Brief Resolved Unexplained Events Symptoms Frequently Result in Inappropriate Gastrointestinal Diagnoses and Treatment.

OBJECTIVE: To determine associations between presenting symptoms and oropharyngeal dysphagia diagnoses, gastroesophageal reflux disease (GERD) diagnoses, and treatment with acid suppression medication in infants with brief resolved unexplained event (BRUE). STUDY DESIGN: We performed a prospective cohort study of infants with BRUE to review presenting symptoms and their potential impact on testing and treatment. Videofluoroscopic swallow study (VFSS) results and explanatory diagnoses were obtained from medical record review; acid suppression use was determined by parental survey. Binary and multivariable logistic regression models were used to evaluate associations between presenting symptoms and obtaining VFSS, VFSS results, GERD diagnoses, and acid suppression medication. RESULTS: Presenting symptoms were varied in 157 subjects enrolled at 51.0 ± 5.3 days of age, with many symptoms that may be related to GERD or dysphagia. Of these, 28% underwent VFSS with 71% abnormal. Overall, 42% had their BRUE attributed to GERD, and 33% were treated with acid suppression during follow-up. Presenting symptoms were significantly associated with the decision to obtain VFSS but not with abnormal VFSS results. Presenting symptoms were also associated with provision of GERD explanatory diagnoses. Both presenting symptoms and GERD explanatory diagnoses were associated with acid suppression use (aOR 2.3, 95% CI 1.03-5.3, P = .04). CONCLUSIONS: Presenting symptoms may play a role in clinicians' decisions on which BRUE patients undergo VFSS but are unreliable to make a diagnosis of oropharyngeal dysphagia. Presenting symptoms may also influence assignment of GERD explanatory diagnoses that is associated with increased acid suppression medication use.

A Prospective Study of Parental Experience with Thickening Feeds for Children with Oropharyngeal Dysphagia and Gastroesophageal Reflux.

Thickening is efficacious and commonly recommended for oropharyngeal dysphagia and gastroesophageal reflux. Little is known about parental experience with this practice. Results of this cross-sectional questionnaire study suggest attitudes are positive, but parents frequently adjust recipes/nipple sizes, which might increase aspiration risk. Clinical follow-up is essential to ensure safe feeding.

Pediatric Aerodigestive Medicine: Advancing Collaborative Care for Children With Oropharyngeal Dysphagia.

OBJECTIVES: Aerodigestive disorders encompass various pathological conditions affecting the lungs, upper airway, and gastrointestinal tract in children. While advanced care has primarily occurred in specialty centers, many children first present to general pediatric gastroenterologists with aerodigestive symptoms necessitating awareness of these conditions. At the 2021 Annual North American Society for Pediatric Gastroenterology, Hepatology and Nutrition meeting, the aerodigestive Special Interest Group held a full-day symposium entitled, Pediatric Aerodigestive Medicine: Advancing Collaborative Care of Children with Aerodigestive Disorders. The symposium aimed to underline the significance of a multidisciplinary approach to achieve better outcomes for these complex patients. METHODS: The symposium brought together leading experts to highlight the growing aerodigestive field, promote new scientific and therapeutic strategies, share the structure and benefits of a multidisciplinary approach in diagnosing common and rare aerodigestive disorders, and foster multidisciplinary discussion of complex cases while highlighting the range of therapeutic and diagnostic options. In this article, we showcase the diagnostic and therapeutic approach to oropharyngeal dysphagia (OPD), one of the most common aerodigestive conditions, emphasizing the role of a collaborative model. CONCLUSIONS: The aerodigestive field has made significant progress and continues to grow due to a unique multidisciplinary, collaborative model of care for these conditions. Despite diagnostic and therapeutic challenges, the multidisciplinary approach has enabled and greatly improved efficient, high-quality, and evidence-based care for patients, including those with OPD.

Acid Suppression Does Not Improve Laryngomalacia Outcomes but Treatment for Oropharyngeal Dysphagia Might Be Protective.

