Pediatric-inspired regimen for adolescent and adult patients with Philadelphia chromosome-negative acute lymphoblastic leukemia: a prospective study from China.

Several international centers have used and reported pediatric-inspired regimens for adolescent and adult patients with Philadelphia chromosome-negative acute lymphoblastic leukemia (Ph- ALL). However, there is a lack of prospective data on the Chinese population. Herein, we performed a prospective study with a pediatric-inspired regimen (IH-2014 regimen) in treating adolescent and adult Ph- ALL patients in our center. From 2014 to 2021, a total of 415 patients aged between 14 and 65 years (median age, 27) were included in this study. After a median follow-up of 40.8 months, the 5-year overall survival, disease-free survival, and event-free survival rates were 53.8%, 51.1% and 45.0%, respectively. The regimen was generally well tolerated and safe, and the overall chemotherapy-related mortality was 3.6%. Age ≥ 40 years and persistent detectable minimal residual disease (MRD) post-induction were independent prognostic factors. Traditional risk factors for adult patients combined with MRD post-induction exhibit predictive significance for survival and relapse, which is helpful in the selection of subsequent treatment. Patients with high risk factors who can achieve deep MRD response after induction do not derive benefit from allogeneic hematopoietic stem cell transplantation.

Toll-like receptor activation regulates the paracrine effect of adipose-derived mesenchymal stem cells on reversing osteoarthritic phenotype of chondrocytes.

BACKGROUND: The therapeutic efficacy of intra-articular mesenchymal stem cells (MSCs) injection for patients with osteoarthritis (OA) currently exhibits inconsistency, and the underlying mechanism remains elusive. It has been postulated that the immunomodulatory properties and paracrine activity of MSCs might be influenced by the inflammatory micro-environment within osteoarthritic joints, potentially contributing to this observed inconsistency. METHODS: Adipose-derived MSCs (ADSCs) were isolated from SD rats and pre-treated with Toll-like receptor 3 (TLR3) agonist Poly I:C or Toll-like receptor 4 (TLR4) agonist LPS. The pre-treated ADSCs were then co-cultured with IL-1ß-induced osteoarthritic chondrocytes using a Transwell system to analyze the paracrine effect of ADSCs on reversing the osteoarthritic phenotype of chondrocytes. RESULTS: RT-PCR and Western blot analysis revealed that Poly I:C and LPS pre-treatments up-regulated the expression of IL-10 and IL-6 in ADSCs, respectively. Furthermore, only Poly I:C-preconditioned ADSCs significantly promoted proliferation while inhibiting apoptosis in IL-1ß-treated chondrocytes. Additionally, Poly I:C-preconditioned ADSCs downregulated MMP13 expression while upregulating aggrecan and collagen II expression levels in IL-1ß-treated chondrocytes. CONCLUSIONS: TLR3 activation polarizes ADSCs into an immunomodulatory phenotype distinct from TLR4 activation, exerting differential effects on reversing the osteoarthritic phenotype of chondrocytes; thus indicating that MSCs' paracrine effect regulated by TLRs signaling impacts the efficacy of intra-articular MSCs injection.

Macrophage migration inhibitory factor reversed senescent phenotype in human chondrocytes in vitro.

BACKGROUND: The senescence of chondrocytes, which is closely linked to the development of osteoarthritis (OA), has been found to be influenced by the inflammatory environment of joint cavity. However, there remains a lack of comprehensive understanding regarding the specific mechanisms through which cytokine impacts chondrocytes senescence. PURPOSE: To investigate the effects of MIF on the chondrocytes senescence and explore the underlying mechanism. METHODS: Human cytokine array and ELISA were used for the level of MIF in synovium fluid. CCK-8 was used for chondrocytes viability. IF, WB, SA-ß-gal staining and flow cytometry were used for the chondrogenic, apoptotic and senescent phenotype of chondrocytes. RESULTS: The level of MIF was significantly increased in OA patients. MIF significantly reversed the senescent phenotype induced by LPS pretreatment in human chondrocytes. MIF significantly enhanced the expression of Col II, SOX9, and ACAN in LPS pre-treated human chondrocytes. Furthermore, MIF significantly inhibited the apoptosis of LPS-induced senescent chondrocytes. CONCLUSION: Increased level of MIF in osteoarthritic joint cavity might effectively suppress the senescent phenotype and simultaneously improve the chondrogenic phenotype in chondrocytes, the underlying mechanism was likely to be independent of apoptosis.

