Del1 Is a Growth Factor for Skeletal Progenitor Cells in the Fracture Callus.

Failure to properly form bone or integrate surgical implants can lead to morbidity and additional surgical interventions in a significant proportion of orthopedic surgeries. While the role of skeletal stem cells (SSCs) in bone formation and repair is well-established, very little is known about the factors that regulate the downstream Bone, Cartilage, Stromal, Progenitors (BCSPs). BCSPs, as transit amplifying progenitor cells, undergo multiple mitotic divisions to expand the pool of lineage committed progenitors allowing stem cells to preserve their self-renewal and stemness. Del1 is a protein widely expressed in the skeletal system, but its deletion led to minimal phenotype changes in the uninjured mouse. In this paper, we demonstrate that Del1 is a key regulator of BCSP expansion following injury. In Del1 knockout mice, there is a significant reduction in the number of BCSPs which leads to a smaller callus and decreased bone formation compared with wildtype (WT) littermates. Del1 serves to promote BCSP proliferation and prevent apoptosis in vivo and in vitro. Moreover, exogenous Del1 promotes proliferation of aged human BCSPs. Our results highlight the potential of Del1 as a therapeutic target for improving bone formation and implant success. Del1 injections may improve the success of orthopedic surgeries and fracture healing by enhancing the proliferation and survival of BCSPs, which are crucial for generating new bone tissue during the process of bone formation and repair.

Sexually dimorphic estrogen sensing in skeletal stem cells controls skeletal regeneration.

Sexually dimorphic tissues are formed by cells that are regulated by sex hormones. While a number of systemic hormones and transcription factors are known to regulate proliferation and differentiation of osteoblasts and osteoclasts, the mechanisms that determine sexually dimorphic differences in bone regeneration are unclear. To explore how sex hormones regulate bone regeneration, we compared bone fracture repair between adult male and female mice. We found that skeletal stem cell (SSC) mediated regeneration in female mice is dependent on estrogen signaling but SSCs from male mice do not exhibit similar estrogen responsiveness. Mechanistically, we found that estrogen acts directly on the SSC lineage in mice and humans by up-regulating multiple skeletogenic pathways and is necessary for the stem cell's ability to self- renew and differentiate. Our results also suggest a clinically applicable strategy to accelerate bone healing using localized estrogen hormone therapy.

A deep learning model for burn depth classification using ultrasound imaging.

Identification of burn depth with sufficient accuracy is a challenging problem. This paper presents a deep convolutional neural network to classify burn depth based on altered tissue morphology of burned skin manifested as texture patterns in the ultrasound images. The network first learns a low-dimensional manifold of the unburned skin images using an encoder-decoder architecture that reconstructs it from ultrasound images of burned skin. The encoder is then re-trained to classify burn depths. The encoder-decoder network is trained using a dataset comprised of B-mode ultrasound images of unburned and burned ex vivo porcine skin samples. The classifier is developed using B-mode images of burned in situ skin samples obtained from freshly euthanized postmortem pigs. The performance metrics obtained from 20-fold cross-validation show that the model can identify deep-partial thickness burns, which is the most difficult to diagnose clinically, with 99% accuracy, 98% sensitivity, and 100% specificity. The diagnostic accuracy of the classifier is further illustrated by the high area under the curve values of 0.99 and 0.95, respectively, for the receiver operating characteristic and precision-recall curves. A post hoc explanation indicates that the classifier activates the discriminative textural features in the B-mode images for burn classification. The proposed model has the potential for clinical utility in assisting the clinical assessment of burn depths using a widely available clinical imaging device.

Safety profile of atorvastatin in the role of burn wound injury conversion.

BACKGROUND: Atorvastatin could be beneficial in the treatment of burn patients to prevent burn wound progression from partial to full thickness. Our primary aim is to evaluate the safety of atorvastatin in burn patients. METHODS: Single center retrospective chart review of burn patients receiving atorvastatin during admission May 2016-May 2019 with historic controls was performed. Demographics, burn total body surface area, atorvastatin doses, creatinine phosphokinase, aspartate aminotransferase levels and adverse events were analyzed. RESULTS: 48 burn patients received atorvastatin during admission. Nine patients experienced elevated CK or AST levels during admission, but did not correlate with timing of atorvastatin administration and were comparable to levels in control patients. No adverse events associated with atorvastatin were identified. CONCLUSIONS: Atorvastatin administered to patients with burn injuries was not associated with any adverse events or attributable lab abnormalities. We believe that atorvastatin is safe to use in patients with burns and can be safely studied to determine the drug's effect on the prevention of burn wound conversion.

Real-time Burn Classification using Ultrasound Imaging.