OBJECTIVE: To determine whether the use of acid suppression and thickened feeds impact laryngomalacia outcomes in infants, including supraglottoplasty risk, time to supraglottoplasty, and hospitalization risk. STUDY DESIGN: We performed a retrospective cohort study to compare risk and time with supraglottoplasty and frequency and duration of hospitalizations for infants diagnosed with laryngomalacia at Boston Children's Hospital between January 1 and December 31, 2017. The primary outcomes were supraglottoplasty requirement, time to supraglottoplasty, and hospitalization risk. Multivariate analyses were performed to determine predictors of supraglottoplasty and hospitalization risk after adjusting for laryngomalacia severity and comorbidities in addition to propensity score adjustment. Kaplan-Meier curves were created to determine the impact of acid suppression use on time to supraglottoplasty. RESULTS: In total, 236 subjects with mean age 62.6 ± 4 days were included in the analysis; 55% were treated with acid suppression. Subjects treated with acid suppression had a greater risk of supraglottoplasty (hazard ratio 3.36, 95% CI 1.36-8.29, P = .009), shorter time to supraglottoplasty (5.64 ± 0.92 vs 7.98 ± 1.92 months, P = .006), and increased respiratory hospitalization risk (relative risk 1.97, 95% CI 1.01-3.85, 0.047), even after adjustment for covariates. Subjects receiving thickening had fewer respiratory hospitalization nights and longer time to supraglottoplasty (9.3 ± 1.7 vs 4.56 ± 0.73 months, P = .004), even after adjustment. CONCLUSIONS: Acid suppression use does not reduce the frequency of supraglottoplasty and related hospitalizations compared with untreated subjects. However, patients treated with thickening have decreased hospitalization and longer time to supraglottoplasty, suggesting that thickening of feeds may be a preferred intervention over acid suppression.

Overlapping Symptoms of Gastroesophageal Reflux and Aspiration Highlight the Limitations of Validated Questionnaires.

OBJECTIVES: Infants frequently present with feeding difficulties and respiratory symptoms, which are often attributed to gastroesophageal reflux but may be because of oropharyngeal dysphagia with aspiration. The Infant Gastroesophageal Reflux Questionnaire Revised (I-GERQ-R) is a clinical measure of gastroesophageal reflux disease but now there is greater understanding of dysphagia as a reflux mimic. We aimed to determine the degree of overlap between I-GERQ-R and evidence of dysphagia, measured by Pediatric Eating Assessment Tool-10 (Pedi-EAT-10) and videofluoroscopic swallow study (VFSS). METHODS: We performed a prospective study of subjects <18 months old with feeding difficulties. All parents completed Pedi-EAT-10 and I-GERQ-R as a quality initiative to address parental feeding concerns. I-GERQ-R results were compared with Pedi-EAT-10 and, whenever available, results of prior VFSS. Pearson correlation coefficients were calculated to determine the relationship between scores. Groups were compared with 1-way ANOVA and Fisher exact test. ROC analysis was completed to compare scores with VFSS results. RESULTS: One hundred eight subjects with mean age 7.1 ±â€Š0.5 months were included. Pedi-EAT-10 and I-GERQ-R were correlated (r = 0.218, P = 0.023) in all subjects and highly correlated in the 77 subjects who had prior VFSS (r = 0.369, P = 0.001). The blue spell questions on I-GERQ-R had relative risk 1.148 (95% confidence interval [CI] 1.043-1.264, P = 0.142) for predicting aspiration/penetration on VFSS, with 100% specificity. Scores on the question regarding crying during/after feedings were also higher in subjects with abnormal VFSS (1.1 ±â€Š0.15 vs 0.53 ±â€Š0.22, P = 0.04). CONCLUSIONS: I-GERQ-R and the Pedi-EAT-10 are highly correlated. I-GERQ-R results may actually reflect oropharyngeal dysphagia and not just gastroesophageal reflux disease in infants.

The Impact of the American Academy of Pediatrics Brief Resolved Unexplained Event Guidelines on Gastrointestinal Testing and Prescribing Practices.

