Effect of an interdisciplinary inpatient program for patients with CRPS in reducing disease activity -a single center prospective cohort study.

OBJECTIVE: The aim of this study was to evaluate the benefit of inpatient treatment in reducing disease activity in patients with CRPS who have exhausted outpatient options. Furthermore, the study sought to identify patient-related outcome variables that predict a reduction in disease activity. METHODS: The primary outcome was disease severity (CRPS Severity Score, range 0-16 points)). Secondary outcomes included depression, anxiety, physical function, pain interference, fatigue, sleep disturbance, and ability to participate in social roles and activities, all of which were assessed using the Promis-29. Furthermore, pain catastrophizing, neuropathic pain, quality of life, pain self-efficacy, medication intake, and the patient's global impression of change were examined in accordance with current international agreed recommendations, assessed at discharge, three-month and six-month post-discharge. Mixed-effects models were conducted to identify baseline variables associated with CRPS severity. RESULTS: Twenty-five patients completed the program (mean age 49.28 (SD 11.23) years, 92% females, mean symptom duration 8.5 (SD 6.5) months). Results showed a significant reduction between baseline and discharge of disease activity (CSS -2.36, p < 0.0001), pain (PROMIS-29 pain -0.88, p = 0.005) and emotional function (PROMIS-29 depression -5.05, p < 0.001; fatigue -4.63, p = 0.002). Moderate evidence for a reduction between baseline and discharge could be observed for pain interference (+2.27, p = 0.05), social participation (PROMIS-29 +1.93, p = 0.05), anxiety (PROMIS-29 -3.32, p = 0.02) and physical function (PROMIS-29 +1.3, p = 0.03). On discharge, 92% of patients (23 of 25) reported improvement in their overall condition. In the follow-up period, medication intake could be reduced after 3 (MQS -8.22, p = 0.002) and 6 months (MQS -8.69, p = 0.001), and there was further improvement in social participation after 3 months (PROMIS-29 +1.72, 0.03) and sleep after 6 months (PROMIS-29 +2.38, 0.008). In the mixed models, it was demonstrated that patients experiencing less pain at baseline also exhibited lower disease activity. CONCLUSION: The results of this study confirm that inpatient interdisciplinary treatment of CRPS patients improves disease activity, pain, physical function, emotional function, and social participation. Most improvements were maintained for up six months after discharge. The majority of patients reported that their overall condition had improved during the study period.

MRI characterization of pelvic floor ligaments in nulliparous women: Technique development and morphometry within the 3D pelvic inclination correction system (3D-PICS).

PURPOSE: The aim of the MRI-study was to evaluate the visibility of the pelvic floor ligaments and to analyze the ligament morphometry in 3D space. METHODS: Twenty-two nulliparous women underwent MRI with a ligament specific protocol. MR datasets were evaluated using the 3D Pelvic Inclination Correction System (3D-PICS). The round ligament (RL), sacrospinous ligament (SSL), sacrotuberous ligament (STL), urogenital diaphragm (UGD) and uterosacral ligament (USL) were analyzed. Qualitative and quantitative analysis was performed. 3D coordinates for origin and insertion points were determined relative to the symphysis; subsequently lengths and angles were calculated. Interrater reliability was calculated to validate the point determination method. RESULTS: Moderate to good visibility was reported for the RL, the SSL, the STL and the UGD. Standard deviation of the points analyzed in the different dimensions vary from 1.5 mm to 21.3 mm. Origin and insertion points of the ligaments are found within a mean standard distance of 10.7 mm. The highest variability was seen in insertion points of RL, with a standard distance of 25.4 mm. The interrater reliability was good to very good (range of intraclass correlation coefficients (ICC) from 0.58 to 0.96), except for the UGD ventral points (ICC from 0.27 to 0.55). CONCLUSIONS: This in-vivo MRI technique development study offers first exact data describing the pelvic floor ligaments in nulliparous women in 3D-PICS. Visibility, exact 3D coordinates of the origin and insertion points, lengths, angles and interrater reliability assessed for all parameters were evaluated morphometrically.

