Thiazolidinediones (TZDs) enhance insulin secretory response via GPR40 and adenylate cyclase (AC).

Thiazolidinediones are synthetic PPARγ ligands that enhance insulin sensitivity, and that could increase insulin secretion from ß-cells. However, the functional role and mechanism(s) of action in pancreatic ß-cells have not been investigated in detail.

Micro-RNAs in the aqueous humour of patients with diabetic macular oedema.

IMPORTANCE: Micro-RNAs (miRNAs) have been studied as new biomarkers or mediators in various diseases, but the value of aqueous humour (AH) miRNAs in diabetic macular oedema (DMO) is still not known. BACKGROUND: To compare AH miRNAs and related cytokine expression in DMO patients and healthy controls. DESIGN: Prospective cross-sectional study. PARTICIPANTS: Twenty naïve DMO patients and 13 control subjects, who were scheduled for intravitreal injection and cataract surgery, respectively. METHODS: AH samples were collected at the beginning of each procedure and analysed using a miRNA polymerase chain reaction (PCR) array composed of 84 miRNAs, reverse transcripase-quantitative PCR (qPCR) for verifying selected differentially expressed miRNAs, and a cytokine assay, the results of which were compared with bioinformatics conducted to find out genes associated with DMO-related miRNAs. MAIN OUTCOMES MEASURES: AH expression of miRNAs and cytokines and the bioinformatics results. RESULTS: Five miRNAs (hsa-miR-185-5p, hsa-miR-17-5p, hsa-miR-20a-5p, hsa-miR-15b-5p and hsa-miR-15a-5p) showing a fold change greater than -50 in log2 values in the miRNA PCR array were selected, all significantly down-regulated in the DMO group compared to the control group (P < .05), and showed a direct relationship with tumour necrosis factor, nuclear factor kappa B subunit 1 and interleukin-6 (IL-6) in bioinformatics analysis, all of which were related to vascular endothelial growth factor (VEGF). In the cytokine assay, the aqueous concentrations of VEGF, placental growth factor, IL-6 and IL-8 were significantly higher in the DMO group compared to the control group. CONCLUSIONS AND RELEVANCE: This study is the first to perform miRNA profiling of the AH of DMO patients. We identified differentially expressed miRNAs in DMO AH, which may be used as potential biomarkers or novel therapeutic targets for DMO.

Effects of aspirin and clopidogrel on neural stem cells.

Cerebral infarction causes severe morbidity and mortality. Most patients with cerebral infarction should take antiplatelet drugs daily, so the effects of those drugs on the regeneration of the brain need to be investigated. Aspirin and clopidogrel are the most widely used antiplatelet drugs for the prevention of ischemic stroke. We investigated the effects of aspirin and clopidogrel on neural stem cells (NSCs). NSCs were dissociated from fetal rat cortex and cultured with basic fibroblast growth factor and N2 medium. To measure the effects of aspirin and clopidogrel on NSCs, NSCs were treated with several concentrations of aspirin, clopidogrel bisulfate, and clopidogrel resinate for 24 h. After the treatment, we measured cell viability by cell counting kit-8, MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay, trypan blue staining, flow cytometry, and lactate dehydrogenase assay. To evaluate their effects on NSC proliferation, we performed BrdU cell proliferation assay and colony-forming unit assay. We compared the intracellular protein level in the NSCs treated with aspirin and two types of clopidogrel, by proteomics analysis. Various viability tests showed that clopidogrel resinate and clopidogrel bisulfate did not affect the viability and proliferation of NSCs whereas aspirin decreased them even at low concentrations which are clinically relevant. Moreover, through the proteomics, it was confirmed that the toxicity of aspirin to NSCs might be associated with the alteration of several intracellular proteins. Taken together, these results suggest that clopidogrel resinate and clopidogrel bisulfate are safe but aspirin could be toxic to NSCs. Therefore, when these antiplatelet agents are prescribed over the long-term, the finding that aspirin could be toxic to NSCs should be considered.

An Integrative Review of the Feasibility and Effects of the Use of Location-Tracking Devices by Persons Living With Cognitive Impairment.