OBJECTIVES: To determine if hospitalization, testing, diagnosis, and management of suspected gastroesophageal reflux, and follow-up visits decreased since introduction of American Academy of Pediatrics guidelines for brief resolved unexplained events (BRUEs). STUDY DESIGN: We performed a retrospective cohort study of infants with BRUE evaluated at Boston Children's Hospital in the year before and after guideline implementation to determine if practice patterns have changed. Outcomes included hospitalization rates, frequency of swallow assessments, other diagnostic testing, and reflux diagnoses, cost of care, and number of repeat visits. Groups were compared based on whether they presented before or after guideline implementation. RESULTS: In total, 359 subjects (186 pre-, 173 post-guidelines) were identified. There were no significant differences in practice patterns or outcomes before or after guideline implementation. Subjects had mean age 2.53 ± 0.15 months, and 80% were hospitalized for 2.49 ± 0.26 days. Each subject had 2.47 diagnostic tests performed, and 89% were noncontributory. Despite only 13% having videofluoroscopic swallow study performed, 72% showed aspiration/penetration. No subject had gastroesophageal reflux testing, yet reflux was implicated as the cause for admission in 40% of subjects, resulting in increased odds of discharge on acid suppressing medications (OR 2.88, 95% CI 1.68-4.92, P = .0001). In follow-up, 28% of subjects had repeat hospitalizations or emergency department visits for persistent symptoms. CONCLUSIONS: Infants with BRUE continue to undergo low-yield diagnostic testing and after admission remain symptomatic and frequently re-present to medical care. Swallow testing remains infrequent despite its high-yield, reflux continues to be implicated and children are still being discharged on acid suppression despite lack of efficacy.

Feeding Interventions Are Associated With Improved Outcomes in Children With Laryngeal Penetration.

OBJECTIVES: To determine if children with laryngeal penetration on videofluoroscopic swallow study (VFSS) who received feeding interventions (thickened liquids, change in liquid flow rate, and/or method of liquid delivery) had improved symptoms and decreased hospitalizations compared with those without intervention. METHODS: We performed a retrospective cohort study of children under 2 years with laryngeal penetration on VFSS at our institution in 2015 to determine initial and follow-up VFSS findings, symptom improvement at follow-up, and hospitalization risk before and after VFSS. Proportions were compared with Fisher exact test and hospitalizations with paired t tests. RESULTS: We evaluated 137 subjects with age 8.93 ±â€Š0.59 months who had laryngeal penetration without aspiration on VFSS. Fifty-five percent had change in management, with 40% receiving thickening and 15% a change in flow rate. There was significant improvement in symptoms for children that had feeding intervention and this improvement was the greatest with thickening (OR 41.8, 95% CI 12.34-141.69, P < 0.001). On repeat VFSS, 26% had evidence of aspiration that was not captured on initial VFSS. Subjects had decreased total and pulmonary hospitalizations with feeding intervention and decreased pulmonary nights with thickening (P < 0.05). CONCLUSIONS: Laryngeal penetration appears to be clinically significant in children with oropharyngeal dysphagia and interventions to decrease its occurrence are associated with improved outcomes including decreased symptoms of concern and hospitalization nights. Thickening or other feeding intervention should be considered for all symptomatic children with laryngeal penetration on swallow study.

Clinical Aspects of Thickeners for Pediatric Gastroesophageal Reflux and Oropharyngeal Dysphagia.

PURPOSE OF REVIEW: The purpose of this review is to discuss current knowledge and recent findings regarding clinical aspects of thickeners for pediatric gastroesophageal reflux and oropharyngeal dysphagia. We review evidence for thickener efficacy, discuss types of thickeners, practical considerations when using various thickeners, and risks and benefits of thickener use in pediatrics. RECENT FINDINGS: Thickeners are effective in decreasing regurgitation and improving swallowing mechanics and can often be used empirically for the treatment of infants and young children. Adverse effects have been reported, but with careful consideration of appropriate thickener types, desired thickening consistency, and follow-up in collaboration with feeding specialists, most patients have symptomatic improvements. Thickeners are typically well tolerated and with few side effects, but close follow-up is needed to make sure patients tolerate thickeners and have adequate symptom improvement.

Presenting Signs and Symptoms do not Predict Aspiration Risk in Children.

OBJECTIVES: To determine if any presenting symptoms are associated with aspiration risk, and to evaluate the reliability of clinical feeding evaluation (CFE) in diagnosing aspiration compared with videofluoroscopic swallow study (VFSS). STUDY DESIGN: We retrospectively reviewed records of children under 2 years of age who had evaluation for oropharyngeal dysphagia by CFE and VFSS at Boston Children's Hospital and compared presenting symptoms, symptom timing, and CFE and VFSS results. We investigated the relationship between symptom presence and aspiration using the Fisher exact test and stepwise logistic regression with adjustment for comorbidities. CFE and VFSS results were compared using the McNemar test. Intervals from CFE to VFSS were compared using the Student t test. RESULTS: A total of 412 subjects with mean (±SD) age 8.9 ± 6.9 months were evaluated. No symptom, including timing relative to meals, predicted aspiration on VFSS. This lack of association between symptoms and VFSS results persisted even in the adjusted multivariate model. The sensitivity of CFE for predicting aspiration by VFSS was 44%. Patients with a reassuring CFE waited 28.2 ± 8.5 days longer for confirmatory VFSS compared with those with a concerning CFE (P < .05). CONCLUSIONS: Presenting symptoms are varied in patients with aspiration and cannot be relied upon to determine which patients have aspiration on VFSS. The CFE does not have the sensitivity to consistently diagnose aspiration so a VFSS should be performed in persistently symptomatic patients.

