Intractable wounds and infections: the role of impaired vascularity and advanced surgical methods for treatment

Long-Term Reoperation Rates After Open versus Minimally Invasive Spine Surgery for Degenerative Lumbar Disease: Five Year Follow-Up of 2130 Patients

BACKGROUND

Minimally Invasive Spine Surgery (MISS) is a growing alternative to Open Spine Surgery (OSS). The preservation of musculature and minimization of iatrogenic injury is hypothesized to decrease the need for reoperation by preserving normal anatomy. Our objective is to compare the relative long-term reoperation rates after MISS and OSS for the treatment of degenerative disease of the lumbar spine.

METHODS

This retrospective analysis compares the long-term reoperation rates after MISS and OSS. Eligible patients were adults with a primary lumbar intervention carried out between 5/1/2004 and 1/31/2014 to allow for at least 5 years of follow up. Patients without sufficient descriptive metrics or follow-up data were excluded. The primary outcome was the rate of lumbar spine reoperation.

RESULTS

A total of 2130 patients met the inclusion criteria-1895 underwent OSS and 235 underwent MISS. On average and across all surgery types (decompression and decompression with fusion), 28% of OSS patients required reoperation during the minimum 5-year follow up period while only 14% of MISS patients required reoperation (P = 0.001). The MISS group was statistically identical to the OSS group in all categories except that the MISS group was on average 1.8 years older (62.25 vs. 60.45, P = 0.039) and had a higher incidence of diabetes (26% vs. 17%, P = 0.000), but had a lower average body mass index than the OSS group (28.35 vs. 29.60, P = 0.002).

CONCLUSIONS

In the setting of degenerative lumbar spine disease, MISS has the potential to reduce the long-term need for reoperation when compared with OSS.

Staphylococcus aureus Infection Initiates Hypoxia-Mediated Transforming Growth Factor-β1 Upregulation to Trigger Osteomyelitis

Little is unknown about the regulatory mechanisms underlying the pathogenesis of osteomyelitis induced by Staphylococcus aureus. Hypoxia-inducible factor-1α (HIF-1α) and transforming growth factor β1 (TGF-β1) were both upregulated in S. aureus-infected MC3T3-E1 cells and osteomyelitis patients. HIF-1α directly targets the hypoxia-responsive elements (HREs) of TGF-β1 mRNA to induce its expression. Silencing HIF-1α and TGF-β1, as well as treatment of hypoxia inhibitor IDF-11774, consistently elevated OPN and RUNX2 expression and alizarin Red S (ARS) and alkaline phosphatase (ALP) staining levels in MC3T3-E1 cells with S. aureus infection. S. aureus infection increased HIF-1α expression and serum TGF-β1 concentration in a mouse model of osteomyelitis. Hypoxia inhibitor IDF-11774 treatment reduced serum levels of interleukin (IL)-6, IL-1β, and C-reactive protein. Upon S. aureus infection, hypoxia was activated to trigger TGF-β1 upregulation through direct targeting of HRE on TGF-β1 mRNA by HIF-1α, eventually leading to osteomyelitis symptoms in terms of osteogenesis and mineralization deficiencies as well as elevated inflammation. This study hereby suggests a novel signaling cascade involving hypoxia/HIF-1α/TGF-β1 in osteomyelitis pathogenesis, which could potentially serve as a target for therapeutic measures. IMPORTANCE The pathogenesis of osteomyelitis induced by Staphylococcus aureus remains unclear. To develop therapeutic approaches for osteomyelitis, it is important to understand the molecular mechanisms of its pathogenesis. Our results suggests that hypoxia/HIF-1α/TGF-β1 signaling is involved in osteomyelitis pathogenesis. Thus, these findings highlight the potential of this signaling components as therapeutic targets for the treatment of osteomyelitis.

