS1， and p-Akt proteins in liver tissue and HepG2 cells. ResultsCompared with the normal control group， mice in the MASLD model group exhibited significantly increased body weight， liver index， and serum levels of ALT， AST， TG， and TC， as well as markedly elevated FBG， FINS， and HOMA-IR， and impaired glucose tolerance （P<0.01）. HE staining revealed marked hepatic steatosis and inflammatory cell infiltration， while oil red O staining showed a significant increase in lipid droplet deposition. Compared with the MASLD model group， after intervention with various doses of paeoniflorin， the increase in body weight and liver index was reduced， serum ALT， AST， TG， and TC levels decreased， and FBG， FINS， and HOMA-IR were significantly lowered， with glucose tolerance markedly improved （P<0.05， P<0.01）， showing a certain dose-dependent trend. HE and oil red O staining results showed a marked reduction in hepatic steatosis and lipid deposition. In vitro experiments demonstrated that， compared with the control group， PA/OA treatment significantly induced increased lipid deposition in HepG2 cells. Compared with the model group， paeoniflorin intervention significantly reduced intracellular lipid droplets， and lipid deposition showed a dose-dependent decreasing trend. Mechanism studies indicated that， compared with the normal control group， the MASLD model group exhibited significantly elevated expression of TLR4， HSP90AA1， and p-NF-κB p65， while p-IRS1 （Ser307） expression was elevated and p-Akt （Ser473） expression was reduced （P<0.01）. Compared with the model group， the expression of the aforementioned proteins was significantly reversed in all treatment groups following intervention （P<0.05， P<0.01）. ConclusionPaeoniflorin significantly alleviates lipid deposition and insulin resistance in MASLD mice. Its mechanism of action may involve targeting HSP90AA1， TLR4， and NF-κB1 to regulate the TLR4/NF-κB-IRS1 inflammation-insulin signaling axis. This regulation suppresses inflammatory responses and restores insulin signaling， thereby ameliorating abnormalities in glucose and lipid metabolism.

ObjectiveTo investigate the therapeutic effect of paeoniflorin on metabolic dysfunction-associated fatty liver disease （MASLD） combined with insulin resistance （IR）， and to elucidate its regulatory mechanisms on the Toll-like receptor 4 （TLR4）/nuclear transcription factor （NF）-κB-insulin receptor substrate 1 （IRS1） inflammation-insulin signaling axis. MethodsMASLD mouse model was established using a 60% high-fat diet. Mice were randomly assigned to a normal control group， a MASLD model group， and paeoniflorin groups （low dose： 25 mg·kg^-1·d^-1， medium dose： 50 mg·kg^-1·d^-1， high dose： 100 mg·kg^-1·d^-1）， receiving intragastric administration for consecutive 12 weeks. Concurrently， a palmitic acid/oleic acid （PA/OA）-induced lipid deposition model was established in HepG2 cells. Cell counting kit-8 （CCK-8） assay was performed to determine the optimal concentrations of PA/OA and paeoniflorin for intervention. Mice body weight， liver index， and serum levels of alanine aminotransferase （ALT）， aspartate aminotransferase （AST）， triglycerides （TG）， and total cholesterol （TC） were measured. Fasting blood glucose （FBG） and fasting insulin （FINS） levels were measured， and the homeostatic model assessment of insulin resistance （HOMA-IR） was calculated， while an oral glucose tolerance test （OGTT） was performed to evaluate glucose metabolism. Hematoxylin and eosin （HE） staining was used to observe pathological changes and inflammatory cell infiltration in liver tissue， and oil red O staining was used to evaluate lipid droplet deposition in liver tissue and HepG2 cells. Potential targets were screened using network pharmacology and molecular docking. Western blot analysis was performed to detect the expression of HSP90AA1， TLR4， p-NF-κB p65， p-IRS1， and p-Akt proteins in liver tissue and HepG2 cells. ResultsCompared with the normal control group， mice in the MASLD model group exhibited significantly increased body weight， liver index， and serum levels of ALT， AST， TG， and TC， as well as markedly elevated FBG， FINS， and HOMA-IR， and impaired glucose tolerance （P<0.01）. HE staining revealed marked hepatic steatosis and inflammatory cell infiltration， while oil red O staining showed a significant increase in lipid droplet deposition. Compared with the MASLD model group， after intervention with various doses of paeoniflorin， the increase in body weight and liver index was reduced， serum ALT， AST， TG， and TC levels decreased， and FBG， FINS， and HOMA-IR were significantly lowered， with glucose tolerance markedly improved （P<0.05， P<0.01）， showing a certain dose-dependent trend. HE and oil red O staining results showed a marked reduction in hepatic steatosis and lipid deposition. In vitro experiments demonstrated that， compared with the control group， PA/OA treatment significantly induced increased lipid deposition in HepG2 cells. Compared with the model group， paeoniflorin intervention significantly reduced intracellular lipid droplets， and lipid deposition showed a dose-dependent decreasing trend. Mechanism studies indicated that， compared with the normal control group， the MASLD model group exhibited significantly elevated expression of TLR4， HSP90AA1， and p-NF-κB p65， while p-IRS1 （Ser307） expression was elevated and p-Akt （Ser473） expression was reduced （P<0.01）. Compared with the model group， the expression of the aforementioned proteins was significantly reversed in all treatment groups following intervention （P<0.05， P<0.01）. ConclusionPaeoniflorin significantly alleviates lipid deposition and insulin resistance in MASLD mice. Its mechanism of action may involve targeting HSP90AA1， TLR4， and NF-κB1 to regulate the TLR4/NF-κB-IRS1 inflammation-insulin signaling axis. This regulation suppresses inflammatory responses and restores insulin signaling， thereby ameliorating abnormalities in glucose and lipid metabolism.