The prognostic factors in acute myeloid leukaemia with double-mutated CCAAT/enhancer-binding protein alpha (CEBPAdm).

The prognostic factors to stratify acute myeloid leukaemia (AML) with double-mutated CCAAT/enhancer-binding protein alpha (CEBPAdm) into different risk groups remains to be determined. In this retrospective study, we evaluated 171 consecutive patients with newly diagnosed AML with CEBPAdm by a Cox proportional hazards regression model. In univariate analyses, colony stimulating factor 3 receptor (CSF3R) and Wilms tumour 1 (WT1) mutations were associated with poor relapse-free survival (RFS). The induction regimens including homoharringtonine (omacetaxine mepesuccinate) or intermediate-dose cytarabine was associated with favourable RFS and overall survival (OS). The induction regimen including both homoharringtonine and intermediate-dose cytarabine was associated with the most favourable RFS (3-year RFS 84.7%) and OS (3-year OS 92.8%) compared to the conventional cytarabine and daunorubicin regimen (3-year RFS 27.7%, hazard ratio [HR] 0.126, 95% confidence interval [CI] 0.051-0.313, Wald p < 0.001; and 3-year OS 56.4%, HR 0.179, 95% CI 0.055-0.586, Wald p = 0.005). In multivariate analyses, the induction regimen including intermediate-dose cytarabine (HR 0.364, 95% CI 0.205-0.646, Wald p < 0.001) and CSF3R mutations (HR 2.667, 95% CI 1.276-5.572, Wald p = 0.009) were independently associated with RFS. Taken together, we found that induction regimen and CSF3R mutations were independent prognostic factors for AML with CEBPAdm.

Deoxycholic acid-stimulated macrophage-derived exosomes promote spasmolytic polypeptide-expressing metaplasia in the stomach.

RATIONALE: Spasmolytic polypeptide-expressing metaplasia (SPEM) is an important risk factor for the occurrence of gastric cancer. It may be driven by a chronic inflammatory environment in which macrophage is involved. Studies have shown that intestinal metaplasia may originate from SPEM, and bile acid-induced chronic inflammation plays an important role in the process of intestinal metaplasia. However, whether bile acids are involved in the development of SPEM and the specific mechanism are unclear. Meanwhile, macrophages are known to be involved in inflammation regulation by releasing various factors, including exosomes. In this study, we hypothesized that the exosomes released from macrophages stimulated by deoxycholic acid participated in the development of SPME. METHODS: In vivo, mice were gavaged with deoxycholic acid for 4 weeks, and gastric tissues were harvested. In vitro, deoxycholic acid-induced macrophage-derived exosomes were isolated by ultracentrifugation and cocultured with the gastric organoids of mice. Immunofluorescence staining and quantitative real-time PCR were used to analyze markers of macrophages and SPEM. RESULTS: In vivo, after 4 weeks of deoxycholic acid intragastric administration, macrophage markers (F4/80) and SPEM markers (TFF2 and GSII lectin) were increased in from treated mice compared with those from normal control mice. In vitro, macrophage-derived exosomes labeled with PKH67 were internalized by gastric organoids. Deoxycholic acid-induced macrophage-derived exosomes increased the expression of SPEM markers (TFF2 and GSII lectin) in gastric organoids compared to exosomes derived from macrophages without deoxycholic acid stimulation. CONCLUSION: Macrophage-derived exosomes may be a novel mechanism by which deoxycholic acid promotes SPEM.