Methods for Assessing the Effects of Xylosides on Angiogenesis

Xylosides are small synthetic molecules consisting of a xylose molecule attached to an aglycone group and serve as primers in the assembly of core protein free glycosaminoglycans using cellular machinery. Synthetic xylosides hold great promise in many biomedical applications and as therapeutics. Recent advances in the study of xylosides have opened up the possibility of developing xylosides as therapeutics to achieve a desirable biological outcome through their selective priming and inhibitory activities toward glycosaminoglycan biosynthesis. The approach described, herein, will serve as a general strategy to comprehensively screen xylosides and evaluate their ability to promote or inhibit angiogenesis, a critical biological process that is dysregulated in over 70 human diseases.

Utilizing Colpocleisis to Repair a Vesicovaginal Fistula in a Cervical Cancer Patient with History of Pelvic Radiation: A Case Report and Literature Review

Background

Vesicovaginal fistula is a rare and distressing urological condition. It is especially prevalent in developing countries with the predominant etiology secondary to obstructed labor. Radiation therapy in female patients with cervical cancer is a risk factor for vesicovaginal fistula formation in the United States. Case Presentation. A 53-year-old woman with a history of cervical cancer and radiation presented with continuous urinary incontinence. Following diagnostic vaginoscopy, a 1 cm vesicovaginal fistula was diagnosed at the vaginal apex. The patient elected for surgical repair. She subsequently underwent successful transvaginal fistula closure using colpocleisis to optimally address the systemic factors of poor wound healing associated with irradiated tissue. Because of the adjacent tissue having been compromised by pelvic radiation, we opted to use a biologic graft made of human cadaveric pericardial tissue (CPT) instead of a native tissue flap to provide additional support for the fistula repair.

Conclusion

A transvaginal approach for surgical repair of vesicovaginal fistula can be successful in patients with a prior history of pelvic radiation. Transvaginal colpocleisis is a viable option to augment vesicovaginal fistula repair for patients with significant comorbidities when sexual intercourse is no longer desired.

In vitro response of macrophages to ceramic scaffolds used for bone regeneration

Macrophages, the primary cells of the inflammatory response, are major regulators of healing, and mediate both bone fracture healing and the inflammatory response to implanted biomaterials. However, their phenotypic contributions to biomaterial-mediated bone repair are incompletely understood. Therefore, we used gene expression and protein secretion analysis to investigate the interactions in vitro between primary human monocyte-derived macrophages and ceramic scaffolds that have been shown to have varying degrees of success in promoting bone regeneration in vivo Specifically, baghdadite (Ca3ZrSi2O9) and strontium-hardystonite-gahnite (Sr-Ca2ZnSi2O7-ZnAl2O4) scaffolds were chosen as two materials that enhanced bone regeneration in vivo in large defects under load compared with clinically used tricalcium phosphate-hydroxyapatite (TCP-HA). Principal component analysis revealed that the scaffolds differentially regulated macrophage phenotype. Temporal changes in gene expression included shifts in markers of pro-inflammatory M1, anti-inflammatory M2a and pro-remodelling M2c macrophage phenotypes. Of note, TCP-HA scaffolds promoted upregulation of many M1-related genes and downregulation of many M2a- and M2c-related genes. Effects of the scaffolds on macrophages were attributed primarily to direct cell-scaffold interactions because of only minor changes observed in transwell culture. Ultimately, elucidating macrophage-biomaterial interactions will facilitate the design of immunomodulatory biomaterials for bone repair.

A glycan-based approach to therapeutic angiogenesis

Angiogenesis, the sprouting of new blood vessels from existing vasculature, involves multiple complex biological processes, and it is an essential step for hemostasis, tissue healing and regeneration. Angiogenesis stimulants can ameliorate human disease conditions including limb ischemia, chronic wounds, heart disease, and stroke. The current strategies to improve the bioavailability of pro-angiogenic growth factors, including VEGF and FGF2, have remained largely unsuccessful. This study demonstrates that small molecules, termed click-xylosides, can promote angiogenesis in the in vitro matrigel tube formation assay and the ex ovo chick chorioallantoic membrane assay, depending on their aglycone moieties. Xyloside treatment enhances network connectivity and cell survivability, thereby, maintaining the network structures on matrigel culture for an extended period of time. These effects were achieved via the secreted xyloside-primed glycosaminoglycans (GAG) chains that in part, act through an ERK1/2 mediated signaling pathway. Through the remodeling of GAGs in the extracellular matrix of endothelial cells, the glycan approach, involving xylosides, offers great potential to effectively promote therapeutic angiogenesis.

