Flexor tendon injuries: Repair & Rehabilitation

Flexor tendon injuries are common and occur mostly by penetrating trauma. Suspected flexor tendon injuries require a thorough clinical assessment and often are not isolated injuries. A detailed understanding of flexor tendon anatomy and spatial relationships is essential, especially when repairing multi-tendon injuries. Principles of flexor tendon repair include a strong suture construct, minimising gap formation between tendon ends, preserving tendon blood supply and providing a smooth repair interface. Moreover, adequate exposure of the zone of injury using full-thickness skin flaps and preservation of neurovascular and pulley structures is essential. In this article an overview of contemporary management strategies is presented. Today's hand surgeons and therapists can choose from a variety of treatment options when managing these important and potentially life-changing injuries.

Embryonic stem cell extracts improve wound healing in diabetic mice

AIMS/HYPOTHESIS

Impaired wound healing significantly impacts morbidity and mortality in diabetic patients, necessitating the development of novel treatments to improve the wound healing process. We here investigated the topical use of acellular embryonic stem cell extracts (EXTs) in wound healing in diabetic db/db mice.

METHODS

Wounds were induced in diabetic db/db mice, which were subsequently treated with EXTs, with 3T3 fibroblast cell line protein extracts (3T3XTs) or with saline as a control. Pathology and mechanistic assays were then performed.

RESULTS

The in vivo topical administration of EXTs facilitates wound closure, contraction and re-epithelialization. Moreover, EXTs reduced the number of wound-infiltrating CD45⁺ inflammatory cells and increased the rate of repair and of angiogenesis as compared to controls. Interestingly, the EXT effect was partly enhanced by the use of a collagen-based biocompatible scaffold. In vivo, topical administration of EXTs increased the percentage of regulatory T cells in the wounded tissue, while in vitro EXT treatment reduced T cell-mediated IFN-γ production. Proteomic screening revealed 82 proteins differentially segregating in EXTs as compared to 3T3 extracts, with APEX1 identified as a key player for the observed immunomodulatory effect of EXTs.

CONCLUSIONS

EXTs are endowed with immunoregulatory and anti-inflammatory properties; their use improves wound healing in diabetic preclinical models.

Overexpressing IRS1 in Endothelial Cells Enhances Angioblast Differentiation and Wound Healing in Diabetes and Insulin Resistance

The effect of enhancing insulin's actions in endothelial cells (ECs) to improve angiogenesis and wound healing was studied in obesity and diabetes. Insulin receptor substrate 1 (IRS1) was overexpressed in ECs using the VE-cadherin promoter to create ECIRS1 TG mice, which elevated pAkt activation and expressions of vascular endothelial growth factor (VEGF), Flk1, and VE-cadherin in ECs and granulation tissues (GTs) of full-thickness wounds. Open wound and epithelialization rates and angiogenesis significantly improved in normal mice and high fat (HF) diet-induced diabetic mice with hyperinsulinemia in ECIRS1 TG versus wild type (WT), but not in insulin-deficient diabetic mice. Increased angioblasts and EC numbers in GT of ECIRS1 mice were due to proliferation in situ rather than uptake. GT in HF-fed diabetic mice exhibited parallel decreases in insulin and VEGF-induced pAkt and EC numbers by >50% without changes in angioblasts versus WT mice, which were improved in ECIRS1 TG mice on normal chow or HF diet. Thus, HF-induced diabetes impaired angiogenesis by inhibiting insulin signaling in GT to decrease the differentiation of angioblasts to EC, which was normalized by enhancing insulin's action targeted to EC, a potential target to improve wound healing in diabetes and obesity.

Hyperspectral Imaging as an Early Biomarker for Radiation Exposure and Microcirculatory Damage

Background

Radiation exposure can lead to detrimental effects in skin microcirculation. The precise relationship between radiation dose received and its effect on cutaneous perfusion still remains controversial. Previously, we have shown that hyperspectral imaging (HSI) is able to demonstrate long-term reductions in cutaneous perfusion secondary to chronic microvascular injury. This study characterizes the changes in skin microcirculation in response to varying doses of ionizing radiation and investigates these microcirculatory changes as a possible early non-invasive biomarker that may correlate with the extent of long-term microvascular damage.