CT Angiography of the Aorta Using Photon-counting Detector CT with Reduced Contrast Media Volume.

Purpose: To develop and evaluate a low-volume contrast media protocol for thoracoabdominal CT angiography (CTA) with photon-counting detector (PCD) CT. Materials and Methods: This prospective study included consecutive participants (April-September 2021) who underwent CTA with PCD CT of the thoracoabdominal aorta and previous CTA with energy-integrating detector (EID) CT at equal radiation doses. In PCD CT, virtual monoenergetic images (VMI) were reconstructed in 5-keV intervals from 40 to 60 keV. Attenuation of the aorta, image noise, and contrast-to-noise ratio (CNR) were measured, and subjective image quality was rated by two independent readers. In the first group of participants, the same contrast media protocol was used for both scans. CNR gain in PCD CT compared with EID CT served as the reference for contrast media volume reduction in the second group. Noninferiority analysis was used to test noninferior image quality of the low-volume contrast media protocol with PCD CT. Results: The study included 100 participants (mean age, 75 years ± 8 [SD]; 83 men). In the first group (n = 40), VMI at 50 keV provided the best trade-off between objective and subjective image quality, achieving 25% higher CNR compared with EID CT. Contrast media volume in the second group (n = 60) was reduced by 25% (52.5 mL). Mean differences in CNR and subjective image quality between EID CT and PCD CT at 50 keV were above the predefined boundaries of noninferiority (-0.54 [95% CI: -1.71, 0.62] and -0.36 [95% CI: -0.41, -0.31], respectively). Conclusion: CTA of the aorta with PCD CT was associated with higher CNR, which was translated into a low-volume contrast media protocol demonstrating noninferior image quality compared with EID CT at the same radiation dose.Keywords: CT Angiography, CT-Spectral, Vascular, Aorta, Contrast Agents-Intravenous, Technology Assessment© RSNA, 2023See also the commentary by Dundas and Leipsic in this issue.

HLA-B27 as a predictor of effectiveness of treatment with TNF inhibitors in axial spondyloarthritis: data from the Swiss Clinical Quality Management Registry.

OBJECTIVE: To explore the impact of the human leucocyte antigen (HLA)-B27 on the effectiveness of tumor necrosis factor inhibitors (TNFi) in patients with axial spondyloarthritis (axSpA). METHODS: A total of 1109 patients with available HLA-B27 status (831 B27+ patients and 278 B27- patients) fulfilling the Assessment of Spondyloarthritis international Society classification criteria for axSpA from the prospective Swiss Clinical Quality Management Registry initiating a first TNFi were included. Drug retention was investigated with multiple adjusted Cox proportional hazard models with imputation of missing values. Multiple-adjusted logistic regression analyses were used to assess the proportion of patients reaching 50% reduction in the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI50) at 1 year. RESULTS: B27+ and B27- patients differed with regard to age, sex, BASDAI, C-reactive protein (CRP), body mass index, enthesitis, uveitis, and classification status. After adjustment for potential confounders for the relationship between HLA-B27 and drug effectiveness (sex and family history of spondyloarthritis), a higher risk of drug discontinuation was found in B27- patients (HR 1.53, 95% CI 1.27-1.83). This difference decreased after additional adjustment for parameters which may act as mediators (HR 1.30, 95% CI 1.30-1.55). Male sex and elevated C-reactive protein (CRP) levels were consistently associated with longer retention. Comparable results were obtained for BASDAI50 responses. CONCLUSION: The HLA-B27 genotype is an important predictor of treatment effectiveness. Male sex and CRP seem, however, to better describe variability of response in individual patients. This data may help avoiding potential discrimination of B27- individuals with regard to TNFi initiation. Key Points • HLA-B27 is a predictor of effectiveness of TNF inhibitors in axial spondyloarthritis. • Variability of response in individual patients is better defined by sex and objective markers of disease activity, such as C-reactive protein.

Prospective validation and extension of the Multimodality Prognostic Score for the treatment allocation of pleural mesothelioma patients.