Biomimetic Approaches for Bone Tissue Engineering

Although autologous bone grafts are considered a gold standard for the treatment of bone defects, they are limited by donor site morbidities and geometric requirements. We propose that tissue engineering technology can overcome such limitations by recreating fully viable and biological bone grafts. Specifically, we will discuss the use of bone scaffolds and autologous cells with bioreactor culture systems as a tissue engineering paradigm to grow bone in vitro. We will also discuss emergent vascularization strategies to promote graft survival in vivo, as well as the role of inflammation during bone repair. Finally, we will highlight some recent advances and discuss new solutions to bone repair inspired by endochondral ossification.

External Bolster Placement After Percutaneous Endoscopic Gastrostomy Tube Insertion: Is Looser Better?

BACKGROUND

Abdominal and gastric wall inflammation, infection, and necrosis after percutaneous endoscopic gastrostomy (PEG) placement is a topic of importance but of limited study. Healing of the abdominal wound after PEG placement is thought to be dependent on a number of factors, including the patient's nutrition status, comorbid disease status, and postprocedural PEG wound care. Another important factor that may influence wound healing is tissue tension and compression. This requires special attention to the correct placement of the external bolster of the PEG tube against the abdominal wall.

METHODS

We performed a study in mongrel dogs to determine the relevance of tissue compression on PEG-tube wound healing; 8 mongrel dogs each received 3 separate 24 Fr PEG tubes at 1 endoscopic setting. After PEG placement, the external bolster was placed at 0 cm, 1 cm, or 4 cm from the abdominal wall. Post-PEG care and enteral feedings were standardized. The dogs were killed at 3 weeks.

RESULTS

Partial migration of the PEG internal bolster into the gastric wall occurred in 1 of 8 of the PEG tubes with the external bolster at 0 cm. PEG-tube-tract tissue inflammation was worse in the dogs with the external bolster placed at 0 cm.

CONCLUSIONS

The position of the external bolster in relation to the abdominal wall may be an important factor in the healing of a post-PEG-tube-placement tissue tract.

Sequential delivery of immunomodulatory cytokines to facilitate the M1-to-M2 transition of macrophages and enhance vascularization of bone scaffolds

In normal tissue repair, macrophages exhibit a pro-inflammatory phenotype (M1) at early stages and a pro-healing phenotype (M2) at later stages. We have previously shown that M1 macrophages initiate angiogenesis while M2 macrophages promote vessel maturation. Therefore, we reasoned that scaffolds that promote sequential M1 and M2 polarization of infiltrating macrophages should result in enhanced angiogenesis and healing. To this end, we first analyzed the in vitro kinetics of macrophage phenotype switch using flow cytometry, gene expression, and cytokine secretion analysis. Then, we designed scaffolds for bone regeneration based on modifications of decellularized bone for a short release of interferon-gamma (IFNg) to promote the M1 phenotype, followed by a more sustained release of interleukin-4 (IL4) to promote the M2 phenotype. To achieve this sequential release profile, IFNg was physically adsorbed onto the scaffolds, while IL4 was attached via biotin-streptavidin binding. Interestingly, despite the strong interactions between biotin and streptavidin, release studies showed that biotinylated IL4 was released over 6 days. These scaffolds promoted sequential M1 and M2 polarization of primary human macrophages as measured by gene expression of ten M1 and M2 markers and secretion of four cytokines, although the overlapping phases of IFNg and IL4 release tempered polarization to some extent. Murine subcutaneous implantation model showed increased vascularization in scaffolds releasing IFNg compared to controls. This study demonstrates that scaffolds for tissue engineering can be designed to harness the angiogenic behavior of host macrophages towards scaffold vascularization.

