Myeloid progenitors differentiate into microglia and promote vascular repair in a model of ischemic retinopathy

Vision loss associated with ischemic diseases such as retinopathy of prematurity and diabetic retinopathy are often due to retinal neovascularization. While significant progress has been made in the development of compounds useful for the treatment of abnormal vascular permeability and proliferation, such therapies do not address the underlying hypoxia that stimulates the observed vascular growth. Using a model of oxygen-induced retinopathy, we demonstrate that a population of adult BM-derived myeloid progenitor cells migrated to avascular regions of the retina, differentiated into microglia, and facilitated normalization of the vasculature. Myeloid-specific hypoxia-inducible factor 1alpha (HIF-1alpha) expression was required for this function, and we also demonstrate that endogenous microglia participated in retinal vascularization. These findings suggest what we believe to be a novel therapeutic approach for the treatment of ischemic retinopathies that promotes vascular repair rather than destruction.

Functional adult myocardium in the absence of Na+-Ca2+ exchange: cardiac-specific knockout of NCX1

The excitation-contraction coupling cycle in cardiac muscle is initiated by an influx of Ca2+ through voltage-dependent Ca2+ channels. Ca2+ influx induces a release of Ca2+ from the sarcoplasmic reticulum and myocyte contraction. To maintain Ca2+ homeostasis, Ca2+ entry is balanced by efflux mediated by the sarcolemmal Na+-Ca2+ exchanger. In the absence of Na+-Ca2+ exchange, it would be expected that cardiac myocytes would overload with Ca2+. Using Cre/loxP technology, we generated mice with a cardiac-specific knockout of the Na+-Ca2+ exchanger, NCX1. The exchanger is completely ablated in 80% to 90% of the cardiomyocytes as determined by immunoblot, immunofluorescence, and exchange function. Surprisingly, the NCX1 knockout mice live to adulthood with only modestly reduced cardiac function as assessed by echocardiography. At 7.5 weeks of age, measures of contractility are decreased by 20% to 30%. We detect no adaptation of the myocardium to the absence of the Na+-Ca2+ exchanger as measured by both immunoblots and microarray analysis. Ca2+ transients of isolated myocytes from knockout mice display normal magnitudes and relaxation kinetics and normal responses to isoproterenol. Under voltage clamp conditions, the current through L-type Ca2+ channels is reduced by 50%, although the number of channels is unchanged. An abbreviated action potential may further reduce Ca2+ influx. Rather than upregulate other Ca2+ efflux mechanisms, the myocardium appears to functionally adapt to the absence of the Na+-Ca2+ exchanger by limiting Ca2+ influx. The magnitude of Ca2+ transients appears to be maintained by an increased gain of sarcoplasmic reticular Ca2+ release. The myocardium of the NCX1 knockout mice undergoes a remarkable adaptation to maintain near normal cardiac function.

Insulin-like growth factor 2 and potential regulators of hemangioma growth and involution identified by large-scale expression analysis

Hemangiomas are benign tumors of the vascular endothelium and are the most common tumors of infancy. These tumors are characterized by an initial phase of rapid proliferation, which is followed, in most cases, by spontaneous involution. Although most lesions resolve without complication, there are some cases in which hemangiomas can be life threatening when occurring near a vital structure. Treatment for these aggressive tumors represents an unmet clinical need. In addition, this characteristic progression of hemangiomas through distinct phases provides a unique opportunity for studying endothelial cell biology and angiogenesis. Using DNA microarrays representing approximately 10,000 human genes, we identified insulin-like growth factor 2 (IGF-2) as a potentially important regulator of hemangioma growth. IGF-2 was highly expressed during the proliferative phase and substantially decreased during involution. This finding was confirmed at the message level by quantitative reverse transcription-PCR and at the protein level by immunohistochemistry. IGF-2 protein was localized primarily to tumor vessels or vascular channels. Using a human hemangioma explant model, we show that IGF-2 promotes sprouting from intact hemangioma tissue. In addition, several angiogenesis-related factors, including integrins alpha(v)beta3 and alpha5beta1, are present in proliferating hemangiomas. During the involuting phase, an increase in several IFN-induced genes was observed. These studies identify potential regulators of hemangioma growth and involution and provide a foundation on which to build further mechanistic investigations into angiogenesis, using hemangiomas as a model.