Methods

Immunocompetent hairless mice (n = 66) were exposed to single fractions of superficial beta-irradiation in doses of 0, 5, 10, 20, 35, or 50 Gy. A HSI device was utilized to measure deoxygenated hemoglobin levels in irradiated and control areas. HSI measurements were performed at baseline before radiation exposure and for the first 3 days post-irradiation. Maximum macroscopic skin reactions were graded, and histological assessment of cutaneous microvascular densities at 4 weeks post-irradiation was performed in harvested tissue by CD31 immunohistochemistry.

Results

CD31 immunohistochemistry demonstrated a significant correlation (r = 0.90, p < 0.0001) between dose and vessel density reduction at 4 weeks. Using HSI analysis, early changes in deoxygenated hemoglobin levels were observed during the first 3 days post-irradiation in all groups. These deoxygenated hemoglobin changes varied proportionally with dose (r = 0.98, p < 0.0001) and skin reactions (r = 0.98, p < 0.0001). There was a highly significant correlation (r = 0.91, p < 0.0001) between these early changes in deoxygenated hemoglobin and late vascular injury severity assessed at the end of 4 weeks.

Conclusion

Radiation dose is directly correlated with cutaneous microvascular injury severity at 4 weeks in our model. Early post-exposure measurement of cutaneous deoxygenated hemoglobin levels may be a useful biomarker for radiation dose reconstruction and predictor for chronic microvascular injury.

Mechanoregulation of Angiogenesis in Wound Healing

Significance: Mechanical forces are important regulators of cell and tissue function. Endothelial cells proliferate in response to tissue stretch and the mechanical properties of the environment direct capillary sprouting and growth. As the vascular network is a key factor in physiology and disease, control of the vascularity by means of mechanical forces could lead to the development of innovative therapeutic strategies. Recent Advances: Increased understanding of mechanobiology has stimulated translational research and allowed the development and optimization of clinical devices that exploit mechanical forces for the treatment of diseases, in particular in the field of wound healing. Stretching in distraction osteogenesis and tissue expansion induces neogenesis of well-vascularized tissues. In micro-deformational wound therapy, micro-mechanical distortions of the wound bed stimulate cell proliferation and angiogenesis by stretching resident cells to improve healing of difficult wounds. Relief from tension antagonizes proliferation and angiogenesis in primarily closed wounds allowing for better scar quality. Critical Issues: The integration of mechanobiology into traditional cell biology and pathophysiology in general is not yet complete and further research is needed to fill existing gaps, in particular in the complexity of in vivo conditions. Future Directions: Still largely unexplored approaches based on mechanical perturbation of the micro-/macro-environment can be devised to overcome the limits of current strategies in a broad spectrum of clinical conditions.

Diffusion and perfusion: the keys to fat grafting

BACKGROUND

Fat grafting is now widely used in plastic surgery. Long-term graft retention can be unpredictable. Fat grafts must obtain oxygen via diffusion until neovascularization occurs, so oxygen delivery may be the overarching variable in graft retention.

METHODS

We studied the peer-reviewed literature to determine which aspects of a fat graft and the microenvironment surrounding a fat graft affect oxygen delivery and created 3 models relating distinct variables to oxygen delivery and graft retention.

RESULTS

Our models confirm that thin microribbons of fat maximize oxygen transport when injected into a large, compliant, well-vascularized recipient site. The "Microribbon Model" predicts that, in a typical human, fat injections larger than 0.16 cm in radius will have a region of central necrosis. Our "Fluid Accommodation Model" predicts that once grafted tissues approach a critical interstitial fluid pressure of 9 mm Hg, any additional fluid will drastically increase interstitial fluid pressure and reduce capillary perfusion and oxygen delivery. Our "External Volume Expansion Effect Model" predicts the effect of vascular changes induced by preoperative external volume expansion that allow for greater volumes of fat to be successfully grafted.