Background/Aims: Endoscopic radiofrequency ablation (ERFA) is a treatment option for superficial esophageal squamous cell neoplasia (ESCN), with a relatively low risk of stenosis; however, the long-term outcomes remain unclear. We aimed to compare the long-term outcomes of patients with widespread superficial ESCN who underwent endoscopic submucosal dissection (ESD) or ERFA. Methods: We retrospectively analyzed the clinical data of patients with superficial ESCN who underwent ESD or ERFA between January 2015 and December 2021. The primary outcome measure was recurrence-free survival. Results: Ninety-two and 33 patients with superficial ESCN underwent ESD and ERFA, respectively. The en bloc, R0, and curative resection rates for ESD were 100.0%, 90.2%, and 76.1%, respectively. At 12 months, the complete response rate was comparable between the two groups (94.6% vs 90.9%, p=0.748). During a median follow-up of 66 months, recurrence-free survival was significantly longer in the ESD group than in the ERFA group (p=0.004), while no significant differences in overall survival (p=0.845) and disease-specific survival (p=0.494) were observed.Preoperative diagnosis of intramucosal cancer (adjusted hazard ratio, 5.55; vs high-grade intraepithelial neoplasia) was an independent predictor of recurrence. Significantly fewer patients in the ERFA group experienced stenosis compare to ESD group (15.2% vs 38.0%, p=0.016). Conclusions The risk of recurrence was higher for ERFA than ESD for ESCN but overall survival was not affected. The risk of esophageal stenosis was significantly lower for patients who underwent ERFA.

Objective:To analyze the clinical characteristics of children with head and neck rhabdomyosarcoma (RMS) and to summarize the mid-long term efficacy of Beijing Children′s Hospital Rhabdomyosarcoma 2006 (BCH-RMS-2006) regimen and China Children′s Cancer Group Rhabdomyosarcoma 2016 (CCCG-RMS-2016) regimen.Methods:A retrospective cohort study. Clinical data of 137 children with newly diagnosed head and neck RMS at Beijing Children′s Hospital, Capital Medical University from March 2013 to December 2021 were collected. Clinical characteristic of patients at disease onset and the therapeutic effects of patients treated with the BCH-RMS-2006 and CCCG-RMS-2016 regimens were compared. The treatments and outcomes of patients with recurrence were also summarized. Survival analysis was performed by Kaplan-Meier method, and Log-Rank test was used for comparison of survival rates between groups.Results:Among 137 patients, there were 80 males (58.4%) and 57 females (41.6%), the age of disease onset was 59 (34, 97) months. The primary site in the orbital, non-orbital non-parameningeal, and parameningeal area were 10 (7.3%), 47 (34.3%), and 80 (58.4%), respectively. Of all patients, 32 cases (23.4%) were treated with the BCH-RMS-2006 regimen and 105 (76.6%) cases were treated with the CCCG-RMS-2016 regimen. The follow-up time for the whole patients was 46 (20, 72) months, and the 5-year progression free survival (PFS) and overall survival (OS) rates for the whole children were (60.4±4.4)% and (69.3±4.0)%, respectively. The 5-year OS rate was higher in the CCCG-RMS-2016 group than in BCH-RMS-2006 group ((73.0±4.5)% vs. (56.6±4.4)%, χ2=4.57, P=0.029). For the parameningeal group, the 5-year OS rate was higher in the CCCG-RMS-2016 group (61 cases) than in BCH-RMS-2006 group (19 cases) ((57.3±7.6)% vs. (32.7±11.8)%, χ2=4.64, P=0.031). For the group with meningeal invasion risk factors, the 5-year OS rate was higher in the CCCG-RMS-2016 group (54 cases) than in BCH-RMS-2006 group (15 cases) ((57.7±7.7)% vs. (30.0±12.3)%, χ2=4.76, P=0.029). Among the 10 cases of orbital RMS, there was no recurrence. In the non-orbital non-parameningeal RMS group (47 cases), there were 13 (27.6%) recurrences, after re-treatment, 7 cases survived. In the parameningeal RMS group (80 cases), there were 40 (50.0%) recurrences, with only 7 cases surviving after re-treatment. Conclusions:The overall prognosis for patients with orbital and non-orbital non-parameningeal RMS is good. However, children with parameningeal RMS have a high recurrence rate, and the effectiveness of re-treatment after recurrence is poor. Compared with the BCH-RMS-2006 regimen, the CCCG-RMS-2016 regimen can improve the treatment efficacy of RMS in the meningeal region.

