Areas Of Tissue Injury Research Articles

In vivo spatiotemporal dynamics of NG2 glia activity caused by neural electrode implantation

Neural interface technology provides direct sampling and analysis of electrical and chemical events in the brain in order to better understand neuronal function and treat neurodegenerative disease. However, intracortical electrodes experience inflammatory reactions that reduce long-term stability and functionality and are understood to be facilitated by activated microglia and astrocytes. Emerging studies have identified another cell type that participates in the formation of a high-impedance glial scar following brain injury; the oligodendrocyte precursor cell (OPC). These cells maintain functional synapses with neurons and are a crucial source of neurotrophic support. Following injury, OPCs migrate toward areas of tissue injury over the course of days, similar to activated microglia. The delayed time course implicates these OPCs as key components in the formation of the outer layers of the glial scar around the implant. In vivo two-photon laser scanning microscopy (TPLSM) was employed to observe fluorescently-labeled OPC and microglia reactivity up to 72 h following probe insertion. OPCs initiated extension of cellular processes (2.5 ± 0.4 μm h−1) and cell body migration (1.6 ± 0.3 μm h−1) toward the probe beginning 12 h after insertion. By 72 h, OPCs became activated at a radius of about 190.3 μm away from the probe surface. This study characterized the early spatiotemporal dynamics of OPCs involved in the inflammatory response induced by microelectrode insertion. OPCs are key mediators of tissue health and are understood to have multiple fate potentials. Detailed spatiotemporal characterization of glial behavior under pathological conditions may allow identification of alternative intervention targets for mitigating the formation of a glial scar and subsequent neurodegeneration that debilitates chronic neural interfaces.

Proline Precursors and Collagen Synthesis: Biochemical Challenges of Nutrient Supplementation and Wound Healing

Wound healing is a complex process marked by highly coordinated immune fluxes into an area of tissue injury; these are required for re-establishment of normal tissue integrity. Along with this cascade of cellular players, wound healing also requires coordinated flux through a number of biochemical pathways, leading to synthesis of collagen and recycling or removal of damaged tissues. The availability of nutrients, especially amino acids, is critical for wound healing, and enteral supplementation has been intensely studied as a potential mechanism to augment wound healing-either by increasing tensile strength, decreasing healing time, or both. From a practical standpoint, although enteral nutrient supplementation may seem like a reasonable strategy to augment healing, a number of biochemical and physiologic barriers exist that limit this strategy. In this critical review, the physiology of enteral amino acid metabolism and supplementation and challenges therein are discussed in the context of splanchnic physiology and biochemistry. Additionally, a review of studies examining various methods of amino acid supplementation and the associated effects on wound outcomes are discussed.

The pathology of eclampsia: An autopsy series

ABSTRACTObjective: We describe the main lesions in the liver, brain, and kidney from autopsies of women who died of eclampsia and characterize the endothelial injury.Methods: Cases were identified from a study involving 317 maternal deaths (2003–2006) conducted at the Maputo Central Hospital (Maputo, Mozambique) in association with ISGlobal (Barcelona, Spain). Histology slides along with stains for endothelial, histiocyte, and platelet markers (CD31, CD34, CD68, CD42B) were reviewed to identify the relevant lesions. Malondialdehyde stain was performed to demonstrate free radical generation.Results: Brain lesions were characterized by perivascular “edema” (68.4%), hemorrhage (36.8%), hemosiderin (31.6%), small vessel thrombosis (10.5%), and parenchymal necrosis (15.8%). Liver sections showed periportal/portal necrosis and sinusoidal fibrin (72.2%) with associated hepatic arterial medial necrosis (44.4%). Kidneys showed glomerular endotheliosis. Endothelial, histiocytic, and platelet markers highlighted capillary injury in the otherwise intact brain parenchyma. Stains for free radical formation were positive predominantly in the areas of tissue injury, but intact glial/neuronal elements were focally positive as evidence of widespread oxidative stress.Conclusion: Pathological changes in cases of eclampsia include widespread endothelial/vascular injury in vulnerable organ beds.

