Embolization for pediatric trauma.

BACKGROUND: The management of pediatric trauma with trans-arterial embolization is uncommon, even in level 1 trauma centers; hence, there is a dearth of literature on this subject compared to the adult experience. OBJECTIVE: To describe a single-center, level 1 trauma center experience with arterial embolization for pediatric trauma. MATERIALS AND METHODS: A retrospective review was performed to identify demographics, transfusion requirements, pre-procedure imaging, procedural details, adverse events, and arterial embolization outcomes over a 19-year period. Twenty children (age 4.5 months to 17 years, median 13.5 years; weight 3.6 to 108 kg, median 53 kg) were included. Technical success was defined as angiographic resolution of the bleeding-related abnormality on post-embolization angiography or successful empiric embolization in the absence of an angiographic finding. Clinical success was defined as not requiring additional intervention after embolization. RESULTS: Seventy-five percent (n=15/20) of patients required red blood cell transfusions prior to embolization with a mean volume replacement 64 ml/kg (range 12-166 ml/kg) and the median time from injury to intervention was 3 days (range 0-16 days). Technical success was achieved in 100% (20/20) of children while clinical success was achieved in 80% (n=16/20). For the 4 children (20%) with continued bleeding following initial embolization, 2 underwent repeat embolization, 1 underwent surgery, and 1 underwent repeat embolization and surgery. Mortality prior to discharge was 15% (n=3). A post-embolization mild adverse event included one groin hematoma, while a severe adverse event included one common iliac artery pseudoaneurysm requiring open surgical ligation. CONCLUSIONS: In this single-center experience, arterial embolization for hemorrhage control in children after trauma is feasible but can be challenging and the clinical failure rate of 20% in this series reflects this complexity. Standardization of pre-embolization trauma assessment parameters and embolic techniques may improve outcomes.

Percutaneous Nephrostomy in Neonates and Young Infants.

PURPOSE: To describe a single-center experience of placing percutaneous nephrostomy (PCN) tubes in neonates and young infants aged ≤3 months. MATERIALS AND METHODS: This retrospective study evaluated PCN placement during a 19-year period. Medical records were reviewed for patient demographics, indications, procedure details, catheter-related adverse events, and outcomes. A total of 45 primary PCN insertions were attempted in 29 children (median age, 11 days [range, first day of life to 3 months]; median weight, 3.5 kg [range, 1.4-7.0 kg]). Salvage procedures resulted in 13 secondary catheters in 6 children. The most common indication was ureteropelvic junction obstruction (40.0%), and the most common urinary tract dilation classification was P3 (88.9%). RESULTS: Technical success for primary placements was 95.6%; both technical failures were due to loss of access in the same patient. Of primary placements, 76.7% were electively removed, 6.9% were dislodged but not replaced, and the remaining 16.3% required salvage procedures. Mechanical adverse events occurred in 20.9% of primary and 53.8% of secondary catheters, including partial retraction, complete dislodgement, and occlusion. Urinary tract infections (UTIs) occurred in 18.6% of primary and 15.4% of secondary catheters. Urosepsis occurred in 2.3% of primary and 7.7% of secondary catheters. Median primary catheter dwell time was 41 days (range, 1-182 days) and median secondary catheter dwell time was 31 days (range, 10-107 days). CONCLUSION: PCN placement in neonates and young infants has a high technical success rate, although not without particular procedural and management challenges of catheter malfunction and UTI.

Novel method to biopsy aneurysmal bone cysts in children.

