Impact of fast-track surgery-oriented care pathways on perioperative rehabilitation indices in patients undergoing radical prostatectomy for prostate cancer.

OBJECTIVE: This study was conducted to evaluate the effects of Fast-Track Surgery (FTS)-oriented care pathways on perioperative rehabilitation indicators in patients undergoing radical prostatectomy for prostate cancer. METHODS: The clinical data of 120 patients admitted to Sichuan Cancer Hospital & Institute who underwent radical prostatectomy for prostate cancer from September 2020 to October 2022 were collected and retrospectively analyzed. The patients were divided into a control group (n=60, receiving standard care) and an FTS group (n=60 patients receiving FTS-oriented care) according to different nursing methods. The perioperative rehabilitation indices were compared between the groups. RESULTS: The FTS group exhibited shorter hospitalization duration (P=0.001), postoperative anal exhaust time (P=0.012), drain removal time (P=0.007), gastrointestinal recovery time (P=0.008), and a lower total complication rate (P=0.016) compared to the control group. The scores of Visual Analog Scale (VAS) (P=0.001, P=0.003, P=0.015) and Activities of Daily Living (ADL) (P=0.011, P=0.005, P=0.007) at 24, 48, and 72 hours postoperatively were significantly lower in the FTS group than in the control group. Hospitalization cost (P=0.002) and medication expenses (P=0.016) were notably lower in the FTS group. During a 12-month follow-up, the FTS group showed a significantly lower complication rates (3.33%) compared to the control group (18.33%) (P=0.009). CONCLUSION: The application of FTS-oriented nursing pathway in patients undergoing radical prostatectomy for prostate cancer significantly enhances postoperative rehabilitation, reduces pain, lowers hospitalization and medication costs, and improves postoperative quality of life, which contributes positively to the nurse-patient relationship and patient outcome.

Microarray analysis of microrna expression in peripheral blood mononuclear cells of patients with polymyositis and dermatomyositis.

Background and Objectives: MicroRNAs (miRNAs) represent a new class of biomarkers in the context of connective tissue disorders. The miRNA expression profiles in peripheral blood mononuclear cells (PBMCs) of patients with polymyositis (PM) and dermatomyositis (DM) have not been fully elucidated. The objective is to investigate miRNAs expression profile in PBMCs of patients with PM/DM. Methods: Microarray technology was used to identify differentially expressed miRNAs in PBMCs obtained from 6 untreated PM/DM patients and 3 healthy controls (HCs). TaqMan-based stem-loop real-time PCR detection was used for validation in a cohort of 34 PM/DM patients and 20 HCs. Results: Microarray analysis revealed 38 differentially expressed miRNAs (24 up-regulated and 14 down-regulated) in PM/DM patients compared to HCs. Four miRNAs (miR-320a, miR-335-3p, miR-34a-5p and miR-454-3p) were chosen for real-time PCR validation. The expression of miR-34a-5p was significantly upregulated in PM/DM group (P < 0.05). In subgroup analysis, miR-34a-5p was significantly upregulated in interstitial lung disease (ILD) group and DM group (P < 0.001). The level of SIRT1, a validated target of miR-34a, was significantly lower in PBMCs of PM/DM patients compared with HCs. Conclusions: MiR-34a-5p may potentially participate in the pathogenesis of PM/DM through SIRT1, and may serve as a potential new biomarker for PM/DM-ILD.

Spontaneous pneumomediastinum in anti-MDA5-positive dermatomyositis: Prevalence, risk factors, and prognosis.

OBJECTIVE: To depict the clinical panorama of spontaneous pneumomediastinum (SPM) in anti-MDA5 antibody-positive dermatomyositis (anti-MDA5+ DM). METHODS: A total of 1352 patients with idiopathic inflammatory myopathy (IIM), including 384 anti-MDA5+ DM patients were retrospectively enrolled. The clinical profiles of anti-MDA5+ DM-associated SPM were analyzed. RESULTS: We identified that 9.4 % (36/384) of anti-MDA5+ DM patients were complicated with SPM, which was significantly higher than that of non-anti-MDA5+ DM and other IIM subtypes (P all <0.001). SPM developed at a median of 5.5 (3.0, 12.0) months after anti-MDA5+ DM onset. Anti-MDA5+ DM patients complicated with SPM showed a significantly higher frequency of fever, dyspnea, and pulmonary infection including viral and fungal infections compared to those without SPM (P all < 0.05). Cytomegalovirus (CMV) and fungal infections were identified to be independent risk factors for SPM development in the anti-MDA5+ DM. SPM and non-SPM patients in our anti-MDA5+ DM cohort showed comparable short-term and long-term survival (P = 0.236). Furthermore, in the SPM group, we found that the non-survivors had a lower peripheral lymphocyte count, higher LDH level, and higher frequency of intensification of immunosuppressive treatment (IST) than survivors. The elevated LDH level and intensification of IST were independent risk factors for increased mortality in anti-MDA5+ DM-associated SPM patients. CONCLUSIONS: Nearly one-tenth of patients with anti-MDA5+ DM develop SPM. Both CMV and fungal infections are risk factors for SPM occurrence. The development of SPM does not worsen the prognosis of anti-MDA5+ DM patients, and the intensification of IST does harm to the SPM prognosis.

