Reconstruction of digit planer injuries using component transfer of double second toes: A case report.

The purpose of this report is to show that customized component second-toe transfers may improve functional and aesthetic outcomes following bone, soft tissue, and joint destruction of traumatically injured digits. A 22-year-old male sustained a planer injury resulting in loss of the distal volar soft tissues of the middle, ring, and small fingers, along with variable destruction of middle phalanges and distal interphalangeal joints. Simultaneous vascularized second-toe transfers were performed with customized joint and pulp reconstruction of middle and small fingers. The ring finger was salvaged using non-vascularized autologous bone graft and acellular dermal matrix. The patient had an uncomplicated postoperative course. Five-year strength, sensory and patient reported outcomes represent overall satisfactory results. Strength testing revealed the injured hand to perform within 90% strength of the uninjured side. Sensory outcomes showed present but diminished sensory perception in each of the injured digits. The patient's upper extremity function, physical health, quality of life, and foot health were overall acceptable, and he returned to using his hand for typing, writing, weight-lifting, and woodworking.

Transdermal deferoxamine prevents pressure-induced diabetic ulcers.

There is a high mortality in patients with diabetes and severe pressure ulcers. For example, chronic pressure sores of the heels often lead to limb loss in diabetic patients. A major factor underlying this is reduced neovascularization caused by impaired activity of the transcription factor hypoxia inducible factor-1 alpha (HIF-1α). In diabetes, HIF-1α function is compromised by a high glucose-induced and reactive oxygen species-mediated modification of its coactivator p300, leading to impaired HIF-1α transactivation. We examined whether local enhancement of HIF-1α activity would improve diabetic wound healing and minimize the severity of diabetic ulcers. To improve HIF-1α activity we designed a transdermal drug delivery system (TDDS) containing the FDA-approved small molecule deferoxamine (DFO), an iron chelator that increases HIF-1α transactivation in diabetes by preventing iron-catalyzed reactive oxygen stress. Applying this TDDS to a pressure-induced ulcer model in diabetic mice, we found that transdermal delivery of DFO significantly improved wound healing. Unexpectedly, prophylactic application of this transdermal delivery system also prevented diabetic ulcer formation. DFO-treated wounds demonstrated increased collagen density, improved neovascularization, and reduction of free radical formation, leading to decreased cell death. These findings suggest that transdermal delivery of DFO provides a targeted means to both prevent ulcer formation and accelerate diabetic wound healing with the potential for rapid clinical translation.

Multiple Subsets of Brain Tumor Initiating Cells Coexist in Glioblastoma.

Brain tumor-initiating cells (BTICs) are self-renewing multipotent cells critical for tumor maintenance and growth. Using single-cell microfluidic profiling, we identified multiple subpopulations of BTICs coexisting in human glioblastoma, characterized by distinct surface marker expression and single-cell molecular profiles relating to divergent bulk tissue molecular subtypes. These data suggest BTIC subpopulation heterogeneity as an underlying source of intra-tumoral bulk tissue molecular heterogeneity, and will support future studies into BTIC subpopulation-specific therapies. Stem Cells 2016;34:1702-1707.

Proximalization of the Vascularized Toe Joint in Finger Proximal Interphalangeal Joint Reconstruction: A Technique to Derive Optimal Flexion From a Joint With Expected Limited Motion.

When used to reconstruct a finger proximal interphalangeal joint, a free toe interphalangeal joint, without modification, cannot meet the motion demands of the finger to allow palm touchdown. This limitation is the direct result of the toe interphalangeal joint having an intrinsic arc of motion that delivers less flexion than that of a normal functioning finger proximal interphalangeal joint. By modifying the inset of the transferred joint to an extra-anatomical more proximal position, this limitation can be overcome. With a mathematical justification highlighted by a clinical illustration, we demonstrate the feasibility and utility of this "proximalization" technique.

The Role of Focal Adhesion Kinase in Keratinocyte Fibrogenic Gene Expression.