OBJECTIVES: This study aimed to examine the effects of location-tracking devices on persons living with cognitive impairment, investigate facilitators of and barriers to using the devices, and provide future directions for the use of the devices. METHODS: An integrative review was conducted using 5 databases: PubMed, Embase, Web of Science, CINAHL, and Scopus. From the 1429 initially identified studies, 10 were included in the review. RESULTS: Location-tracking devices benefited persons living with cognitive impairment and their informal caregivers. The devices brought more independence to persons living with cognitive impairment, allowing them to go outside and feel safer there. Furthermore, the devices reduced the caregivers' worries about their loved ones being lost. CONCLUSIONS: Location-tracking devices have the potential to increase independence in persons living with cognitive impairment and to decrease psychological stress in informal caregivers. In the future, ways to minimize the barriers to using location-tracking devices need to be determined.

Association between osteoporosis and the rate of telomere shortening.

A shorter leukocyte telomere length (LTL) is reported to be associated with age-related diseases, including osteoporosis. Many studies have tried identifying the association between LTL and osteoporosis, although it remains controversial. This study aimed to determine whether osteoporosis is independently associated with LTL shortening in a prospective longitudinal cohort. The KBASE study is an independent multicenter prospective cohort in South Korea, which began in 2014. We compared the LTL values for each participant at baseline and over a 2-year follow-up period. Boxplots were used to demonstrate the differences in the change in LTL over a 2-year follow-up according to osteoporosis. Multivariable linear regression was conducted to identify whether osteoporosis is independently associated with the rate of telomere shortening. A total of 233 subjects (from 55 to 88 years) from the KBASE cohort were finally enrolled in the study. We observed that the LTL decreased by approximately 1.2 kbp over 2 years. While the LTL decreased as age increased, the rate of LTL shortening did not increase with age. Multivariable linear regression analysis indicated that only osteoporosis was independently associated with rapid LTL shortening over 2 years (B, -8.08; p = 0.038). We sought to identify an association between osteoporosis and LTL shortening in an independent prospective cohort. We found that participants with osteoporosis had significantly faster LTL shortening over 2 years than those without osteoporosis. We hope this study will help elucidate the underlying mechanisms in the relationship between LTL and osteoporosis in the future.

Characteristics of Femoral Shaft Fractures That Predict Ipsilateral Femoral Neck Fractures.

INTRODUCTION: This study aims to characterize radiographic features and fracture characteristics in femoral shaft fractures with associated femoral neck fractures, with the goal of establishing predictive indicators for the presence of ipsilateral femoral neck fractures (IFNFs). METHODS: A retrospective cohort was collected from the electronic medical record of three level I trauma centers over a 5-year period (2017 to 2022) by current procedural terminology (CPT) codes. Current CPT codes for combined femoral shaft and IFNFs were identified to generate our study group. CPT codes for isolated femur fractures were identified to generate a control group. RESULTS: One hundred forty patients comprised our IFNF cohort, and 280 comprised the control cohort. On univariate, there were significant differences in mechanism of injury (P < 0.001), Orthopedic Trauma Association (OTA)/Arbeitsgemeinshaft fur Osteosynthesefragen (AO) classification (P = 0.002), and fracture location (P < 0.001) between cohorts. On multivariate, motor vehicle crashes were more commonly associated with IFNFs compared with other mechanism of injuries. OTA/AO 32A fractures were more commonly associated with IFNFs when compared with OTA/AO 32B fractures (adjusted odds ratio = 0.36, P < 0.001). Fractures through the isthmus were significantly more commonly associated with IFNFs than fractures more proximal (adjusted odds ratio = 2.52, P = 0.011). DISCUSSION: Detecting IFNFs in femoral shaft fractures is challenging. Motor vehicle crashes and motorcycle collisions, OTA/AO type 32A fractures, and isthmus fractures are predictive of IFNFs.

Reporting Bias is Highly Prevalent in Systematic Reviews and Meta-Analyses of Platelet Rich Plasma Injections for Hip Osteoarthritis.

Purpose: To describe the incidence and types of spin in systematic reviews of platelet-rich plasma (PRP) injections for hip osteoarthritis (OA) and to determine whether patterns in study characteristics could be identified among studies with identifiable spin. Methods: The PubMed, Scopus, and SPORTDiscus databases were queried. Inclusion criteria were systematic reviews or meta-analyses that included an assessment of intra-articular PRP injections as a stand-alone treatment for hip OA. Two authors independently assessed the presence of spin in the included studies and recorded general study characteristics. The prevalence of the 15 different categories of spin was quantified using descriptive statistics. Results: Fifteen studies met inclusion criteria for this study. All studies contained at least two types of spin (range 2-9), with a median of 2. The most common type of spin was type 14 ("Failure to report a wide confidence interval of estimates"), which was observed in 10 studies. The second most common type of spin was type 13 ("Failure to specify the direction of the effect when it favors the control intervention"), found in 6 studies. Conclusions: Spin is highly prevalent in abstracts of systematic reviews of PRP in the treatment of hip OA. Several associations were found between spin types and the study characteristics of AMSTAR 2 rating, Scopus CiteScore, journal impact factor, and PROSPERO preregistration. When present, spin in the abstracts of reviewed studies tended to favor the use of PRP in hip osteoarthritis. Clinical Relevance: It is important to understand the prevalence of spin in published abstracts, especially in areas of great impact or interest, so authors and readers can have a greater awareness of this potential form of bias.