High prevalence and mortality of Pneumocystis jirovecii pneumonia in anti-MDA5 antibody-positive dermatomyositis.

OBJECTIVES: To identify potential risk factors and prognostic factors of Pneumocystis jirovecii pneumonia (PJP) infection in anti-melanoma differentiation-associated gene 5 antibody-positive DM (anti-MDA5+ DM) patients, and to evaluate the diagnostic performance of metagenomic next-generation sequencing (mNGS). METHODS: Anti-MDA5+ DM patients who underwent mNGS or real-time PCR for PJP detection were recruited. The potential risk factors for PJP occurrence and death were analysed via Logistic regression and Cox proportional hazards regression, respectively. The diagnostic efficacy of mNGS was compared with the conventional methods. RESULTS: 91 patients were enrolled and 44 were assigned to PJP+ group. The PJP detection rate was 48.4%. PJP often occurred in the first 3 months (68.2%) of the disease; this period also showed the highest mortality rate (20.5%). Fever and increased lactate dehydrogenase (LDH) were independent risk factors for PJP occurrence, while trimethoprim-sulfamethoxazole (TMP/SMZ) prophylaxis was an independent protective factor (all P < 0.05). Older age and increased LDH were predictors for mortality in patients with anti-MDA5+ DM and PJP (all P < 0.05). In addition, we found that mNGS had a sensitivity of 100.0% and specificity of 90.0% in diagnosing PJP, with the highest area under the curve of 0.95 (P < 0.001). CONCLUSION: PJP has high prevalence and mortality in anti-MDA5+ DM. It is crucial for clinicians to identify high-risk patients and promptly institute TMP/SMZ to prevent PJP. mNGS is the preferred approach for pathogen detection in anti-MDA5+ DM when PJP is suspected.

Regioselective Synthesis of Indole-Fused Seven-Membered N-Heterocycles via Photoredox-Catalyzed Intramolecular Cyclization.

Herein, we describe the construction of indole-fused seven-membered N- and O-heterocycles from indolyl α-diazocarbonyls via photoredox-catalyzed intramolecular cyclization. The photoredox process features operational simplicity, mild conditions, and as low as 0.1 mol % catalyst loading. The tricyclic heterocycles are obtained in yields of 24 to 67% with excellent regioselectivity. The practicality of this protocol is further demonstrated by gram-scale reactions carried out in both batch and continuous flow.

Clinical Heterogeneity of Patients With Antinuclear Matrix Protein 2 Antibody-Positive Myositis: A Retrospective Cohort Study in China.

OBJECTIVE: Heterogeneity exists among patients with myositis who have antinuclear matrix protein 2 (anti-NXP2) antibodies, although they usually present with severe muscle weakness. This study aimed to investigate the differences in phenotypes and prognoses among adult patients with myositis who have anti-NXP2 antibodies. METHODS: Adult patients with myositis who have anti-NXP2 antibodies were enrolled from January 2010 to December 2019. Their clinical features and laboratory data were recorded retrospectively. We followed up on their survival status until June 30, 2020. A hierarchical cluster analysis, Kaplan-Meier curves, and classification and regression trees were used to analyze the data. RESULTS: A total of 70 adult patients with myositis who have anti-NXP2 antibodies were enrolled. All patients experienced muscle weakness. A total of 11 patients did not present with rashes during disease progression, and 43 patients developed dysphagia. In total, 21 patients had interstitial lung disease (ILD), whereas no patients had rapidly progressive ILD. Hierarchical cluster analysis identified 2 clusters. Patients in cluster 1 were younger at disease onset, had a higher incidence of subcutaneous calcification, and had a lower incidence of V sign and shawl sign. Patients in cluster 2 had a higher frequency of ILD, accompanied by lower levels of lymphocytes and higher levels of serum ferritin. Moreover, patients in cluster 2 had worse prognoses. CONCLUSION: Patients with myositis who have anti-NXP2 antibodies may present with different phenotypes that are characterized by unique features and prognoses.