CONCLUSIONS

These models confirm that initial fat grafting survival is limited by oxygen diffusion. Preoperative expansion increases oxygen diffusion capacity allowing for additional graft retention. These models provide a scientific framework for testing the current fat grafting theories.

Development of mast cells and importance of their tryptase and chymase serine proteases in inflammation and wound healing

Mast cells (MCs) are active participants in blood coagulation and innate and acquired immunity. This review focuses on the development of mouse and human MCs, as well as the involvement of their granule serine proteases in inflammation and the connective tissue remodeling that occurs during the different phases of the healing process of wounded skin and other organs. The accumulated data suggest that MCs, their tryptases, and their chymases play important roles in tissue repair. While MCs initially promote healing, they can be detrimental if they are chronically stimulated or if too many MCs become activated at the same time. The possibility that MCs and their granule serine proteases contribute to the formation of keloid and hypertrophic scars makes them potential targets for therapeutic intervention in the repair of damaged skin.

"Synchronous" multifocal necrotizing fasciitis

BACKGROUND

Necrotizing fasciitis (NF) is an infection of the soft tissue, and is fatal if not promptly and aggressively treated. Although it is rare, it is not exceptional; nevertheless, its presentation may be misleading and may delay the diagnosis. We highlight the possible synchronous development of NF in multiple noncontiguous areas.

CASE REPORT

A 44-year-old diabetic man with no history of trauma complained of nonspecific lower back pain, which he treated with analgesics and oral antibiotics. Erythema at the left arm appeared, and the general condition worsened. The patient was admitted to the Emergency Department, and NF was diagnosed at the right gluteus and left arm.

CONCLUSION

"Synchronous" multifocality is not an expected presentation of NF, and it complicates the diagnosis and delays treatment, with a potentially negative impact on outcome.

Therapeutic effects of pregnancy on a chronic skin ulcer

OBJECTIVES

Sex hormones strongly influence skin physiology and evidences suggest wound healing as well. Estrogens establish a prohealing setting, and androgens play an antagonist role.

METHODS AND RESULTS

We present the case of a young woman in whom pregnancy with its associated hormonal shifts allowed the spontaneous healing of a chronic wound on the left leg with bone exposure, which had followed a car accident and had resisted medical and surgical treatments for 5 years.

DISCUSSION

Systemic or topical estrogens may offer alternative options in the therapy of chronic wounds, in particular in the elderly adults who have physiologically reduced estrogens levels.

Decellularized omentum as novel biologic scaffold for reconstructive surgery and regenerative medicine

Homologous tissues, such as adipose tissue, may be an interesting source of acellular scaffolds, maintaining a complex physiological three-dimensional (3D) structure, to be recellularized with autologous cells. The aim of the present work is to evaluate the possibility of obtaining homologous acellular scaffolds from decellularization of the omentum, which is known to have a complex vascular network. Adult rat and human omenta were treated with an adapted decellularization protocol involving mechanical rupture (freeze-thaw cycles), enzymatic digestion (trypsin, lipase, deoxyribonuclease, ribonuclease) and lipid extraction (2-propanol). Histological staining confirmed the effectiveness of decellularization, resulting in cell-free scaffolds with no residual cells in the matrix. The complex 3D networks of collagen (azan-Mallory), elastic fibers (Van Gieson), reticular fibers and glycosaminoglycans (PAS) were maintained, whereas Oil Red and Sudan stains showed the loss of lipids in the decellularized tissue. The vascular structures in the tissue were still visible, with preservation of collagen and elastic wall components and loss of endothelial (anti-CD31 and -CD34 immunohistochemistry) and smooth muscle (anti-alpha smooth muscle actin) cells. Fat-rich and well vascularized omental tissue may be decellularized to obtain complex 3D scaffolds preserving tissue architecture potentially suitable for recellularization. Further analyses are necessary to verify the possibility of recolonization of the scaffold by adipose-derived stem cells in vitro and then in vivo after re implantation, as already known for homologus implants in regenerative processes.