RIPK3 in cell death and inflammation: the good, the bad, and the ugly.

Necroptosis is a form of cell death that can be observed downstream of death receptor or pattern recognition receptor signaling under certain cellular contexts, or in response to some viral and bacterial infections. The receptor interacting protein kinases-1 (RIPK1) and RIPK3 are at the core of necroptotic signaling, among other proteins. Because this pathway is normally halted by the pro-apoptotic protease caspase-8 and the IAP ubiquitin ligases, how and when necroptosis is triggered in physiological settings are ongoing questions. Interestingly, accumulating evidence suggests that RIPK3 has functions beyond the induction of necroptotic cell death, especially in the areas of tissue injury and sterile inflammation. Here, we will discuss the role of RIPK3 in a variety of physiological conditions, including necroptotic and non-necroptotic cell death, in the context of viral and bacterial infections, tissue damage, and inflammation.

Secondary hyperalgesia is mediated by heat-insensitive A-fibre nociceptors.

It is believed that secondary hyperalgesia (the increased sensitivity to mechanical nociceptive stimuli that develops after cutaneous tissue injury in the surrounding uninjured skin) is mediated by a subclass of nociceptors: the slowly adapting A-fibre mechano-heat nociceptors (AMH-type I). Here we tested this hypothesis. By using intense long-lasting heat stimuli, which are known to activate these slowly adapting AMH-type I nociceptors, we show that the perceived intensity elicited by these stimuli is not increased in the area of secondary hyperalgesia. Moreover, we show that during an A-fibre nerve conduction block the perception elicited by the long-lasting heat stimuli is significantly reduced in a time window that matches the response profile of the AMH-type I nociceptors. AMH-type I nociceptors contribute to the perception of sustained heat, but they do not mediate secondary hyperalgesia. Therefore, we propose that secondary hyperalgesia is mediated by high threshold mechanoreceptors. Secondary hyperalgesia refers to the increase in sensitivity to mechanical nociceptive stimuli delivered outside the area of tissue injury. Previous studies have suggested that secondary hyperalgesia is mediated by a specific class of myelinated nociceptors: slowly adapting A-fibre mechano- and heat-sensitive (AMH) type I nociceptors. Here, we tested this hypothesis by examining whether long-lasting heat stimuli, which are known to activate AMH-type I nociceptors, elicit enhanced responses when delivered to the area of secondary hyperalgesia induced by high frequency electrical stimulation of the skin (HFS). Before and 20min after HFS, sustained 30s radiant heat stimuli were delivered to the area of increased mechanical pinprick sensitivity while participants continuously rated intensity of perception using an online visual analog scale (0-100mm). After HFS, no significant enhancement of heat perception was observed in the area of increased pinprick sensitivity. To establish that myelinated nociceptors actually contribute to the perception of sustained heat, we conducted a second experiment in which sustained heat stimuli were presented before and during an A-fibre nerve conduction block, achieved by applying a rubber band with weights which compresses the superficial radial nerve against the radius. During the block, heat perception was significantly reduced 17-33s after the onset of the heat stimulus (before: mean=53mm, during: mean=31mm; P=0.03), matching the response profile of AMH-type I nociceptors. These results support the notion that AMH-type I nociceptors contribute to the perception of sustained heat, but also show that these afferents do not mediate secondary hyperalgesia.

