Effects of Intrathecal Morphine Administration in Patients Undergoing Primary Total Hip Arthroplasty Under Spinal Anesthesia With Quadratus Lumborum Block for Postoperative Analgesia.

Introduction Quadratus lumborum (QL) block has previously been shown to provide improved analgesia in patients undergoing primary total hip arthroplasty (THA) under spinal anesthesia when compared to spinal anesthesia alone. Additionally, recent studies have shown the addition of intrathecal morphine (ITM) to provide superior postoperative analgesia in patients undergoing various surgical interventions including total knee arthroplasty under spinal anesthesia with peripheral nerve blockade. At this time, however, there has not been a study evaluating the effects of intrathecal morphine in patients undergoing THA under spinal anesthesia with QL block. This study aims to assess if the addition of intrathecal morphine can provide adequate or even superior postoperative analgesia in patients undergoing primary THA. Methods This retrospective study included 26 patients in the spinal/QL block/intrathecal morphine (SA+QLB+ITM) group, 31 patients in the spinal/QL block group (SA+QLB), and 28 patients in the spinal only (SA or control) group. Twenty-six patients undergoing primary THA under a combination of spinal anesthesia and peripheral nerve blockade (quadratus lumborum block) were given a dose of 100 mcg of intrathecal morphine. Various parameters were evaluated including Post-Anesthesia Care Unit (PACU) and 24-hour visual analog scale (VAS) scores, time to first opioid use, 24- and 48-hour total opioid use as oral morphine equivalents (OME), 24-hour ambulation distance, and time from block placement to hospital discharge. The results were analyzed and compared to patients undergoing primary THA under spinal anesthesia with QL block (no intrathecal morphine) and compared to a control group of patients undergoing primary THA under spinal anesthesia only. Results The study analysis included 26 patients in the SA+QLB+ITM group, 31 patients in the SA+QLB group, and 28 patients in the SA (control) group. When compared with the control group, the SA+QLB+ITM had lower 24-hour total opioid usage (mean difference 20.80 OME, CI 6.454 to 35.15, p-value 0.0025), longer time to 1st opioid use (mean difference -20.51 hours later, p-value .0052), lower 24-hr VAS (difference 2.421, p-value 0.0012, CI 0.8559 to 3.987), and faster time to discharge (16.00 hr earlier, p-value 0.0459). When compared to the SA+QLB group, the SA+QLB+ITM group only showed a statistically significant difference in faster time to discharge (19.46 hr earlier, p-value 0.0068). However, while there was no statistically significant difference in time to 1st opioid use between the control and SA+QLB group, the difference did become significant when comparing the control to the SA+QLB+ITM group (mean difference -20.51 hours later (p-value .0052). There was no significant difference in either of the three groups in ambulation distance at 24 hours, PACU VAS, or 48-hour total opioid use. Conclusion Our study concludes that the addition of 100 mcg ITM for total hip arthroplasty under spinal anesthesia improved postoperative analgesia compared to the control group. Also, the ITM group did better with respect to delay in first opioid use and decreased hospital stay compared to the control and block-only groups. Our study warrants no more concerns of PONV, pruritus, or respiratory depression with this dose of ITM and requires standard postoperative care.

The Dose Comparison of Intrathecal Morphine for Postoperative Analgesia in Total Knee Arthroplasty Under Spinal Anesthesia: A Single Institute Retrospective Study.

