Validation of a small animal model for soft tissue filler characterization.

BACKGROUND: Rigorous preclinical testing of soft tissue fillers has been lacking. No animal model has emerged as an accepted standard to evaluate tissue filler longevity. OBJECTIVE: To validate a small animal model to compare soft tissue filler degradation and tissue reaction. METHODS: Preliminary experiments compared caliper with magnetic resonance imaging volumetric analysis. Next, four hyaluronic acid (HA) fillers were injected into the dermis of Sprague-Dawley rats. The three dimensions of the implants were measured at day 0, day 1, and monthly for 1 year or complete resorption of the filler. Volumetric, histologic, and statistical analyses were performed. RESULTS: Magnetic resonance imaging results validated caliper-based volumetric measurements. Histology demonstrated injections in the subcutaneous space just deep to the dermis and panniculus carnosus. High- and very high-concentration HA fillers maintained significantly greater volumes and volume ratios than low-concentration HA fillers throughout the duration of the study. CONCLUSIONS: The rat subcutis model demonstrated the ability to differentiate between HA fillers with different residence times. The caliper-based rat-subcutis method demonstrated consistent volumetric analysis and correlated with human residence times of HA fillers. These quantitative results validate the rat subcutis model as an expedited preclinical model for HA fillers.

A safe and cost-effective short hospital stay protocol to identify patients at low risk for the development of significant hypocalcemia after total thyroidectomy.

OBJECTIVE: The objective of this retrospective chart review was to determine if serial postoperative serum calcium levels early after total thyroidectomy can be used to develop an algorithm that identifies patients who are unlikely to develop significant hypocalcemia and can be safely discharged within 24 hours after surgery. METHODS: Records of 135 consecutive patients who underwent total/completion thyroidectomy and were operated on by the senior author from 2001 to 2005 have been reviewed. For the entire study group, reports of the early postoperative serum calcium levels (6 hours and 12 hours postoperatively), final thyroid pathology, preoperative examination, inpatient course, and postoperative follow up were reviewed. An endocrine medicine consultation was obtained for all patients while in the hospital after surgery. For patients who developed significant hypocalcemia, reports of their management and the need for readmission or permanent medications for hypoparathyroidism were reviewed. According to the change in serum calcium levels between 6 hours and 12 hours postoperatively, patients were divided into two groups: 1) positive slope (increasing) and 2) nonpositive (nonchanging/decreasing). RESULTS: All patients with a positive slope (50/50) did not develop significant hypocalcemia in contrast to only 59 of 85 patients (69.4%) with a nonpositive slope (P < .001, positive predictive value of positive slope in predicting freedom from significant hypocalcemia = 100%, 95% confidence interval = 92.9-100). In the nonpositive slope group, 61 patients had a serum calcium level > or =8 mg/dL at 12 hours postoperatively (< or =0.5 mg/dL below the low end of normal), and 53 (87%) of these patients remained free of significant hypocalcemia in contrast to only 6 (25%) of 24 patients with serum calcium level <8 mg/dL at 12 hours postoperatively (sensitivity = 90%, positive predictive value = 87%). In addition, of the eight patients who developed significant hypocalcemia in the nonpositive slope group with a serum calcium level > or =8 mg/dL at 12 hours postoperatively, 7 (88%) patients developed the signs and symptoms during the first 24 hours after total thyroidectomy. Readmission and permanent need for calcium supplementation happened in two patients, respectively, all with serum calcium levels <8 mg/dL at 12 hours after total thyroidectomy. The compressive and/or symptomatic large multinodular goiter as an indication for thyroidectomy was associated with developing significant hypocalcemia (P < .05). There was no statistically significant correlation between the development of significant hypocalcemia and gender, age, thyroid pathology other than goiter, or neck dissection. CONCLUSION: Patients with a positive serum calcium slope (t = 6 and 12 hours) after total thyroidectomy are safe to discharge within 24 hours after surgery with patient education with or without calcium supplementation. In addition, patients with a nonpositive slope and a serum calcium level > or =8 mg/dL at 12 hours postoperatively (< or =0.5 mg/dL below the low end of normal) are unlikely to develop significant hypocalcemia, especially beyond 24 hours postoperatively, and therefore can be safely discharged within 24 hours after total thyroidectomy with patient education and oral calcium supplementation. Our management algorithm identifies those patients at low risk of developing significant hypocalcemia early in the postoperative course after total thyroidectomy to allow for a short hospital stay and safe discharge.