Mechanisms of action of microdeformational wound therapy

Microdeformational Wound Therapy (MDWT) is a class of medical devices that have revolutionized the treatment of complex wounds over the last 20 years. These devices, are a subset of Negative Pressure Wound Therapy (NPWT), in which there is a highly porous interface material placed between the wound and a semi-occlussive dressing and connected to suction. The porous interface material acts to deform the wound on a micro scale promoting cellular proliferation. These devices appear to significantly improve the speed of healing in many wounds, facilitate granulation tissue formation and reduce the complexity of subsequent reconstructive operations. The mechanisms through which such effects are obtained are beginning to be better understood through basic research and clinical trials. Further work in this field is likely to yield devices that are designed to treat specific wound types.

Malignant Glomus Tumor of the Leg Developed in the Context of a Superficial Typical Glomus Tumor

A 41-year-old man presented with a 2-cm painful subcutaneous nodule in his right leg, which had been present for more than 10 years and was recently enlarging. Histologically, the tumor was composed of sheets and nests of cells with variable cytomorphology, including typical round/ovoid glomus cells with clear cytoplasm and well-defined borders, small cells, and spindle cells. Numerous medium to large vessels were present. Nodules with moderate to high cellularity, nuclear atypia, and frequent mitotic figures (42 per 50 high-power fields) were noted. Immunohistochemistry showed cytoplasmic and membranous expression of smooth-muscle actin, vimentin, and membranous expression of type IV collagen. Whereas superficiality, dimensions, and long-term follow-up may suggest classification as a symplastic or uncertain potential glomus tumor (GT), histological features and immunoprofile are indicative of malignant nodules developed in a typical GT. The follow-up has been negative for recurrence/metastases. A search of the literature revealed 17 cases of malignant GTs between 1995 and 2010, all fatal, of which 10 had skin as the primary site.

Facial basal cell carcinoma: analysis of recurrence and follow-up strategies

Rates of recurrence after incomplete surgical excision of basal cell carcinoma (BCC) range from 4 to 16.6% of analyzed cases. The aim of the present study was to identify the predictive factors associated with facial BBC recurrence following excision and their influences, in order to establish a proper therapeutic strategy. A monocentric retrospective study was performed reviewing all BCCs surgically excised at the Institute of Plastic Surgery, University of Padua, with particular focus on the involvement of surgical margins and recurrence. Seven hundred and nineteen lesions in 605 patients were studied. Correlations between recurrence probability and various characteristics of BCC were analyzed using a logistic regression model. It was observed that incomplete excision, deep margin involvement, the presence of sclerodermiform or metatypic basaloid squamous cells, as well as pleomorphous histological variants and/or peritumoral inflammatory infiltrates, were all related to an increase in the probability of recurrence. BCC excision must be followed by individualized management with particular consideration for the localization, the histological type and other known predisposing factors; the treatment strategy and, in particular, the length of the surveillance period and the frequency of patient assessment should be evaluated on the basis of the recurrence probability outlined.

Histological evolution of chronic wounds under negative pressure therapy

BACKGROUND

Negative pressure wound therapy (NPT) has achieved widespread success in the treatment of difficult wounds. However, its effects are but partially explored, and investigations mostly concentrated at the wound-dressing interface; a detailed histological description of the evolution of wounds under NPT is still lacking.

MATERIALS AND METHODS

Subsequent punch biopsies of NPT-treated chronic wounds of human patients were analysed. Phenomena occurring in wounds were quantified by analysis of proliferating cells nuclear antigen (PCNA) (proliferating nuclei), CD31 (blood vessels), CD68p (macrophages) and CD45 (lymphocytes) stained slides.