PURPOSE: The thin and friable septations composing aneurysmal bone cysts (ABC) may be challenging to target for percutaneous biopsy. The purpose of this study was to describe and evaluate a novel method of ABC biopsy using endomyocardial biopsy forceps as an attempt to capture larger fragments of tissue for diagnosis. METHODS AND MATERIALS: This was a retrospective study performed over a 17-year period. Patients <18 years old who underwent percutaneous biopsy for a presumed ABC, based on pre-procedure imaging, were included. Medical records were reviewed to identify age, sex, lesion location, biopsy procedure details, complications, and pathology results. A diagnostic biopsy was defined as conclusive histologic confirmation. Inconclusive findings or findings suggestive of but not diagnostic of an ABC were treated as non-diagnostic, even if imaging and clinical findings were characteristic. Biopsy device selection and quantity of tissue obtained was at the discretion of the pediatric interventional radiologist. Fisher's exact test was used to compare the diagnostic yield of standard biopsies to those employing biopsy forceps. RESULTS: Twenty-three biopsies were performed in 18 patients (11 female) with a median age of 14.7 years (IQR 10.6-15.6). Lesions were located in the extremities (7, 30.4%), chest (6, 26.1%), pelvis (5, 21.7%), spine (4, 17.4%), and mandible (1, 4.3%). Specimens were obtained using a 13- or 15-gauge bone coring needle (11, 47.8%); 14-, 16-, or 18-gauge soft tissue needle (6, 26.1%); or a combination of bone and soft tissue (4, 17.4%) needles. Endomyocardial biopsy forceps were utilized in 7 cases (30.4%), 2 in which it was the only device used. Overall, a conclusive pathologic diagnosis was made in 13/23 (56.5%) biopsies. Of the diagnostic biopsies, 1 was a unicameral bone cyst and all others were ABCs. No malignancy was identified. Compared to the standard approach, the use of forceps was more likely to result in a diagnostic biopsy (40.0% vs 100.0%, p = 0.008). There were no complications. CONCLUSIONS: Endomyocardial biopsy forceps offer an additional, novel technique to biopsy presumed ABCs and may improve diagnostic yield.

Central venous access in children: Placement trends over the last decade.

PURPOSE: To evaluate central venous access placement trends for radiology and non-radiology services over the last decade. MATERIALS AND METHODS: Children who had central venous access procedures included in a large administrative database of 49 pediatric institutions in the United States between 2010 and 2020 were included. Patient demographics and patient specific factors were compared between groups. The percentage of procedures performed by interventional radiology (IR) and non-radiology services were compared over time and by region. RESULTS: A total of 483,181 vascular access encounters were recorded (45.3% female; median age 2 years (IQR 0-11 years)). Approximately one quarter of vascular access encounters were IR-led, with a slight increase of 3.8% between 2010 and 2020. Children who underwent IR-placed vascular access were older (median age of 4 years compared to 1 year in non-radiology encounters). Interventional radiology-placed access was greatest in the Midwest (33.5%) with a decrease of 5.9% over the study period; in the other three regions, IR-performed encounters increased. Patient comorbidities more prevalent in the IR encounters were technology dependence (42.4% of all radiology encounters), gastrointestinal (34.9%), respiratory (20.8%), and transplant (8.1%), while those which were more prevalent in the non-radiology encounters were nephrology/urology (21.4% of all non-radiology encounters), prematurity/neonatal (17.3%), and malignancy (17.3%). CONCLUSIONS: Interventional radiology-provided vascular access services have slightly increased over the last decade without significant service-line transfer to other specialties. Underlying comorbidities in IR-led vascular access encounters vary across institutions based on referral patterns, possibly reflecting the adoption of ultrasound guidance by other pediatric subspecialties.

Adjunctive techniques for percutaneous enteral access in children: a pictorial review.

Primary percutaneous gastrostomy and gastrojejunostomy tube placements are fundamental procedures performed in pediatric interventional radiology, with both antegrade and retrograde techniques described. In pediatric patients, however, challenges may arise due to smaller patient size and anatomical variations. Several adjunctive techniques may facilitate safe percutaneous access in the setting of a limited percutaneous gastric access window. These include the intra-procedural use of cone beam computed tomography (CT), percutaneous needle decompression in the setting of distended air-filled bowel interposed between the stomach and abdominal wall, post-pyloric balloon occlusion to facilitate gastric distension, ultrasound-guided gastric puncture, and intra-gastric contrast-enhanced ultrasound (ceUS) to define the relationship of the gastric wall and the anterior abdominal wall. Adjunctive techniques may increase successful primary percutaneous gastroenteric tube placement and may improve operator confidence in safe placement.

Pediatric musculoskeletal pathologies: are there differences in triage of diagnoses and preferences for communication between radiology and orthopedics?

