Cytokine Receptor-like Factor 1 (CRLF1) and Its Role in Osteochondral Repair.

BACKGROUND: Since cytokine receptor-like factor 1 (CRLF1) has been implicated in tissue regeneration, we hypothesized that CRLF1 released by mesenchymal stem cells can promote the repair of osteochondral defects. METHODS: The degree of a femoral osteochondral defect repair in rabbits after intra-articular injections of bone marrow-derived mesenchymal stem cells (BMSCs) that were transduced with empty adeno-associated virus (AAV) or AAV containing CRLF1 was determined by morphological, histological, and micro computer tomography (CT) analyses. The effects of CRLF1 on chondrogenic differentiation of BMSCs or catabolic events of interleukin-1beta-treated chondrocyte cell line TC28a2 were determined by alcian blue staining, gene expression levels of cartilage and catabolic marker genes using real-time PCR analysis, and immunoblot analysis of Smad2/3 and STAT3 signaling. RESULTS: Intra-articular injections of BMSCs overexpressing CRLF1 markedly improved repair of a rabbit femoral osteochondral defect. Overexpression of CRLF1 in BMSCs resulted in the release of a homodimeric CRLF1 complex that stimulated chondrogenic differentiation of BMSCs via enhancing Smad2/3 signaling, whereas the suppression of CRLF1 expression inhibited chondrogenic differentiation. In addition, CRLF1 inhibited catabolic events in TC28a2 cells cultured in an inflammatory environment, while a heterodimeric complex of CRLF1 and cardiotrophin-like Cytokine (CLC) stimulated catabolic events via STAT3 activation. CONCLUSION: A homodimeric CRLF1 complex released by BMSCs enhanced the repair of osteochondral defects via the inhibition of catabolic events in chondrocytes and the stimulation of chondrogenic differentiation of precursor cells.

Laceration of the Sciatic Nerve After Closed Reduction of a Dislocated Total Hip Arthroplasty.

Sciatic nerve injury after closed reduction of a dislocated total hip arthroplasty (THA) is an exceedingly rare but tremendously devastating complication. Closed reduction is the standard of care and is typically associated with a low complication rate. There have only been seven sciatic nerve injuries after closed reduction of a dislocated THA reported in the literature, and none were secondary to nerve laceration. We report a case of sciatic nerve laceration after attempted closed reduction of a dislocated THA. This resulted in complete loss of sensory and motor sciatic nerve function. This case highlights the importance of a detailed neurologic examination before and after closed reduction of a dislocated total hip, the importance of using careful reduction maneuvers, and transitioning to open reduction when necessary.

Effect of documented and undocumented psychiatric conditions on length of stay and discharge destination after total knee arthroplasty.

INTRODUCTION: Length of stay (LOS) and readmissions are quality metrics linked to physician payments and substantially impact the cost of care. This study aims to evaluate the effect of documented and undocumented psychiatric conditions on LOS, discharge location, and readmission following total knee arthroplasty (TKA). METHODS: Retrospective review of all primary, unilateral TKA from 2015 to 2020 at a high-volume, academic orthopedic hospital was conducted. Patients were separated into three cohorts: patients with a documented psychiatric diagnosis (+Dx), patients without a documented psychiatric diagnosis but with an actively prescribed psychiatric medication (-Dx), and patients without a psychiatric diagnosis or medication (control). Patient demographics, LOS, discharge location, and 90 days readmissions were assessed. RESULTS: A total of 2935 patients were included; 1051 patients had no recorded psychiatric medications (control); 1884 patients took at least one psychiatric medication, of which 1161 (61.6%) were in the-Dx and 723 (38.4%) were in the +Dx cohort. Operative time (+Dx, 103.4 ± 29.1 and -Dx, 103.1 ± 28.5 vs. 93.6 ± 26.2 min, p < 0.001 for both comparisons) and hospital LOS stay (+ Dx, 3.00 ± 1.70 and -Dx, 3.01 ± 1.83 vs. 2.82 ± 1.40 days, p = 0.021 and p = 0.006, respectively) were greater for patients taking psychiatric medications when compared to the control group. Patients taking psychiatric medication with or without associated diagnosis were significantly more likely to be discharged to a secondary facility-22.8% and 20.9%, respectively-compared to controls, at 12.5% (p < 0.001). Ninety-day readmission rates did not differ between the control and both psychiatric groups (p = 0.693 and p = 0.432, respectively). CONCLUSION: TKA patients taking psychiatric medications with or without a documented psychiatric diagnosis have increased hospital LOS and higher chances of discharge to a secondary facility. Most patients taking psychiatric medication also had no associated diagnosis. Payment models should consider the presence of undocumented psychiatric diagnoses when constructing metrics. Surgeons and institutions should also direct their attention to identifying, recording, and managing these patients to improve outcomes. LEVEL III EVIDENCE: Retrospective Cohort Study.