Endoscopic acanthosis nigricans appearance: A novel specific marker for diagnosis of low-grade intraepithelial neoplasia.

BACKGROUND AND AIM: At present, there is no recognized diagnostic criteria for gastric low-grade intraepithelial neoplasia (LGIN). The purpose of this study was to determine whether an "endoscopic acanthosis nigricans appearance (EANA)" could be a useful endoscopic marker for distinguishing LGIN lesions from peripheral non-neoplastic tissues. METHODS: A retrospective study was conducted on 638 cases of suspected superficial lesions with endoscopic images from white light endoscopy and magnifying endoscopy combined with narrow band imaging. According to the pathological results of accurate biopsies, those lesions were divided into three groups: a control group, an LGIN group, and an early gastric cancer (EGC) group. RESULTS: According to the presence of EANAs, the sensitivity, specificity, positive predictive value, and negative predictive value for differentiating between the LGIN and control groups were 24.8%, 97.3%, 78.3%, and 76.6%, respectively. The sensitivity (84.1%) and negative predictive value (92.4%) were significantly improved by combining EANA with types IV-VI pit pattern. The intervening part and mean gray value of glands, representing microsurface features and microvascular variation, were significantly larger or higher in EANA lesions than in the surrounding non-neoplastic mucosa. LGIN with EANA was more likely to be present in lesions of type 0-IIa. In addition, the prevalence of EANAs in EGC was 16.7%. CONCLUSION: An EANA could be used as an auxiliary indicator for a diagnosis of LGIN in suspected lesions. It could also play a potential assistive role in the diagnosis of EGC lesions.

Synergistically regulated spontaneous calcium signaling is attributed to cartilaginous extracellular matrix metabolism.

Ca2+ has been recognized as a key molecule for chondrocytes, however, the role and mechanism of spontaneous [Ca 2+ ] i signaling in cartilaginous extracellular matrix (ECM) metabolism regulation are unclear. Here we found that spontaneous Ca 2+ signal of in-situ porcine chondrocytes was [Ca 2+ ] o dependent, and mediated by [Ca 2+ ] i store release. T-type voltage-dependent calcium channel (T-VDCC) mediated [Ca 2+ ] o influx was associated with decreased cell viability and expression levels of ECM deposition genes. Further analysis revealed that chondrocytes expressed both inositol 1,4,5-trisphosphate receptor (InsP3R) and Orai isoforms. Inhibition of endoplasmic reticulum (ER) Ca 2+ release and store-operated calcium entry significantly abolished spontaneous [Ca 2+ ] i signaling of in-situ chondrocytes. Moreover, blocking ER Ca 2+ release with InsP3R inhibitors significantly upregulated ECM degradation enzymes production, and was accompanied by decreased proteoglycan and collagen type II intensity. Taken together, our data provided evidence that spontaneous [Ca 2+ ] i signaling of in-situ porcine chondrocytes was tightly regulated by [Ca 2+ ] o influx, InsP3Rs mediated [Ca 2+ ] i store release, and Orais mediated calcium release-activated calcium channels activation. Both T-VDCC mediated [Ca 2+ ] o influx and InsP3Rs mediated ER Ca 2+ release were found crucial to cartilaginous ECM metabolism through distinct regulatory mechanisms.

Nilotinib combined with multi-agent chemotherapy in newly diagnosed Philadelphia chromosome-positive acute lymphoblastic leukemia: a single-center prospective study with long-term follow-up.