Objective: To understand the moderating effect of cohabitation with parents on the association between peer dating behavior and sexual behaviors among secondary vocational school students, so as to provide a scientific basis for preventing sexual behaviors among secondary vocational school students. Methods: From March to April 2021, an electronic questionnaire survey was conducted among 3 180 students from 6 vocational schools in Shanghai (urban, suburban, exurban) and Shaanxi (Shangluo, Ankang, Baoji) using cluster sampling. Spearman correlation analysis was used to investigate the relationship of cohabitation with parents, peer dating behavior and sexual behaviors among secondary vocational school students. Binary Logistic regression analysis was performed to investigate the role of cohabitation with parents on peer dating behavior and sexual behaviors among secondary vocational students. Results: There was a significant negative between cohabitation with parents and sexual ( r =-0.04); and there was a positive correlation between peer dating behavior and sexual behaviors ( r =0.24), as well as cohabitation with parents and peer dating behavior ( r =0.04)( P <0.05). Multivariable Logistic regression analysis showed an association between peer dating behavior and the occurrence of sexual behaviors ( OR=2.79-12.95, P <0.05). Cohabitation with parents played a moderating role in the association between peer dating behavior and sexual behaviors, and a signification interaction was found between cohabitation with parents and reporting that a small part or about half of their peers had dating behavior ( OR =0.48, P <0.05). Conclusions The more peers dating behavior are associated with a higher risk of sexual behaviors among secondary vocational school students, and cohabitation with parents can partly reduce this risk. School and family sexuality education for secondary vocational students should be strengthened to improve their interpersonal skills and decision-making, and ability to resist peer pressure, so as to reduce their risk of sexual behaviors.

Non-steroidal anti-inflammatory drugs(NSAIDs),commonly utilized analgesics,are extensively employed for managing pain associated with musculoskeletal disorders or injuries.Recent clinical studies have demonstrated a heightened risk of bone stress injuries(BSI)in soldiers and athletes,particularly during high-intensity training,due to NSAID usage.Furthermore,the impact of NSAIDs on fracture healing is well-documented;however,the precise mechanism by which their use during training contributes to an increased incidence of stress bone injuries remains unclear.This article aims to summarize potential mechanisms through an extensive review of domestic and international literature in order to standardize the utilization and clinical management of NSAIDs,optimize pain management strategies,and prevent stress bone injuries or fractures in specific populations such as soldiers and elite athletes.

Heat stroke is a heat-related illness caused by an imbalance between the body's heat production and heat dissipation,which could lead to multiple organ dysfunction syndrome with a high mortality rate.Rapid and effective reduction of core body temperature is key to successful treatment.This article reviews recent progress in the treatment of heat stroke,including new understandings of organ injury mechanisms,the timing,velocity and goals of cooling treatment,evaluation and selection of traditional cooling techniques(such as cold water immersion),and scientific evaluation of new cooling technologies(such as blood purification technology and intravascular heat exchange cooling technology),aiming to promote understanding and treatment of heat stroke.