Abnormal skin scarring causes functional impairment, psychological stress, and high socioeconomic cost. Evidence shows that altered mechanotransduction pathways have been linked to both inflammation and fibrosis, and that focal adhesion kinase (FAK) is a key mediator of these processes. We investigated the importance of keratinocyte FAK at the single cell level in key fibrogenic pathways critical for scar formation. Keratinocytes were isolated from wildtype and keratinocyte-specific FAK-deleted mice, cultured, and sorted into single cells. Keratinocytes were evaluated using a microfluidic-based platform for high-resolution transcriptional analysis. Partitive clustering, gene enrichment analysis, and network modeling were applied to characterize the significance of FAK on regulating keratinocyte subpopulations and fibrogenic pathways important for scar formation. Considerable transcriptional heterogeneity was observed within the keratinocyte populations. FAK-deleted keratinocytes demonstrated increased expression of genes integral to mechanotransduction and extracellular matrix production, including Igtbl, Mmpla, and Col4a1. Transcriptional activities upon FAK deletion were not identical across all single keratinocytes, resulting in higher frequency of a minor subpopulation characterized by a matrix-remodeling profile compared to wildtype keratinocyte population. The importance of keratinocyte FAK signaling gene expression was revealed. A minor subpopulation of keratinocytes characterized by a matrix-modulating profile may be a keratinocyte subset important for mechanotransduction and scar formation.

Progenitor cell dysfunctions underlie some diabetic complications.

Stem cells and progenitor cells are integral to tissue homeostasis and repair. They contribute to health through their ability to self-renew and commit to specialized effector cells. Recently, defects in a variety of progenitor cell populations have been described in both preclinical and human diabetes. These deficits affect multiple aspects of stem cell biology, including quiescence, renewal, and differentiation, as well as homing, cytokine production, and neovascularization, through mechanisms that are still unclear. More important, stem cell aberrations resulting from diabetes have direct implications on tissue function and seem to persist even after return to normoglycemia. Understanding how diabetes alters stem cell signaling and homeostasis is critical for understanding the complex pathophysiology of many diabetic complications. Moreover, the success of cell-based therapies will depend on a more comprehensive understanding of these deficiencies. This review has three goals: to analyze stem cell pathways dysregulated during diabetes, to highlight the effects of hyperglycemic memory on stem cells, and to define ways of using stem cell therapy to overcome diabetic complications.

Stem Cells in Wound Healing: The Future of Regenerative Medicine? A Mini-Review.

The increased risk of disease and decreased capacity to respond to tissue insult in the setting of aging results from complex changes in homeostatic mechanisms, including the regulation of oxidative stress and cellular heterogeneity. In aged skin, the healing capacity is markedly diminished resulting in a high risk for chronic wounds. Stem cell-based therapies have the potential to enhance cutaneous regeneration, largely through trophic and paracrine activity. Candidate cell populations for therapeutic application include adult mesenchymal stem cells, embryonic stem cells and induced pluripotent stem cells. Autologous cell-based approaches are ideal to minimize immune rejection but may be limited by the declining cellular function associated with aging. One strategy to overcome age-related impairments in various stem cell populations is to identify and enrich with functionally superior stem cell subsets via single cell transcriptomics. Another approach is to optimize cell delivery to the harsh environment of aged wounds via scaffold-based cell applications to enhance engraftment and paracrine activity of therapeutic stem cells. In this review, we shed light on challenges and recent advances surrounding stem cell therapies for wound healing and discuss limitations for their clinical adoption.

Knee Donor Site Morbidity Following Harvest of Medial Femoral Trochlea Osteochondral Flaps for Carpal Reconstruction.