OBJECTIVES: Patient allocation to multimodality treatment in patients with malignant pleural mesothelioma remains a challenge. The aim of this study was to validate our previously established Multimodality Prognostic Score (MMPS) (tumour volume before chemotherapy, histological subtype, C-reactive protein before chemotherapy and tumour progression after chemotherapy) and to extend the score with additional blood parameters for better patient outcome. METHODS: Patients with histologically proven malignant pleural mesothelioma and curative intended therapy with clinical stage T1-T3 N0-N2 M0 were eligible. The existing MMPS was validated and further additional blood markers (erythrocytes, neutrophils, monocytes, albumin, gamma-glutamyl transferase and alkaline phosphatase) were evaluated for potential incorporation. RESULTS: For the validation of the existing MMPS, as the first part of this analysis, 117 patients treated as of September 2011 were included. A total of 88 patients were treated with macroscopic complete resection, whereas 29 patients were treated with palliative or no surgery. Patients treated with macroscopic complete resection and a high MMPS showed statistically significant lower overall survival. In the second part, the extension of the MMPS with additional blood parameters was analysed. Albumin, the only parameter showing evidence for having influence on overall survival, was further added to the extended MMPS. When comparing the performance measures Area under the curve (AUC) and Brier score, the extended score performed better (higher AUC, lower Brier score) than the original MMPS. CONCLUSIONS: The extended score with albumin showed improved performance in comparison to the original score. The extended MMPS also may help allocating patients to surgery.

Current differentiation between radiographic and non-radiographic axial spondyloarthritis is of limited benefit for prediction of important clinical outcomes: data from a large, prospective, observational cohort.

OBJECTIVE: To compare disease characteristics and outcomes between patients with axial spondyloarthritis with non-radiographic disease (nr-axSpA), bilateral grade 2 sacroiliitis (r22axSpA) and unilateral/bilateral grade 3-4 sacroiliitis (r3+axSpA) according to the modified New York criteria. METHODS: We included patients with axial spondyloarthritis with available pelvic radiographs from the Swiss Clinical Quality Management Cohort. Retention of a first tumour necrosis factor inhibitor (TNFi) was investigated with multiple adjusted Cox proportional hazards models. The proportion of patients reaching 50% reduction in the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI50) at 1 year was assessed with multiple adjusted logistic regression analyses. Spinal radiographic progression, defined as an increase in ≥2 mSASSS units in 2 years, was assessed in generalised estimating equation models. RESULTS: From 2080 patients, those with nr-axSpA (n=485) and r22axSpA (n=443) presented with lower C reactive protein levels and less severe clinical spinal involvement compared with patients with r3+axSpA (n=1152). While TNFi retention was similar in r22axSpA and nr-axSpA, the risk of discontinuation was significantly lower in r3+axSpA (HR 0.60, 95% CI 0.44 to 0.82 vs nr-axSpA). BASDAI50 responses at 1 year were comparable in r22axSpA and nr-axSpA, with a better response associated with r3+axSpA (OR 2.05, 95% CI 1.09 to 3.91 vs nr-axSpA). Spinal radiographic progression was similar in r22axSpA and nr-axSpA and significantly higher in r3 +axSpA. CONCLUSION: Patients with r22axSpA are comparable to nr-axSpA patients but differ from patients with more severe sacroiliac damage with regard to treatment effectiveness and spinal radiographic progression. Therefore, current differentiation between nr-axSpA and radiographic disease seems of limited use for outcome prediction.

Preoperative clinical symptomatology and stroke burden in pediatric moyamoya angiopathy: Defining associated risk variables.