Background and purpose of the study Intrathecal morphine (ITM) provides effective postoperative analgesia in patients undergoing total knee arthroplasty (TKA) under spinal anesthesia. However, the ideal dose at which maximal analgesic effects can be delivered with minimal side effects is not clearly known. This retrospective study is aimed to compare two different doses of ITM with respect to analgesia benefits and side effects. Methods This is a retrospective, descriptive, single-center study approved by the Institutional Review Board (IRB) at the University of Alabama at Birmingham. Three patient groups were selected: a control group receiving continuous adductor canal block (CCACB) under spinal anesthesia, and two experimental groups receiving single-dose adductor canal block (SSACB) under spinal anesthesia with either 100 mcg or 150 mcg of ITM. The sample size included 75 patients (25 per group) who were 18 years and older, American Society of Anesthesiology (ASA) class 1-3 who were undergoing primary TKA. Patients with chronic pain or opioid use exceeding 30 days and those undergoing surgeries other than primary TKA were excluded. Outcome data, including opioid use (from which post-operative oral morphine equivalents (OME) were calculated), antiemetic use, visual analog pain scale (VAS) scores, distance ambulated at 24 hours, and length of hospital stay, were extracted by chart review. Results In the post-anesthesia care unit (PACU), patients in both ITM groups experienced significantly lower opioid consumption and pain scores compared to the control group (p<.001). Furthermore, cumulative OME at 24 hours was significantly less in the ITM groups compared to the control, but there was no difference between ITM doses (p=0.004; mean cumulative OME for control was 77.2 OME vs 43.4 OME for 100 mcg ITM vs 42.6 OME for 150 mcg ITM). Antiemetic usage did not increase in the ITM groups. Although there was no statistically significant difference in ambulation at 24 hours, both ITM groups exhibited a trend toward greater average ambulation distance compared to the control group (p=0.095; mean distance walked for control was 67.6 feet, 76.6 feet for 100 mcg ITM vs 98.8 feet for 150 mcg ITM). Hospital length of stay did not significantly differ between the groups. Conclusion ITM doses of 100 mcg and 150 mcg provide effective analgesia for patients undergoing lower extremity total knee arthroplasty under spinal anesthesia. Patients receiving ITM had better pain scores in the immediate post-operative period and had overall less oral morphine equivalent consumption when compared to control. In addition, the safety and side effect profile for ITM is similar for both doses as there was no incidence of respiratory depression and antiemetic usage did not differ between all study arms. Future studies should explore the use of higher ITM doses and consider a broader patient population to further understand the advantages and potential drawbacks of ITM in TKA surgery.

Intrathecal Morphine Use Improves Postoperative Analgesia and Reduces Opioid Consumption in Patients Undergoing Total Knee Arthroplasty Under Spinal Anesthesia: A Retrospective Study.

Background Intrathecal morphine (ITM) provides effective postoperative analgesia for patients undergoing total knee arthroplasty (TKA) under spinal anesthesia (SA). The management of pain in patients undergoing TKA has remained a challenge for anesthesiologists, as no single regional anesthesia technique is adequate with regard to balancing effective analgesia with minimal side effects. Severe postoperative pain following TKA has been shown to negatively impact patient outcomes and mortality. This study is aimed to describe the effect of intrathecal morphine in patients undergoing total knee arthroplasty. Methods This was a retrospective, descriptive, and single-center study conducted on patients undergoing total knee arthroplasty from June 1, 2022, to June 1, 2023. The sample size consisted of 50 patients who were 18 years and older, American Society of Anesthesiology (ASA) class 1-3, and patients who had received either 150 mcg (experimental) or no ITM dose under spinal anesthesia. Oral morphine requirement (OME) and visual analog pain scale (VAS) were used to assess pain in the first 24 hours after surgery. Results The experimental group had significantly lower OME usage in the post-anesthesia care unit (PACU) (p < 0.001) and at six hours (p = 0.040) postoperatively. At 12 hours and 24 hours postoperatively, the two groups had similar OME use (p > 0.20, for both). The experimental group had significantly less total OME use over the first 24-hour postoperative period. The experimental group had significantly lower pain scores in the PACU (p < 0.001) and at six hours postop (p = 0.002); there were no significant differences between groups at 12- and 24-hours postop. The ambulation distance was clinically significant and better in the ITM group but was not statistically significant (p = 0.080). There was no difference between groups in the incidence of postoperative nausea and vomiting (PONV). Conclusion The careful use of ITM with the optimal dose offers an effective addition to regional anesthesia for improved analgesia with minimal side effects. The 150 mcg ITM dose provided good analgesic effects with longer duration and was not associated with respiratory depression.