Clinical role of bronchoalveolar lavage in dermatomyositis-associated interstitial lung disease.

OBJECTIVE: To investigate the role of bronchoalveolar lavage (BAL) in DM-associated interstitial lung disease (ILD). METHODS: We retrospectively reviewed the medical records of patients with DM-ILD who underwent bronchoscopy between October 2015 and September 2019. We then collated clinical features, laboratory data and bronchoscopy findings. The follow-up study was terminated on the 1 May 2020. RESULTS: A total of 113 DM-ILD patients were included in this study, including 27 patients with acute/subacute interstitial pneumonia (A/SIP) and 86 patients with chronic interstitial pneumonia (CIP). The A/SIP group had significantly lower proportions of lymphocytes and eosinophils in the bronchoalveolar lavage fluid (BALF) than the CIP group, but had a significantly higher proportion of neutrophils. Pathogens were discovered in BALF from 28 (24.8%) patients. Twenty-five (22.1%) patients commenced or changed antibiotic therapy on the basis of their bronchoscopy results. Lymphopenia and intensive care unit care were significantly associated with pathogen-positive BALF findings. Complications of bronchoscopy occurred in nine (8.0%) patients; fever (5.3%) was the most common complication. Twenty-five deaths (25/106, 23.6%) were observed during a mean follow-up of 22 months. Age, A/SIP and anti-MDA5 antibody were identified as independent predictors of a poor outcome, while mechanic's hands was an independent protective factor. However, cellular and pathogen findings in BALF had no significant influence on 30-day or overall mortality. CONCLUSION: Bronchoscopy is a relatively useful instrument to evaluate ILD in patients with DM, and BAL can improve the diagnosis of infection. However, cellular and pathogen findings from BALF had no significant influence on prognosis.

The effects of infliximab in treating idiopathic inflammatory myopathies: A review article.

Anti-TNF treatment may be useful for patients with idiopathic inflammatory myopathies (IIMs). The purpose of this study is to assess the efficacy of infliximab (IFX) in the management of IIMs. Two databases (ie, PubMed and China National Knowledge Infrastructure) were searched up to Nov 2020 for studies investigating skin lesions and muscular weakness in patients with IIMs treated with IFX. A total of 18 studies were included. One hundred and eighteen patients were identified, including 58 adult patients and 60 patients with juvenile dermatomyositis (JDM) treated with IFX. Among these patients, 110 (93%) patients with refractory cases. In addition to glucocorticoids, patients from 15/18 studies received immunosuppressant agents (ISAs) concomitantly with IFX, among which methotrexate (MTX) was most common. After treatment with IFX, skin lesions and muscle strength were improved in 67% of patients with DM and 75% of patients with JDM, respectively. Skin calcinosis was improved in 21/34 (62%) of patients with JDM. Only 55% (12/22) of patients with polymyositis exhibited improvements in muscle strength. Lastly, 40% (42/104) of patients reported adverse events. Current evidence appears to support the use of IFX in some patients with refractory IIMs, especially those with JDM. The most common adverse reaction was infection. Large, randomized-controlled studies should be carried out to confirm these findings.

The Efficacy of Tocilizumab in the Treatment of Patients with Refractory Immune-Mediated Necrotizing Myopathies: An Open-Label Pilot Study.

Objective: To evaluate the efficacy of tocilizumab (TCZ) in adult patients with refractory immune-mediated necrotizing myopathies (IMNMs) and investigate possible predictive biomarkers of the response to treatment with TCZ. Methods: Patients with refractory IMNM were enrolled in this open-label pilot observational study and received intravenous TCZ treatment. The clinical response was assessed after 6 months of TCZ treatment according to the 2016 American College of Rheumatology-European League Against Rheumatism (ACR-EULAR) response criteria for adult dermatomyositis and polymyositis. Muscle biopsies were performed to investigate muscle fiber regeneration by immunohistochemical staining of CD56. Serum levels of interleukin (IL)-6 were measured using a multiplex bead-based flow fluorescent immunoassay. The levels of muscle IL-6 mRNA were detected by real-time polymerase chain reaction. Results: A total of 11 patients with refractory IMNM were enrolled in the study, including 3 anti-3-hydroxy-3-methylglutaryl-CoA reductase- and 8 anti-signal recognition particle-positive patients. Seven (63.6%) of these patients achieved clinically significant responses according to the 2016 ACR-EULAR myositis response criteria. Responders had higher baseline serum IL-6 and muscle IL-6 mRNA levels and percentage of CD56-positive muscle fibers than non-responders. Baseline serum IL-6 levels and the percentage of CD56-positive muscle fibers were positively correlated with total improvement score after 6 months of TCZ treatment. Furthermore, muscle fiber necrosis and muscle fiber size variation decreased in repeated muscle biopsies in five responders. Conclusion: Patients with refractory IMNM may respond to TCZ. Baseline serum IL-6 and muscle IL-6 mRNA levels and the percentage of CD56-positive muscle fibers may predict the response to TCZ treatment in these patients.