Impact of Admission Source on Shoulder Arthroplasty.

BACKGROUND: The purpose of this study was to determine the relationship between admission source and postoperative length of stay (LOS), index admission hospital charges, and discharge disposition, in patients undergoing shoulder arthroplasty. METHODS: The New York Statewide Planning and Research Cooperative System (SPARCS) was used to identify all patients that underwent elective shoulder arthroplasty from 1994 through 2015. Patients were grouped into institutionalized (INS) versus non-institutionalized (n-INS) groups based on admission source. The two groups were compared regarding demographics, Charleston comorbidity index (CCI), postoperative blood transfusion requirement, LOS, and total charges. RESULTS: A total of 33,248 patients were identified (32,875 n-INS, 373 INS). Patientsin the INS cohort were significantly older (71.9 versus 68.1 years) and had a higher CCI (1.3 vs. 0.7). The mean LOS in the INS group was nearly 1 week longer(9.5 days vs. 2.8 days) and had a significantly higher postoperative blood transfusion rate (37.5% vs. 9.2%, odds ratio: 5.9). The mean total hospital charges in the INS group were also significantly higher ($63,988 vs. $36,826). DISCUSSION: Institutionalized patients undergoing shoulder arthroplasty have a protracted postoperative hospital course and this ultimately resulted in poorer outcomes and increased resource utilization.

Dual Mobility in Total Hip Arthroplasty.

Dual mobility designs in total arthroplasty allow for increased range of motion prior to impingement and dislocation. While valuable for reducing dislocation, dual mobility has its own unique complication profile that includes intraprosthetic dislocation, corrosion, and femoral notching. Despite these relatively rare complications, dual mobility articulations are valuable options for patients at higher risk of dislocation-both early and contemporary reports on dual mobility in total hip arthroplasty suggest that it can reduce the risk of dislocation without leading to unacceptable rates of complication or early revision. Cost analyses and longer follow-up studies on newer dual mobility designs will help determine the future of dual mobility in total hip arthroplasty.

Changes in the Synovial Fluid Cytokine Profile of the Knee Between an Acute Anterior Cruciate Ligament Injury and Surgical Reconstruction.

BACKGROUND: Changes in the intra-articular inflammatory state during the immediate period after an acute anterior cruciate ligament (ACL) rupture are not well defined. PURPOSE: To evaluate changes in the concentration of select proinflammatory and anti-inflammatory synovial fluid cytokines during the interval between an ACL injury and surgical reconstruction. STUDY DESIGN: Descriptive laboratory study. METHODS: In patients with an acute ACL injury, a synovial fluid sample was obtained from the injured knee during the initial office visit within 2 weeks of the inciting traumatic event. An additional synovial fluid sample was collected at the time of ACL reconstruction just before the surgical incision. Synovial fluid samples from both the acute injury and the surgery time points were processed with a protease inhibitor, and the concentrations of 10 cytokines of interest were measured using a multiplex magnetic bead immunoassay. The primary outcome was the change in cytokine concentrations between time points. RESULTS: A total of 20 patients with a mean age of 30.2 ± 8.3 years were included. The acute injury synovial fluid samples were collected at 6.6 ± 3.8 days after the injury. The surgical synovial fluid samples were collected at 31.6 ± 15.6 days after the acute injury samples. Based on a series of linear mixed-effects models to control for the effect of concomitant meniscal injuries and by-patient variability, there was a statistically significant increase in the concentrations of RANTES and bFGF and a statistically significant decrease in the concentrations of IL-6, MCP-1, MIP-1ß, TIMP-1, IL-1Ra, and VEGF between time points. CONCLUSION: This study demonstrates the ongoing alterations in the intra-articular microenvironment during the initial inflammatory response in the acute postinjury period. We identified 6 synovial fluid cytokines that significantly decreased and 2 that significantly increased between the first clinical presentation shortly after the injury and the time of surgery 1 month later. CLINICAL RELEVANCE: This study describes the molecular profile of the inflammatory changes between the time of an acute ACL injury and the time of surgical reconstruction 1 month later. A greater understanding of the acute inflammatory response within the knee may be helpful in identifying the optimal timing for a surgical intervention that balances the risk of chondral damage with the likelihood of successful, well-healed reconstruction.