PURPOSE: This study examines donor site morbidity associated with the medial femoral trochlea (MFT) when used as a donor site for vascularized osteochondral flaps for reconstruction of challenging carpal defects such as proximal pole scaphoid nonunion and advanced Kienböck disease. METHODS: The retrospective study population included all patients who had undergone MFT flap harvest for scaphoid or lunate reconstruction. Chart review, patient questionnaires, and validated knee function assessment tools were used: International Knee Documentation Committee Subjective Knee Form scores ranged from 0 (maximal disability) to 100 (no disability). Western Ontario and McMaster Universities osteoarthritis index scores ranged from 0% (no disability) to 100% (maximal disability). Magnetic resonance imaging and radiographs were obtained on the donor knee on the majority of patients. RESULTS: Questionnaire response rate was 79% (45 of 57 patients). Average patient age was 35 ± 11 years (range, 19-70 years). Average postoperative follow-up was 27 ± 17 months (range, 9-108 months). The indication for MFT flap reconstruction was scaphoid nonunion in 30 patients and Kienböck disease in 15 patients. All 45 patients had a stable knee on examination. Magnetic resonance and radiographic imaging obtained on 35 patients exhibited no pathological changes. Average duration of postoperative pain was 56 ± 59 days (range, 0-360 days); average duration until patients reported the knee returning to normal was 90 ± 60 days (range, 14-360 days). Forty-three of 44 patients would have the same surgery again if needed; overall satisfaction with the surgery was rated as 5 ± 1 (range, 2-5) on a scale from 0 (no satisfaction) to 5 (maximal satisfaction). Average International Knee Documentation Committee score was 96 ± 9 (range, 56.3-100) and the average Western Ontario and McMaster Universities score was 6% ± 16% (range, 0%-68%). CONCLUSIONS: Medial femoral trochlea osteochondral flap harvest results in minimal donor site morbidity in the majority of patients. Symptoms are time limited. Intermediate-term follow-up demonstrates excellent results in subjective outcome measures. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Distally Based Iliotibial Band Flap: Anatomic Study with Surgical Considerations.

Background Reconstruction of high-risk fascia, tendon, or ligament defects may benefit from vascularized tissue. The iliotibial band (ITB), a thick fibrous tract of connective tissue, serves as a potential donor site for free tissue transfer but its blood supply has not been thoroughly investigated. The aim of this anatomical study was to investigate the vascular supply to the distal ITB and its role as a free fascial flap. Methods We dissected 16 fresh-frozen cadaveric legs and injected latex into the superolateral geniculate artery (SLGA). A distal ITB fascial flap was designed and measurements were taken for flap dimensions, pedicle length and size, and SLGA perfusion territory. Results The SLGA perfused 11.5 ± 2.3 cm of distal ITB (proximal to the lateral femoral epicondyle) and provided 6.4 ± 0.7cm of pedicle length to the ITB flap. Conclusions Chimeric options to include bone (from the lateral femoral condyle), cartilage (from the lateral femoral trochlea), muscle (from vastus lateralis or biceps femoris), and skin are possible. Surgical harvest techniques are proposed, including preservation of ITB insertions to minimize lateral knee instability. Clinical validation is needed to determine the role of the distal ITB free fascial flap in reconstructive microsurgery.

Endothelial trauma from mechanical thrombectomy in acute stroke: in vitro live-cell platform with animal validation.

BACKGROUND AND PURPOSE: Endovascular thrombectomy has shown promise for the treatment of acute strokes resulting from large-vessel occlusion. Reperfusion-related injury may contribute to the observed decoupling of angiographic and clinical outcomes. Iatrogenic disruption of the endothelium during thrombectomy is potentially a key mediator of this process that requires further study. METHODS: An in vitro live-cell platform was developed to study the effect of various commercially available endovascular devices on the endothelium. In vivo validation was performed using porcine subjects. RESULTS: This novel in vitro platform permitted high-resolution quantification and characterization of the pattern and timing of endothelial-cell injury among endovascular thrombectomy devices and vessel diameters. Thrombectomy devices displayed heterogeneous effects on the endothelium; the device performance assessed in vitro was substantiated by in vivo findings. CONCLUSIONS: In vitro live-cell artificial vessel modeling enables a detailed study of the endothelium after thrombectomy and may contribute to future device design. Large animal studies confirm the relevance of this in vitro system to investigate endothelial physiology. This artificial vessel model may represent a practical, scalable, and physiologically relevant system to assess new endovascular technologies.

Load-Dependent Emission Factors and Chemical Characteristics of IVOCs from a Medium-Duty Diesel Engine.