Anti-melanoma differentiation-associated gene 5 (MDA5) antibody-positive dermatomyositis responds to rituximab therapy.

OBJECTIVES: The purpose of this study was to assess the efficacy of rituximab (RTX) in the management of anti-melanoma differentiation-associated gene 5 (anti-MDA5) antibody-positive dermatomyositis (DM), with or without rapidly progressive interstitial lung disease (RP-ILD). METHODS: Medical records of DM patients with anti-MDA5 antibodies treated with RTX therapy were reviewed retrospectively. Skin rash data, lung function tests, chest high-resolution computed tomography (HRCT), and serum markers were compared before and after RTX. RESULTS: Eleven consecutive cases, including 5 males and 6 females, were identified. One hundred percent of patients had a typical DM rash and about 45% presented with skin ulceration. All the patients had ILD, 73% had RP-ILD, and 27% had mild or asymptomatic ILD. Ro-52 antibodies were found in 55% of this group. Lymphopenia was present in 10/11 patients (91%). Around half (55%) had a level of ferritin greater than 1000 ng/ml. Nine patients (82%) were refractory. These patients received intravenous RTX (375 mg/m2) at 0 and 14 days (conventional dose) or 100 mg once a week for 4 weeks (low dose). After RTX treatment, 2 patients (18%) with mild ILD showed complete remission, and 6 (55%) showed improvement in lung HRCT and/or lung function. Skin rash in 4 patients (100%) and ILD in 3 (75%) showed improvement in the low-dose group. Infection episodes occurred in four (57%) and one (25%) of the conventional-dose and low-dose group, respectively. CONCLUSIONS: Our study found that RTX is sufficient to improve skin rash and ILD or RP-ILD. Our results also suggest that lower RTX doses may be a useful therapy for anti-MDA5 antibody-positive DM patients. Key Points • To clarify efficacy of RTX in the management of anti-MDA5 antibody-positive DM, we performed a retrospective chart review of DM patients with anti-MDA5 antibodies who were treated with RTX. • This study found that RTX is sufficient to improve skin rash and ILD or RP-ILD. • The results suggest that low-dose RTX in treatment of MDA5-DM results in better responses and fewer adverse events.

Interstitial Lung Disease Is a Major Characteristic of Patients Who Test Positive for Anti-PM/Scl Antibody.

OBJECTIVE: This study aimed to analyze the clinical features of anti-PM/Scl antibodies in Chinese patients. METHOD: We reviewed the clinical data of anti-PM/Scl antibody-positive patients, including their long-term follow-up. RESULTS: A total of 30 patients carried anti-PM/Scl antibodies, 21 (70%) were females, and the mean age was 55.4 years, 15 (50%) and 10 (33.3%) patients were positive for anti-PM/Scl-75 and anti-PM/Scl-100, respectively. Fifteen cases (50%) were diagnosed as inflammatory myopathy, namely, 11 dermatomyositis (DM) and 4 polymyositis (PM). Five (16.7%) patients were diagnosed with overlap syndrome, and only one (3.3%) was diagnosed as systemic sclerosis. The other 9 (30%) patients were classified as undifferentiated connective tissue disease. Twenty-six (86.7%) had interstitial lung disease (ILD) and was the sole manifestation in 8 (26.7%) patients, 15 (58.0%) showed non-specific interstitial pneumonia based on high-resolution CT or lung biopsy. The majority of patients (95%) with mild and moderate groups on basis of pulmonary function tests. Compared to the anti-PM/Scl-100 group, the occurrence of clinical characteristics was not significantly different from the anti-PM/Scl-75 group, except the levels of C-reactive protein and erythrocyte sedimentation rate in the anti-PM/Scl-75 antibody-positive group were higher (p < 0.05). All patients with positive Ro-52 antibodies had ILD and were more likely to develop skin rash in the group with Ro-52 (p = 0.024). With a follow-up of the present cohort, 70.8% improved with treatment, but 16.7% of patients are easy to relapse. CONCLUSION: The anti-PM/Scl antibody occurred frequently in DM/PM patients, ILD was the major clinical feature, especially in patients combined with Ro-52. Some patients may complicate with ILD alone without extrapulmonary manifestations. Anti-PM/Scl antibodies positive patients were responsive to treatment.