Cementless Primary Total Knee Arthroplasty Will this be the Future?

Cementless fixation in total knee arthroplasty (TKA) offers the potential for biologically active osseointegration and the potential for life-long fixation. With early cementless TKA designs, several design issues were identified related to early failure, particularly with the tibial and patellar components. However, in the recent two decades, with improvements upon the early designs, particularly in porous metal technology as well as improved early biomechanical stability, interest was re-established in cementless TKA. The surgical technique for cementless TKA is more exacting than cemented technique, with an important emphasis on indications, accurate resections, and component alignment. Modern cementless TKA designs have demonstrated excellent early- and mid-term survivorship equivalent to cemented TKA. More long-term studies are needed to study this comparison. While implant cost maybe higher with cementless designs, there is emerging evidence that there may be an overall cost saving with the use of cementless components given the shorter operative time and the savings in the cost of supplies associated with the use of cement. As the population undergoing TKA is becoming younger and more active, interest in the use of cementless implants will likely increase.

Aseptic Loosening of Porous Metaphyseal Sleeves and Tantalum Cones in Revision Total Knee Arthroplasty: A Systematic Review.

Bone loss often complicates revision total knee arthroplasty (TKA). Management of metaphyseal defects varies, with no clearly superior technique. Two commonly utilized options for metaphyseal defect management include porous-coated metaphyseal sleeves and tantalum cones. A systematic review was conducted according to the international Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We combined search terms "Total knee arthroplasty" AND/OR "Sleeve," "Cone" as either keywords or medical subject heading (MeSH) terms in multiple databases according to PRISMA recommendations. All retrieved articles were reviewed and assessed using defined inclusion and exclusion criteria. A total of 27 studies (12 sleeves and 15 cones) of revision TKAs were included. In the 12 studies on sleeve implantation in revision TKAs, 1,617 sleeves were implanted in 1,133 revision TKAs in 1,025 patients. The overall rate of reoperation was 110/1,133 (9.7%) and the total rate of aseptic loosening per sleeve was 13/1,617 (0.8%). In the 15 studies on tantalum cone implantation in revision TKAs, 701 cones were implanted into 620 revision TKAs in 612 patients. The overall rate of reoperation was 116/620 (18.7%), and the overall rate of aseptic loosening per cone was 12/701 (1.7%). Rates of aseptic loosening of the two implants were found to be similar, while the rate of reoperation was nearly double in revision TKAs utilizing tantalum cones. Variability in the selected studies and the likely multifactorial nature of failure do not allow for any definitive conclusions to be made. This review elucidates the necessity for additional literature examining revision TKA implants.

Subsidence Following Revision Total Hip Arthroplasty Using Modular and Monolithic Components.