OBJECTIVE: To evaluate the preoperative clinical and magnetic resonance imaging and angiography (MRI-MRA) characteristics in pediatric moyamoya patients. METHODS: Analysis included 100 children with moyamoya angiopathy referred to our moyamoya center for preoperative evaluation. Clinical symptoms, neurological status using Pediatric Stroke Outcome Measurement (PSOM) and degree of disability on modified Rankin scale score (mRS) were evaluated. MRI-MRA evaluation included the assessment of ischemic lesions and involvement of posterior circulation. Data were analyzed for moyamoya disease (MMD), moyamoya syndrome (MMS) and age at disease onset. RESULTS: Stroke was a common presentation in both MMD and MMS patients. TIAs and headaches/migraine were more frequent in MMD. There was no evidence of a difference in stroke burden on MRI as well as in PCA involvement between the two subgroups. Children <2 years had higher odds of having a stroke (OR 15.5, 95% CI 3.8-62.4, p < 0.001), recurrent stroke (OR 11.8, 95%CI 2.9-46.7, p < 0.001) and unfavorable mRS (≥2) (OR 4.2, 95% CI 1.3-13.7, p = 0.01) when compared to those >5 years of age. There was some evidence of association of PCA involvement with recurrent strokes (OR 3.1, CI 1.0-9.6, p = 0.05), a poor PSOM (OR 3.0, 95% CI 1.1-8.2, p = 0.04) and mRS (OR 3.1, 95% CI 1.2-8.3, p = 0.02). CONCLUSION: Stroke seems to be a common presentation in both MMD and MMS patients. Early age at symptom onset and involvement of posterior circulation seem to be important risk factors for a high stroke burden and an unfavorable PSOM and mRS.

Site of Recurrence and Survival After Surgery for Colorectal Peritoneal Metastasis.

BACKGROUND: Multimodal treatment, including systemic treatment and surgery, improved the prognosis of peritoneal metastasis (PM). Despite all efforts, recurrence rates remain high, and little data are available about clinical behavior or molecular patterns of PM in comparison to hematogenous metastasis. Here, we aimed to analyze recurrence patterns after multimodal treatment for PM from colorectal cancer. METHODS: Patients with colorectal PM undergoing multimodal treatment including systemic chemotherapy and cytoreductive surgery plus hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) between 2005 and 2017 at 4 centers were analyzed retrospectively. RESULTS: A total of 505 patients undergoing CRS/HIPEC were analyzed. Of the patients, 82.1% received preoperative chemotherapy. Median peritoneal cancer index was 6 (interquartile range = 3-11). Median disease-free and overall survival was 12 (95% confidence interval [CI] = 11 to 14) months and 51 (95% CI = 43 to 62) months, respectively. Disease recurred in 361 (71.5%) patients, presenting as isolated peritoneal recurrence in 24.6%, isolated hematogenous recurrence in 28.3%, and mixed recurrence in 13.9% of patients. Recurrence to the peritoneum was associated with an impaired time from recurrence to death of 21 (95% CI = 18 to 31) months for isolated peritoneal and 22 (95% CI = 16 to 30) months for mixed recurrence, compared with 43 (95% CI = 31 to >121) months for hematogenous recurrence (hazard ratio [HR] = 1.79, 95% CI = 1.27 to 2.53; P = .001; and HR = 2.44, 95% CI = 1.61 to 3.79; P < .001). On multiple logistic regression analysis, RAS mutational status (odds ratio [OR] = 2.42, 95% CI = 1.11 to 5.47; P = .03) and positive nodal stage of the primary (OR = 3.88, 95% CI = 1.40 to 11.86; P = .01) were identified as predictive factors for peritoneal recurrence. CONCLUSIONS: This study highlights the heterogeneity of peritoneal metastasis in patients with colorectal cancer. Recurrent peritoneal metastasis after radical treatment represents a more aggressive subset of metastatic colorectal cancer.

Differences between men and women with nonradiographic axial spondyloarthritis: clinical characteristics and treatment effectiveness in a real-life prospective cohort.