This article presents a real-time approach for classification of burn depth based on B-mode ultrasound imaging. A grey-level co-occurrence matrix (GLCM) computed from the ultrasound images of the tissue is employed to construct the textural feature set and the classification is performed using nonlinear support vector machine and kernel Fisher discriminant analysis. A leave-one-out cross-validation is used for the independent assessment of the classifiers. The model is tested for pair-wise binary classification of four burn conditions in ex vivo porcine skin tissue: (i) 200 °F for 10 s, (ii) 200 °F for 30 s, (iii) 450 °F for 10 s, and (iv) 450 °F for 30 s. The average classification accuracy for pairwise separation is 99% with just over 30 samples in each burn group and the average multiclass classification accuracy is 93%. The results highlight that the ultrasound imaging-based burn classification approach in conjunction with the GLCM texture features provide an accurate assessment of altered tissue characteristics with relatively moderate sample sizes, which is often the case with experimental and clinical datasets. The proposed method is shown to have the potential to assist with the real-time clinical assessment of burn degrees, particularly for discriminating between superficial and deep second degree burns, which is challenging in clinical practice.

DEL1 protects against chondrocyte apoptosis through integrin binding.

BACKGROUND: Osteoarthritis (OA) is a debilitating disease process, affecting mobility and overall health of millions. Current treatment is for symptomatic relief and discovery of approaches to halt or reverse damage is imperative. Deletion of developmental endothelial locus-1 (Del1) has been shown to increase severity of OA in knockout mice. We examined the intracellular pathways involved in the ability of DEL1 to protect chondrocytes from apoptosis and anoikis and hypothesized that it functioned via integrin signaling. MATERIALS AND METHODS: Primary human chondrocytes were treated with various inducers of apoptosis, including anoikis, in the presence of added DEL1 or bovine serum albumin as control. Various inhibitors of integrin binding were examined for their effect on DEL1 activity. Downstream signaling pathway components were detected by immunoblotting. RESULTS: The addition of DEL1 protected chondrocytes from multiple inducers of apoptosis as measured by cell survival, terminal deoxynucleotidyl transferase dUTP nick end labeling and caspase 3/7 assays (P < 0.05). The effect of DEL1 was blocked by RGD peptides and by antibodies directed to integrin αVß3, but not by controls or antibody to integrin α1 (P < 0.05). Treatment with DEL1 promoted ERK and AKT activation when cells were attached, but only AKT activation under conditions of anoikis. CONCLUSIONS: DEL1 protected chondrocytes from apoptosis in response to activators of either the intrinsic or extrinsic pathways, and to anoikis. This effect was mediated primarily through integrin αVß3. This represents a therapeutic target for therapies to prevent cartilage degeneration in OA.

Review of the Current Management of Pressure Ulcers.

Significance: The incidence of pressure ulcers is increasing due to our aging population and the increase in the elderly living with disability. Learning how to manage pressure ulcers appropriately is increasingly important for all professionals in wound care. Recent Advances: Many new dressings and treatment modalities have been developed over the recent years and the goal of this review is to highlight their benefits and drawbacks to help providers choose their tools appropriately. Critical Issues: Despite an increased number of therapies available on the market, none has demonstrated any clear benefit over the others and pressure ulcer treatment remains frustrating and time-consuming. Future Directions: Additional research is needed to develop products more effective in prevention and treatment of pressure ulcers.

Laboratory Models for the Study of Normal and Pathologic Wound Healing.

Current knowledge of wound healing is based on studies using various in vitro and in vivo wound models. In vitro models allow for biological examination of specific cell types involved in wound healing. In vivo models generally provide the full spectrum of biological responses required for wound healing, including inflammation and angiogenesis, and provide cell-cell interactions not seen in vitro. In this review, the authors aim to delineate the most relevant wound healing models currently available and to discuss their strengths and limitations in their approximation of the human wound healing processes to aid scientists in choosing the most appropriate wound healing models for designing, testing, and validating their experiments.

Inhibition of IRE1 results in decreased scar formation.

Wound healing is characterized by the production of large amounts of protein necessary to replace lost cellular mass and extracellular matrix. The unfolded protein response (UPR) is an important adaptive cellular response to increased protein synthesis. One of the main components of the UPR is IRE1, an endoplasmic reticulum transmembrane protein with endonuclease activity that produces the activated form of the transcription factor XBP1. Using luciferase reporter mice for Xbp1 splicing, we showed that IRE1 was up-regulated during excisional wound healing at the time in wound healing consistent with that of the proliferative phase, when the majority of protein synthesis for cellular proliferation and matrix deposition occurs. Furthermore, using a small molecule inhibitor of IRE1 we demonstrated that inhibition of IRE1 led to decreased scar formation in treated mice. Results were recapitulated in a hypertrophic scar mouse model. These data help provide a cellular pathway to target in the treatment of hypertrophic scarring and keloid disorders.