Cathepsin S Contributes to the Pathogenesis of Muscular Dystrophy in Mice

Duchenne muscular dystrophy (DMD) is an X-linked recessive disease caused by mutations in the gene encoding dystrophin. Loss of dystrophin protein compromises the stability of the sarcolemma membrane surrounding each muscle cell fiber, leading to membrane ruptures and leakiness that induces myofiber necrosis, a subsequent inflammatory response, and progressive tissue fibrosis with loss of functional capacity. Cathepsin S (Ctss) is a cysteine protease that is actively secreted in areas of tissue injury and ongoing inflammation, where it participates in extracellular matrix remodeling and healing. Here we show significant induction of Ctss expression and proteolytic activity following acute muscle injury or in muscle from mdx mice, a model of DMD. To examine the functional ramifications associated with greater Ctss expression, the Ctss gene was deleted in the mdx genetic background, resulting in protection from muscular dystrophy pathogenesis that included reduced myofiber turnover and histopathology, reduced fibrosis, and improved running capacity. Mechanistically, deletion of the Ctss gene in the mdx background significantly increased myofiber sarcolemmal membrane stability with greater expression and membrane localization of utrophin, integrins, and β-dystroglycan, which anchor the membrane to the basal lamina and underlying cytoskeletal proteins. Consistent with these results, skeletal muscle-specific transgenic mice overexpressing Ctss showed increased myofiber necrosis, muscle histopathology, and a functional deficit reminiscent of muscular dystrophy. Hence, Ctss induction during muscular dystrophy is a pathologic event that partially underlies disease pathogenesis, and its inhibition might serve as a new therapeutic strategy in DMD.

Complement C3a signaling mediates production of angiogenic factors in mesenchymal stem cells

A major portion of the beneficial effect of mesenchymal stem cells (MSC) is due to the production of trophic and angiogenic factors by these cells, and one of the efforts to improve the therapeutic efficacy of these cells lies in enhancing this capacity. Since there is complement activation in all areas of tissue injury, and both C3a and C5a activate MSC, it was asked whether stimulation with C3a or C5a would upregulate the production of trophic factors by MSC. C3a caused significant up-regulation of various angiogenic factors, including VEGF, CXCL8/IL-8 and IL-6. In contrast there was no detectable production of the pro-inflammatory cytokines TNF-α and IL-1β in spite of nuclear translocation of NFκB. Although C5a also caused moderate up-regulation of angiogenic factors, the effect was borderline significant. Furthermore the production of angiogenic factors induced by C3a was of physiological relevance: Supernatants of MSCs cultured under serum-free conditions induced minimal tube formation of HUVECs as an in vitro measure of angiogenesis; tube formation was considerably enhanced, when supernatants from C3a-stimulated MSC were used, while C3a itself had no direct angiogenic effect on HUVECs. The signaling cascade responsible for the production of angiogenic factors by C3a or C5a could be defined as activation of the rho cascade which was necessary for nuclear translocation of NFκB p65 and of phospho-ERK1/2. Although rho was only transiently activated, inhibition of the rho or “downstream of it” of the NFκB pathway, prevented C3a-and C5a-induced up-regulation of angiogenic factors.

TRPA1: A Gatekeeper for Inflammation

Tissue damage evokes an inflammatory response that promotes the removal of harmful stimuli, tissue repair, and protective behaviors to prevent further damage and encourage healing. However, inflammation may outlive its usefulness and become chronic. Chronic inflammation can lead to a host of diseases, including asthma, itch, rheumatoid arthritis, and colitis. Primary afferent sensory neurons that innervate target organs release inflammatory neuropeptides in the local area of tissue damage to promote vascular leakage, the recruitment of immune cells, and hypersensitivity to mechanical and thermal stimuli. TRPA1 channels are required for neuronal excitation, the release of inflammatory neuropeptides, and subsequent pain hypersensitivity. TRPA1 is also activated by the release of inflammatory agents from nonneuronal cells in the area of tissue injury or disease. This dual function of TRPA1 as a detector and instigator of inflammatory agents makes TRPA1 a gatekeeper of chronic inflammatory disorders of the skin, airways, and gastrointestinal tract.