T2-TrpRS Inhibits Preretinal Neovascularization and Enhances Physiological Vascular Regrowth in OIR as Assessed by a New Method of Quantification

PURPOSE

A carboxyl-terminal fragment of tryptophan tRNA synthetase (T2-TrpRS) has demonstrated potent angiostatic activity during retinal developmental neovascularization in vivo. The effects of T2-TrpRS on pathologic neovascularization were tested and compared with a potent VEGF antagonist using the mouse model of oxygen-induced retinopathy (OIR).

METHODS

C57BL/6J mice were transiently exposed to hyperoxic conditions (75% O2) between postnatal day 7 (P7) and P12 and then returned to room air. Retinas were isolated, blood vessels stained with isolectin Griffonia simplicifolia, images of retinal whole-mounts acquired, and the area of vascular obliteration and extent of preretinal neovascularization quantified. This method was compared to the commonly used method of OIR quantification in which the number of pre-inner limiting membrane (ILM) nuclei is counted in serial sections of whole eyes. To assess the angiostatic activity of T2-TrpRS, mice were injected intravitreally at P12 with either T2-TrpRS, a VEGF aptamer, or vehicle (PBS) alone, and the effects on area of obliteration and on preretinal neovascular tuft formation were assessed.

RESULTS

Using a modified method of quantification in the mouse OIR model based on images of isolectin-stained retinal wholemounts, we were able to assess reliably and consistently both vascular obliteration and preretinal neovascular tuft formation in the same specimen. T2-TrpRS demonstrated potent angiostatic activity, reducing the appearance of pathologic neovascular tufts by up to 90%. Surprisingly, T2-TrpRS also enhanced physiological revascularization of the obliterated retinal vasculature, reducing these areas by up to 60% compared with PBS-injected eyes. In contrast, the VEGF antagonist, while similarly reducing preretinal neovascular tuft formation, did not enhance revascularization of the obliterated areas.

CONCLUSIONS

Use of a rapid, quantifiable method to assess the effect of T2-TrpRS on retinal angiogenesis in the OIR model demonstrates the importance of a quantification system that permits simultaneous analysis of a drug's effect on vascular obliteration as well as on preretinal neovascularization. The results obtained using this method suggest enhanced clinical value for compounds such as T2-TrpRS that not only inhibit pathologic neovascularization, but also facilitate physiological revascularization of ischemic tissue.

Plants used as antidiabetics in popular medicine in Rio Grande do Sul, southern Brazil

ETHNOPHARMACOLOGICAL RELEVANCE

Plants are widely as antidiabetics. The study of these plants is essential because many of them may have undesirable effects, such as acute or chronic toxicity; or their use may even delay or discourage the adoption of the proper and effective treatment.

MATERIALS AND METHODS

The present study surveyed the plant species that are popularly used to treat diabetes mellitus in the state of Rio Grande do Sul in southern Brazil. Sixteen ethnobotanical surveys performed in the state were consulted, and the species used to treat diabetes were listed. For species cited in at least two of the studies, scientific data related to antidiabetic activity were searched in the ISI Knowledge database. The scientific binomial of each species was used as keywords, and data found in review papers were also included.

RESULTS

A total of 81 species in 42 families were mentioned; the most important families were Asteraceae and Myrtaceae. Twenty eight species were cited at least twice as being used to treat diabetes in the state. For 11 of these, no scientific data regarding antidiabetic activity could be located. The species most frequently mentioned for use with diabetes were Syzygium cumini (Myrtaceae) and Bauhinia forficata (Fabaceae), in 12 studies each, followed by Sphagneticola trilobata (Asteraceae), in six studies; and Baccharis trimera (Asteraceae), Bidens pilosa (Asteraceae), Cynara scolymus (Asteraceae), and Leandra australis (Melastomataceae) in four studies each. Bauhinia forficata and Syzygium cumini have been studied in more detail for antidiabetic activity.

CONCLUSIONS

A considerable number of plant species are traditionally used for the treatment of diabetes melitus in the Rio Grande do Sul State. The majority of those plants that have been studied for antidiabetic activity showed promising results, mainly for Bauhinia forficata and Syzygium cumini. However, for most of the plants mentioned, the studies are not sufficient to guarantee the efficacy and safety in the use of these plants in the treatment against diabetes.