OBJECTIVE: To define the clinical importance of various pediatric musculoskeletal diagnoses, determine preferred communication methods based on the acuity level of findings, and investigate differences between specialties utilizing the Delphi methodology. METHODS: Radiologists, orthopedic surgeons, and sports-medicine pediatricians at a tertiary children's hospital were surveyed (n = 79) twice using REDCap (Research Electronic Data Capture). Surveys were conducted anonymously and at least 1 year apart, first eliciting all potentially non-routine findings and various communication methods (round 1), and later categorizing the acuity (emergent, urgent, or non-urgent) of different diagnosis categories and selecting the preferred communication method (verbal, written electronic messages, and report) and timeframe (round 2). Chi-square, Fisher's exact, and Kruskal-Wallis H tests were used to compare variables between specialties. RESULTS: Round 1 produced 267 entries for non-routine findings (grouped into 19 diagnoses) and 71 for communication methods (grouped into 3 categories). Round 2 found no significant difference in the acuity assignments for the 19 predetermined diagnoses (p = 0.66) between the 3 specialties; however, there was reduced agreement for the top urgent diagnoses within and between specialties. Most pediatricians preferred written electronic messages. The preferred communication timeframe for urgent diagnoses was significantly different (< 2 h for pediatricians, < 4 h for radiologists, and < 8 h for surgeons; p = 0.003) between specialties whereas no difference was found for emergent (p = 1) and non-urgent diagnoses (p = 0.80). CONCLUSION: Acuity assignment for the 19 pediatric-specific musculoskeletal diagnoses was not significantly different between specialties, but the preferred communication timeframe for urgent diagnoses was significantly different, ranging between 2 and 8 h.

Primary thromboprophylaxis to prevent thrombotic events in pediatric oncology patients with a malignant mediastinal mass.

Children with malignant mediastinal masses have increased thrombotic events (TE). Eligible subjects with malignant mediastinal masses between January 2000 and December 2017 were evaluated for TE, with 19 among 76 subjects receiving enoxaparin thromboprophylaxis. There were 13 TEs among 76 subjects for an incidence of 17.1%. Mediastinal compression directly led to TE in 9.2% of subjects who also had statistically significant superior vena cava compression at diagnosis. Primary thromboprophylaxis did not significantly affect TE occurrence; however, larger studies are warranted to consider strategic thromboprophylaxis guided by radiological monitoring of dynamic vascular compression to improve TE outcomes.

Pediatric May-Thurner Syndrome-Systematic review and individual patient data meta-analysis.

BACKGROUND: The outcomes of deep vein thrombosis (DVT) in children with May-Thurner Syndrome (MTS) remain unclear. OBJECTIVES: This systematic review and patient-level meta-analysis aims to describe the outcomes of children with MTS presenting with DVT. METHODS: A systematic review of the published literature was performed. Data related to patients <18 years diagnosed with MTS and DVT was extracted. Risk of bias was assessed using the Murad criteria. Outcomes included vessel patency post-treatment, DVT recurrence, and post-thrombotic syndrome (PTS). Predictive and explanatory models were developed for these outcomes. RESULTS: In total, 109 cases were identified (age range 4-17 years; 77 females) in 28 studies; 75% of patients had ≥1 additional risk factor for DVT. PTS was seen in 61% of patients, DVT recurrence in 38%, and complete vessel patency post-treatment in 65%. The models developed to predict and explain PTS performed poorly overall. Recurrent thrombosis (adjusted for age and patency) predicted PTS (odds ratio [OR] 3.36, 95% confidence interval [CI] 1.28-8.82). DVT management strategies (adjusted for age and DVT characteristics) predicted vessel patency (OR 2.10, 95% CI 1.43-3.08). Lack of complete vessel patency (adjusted for age and thrombophilia) predicted recurrent DVT (OR 2.70, 95% CI 1.09-6.67). Sensitivity analyses showed the same direction of effects for all outcomes. CONCLUSIONS: PTS and DVT recurrence occur frequently in pediatric MTS. PTS prediction is complex and it was not possible to identify early predictors to guide clinical practice. Use of imaging-guided therapy and thrombus burden predicted venous patency, and lack of patency predicted DVT recurrence.

Ectopic Gallbladder Mimicking Choledochal Cyst on Hepatobiliary Scintigraphy.

The gallbladder is generally located at the anterolaterally situated gallbladder fossa on the undersurface of the liver, whereas choledochal cyst, as a dilation of the common bile duct, is located more posteromedially. We reported an ectopically located gallbladder, which appeared to be a choledochal cyst on hepatobiliary scintigraphy in a 10-year-old girl.

Ovarian dermoid cyst complicated by small bowel obstruction, entero-ovarian fistula formation, and malignant degeneration.