HIF‐2α Suppresses p53 to Enhance the Stemness and Regenerative Potential of Human Embryonic Stem Cells

Human embryonic stem cells (hESCs) have been reported to exert cytoprotective activity in the area of tissue injury. However, hypoxia/oxidative stress prevailing in the area of injury could activate p53, leading to death and differentiation of hESCs. Here we report that when exposed to hypoxia/oxidative stress, a small fraction of hESCs, namely the SSEA3+/ABCG2+ fraction undergoes a transient state of reprogramming to a low p53 and high hypoxia inducible factor (HIF)-2α state of transcriptional activity. This state can be sustained for a period of 2 weeks and is associated with enhanced transcriptional activity of Oct-4 and Nanog, concomitant with high teratomagenic potential. Conditioned medium obtained from the post-hypoxia SSEA3+/ABCG2+ hESCs showed cytoprotection both in vitro and in vivo. We termed this phenotype as the “enhanced stemness” state. We then demonstrated that the underlying molecular mechanism of this transient phenotype of enhanced stemness involved high Bcl-2, fibroblast growth factor (FGF)-2, and MDM2 expression and an altered state of the p53/MDM2 oscillation system. Specific silencing of HIF-2α and p53 resisted the reprogramming of SSEA3+/ABCG2+ to the enhanced stemness phenotype. Thus, our studies have uncovered a unique transient reprogramming activity in hESCs, the enhanced stemness reprogramming where a highly cytoprotective and undifferentiated state is achieved by transiently suppressing p53 activity. We suggest that this transient reprogramming is a form of stem cell altruism that benefits the surrounding tissues during the process of tissue regeneration.

Self‐injurious behaviour: limbic dysregulation and stress effects in an animal model

Self-injurious behaviour (SIB) is prevalent in neurodevelopmental disorders, but its expression is highly variable within, and between diagnostic categories. This raises questions about the factors that contribute to aetiology and expression of SIB. Expression of SIB is generally described in relation to social reinforcement. However, variables that predispose vulnerability have not been as clearly characterised. This study reports the aetiology and expression of self-injury in an animal model of pemoline-induced SIB. It describes changes in gross neuronal activity in selected brain regions after chronic treatment with pemoline, and it describes the impact that a history of social defeat stress has on the subsequent expression of SIB during pemoline treatment. Experiment 1--Male Long-Evans rats were injected on each of five consecutive days with pemoline or vehicle, and the expression of SIB was evaluated using a rating scale. The brains were harvested on the morning of the sixth day, and were assayed for expression of cytochrome oxidase, an index of sustained neuronal metabolic activity. Experiment 2--Male Long-Evans rats were exposed to a regimen of 12 daily sessions of social defeat stress or 12 daily sessions of handling (i.e. controls). Starting on the day after completion of the social defeat or handling regimen, each rat was given five daily injections of pemoline. The durations of self-injurious oral contact and other stereotyped behaviours were monitored, and the areas of tissue injury were quantified. Experiment 1--Neuronal metabolic activity was significantly lower in a variety of limbic and limbic-associated brain structures in the pemoline-treated rats, when compared with activity in the same regions of vehicle-treated controls. In addition, neuronal activity was low in the caudate-putamen, and in subfields of the hypothalamus, but did not differ between groups for a variety of other brain regions, including nucleus accumbens, substantia nigra, ventral tegmentum, thalamus, amygdala, and cortical regions. Experiment 2--All the pemoline-treated rats exhibited SIB, and whereas the social defeat regimen did not alter the total amount of self-injurious oral contact or other stereotyped behaviours, it significantly increased the severity of tissue injury. A broad sampling of regional metabolic activity indicates that the pemoline regimen produces enduring changes that are localised to specific limbic, hypothalamic and striatal structures. The potential role of limbic function in aetiology of SIB is further supported by the finding that pemoline-induced self-injury is exacerbated by prior exposure to social defeat stress. Overall, the results suggest brain targets that should be investigated further, and increase our understanding of the putative role that stress plays in the pathophysiology of SIB.