Oropharyngeal Dysphagia Is Strongly Correlated With Apparent Life-Threatening Events.

OBJECTIVES: The aim of the present study was to investigate the prevalence of oropharyngeal dysfunction with resultant aspiration in patients admitted after apparent life-threatening events (ALTE) and to determine whether historical characteristics could predict this oropharyngeal dysphagia and aspiration risk. METHODS: We retrospectively reviewed the records of all patients admitted to Boston Children's Hospital between 2012 and 2015 with a diagnosis of ALTE to determine the frequency of evaluation for oropharyngeal dysphagia using video fluoroscopic swallow studies (VFSS) and clinical feeding evaluations, to determine the prevalence of swallowing dysfunction in subjects admitted after ALTE and to compare presenting historical characteristics to swallow study results. RESULTS: A total of 188 children were admitted with a diagnosis of ALTE of which 29% (n = 55) had an assessment of swallowing by VFSS. Of those who had a VFSS, 73% (n = 40) had evidence of aspiration or penetration on VFSS. Of all of the diagnostic tests ordered on patients with ALTEs, the VFSS had the highest rate of abnormalities of any test ordered. None of the historical characteristics of ALTE predicted which patients were at risk for aspiration. In patients who had both clinical feeding evaluations and VFSS, observed clinical feedings incorrectly identified 26% of patients as having no oropharyngeal dysphagia when in fact aspiration was present on VFSS. CONCLUSIONS: Oropharyngeal dysphagia with aspiration is the most common diagnosis identified in infants presenting with ALTEs. The algorithm for ALTE should be revised to include an assessment of VFSS as clinical feeding evaluations are inadequate to assess for aspiration.

Gastroesophageal Reflux Burden, Even in Children That Aspirate, Does Not Increase Pediatric Hospitalization.

OBJECTIVES: Gastroesophageal reflux is common but remains a controversial disease to diagnose and treat and little is known about the role of reflux testing in predicting clinical outcomes, particularly in children at risk for extraesophageal reflux complications. The aim of this study was to determine if rates of hospitalization were affected by reflux burden even after adjusting for aspiration risk. METHODS: We prospectively recruited, between 2009 and 2014, a cohort of pediatric patients with suspected extraesophageal reflux disease who were referred for reflux testing and underwent both multichannel intraluminal impedance with pH (pH-MII) and modified barium swallow studies. A subset of patients also underwent bronchoalveolar lavage with pepsin analysis. We determined their rates of hospitalization for a minimum of 1 year following pH-MII testing. RESULTS: We prospectively enrolled 116 pediatric patients who presented for care at Boston Children's Hospital and underwent both pH-MII and modified barium swallow studies. There was no statistically significant relationship between reflux burden measured by pH-MII or bronchoalveolar pepsin and total number of admissions or number of admission nights even after adjusting for aspiration status (P > 0.2). There were no statistically significant relationships between reflux burden by any method and the number or nights of urgent pulmonary admissions before or after adjusting for aspiration risk (P > 0.08). CONCLUSIONS: Even in aspirating children, reflux burden did not increase the risk of hospitalization. Based on these results, routine reflux testing cannot be recommended even in aspirating children, because the results do not impact clinically significant outcomes.

Breastfeeding in infants who aspirate may increase risk of pulmonary inflammation.