Myeloid cells in infantile hemangioma

Little is known about the pathogenesis of infantile hemangiomas despite the fact that they are relatively common tumors. These benign neoplasms occur in as many as 1 in 10 births, and although rarely life threatening, hemangiomas can pose serious concerns to the cosmetic and psychosocial development of the afflicted child. Ulceration, scarring, and disfigurement are significant problems as are encroachment of the ear and eye, which can threaten hearing and vision. The precise mechanisms controlling the rapid growth observed in the first months of life and the spontaneous involution that follows throughout the course of years remain unknown. In this report we demonstrate the presence of large numbers of hematopoietic cells of the myeloid lineage in proliferating hemangiomas and propose a mechanism for the observed evolution of these lesions that is triggered by hypoxia and involves the participation of myeloid cells. We report the results of experiments using myeloid markers (CD83, CD32, CD14, CD15) that unexpectedly co-labeled hemangioma endothelial cells, providing new evidence that these cells are distinct from normal endothelium.

Hypertrophy and heart failure in mice overexpressing the cardiac sodium-calcium exchanger

BACKGROUND

The cardiac sodium-calcium exchanger (NCX1) is a key sarcolemmal protein for the maintenance of calcium homeostasis in the heart. Because heart failure is associated with increased expression of NCX1, heterozygous (HET) and homozygous (HOM) transgenic mice overexpressing NCX1 were developed and evaluated.

METHODS AND RESULTS

The NCX1 transgenic mice display 2.3-fold (HET) and 3.1-fold (HOM) increases in exchanger activity from wild-type (WT) mice. Functional information was obtained by echocardiography and catheterizations before and after hemodynamic stress from pregnancy, treadmill exercise or transaortic constriction (TAC). HET and HOM mice exhibited hypertrophy and blunted responses with beta-adrenergic stimulation. Postpartum mice from all groups were hypertrophied, but only the HOM mice exhibited premature death from heart failure. HOM mice became exercise intolerant after 6 weeks of daily treadmill running. After 21 days TAC, HET, and HOM mice exhibited significant contractile dysfunction and 15% to 40% mortality with clinical evidence of heart failure.

CONCLUSIONS

Hemodynamic stress results in a compensated hypertrophy in WT mice, but NCX1 transgenic mice exhibit decreased contractile function and heart failure in proportion to their level of NCX1 expression. Thus exchanger overexpression in mice leads to abnormal calcium handling and a decompensatory transition to heart failure with stress.

Progenitor cells and retinal angiogenesis

Nothing more dramatically captures the imagination of the visually impaired patient or the ophthalmologist treating them than the possibility of rebuilding a damaged retina or vasculature with "stem cells." Stem cells (SC) have been isolated from adult tissues and represent a pool of cells that may serve to facilitate rescue/repair of damaged tissue following injury or stress. We propose a new paradigm to "mature" otherwise immature neovasculature or, better yet, stabilize existing vasculature to hypoxic damage. This may be possible through the use of autologous bone marrow (BM) or cord blood derived hematopoietic SC that selectively target sites of neovascularization and gliosis where they provide vasculo- and neurotrophic effects. We have demonstrated that adult BM contains a population of endothelial and myeloid progenitor cells that can target activated astrocytes, a hallmark of many ocular diseases, and participate in normal developmental, or injury-induced, angiogenesis in the adult. Intravitreal injection of these cells from mice and humans can prevent retinal vascular degeneration ordinarily observed in mouse models of retinal degeneration; this vascular rescue correlates with functional neuronal rescue as well. The use of autologous adult BM derived SC grafts for the treatment of retinal vascular and degenerative diseases represents a novel conceptual approach that may make it possible to "mature" otherwise immature neovasculature, stabilize existing vasculature to hypoxic damage and/or rescue and protect retinal neurons from undergoing apoptosis. Such a therapeutic approach would obviate the need to employ destructive treatment modalities and would facilitate vascularization of ischemic and otherwise damaged retinal tissue.