Dermoid cysts, or mature cystic teratomas, are complicated by malignant degeneration in only 1-2% of cases. Rarely, dermoid cysts result in complications of small bowel obstruction or entero-ovarian fistula formation. In the current report we present the case of a 59-year-old female with a known dermoid cyst who presented with leukocytosis and was discovered to have a small bowel obstruction at the level of an ileo-ovarian fistula. The patient was taken to the operating room and was treated with total abdominal hysterectomy, bilateral salpingo-oopherectomy, and short segment small bowel resection. Review of the surgical pathology revealed areas of malignant degeneration within the dermoid cyst to squamous cell carcinoma. To our knowledge, this is only the second reported case of an ovarian dermoid cyst complicated by small bowel obstruction, entero-ovarian fistula formation, and malignant degeneration.

The Utility of MRI in the Diagnosis of Takayasu Arteritis.

Takayasu Arteritis (TA) is an inflammatory disorder involving the thoracoabdominal aorta and its branches and the pulmonary arteries, with eventual vascular stenosis, occlusion, or aneurysm formation. Conventional angiography has been the reference imaging standard for diagnosis of TA. The purpose of this case report is to demonstrate the utility of MR imaging and MR angiography in the diagnosis of Takayasu Arteritis in a pediatric patient. The patient is a 15-year-old female patient presenting with anemia, hypertension, and acute kidney injury. Initial chest CT demonstrated ectasia of the ascending and focal stenosis of the descending thoracic aorta, prompting further evaluation with MRI and MRA. MRI/MRA demonstrated mural thickening with luminal stenosis of the aorta and aortic branch vessels. These imaging findings were suggestive of a large vessel arteritis and along with the clinical presentation and laboratory abnormalities the diagnosis of Takayasu Arteritis was suggested. Several case series in adults have described the cross-sectional findings of TA. However, this case report demonstrates the utility of MRI/MRA in the evaluation of TA in children and in the course of follow-up, as it provides a noninvasive method for evaluating a child without ionizing radiation or iodinated contrast.

Endovascular Thrombolysis in the Management of Iliofemoral Thrombosis in Children: A Multi-Institutional Experience.

PURPOSE: To evaluate technical feasibility, complications, and clinical outcomes of endovascular thrombolysis for iliofemoral thrombosis at two tertiary-care children's hospitals. MATERIALS AND METHODS: Institutional review board-approved retrospective review from March 2003 through June 2013 showed that venous thrombolysis for iliofemoral thrombosis was performed in 57 children (64 limbs) with a median age of 16.1 years (mean age, 14.5 y; range, 1.0-17.8 y). Techniques included catheter-directed thrombolysis (CDT), percutaneous mechanical thrombectomy (PMT), and pharmacomechanical catheter-directed thrombolysis (PCDT) with adjunctive angioplasty and/or stent placement. Villalta and modified Villalta scales were applied retrospectively to follow-up data to assess postthrombotic syndrome (PTS). RESULTS: Technical success (≥ 50% thrombolysis) rate was 93.7%: grade III (100%) in 19 limbs, grade II (50%-99%) in 41 limbs, and grade I (< 50%) in four limbs. Techniques included CDT with PCDT (32.8%) or PMT (35.9%), CDT alone (26.6%), PCDT alone (4.7%) or with adjunctive angioplasty (54.7%), and stent placement (6.3%). Mean duration of CDT was 36.5 hours (range, 2.9-89.6 h). There was one major complication (1.8%) of bleeding requiring transfusion. Minor complications (ie, bleeding) occurred in seven patients (12.2%). Median follow-up was 1.5 years (range, 30 d to 7 y). Seven patients underwent repeat thrombolysis for recurrent thrombosis. The PTS rate was 59.3% per modified Villalta scale but only 2.1% per Villalta scale. CONCLUSIONS: Endovascular thrombolysis is technically feasible and safe for iliofemoral thrombosis in children. Variable results were seen with two scales to assess PTS, suggesting an acute need for standardization of outcome measurement in children.

Lower Extremity Vascular Access in Neonates and Infants: A Single Institutional Experience.

PURPOSE: To demonstrate feasibility and evaluate outcomes of direct-stick saphenous and single-incision tunneled femoral noncuffed central venous catheters (CVCs) placed in a large series of neonates and infants at a single institution. MATERIALS AND METHODS: A retrospective review was performed for all neonates and infants receiving a lower extremity CVC by interventional radiology between 2007 and 2012. Technical success, mechanical and infectious complications, and catheter outcomes were recorded. RESULTS: There were 271 primary insertions performed in 243 children by interventional radiologists in the interventional radiology suite or at the bedside. CVCs were placed via the femoral vein with single-incision technique (84.9%) or the saphenous vein via a direct-stick technique (15.1%), with a technical success rate of 100%. The total number of catheter-days was 7,917 days (median, 19 d; range, 0-220 d). The number of primary catheter-days was 5,333 days (median, 15 d; range, 0-123.0 d), and salvage procedures prolonged catheter life by 2,584 days (median, 15 d; range, 1.0-101.0 d). The mechanical and adjusted infectious complication rates were 1.67 and 0.44 per 100 catheter-days. CONCLUSIONS: Image-guided placement of saphenous or tunneled femoral catheters using a single incision is a safe and feasible method for vascular access in neonates and infants.