BACKGROUND: The ideal femoral component in revision total hip arthroplasty (rTHA) remains undetermined; however, tapered, fluted, titanium (TFT) stems are now widely used with favorable results in all types of revision scenarios. With both modular and monoblock TFT stem options, neither has been proven to be superior. Femoral stem subsidence has been linked to aseptic loosening, instability, and leg length discrepancy. This study aims to assess stem subsidence of modular and monoblock TFT stems at a single urban orthopedic specialty hospital within a tertiary academic medical center. METHODS: Electronic medical records of rTHAs performed between January 2013 and March 2018 utilizing modular and monoblock TFT stems were examined. Data collected included baseline demographics, surgical indication, femoral Paprosky classification, and stem subsidence at most recent follow up (3 months to 3 years). Two-sample t-tests and chi-squared tests were used for statistical analysis. RESULTS: A total of 186 patients (106 modular, 80 monoblock) were included in the analysis. Modular stems underwent significantly greater subsidence than monoblock stems at latest radiographic follow-up (3.9 ± 2.6 vs 2.3 ± 2.5 mm, P < .001). A significantly greater proportion of modular stems underwent >5 mm of subsidence at latest follow-up (29.2% vs 11.3%, P < .001). CONCLUSION: Monoblock TFT stems have displayed promising clinical results in prior studies, and now have been shown to decrease the incidence of postoperative subsidence. With the potential for stem subsidence to lead to aseptic loosening, limb length discrepancy, and instability, the orthopedic surgeon should weigh the risks and benefits of utilizing modular vs monoblock TFT stems in rTHA.

Nonmodular Stems Are a Viable Alternative to Modular Stems in Revision Total Hip Arthroplasty.

BACKGROUND: Nonmodular and modular femoral stems have been associated with complications after revision total hip arthroplasty (rTHA). As such, the ideal femoral component for rTHA remains undecided. This study aims to report outcomes of titanium, tapered-fluted, modular and nonmodular femoral components in rTHA. METHODS: From January 1, 2013 to September 30, 2017, all rTHAs using modular or nonmodular femoral stems were identified. Demographic data including age, gender, and American Society of Anesthesiologists scores were collected. Surgical details including operative time and implant cost were also collected. Clinical outcomes including length of stay, dislocation, infection, fracture, reoperation, and re-revision were collected. Statistical analysis was performed using chi-square test and Student's t-test for all categorical and continuous variables, respectively. RESULTS: One hundred forty-six rTHA cases (103 modular and 43 nonmodular) were identified with an average follow-up of 29 months (range 3-59 months). Nonmodular stems had a significantly lower cost when compared to modular implants (modular stems 120.8% higher cost; P < .001). The surgical time of nonmodular components was significantly greater (193 minutes vs 163 minutes; P = .029). There were no differences observed in any other surgical details or clinical outcomes assessed, including length of stay (P = .323), rate of re-revision of the femoral implant (P = .389), rate of re-operation (P = .383), and postop complications (P = .241), including infection (P = .095), dislocation (P = .778), and fracture (P = .959). CONCLUSIONS: Nonmodular components provide encouraging clinical results with significantly lower costs compared to modular implants in rTHA. The use of titanium, tapered-fluted, nonmodular components may offer a more cost-effective approach to rTHA compared to their modular counterparts.

Alterations in Synovial Fluid Biomarker Levels in Knees With Meniscal Injury as Compared With Asymptomatic Contralateral Knees.

BACKGROUND: Changes in the joint microenvironment after an injury to the articular surface of the knee have been implicated in the pathogenesis of osteoarthritis. While prior studies focused on changes in this microenvironment after anterior cruciate ligament ruptures, few have explored the biomarker changes that occur in the setting of meniscal injuries. PURPOSE: To determine whether meniscal injury results in significant alterations to synovial fluid biomarker concentrations as compared with noninjured contralateral knees. Additionally, to explore the relationship between synovial fluid biomarkers and the degree of cartilage injury seen in these patients. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Patients undergoing surgery for unilateral meniscal injury were prospectively enrolled from October 2011 to December 2016, forming a cohort that had synovial fluid samples collected from both the injured knee and the contralateral uninjured knee at the time of meniscal surgery. Synovial fluid samples were collected just before incision, and the concentrations of 10 biomarkers of interest were determined with a multiplex magnetic bead immunoassay. The concentrations of synovial fluid biomarkers from the operative and contralateral knees were compared. Additionally, the synovial fluid biomarker concentrations of operative knees from patients with associated high-grade cartilage lesions were compared with those with low-grade lesions. RESULTS: The current analysis included synovial fluid samples from 82 knees (41 operative and 41 contralateral) from 41 patients undergoing arthroscopic surgery to treat a symptomatic meniscal injury. The mean ± SD age of patients was 49.86 ± 11.75 years. There were significantly greater concentrations of 4 of the 5 proinflammatory biomarkers (IL-6, MCP-1, MIP-1ß, and MMP-3) in symptomatic knees as compared with asymptomatic knees when controlling for the duration of symptoms, body mass index, age, and the random effects of by-patient variability. In the injured knees, associated high-grade cartilage lesions were predictive of elevated MCP-1, MIP-1ß, and VEGF levels. Low synovial fluid concentration of TIMP-1 or a greater ratio of MMP-3 to TIMP-1 was associated with the presence of synovitis. Increasing age was found to be an independent predictor of increased IL-6, MCP-1, and VEGF concentrations in the setting of symptomatic meniscal injury. CONCLUSION: The authors identified 4 proinflammatory synovial fluid biomarkers whose concentrations were significantly different after meniscal injury as compared with uninjured contralateral knees. Furthermore, they describe the effects of associated cartilage damage, synovitis, and patient age on biomarker concentrations.