Identifying Potential Regulators of Infantile Hemangioma Progression through Large-scale Expression Analysis: A Possible Role for the Immune System and Indoleamine 2,3 Dioxygenase (IDO) during Involution

Hemangiomas are benign endothelial tumors. Often referred to as hemangiomas of infancy (HOI), these tumors are the most common tumor of infancy. Most of these lesions proliferate rapidly in the first months of life, and subsequently slowly involute during early childhood without significant complications. However, they often develop on the head or neck, and may pose a significant cosmetic concern for families. In addition, a fraction of these tumors can grow explosively and ulcerate, bleed, or obstruct vision or airway structures. Current treatments for these tumors are associated with significant side effects, and our knowledge of the biology of hemangiomas is limited. The natural evolution of these lesions creates a unique opportunity to study the changes in gene expression that occur as the endothelium of these tumors proliferates and then subsequently regresses. Such information may also increase our understanding of the basic principals of angiogenesis in normal and abnormal tissue. We have performed large-scale genomic analysis of hemangioma gene expression using DNA microarrays. We recently identified insulin-like growth factor 2 as a potentially important regulator of hemangioma growth using this approach. However, little is known about the mechanisms involved in hemangioma involution. Here we explore the idea that hemangioma involution might be an immune-mediated process and present data to support this concept. We also demonstrate that proliferating hemangiomas express indoleamine 2,3 dioxygenase (IDO) and discuss a possible mechanism that accounts for the often slow regression of these lesions.

Molecular cloning and functional expression of contortrostatin, a homodimeric disintegrin from southern copperhead snake venom

Contortrostatin is a unique dimeric disintegrin isolated from southern copperhead snake venom. Through antagonism of integrins alphaIIbbeta3, alpha5beta1, alphavbeta3, and alphavbeta5, contortrostatin inhibits platelet aggregation and disrupts cancer cell adhesion and invasion. We cloned cDNA from a library made from the venom gland cells of Agkistrodon contortrix contortrix using polymerase chain reaction. We found that the contortrostatin gene is part of a precursor composed of proprotein, metalloproteinase, and disintegrin domains. The precursor cDNA is 2027 bp with a 1449-bp open reading frame. The disintegrin domain is 195 bp encoding 65 amino acids. Like other members of the disintegrin family, each subunit of contortrostatin has an RGD site, and the cysteine alignment is conserved. The disintegrin domain of the cDNA has been expressed in a eukaryotic expression system as a homodimeric fusion protein with an immunoglobulin. The recombinant protein is recognized by an antiserum against native contortrostatin in Western blot. Both the native and recombinant proteins bind to integrins alphavbeta3 and alphavbeta5. Like native contortrostatin, the recombinant fusion protein inhibits platelet aggregation, blocks cancer cell adhesion to fibronectin and vitronectin, and prevents invasion of cancer cells through a Matrigel barrier. The success of functional expression not only validates the cDNA cloning of this disintegrin, but also provides adequate material for functional studies of contortrostatin.

Contortrostatin, a homodimeric disintegrin, binds to integrin alphavbeta5

Contortrostatin is a homodimeric disintegrin from snake venom. We have shown that contortrostatin binds to integrins alphaIIbbeta3, alpha5beta1, and alphavbeta3. We now use several criteria to demonstrate the binding of contortrostatin to alphavbeta5. First, incubation of T24 cells, which express alphavbeta3 and alphavbeta5, with antibody against alphavbeta3 failed to completely inhibit adhesion of cells to vitronectin. However, pretreatment of the cells with contortrostatin or the combination of antibodies against alphavbeta3 and alphavbeta5 completely blocked adhesion to vitronectin. By contrast, either anti-alphavbeta5 alone or contortrostatin blocked adhesion of an alphavbeta3-negative T24 subline. Second, contortrostatin as well as anti-alphavbeta5 inhibits invasion of OVCAR-5, which express only alphavbeta5. Third, contortrostatin binds to purified alphavbeta5 in a saturable manner. Finally, radioligand binding assays yielded a K(d) value of 24 nM for [(125)I]contortrostatin binding to alphavbeta5. This investigation identifies alphavbeta5 as a binding site for contortrostatin. Blockage of alphavbeta5 by contortrostatin inhibits alphavbeta5-mediated adhesion and invasion.

Incorrect death certification. An invitation to obfuscation

The physician responsible for signing a death certificate has an obligation to complete the medical part of the form, which includes entering the cause of death. In a review of 384 death certificates signed by house staff and attending physicians at a university hospital over a one-year period, 59% contained errors in cause-of-death entries. The most common error was listing mechanisms rather than causes of death. Since death certificates are used in calculating basic mortality statistics, such a large percentage of error can lead to considerable statistical misinformation.