OBJECTIVE: To evaluate management strategies and pulmonary outcomes for breastfed infants with oropharyngeal dysphagia. STUDY DESIGN: We performed a retrospective cohort study of breastfed infants diagnosed with oropharyngeal dysphagia with documented aspiration or laryngeal penetration on videofluoroscopic swallow study (VFSS). Medical records were reviewed for VFSS results and speech-language pathologist recommendations following VFSS, results of chest x-ray, results of bronchoalveolar lavage (BAL) within 1 year of VFSS, and aspiration-related hospitalizations occurring before or within 1 year of VFSS. Subjects were categorized as cleared or not cleared to breastfeed based on the VFSS. Proportions were compared with Chi-square and Fisher's exact tests and means with Student's t-tests. RESULTS: Seventy-six infants (4.7 ± 0.4 months old) were included; 50% (38) had aspiration and 50% (38) had laryngeal penetration. After VFSS, 70% (53) were cleared to breastfeed while 30% (23) were not cleared to breastfeed. Patients with aspiration were less likely to be cleared to breastfeed (p = .006); however, 55% (21/38) of those with aspiration were still cleared to breastfeed. Infants cleared to breastfeed had significantly more pulmonary hospitalizations (p = .04) and were also at increased risk of elevated neutrophil count (p = .02) and culture growth on BAL (p = .01). Significantly increased abnormal neutrophil count was also found in those cleared to breastfeed with laryngeal penetration (p = .01). CONCLUSIONS: Infants with oropharyngeal dysphagia counseled to continue breastfeeding had increased risk of BAL inflammation and more pulmonary hospitalizations compared to those that were told to stop breastfeeding.

Gastrointestinal factors associated with risk of bronchiectasis in children.

OBJECTIVE: To evaluate gastrointestinal (GI) risk factors for bronchiectasis in children. We hypothesized that upper GI tract dysmotility would be associated with increased risk of bronchiectasis. STUDY DESIGN: Subjects in this retrospective cohort study included those evaluated for persistent pulmonary symptoms in the Aerodigestive Center at Boston Children's Hospital who underwent chest computed tomography (CT) between 2002 and 2019. To determine gastrointestinal predictors of bronchiectasis, baseline characteristics, comorbidities, enteral tube status, medications received, gastroesophageal reflux burden, adequacy of swallow function, esophageal dysmotility, gastric dysmotility, and neutrophil count on bronchoalveolar lavage (BAL) were compared between patients with and without bronchiectasis. Proportions were compared with Fisher's exact test and binary logistic regression with stepwise selection was used for multivariate analysis. ROC analyses were utilized to compare BAL neutrophils and bronchiectasis. RESULTS: Of 192 subjects, 24% were found to have evidence of bronchiectasis on chest CT at age 7.9 ± 0.5 years. Enteral tubes (OR 5.77, 95% CI 2.25-14.83, p < 0.001) and increased BAL neutrophil count (OR 5.79, 95% CI 1.87-17.94, p = 0.002) were associated with increased risk while neurologic comorbidities were associated with decreased risk (OR 0.24, 95% CI 0.09-0.66, p = 0.006). Gastroesophageal reflux was not found to be a significant risk factor. Neutrophil counts >10% had 72% sensitivity and 60% specificity for identifying bronchiectasis. CONCLUSIONS: Enteral tubes were associated with significantly increased risk of bronchiectasis but gastroesophageal reflux was not. Providers should consider obtaining chest CT to evaluate for bronchiectasis in children found to have unexplained elevated BAL neutrophil count.

A critical role for macrophages in neovessel formation and the development of stenosis in tissue-engineered vascular grafts.

The primary graft-related complication during the first clinical trial evaluating the use of tissue-engineered vascular grafts (TEVGs) was stenosis. We investigated the role of macrophages in the formation of TEVG stenosis in a murine model. We analyzed the natural history of TEVG macrophage infiltration at critical time points and evaluated the role of cell seeding on neovessel formation. To assess the function of infiltrating macrophages, we implanted TEVGs into mice that had been macrophage depleted using clodronate liposomes. To confirm this, we used a CD11b-diphtheria toxin-receptor (DTR) transgenic mouse model. Monocytes infiltrated the scaffold within the first few days and initially transformed into M1 macrophages. As the scaffold degraded, the macrophage infiltrate disappeared. Cell seeding decreased the incidence of stenosis (32% seeded, 64% unseeded, P=0.024) and the degree of macrophage infiltration at 2 wk. Unseeded TEVGs demonstrated conversion from M1 to M2 phenotype, whereas seeded grafts did not. Clodronate and DTR inhibited macrophage infiltration and decreased stenosis but blocked formation of vascular neotissue, evidenced by the absence of endothelial and smooth muscle cells and collagen. These findings suggest that macrophage infiltration is critical for neovessel formation and provides a strategy for predicting, detecting, and inhibiting stenosis in TEVGs.

Determining the fate of seeded cells in venous tissue-engineered vascular grafts using serial MRI.