Multimodal noninvasive monitoring of soft tissue wound healing

Here we report results of non-invasive measurements of indirect markers of soft tissue healing of traumatic wounds in an observational swine study and describe the quantification of analog physiological signals. The primary purpose of the study was to measure bone healing of fractures with four different wound treatments. A second purpose was to quantify soft tissue wound healing by measuring the following indirect markers: (1) tissue oxygenation, (2) fluid content, and (3) blood flow, which were all measured by non-invasive modalities, measured with available devices. Tissue oxygenation was measured by near infrared spectroscopy; fluid content was measured by bipolar bio-impedance; and blood flow was measured by Doppler ultrasound. Immediately after comminuted femur fractures were produced in the right hind legs of thirty anesthetized female Yorkshire swine, one of four wound treatments was instilled into each wound. The four wound treatments were as follows: salmon fibrinogen/thrombin-n = 8; commercial bone filler matrix-n = 7; bovine collagen-n = 8; porcine fibrinogen/thrombin-n = 7. Fractures were stabilized with an external fixation device. Immediately following wound treatments, measurements were made of tissue oxygenation, fluid content and blood flow; these measurements were repeated weekly for 3 weeks after surgery. Analog signals of each modality were recorded on both the wounded (right) hind leg and the healthy (left) hind leg, for comparison purposes. Data were processed off-line. The mean values of 10-s periods were calculated for right-left leg comparison. ANOVA was applied for statistical analysis. Results of the bone healing studies are published separately (Rothwell et al. in J Spec Oper Med 13:7-18, 2013). For soft tissue wounds, healing did not differ significantly among the four wound treatments; however, regional oxygenation of wounds treated with salmon fibrinogen/thrombin showed slightly different time trends. Further studies are needed to establish standards for healthy wound healing and for detection of pathological alterations such as infection. Non-invasive measurement and quantification of indirect markers of soft tissue wound healing support the goals and principles of evidence-based medicine and show potential as easy to administer tools for clinicians and battlefield medical personnel to apply when procedures such as the PET scan are not available or affordable. The method we developed for storing analog physiological signals could be used for maintaining electronic health records, by incorporating vital signs such as ECG and EEG, etc.

Therapeutic opportunities for targeting the ubiquitous cell surface receptor CD47

INTRODUCTION

CD47 is a ubiquitously expressed cell surface receptor that serves as a counter-receptor for SIRPα in recognition of self by the innate immune system. Independently, CD47 also functions as an important signaling receptor for regulating cell responses to stress.

AREAS COVERED

We review the expression, molecular interactions, and pathophysiological functions of CD47 in the cardiovascular and immune systems. CD47 was first identified as a potential tumor marker, and we examine recent evidence that its dysregulation contributes to cancer progression and evasion of anti-tumor immunity. We further discuss therapeutic strategies for enhancing or inhibiting CD47 signaling and applications of such agents in preclinical models of ischemia and ischemia/reperfusion injuries, organ transplantation, pulmonary hypertension, radioprotection, and cancer.

EXPERT OPINION

Ongoing studies are revealing a central role of CD47 for conveying signals from the extracellular microenvironment that limit cell and tissue survival upon exposure to various types of stress. Based on this key function, therapeutics targeting CD47 or its ligands thrombospondin-1 and SIRPα could have broad applications spanning reconstructive surgery, engineering of tissues and biocompatible surfaces, vascular diseases, diabetes, organ transplantation, radiation injuries, inflammatory diseases, and cancer.

Role of hyaluronan in angiogenesis and its utility to angiogenic tissue engineering

Angiogenesis represents the outgrowth of new blood vessels from existing ones, a physiologic process that is vital to supply nourishment to newly forming tissues during development and tissue remodeling and repair (wound healing). Regulation of angiogenesis in the healthy body occurs through a fine balance of angiogenesis-stimulating factors and angiogenesis inhibitors. When this balance is disturbed, excessive or deficient angiogenesis can result and contribute to development of a wide variety of pathological conditions. The therapeutic stimulation or suppression of angiogenesis could be the key to abrogating these diseases. In recent years, tissue engineering has emerged as a promising technology for regenerating tissues or organs that are diseased beyond repair. Among the critical challenges that deter the practical realization of the vision of regenerating functional tissues for clinical implantation, is how tissues of finite size can be regenerated and maintained viable in the long-term. Since the diffusion of nutrients and essential gases to cells, and removal of metabolic wastes is typically limited to a depth of 150-250 microm from a capillary (3-10 cells thick), tissue constructs must mandatorily permit in-growth of a blood capillary network to nourish and sustain the viability of cells within. The purpose of this article is to provide an overview of the role and significance of hyaluronan (HA), a glycosaminoglycan (GAG) component of connective tissues, in physiologic and pathological angiogenesis, its applicability as a therapeutic to stimulate or suppress angiogenesis in situ within necrotic tissues in vivo, and the factors determining its potential utility as a pro-angiogenic stimulus that will enable tissue engineering of neo-vascularized and functional tissue constructs for clinical use.