Three-Dimensional In Vivo Imaging of the Mouse Intraocular Vasculature during Development and Disease

PURPOSE

Aberrant growth of blood vessels in the eye is a major cause of vision loss, occurring as a complication of diabetic retinopathy, age-related macular degeneration, and retinal vascular occlusions, among others. Whereas in humans, in vivo angiography is routinely used to image such diseases, many animal models of ocular vascular disease and development rely on dissected tissues that may not accurately represent in vivo conditions and require enucleation of the eye, the death of the animal, or both.

METHODS

A method of three-dimensional imaging of blood vessels was used in the living mouse eye that involved scanning laser confocal microscopy and computer-aided image reconstruction.

RESULTS

This minimally invasive technique was used to collect three-dimensional images of intraocular vessels in vivo during development. The retinal and choroidal vasculature was studied during development and disease, in models of retinal degeneration, central retinal vein occlusion, and oxygen-induced retinopathy. To aid in investigations into cell-based therapies for retinal disease, two-color imaging was used to localize transplanted cells in relation to the vasculature. This technique was used to perform serial imaging of the ocular vasculature over time, when developmental regression of vessels was observed.

CONCLUSIONS

This in vivo vascular imaging approach is valuable in monitoring normal development, disease progression, and efficacy of experimental treatments in mouse models of ocular vascular disease and may have broader applications to the field of angiogenesis by using the readily visualized ocular vascular bed as a surrogate to test pro- and antiangiogenic compounds.

Functional effect of contortrostatin, a snake venom disintegrin, on human glioma cell invasion in vitro

The metastatic spread of cancer is a complex process that involves the combination of different cellular actions including cell adhesion to the extracellular matrix (ECM), breakdown of the ECM by specific matrix-degrading proteinases, and active cell locomotion. Contortrostatin (CN), a homodimeric snake venom disintegrin, has previously been demonstrated to be effective in blocking vitronectin/fibronectin-dependent adhesion and invasion of T98G human glioblastoma cells through Matrigel using in vitro studies. However, it is not known at what step of the invasion process CN exerts its inhibitory effect. In the present report, CN is shown to decrease invasion of various glioma cell lines through Matrigel affecting neither cell adhesion, nor cell viability. While CN had no effect on cell binding to laminin and type IV collagen, it blocked adhesion of alphav beta3-positive, but not alphav beta3-negative cells, to vitronectin and fibronectin. Furthermore, members of the matrix metalloproteinase (MMP) family and their physiological inhibitors, and of the plasminogen activator (PA)/plasmin system were demonstrated not to be involved in CN-induced loss of glioma cell invasiveness. Instead, CN inhibited active locomotion of cells on Matrigel. These data suggest that CN-mediated inhibition of glioma cell invasion through Matrigel is a direct result of impaired cell motility. Moreover, use of several glioma cell lines and integrin antibodies strongly indicates the versatility of CN in inhibiting the invasion process based on the ability of CN to interact with different integrins, including alphav beta3, alphav beta5, and alpha5beta1.

Differential regulation of tyrosine phosphorylation in tumor cells by contortrostatin, a homodimeric disintegrin, and monomeric disintegrins echistatin and flavoridin

The homodimeric disintegrin contortrostatin was compared directly to the monomeric disintegrins echistatin and flavoridin for the ability to affect protein tyrosine phosphorylation in tumor cells. It was observed that contortrostatin had a dramatic effect on the tyrosine phosphorylation status of several proteins in T24 human bladder cancer cells, including robust induction of phosphorylation of proteins in the range of 120-140 kDa. Echistatin alone had no effect on tyrosine phosphorylation in T24 cells, but dose-dependently inhibits the effects of contortrostatin when both are added simultaneously. Among the proteins that undergo tyrosine phosphorylation in response to contortrostatin treatment is CAS, a 130 kDa adapter protein involved in integrin signaling. Flavoridin alone was found to have no effect on CAS, but can completely block contortrostatin-induced phosphorylation of this protein in MDA-MB-435 cells. These observations strongly suggest that the homodimeric structure of contortrostatin functionally distinguishes it from other monomeric members of the disintegrin family.