Guidelines for Instrumentation for Total Knee Replacement Based on Frontal Plane Radiographs.

OBJECTIVE: The objective of this study was to measure the dimensions and the angulations of the femur and tibia for arthritic knees that were scheduled for total knee surgery. The purpose was to provide information for the design of surgical instruments such as cutting guides. Instruments made using three-dimensional printing were a particular consideration because of the variations in sizing that are possible. MATERIALS AND METHODS: Sixty-six frontal plane EOS radiographs were obtained of patients with osteoarthritis who were under consideration for total knee arthroplasty. The images were imported into computer-assisted design software. The anatomic and mechanical axes and the joint lines were constructed for the femur and tibia. The angles between the axes and lines and key dimensions including the femoral canal diameters were measured. RESULTS: The angle between the anatomic and mechanical axes was 5.5° ± 1.4°, the femoral joint line sloped 2.2°, and the tibial joint line 4.3° to the mechanical axes. The values were similar to non-arthritic knees except for a higher tibial slope. The femoral canal diameter at 150 mm from distal was 19 ± 5 mm. CONCLUSIONS: In a total knee replacement procedure, aligning perpendicular to the mechanical axis results on average about 2° more valgus and 2° to 3° tilt of the joint line. Instruments could be calibrated for individual patients, but the maximum variations based on long-term follow-up should be recognized. A multi-diameter system is needed for the femoral intramedullary rod to limit errors to 1° or less.

Disparities in Discharge Destination After Lower Extremity Joint Arthroplasty: Analysis of 7924 Patients in an Urban Setting.

BACKGROUND: Discharge destination is an important factor to consider to maximize care coordination and manage patient expectations after total joint arthroplasty (TJA). It also has significant impact on the cost-effectiveness of these procedures given the significant cost of post-acute inpatient care. Therefore, understanding factors that impact discharge destination after TJA is critical. METHODS: An evaluation of socioeconomic, geographic, and racial/ethnic factors associated with discharge destination to either home or institution (ie, rehabilitation, skilled nursing facility, and so forth) following joint arthroplasty of the lower extremity was conducted. We analyzed data on patients admitted between 2011 and 2014 for primary or revision hip or knee arthroplasty at a single institution. Bivariate and multivariate statistical techniques were applied to determine associations. RESULTS: Included in the analysis were 7924 cases of lower extremity joint procedures, of which 4836 (61%), 785 (10%), and 2770 (35%) were of female gender, low socioeconomic status, and nonwhite race/ethnicity, respectively. A total of 5088 (64%) and 2836 (36%) cases were discharged to home and institution, respectively. Significant predictors of discharge to an institution in the multivariate analysis include SES (low and middle SES [odds ratio {OR}: 1.27, 95% confidence interval {CI}: 1.02-1.57, P = .029; and OR: 1.26, 95% CI: 1.10-1.44, P = .001]), age (OR: 1.05, 95% CI: 1.049-1.060, P < .001), female gender (OR: 1.69, 95% CI: 1.52-1.89, P < .001) and TKA procedure (OR: 1.48, 95% CI: 1.33-1.64, P < .001). Patients of nonblack race/ethnicity were more likely to be discharged home (white OR: 0.84, 95% CI: 0.72-0.98, P = .027; other OR: 0.80, 95% CI: 0.67-0.95, P = .009). CONCLUSION: Socioeconomic status and race/ethnicity are important factors related to discharge destination following TJA. Thoroughly understanding and addressing these factors may help increase the rates of discharge to home as opposed to institution.