Inflammatory phase of bone healing initiates the regenerative healing cascade

Bone healing commences with an inflammatory reaction which initiates the regenerative healing process leading in the end to reconstitution of bone. An unbalanced immune reaction during this early bone healing phase is hypothesized to disturb the healing cascade in a way that delays bone healing and jeopardizes the successful healing outcome. The immune cell composition and expression pattern of angiogenic factors were investigated in a sheep bone osteotomy model and compared to a mechanically-induced impaired/delayed bone healing group. In the impaired/delayed healing group, significantly higher T cell percentages were present in the bone hematoma and the bone marrow adjacent to the osteotomy gap when compared to the normal healing group. This was mirrored in the higher cytotoxic T cell percentage detected under delayed bone healing conditions indicating longer pro-inflammatory processes. The highly activated periosteum adjourning the osteotomy gap showed lower expression of hematopoietic stem cell markers and angiogenic factors such as heme oxygenase and vascular endothelial growth factor. This indicates a deferred revascularization of the injured area due to ongoing pro-inflammatory processes in the delayed healing group. Results from this study suggest that there are unfavorable immune cells and factors participating in the initial healing phase. In conclusion, identifying beneficial aspects may lead to promising therapeutical approaches that might benefit further by eliminating the unfavorable factors.

Application of clinical proteomics in diagnosis and management of trauma patients

Poly-trauma remains a medical entity with major implications, for patient's morbidity, mortality and healthcare economics. Advances in molecular medicine have improved diagnostic techniques in detecting devastating complication after major trauma. Patients at high risk of multiple organ dysfunction syndrome (MODS) or adult respiratory distress syndrome (ARDS), could be identified early, monitored and treated. Proteomics is the systematic evaluation of proteins produced by the cell under normal or pathological circumstances. Investigating protein production will allow us to identify and modify disease natural history and treatment. In this review, we summarise the proteomic methods currently applied in trauma research.

Principles and therapeutic implications of angiogenesis, vasculogenesis and arteriogenesis

The vasculature is the first organ to arise during development. Blood vessels run through virtually every organ in the body (except the avascular cornea and the cartilage), assuring metabolic homeostasis by supplying oxygen and nutrients and removing waste products. Not surprisingly therefore, vessels are critical for organ growth in the embryo and for repair of wounded tissue in the adult. Notably, however, an imbalance in angiogenesis (the growth of blood vessels) contributes to the pathogenesis of numerous malignant, inflammatory, ischaemic, infectious and immune disorders. During the last two decades, an explosive interest in angiogenesis research has generated the necessary insights to develop the first clinically approved anti-angiogenic agents for cancer and blindness. This novel treatment is likely to change the face of medicine in the next decade, as over 500 million people worldwide are estimated to benefit from pro- or anti-angiogenesis treatment. In this following chapter, we discuss general key angiogenic mechanisms in health and disease, and highlight recent developments and perspectives of anti-angiogenic therapeutic strategies.

Vascularized bone blocks from the toe phalanx to solve complex intercalated defects in the fingers

PURPOSE

Vascularized bone transplants resist infection and allow rapid healing but keeping small bony segments vascularized, as needed for a finger defect, is a challenge. The purpose of this article is to present a cohort of patients with traumatic intercalated compound bony defects in the fingers that were reconstructed by a vascularized toe phalanx (or part of a phalanx) in a single stage.