RESULTS

Three layers were identified in day-0 wounds. Over time, under NPT, the layers behaved differently: the most superficial (1.5 mm) developed granulation tissue, constant in thickness, with high proliferation index, increased in blood vessels density and developed acute inflammation. Instead, the two deeper layers decreased in proliferation rate, maintained vessels density unchanged, were cleared of chronic inflammation and oedema and underwent progression towards stable tissue.

DISCUSSION

Indeed, while most research has focused on induction of superficial granulation tissue by NPT, deeper layers appear to be also affected, with relieving of chronic inflammation and tissue stabilisation. This may be an important and under-appreciated effect, playing a role in the known positive outcomes of NPT, such as better graft-taking rates.

Temporary coverage of a forehead defect following tumor resection with a hyaluronic acid biological dressing: a case report

 Coverage of large skin defects, especially following tumor resection and in patients who are not good candidates for procedures requiring general anesthesia, may require a staged procedure. The use of dermal substitutes to cover the defect until autologous grafting can be performed has been described. Hyaluronic acid biological dressings (HABD) also have been used for the temporary coverage of partial- to full-thickness posttraumatic or postsurgical wounds. An 82-year-old man with cardiopathy presented with an 8 cm x 4 cm ulcerated squamous cell carcinoma on his forehead. Following surgical removal under local anesthesia, the 12 cm x 8 cm defect was covered with HABD, which was removed immediately before the scheduled surgical closure (21 days later). At that time, well-vascularized granulation tissue completely covered the bone and an autologous skin graft was applied. Punch biopsy results obtained 4 weeks after surgery showed dressing remnants in the dermis and confirmed the graft was totally integrated with the surrounding tissues; there was no evidence of hypertrophy or excessive scarring. In this patient, the staged procedure provided an excellent alternative to a complex surgical procedure. Use of the biological dressing required only a weekly wound and dressing assessment and the cosmetic result was good without evidence of a recurrence at the 2-year follow-up. Studies to ascertain the efficacy and effectiveness of this dressing for the temporary coverage of soft tissue defects are needed.

Layers of the abdominal wall: anatomical investigation of subcutaneous tissue and superficial fascia

INTRODUCTION

In recent times new surgical approaches have been developed, in which subcutaneous tissue is the primary object, such as flaps and fat removal techniques, but different descriptions and abundance of terminology persist in Literature about this tissue.

AIM AND METHODS

In order to investigate the structure of abdominal subcutaneous tissue, macroscopic and microscopic analyses of its layers were performed in 10 fresh cadavers. Results were compared with in vivo CT images of the abdomen of 10 subjects.

RESULTS

The subcutaneous tissue of the abdomen comprises three layers: a superficial adipose layer (SAT), a membranous layer, and a deep adipose layer (DAT). The SAT presented fibrous septa that defined polygonal-oval lobes of fat cells with a mean circularity factor of 0.856 ± 0.113. The membranous layer is a continuous fibrous membrane rich in elastic fibers with a mean thickness of 847.4 ± 295 μm. In the DAT the fibrous septa were predominantly obliquely-horizontally oriented, defining large, flat, polygonal lobes of fat cells (circularity factor: mean 0.473 ± 0.07). The CT scans confirm these findings, showing a variation of the thickness of the SAT, DAT and membranous layer according with the subjects and with the regions.

DISCUSSION

The distinction of SAT and DAT and their anatomic differences are key elements in modern approaches to liposuction. The membranous layer appears to be also a dissection plane which merits further attention. According with the revision of Literature, the Authors propose that the term "superficial fascia" should only be used as a synonym for the membranous layer.