Comparison of Pericapsular Nerve Group (PENG) Block Versus Quadratus Lumborum (QL) Block for Analgesia After Primary Total Hip Arthroplasty Under Spinal Anesthesia: A Retrospective Study.

BACKGROUND: Total hip arthroplasty (THA) is one of the most common operative procedures performed. Controlling postoperative pain following THA remains a challenge due to the complex innervation of the hip joint and the recent desire to preserve motor function following nerve blockade. Several nerve block techniques have been used for THA in the past, but the quadratus lumborum (QL) block and the blockade of the pericapsular nerve group (PENG) have emerged as opiate-sparing regional anesthesia techniques that preserve motor function. To date, little data comparing the two block techniques exists. The purpose of our study was to compare outcomes following these techniques in patients undergoing primary THA. MATERIALS AND METHODS: This retrospective analysis utilized data from three distinct groups who underwent primary THA at our institution: 45 patients who received PENG block, 38 patients who received QL block, and 77 control patients. Chart review analysis was performed by authorized personnel to obtain cumulative oral morphine equivalent (OME) data at 24 and 48 hours postoperatively (primary outcomes). In addition, visual analog pain scale (VAS) scores in the post-anesthesia care unit (PACU) and at 12, 24, and 48 hours, ambulation distance, and length of hospital stay data were obtained (secondary outcomes). Group comparisons were conducted using either analysis of variance (ANOVA) with Tukey's multiple comparison test for parametric data or Krustal-Wallis with Dunn's multiple comparison tests for nonparametric endpoints. RESULTS: This study found a statistically significant difference in cumulative OME usage across all groups at 24 and 48 hours. Significant difference in OMEs was found between QL and control and PENG and control; however, no difference was found in OMEs between PENG and QL groups at either time point. There was a statistically significant difference in VAS scores in the PACU across all groups; QL showed significantly lower VAS scores in the PACU compared to PENG and control, while PENG only showed significantly lower VAS scores compared to control. There was a statistically significant difference in VAS scores at 24 hours across all groups; however, only QL showed significantly lower VAS scores compared to control at 24 hours. QL was associated with a statistically significant increase in the length of hospital stay compared to PENG. CONCLUSION: This study showed no difference between OME usage in patients who received PENG or QL nerve blocks for primary THA. VAS scores were similar between groups with the exception of QL outperforming PENG in the PACU. Optimizing postoperative pain via multi-approach strategies should remain a priority for patients undergoing THA. Future research is warranted in order to provide guidance on best practice for these patients.

Association Between COVID-19 and Mortality in Hip Fracture Surgery in the National COVID Cohort Collaborative (N3C): A Retrospective Cohort Study.

BACKGROUND: This study investigated the outcomes of coronavirus disease (COVID-19)-positive patients undergoing hip fracture surgery using a national database. METHODS: This is a retrospective cohort study comparing hip fracture surgery outcomes between COVID-19 positive and negative matched cohorts from 46 sites in the United States. Patients aged 65 and older with hip fracture surgery between March 15 and December 31, 2020, were included. The main outcomes were 30-day all-cause mortality and all-cause mortality. RESULTS: In this national study that included 3303 adults with hip fracture surgery, the 30-day mortality was 14.6% with COVID-19-positive versus 3.8% in COVID-19-negative, a notable difference. The all-cause mortality for hip fracture surgery was 27.0% in the COVID-19-positive group during the study period. DICUSSION: We found higher incidence of all-cause mortality in patients with versus without diagnosis of COVID-19 after undergoing hip fracture surgery. The mortality in hip fracture surgery in this national analysis was lower than other local and regional reports. The medical community can use this information to guide the management of hip fracture patients with a diagnosis of COVID-19.

Systemic Complications of Obesity in Operative Acetabular Fractures.