Immune Regulatory Function of Cancer- Associated Fibroblasts in Non-small Cell Lung Cancer.

BACKGROUND: Cancer-associated fibroblasts (CAFs) are key components of the tumor microenvironment and significantly contribute to immune evasion. We investigated the effects of CAFs on the immune function of CD4+ and CD8+ T cells in non-small cell lung cancer (NSCLC). METHODS: We isolated CAFs and normal fibroblasts (NFs) from tumors and normal lung tissues of NSCLC patients, respectively. CAFs were co-cultured with activated T cells to evaluate their immune regulatory function. We investigated the effect of CAF conditioned medium (CAF-CM) on the cytotoxicity of T cells. CAFs were also co-cultured with activated peripheral blood mononuclear cells and further incubated with cyclooxygenase- 2 (COX2) inhibitors to investigate the potential role of COX2 in immune evasion. RESULTS: CAFs and NFs were isolated from the lung tissues (n=8) and lymph nodes (n=3) of NSCLC patients. Immune suppressive markers, such as COX2 and programmed death-ligand 1 (PD-L1), were increased in CAFs after co-culture with activated T cells. Interestingly, CAFs promoted the expression of programmed death-1 in CD4+ and CD8+ T cells, and strongly inhibited T cell proliferation in allogenic and autologous pairs of CAFs and T cells. CAF-CM decreased the cytotoxicity of T cells. COX2 inhibitors partially restored the proliferation of CD4+ and CD8+ T cells, and downregulated the expression of COX2, prostaglandin E synthase, prostaglandin E2, and PD-L1 in CAFs. CONCLUSION: CAFs promote immune evasion by suppressing the function of CD4+ and CD8+ T cells via their effects on COX2 and PD-L1 in NSCLC. The immunosuppressive function of CAFs could be alleviated by COX2 inhibitors.

Inhibition of the NLRP3 Inflammasome Activation/Assembly through the Activation of the PI3K Pathway by Naloxone Protects Neural Stem Cells from Ischemic Condition.

Naloxone is a well-known opioid antagonist and has been suggested to have neuroprotective effects in cerebral ischemia. We investigated whether naloxone exhibits anti-inflammatory and neuroprotective effects in neural stem cells (NSCs) injured by oxygen-glucose deprivation (OGD), whether it affects the NOD-like receptor protein 3 (NLRP3) inflammasome activation/assembly, and whether the role of the phosphatidylinositol 3-kinase (PI3K) pathway is important in the control of NLRP3 inflammasome activation/assembly by naloxone. Primary cultured NSCs were subjected to OGD and treated with different concentrations of naloxone. Cell viability, proliferation, and the intracellular signaling proteins associated with the PI3K pathway and NLRP3 inflammasome activation/assembly were evaluated in OGD-injured NSCs. OGD significantly reduced survival, proliferation, and migration and increased apoptosis of NSCs. However, treatment with naloxone significantly restored survival, proliferation, and migration and decreased apoptosis of NSCs. Moreover, OGD markedly increased NLRP3 inflammasome activation/assembly and cleaved caspase-1 and interleukin-1ß levels in NSCs, but naloxone significantly attenuated these effects. These neuroprotective and anti-inflammatory effects of naloxone were eliminated when cells were treated with PI3K inhibitors. Our results suggest that NLRP3 inflammasome is a potential therapeutic target and that naloxone reduces ischemic injury in NSCs by inhibiting NLRP3 inflammasome activation/assembly mediated by the activation of the PI3K signaling pathway.

Differential expression of aqueous humor microRNAs in central retinal vein occlusion and its association with matrix metalloproteinases: a pilot study.