Excessive Neutrophils and Neutrophil Extracellular Traps Contribute to Acute Lung Injury of Influenza Pneumonitis

Complications of acute respiratory distress syndrome (ARDS) are common among critically ill patients infected with highly pathogenic influenza viruses. Macrophages and neutrophils constitute the majority of cells recruited into infected lungs, and are associated with immunopathology in influenza pneumonia. We examined pathological manifestations in models of macrophage- or neutrophil-depleted mice challenged with sublethal doses of influenza A virus H1N1 strain PR8. Infected mice depleted of macrophages displayed excessive neutrophilic infiltration, alveolar damage, and increased viral load, later progressing into ARDS-like pathological signs with diffuse alveolar damage, pulmonary edema, hemorrhage, and hypoxemia. In contrast, neutrophil-depleted animals showed mild pathology in lungs. The brochoalveolar lavage fluid of infected macrophage-depleted mice exhibited elevated protein content, T1-α, thrombomodulin, matrix metalloproteinase-9, and myeloperoxidase activities indicating augmented alveolar-capillary damage, compared to neutrophil-depleted animals. We provide evidence for the formation of neutrophil extracellular traps (NETs), entangled with alveoli in areas of tissue injury, suggesting their potential link with lung damage. When co-incubated with infected alveolar epithelial cells in vitro, neutrophils from infected lungs strongly induced NETs generation, and augmented endothelial damage. NETs induction was abrogated by anti-myeloperoxidase antibody and an inhibitor of superoxide dismutase, thus implying that NETs generation is induced by redox enzymes in influenza pneumonia. These findings support the pathogenic effects of excessive neutrophils in acute lung injury of influenza pneumonia by instigating alveolar-capillary damage.

Human mucosal leishmaniasis: Neutrophils infiltrate areas of tissue damage that express high levels of Th17‐related cytokines

Mucosal leishmaniasis (ML) is characterised by severe tissue destruction. Herein, we evaluated the involvement of the IL-17-type response in the inflammatory infiltrate of biopsy specimens from 17 ML patients. IL-17 and IL-17-inducing cytokines (IL-1β, IL-23, IL-6 and TGF-β) were detected by immunohistochemistry in ML patients. IL-17(+) cells exhibited CD4(+), CD8(+) or CD14(+) phenotypes, and numerous IL-17(+) cells co-expressed the CC chemokine receptor 6 (CCR6). Neutrophils, a hallmark of Th17-mediated inflammation, were regularly detected in necrotic and perinecrotic areas and stained positive for neutrophil elastase, myeloperoxidase and MMP-9. Taken together, these observations demonstrate the existence of Th17 cells in ML lesions associated with neutrophils in areas of tissue injury and suggest that IL-17 is involved in ML pathogenesis.

Susceptibility-Weighted Imaging in Neurodegeneration in Langerhans Cell Histiocytosis

Figure 2. Bilateral SWI-hypointense calcifications in the substantia nigra and globus pallidus. A 15-year-old boy with confirmed Langerhans cell histiocytosis (LCH) was referred for magnetic resonance imaging (MRI). Conventional MRI, using T1and T2-weighted sequences, detected bilateral T2-hyperintense and T1-hypointense, non-contrast-enhancing signal alterations within the pons, dentate nuclei, and adjacent cerebellar white matter (Figure 1). In addition, discrete T1-hyperintense calcifications were noted in the globus pallidus. These lesions represent the classical pattern of neurodegeneration in LCH (ND-LCH). Susceptibility-weighted imaging (SWI) is a newly developed MRI sequence that is highly sensitive for intraparenchymal calcifications and hemorrhages because of its pulse design. The calcifications in the globus pallidus identified on T1-weighted sequences were more conspicuous on SWI. SWI also revealed additional calicifications affecting the substantia nigra that were not prospectively recognized on either conventional T1or T2-weighted sequences (Figure 2). SWI should be added to conventional MRI in patients with ND-LCH. SWI may reveal areas of tissue injury that go undetected on conventional MRI. SWI’s ability to more