A Novel Three-Dimensional Platform to Investigate Neoangiogenesis, Transendothelial Migration, and Metastasis of MDAMB-231 Breast Cancer Cells.

BACKGROUND: A crucial step in the progression of cancer involves the transendothelial migration of tumor cells into the bloodstream and invasion at distant sites. Most in vitro models of malignant cell behavior do not account for the presence of and interaction with vascular cells. Three-dimensional platforms to further explore the factors responsible for metastatic cellular behavior are under intensive investigation. METHODS: Hydrogels with encapsulated MDAMB-231 breast cancer cells were fabricated with a central microchannel. The microchannel was lined with a co-culture of human umbilical vein endothelial cells and human aortic smooth muscle cells. For comparison, co-culture-seeded microchannels without breast cancer cells (MDAMB-negative) were fabricated. RESULTS: After 7 and 14 days, the endoluminal lining of encapsulated MDAMB-231 co-culture-seeded microchannels demonstrated aberrant endothelial cell and smooth muscle cell organization and breast cancer cell transendothelial migration. MDAMB-231 cells performed matrix remodeling, forming tumor aggregates within the bulk, migrating preferentially toward the hydrogel "neovessel." In contrast, MDAMB-negative constructs demonstrated maintenance of an intact endoluminal lining composed of endothelial cells and smooth muscle cells that organized into discrete layers. Furthermore, the thicknesses of the endoluminal lining of MDAMB-negative constructs were significantly greater than encapsulated MDAMB-231 co-culture-seeded constructs after 7 and 14 days (p = 0.012 and p < 0.001, respectively). CONCLUSION: The authors have created a powerful tool that may have tremendous impact on furthering our understanding of cancer recurrence and metastasis, shedding light on these poorly understood phenomena.

Perioperative Antibiotics in the Setting of Oropharyngeal Reconstruction: Less Is More.

BACKGROUND: Recipient-site infection after oropharyngeal reconstruction is a potentially disastrous complication. Although studies suggest that perioperative antibiotics reduces infection rates in these patients from 87% to 20%, there is no consensus regarding what constitutes the most appropriate antibiotic regimen and duration of treatment. METHODS: A retrospective review of perioperative antibiotic administration was performed of all patients who underwent local, pedicled, or free flap oropharyngeal reconstruction after oncologic resection by a single surgeon at a single institution between 2007 and 2013 to assess for recipient-site complications. RESULTS: Ninety-seven patients underwent 100 reconstructions (61 free flap reconstructions, 39 pedicled/local flap reconstructions) and all received a combination of intravenous (IV) antibiotic agents designed to cover oral flora. There were 23 (23%) recipient-site complications, which included cellulitis (9%), mucocutaneous fistula (5%), abscess (5%), and wound dehiscence (4%). Duration of antibiotic prophylaxis, defined as less than 48 hours (short-course) or greater than 48 hours (long-course), was not a significant predictor of recipient-site complication. Significant risk factors for recipient-site complications were clindamycin prophylaxis (P < 0.008), increased duration of surgery (P < 0.047), and advanced age (P < 0.034). Recipient-site complication was found to be a significant predictor of both increased length of hospital stay (P < 0.001) and increased time to the resumption of enteral feeds (P < 0.035). CONCLUSIONS: These data suggest that extended courses of perioperative antibiotics do not confer additional benefits in patients undergoing oropharyngeal reconstruction. We recommend a limited 48-hour course of prophylactic antibiotics with sufficient aerobic and anaerobic coverage to help minimize the incidence of antibiotic-related morbidities.

Reduction of suture associated inflammation after 28 days using novel biocompatible pseudoprotein poly(ester amide) biomaterials.