OBJECTIVE: To determine the effect of obesity on rates of systemic complications in operatively treated acetabular fractures. DESIGN: Retrospective Case-Control study. SETTING: Level 1 Trauma Center. PATIENTS/PARTICIPANTS: All patients with acetabular fractures managed operatively from January 2015 to December 2019. Patients were divided into groups based on their body mass index (BMI) (normal weight = BMI <25 kg/m2, overweight = BMI 25-30, obese = BMI 30-40, and morbidly obese = BMI >40). INTERVENTION: Operative management of an acetabular fracture. MAIN OUTCOME MEASUREMENT: Systemic complications, including mortality, sepsis, pneumonia, acute respiratory distress syndrome, deep vein thrombosis, pulmonary embolism, or venous thrombotic event. RESULTS: A total of 428 patients were identified. One hundred nine patients (25.4%) were in normal weight, 133 (31.1%) were overweight, 133 (31.1%) were obese, and 53 (12.4%) were morbidly obese. The rate of systemic complications was 17.5%, and overall mortality rate was 0.005%. There were no significant differences between the different BMI groups in all-cause complications or any individual complications. When the morbidly obese group was compared with all other patients, there were also no significant differences in all-cause complications or any individual complications. CONCLUSION: In conclusion, in this study, there was no association with increasing BMI and inpatient systemic complications after operative management of acetabular fractures. As we continue to refine our understanding of how obesity affects outcomes after acetabular fracture surgery, other indices of obesity might prove more useful in predicting complications. In the obese population, there are well-documented risks of postoperative infections and challenges in obtaining an anatomic reduction, but the fear of postoperative systemic complications should not deter surgeons from undertaking operative management of acetabular fractures in the obese population. Because the prevalence of obesity in trauma patients continues to increase, it is incumbent on us to continue to improve our understanding of optimal treatment for our patients. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

COVID-19 and Acute Cervical Spinal Cord Injury-Case Report of 2 Patients: Do We Need to Rethink Our Standard Treatment Strategy?

STUDY DESIGN: This was a case series. OBJECTIVE: The authors sought to examine the high-risk population of COVID-positive patients with acute cervical spinal cord injury (SCI) in a large level 1 trauma and tertiary referral center. SUMMARY OF BACKGROUND DATA: There are limited studies regarding the surgical management of patients with acute SCI in the setting of the recent coronavirus pandemic. METHODS: The authors describe the cases of 2 patients who died from COVID-related complications after acute cervical SCI. RESULTS: Patients with SCI are at increased risk of pulmonary complications. COVID-19 infection represents a double hit in this patient population, increasing potential morbidity and mortality in the perioperative time frame. Careful consideration must be made regarding the timing of potential surgical intervention in the treatment of acute SCI. CONCLUSIONS: Nationwide database of COVID-positive patients with acute spinal cord injury should be collected and analyzed to better understand how to manage acute SCI in the COVID-19 era. The authors recommend preoperative discussion in patients with acute cervical SCI with COVID-19, specifically emphasizing the increased risk of respiratory complications and mortality.

Comparison Between the Direct Anterior and Posterior Approaches for Total Hip Arthroplasty Performed for Femoral Neck Fracture.

OBJECTIVES: To compare 90-day and 1-year outcomes, including mortality, of femoral neck fracture patients undergoing total hip arthroplasty (THA) by direct anterior approach (DAA) versus posterior approach (PA). DESIGN: Retrospective cohort. SETTING: Level I Trauma Center. PATIENTS: One hundred forty-three consecutive intracapsular femoral neck fractures treated with THA from 2010 to 2018. The minimum follow-up was 12 months, and the average follow-up was 14.6 months (12-72 months). MAIN OUTCOME MEASURES: Postoperative outcomes, including discharge ambulation, dislocation, periprosthetic joint infection, revision THA, and mortality at 90 days and 1 year after THA. RESULTS: Of the 143 THA included, 44 (30.7%) were performed by DAA while 99 (69.3%) were performed by PA. In-hospital outcomes were similar between the cohorts. Compared with DAA patients, PA patients were more likely to ambulate without assistance preinjury (88.9% vs. 72.7%, P = 0.025) and be nonambulatory at the time of discharge (27.3% vs. 11.4%, P = 0.049). There were no significant differences in 90-day and 1-year postoperative outcomes between the DAA and PA groups, including dislocation, periprosthetic joint infection, periprosthetic fracture, mechanical complications, and revision surgery. Although there was no difference in mortality rate at 90 days, at 1-year follow-up the mortality rate was lower in the DAA group (0% vs. 11.1%, P = 0.018). CONCLUSIONS: Performing THA by DAA provides similar benefits in regards to medical and surgical outcomes compared with the PA for displaced femoral neck fracture. However, the DAA may lead to decreased 1-year mortality rates, possibly, because of improved early ambulation capacity that is an important predictor of long-term mortality. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Calcium pyrophosphate deposition disease of the cervical and thoracolumbar spine: A report of two cases.