The role of positron emission tomography/computed tomography in the management of recurrent papillary thyroid carcinoma.

OBJECTIVES/HYPOTHESIS: The aim of the study was to evaluate the role of combined positron emission tomography/computed tomography (PET/CT) fusion imaging in the detection and management of recurrent papillary thyroid cancer. STUDY DESIGN: A retrospective analysis of 33 patients with suspected recurrent papillary thyroid carcinoma who had undergone PET/CT was performed. PET/CT was compared with standard imaging techniques in each patient to determine whether PET/CT contributed to the therapeutic management plan. Histopathological findings were correlated to PET/CT in patients who underwent surgery. METHODS: The senior author reviewed the charts of 33 patients with recurrent papillary thyroid carcinoma to determine the impact PET/CT had on management. PET/CT was compared with conventional imaging results. In surgical patients, PET/CT was compared with histopathological findings to determine its sensitivity, specificity, accuracy, positive predictive value, and negative predictive value. RESULTS: In 67% of the cases (22 of 33), PET/CT supplied additional information that altered or confirmed the management plan. Twenty of 33 patients underwent surgery with 36 sites assessed by histopathological analysis. PET/CT correlated with histopathological findings in 25 of 36 distinct anatomical sites, with an accuracy of 70%. The sensitivity of PET/CT in identifying recurrence was found to be 66%, with a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 27%. CONCLUSION: Combined PET/CT fusion scanning was most useful in the detection and management of recurrent papillary thyroid cancer in patients who had average thyroglobulin levels greater than 10 ng/mL and when the tumor no longer concentrated radioactive iodine. In 100% of the cases in which PET/CT localized a region suspicious for malignancy, histopathological analysis confirmed the results. When PET/CT is positive, it is a powerful tool for predicting exact locations of recurrent papillary thyroid cancer, thus making it a reliable guide for surgical planning. PET/CT is a supplement to conventional imaging and fine-needle aspiration in the workup of recurrent papillary thyroid cancer. A negative finding on PET/CT is not sufficiently reliable to preclude further investigation and treatment.

Intra-articular delivery of glucosamine for treatment of experimental osteoarthritis created by a medial meniscectomy in a rat model.

Glucosamine (GlcN) is a naturally occurring amino-monosaccharide with putative chondroprotective activity. Optimum responses to GlcN are achieved at concentrations which are impractical with oral dosing. Intra-articular delivery of a bolus dose of GlcN is one way to overcome these pharmacokinetic obstacles. In this study we report the effects of exposing primary human chondrocytes to a bolus dose of GlcN. We also locally administered GlcN in the context of a meniscal transection model of rat osteoarthritis (OA). The knees of male rats were subjected to medial meniscal transection and developed arthritic changes over 4 weeks.Treatment groups were then given thrice weekly 100mL injections of 35 µg, 350 µg, 1.8 mg, or 3.5mg of GlcN dissolved in normal saline. Gross images, modified Mankin scores, and histomorphometric measurements were used as outcome measures. The 350 µg dosage of GlcN had the most significant positive impact on all components of the modified Mankin score. Together, these findings suggest the local delivery of high concentrations of GlcN is well tolerated and can suppress experimental OA through influences on both bone and cartilage.

Response to aflibercept after frequent re-treatment with bevacizumab or ranibizumab in eyes with neovascular AMD.

BACKGROUND AND OBJECTIVE: To evaluate the effects of switching to aflibercept in eyes with neovascular age-related macular degeneration (AMD) requiring frequent re-treatment with bevacizumab or ranibizumab. PATIENTS AND METHODS: Retrospective review of 73 eyes of 65 patients with neovascular AMD switched to aflibercept due to persistent or recurrent macular fluid after at least 1 year of intravitreal bevacizumab or ranibizumab with re-treatment at least every 6 weeks. Minimum post-switch follow-up was 6 months. All patients were treated using a treat-and-extend strategy. The treatment intervals immediately after and before the switch were the same. RESULTS: The mean pre-switch anti-VEGF therapy duration was 45 months, and the mean number of injections was 31. In the 6 months after the switch, the average number of injections was reduced by 0.6 compared with the 6 months before the switch (P < .001). Visual acuity was unchanged during this period (P = .78). Central retinal thickness (CRT) decreased by 19 µm after the switch (P < .001). Seventy eyes had vascularized retinal pigment epithelial detachments (PEDs). The decrease in the PED cube-root volume during the 6 months after the switch was statistically significant (-0.07 mm; P = .007). CONCLUSION: The number of injections, CRT, and PED volume decreased significantly after the switch to aflibercept, but visual acuity was unchanged.