The aim of this study is to investigate the efficacy and safety of nilotinib combined with multi-agent chemotherapy in newly diagnosed Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL). Thirty patients with Ph+ ALL were recruited. Standard induction chemotherapy was given for 4 weeks. Nilotinib was administered beginning on day 15 of induction. After achieving hematologic complete remission (HCR), patients received either seven courses of consolidation or hematopoietic cell transplantation (HCT). Nilotinib was continued 2 years after achieving HCR or before stem cell transplantation conditioning. HCR and molecular complete response (MCR), overall survival (OS), hematologic relapse-free survival (HRFS), molecular relapse-free survival (MRFS), toxicity, and nilotinib levels in the serum and cerebrospinal fluid were evaluated. All patients achieved HCR, and cumulative MCR rate was 83.3%. The median HRFS and OS were 18 and 47.5 months, respectively. Four-year HRFS and OS rates were 54% and 45%, respectively. The median MRFS and 4-year MRFS for the patients with MCR were 19 months and 45%, respectively. The molecular response of patients after induction cycle had no impact on HRFS, MRFS, or OS. The patients who achieved MCR after 3 and 6 months had superior HRFS. The HCT cohort in the first HCR had significantly lower rates of relapse and longer MRFS, HRFS, and OS. Most adverse events were reversible with dose reduction or transient interruption of nilotinib therapy. Only traces of nilotinib were detected in cerebrospinal fluid. Nilotinib combined with cytotoxic chemotherapy was effective and translated to a high HCR and MCR for patients with Ph+ ALL. It should be noted that nilotinib cannot cross the blood-brain barrier.

Flow cytometric analysis of cerebrospinal fluid in adult patients with acute lymphoblastic leukemia during follow-up.

OBJECTIVE: To explore the value of flow cytometric (FCM) analysis of cerebrospinal fluid (CSF) in the diagnosis of central nervous system involvement in adult patients with acute lymphoblastic leukemia (ALL) during follow-up. METHODS: A total of 2871 CSF samples from 357 adult patients with newly diagnosed ALL between the year of 2009 and 2015 were analyzed retrospectively. These patients were divided into 3 groups according to CSF results, FCM+/conventional cytology (CC)+ group, FCM+/CC- group, and FCM-/CC- group, respectively. The overall survival (OS) of the three groups was analyzed. RESULTS: Fifteen (4.2%) and 26 (7.3%) patients' CSF samples were FCM+/CC+ and FCM+/CC-, respectively. The remaining 316 (88.5%) patients' samples were FCM-/CC-. The 2-year OS for the FCM+/CC+, FCM+/CC-, and FCM-/CC- groups was 40.0%, 20.6%, and 64.2%, respectively (P < .001). There was no statistically significant difference in OS between FCM+/CC+ and FCM+/CC- patients (P = .195). In multivariate analysis, a high WBC count and LDH level were independent risk factors for central nervous system involvement in adult patients with ALL. CONCLUSIONS: FCM demonstrated a superior sensitivity over conventional cytology in the diagnosis of central nervous system involvement in adult patients with ALL. FCM+/CC- patients showed a similar survival with FCM+/CC+ patients, suggesting that an isolated FCM-positive status holds clinical significance.

An analysis of 97 previously diagnosed de novo adult acute erythroid leukemia patients following the 2016 revision to World Health Organization classification.

BACKGROUND: The incidence of acute erythroid leukemia subtype (AEL) is rare, accounting for 5% of cases of acute myeloid leukemia (AML), and the outcome is dismal. However, in 2016 revision to the WHO classification, the subcategory of AEL has been removed. Myeloblasts are redefined as the percentage of total marrow cells, not non-erythroid cells. Therefore, the previously diagnosed AEL cases are currently diagnosed as AML or myelodyspalstic syndrome (MDS) according to new criteria. METHODS: We respectively reviewed cases of 97 de novo previously diagnosed AEL and all the patients were diagnosed as AML or MDS according to the new classification scheme, and then the clinical characteristics of these two subtypes were compared. Statistical analyses were performed by SPSS software version 18.0. RESULTS: The median age was 37 years-old, the two-thirds of previous AEL cases were diagnosed as MDS, and there was no obvious difference between two subtypes except for male/female ratio and age. Cytogenetic, rather than MDS/AML subtypes, can better represent the prognostic factor of previously diagnosed AEL patients. When the cytogenetic risk of patients belonged to MRC intermediate category and age were below 40 years-old in previous AEL cases, the patients who received induction chemotherapy without transplantation had a similar survival compared with the patients who underwent transplantation (3-year OS: 67.2% vs 68.5%). CONCLUSIONS: Cytogenetic, rather than MDS/AML subtypes, can better represent the prognostic factor of previously diagnosed AEL patients. Transplantation was a better choice for those whose cytogenetic category was unfavorable.