Background: Spinal calcium pyrophosphate deposition disease (CPPD) is uncommon, and often resembles more common spine pathologies causing pain and neural compression. Here, we present two unusual cases of CPPD of the cervical and thoracolumbar spines. Case description: Case 1: A 71-year old female smoker presented with a large epidural mass causing rapidly progressive cervical myelopathy with weakness in the upper and lower extremities.Case 2: A 66-year-old morbidly obese male presented with chronic back pain for several years associated with progressively worsening radicular pain in his left lower extremity. Outcome: The first case is an example of tumoral CPPD involving the facet joint and expanding into the epidural space. The second case was an example of CPPD involving a thoracolumbar facet cyst, resulting in unilateral radiculopathy. Both patients were treated surgically and had significant improvement in symptoms post-operatively. Conclusions: CPPD in the spine is an uncommon diagnosis but should be considered in the differential diagnosis of patients presenting with back pain and associated neurological symptoms. Accurate diagnosis of spinal CPPD is important in that it will guide postoperative management with anti-inflammatory medications and reduce risk of recurrence.

Optimization of Orthopedic Surgical Instrument Trays: Lean Principles to Reduce Fixed Operating Room Expenses.

BACKGROUND: Optimization of surgical instrument trays improves efficiency and reduces cost. The purpose of this study is to assess the economic impact of optimizing orthopedic instrument trays at a tertiary medical center. METHODS: Twenty-three independent orthopedic surgical instrument trays at a single academic hospital were reviewed from 2017 to 2018. Using Lean methodology, surgeons agreed upon the fewest number of instruments needed for each of the procedure trays. Instrument usage counts, cleaning times, room turnover times, tray weight, holes in tray wrapping, wet trays, and time invested to optimize each tray were tracked. Cost savings were calculated. Student's t-test was used to determine statistical significance, with P < .05 considered significant. RESULTS: The mean instrument usage before and after Lean optimization was 23.4% and 54.2% (P < .0001). By Lean methods, 433 of 792 instruments (55%) were removed from 11 unique instrument trays (102 total trays), resulting in a reduction of 3520 instruments. Total weight reduction was 574.3 pounds (22%), ranging from 2.1-16.2 pounds per tray. The number of trays with wrapping holes decreased from 13 to 1 (P < .0001). The process of examining and removing instruments took an average of 7 minutes 35 seconds per tray. The calculated total annual savings was $270,976 (20% overall cost reduction). CONCLUSION: In addition to substantial cost savings, tray optimization decreases tray weights and cleaning times without negatively impacting turnover times. Lean methodology improves efficiency in instrument tray usage, and reduces hospital cost while encouraging surgeon and staff participation through continuous process improvement. LEVEL OF EVIDENCE: Economic Quality Improvement, Level III.

Does Surgeon Fellowship Training Influence Outcomes in Hemiarthroplasty for Femoral Neck Fracture?