Hypopyon and pseudoendophthalmitis 1 month after vitrectomy for retinal detachment with subretinal hemorrhage.

The presence of postoperative hypopyon warrants consideration of the diagnosis of infectious endophthalmitis, but other etiologies may mimic a hypopyon. The differential diagnosis of a postoperative hypopyon must include causes of pseudoendophthalmitis to avoid unnecessary and invasive interventions. The context and clinical presentation are the most important factors allowing such a distinction. A patient with a hypopyon and elevated intraocular pressure presented 1 month after pars plana vitrectomy for a hemorrhagic retinal detachment. Slit lamp examination disclosed khaki-colored cells layered in the anterior chamber, and a diagnosis of pseudoendophthalmitis was made. The hypopyon resolved without intervention.

Tissue engineering for in vitro analysis of matrix metalloproteinases in the pathogenesis of keloid lesions.

IMPORTANCE: Keloid lesions form because of alterations in the mechanisms that govern cutaneous wound healing. Although matrix metalloproteinases (MMPs) have been implicated in keloid pathophysiology, many questions still remain about their involvement. Our incomplete understanding of keloid pathophysiology has led to high recurrence rates in current treatments. No reliable animal model is available for studying keloids. OBJECTIVE: To gain a better understanding of the disease mechanisms involved in keloid lesions in the hopes of identifying therapeutic options. DESIGN: Fibroblasts derived from keloid tissue were incorporated in either Matrigel or polyethylene glycol diacrylate mixed with type I collagen to create 3-dimensional models to investigate the role MMPs play in keloid formation. The MMP gene expressions were also compared between fibroblasts isolated from different sites within the same keloid lesion. SETTING: The Johns Hopkins School of Medicine, Baltimore, Maryland. PARTICIPANTS: Keloid fibroblasts were received from the Baylor College of Medicine, and additional keloid fibroblasts were enzymatically isolated from the dermal layer of lesions removed from consenting patients at The Johns Hopkins Hospital. RESULTS: In the Matrigel system, MMP9 and MMP13 were observed to be significantly upregulated in keloid fibroblasts. The addition of decorin resulted in a significant decrease of type I collagen and MMP1, MMP9, and MMP13 gene expressions from keloid fibroblasts. Higher MMP gene expressions were observed in fibroblasts isolated from the margins of the original keloid wound. CONCLUSIONS AND RELEVANCE: MMP9 and MMP13 are expressed significantly more in keloid-derived cells, thus making them 2 potential targets for disease modification. Molecules that target organization of the lesion's matrix can be beneficial in downregulating increased markers during the disease. In addition, heterogeneity is observed with the varying MMP gene expressions from site-specific fibroblasts within the same keloid lesion.

An injectable adipose matrix for soft-tissue reconstruction.

BACKGROUND: Soft-tissue repair is currently limited by the availability of autologous tissue sources and the absence of an ideal soft-tissue replacement comparable to native adipose tissue. Extracellular matrix-based biomaterials have demonstrated great potential as instructive scaffolds for regenerative medicine, mechanically and biochemically defined by the tissue of origin. As such, the distinctive high lipid content of adipose tissue requires unique processing conditions to generate a biocompatible scaffold for soft-tissue repair. METHODS: Human adipose tissue was decellularized to obtain a matrix devoid of lipids and cells while preserving extracellular matrix architecture and bioactivity. To control degradation and volume persistence, the scaffold was cross-linked using hexamethylene diisocyanate and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. In vitro studies with human adipose-derived stem cells were used to assess cell viability and adipogenic differentiation on the biomaterial. In vivo biocompatibility and volume persistence were evaluated by subcutaneous implantation over 12 weeks in a small-animal model. RESULTS: The scaffold provided a biocompatible matrix supporting the growth and differentiation of adipose-derived stem cells in vitro. Cross-linking the matrix increased its resistance to enzymatic degradation. Subcutaneous implantation of the acellular adipose matrix in Sprague-Dawley rats showed minimal inflammatory reaction. Adipose tissue development and vascularization were observed in the implant, with host cells migrating into the matrix indicating the instructive potential of the matrix for guiding tissue remodeling and regeneration. CONCLUSIONS: With its unique biological and mechanical properties, decellularized adipose extracellular matrix is a promising biomaterial scaffold that can potentially be used allogenically for the correction of soft-tissue defects.