The aim of this study is to investigate the differential expression of microRNAs (miRNAs) in the aqueous humor (AH) of patients with central retinal vein occlusion (CRVO), and their association with AH matrix metalloproteinase (MMP) activity. Eighteen subjects, including 10 treatment naïve patients with CRVO and 8 control subjects, scheduled for intravitreal injection and cataract surgery, respectively, were included. AH samples were collected at the beginning of the procedure. A microarray composed of 84 miRNAs was performed to identify differentially expressed miRNAs in CRVO AH, which were further analyzed using bioinformatic tools to identify directly related cytokines/proteins. Eight miRNAs (hsa-mir-16-5p, hsa-mir-142-3p, hsa-mir-19a-3p, hsa-mir-144-3p, hsa-mir-195-5p, hsa-mir-17-5p, hsa-mir-93-5p, and hsa-mir-20a-5p) were significantly downregulated in the CRVO group. Bioinformatic analysis revealed a direct relationship among downregulated miRNAs, CRVO, and the following proteins: MMP-2, MMP-9, tumor necrosis factor, transforming growth factor beta-1, caspase-3, interleukin-6, interferon gamma, and interleukin-1-beta. Activities of MMP-2 and -9 in AH were detected using gelatin zymography, showing significant increase in the CRVO group compared to the control group (p < 0.01). This pilot study first revealed that MMP-2 and -9 were directly related to downregulated miRNAs and showed significant increase in activity in AH of patients with CRVO. Therefore, the relevant miRNAs and MMPs in AH could serve as potential biomarkers or therapeutic targets for CRVO.

Glia-Like Cells from Human Mesenchymal Stem Cells Protect Neural Stem Cells in an In Vitro Model of Alzheimer's Disease by Reducing NLRP-3 Inflammasome.

BACKGROUND AND PURPOSE: Neural stem cells (NSCs) have the ability to regenerate, proliferate, and differentiate, enabling them to play important roles in the recovery of the damaged nervous system. However, in neurodegenerative diseases such as Alzheimer's disease (AD), the NSCs are damaged as well. Glia-like cells from human mesenchymal stem cells (ghMSCs) are functionally enhanced adult stem cells. In the present study, we investigated whether ghMSCs could protect NSCs from amyloid beta (Aß)-mediated toxicity. METHODS: Rat NSCs were obtained from E13-14 fetal rat cortices. NSCs were seeded in pre-coated plates, and the next day, cells were simultaneously treated with 20 µM Aß and 0.4 µm pore insert well-seeded ghMSCs. After 48 hours of co-treatment, cell viability and proliferation were evaluated. After 2 hours of co-treatment, western blotting was performed to measure inflammasome-related factors, such as NOD-like receptor family pyrin domain containing 3, caspase-1, and interleukin-1ß. RESULTS: The results showed that ghMSCs increased viability and proliferation and reduced the toxicity of NSCs injured by Aß by reducing the NRLP3 inflammasome activation of NSCs induced by Aß. CONCLUSIONS: In this study, we confirmed that ghMSCs could protect NSCs in an in vitro model of AD through the regulation of inflammatory response.

Case study: analysis of end-user requests on electronic medical record and computerized physician order entry system of Seoul National University Hospital in Korea.

Seoul National University Hospital (SNUH) in Korea has utilized the full Electronic Medical Record (EMR) system since October 2004. Unlike other countries, most EMR systems in Korean teaching and general hospitals are in-house development systems. Therefore, we can actively respond to user requests on EMR. Here, based on 5 years of experience in EMR system operation, we analyzed 2,339 SNUH EMR user requests from 2006 to 2008 for improvement of EMR system operation and management. We classify user requests into 9 criteria based on guidelines from the SNUH medical information management team. In conclusion, the most common requests (73%) are for improvement of improving quality of care. However, requests associated with hospital enterprise, public policy, and customer service are gradually increased every year. Therefore, we suggest that suitable EMR management criteria are necessary for reliable EMR operation and management.

Atorvastatin Rejuvenates Neural Stem Cells Injured by Oxygen-Glucose Deprivation and Induces Neuronal Differentiation Through Activating the PI3K/Akt and ERK Pathways.