Sutures elicit an inflammatory response, which may impede the healing process and result in wound complications. We recently reported a novel family of biocompatible, biodegradable polymers, amino acid-based poly(ester amide)s (AA-PEA), which we have shown to significantly attenuate the foreign body inflammatory response in vitro. Two types of AA-PEA (Phe-PEA and Arg-Phe-PEA) were used to coat silk or plain-gut sutures, which were implanted in the gluteus muscle of C57BL/6 mice, while the uncoated control sutures were implanted in the contralateral side. After 3, 7, 14, and 28 days the mean area of inflammation surrounding the sutures was compared. Phe-PEA coating of silk sutures significantly decreased inflammation compared with noncoated controls (67.8 ± 17.4% after 3d [p = 0.0014], 51.6 ± 7.2% after 7d [p < 0.001], and 37.3 ± 8.3% after 28d [p = 0.0001]) when assessed via analysis of photomicrographs using digital image software. Phe-PEA coated plain-gut sutures were similarly assessed and demonstrated a significant decrease in the mean area of inflammation across all time points (54.1 ± 8.3% after 3 d, 41.4 ± 3.9% after 7 d, 71.5 ± 8.1% after 14 d, 78.4 ± 8.5%, and after 28 d [all p < 0.0001]). Arg-Phe-PEA coated silk demonstrated significantly less inflammation compared to noncoated controls (61.3 ± 9.4% after 3 d, 44.7 ± 4.7% after 7 d, 19.6 ± 8%, and 38.3 ± 6.8% after 28 d [all p < 0.0001]), as did coated plain-gut (37.4 ± 8.3% after 3 d [p = 0.0004], 55.0 ± 7.8% after 7 d [p < 0.0001], 46.0 ± 4.6% after 14 d [p < 0.0001], and 59.0 ± 7.9% after 28 d [p < 0.0001]). Both Phe-PEA and Arg-Phe-PEA coatings significantly decrease the inflammatory response to sutures in vivo for up to 28 days.

Prophylactic plastic surgery closure of neurosurgical scalp incisions reduces the incidence of wound complications in previously-operated patients treated with bevacizumab (Avastin®) and radiation.

Neurosurgical craniotomy, craniectomy, or other trans-galeal interventions are performed for a variety of indications, including the resection of benign or malignant tumors, hematoma evacuation, and for the management of intractable seizure disorders. Despite an overall low complication rate of intervention, wound healing complications such as dehiscence, surgical site infection, and cerebrospinal fluid leak are not uncommon. A retrospective review was performed of all patients who underwent scalp incision closure at a single institution by a single plastic surgeon between 2006 and 2013. Sixty patients (83 procedures) were included in the study. Fifty-seven patients (95.0 %) underwent previous craniotomy, craniectomy, or other trans-galeal procedure. Of the total 60 patients, 35 patients received preoperative radiation. Sixteen patients received bevacizumab prior to their index case, while 12 received bevacizumab postoperatively. Ten patients (16.7 %) required additional plastic surgical intervention for wound complications after their index plastic surgery procedure. Plastic surgery was consulted prophylactically in 34 patients (38 procedures). When plastic surgery was consulted prophylactically, 4 patients (11.8 %) required further wound revision. None of the 14 patients who underwent prophylactic plastic surgery closure for previous scalp incision, preoperative bevacizumab, and XRT administration required re-intervention. Plastic surgery closure of complex scalp incisions reduces the incidence of wound complications among patients who underwent previous neurosurgical intervention, XRT administration, and preoperative bevacizumab administration. This is particularly true when plastic surgery closure is performed "prophylactically." Further collaboration between the neurosurgical and plastic surgery teams is therefore warranted, particularly in the setting of these high-risk cases.

Fabrication and in vivo microanastomosis of vascularized tissue-engineered constructs.

Tissue engineering endeavors to create replacement tissues and restore function that may be lost through infection, trauma, and cancer. However, wide clinical application of engineered scaffolds has yet to come to fruition due to inadequate vascularization. Here, we fabricate hydrogel constructs using Pluronic(®) F127 as a sacrificial microfiber, creating microchannels within biocompatible, biodegradable type I collagen matrices. Microchannels were seeded with human umbilical vein endothelial cells (HUVEC) or HUVEC and human aortic smooth muscle cells (HASMC) in co-culture, generating constructs with an internal endothelialized microchannel. Histological analysis demonstrated HASMC/HUVEC-seeded constructs with a confluent lining after 7 days with preservation and further maturation of the lining after 14 days. Immunohistochemical staining demonstrated von Willebrand factor and CD31(+) endothelial cells along the luminal surface (neointima) and alpha-smooth muscle actin expressing smooth muscle cells in the subendothelial plane (neomedia). Additionally, the deposition of extracellular matrix (ECM) components, heparan sulfate and basal lamina collagen IV were detected after 14 days of culture. HUVEC-only- and HASMC/HUVEC-seeded microchannel-containing constructs were microsurgically anastomosed to rat femoral artery and vein and perfused, in vivo. Both HUVEC only and HUVEC/HAMSC-seeded constructs withstood physiologic perfusion pressures while their channels maintained their internal infrastructure. In conclusion, we have synthesized and performed microvascular anastomosis of tissue-engineered hydrogel constructs. This represents a significant advancement toward the generation of vascularized tissues and brings us closer to the fabrication of more complex tissues and solid organs for clinical application.