Cost Analysis of Total Joint Arthroplasty Readmissions in a Bundled Payment Care Improvement Initiative.

BACKGROUND: The Bundled Payment for Care Improvement (BPCI) Initiative is a Centers for Medicare and Medicaid Services program designed to promote coordinated and efficient care. This study seeks to report costs of readmissions within a 90-day episode of care for BPCI Initiative patients receiving total knee arthroplasty (TKA) or total hip arthroplasty (THA). METHODS: From January 2013 through December 2013, 1 urban, tertiary, academic orthopedic hospital admitted 664 patients undergoing either primary TKA or THA through the BPCI Initiative. All patients readmitted to our hospital or an outside hospital within 90-days from the index episode were identified. The diagnosis and cost for each readmission were analyzed. RESULTS: Eighty readmissions in 69 of 664 patients (10%) were identified within 90-days. There were 53 readmissions (45 patients) after THA and 27 readmissions (24 patients) after TKA. Surgical complications accounted for 54% of THA readmissions and 44% of TKA readmissions. These complications had an average cost of $36,038 (range, $6375-$60,137) for THA and $38,953 (range, $4790-$104,794) for TKA. Eliminating the TKA outlier of greater than $100,000 yields an average cost of $27,979. Medical complications of THA and TKA had an average cost of $22,775 (range, $5678-$82,940) for THA and $24,183 (range, $3306-$186,069) for TKA. Eliminating the TKA outlier of greater than $100,000 yields an average cost of $11,682. CONCLUSION: Hospital readmissions after THA and TKA are common and costly. Identifying the causes for readmission and assessing the cost will guide quality improvement efforts.

Complications of Total Hip Arthroplasty: Standardized List, Definitions, and Stratification Developed by The Hip Society.

BACKGROUND: Reporting of complications after total hip arthroplasty (THA) is not standardized, and it is done inconsistently across various studies on the topic. Advantages of standardizing complications include improved patient safety and outcomes and better reporting in comparative studies. QUESTIONS/PURPOSES: The purpose of this project was to develop a standardized list of complications and adverse events associated with THA, develop standardized definitions for each complication, and stratify the complications. A further purpose was to validate these standardized THA complications. METHODS: The Hip Society THA Complications Workgroup proposed a list of THA complications, definitions for each complication, and a stratification scheme for the complications. The stratification system was developed from a previously validated grading system for complications of hip preservation surgery. The proposed complications, definitions, and stratification were validated with an expert opinion survey of members of The Hip Society, a case study evaluation, and analysis of a large administrative hospital system database with a focus on readmissions. RESULTS: One hundred five clinical members (100%) of The Hip Society responded to the THA complications survey. Initially, 21 THA complications were proposed. The validation process reduced the 21 proposed complications to 19 THA complications with definitions and stratification that were endorsed by The Hip Society (bleeding, wound complication, thromboembolic disease, neural deficit, vascular injury, dislocation/instability, periprosthetic fracture, abductor muscle disruption, deep periprosthetic joint infection, heterotopic ossification, bearing surface wear, osteolysis, implant loosening, cup-liner dissociation, implant fracture, reoperation, revision, readmission, death). CONCLUSIONS: Acceptance and use of these standardized, stratified, and validated THA complications and adverse events could advance reporting of outcomes of THA and improve assessment of THA by clinical investigators. LEVEL OF EVIDENCE: Level V, therapeutic study.

Early Results of Medicare's Bundled Payment Initiative for a 90-Day Total Joint Arthroplasty Episode of Care.