BACKGROUND: The aim of this study is to compare the outcomes (90 days and 1 year) of patients with femoral neck fracture undergoing hemiarthroplasty by surgeons with different fellowship training: trauma, arthroplasty, and general orthopedics. METHODS: This study is a retrospective review of consecutive patients undergoing hip hemiarthroplasty for femoral neck fracture from 2010 to 2018. Comorbidities, perioperative details, demographics, injury variables, and time-to-surgery were compared between the fellowship training cohorts, in addition to outcomes including dislocation, periprosthetic joint infection, and mortality at 90 days and 1 year. RESULTS: A total of 298 hips with an average age of 77.8 years underwent hemiarthroplasty for femoral neck fracture. Arthroplasty surgeons had a significantly shorter operative duration (82 minutes, P = .0014) and utilized the anterior approach more frequently (P < .0001). The general orthopedists had a significantly increased total surgical complication risk compared to both the arthroplasty and trauma fellowship-trained cohorts at both 90 days (11.8% vs 1.6% vs 3.9%, P = .015) and 1 year (18.2% vs 4.9% vs 7.1%, P = .008). The overall mortality risk was 11.7% at 90 days and 22.8% at 1 year. When adjusted for covariates, including comorbidities, gender, age, and preoperative walking capacity, both the arthroplasty fellowship-trained cohort (odds ratio 0.381, 95% confidence interval 0.159-0.912, P = .030) and the general orthopedist cohort (odds ratio 0.495; 95% confidence interval 0.258-0.952, P = .035) had reduced risk of 1-year mortality compared to the trauma fellowship-trained cohort. CONCLUSION: Hemiarthroplasty performed for femoral neck fractures may result in fewer complications when performed by arthroplasty fellowship-trained surgeons. An arthroplasty weekly on-call schedule and adjusted institutional protocols may be utilized to improve outcomes and reduce complications. LEVEL OF EVIDENCE: Level II, retrospective cohort.

Efficacy of Intraoperative Antiseptic Techniques in the Prevention of Periprosthetic Joint Infection: Superiority of Betadine.

BACKGROUND: Povidone-iodine (PI), chlorhexidine gluconate (CHG), and vancomycin (VANC) powder are common intrawound prophylactic agents to prevent periprosthetic joint infection during primary total joint arthroplasty. The aims of this study are (1) to determine the minimal inhibitory concentration (MIC) and time to death for PI, CHG, and VANC against multiple bacteria and (2) to determine time to death against bacteria dried on titanium discs. METHODS: A standard quantitative suspension assay was performed to determine the MIC for PI, CHG, and VANC against methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus epidermidis, Haemophilus influenzae, Pseudomonas aeruginosa, Burkholderia cepacia, and Escherichia coli. Time to death assay was performed with time points of 0, 3, 30, and 60 minutes. Concentrations of antiseptic agents for time to death assay were 1% PI, 0.05% CHG, and 5 µg/mL VANC. Dry-phase bacteria on titanium discs were treated in a similar fashion. RESULTS: The MIC of PI was 0.63%, CHG was 0.0031%, and VANC was 1.56 µg/mL. All 7 bacterial isolates were completely killed by PI at all times tested. CHG failed to kill MRSA and B cepacia at 0- and 3-minute exposures. Vancomycin completely killed MRSA and S epidermidis isolates between 18-20 hours of exposure. All bacterial isolates dried on titanium discs were eliminated by PI exposure on contact. E coli and S epidermidis were incompletely eliminated by CHG at 0 minutes, with all isolates eliminated at 3, 10, and 30 minutes. CONCLUSION: Our study suggests that PI kills all bacteria tested immediately on contact and that the exposure time is not the key factor.

A prospective study of platelet function in trauma patients.