Contortrostatin, a homodimeric disintegrin, actively disrupts focal adhesion and cytoskeletal structure and inhibits cell motility through a novel mechanism

Integrins play a major role in the regulation of cell motility. They physically link the extracellular environment to the cytoskeleton and participate in large protein complexes known as focal adhesions. In this report, it is demonstrated that treatment of tumor cells with the homodimeric disintegrin contortrostatin induces integrin-mediated tyrosine phosphorylation events and causes severe disruptions in the actin cytoskeleton and disassembly of focal adhesion structures without affecting cellular adhesion to a reconstituted basement membrane. Included in this disruption is the tyrosine phosphorylation and altered subcellular localization of FAK. Through use of transfected 293 cells with specific integrin expression profiles and anti-alphavbeta3 mAbs, we demonstrate that these events are mediated exclusively by the alphavbeta3 integrin and are likely the result of contortrostatin-mediated crosslinking of this receptor at the cell surface, since monovalent disintegrins, flavoridin or echistatin do not induce such effects. Further, it is shown that contortrostatin potently inhibits motility in cells expressing the alphavbeta33 integrin. The results of this study describe a novel integrin-mediated mechanism by which cell motility can be inhibited and suggest an alternative approach to therapeutic intervention for cancer invasion and metastasis.

Contortrostatin activates ERK2 and tyrosine phosphorylation events via distinct pathways

We report that cells adhering to contortrostatin show transient increases in activation of Extracellular signal Regulated Kinase 2 (ERK2). The kinetics and degree of activation are similar to cells adhering to fibronectin or vitronectin. We have recently shown that contortrostatin induces tyrosine phosphorylation in tumor cells. Contortrostatin is shown here to stimulate activation of ERK2 in suspended cells, but this activation follows a different dose-response pattern than contortrostatin-induced tyrosine phosphorylation. Since contortrostatin induces tyrosine phosphorylation via alphavbeta3, we explored the effects of an alphavbeta3-blocking antibody, 7E3, on contortrostatin-stimulated ERK2 activation. While 7E3 completely blocks the effect of contortrostatin on tyrosine phosphorylation, this antibody had no effect on activation of ERK2. In cells lacking expression of alphavbeta3, tyrosine phosphorylation was unaffected by contortrostatin treatment, but ERK2 was activated. This is strong evidence that contortrostatin is regulating tyrosine phosphorylation events and ERK2 activation via separate pathways and through different integrin receptors.

Contortrostatin, a snake venom disintegrin, induces alphavbeta3-mediated tyrosine phosphorylation of CAS and FAK in tumor cells

Contortrostatin is a homodimeric disintegrin that inhibits platelet aggregation and cell adhesion to extracellular matrix proteins by blocking integrins. The effect of contortrostatin on integrin-mediated signaling in tumor cells was investigated by studying tyrosine phosphorylation events and activation of specific signaling molecules. We found that at concentrations as low as 1 nM, soluble contortrostatin activates integrin signals leading to increased tyrosine phosphorylation of FAK and CAS, and that these signals are abolished by inhibiting Src family kinases. Using transfected 293 cells expressing specific integrins, it was determined that contortrostatin-generated signals are mediated exclusively by the alphavbeta3 integrin. This observation was extended by showing that cells lacking alphavbeta3, but expressing alphavbeta5 and alpha5beta1, do not respond in this way to contortrostatin treatment. In cells expressing alphavbeta3, blocking contortrostatin binding with antibodies against alphavbeta3 completely abrogates contortrostatin signals. Monovalent disintegrins echistatin and flavoridin were incapable of affecting tyrosine phosphorylation alone, but when added simultaneously with contortrostatin, completely inhibited contortrostatin-initiated signals. We propose that the homodimeric nature of contortrostatin imparts the ability to crosslink alphavbeta3 integrins, causing Src activation and hyperphosphorylation of FAK and CAS. This activity may represent a novel mechanism by which tumor cell motility can be inhibited.

The role of arthroscopy in the treatment of lunotriquetral ligament injuries

The treatment of lunotriquetral interosseous (LTIO) ligament injuries is controversial. It is part of a spectrum of injuries involving the ulnar side of the wrist. Associated injuries may play a greater role in the outcome of treatment than does the LTIO injury. Arthroscopy is the most accurate diagnostic tool available for the evaluation of LTIO ligament injuries; it allows diagnosis and often treatment of associated injuries. This article describes the current approach to the diagnosis and treatment of LTIO ligament injuries and related use of arthroscopy.