The Lineage Specification of Mesenchymal Stem Cells Is Directed by the Rate of Fluid Shear Stress.

The effective regulation of fluid shear stress (FSS) on the lineage specification of mesenchymal stem cells (MSCs) remains to be addressed. We hypothesized that when MSCs are recruited to musculoskeletal system following stimulation, their differentiation into osteogenic or chondrogenic cells is directed by the rate of FSS (ΔSS) through modulation of the mechanosensitive, cation-selective channels (MSCCs), intracellular calcium levels, and F-actin. To this end, MSCs were exposed to laminar FSS linearly increased from 0 to 10 dyn/cm(2) in 0, 2, or 20 min and maintained at 10 dyn/cm(2) for a total of 20 min (termed as ΔSS 0-0', 0-2', and 0-20', respectively, representing more physiological (0-0') and non-physiological (0-2' and 0-20') ΔSS treatments). Our results showed 0-0' facilitated MSC differentiation towards chondrogenic and not osteogenic phenotype, by promoting moderate intracellular calcium concentration ([Ca(2+) ]i ) increase from the calcium channels with the exception of MSCCs or intracellular calcium stores, and F-actin organization. In contrast, 0-2' promoted MSCs towards osteogenic and not chondrogenic phenotype, by inducing significant [Ca(2+) ]i increase mainly from the MSCCs, and F-actin assembly. However, 0-20' elicited the modest osteogenic and chondrogenic phenotypes, as it induced the lowest [Ca(2+) ]i increase mainly from MSCCs, and F-actin assembly. Our results suggest that compared to the more physiological ΔSS, the non-physiological ΔSS favors [Ca(2+) ]i influx from MSCCs. An appropriate non-physiological ΔSS (0-2') even elicits a large [Ca(2+) ]i influx from the MSCCs that reverses the lineage specification of MSCs, providing validation for the high mechanosensitivity of MSCs and guidance for training osteoporosis and osteoarthritis patients. J. Cell. Physiol. 231: 1752-1760, 2016. © 2015 Wiley Periodicals, Inc.

Effects of vimentin disruption on the mechanoresponses of articular chondrocyte.

Human articular cartilage is subjected to repetitive mechanical loading during life time. As the only cellular component of articular cartilage, chondrocytes play a key role in the mechanotransduction within this tissue. The mechanoresponses of chondrocytes are largely determined by the cytoskeleton. Vimentin intermediate filaments, one of the major cytoskeletal components, have been shown to regulate chondrocyte phenotype. However, the contribution of vimentin in chondrocyte mechanoresponses remains less studied. In this study, we seeded goat articular chondrocytes on a soft polyacrylamide gel, and disrupted the vimentin cytoskeleton using acrylamide. Then we applied a transient stretch or compression to the cells, and measured the changes of cellular stiffness and traction forces using Optical Magnetic Twisting Cytometry and Traction Force Microscopy, respectively. In addition, to study the effects of vimentin disruption on the intracellular force generation, we treated the cells with a variety of reagents that are known to increase or decrease cytoskeletal tension. We found that, after a compression, the contractile moment and cellular stiffness were not affected in untreated chondrocytes, but were decreased in vimentin-disrupted chondrocytes; after a stretch, vimentin-disrupted chondrocytes showed a lower level of fluidization-resolidification response compared to untreated cells. Moreover, vimentin-disrupted chondrocytes didn't show much difference to control cells in responding to reagents that target actin and ROCK pathway, but showed a weaker response to histamine and isoproterenol. These findings confirmed chondrocyte vimentin as a major contributor in withstanding compressive loading, and its minor role in regulating cytoskeletal tension.