Interstitial lung disease is a major characteristic of anti-KS associated ant-synthetase syndrome.

BACKGROUND: Anti-KS autoantibodies are rare myositis-specific autoantibodies that have been described to target asparaginyl-transfer RNA synthetase. METHODS: Here, we review the published literature on critical issues concerning the detection of anti-KS antibodies and the clinical features associated with their presence. RESULTS: Seven articles are reviewed, in all of which immunoprecipitation was employed for the detection of anti-KS antibodies. A total of 47 patients were included; the ratio of females to males was 1.9:1. In total, 46 (98%) of these patients had interstitial lung disease (ILD), which was the sole manifestation in half (50%) of them. Pulmonary pathology revealed 7 (27%) with usual interstitial pneumonia, and 16 (62%) with non-specific pneumonia. Arthritis was present in about one-quarter (26%) of patients, and the incidence of Raynaud's phenomenon and mechanic's hands was 19% and 32%, respectively. However, manifestations of myositis were rare (9%). In addition, three (11%) patients had malignant tumors. Most patients responded to glucocorticoid therapy. CONCLUSIONS: Identifying anti-KS in patients with ILD may be useful for treatment, but reliable practical detection is needed. Furthermore, clinicians need to be aware of the possible presence of anti-KS antibodies in patients with ILD, either isolated or in combination with myositis.

Coexistence of Axial Spondyloarthritis and Idiopathic Inflammatory Myopathy.

Both axial spondyloarthritis (axSpA) and idiopathic inflammatory myopathy (IIM) are infrequent, and their coexistence is even rarer; there are a few reported cases in the literature. The aim of this study was to assess their association and clinical and laboratory features in our patients. The clinical data of patients with axSpA and IIM diagnosed in China-Japan Friendship Hospital from July 2015 to February 2019 were retrospectively analyzed. This study included 7 patients with axSpA who met the IIM criteria, including 3 males and 4 females. The age of onset was 16 to 39 years. Four patients were HLA-B27 positive, and three were negative. All patients were first diagnosed as axSpA, and then IIM was detected after 0.5-20 years (mean ± SD, 9.9 ± 5.0 years). After being diagnosed to have axSpA and IIM, those patients were given prednisone and immunosuppressant drugs, and their symptoms gradually improved. Our study provides further evidence of the coexistence of IIM with axSpA. In patients with axSpA who have skin rash, interstitial lung disease (ILD), myalgia, or muscle weakness, we should suspect that they may have IIM.

Soluble IL-2 Receptor in Dermatomyositis: Its Associations with Skin Ulcers and Disease Activity.

OBJECTIVE: To investigate the role of soluble interleukin-2R (sIL-2R) in idiopathic inflammatory myopathies (IIM). METHODS: Serum sIL-2R levels were measured in 74 dermatomyositis (DM), 16 immune-mediated necrotizing myopathy (IMNM), 24 rheumatoid arthritis (RA), 20 systemic lupus erythematosus (SLE), and 20 healthy controls (HCs) by chemiluminescent immunometric assay. Clinical features and laboratory data were collected from electronic medical record. Disease activity was evaluated by using physician global disease activity and myositis disease activity assessment visual analog scale (MYOACT) on admission. 20 DM patients were followed. Serum sIL-2R levels were analyzed and compared with clinical features, laboratory data, and measures of disease activity. RESULTS: Serum sIL-2R levels were significantly higher in DM patients than in IMNM patients and HCs (648.8 ± 433.1 U/ml vs. 352.3 ± 126.0 U/ml and 648.8 ± 433.1 U/ml vs. 285.8 ± 101.9 U/ml, respectively; all P < 0.001), while there was no significant difference between IMNM and HCs. There were also no significant differences of sIL-2R levels in DM, SLE, and RA. Importantly, serum sIL-2R levels were significantly higher in treatment-naïve or active DM patients than those that are not (1100.9 ± 550.4 U/ml vs. 615.6 ± 330.4 U/ml, P = 0.006; 808.8 ± 421.6 U/ml vs. 339.8 ± 103.4 U/ml, P < 0.001). DM patients with skin ulcers had significantly higher sIL-2R levels than those without (889.3 ± 509.9 U/ml vs. 640.0 ± 368.7 U/ml, P = 0.023). Cross-sectional analysis in DM showed that sIL-2R levels positively correlated with CK, ESR, CRP, ferritin, physician VAS, and MYOACT scores (rho = 0.278, rho = 0.474, rho = 0.469, rho = 0.454, r = 0.646, and r = 0.600, respectively; all P < 0.05), negatively correlated with T cell counts and MMT8 scores (r = -0.380, P = 0.002; rho = -0.394, P = 0.001). Follow-up study showed that changes in sIL-2R levels after treatment correlated with changes in physician VAS and MYOACT scores (r = 0.823 and r = 0.695, respectively; all P < 0.01). CONCLUSION: Serum sIL-2R levels were elevated in DM but not in IMNM. Serum sIL-2R could act as a disease activity marker and be associated with ulcerative skin lesions in DM.