BACKGROUND: Sex differences with regard to clinical manifestations and response to tumor necrosis factor inhibitors (TNFi) have been delineated for the radiographic form of axial spondyloarthritis (axSpA). More limited evidence for a differential effectiveness of treatment in genders exists for the nonradiographic disease state (nr-axSpA). The aim of the study was to compare demographics, clinical parameters, and response to TNFi in women versus men with nr-axSpA. METHODS: We compared disease characteristics of 264 women and 231 men with nr-axSpA at inclusion in the prospective Swiss Clinical Quality Management Cohort. Response to a first TNFi was assessed in 85 women and 78 men without diagnosed co-morbid fibromyalgia. The primary outcome was the proportion of patients achieving the 40% improvement in the Assessment of SpondyloArthritis international Society criteria (ASAS40) at 1 year. Additional response outcomes were evaluated as secondary outcomes. Patients having discontinued TNFi were considered non-responders. Logistic regression analyses were adjusted for baseline differences, which might potentially mediate the effect of sex on treatment response. RESULTS: Compared to men, women had a longer diagnostic delay, a higher level of perceived disease activity, and more enthesitis and were in a lower percentage HLA-B27 positive. An ASAS40 response was achieved by 17% of women and 38% of men (OR 0.34; 95% CI 0.12, 0.93; p = 0.02). A significantly lower response rate in women was confirmed in the adjusted analysis (OR 0.19; 95% CI 0.05, 0.62; p = 0.009) as well as for the other outcomes assessed. CONCLUSION: Despite only few sex differences in patient characteristics in nr-axSpA, response rates to TNFi are significantly lower in women than in men.

Spinal radiographic progression in axial spondyloarthritis and the impact of classification as nonradiographic versus radiographic disease: Data from the Swiss Clinical Quality Management cohort.

OBJECTIVE: To investigate whether spinal radiographic progression relates to structural damage at the sacroiliac level in axial spondyloarthritis (axSpA). METHODS: Patients classified as nonradiographic (nr-) and radiographic (r-) axSpA in the Swiss Clinical Quality Management cohort with radiographs performed every 2 years, scored according to the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS), were included. The relationship between classification status and spinal progression during 2 years was investigated using binomial generalized estimating equations models with adjustment for sex, ankylosing spondylitis disease activity score (ASDAS) and tumour necrosis factor inhibitor treatment. Baseline spinal damage was considered an intermediate variable and included in sensitivity analyses. RESULTS: In total, 88 nr-axSpA and 418 r-axSpA patients contributed to data for 725 radiographic intervals. R-axSpA patients were more frequently male, had a longer disease duration and higher structural damage at baseline. Mean (SD) mSASSS change over 2 years was 0.16 (0.62) units in nr-axSpA and 0.92 (2.78) units in r-axSpA, p = 0.01. Nr-axSpA was associated with a significantly lower progression in 2 years (defined as an increase in ≥2 mSASSS units) in adjusted analyses (OR 0.33, 95%CI 0.13; 0.83), confirmed with progression defined as the formation of ≥1 syndesmophyte. Mediation analyses revealed that sacroiliitis exerted its effect on spinal progression indirectly by being associated with the appearance of a first syndesmophyte (OR 0.09, 95%CI 0.02; 0.36 for nr-axSpA vs r-axSpA). Baseline syndesmophytes were predictors of further progression. CONCLUSION: Spinal structural damage is mainly restricted to patients with r-axSpA, leading to relevant prognostic and therapeutic implications.

Comparison of drug survival on adalimumab, etanercept, golimumab and infliximab in patients with axial spondyloarthritis.

OBJECTIVES: To compare drug survival in patients with axial spondyloarthritis treated with different TNF inhibitors in standard dosage. METHODS: Patients fulfilling the Assessment in SpondyloArthritis international Society classification criteria for axial spondyloarthritis in the Swiss Clinical Quality Management cohort were included in this study if a first TNF inhibitor on standard dosage was started after recruitment and if a baseline visit was available. Drug maintenance up to drug discontinuation or dose escalation was compared between TNF inhibitors with multiple adjusted Cox proportional hazards models and multiple imputation for missing baseline covariate data. RESULTS: A total of 966 patients were included (adalimumab 344, etanercept 237, golimumab 214, infliximab 171). Patients on certolizumab (n = 18) were excluded. Patients starting golimumab had lower disease activity as well as better physical function and quality of life in comparison to patients starting another drug. A higher proportion of patients starting infliximab had a history of extra-articular manifestations. Drug dosage was more often escalated during follow-up in patients treated with infliximab than with subcutaneously administered agents. However, no significant differences in time up to drug discontinuation or dose escalation were observed in multiple adjusted analyses if treatment was initiated after 2009, when all 4 TNF inhibitors were available: hazard ratio for infliximab versus etanercept 1.16 (95% confidence interval 0.80; 1.67), p = 0.44, for golimumab versus etanercept 0.80 (0.58; 1.10), p = 0.17 and for adalimumab versus etanercept 0.93 (0.69; 1.26), p = 0.66. CONCLUSION: In axial spondyloarthritis, drug survival with standard doses of different TNF inhibitors is comparable.