In vivo acceleration of skin growth using a servo-controlled stretching device

Tension is a principal force experienced by skin and serves a critical role in growth and development. Optimal tension application regimens may be an important component for skin tissue engineering and dermatogenesis. In this study, we designed and tested a novel servo-controlled skin-stretching device to apply predetermined tension and waveforms in mice. The effects of static and cyclical stretching forces were compared in 48 mice by measuring epidermal proliferation, angiogenesis, cutaneous perfusion, and principal growth factors using immunohistochemistry, real-time reverse transcriptase-polymerase chain reaction, and hyperspectral imaging. All stretched samples had upregulated epidermal proliferation and angiogenesis. Real-time reverse transcriptase-polymerase chain reaction of epidermal growth factor, transforming growth factor beta1, and nerve growth factor demonstrated greater expression in cyclically stretched skin when compared to static stretch. Hypoxia-induced factor 1alpha was significantly upregulated in cyclically stretched skin, but poststretch analysis demonstrated well-oxygenated tissue, collectively suggesting the presence of transient hypoxia. Waveform-specific mechanical loads may accelerate tissue growth by mechanotransduction and as a result of repeated cycles of temporary hypoxia. Further analysis of mechanotransduction signaling pathways may provide additional insight to improve skin tissue engineering methods and optimize our device.

Isolation method for a stem cell population with neural potential from skin and adipose tissue

OBJECTIVE: In recent years, research on stem cells has been focused on the development of personalized cell-based therapies. Owing to their homing properties, adult human stem cells are a promising source of autologous cells to be used as therapeutic vehicles. Multiple potential sources for clinically useful stem and progenitor cells have been identified, including autologous and allogenic embryonic, fetal and adult somatic cells from neural, adipose and mesenchymal tissue. In the present report, we describe a simple protocol to obtain an enriched culture of adult stem cells organized in neurospheres from two post-natal tissues: skin and adipose tissue. METHODS: Adult stem cells isolated from skin and adipose tissue derived from the same adult donor were amplified under varying conditions related to the coating of the chamber slide and the presence of serum and/or growth factors, such as with EGF and FGF2. Neurospheres were then expanded and evaluated in terms of proliferation and gene expression. RESULTS: Adipose and skin derived neurospheres were comparable in size, quantity of cells and genes expressed. Cells from both types of tissue grew optimally without slide coating, in the presence of serum and with the combined addition of FGF2 and EGF. DISCUSSION: We describe a method for isolating and improving a population of multipotent adult precursor cells from the two most accessible adult tissue sources: skin and adipose tissue. This autologous adult stem cell population could be used for cell replacement or cell therapies.

Quiescent platelets stimulate angiogenesis and diabetic wound repair

INTRODUCTION

Platelets partake in hemostasis, wound healing, and tumor growth. Although platelet-rich-plasma (PRP) has been used in surgery for several years, its mechanism of action and application methods are still poorly characterized.

MATERIALS AND METHODS

A single unit of human platelets obtained by plateletpheresis was diluted in plasma and divided into three equal volumes. One volume was stored at room temperature as fresh platelets (RT), another volume was frozen by storage at -80 degrees C (FZ), and the third volume was frozen at -80 degrees C with 6% DMSO (FZ6). Plasma (PL) was used as control. Using flow cytometry, platelets were tested for platelet glycoprotein GPIb and annexin V binding, as survival and activation markers, respectively. Hemostatic function was assessed by thromboelastometry. In vivo, platelets were topically applied on 1 cm,(2) full-thickness wounds on db/db mice (n = 10/group) and healing was staged microscopically and macroscopically.

RESULTS

All platelet preparations showed hemostatic ability. RT platelets were GPIb positive (nonactivated-quiescent platelets) and stimulated angiogenesis by threefold, and cell proliferation by fourfold in vivo. FZ platelets were positive for annexin V, indicating activated platelets and, in vivo, increased only wound granulation. FZ6 platelets contained 30% nonactivated-quiescent and 50% activated platelets and stimulated granulation, angiogenesis, cell proliferation, and promoted re-epithelialization in vivo.

CONCLUSIONS

Platelets showed distinct mechanisms to induce hemostasis and wound healing. Quiescent platelets are required to induce angiogenesis in vivo. Platelets stored at room temperature and frozen with 6% DMSO and stored at -80 degrees C achieved optimal wound healing in diabetic mice.