Effect of L-arginine and sildenafil citrate on intrauterine growth restriction fetuses: a meta-analysis.

BACKGROUND: Intrauterine growth restriction (IUGR) is associated with perinatal morbidity and mortality. Several clinical trials have reported L-arginine and sildenafil citrate had effect on intrauterine growth restriction fetuses. A meta-analysis of available randomized controlled trials (RCTs) was conducted to investigate the effects of L-arginine and sildenafil citrate on major clinical outcomes of IUGR fetuses. METHODS: Systematically searched Medline, Embase, the Cochrane Library, and Clinical Trials, references of retrieved articles, and conference proceedings from 1960 to 2015. We included randomized controlled trials assessing the effects of L-arginine and sildenafil citrate on IUGR. Outcomes analyzed were the birth weight, gestational age at labor, Apgar score at 1and 5 min, the ratio of NRDS, the ratio of ICH and neonatal death, etc. RESULTS: Ten trials were included. Nine trials (576 patients) compared L-arginine with either placebo or no intervention. In the L-arginine treatment groups of the L-arginine trials, there was a significant increase in fetal birth weight (SMD 0.41, 95 % CI [0.24,0.58]), gestational age (SMD 0.30, 95 % CI [0.07,0.54]); L-arginine treatment group have a significant reduction in the ratio of neonatal respiratory distress syndrome (P = 0.009), intracranial hemorrhage of fetuses (P = 0.002), but the number of included studies and people on these outcomes are small. As only one trial (41 patients) compared sildenafil citrate with placebo, it was too small for reliable conclusions about possible differential effects could be drawn. CONCLUSIONS: The results of this meta-analysis showed that L-arginine increased birth weight and prolonged gestational age at labor of IUGR fetuses. However, further large-scale RCTs are needed to adequately assess the effect of L-arginine and Sildenafil citrate on clinical outcomes, because the number of study may be small.

Engineering zonal cartilage through bioprinting collagen type II hydrogel constructs with biomimetic chondrocyte density gradient.

BACKGROUND: Cartilage tissue engineering is a promising approach for repairing and regenerating cartilage tissue. To date, attempts have been made to construct zonal cartilage that mimics the cartilaginous matrix in different zones. However, little attention has been paid to the chondrocyte density gradient within the articular cartilage. We hypothesized that the chondrocyte density gradient plays an important role in forming the zonal distribution of extracellular matrix (ECM). METHODS: In this study, collagen type II hydrogel/chondrocyte constructs were fabricated using a bioprinter. Three groups were created according to the total cell seeding density in collagen type II pre-gel: Group A, 2 × 10(7) cells/mL; Group B, 1 × 10(7) cells/mL; and Group C, 0.5 × 10(7) cells/mL. Each group included two types of construct: one with a biomimetic chondrocyte density gradient and the other with a single cell density. The constructs were cultured in vitro and harvested at 0, 1, 2, and 3 weeks for cell viability testing, reverse-transcription quantitative PCR (RT-qPCR), biochemical assays, and histological analysis. RESULTS: We found that total ECM production was positively correlated with the total cell density in the early culture stage, that the cell density gradient distribution resulted in a gradient distribution of ECM, and that the chondrocytes' biosynthetic ability was affected by both the total cell density and the cell distribution pattern. CONCLUSIONS: Our results suggested that zonal engineered cartilage could be fabricated by bioprinting collagen type II hydrogel constructs with a biomimetic cell density gradient. Both the total cell density and the cell distribution pattern should be optimized to achieve synergistic biological effects.

[A clinical study of acute lymphoblastic leukemia in adolescents: a single center experience].