A detailed understanding of the climate and air quality impacts of mobile-source emissions requires the characterization of intermediate-volatility organic compounds (IVOCs), relatively-low-vapor-pressure gas-phase species that may generate secondary organic aerosol with high yields. Due to challenges associated with IVOC detection and quantification, IVOC emissions remain poorly understood at present. Here, we describe measurements of the magnitude and composition of IVOC emissions from a medium-duty diesel engine. Measurements are made on an engine dynamometer and utilize a new mass-spectrometric instrument to characterize the load dependence of the emissions in near-real-time. Results from steady-state engine operation indicate that IVOC emissions are highly dependent on engine power, with highest emissions at engine idle and low-load operation (≤25% maximum rated power) with a chemical composition dominated by saturated hydrocarbon species. Results suggest that unburned fuel components are the dominant IVOCs emitted at low loads. As engine load increases, IVOC emissions decline rapidly and become increasingly characterized by unsaturated hydrocarbons and oxygenated organics, newly formed from incomplete combustion processes at elevated engine temperatures and pressures. Engine transients, including a cold-start ignition and engine acceleration, show IVOC emission profiles that are different in amount or composition compared to steady-state combustion, underscoring the utility of characterizing IVOC emissions with high time resolution across realistic engine operating conditions. We find possible evidence for IVOC losses on unheated dilution and sampling surfaces, which need to be carefully accounted for in IVOC emission studies.

Nanotechnology in bone tissue engineering.

Nanotechnology represents a major frontier with potential to significantly advance the field of bone tissue engineering. Current limitations in regenerative strategies include impaired cellular proliferation and differentiation, insufficient mechanical strength of scaffolds, and inadequate production of extrinsic factors necessary for efficient osteogenesis. Here we review several major areas of research in nanotechnology with potential implications in bone regeneration: 1) nanoparticle-based methods for delivery of bioactive molecules, growth factors, and genetic material, 2) nanoparticle-mediated cell labeling and targeting, and 3) nano-based scaffold construction and modification to enhance physicochemical interactions, biocompatibility, mechanical stability, and cellular attachment/survival. As these technologies continue to evolve, ultimate translation to the clinical environment may allow for improved therapeutic outcomes in patients with large bone deficits and osteodegenerative diseases. FROM THE CLINICAL EDITOR: Traditionally, the reconstruction of bony defects has relied on the use of bone grafts. With advances in nanotechnology, there has been significant development of synthetic biomaterials. In this article, the authors provided a comprehensive review on current research in nanoparticle-based therapies for bone tissue engineering, which should be useful reading for clinicians as well as researchers in this field.

Lateral Femoral Condyle Flap: An Alternative Source of Vascularized Bone From the Distal Femur.

PURPOSE: To elucidate the vascular anatomy of the superolateral geniculate artery (SLGA) and its supply to the periosteum of the lateral femoral condyle (LFC) and to provide guidelines for flap design and describe an illustrative case. METHODS: Thirty-one fresh cadaveric limbs were dissected. The vascular anatomy of the SLGA and its distal branches to skin, muscle, and periosteum were identified. Fluoroscopic images were taken during continuous perfusion of a radiopaque contrast dye into the SLGA. Intra-arterial injections of latex rubber were performed in 12 cadaver limbs. The vascular territory was traced from the SLGA to its distal branches, and surrounding soft tissues were dissected. RESULTS: The SLGA originated from the popliteal artery 4.9 ± 1.2 cm (range, 2.8-7 cm) from the knee joint and its pedicle diameter was 1.8 ± 0.5 mm (range, 1-3 mm). SGLA pedicle-specific fluoroscopic angiography demonstrated a dense filigree of vessels over the lateral distal femur. Arterial latex injections confirmed that the SLGA supplied the periosteum of the LFC and distal femur shaft. The proximal-most extent of periosteal perfusion was 11.7 ± 2.1 cm (range, 9.3-14.1 cm) from the knee joint. The average pedicle length of LFC osteoperiosteal flaps was 4.8 ± 0.9 cm (range, 3.5-6.3 cm). CONCLUSIONS: The LFC flap consistently demonstrated almost 12 cm of femur length perfusion based on the SLGA pedicle. The anatomy of this flap enables chimeric designs combining soft tissue, bone, and cartilage. CLINICAL RELEVANCE: The vascularized LFC flap is an option for reconstruction of osseous defects of the upper extremity.

Soft tissue mechanotransduction in wound healing and fibrosis.