Chimeric Maternal Cells with Tissue-Specific Antigen Expression and Morphology Are Common in Infant Tissues

Maternal microchimerism (MMc) has been purported to play a role in the pathogenesis of autoimmunity, but how a small number of foreign cells could contribute to chronic, systemic inflammation has not been explained. Reports of peripheral blood cells differentiating into tissue-specific cell types may shed light on the problem in that chimeric maternal cells could act as target cells within tissues. We investigated MMc in tissues from 7 male infants. Female cells, presumed maternal, were characterized by simultaneous immunohistochemistry and fluorescence in situ hybridization for X- and Y-chromosomes. Maternal cells constituted 0.017% to 1.9% of parenchymal cells and were found in all infants in liver, pancreas, lung, kidney, bladder, skin, and spleen. Maternal cells were differentiated: maternal hepatocytes in liver, renal tubular cells in kidney, and beta-islet cells in pancreas. Maternal cells were not found in areas of tissue injury or inflammatory infiltrate. Maternal hematopoietic cells were found only in hearts from patients with neonatal lupus. Thus, differentiated maternal cells are present in multiple tissue types and occur independently of inflammation or tissue injury. Loss of tolerance to maternal parenchymal cells could lead to organ-specific "auto" inflammatory disease and elimination of maternal cells in areas of inflammation.

Periostin as a Heterofunctional Regulator of Cardiac Development and Disease

Periostin (Postn) is a heterofunctional secreted extracellular matrix (ECM) protein comprised of four fasciclin domains that promotes cellular adhesion and movement, as well as collagen fibrillogenesis. Postn is expressed in unique growth centers during embryonic development where it facilitates epithelial-mesenchymal transition (EMT) of select cell populations undergoing reorganization. In the heart, Postn is expressed in the developing valves, cardiac fibroblasts and in regions of the outflow track. In the adult, Postn expression is specifically induced in areas of tissue injury or areas with ongoing cellular re-organization. In the adult heart Postn is induced in the ventricles following myocardial infarction, pressure overload stimulation, or generalized cardiomyopathy. Here we will review the functional consequences associated with Postn induction in both the developing and adult heart. The majority of data collected to date suggest a common function for Postn in both development and disease as a potent inducible regulator of cellular reorganization and extracellular matrix homeostasis, although some alternate and controversial functions have also been ascribed to Postn, the validity of which will be discussed here.

Cardiac Cell-Based Therapy: Cell Types and Mechanisms of Actions

Over the past decade, the concept that the heart could undergo cardiac regeneration has rapidly evolved. Studies have indicated that numerous sites in the body harbor stem or progenitor cells, prompting clinical trials of these potential therapeutic cell-based approaches. Most notable are the series of trials utilizing either skeletal myoblasts or autologous whole bone marrow. More recently the quest has focused on specific bone marrow constituents, most notably the mesenchymal stem cell, which has several unique advantages including immunoprivilege, immunosuppression, and the ability to home to areas of tissue injury. Most recently, cells have been identified within the heart itself that are capable of self-replication and differentiation. The discovery of cardiac stem cells offers not only a potential therapeutic approach but also provides a plausible target for endogenous activation as a therapeutic strategy. Together the new insights obtained from studies of cell-based cardiac therapy have ushered in new biological paradigms and enormous potential for novel therapeutic strategies for cardiac disease.