A major limitation of tissue engineering research is the lack of noninvasive monitoring techniques for observations of dynamic changes in single tissue-engineered constructs. We use cellular magnetic resonance imaging (MRI) to track the fate of cells seeded onto functional tissue-engineered vascular grafts (TEVGs) through serial imaging. After in vitro optimization, murine macrophages were labeled with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles and seeded onto scaffolds that were surgically implanted as inferior vena cava interposition grafts in SCID/bg mice. Serial MRI showed the transverse relaxation times (T(2)) were significantly lower immediately following implantation of USPIO-labeled scaffolds (T(2) = 44 ± 6.8 vs. 71 ± 10.2 ms) but increased rapidly at 2 h to values identical to control implants seeded with unlabeled macrophages (T(2) = 63 ± 12 vs. 63 ± 14 ms). This strongly indicates the rapid loss of seeded cells from the scaffolds, a finding verified using Prussian blue staining for iron containing macrophages on explanted TEVGs. Our results support a novel paradigm where seeded cells are rapidly lost from implanted scaffolds instead of developing into cells of the neovessel, as traditionally thought. Our findings confirm and validate this paradigm shift while demonstrating the first successful application of noninvasive MRI for serial study of cellular-level processes in tissue engineering.

Tissue-engineered vascular grafts form neovessels that arise from regeneration of the adjacent blood vessel.

We developed a tissue-engineered vascular graft composed of biodegradable scaffold seeded with autologous bone marrow-derived mononuclear cells (BMMCs) that is currently in clinical trial and developed analogous mouse models to study mechanisms of neovessel formation. We previously reported that seeded human BMMCs were rapidly lost after implantation into immunodeficient mice as host macrophages invaded the graft. As a consequence, the resulting neovessel was entirely of host cell origin. Here, we investigate the source of neotissue cells in syngeneic BMMC-seeded grafts, implanted into immunocompetent mouse recipients. We again find that seeded BMMCs are lost, declining to 0.02% at 14 d, concomitant with host macrophage invasion. In addition, we demonstrate using sex-mismatched chimeric hosts that bone marrow is not a significant source of endothelial or smooth muscle cells that comprise the neovessel. Furthermore, using composite grafts formed from seeded scaffold anastomosed to sex-mismatched natural vessel segments, we demonstrate that the adjacent vessel wall is the principal source of these endothelial and smooth muscle cells, forming 93% of proximal neotissue. These findings have important implications regarding fundamental mechanisms underlying neotissue formation; in this setting, the tissue-engineered construct functions by mobilizing the body's innate healing capabilities to "regenerate" neotissue from preexisting committed tissue cells.

Characterization of the natural history of extracellular matrix production in tissue-engineered vascular grafts during neovessel formation.

BACKGROUND: The extracellular matrix (ECM) is a critical determinant of neovessel integrity. MATERIALS AND METHODS: Thirty-six (polyglycolic acid + polycaprolactone and poly lactic acid) tissue-engineered vascular grafts seeded with syngeneic bone marrow mononuclear cells were implanted as inferior vena cava interposition grafts in C57BL/6 mice. Specimens were characterized using immunohistochemical staining and qPCR for representative ECM components in addition to matrix metalloproteinases (MMPs). Total collagen, elastin, and glycosaminoglycan (GAG) contents were determined. MMP activity was measured using zymography. RESULTS: Collagen production on histology demonstrated an initial increase in type III at 1 week followed by type I production at 2 weeks and type IV at 4 weeks. Gene expression of both type I and type III peaked at 2 weeks, whereas type IV continued to increase over the 4-week period. Histology demonstrated fibrillin-1 deposition at 1 week followed by elastin production at 4 weeks. Elastin gene expression significantly increased at 4 weeks, whereas fibrillin-1 decreased at 4 weeks. GAG demonstrated abundant production at each time point on histology. Gene expression of decorin significantly increased at 4 weeks, whereas versican decreased over time. Biochemical analysis showed that total collagen production was greatest at 2 weeks, and there was a significant increase in elastin and GAG production at 4 weeks. Histological characterization of MMPs showed abundant production of MMP-2 at each time point, while MMP-9 decreased over the 4-week period. Gene expression of MMP-2 significantly increased at 4 weeks, whereas MMP-9 significantly decreased at 4 weeks. CONCLUSIONS: ECM production during neovessel formation is characterized by early ECM deposition followed by extensive remodeling.