Transiliopsoas approach: an alternative route to drain pelvic abscesses in children.

OBJECTIVE: To evaluate an alternative route of pelvic abscess drainage in children via a transiliopsoas approach. BACKGROUND: Appendiceal perforations complicated by inflammatory masses, such as abscesses or phlegmon, are a common indication for abdominal drainage in pediatric interventional radiology. Certain locations of collections may present particular challenges for the operator, owing to numerous surrounding structures, including bowel and other pelvic anatomy. This series describes an alternative route for drainage, which involves traversing the iliopsoas muscle under US guidance to drain a deep pelvic abscess. MATERIALS AND METHODS: Retrospective chart review was performed of the transiliopsoas approach for abscess drainage during a 5-year period. The technique, pre- and post-drainage imaging, aspiration/drain output, duration of catheter dwell, procedure-related complications and abscess recurrence were reviewed. RESULTS: Transiliopsoas needle placement was successful in 14 of 14 patients (100%). Catheter placement was successful in 13 patients. Abscess wall rupture precluded catheter placement in one patient. Mean catheter duration was 4.9 days, with a range of 2 to 9 days. Clinical improvement was achieved in all 14 patients (100%). There were no major complications. Post-procedure pain with ambulation was reported in 3 of 14 patients (21.4%), which was successfully controlled in each case with medication, and resolved after 2 days. CONCLUSION: The transiliopsoas route is a safe and effective route for US-guided abscess drainage and catheter placement in children with deep pelvic collections. In selected cases, this approach provides a more easily accessible and safer route than more traditional interventional approaches.

US-guided placement and tip position confirmation for lower-extremity central venous access in neonates and infants with comparison versus conventional insertion.

PURPOSE: To describe experience with the use of ultrasound (US)-guided placement and tip position confirmation for direct saphenous and single-incision tunneled femoral noncuffed central venous catheters (CVCs) placed in neonates and infants at the bedside. MATERIALS AND METHODS: A retrospective review of the interventional radiology (IR) database and electronic medical records was performed for 68 neonates and infants who received a CVC at the bedside and for 70 age- and weight-matched patients with CVCs placed in the IR suite between 2007 and 2012. Technical success, complications, and outcomes of CVCs placed at the bedside were compared with those in an age- and weight-matched sample of children with CVCs placed in the IR suite. RESULTS: A total of 150 primary insertions were performed, with a technical success rate of 100%. Total catheter lives for CVCs placed at the bedside and in the IR suite were 2,030 catheter-days (mean, 27.1 d) and 2,043 catheter-days (mean, 27.2 d), respectively. No significant difference was appreciated between intraprocedural complications, mechanical complications (bedside, 1.53 per 100 catheter-days; IR, 1.76 per 100 catheter-days), or infectious complications (bedside, 0.39 per 100 catheter-days; IR, 0.34 per 100 catheter-days) between groups. CONCLUSIONS: US-guided placement and tip position confirmation of lower-extremity CVCs at bedside for critically ill neonates and infants is a safe and feasible method for central venous access, with similar complications and catheter outcomes in comparison with CVCs placed by using fluoroscopic guidance in the IR suite.

Single-incision technique for placement of tunneled internal jugular vein vascular access in children.