TRANSFORMING GROWTH FACTOR-β1 INDUCED MYOFIBROBLASTS REGULATE LNCaP CELL DEATH

Reactive stroma represents a generic wound response phenomenon, which has been identified in areas of tissue injury and carcinogenesis. To determine whether reactive stroma influences prostate tumor cell growth 3 primary prostate stromal cell lines were treated with transforming growth factor-beta1 (TGF-beta1) to induce the reactive stroma phenotype and then co-cultured with LNCaP cells. Flow cytometry was performed in LNCaP cells that had been co-cultured with induced reactive stroma or control stroma and an index of cell death and proliferation was obtained. Using the previously described 3 way differential reactive stroma xenograft tumor model consisting of LNCaP cells, stromal cells and Matrigel (Collaborative Research, Bedford, Massachusetts) LNCaP cell apoptosis was evaluated using TUNEL staining in a background of varying degrees of reactive stroma. Flow cytometric analysis revealed that LNCaP cells co-cultured with TGF-beta1 induced stromal cells demonstrated a significantly decreased rate of cell death compared with controls (p <0.001). In an animal model LNCaP cells of the 3 way xenograft constructs treated with TGF-beta1 latency associated peptide, an inhibitor of TGF-beta1, showed increased apoptosis by TUNEL staining (p <0.001). Double label immunohistochemistry analysis demonstrated that TGF-beta1 induced stromal cells had an increased proportion of myofibroblasts, the identifying cell type of reactive stroma. Furthermore, the degree of reactive stroma inversely corresponded to the degree of LNCaP cell death. These findings indicate that reactive stroma influences prostate cancer cell growth and warrant investigation of the regulatory mechanisms between reactive stroma and prostate cancer cells.

Neural mechanisms of cutaneous nociceptive pain. (Department of Neurology, University of Würzburg, Germany) Clin J Pain 2000;16:S131–S138.

Acute mechanical, thermal, and chemically induced pains in the skin are signaled by a set of specific nociceptive afferents, which encode the magnitude of the perceived pain by their discharge intensity. After tissue injury or inflammation, a number of changes in their properties of the primary afferent occur parallel to profound changes in the central nervous system. Primary hyperalgesia (within the area of tissue injury) is best explained by changes of the properties of primary nociceptive afferents, whereas secondary hyperalgesia (increased pain sensitivity outside the area of tissue injury) critically requires functional changes in the central nervous system. Collectively, these changes are the basis for many forms of hyperalgesia that can present clinically as incident pain. Knowledge of the various types of hyperalgesia and their underlying mechanisms is required for better treatment of this challenging aspect of chronic pain.

Neural mechanisms of cutaneous nociceptive pain.

Acute mechanical, thermal, and chemically induced pains in the skin are signalled by a set of specific nociceptive afferents, which encode the magnitude of the perceived pain by their discharge intensity. After tissue injury or inflammation, a number of changes in the properties of the primary afferent occur parallel to profound changes in the central nervous system. Primary hyperalgesia (within the area of tissue injury) is best explained by changes of the properties of primary nociceptive afferents, whereas secondary hyperalgesia (increased pain sensitivity outside the area of tissue injury) critically requires functional changes in the central nervous system. Collectively, these changes are the basis for the many forms of hyperalgesia that can present clinically as incident pain. Knowledge of the various types of hyperalgesia and their underlying mechanisms is required for better treatment of this challenging aspect of chronic pain.

The Cell Adhesion Domain in Plasma Vitronectin Is Cryptic

Vitronectin (Vn) is a major adhesive glycoprotein in blood. However, many of the functions of Vn are regulated by its conformational state and degree of multimerization. Here, the ability of native and denatured Vn to bind to integrin adhesion receptors was compared. Three lines of evidence suggest that the native, plasma form of Vn is not an adhesive glycoprotein. (i) Antibodies that bind in close proximity to the cell adhesion domain of Vn fail to bind to native Vn present in unfractionated plasma. (ii) Denatured Vn binds to both glycoprotein IIb/IIIa and alphavbeta3 in a dose-dependent manner. In contrast, native Vn is unable to bind either integrin. (iii) Thermal denaturation of native Vn, or its complexation with type 1 plasminogen activator inhibitor, exposed the cell adhesion domain of Vn. Thus, while plasma Vn is unable to bind integrins and is not an adhesive glycoprotein, the conformationally altered from of the protein binds avidly to both alphavbeta3 and glycoprotein IIb/IIIa. The data presented here indicate that such conformational changes in Vn are likely to occur in areas of tissue injury and thrombosis.