Hospitalization mortality and associated risk factors in patients with polymyositis and dermatomyositis: A retrospective case-control study.

BACKGROUND: Polymyositis and dermatomyositis (PM/DM) are systemic autoimmune diseases with multiple organ involvements that manifest as muscular and cutaneous disorders, interstitial lung disease (ILD) and malignancies. However, information concerning the outcomes and associated factors for PM/DM patients who are hospitalized is limited. METHODS: We retrospectively reviewed the medical charts of PM/DM patients admitted to a Chinese tertiary referral hospital (Peking Union Medical College Hospital, PUMCH) from 2008 to 2014. The deceased group included 63 patients who had "deceased discharge" status or were confirmed to have died within two weeks of hospital discharge. The demographic data, clinical manifestations, and direct causes of death were analyzed retrospectively. Medical records for 126 age- and sex-matched PM/DM patients were selected as controls from 982 inpatients successively admitted to the same center during the same period. In addition to the comparison of clinical manifestations between the two groups, binary logistic regression was conducted to explore the risk factors related to PM/DM mortality. RESULTS: Over the past 6 years at PUMCH, the in-hospital mortality rate of PM/DM patients was 4.58%. The male gender and the elder patients had a high risk of death (P = 0.031 and P = 0.001 respectively). The three most frequent causes of death for PM/DM patients were pulmonary infection (35%), ILD exacerbation (21%) or both conditions (25%). Pulmonary infection (P<0.001, OR = 5.63, 95% CI, 2.37-13.36), pneumomediastinum (P = 0.041, OR = 11.02, 95%CI, 1.10-110.54), Gottron's papules (P = 0.010, OR = 3.24, 95%CI, 1.32-7.97), and elevated erythrocyte sedimentation rate (ESR) (P = 0.005, OR = 9.9, 95%CI 2.0-49.0) were independent risk factors for in-hospital mortality of PM/DM patients. CONCLUSION: PM/DM patients continue to display high in-hospital mortality. Pulmonary infection is the strongest predictor of poor prognosis in PM/DM patients, followed by pneumomediastinum, Gottron's papules, and elevated ESR.

Integrin activation and internalization on soft ECM as a mechanism of induction of stem cell differentiation by ECM elasticity.

The mechanism by which ECM elasticity induces lineage specification of stem cells has not been clearly understood. Integrins are well-documented mechanosensors that are positioned at the beginning of the sensing pathway. By using an antibody specifically recognizing the active conformation of ß1 integrin, we observed that ß1 integrin activation in bone marrow mesenchymal stem cells (BMMSCs) was induced by soft substrate to a significantly greater degree than by stiff substrate. In contrast, however, the level of cell surface integrin on soft substrate was significantly lower than that on stiff substrate. Soft substrate markedly enhanced the internalization of integrin, and this internalization was mediated mainly through caveolae/raft-dependent endocytosis. The inhibition of integrin internalization blocked the neural lineage specification of BMMSCs on soft substrate. Furthermore, soft substrate also repressed the bone morphogenetic protein (BMP)/Smad pathway at least partially through integrin-regulated BMP receptor endocytosis. A theoretical analysis based on atomic force microscopy (AFM) data indicated that integrin-ligand complexes are more easily ruptured on soft substrate; this outcome may contribute to the enhancement of integrin internalization on soft substrate. Taken together, our results suggest that ECM elasticity affects integrin activity and trafficking to modulate integrin BMP receptor internalization, thus contributing to stem cell lineage specification.