Oxygen and glucose (OGD) deprivation is one of the most important pathogenic mechanisms in cerebral infarction and is widely used as an in vitro model for ischemic stroke. OGD also damages neural stem cells (NSCs), which are important in brain recovery after cerebral infarction. To enhance recovery, there have been many studies aimed at determining methods to protect NSCs after stroke. Because atorvastatin has diverse protective effects on neural cells, we studied whether it could rejuvenate NSCs injured by OGD. Primary cultured NSCs were exposed to OGD for 8 h, and the main characteristics of stem cells, such as survival, proliferation, migration, and differentiation, were evaluated to confirm the effect of OGD on NSCs. Next, cells were treated with various concentrations of atorvastatin with exposure to OGD for 8 h to confirm whether it could rejuvenate NSCs. OGD significantly affected the survival, proliferation, migration, and differentiation of NSCs. However, treatment with atorvastatin meaningfully restored survival, proliferation, migration, and differentiation of NSCs. These beneficial effects of atorvastatin were blocked by treatment with either a PI3K inhibitor or an ERK inhibitor. In conclusion, OGD damages NSCs and causes them to lose the main characteristics of stem cells so that they cannot contribute to brain recovery after cerebral infarction. However, treatment with atorvastatin after cerebral infarction can effectively rejuvenate NSCs through activating the PI3K and ERK pathways to aid in brain regeneration.

LGR5 and Downstream Intracellular Signaling Proteins Play Critical Roles in the Cell Proliferation of Neuroblastoma, Meningioma and Pituitary Adenoma.

Leucine-rich repeat-containing G-protein coupled receptor 5 (LGR5) has been reported to play critical roles in the proliferation of various cancer cells. However, the roles of LGR5 in brain tumors and the specific intracellular signaling proteins directly associated with it remain unknown. Expression of LGR5 was first measured in normal brain tissue, meningioma, and pituitary adenoma of humans. To identify the downstream signaling pathways of LGR5, siRNA-mediated knockdown of LGR5 was performed in SH-SY5Y neuroblastoma cells followed by proteomics analysis with 2-dimensional polyacrylamide gel electrophoresis (2D-PAGE). In addition, the expression of LGR5-associated proteins was evaluated in LGR5-inhibited neuroblastoma cells and in human normal brain, meningioma, and pituitary adenoma tissue. Proteomics analysis showed 12 protein spots were significantly different in expression level (more than two-fold change) and subsequently identified by peptide mass fingerprinting. A protein association network was constructed from the 12 identified proteins altered by LGR5 knockdown. Direct and indirect interactions were identified among the 12 proteins. HSP 90-beta was one of the proteins whose expression was altered by LGR5 knockdown. Likewise, we observed decreased expression of proteins in the hnRNP subfamily following LGR5 knockdown. In addition, we have for the first time identified significantly higher hnRNP family expression in meningioma and pituitary adenoma compared to normal brain tissue. Taken together, LGR5 and its downstream signaling play critical roles in neuroblastoma and brain tumors such as meningioma and pituitary adenoma.

Leucine-rich G Protein-coupled Receptor-5 Is Significantly Increased in the Aqueous Humor of Human Eye with Proliferative Diabetic Retinopathy.

Leucine-rich G protein-coupled receptor-5 (LGR5) is known to be a stem cell marker in many organs. LGR5 may have important roles in proliferative diabetic retinopathy (PDR) because LGR5 potentiate the Wnt/ß-catenin pathway, which plays crucial roles in pathologic neovascularization in the retina. The association between LGR5 and retinal pathologic neovascularization has not yet been reported. In the present study, LGR5 was compared in human aqueous humor (AH) between normal control and patients with PDR to confirm the relationship between LGR5 and PDR. AH was collected from 7 naïve PDR patients and 3 control subjects before intravitreal injection and cataract surgery, respectively. LGR5 and key members of Wnt/ß-catenin were assessed by western blotting. In the present study, it was confirmed for the first time that LGR5 is detected in AH and it increases in PDR patients. Key members of Wnt/ß-catenin pathway were also increased in AH of PDR patients compared to control. These findings might support the hypothesis that LGR5 has important roles in PDR especially considering the roles of the Wnt/ß-catenin pathway, which is activated by LGR5, contributing to retinal pathologic neovascularization.

Reduction of mycoplasmal lesions and clinical signs by vaccination against Mycoplasma hyorhinis.

Porcine mycoplasmal pneumonia is a significant disease problem in the swine industry. The causative agents include Mycoplasma hyopneumoniae and Mycoplasma hyorhinis. M. hyopneumoniae is the major pathogen contributing to the porcine respiratory disease complex, but is difficult to isolate from the respiratory tract and tonsils, whereas M. hyorhinis is not. Although M. hyorhinis is commonly detected in the lungs, the role of M. hyorhinis as a cause of pneumonia remains unclear. Current vaccines for porcine mycoplasmal pneumonia only include M. hyopneumoniae, not M. hyorhinis. M. hyopneumoniae vaccines are widely used, but disease still occurs because of poor vaccine efficacy and possibly the presence of M. hyorhinis. In this study, an inactivated vaccine containing a mixture of M. hyorhinis and M. hyopneumoniae was generated and evaluated for safety, immunogenicity, and protective efficacy against challenge with M. hyorhinis in pigs. The inactivated vaccine induced an antibody response and reduced pneumonic lesions in the lungs and tracheas compared with the non-vaccinated group.