Photoactivated composite biomaterial for soft tissue restoration in rodents and in humans.

Soft tissue reconstruction often requires multiple surgical procedures that can result in scars and disfiguration. Facial soft tissue reconstruction represents a clinical challenge because even subtle deformities can severely affect an individual's social and psychological function. We therefore developed a biosynthetic soft tissue replacement composed of poly(ethylene glycol) (PEG) and hyaluronic acid (HA) that can be injected and photocrosslinked in situ with transdermal light exposure. Modulating the ratio of synthetic to biological polymer allowed us to tune implant elasticity and volume persistence. In a small-animal model, implanted photocrosslinked PEG-HA showed a dose-dependent relationship between increasing PEG concentration and enhanced implant volume persistence. In direct comparison with commercial HA injections, the PEG-HA implants maintained significantly greater average volumes and heights. Reversibility of the implant volume was achieved with hyaluronidase injection. Pilot clinical testing in human patients confirmed the feasibility of the transdermal photocrosslinking approach for implantation in abdomen soft tissue, although an inflammatory response was observed surrounding some of the materials.

A versatile pH sensitive chondroitin sulfate-PEG tissue adhesive and hydrogel.

We developed a chondroitin sulfate-polyethylene glycol (CS-PEG) adhesive hydrogel with numerous potential biomedical applications. The carboxyl groups on chondroitin sulfate (CS) chains were functionalized with N-hydroxysuccinimide (NHS) to yield chondroitin sulfate succinimidyl succinate (CS-NHS). Following purification, the CS-NHS molecule can react with primary amines to form amide bonds. Hence, using six arm polyethylene glycol amine PEG-(NH2)6 as a crosslinker we formed a hydrogel which was covalently bound to proteins in tissue via amide bonds. By varying the initial pH of the precursor solutions, the hydrogel stiffness, swelling properties, and kinetics of gelation could be controlled. The sealing/adhesive strength could also be modified by varying the damping and storage modulus properties of the material. The adhesive strength of the material with cartilage tissue was shown to be ten times higher than that of fibrin glue. Cells encapsulated or in direct contact with the material remained viable and metabolically active. Furthermore, CS-PEG material produced minimal inflammatory response when implanted subcutaneously in a rat model and enzymatic degradation was demonstrated in vitro. This work establishes an adhesive hydrogel derived from biological and synthetic components with potential application in wound healing and regenerative medicine.

Spontaneous meningoencephalocele of the temporal bone: clinical spectrum and presentation.

OBJECTIVE: To describe the clinical presentation and the radiological and surgical findings in patients with spontaneous meningoencephalocele of the temporal bone. DESIGN: Retrospective case series. SETTING: Academic, tertiary care medical center. PATIENTS: Fifteen consecutive patients with surgically confirmed meningoencephalocele of the mastoid and middle ear, without a history of trauma, tumor, cholesteatoma, or surgery of the mastoid or cranium, who were treated at our institution between January 1, 1999, and December 31, 2006. RESULTS: Ten of the 15 patients were women. Ages ranged from 31 to 77 years, with 12 patients 50 years or older. The most common presenting complaint was new-onset hearing loss in 14 patients, followed by aural fullness and headache. Cerebrospinal fluid formed an effusion in the middle ears of 13 patients and was most commonly identified when myringotomy resulted in continuous clear otorrhea. Four subjects had a history of adult-onset recurrent acute otitis media with intermittent otorrhea, which in 1 case was complicated by brain abscess. At least 1 full-thickness defect of the tegmen associated with cortical thinning of the middle fossa floor was identified in all cases on high-resolution computed tomography. At surgery, herniations of meningeal and cerebral tissue were seen through 1 (7 cases) or 2 (8 cases) defects in the middle fossa floor. Obstruction of antral aeration by the meningoencephalocele was present in all 4 cases associated with otitis media. CONCLUSIONS: The onset of otitis media, including middle ear effusions at 40 years or older, warrants the consideration of a meningoencephalocele of the ear. The appearance of tegmental defects and cortical thinning of the middle fossa floor on computed tomography provides a strong indication of the diagnosis and of the need for surgical repair.