BACKGROUND: In 2011 Medicare initiated a Bundled Payment for Care Improvement (BPCI) program with the goal of introducing a payment model that would "lead to higher quality, more coordinated care at a lower cost to Medicare." METHODS: A Model 2 bundled payment initiative for Total Joint Replacement (TJR) was implemented at a large, tertiary, urban academic medical center. The episode of care includes all costs through 90 days following discharge. After one year, data on 721 Medicare primary TJR patients were available for analysis. RESULTS: Average length of stay (LOS) was decreased from 4.27 days to 3.58 days (Median LOS 3 days). Discharges to inpatient facilities decreased from 71% to 44%. Readmissions occurred in 80 patients (11%), which is slightly lower than before implementation. The hospital has seen cost reduction in the inpatient component over baseline. CONCLUSION: Early results from the implementation of a Medicare BPCI Model 2 primary TJR program at this medical center demonstrate cost-savings. LEVEL OF EVIDENCE: IV economic and decision analyses-developing an economic or decision model.

Local and systemic alterations in signal transducers and activators of transcription (STAT) associated with human abdominal aortic aneurysms.

BACKGROUND: Signal transducers and activators of transcription (STAT) proteins are transcription factors that, when activated by phosphorylation, regulate gene expression and cellular activity. The aim of this study was to evaluate the local and systemic expression and activation of STAT proteins associated with abdominal aortic aneurysms (AAA). METHODS: Expression and activation of STAT proteins were assessed in aortic wall samples obtained from patients undergoing repair of AAA (n = 9) and from non-aneurysmal (NA) donors (n = 17). Aortic samples were evaluated for mRNA and protein expression for STAT1, 2, 3, 4, 5a, and 5b using RT-PCR and immunoblot (WB) assays and normalized to ß-actin (expressed as arbitrary units). STAT activation was assessed with WB assays using phosphorylated (p)-STAT-specific antibodies. Alterations in STAT activation were calculated by normalizing pSTAT proteins to corresponding total STAT levels. Immunohistochemistry was performed on AAA and NA samples using the total and pSTAT antibodies. Systemic alterations in STAT activation were assessed by evaluating circulating leukocytes for the presence of pSTAT from patients with AAA (AAA, n = 8), repaired aneurysm (RA, n = 8), or age/gender matched controls with no AAA (CT, n = 8). Flow cytometry was performed to assess for circulating levels of STAT1 (pY701), STAT3 (pY705), and STAT5a (pY694) in monocytes, granulocytes, and lymphocytes. Assessments were made at baseline and in response to in vitro stimulation with IFN-γ (50 ng/mL) or IL-6 (100 ng/mL). Results were analyzed using Student's t-test and are expressed as mean ± SEM. RESULTS: In AAA tissue compared with NA, STAT-1 (1.08 ± 0.09 versus 0.62 ± 0.07), -2 (0.98 ± 0.07 versus 0.55 ± 0.08), and -4 (0.89 ± 0.12 versus 0.35 ± 0.11) mRNA levels were elevated (P < 0.01, all). Corresponding increases in STAT protein were only observed for STAT1 (2.77 ± 0.93 versus 0.93 ± 0.08, P < 0.05). Increases in activation were observed in AAA compared with NA in pSTAT2 (0.77 ± 0.1 versus 0.1 ± 0.02, P < 0.01), pSTAT3 (1.6 ± 0.3 versus 0.2 ± 0.06, P < 0.02) and pSTAT5 (0.57 ± 0.03 versus 0.2 ± 0.03, P < 0.05) levels. Phosphorylated STAT1, 2, 3, and 5 were observed in inflammatory cells invading the AAA adventitia. In addition, STAT3 was observed in the media of AAA and NA, but pSTAT3 was only observed in the media of AAA. There were no differences in baseline levels of pSTAT-positive circulating leukocytes. IFN-γ stimulation decreased STAT-5a (pY694)-positive CT lymphocytes to 40% ± 13% of baseline, but had no effect on AAA or RA lymphocytes (116% ± 35%, 102% ± 19%, respectively; P = 0.01). STAT-5a (pY694)-positive CT granulocytes also decreased to 62% ± 18% of baseline compared with AAA or RA granulocytes (122% ± 25%, 126% ± 17%, respectively; P = 0.01). Alterations in STAT1 (pY701) and STAT3 (pY705) were not observed in leukocytes following cytokine stimulation. CONCLUSIONS: STAT proteins are important regulators of transcriptional activity and have been linked to cardiovascular disease. The present data suggest that altered levels of phosphorylated STATs are associated with AAA. Understanding their role may provide further insight into the mechanisms of AAA formation and allow for the development of medical treatment options.