OBJECTIVE: To explore the clinical and laboratory characteristics, treatment, prognostic factors of acute lymphoblastic leukemia (ALL) in adolescents. METHODS: Adolescents de novo ALL patients in Blood Disease Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences from September 1999 to September 2013 were enrolled in this study. Clinical data, therapeutic effect and prognostic factors were retrospectively analyzed. RESULTS: Of all 94 patients, 91 patients were treated in our center. The overall complete remission (CR) rate was 96.7% (88/91), CR rate after one cycle was 91.2%(83/91). The median follow-up time was 18 months. In all patients, the 6-year anticipated overall survival (OS) rate and disease free survival (DFS) rate were (47.6 ± 6.7)% and (45.4 ± 6.0)% respectively. In standard risk ALL patients , 6-year anticipated OS rate and DFS rate were (65.7 ± 8.1)% and (65.3 ± 7.4)%. Hyperleukocytosis (white blood cell count ≥30 × 10(9)/L in B-ALL; ≥100 × 10(9)/L in T-ALL), Ph(+) , MLL(+) , hypodiploid were risk factors associated with poor clinical outcome. CONCLUSIONS: The therapeutic effect and clinical outcome in adolescents with ALL are relatively favorable, especially in standard risk group. In high risk ALL patients, allogeneic hematopoietic stem cell transplantation may improve therapeutic efficacy.

Inserted rest period resensitizes MC3T3-E1 cells to fluid shear stress in a time-dependent manner via F-actin-regulated mechanosensitive channel(s).

The underlying cellular mechanism of anabolic effect recovered by inserting rest is not fully understood. In this work, we studied the role of F-actin regulated mechanosensitive channel(s) re-activation in mechanosensitivity modulation in vitro. Results showed that steady fluid shear stress (sFSS) stimulation with 30-min rest period was more potential in increasing alkalinephosphatase (ALP) activity than 10 and 0-min rest periods, and insertion of 30 min, but not 0 or 10 min, recovered the [Ca(2+)]i transient and contribution of the mechanosensitive channel(s). During the rest period, F-actin experienced polymerization (0-10 min), followed by depolymerization (10-30 min); inhibition of F-actin polymerization/depolymerization significantly increased/decreased the [Ca(2+)]i transient, as well as the contribution of the mechanosensitive channel(s) in subsequent sFSS stimulation. Our results demonstrated that the long rest period between sFSS loadings recruited [Ca(2+)]i transient via F-actin depolymerization-induced reactivation of mechanosensitive channel(s), suggesting that F-actin-regulated cellular stiffness could account for the decreased anabolic response during continuous mechanical loading in bone cells.

Prostaglandin E2 modulates F-actin stress fiber in FSS-stimulated MC3T3-E1 cells in a PKA-dependent manner.

The effect of prostaglandin E2 (PGE2) on bone mass has been well-established in vivo. Previous studies have showed that PGE2 increases differentiation, proliferation, and regulates cell morphology through F-actin stress fiber in statically cultured osteoblasts. However, the effect of PGE2 on osteoblasts in the presence of fluid shear stress (FSS), which could better uncover the anabolic effect of PGE2 in vivo, has yet to be examined. Here, we hypothesized that PGE2 modulates F-actin stress fiber in FSS-stimulated MC3T3-E1 osteoblastic cells through protein kinase A (PKA) pathway. Furthermore, this PGE2-induced F-actin remodeling was associated with the recovery of cellular mechanosensitivity. Our data showed that treatment with 10 nM dmPGE2 for 15 min significantly suppressed the F-actin stress fiber intensity in FSS-stimulated cells in a PKA-dependent manner. In addition, dmPGE2 treatment enhanced the cells' calcium peak magnitude and the percentage of responding cells in the second FSS stimulation, though these effects were abolished and attenuated by co-treatment with phalloidin. Our results demonstrated that 10 nM dmPGE2 was able to accelerate the 'reset' process of F-actin stress fiber to its pre-stimulated level partially through PKA pathway, and thus promoted the recovery of cellular mechanosensitivity. Our finding provided a novel cellular mechanism by which PGE2 increased bone formation as shown in vivo, suggesting that PGE2 could be a potential target for treatments of bone formation-related diseases.