METHODS

Eight patients were treated with an intercalary vascularized bone graft that included a part of the proximal phalanx (3 patients), most of the middle phalanx (4 patients), or a portion of each phalanx (1 patient) of a second toe (totaling 9 bone blocks). There was an associated soft-tissue defect in each patient, an infection in 6 patients, and cartilage loss in 4 patients. The toes were pedicled on the proper digital artery (6 patients) or a segment of the first dorsal metatarsal artery (2 patients). A mean length of 12 mm of vascularized bone was transferred. The associated skin island varied from a minimum of 2 x 1 cm to a maximum of 5 x 3 cm. Bleeding from all of the bone surfaces was evidenced once the clamps were released. The homolateral digital nerve and the contralateral neurovascular pedicle of the toe were kept in place. The toe defect was treated by soft-tissue arthroplasty or arthrodesis. No toe was amputated.

RESULTS

Radiologic bony union was evident at 4 to 6 weeks, except in 1 patient with an acute infection whose distal union failed to unite at 6 weeks because the infection recurred. Finger length loss averaged 3 mm. All patients returned to their preoperative occupation.

CONCLUSIONS

In this group of patients the toe phalanx reliably maintained its vascularization, allowing us to solve compound osteocutaneous defects in the fingers in a single stage. Donor site morbidity was minimal.

Biomechanical characterization of vaginal versus abdominal surgical wound healing in the rabbit

OBJECTIVE

The objective of the study was to compare biomechanical properties of vaginal versus abdominal surgical wound healing in the rabbit.

STUDY DESIGN

Bilateral 6-mm full-thickness circular segments were excised from the vagina and abdominal skin in 38 New Zealand White female rabbits. Animals were killed 0, 4, 7, 10, 14, 21, 28, and 35 days after wounding, and the wounds were assessed for surface area and tensile properties.

RESULTS

Wound closure and scar contraction were significantly faster in the vagina than the abdomen (P = .001). Baseline tensile strength (P = .05), modulus (P = .001), and tensile energy to break (P = .18) were higher in the abdomen, whereas maximal tissue elongation was higher in the vagina (P = .13). After wounding, a drop in tensile strength, modulus, and tensile energy to break was observed in both tissues through postwounding day 4, followed by a progressive recovery of these properties. A progressive loss of elasticity was noted in both tissues after wounding.

CONCLUSION

The surgical wound closes and contracts faster in the rabbit vagina than in its abdomen. Although these tissues have different biomechanical properties at baseline, they regenerate their tensile strength and lose their elasticity at a similar rate.

Vascularised bone grafts for the management of non-union

Non-union of the long bones may have severe consequences, particularly when combined with other post-traumatic sequelae, such as tendon adhesions, reflex sympathetic dystrophy and infection, among others. In these cases, it is important to treat the delayed union or non-union first or at the same time with the other problems in order to achieve adequate function. Once the normal bony healing process has been slowed or stopped, it is necessary to provide both stability to the fracture site, as well as a biological stimulus for the fibrocartilagenous callus to finish the healing process. Vascularised grafts, such as the free fibula, offer not only structural support, but also promote bone healing. The later is achieved by trabecular bone formation, as well as vascular sprouting from pedicle vessels.

Guanylyl cyclase-dependent chemotaxis of endothelial cells in response to nitric oxide gradients

Nitric oxide (NO) is an important regulator of angiogenesis and neovascularization. The nature of endothelial cell motility responses to NO was examined using a Boyden chamber method. NO generated via decomposition of either DEA/NO or DETA/NO produced increases in human umbilical vein endothelial cell (HUVEC) chemotaxis, which were completely abrogated by ODQ, a soluble guanylyl cyclase inhibitor. Measurements of NO either directly by chemiluminescence or its chemistry with diaminofluorescein revealed that chemotaxis was driven by subtle NO gradients between the lower and the upper wells in this system. In addition to diffusion and volatilization from the upper chambers, the data showed that HUVEC consumption of NO contributed to these sustained gradients. Comparison of DEA/NO- and DETA/NO-mediated responses suggested that the persistence of spatial NO gradients is as significant as the absolute magnitude of NO exposure per unit time. The findings suggest that subnanomolar NO gradients are sufficient to mobilize endothelial cell migration into hypoxic tissue during neovascularization events, such as in wound healing and cancer.