Objective To investigate the effect of splenectomy on the repair of full-thickness skin tissue defects,as well as the impact of different recovery times after splenectomy on the healing of skin tissue defects.Methods According to a random number table,39 8-week-old female C57 mice were randomly divided into three groups:sham surgery group(sham group,n=13),splenectomy group with 3 days of recovery(Spx3d group,n=13),and splenectomy group with 3 weeks of recovery(Spx3w group,n=13).Full-thickness skin defects were created on the backs of the mice in each group.The wound healing conditions at different times after skin defects were observed,and the wound healing rates after the injury were calculated.Peripheral blood cell analysis was performed on day 14 after the defect,and tissue samples from the wound area were taken for hematoxylin and eosin(HE)staining to observe the granulation tissue thickness at the defect site and the re-epithelialization rate.Masson's trichrome staining was used to observe the proportion of collagen fibers.Results After splenectomy and sham surgery,the mice recovered well without significant discomfort.From 1 to 14 days after the skin defect modeling,the wound areas of the mice in all three groups gradually decreased.Compared with sham group,the wound areas were smaller in Spx3d and Spx3w groups at 3,5 and 7 days after the injury,and the differences were statistically significant(P<0.05).The wound healing rates were also significantly higher(P<0.05).Moreover,at 3 days and 5 days after the injury,the wound healing rates of Spx3d group were significantly higher than those of Spx3w group(P<0.05 or P<0.01).The peripheral blood white blood cell(WBC)count in Spx3w group was significantly higher than that in sham group and Spx3d group(P<0.01).The platelet counts in both sham group and Spx3w group were significantly higher than that in Spx3d group(P<0.05).Additionally,the lymphocyte and neutrophil counts in Spx3w group were markedly higher than those in sham group(P<0.05).No statistically significant differences in red blood cell(RBC)counts were observed among the three groups(P>0.05).HE staining results showed that compared with sham group,the wound healing of the mice in Spx3d and Spx3w groups were better,and the thickness of the granulation tissue in Spx3d group were better than that in Spx3w group.At 7 days,the thickness of the granulation tissue in Spx3d and Spx3w groups was significantly higher than that in sham group(P<0.01,P<0.05)and the re-epithelialization rate in Spx3d group was significantly higher than that in sham group and Spx3w group(P<0.05).At 14 days,the re-epithelialization rates of Spx3d and Spx3w groups were significantly higher than those of sham group(P<0.05).The results of Masson's staining showed that the collagen fiber proportion in the wounds of Spx3d group at 7 and 14 days and that of Spx3w group at 14 days were significantly higher than that in sham group(P<0.05).Conclusion The healing of skin defects in mice is accelerated after splenectomy,and the recovery time after splenectomy has a certain effect on the healing of skin defects.

Objective To investigate the clinical characteristics of patients with clinical and subclinical Cushing's syndrome caused by primary bilateral macronodular adrenal hyperplasia(PBMAH).Methods A retrospective analysis was performed on the clinical data of 198 patients with Cushing's syndrome caused by PBMAH diagnosed in the First Medical Center of Chinese PLA General Hospital from January 2004 to October 2024.According to clinical manifestations,the patients were classified into clinical type Cushing's syndrome(n=61)and subclinical type Cushing's syndrome(n=137),and the clinical characteristics of the two types were compared.Results The mean age at diagnosis of patients with PBMAH-induced Cushing's syndrome was(53.5±10.4)years,including 118 males and 80 females,with a male-to-female ratio of 1.475:1.Compared with the subclinical type,the clinical type had a higher proportion of females,higher levels of serum cortisol,24-hour urine free cortisol(24 h UFC),and inhibited serum cortisol after low-dose dexamethasone suppression.Additionally,the clinical type had lower plasma ACTH,larger adrenal nodules and a higher risk of surgery(P<0.05)compared with those in subclinical type.The incidences of hypertension,dyslipidemia,obesity,diabetes mellitus,hypokalemia,vitamin D deficiency,osteoporosis,coronary heart disease,and cerebrovascular disease in patients with Cushing's syndrome caused by PBMAH were 87.9%,50.5%,37.1%,36.9%,27.8%,25.9%,18.7%,18.7%and 12.1%,respectively.Among them,compared with subclinical type patients,clinical type patients had higher incidence of hypokalaemia,vitamin D deficiency and osteoporosis(P<0.05),while there were no statistically significant differences in the incidences of other comorbidities between the two types(P>0.05).The results of postoperative follow-up for PBMAH patients showed that the short-term biochemical remission rate of unilateral total adrenalectomy was 41.5%(22/53)and the long-term biochemical remission rate was 32.0%(8/25).The short-term biochemical remission rate of unilateral partial(or nodular)adrenalectomy was 52.9%(9/17),and the long-term biochemical remission rate was 14.3%(1/7).All patients who underwent unilateral total adrenalectomy plus contralateral partial resection developed adrenal insufficiency(3/3),and 1 patient(1/3)relapsed 3.4 years after surgery.Conclusion Clinical and subclinical types of Cushing's syndrome caused by PBMAH have their distinct clinical characteristics.Surgery is an effective treatment for PBMAH,but a certain proportion of patients fail to achieve biochemical remission after non-bilateral total adrenalectomy.