Response to Tumor Necrosis Factor Inhibition in Male and Female Patients with Ankylosing Spondylitis: Data from a Swiss Cohort.

OBJECTIVE: To investigate sex differences in connection with the effectiveness of tumor necrosis factor inhibitors (TNFi) in patients with ankylosing spondylitis (AS). METHODS: A total of 440 patients with AS (294 men; 146 women) initiating a first TNFi in the prospective Swiss Clinical Quality Management Cohort were included. We evaluated the proportion of patients achieving the 20% and 40% improvement in the Assessment of Spondyloarthritis international Society criteria (ASAS20 and ASAS40) as well as Ankylosing Spondylitis Disease Activity Score (ASDAS) improvement and status scores at 1 year. Patients having discontinued TNFi were considered nonresponders. Logistic regression analyses were performed to adjust for important predictors of response. RESULTS: Compared to men, female patients had lower mean C-reactive protein levels, better spinal mobility, and more peripheral disease at the start. There was no sex disparity with regard to the ASDAS, the Bath Ankylosing Spondylitis Disease Activity and Functional indices, and the quality of life. At 1 year, 52% of women and 63% of men achieved an ASAS20 response (OR 0.63, 95% CI 0.37-1.07, p = 0.09). An inactive disease status (ASDAS < 1.3) was reached by 18% of women and 26% of men (OR 0.65, 95% CI 0.32-1.27, p = 0.22). These sex differences in response to TNFi were more pronounced in adjusted analyses (OR 0.34, 95% CI 0.16-0.71, p = 0.005 for ASAS20 and OR 0.10, 95% CI 0.03-0.31, p < 0.001 for ASDAS < 1.3) and confirmed for all the other outcomes assessed. CONCLUSION: In AS, fewer women respond to TNFi and women show a reduced response in comparison to men.

Impact of obesity on the response to tumor necrosis factor inhibitors in axial spondyloarthritis.

BACKGROUND: Few studies have investigated the impact of obesity on the response to tumor necrosis factor inhibitors (TNFi) in patients with axial spondyloarthritis (axSpA). The aim of our study was to investigate the impact of different body mass index (BMI) categories on TNFi response in a large cohort of patients with axSpA. METHODS: Patients with axSpA within the Swiss Clinical Quality Management (SCQM) program were included in the current study if they fulfilled the Assessment in Spondyloarthritis International Society (ASAS) criteria for axSpA, started a first TNFi after recruitment, and had available BMI data as well as a baseline and follow-up visit at 1 year (±6 months). Patients were categorized according to BMI: normal (BMI 18.5 to <25), overweight (BMI 25-30), and obese (BMI >30). We evaluated the proportion of patients achieving the 40% improvement in ASAS criteria (ASAS40), as well as Ankylosing Spondylitis Disease Activity Score (ASDAS) improvement and status scores at 1 year. Patients having discontinued the TNFi were considered nonresponders. We controlled for age, sex, HLA-B27, axSpA type, BASDAI, BASMI, elevated C-reactive protein (CRP), current smoking, enthesitis, physical exercise, and co-medication with disease-modifying antirheumatic drugs, as well as with nonsteroidal anti-inflammatory drugs in multiple adjusted logistic regression analyses. RESULTS: A total of 624 axSpA patients starting a first TNFi were considered in the current study (332 patients of normal weight, 204 patients with overweight, and 88 obese patients). Obese individuals were older, had higher BASDAI levels, and had a more important impairment of physical function in comparison to patients of normal weight, while ASDAS and CRP levels were comparable between the three BMI groups. An ASAS40 response was reached by 44%, 34%, and 29% of patients of normal weight, overweight, and obesity, respectively (overall p = 0.02). Significantly lower odds ratios (ORs) for achieving ASAS40 response were found in adjusted analyses in obese patients versus patients with normal BMI (OR 0.27, 95% confidence interval (CI) 0.09-0.70). The respective adjusted ASAS40 OR in overweight versus normal weight patients was 0.62 (95% CI 0.24-1.14). Comparable results were found for the other outcomes assessed. CONCLUSIONS: Obesity is associated with significantly lower response rates to TNFi in patients with axSpA.