Recent evidence suggests that mechanical forces can significantly impact the biologic response to injury. Integrated mechanical and chemical signaling networks have been discovered that enable physical cues to regulate disease processes such as pathologic scar formation. Distinct molecular mechanisms control how tensional forces influence wound healing and fibrosis. Conceptual frameworks to understand cutaneous repair have expanded beyond traditional cell-cytokine models to include dynamic interactions driven by mechanical force and the extracellular matrix. Strategies to manipulate these biomechanical signaling networks have tremendous therapeutic potential to reduce scar formation and promote skin regeneration.

Loss of keratinocyte focal adhesion kinase stimulates dermal proteolysis through upregulation of MMP9 in wound healing.

OBJECTIVE: To investigate how epithelial mechanotransduction pathways impact wound repair. BACKGROUND: Mechanical forces are increasingly recognized to influence tissue repair, but their role in chronic wound pathophysiology remains unknown. Studies have shown that chronic wounds exhibit high levels of matrix metalloproteinase 9 (MMP9), a key proteolytic enzyme that regulates wound remodeling. We hypothesized that epithelial mechanosensory pathways regulated by keratinocyte-specific focal adhesion kinase (FAK) control dermal remodeling via MMP9. METHODS: A standard wound model was applied to keratinocyte-specific FAK knockout (KO) and control mice. Rates of wound healing were measured and tissue was obtained for histologic and molecular analyses. Transcriptional and immunoblot assays were used to assess the activation of FAK, intracellular kinases, and MMP9 in vitro. A cell suspension model was designed to validate the importance of FAK mechanosensing, p38, and MMP9 secretion in human cells. Biomechanical testing was utilized to evaluate matrix tensile properties in FAK KO and control wounds. RESULTS: Wound healing in FAK KO mice was significantly delayed compared with controls (closure at 15 days compared with 20 days, P = 0.0003). FAK KO wounds demonstrated decreased dermal thickness and collagen density. FAK KO keratinocytes exhibited overactive p38 and MMP9 signaling in vitro, findings recapitulated in human keratinocytes via the deactivation of FAK in the cell suspension model. Functionally, FAK KO wounds were significantly weaker and more brittle than control wounds, results consistent with the histologic and molecular analyses. CONCLUSIONS: Keratinocyte FAK is highly responsive to mechanical cues and may play a critical role in matrix remodeling via regulation of p38 and MMP9. These findings suggest that aberrant epithelial mechanosensory pathways may contribute to pathologic dermal proteolysis and wound chronicity.

A modern series of acute aortic occlusion.

OBJECTIVE: Acute aortic occlusion (AAO) is a rare condition associated with substantial morbidity and mortality. The most recent large series was published over 15 years ago and included patients from the 1980s. Previous studies reported up to 50% of AAOs are caused by embolization, with a mortality rate approaching 50%. We reviewed our recent experience with AAOs to identify current etiologies and outcomes in a contemporary series of patients with AAOs. METHODS: Current Procedural Terminology codes and data from a prospectively maintained vascular surgical database were used to identify patients with acute occlusion of the native aorta between 2005 and July 2013. AAOs secondary to trauma, dissection, or graft occlusion were excluded. RESULTS: We identified 29 patients with AAOs treated at our institution. Twenty-three patients were transferred from referring hospitals with a mean transfer time of 3.9 hours (range, 0.5-7.5 hours). Twenty-two presented with occlusion below the renal arteries and seven with occlusion extending above the renal arteries. Resting motor/sensory lower extremity deficits were noted in 17 patients. Eight patients presented with complete paraplegia. Etiology was felt to be aortoiliac thrombosis in 22 cases, embolic occlusion in 2, and indeterminate in 5. Surgical revascularization was performed in 26 cases (extra-anatomic bypass in 18, thromboembolectomy in 5, and aortobifemoral bypass in 3 patients. Three patients had no intervention. Acute renal failure developed in 15 patients and rhabomyolysis in 10 patients. Fasciotomy was performed in 19 extremities. Nine extremities were amputated in six patients. Overall mortality was 34% with a 30-day mortality of 24% and a postprocedure mortality of 15%. CONCLUSIONS: AAO is an infrequent but devastating event. The dominant etiology of AAOs is now thrombotic occlusion. Despite advances in vascular surgery and critical care over the past 2 decades, associated morbidity and mortality remain substantial with high rates of limb loss, acute renal failure, rhabdomyolysis, and death. Mortality may be improved with expeditious extra-anatomic bypass.