BACKGROUND: Central venous access is indispensable in caring for children with infections, malignancies and chronic illnesses, and image-guided placement of central venous access devices (CVAD) is increasingly used. A single-incision technique for placement of tunneled central venous access devices at the internal jugular vein has been described; however the technique has not been described exclusively in children. OBJECTIVE: To describe our initial experience using the single-incision technique for tunneled central venous access at the internal jugular vein in children. MATERIALS AND METHODS: We conducted a retrospective review of the interventional radiology database and electronic medical records of 15 children who received a tunneled central venous access device (CVAD) using a single incision between 2010 and 2012. Patients included eight boys and seven girls with an average age of 11 years (median 13.3 years, range 1-18.7 years) and average weight of 44.2 kg (median 38.3 kg, range 9.6-99.0 kg). RESULTS: A total of 17 primary insertions were performed. Technical success was 100%. Total catheter life consisted of 1,416 catheter-days (mean 83.3 days, range 8-502 days). There were no procedure-related or early complications. Seven late complications requiring intervention occurred in three catheters. Total mechanical and infectious complications occurred at rates of 0.28 and 0.21 per 100 catheter-days, respectively. The adjusted rate for infectious complications was 0.14 per 100 catheter-days. Medical salvage procedures (83%) and interventional radiology salvage procedures (17%) prolonged catheter life by an average of 94.5 days (range 10-329 days). CONCLUSION: This study demonstrates safe use and technical feasibility of the image-guided single-incision technique for central venous access in children, particularly in children in whom the conventional technique is less desirable.

Intraoperative cerebral angiography in arteriovenous malformation resection in children: a single institutional experience.

OBJECT: The use of cerebral intraoperative angiography has been described in resection of arteriovenous malformations (AVMs) in adults. More recently, studies have described experiences with intraoperative angiography in a small number of children. However, data on the safety and clinical utility of intraoperative angiography in the pediatric population remains limited in comparison with available data in adults. The aim of the study was to evaluate the use of cerebral intraoperative angiography in children undergoing AVM resection. The clinical utility of intraoperative angiography and procedure-related complications were evaluated. METHODS: A retrospective review was performed for all patients undergoing cerebral AVM resection with intraoperative angiography at The Children's Hospital of Philadelphia between 2008 and 2012. Patient imaging and operative and medical notes were reviewed to evaluate for end points of the study. A total of 17 patients (8 males, 9 females) were identified, with a median age of 12.1 years (range 1.2-17.9 years) and median weight of 45.5 kg (range 12.1-78.9 kg). RESULTS: A total of 21 intraoperative angiography procedures were performed for 18 AVM resections in 17 patients. The technical success rate was 94%. In 2 cases (11%), intraoperative angiography demonstrated a residual AVM, and repeat resections were performed. In both cases, no recurrent disease was noted on postoperative follow-up. One procedure-related complication (4.8%) occurred in 1 patient who was positioned prone. Recurrence to date was noted in 2 (14%) of the 14 cases with available postoperative follow-up at 3.5 and 4.7 months following resection with intraoperative angiography. The median follow-up time from intraoperative angiography to the most recent postoperative angiography was 1.1 years (range 4.3 months to 3.8 years). CONCLUSIONS: Intraoperative angiography is an effective and safe adjunct for surgical management of cerebral AVMs in the pediatric population.

Role of JNK-1 regulation in the protection of contact-inhibited fibroblasts from oxidative stress.

The molecular signaling events leading to protection from oxidative stress-induced apoptosis upon contact inhibition have not been fully investigated. Previous research has indicated a role for mitogen-activated protein kinases (MAPKs) in the regulation of contact inhibition, and these proteins have also been associated with cell cycle regulation and stress-induced apoptosis. The potential role of the MAPK JNK-1 in the stress-response of actively proliferating and contact-inhibited cells was investigated. Actively proliferating normal fibroblasts (BJ) and fibrosarcoma cells (HT-1080) were stressed with H2O2, and levels of activated JNK-1 and cleaved PARP were ascertained. Similarly, these results were compared with levels of activated JNK-1 and cleaved PARP detected in H2O2-stressed confluent fibrosarcoma or contact-inhibited fibroblast cells. Contact-inhibited fibroblasts were protected from apoptosis in comparison to subconfluent fibroblasts, concurrent with decreased JNK-1 activation. Increased culture density of fibrosarcoma cells was not protective against apoptosis, and these cells did not demonstrate density-dependent alterations in the JNK-1 stress response. This decreased activation of JNK-1 in stressed, contact-inhibited cells did not appear to be dependent upon increased expression of MKP-1; however, over-expression of MKP-1 was sufficient to result in a slight decrease in H2O2-stimulated PARP cleavage. Increasing the antioxidant capacity of fibroblasts through NAC-treatment not only lessened H2O2-stimulated JNK-1 activation, but also did not influence the expression of MKP-1. Taken together, these results suggest that regulation of negative regulation of JNK-1 upon contact inhibition is protective against apoptosis, and that this regulation is independent of MKP-1.