Impedance flow cytometry gauges proliferative capacity by detecting TRPC1 expression.

When examined, the expansion of many stem cell classes has been shown to be facilitated by mechanically-regulated calcium entry from the extracellular space that also helps direct their developmental programs towards mechanosensitive tissues such as muscle, bone, and connective tissues. Cation channels of the transient receptor potential C class (TRPC) are the predominant conduit for calcium entry into proliferating myoblasts. Nonetheless, methods to non-invasively study this calcium-entry pathway are still in their infancy. Here we show that a microfluidic configuration of impedance-based flow cytometry (IFC) provides a method to detect TRP channel expression in cells at high throughput. Using this technology we discern changes in the IFC signal that correlates with the functional expression of TRPC1 channels and coincides with cell proliferation. Pharmacological agents, mechanical conditions or malignant states that alter the expression of TRPC1 channels are reflected in the IFC signal accordingly, whereas pharmacological agents that alter cation-permeation through TRPC1 channels, or ionophores that independently increase calcium entry across the membrane, have little effect. Our results suggest that IFC detects changes in whole-cell membrane organization associated with TRPC1 activation and surface expression, rather than cation permeation through the channel per se. IFC-based technologies thus have the potential to identify living stem cells in their earliest stages of expansion without staining or chemical fixation.

Label-free hybridoma cell culture quality control by a chip-based impedance flow cytometer.

Impedance flow cytometry (IFC) was evaluated as a possible alternative to fluorescence-based methods for on-line quality monitoring of hybridoma cells. Hybridoma cells were cultured at different cell densities and viability was estimated by means of IFC and fluorescence-based flow cytometry (FCM). Cell death was determined by measuring the impedance phase value at high frequency in low conductivity buffer. IFC data correlate well with reference FCM measurements using AnnexinV and 7-AAD staining. Hybridoma cells growing at different densities in cell culture revealed a density-dependent subpopulation pattern. Living cells of high density cultures show reduced impedance amplitudes, indicating particular cellular changes. Dead cell subpopulations become evident in cultures with increasing cell densities. In addition, a novel intermediate subpopulation, which most probably represents apoptotic cells, was identified. These results emphasize the extraordinary sensitivity of high frequency impedance measurements and their suitability for hybridoma cell culture quality control.

Microfluidic impedance-based flow cytometry.

Microfabricated flow cytometers can detect, count, and analyze cells or particles using microfluidics and electronics to give impedance-based characterization. Such systems are being developed to provide simple, low-cost, label-free, and portable solutions for cell analysis. Recent work using microfabricated systems has demonstrated the capability to analyze micro-organisms, erythrocytes, leukocytes, and animal and human cell lines. Multifrequency impedance measurements can give multiparametric, high-content data that can be used to distinguish cell types. New combinations of microfluidic sample handling design and microscale flow phenomena have been used to focus and position cells within the channel for improved sensitivity. Robust designs will enable focusing at high flowrates while reducing requirements for control over multiple sample and sheath flows. Although microfluidic impedance-based flow cytometers have not yet or may never reach the extremely high throughput of conventional flow cytometers, the advantages of portability, simplicity, and ability to analyze single cells in small populations are, nevertheless, where chip-based cytometry can make a large impact.