Paroxysmal nocturnal hemoglobinuria: a red clot syndrome.

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired, nonmalignant disorder of hematopoietic stem cells characterized by hemolysis, diminished hematopoiesis, and thrombophilia. We describe a 65-year-old woman with known PNH and peripheral arterial disease who presented with critical limb ischemia and a nonhealing left foot ulcer. She underwent surgical bypass of a diffusely diseased left superficial femoral artery with autologous reversed saphenous vein graft. Her postoperative course was complicated by wound sepsis and PNH exacerbation with resultant graft thrombosis requiring an above-knee amputation. This case highlights several key concepts relevant to the management of vascular surgery patients with PNH: (1) their predisposition for arterial and venous thrombosis; (2) hypercoagulability despite standard anticoagulation regimens; (3) the role of eculizumab (a monoclonal antibody that inhibits complement activation used to treat PNH) in reducing thrombotic complications and hemolysis; and (4) complications associated with the immunosuppressive effects of eculizumab. We recommend careful monitoring of hemolysis and immunosuppression, aggressive anticoagulation, frequent graft surveillance, and early consultation with hematology.

The role of focal adhesion complexes in fibroblast mechanotransduction during scar formation.

Historically, great efforts have been made to elucidate the biochemical pathways that direct the complex process of wound healing; however only recently has there been recognition of the importance that mechanical signals play in the process of tissue repair and scar formation. The body's physiologic response to injury involves a dynamic interplay between mechanical forces and biochemical cues which directs a cascade of signals leading ultimately to the formation of fibrotic scar. Fibroblasts are a highly mechanosensitive cell type and are also largely responsible for the generation of the fibrotic matrix during scar formation and are thus a critical player in the process of mechanotransduction during tissue repair. Mechanotransduction is initiated at the interface between the cell membrane and the extracellular matrix where mechanical signals are first translated into a biochemical response. Focal adhesions are dynamic multi-protein complexes through which the extracellular matrix links to the intracellular cytoskeleton. These focal adhesion complexes play an integral role in the propagation of this initial mechanical cue into an extensive network of biochemical signals leading to widespread downstream effects including the influx of inflammatory cells, stimulation of angiogenesis, keratinocyte migration, fibroblast proliferation and collagen synthesis. Increasing evidence has demonstrated the importance of the biomechanical milieu in healing wounds and suggests that an integrated approach to the discovery of targets to decrease scar formation may prove more clinically efficacious than previous purely biochemical strategies.

Transcriptional profiling of rapamycin-treated fibroblasts from hypertrophic and keloid scars.

Excess scar formation after cutaneous injury can result in hypertrophic scar (HTS) or keloid formation. Modern strategies to treat pathologic scarring represent nontargeted approaches that produce suboptimal results. Mammalian target of rapamycin (mTOR), a central mediator of inflammation, has been proposed as a novel target to block fibroproliferation. To examine its mechanism of action, we performed genomewide microarray on human fibroblasts (from normal skin, HTS, and keloid scars) treated with the mTOR inhibitor, rapamycin. Hypertrophic scar and keloid fibroblasts demonstrated overexpression of collagen I and III that was effectively abrogated with rapamycin. Blockade of mTOR specifically impaired fibroblast expression of the collagen biosynthesis genes PLOD, PCOLCE, and P4HA, targets significantly overexpressed in HTS and keloid scars. These data suggest that pathologic scarring can be abrogated via modulation of mTOR pathways in procollagen and collagen processing.

Functional reconstruction of subtotal thumb metacarpal defect with a vascularized medial femoral condyle flap: case report.

Devastating hand injuries require customized reconstructive strategies to maximize functional outcomes. We report a case of thumb metacarpal reconstruction using a vascularized medial femoral condyle osteocutaneous flap in the setting of nearly complete metacarpal loss. In addition to achieving the traditional goals of reconstructing thumb length and providing stability, the medial femoral condyle flap allowed motion at the carpometacarpal joint. The patient's hand function was further optimized by a component transfer of a proximally injured but distally preserved index finger to the amputated middle finger position. The patient regained satisfactory grip and thumb function with minimal donor site morbidity. This case highlights the role of both creative and established approaches to reconstruct composite tissues following devastating hand injury.