BACKGROUND: Exsanguination associated with acute traumatic coagulopathy is a leading cause of death following injury. While platelets occupy a pivotal role in clot formation, clinical research has been scant because of complexities resulting from the need for rapid handling and complex testing of platelet functions. While the thrombin pathway has been proposed as a mediator of platelet dysfunction in trauma, it has not been systematically investigated. The purpose of this study was to evaluate the thrombin pathway in platelet dysfunction. METHODS: Forty trauma patients and 20 noninjured controls were enrolled in the study at a Level I trauma center. Platelet aggregation was tested by light transmission aggregometry with two agonists, adenosine diphosphate (ADP) and thrombin receptor agonist peptide (TRAP). Mean fluorescence intensity and percent positivity of CD62 on ADP-activated platelets were evaluated using flow cytometry. Enzyme-linked immunosorbent assays were performed to evaluate the concentrations of D-dimer, thrombin-antithrombin complex (TAT), and prothrombin fragment 1 + 2 (PF 1 + 2) in each sample. RESULTS: Compared with healthy controls, trauma patients had significantly decreased ADP- and TRAP-mediated platelet aggregation and ADP-mediated CD62 expression. In trauma patients, TRAP-mediated aggregation was inversely proportional to head Abbreviated Injury Scale (AIS) score. Glasgow Coma Scale (GCS) score was directly proportional to TRAP- and ADP-mediated aggregation. When compared with controls, significant differences of D-dimer, TAT, and PF 1 + 2 were found. Measures of shock, including admission blood pressure, pulse, base deficit, and lactate level, did not correlate with platelet dysfunction. CONCLUSION: Trauma patients have significantly lower levels of platelet activation and aggregation compared with healthy controls. Severity of head injury was significantly correlated with platelet dysfunction in a stepwise fashion. Trauma patients also have significantly increased levels of D-dimer, TAT, and PF 1 + 2 when compared with healthy controls. Our data suggest that the thrombin receptor pathway plays an important role in platelet dysfunction in trauma. LEVEL OF EVIDENCE: Prognostic and epidemiologic study, level III.

Tetraspanin CD9 regulates cell contraction and actin arrangement via RhoA in human vascular smooth muscle cells.

The most prevalent cardiovascular diseases arise from alterations in vascular smooth muscle cell (VSMC) morphology and function. Tetraspanin CD9 has been previously implicated in regulating vascular pathologies; however, insight into how CD9 may regulate adverse VSMC phenotypes has not been provided. We utilized a human model of aortic smooth muscle cells to understand the consequences of CD9 deficiency on VSMC phenotypes. Upon knocking down CD9, the cells developed an abnormally small and rounded morphology. We determined that this morphological change was due to a lack of typical parallel actin arrangement. We also found similar total RhoA but decreased GTP-bound (active) RhoA levels in CD9 deficient cells. As a result, cells lacking a full complement of CD9 were less contractile than their control treated counterparts. Upon restoration of RhoA activity in the CD9 deficient cells, the phenotype was reversed and cell contraction was restored. Conversely, inhibition of RhoA activity in the control cells mimicked the CD9-deficient cell phenotype. Thus, alteration in CD9 expression was sufficient to profoundly disrupt cellular actin arrangement and endogenous cell contraction by interfering with RhoA signaling. This study provides insight into how CD9 may regulate previously described vascular smooth muscle cell pathophysiology.

Pro-MMP-9 upregulation in HT1080 cells expressing CD9 is regulated by epidermal growth factor receptor.

Degradation of the surrounding extracellular matrix (ECM) by matrix metalloproteinases (MMPs) drives invasion and metastasis of cancer cells. We previously demonstrated that tetraspanin CD9 expression upregulates pro-MMP-9 expression and release and promotes cellular invasion in a human fibrosarcoma cell line (HT1080). These events were dependent upon the highly functional second extracellular loop of CD9. We report here that the epidermal growth factor receptor (EGFR) tyrosine kinase expression and activity are involved in the CD9-mediated increase in pro-MMP-9 release and cellular invasion. Pro-MMP-9 expression was significantly decreased in a dose-dependent manner using first a broad spectrum receptor tyrosine kinase inhibitor and multiple specific EGFR inhibitors in CD9-HT1080 cells. Furthermore, gefitinib treatment of CD9-HT1080 cells reduced invasion through matrigel. EGFR knockdown using short interfering RNA resulted in decreased pro-MMP-9 expression and release into the media and subsequent cellular invasion without affecting CD9 expression or localization. Conclusively, this study points to EGFR as a key mediator between CD9-mediated pro-MMP-9 release and cellular invasion of HT1080 cells.