PMA activates Stat3 in the Jak/Stat pathway and induces SOCS5 in rat brain astrocytes.

Suppressors of cytokine signaling (SOCS) family members are negative feedback regulators of the Jak/Stat pathway, which is an essential inflammatory signaling pathway. We investigated expression of eight members of the SOCS family in rat astrocytes, using two inflammatory stimulants, PMA and IFN-gamma. Only a few SOCS genes were induced by both stimulants, and we detected an increase in SOCS5 protein with PMA. PMA activated the Jnk, Erk, p38, and Jak/Stat signal pathways. In addition, it increased the level of activated-Stat3 resulting from tyrosine phosphorylation. A gel-shift assay showed that a protein in nuclear extracts from PMA-treated cells was able to bind to Stat binding elements. These results suggest that activated Stat3 binds to SOCS promoters and leads to their transcriptional induction.

Establishing a Population-Based HLA-Antibody Panel for Flow Cytometric Monitoring of Chimerism in HLA-Haploidentical Stem Cell Transplantation.

Determining the chimerism in stem cell transplantation (SCT) is important in the monitoring of engraftment. Conventional monitoring methods such as short tandem repeat polymerase chain reaction (STR-PCR) are labor intensive and difficult in showing the dynamics of cell subpopulations. In HLA-haploidentical SCT, flow cytometric analysis using anti-HLA antibody for the mismatched HLA can be useful in observing changes of cell subpopulations and determining chimerism. We designed a specific panel of HLA antibody reagents for the Korean population, and verified its clinical application in flow cytometric monitoring of chimerism after haploidentical stem cell transplantation. A total of 12 anti-HLA-A, -B-antibodies were selected, which could cover 82.5% of HLA-A and 16.5% of HLA-B in Korean population. This HLA panel distinguished donor and recipient cells in 22 of 23 HLA-haploidentical SCT cases. In one case, the patient had HLA-A*02/A*24, B*48/B*61 while the donor had HLA-A*02/A*33, B*44/B*48. The donor type HLA-B*44(+) and CD3(+) T cells, and HLA-B*44(+) and CD56(+) NK cells were seen at day 14 and day 8, respectively. Increased HLA-B*44(+) cells throughout the study period indicated the engraftment of donor stem cells. We were able to design a population specific panel of HLA-antibodies, and verified that flow cytometric analysis using HLA antibody for the detection of chimerism in HLA-haploidentical SCT was a simple and sensitive monitoring technique. This method allowed us to observe the dynamic changes in cell subpopulations after HLA-haploidentical SCT. Flow cytometric analysis can be considered as a strong tool for the monitoring of engraftment in HLA-haploidentical SCT.

Mycoplasma hyorhinis is a potential pathogen of porcine respiratory disease complex that aggravates pneumonia caused by porcine reproductive and respiratory syndrome virus.

The porcine respiratory disease complex (PRDC) caused by numerous bacterial and viral agents has a great impact on pig industry worldwide. Although Mycoplasma hyorhinis (Mhr) has been frequently isolated from lung lesions from pigs with PRDC, the pathological importance of Mhr may have been underestimated. In this study, 383 serum samples obtained from seven herds with a history of PRDC were tested for specific antibodies to Mhr, Mycoplasma hyopneumoniae (Mhp), and porcine reproductive and respiratory syndrome virus (PRRSV). Seropositive rates of PRRSV were significantly correlated with those of Mhr (correlation coefficient, 0.862; P-value, 0.013), but not with those of Mhp (correlation coefficient, -0.555; P-value, 0.196). In vivo experiments demonstrated that pigs co-infected with Mhr and PRRSV induced more severe lung lesions than pigs infected with Mhr or PRRSV alone. These findings suggest that Mhr is closely associated with pneumonia caused by PRRSV and provide important information on Mhr pathogenesis within PRDC. Therefore, effective PRDC control strategies should also consider the potential impact of Mhr in the pathogenesis of PRDC.