Lower-Limb Lymphatic Drainage Pathways and Lymph Nodes: A CT Lymphangiography Cadaver Study.

Background Most lymphatic imaging examinations of the lower limb require intradermal or subcutaneous injection of tracer material into the foot to demonstrate the lymphatic vessels; however, no standard protocol exists, and single or multiple injections are applied at different sites. Purpose To determine the three-dimensional relationships between each lymphatic group of the lower limb and corresponding regional lymph nodes. Materials and Methods A total of 130 lower limbs (55 from men and 75 from women) from 83 fresh human cadavers were studied. Lymphatic vessels were first visualized by using indocyanine green fluorescent lymphography with 19 injection sites in the foot, classified into four distinct lymphatic groups (anteromedial, anterolateral, posteromedial, and posterolateral); dilute oil-based contrast material was then injected. Next, specimens were scanned with CT and three-dimensional images were analyzed. Results The anteromedial and anterolateral lymphatic groups of the lower-leg lymphatic vessels were independent of each other and connected to different regional lymph nodes in the inguinal region. The posteromedial group and the anteromedial group in the lower leg drained to the same inguinal lymph nodes. Only the posterolateral group of lymphatic vessels in the lower leg drained to the popliteal lymph nodes. Leg lymphatic drainage pathways were independent of genital pathways. Conclusion Standard injection sites at the web spaces between the toes did not help visualize some lymph nodes of the lower leg. Additional injection sites in the medial, lateral, and posterior aspect of the foot would be better for evaluating the whole lymphatic pathways and regional lymph nodes and for improving understanding of leg lymphedema. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Weiss and Liddel in this issue.

Mechanical strain attenuates cytokine-induced ADAMTS9 expression via transient receptor potential vanilloid type 1.

The synovial fluids of patients with osteoarthritis (OA) contain elevated levels of inflammatory cytokines, which induce the expression of a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) and of the matrix metalloproteinase (MMP) in chondrocytes. Mechanical strain has varying effects on organisms depending on the strength, cycle, and duration of the stressor; however, it is unclear under inflammatory stimulation how mechanical strain act on. Here, we show that mechanical strain attenuates inflammatory cytokine-induced expression of matrix-degrading enzymes. Cyclic tensile strain (CTS), as a mechanical stressor, attenuated interleukin (IL)-1ß and tumor necrosis factor (TNF)-α-induced mRNA expression of ADAMTS4, ADAMTS9, and MMP-13 in normal chondrocytes (NHAC-kn) and in a chondrocytic cell line (OUMS-27). This effect was abolished by treating cells with mechano-gated channel inhibitors, such as gadolinium, transient receptor potential (TRP) family inhibitor, ruthenium red, and with pharmacological and small interfering RNA-mediated TRPV1 inhibition. Furthermore, nuclear factor κB (NF-κB) translocation from the cytoplasm to the nucleus resulting from cytokine stimulation was also abolished by CTS. These findings suggest that mechanosensors such as the TRPV protein are potential therapeutic targets in treating OA.

Reverse-supercharged, distally based latissimus dorsi flap for lumbar defect: A case report.

Well-vascularized tissue is required for successful reconstruction of a soft tissue defect in the lumbar region. There are several options for reconstruction; however, controversy exists regarding the optimal technique. Here, we present a case of a lumbar defect following tumor resection in a 75-year-old patient that was repaired using a reverse-supercharged, distally based latissimus dorsi flap. The defect of size 15 × 12 cm2 was localized to the lumbar region. An 11 × 7 cm2 -sized, distally based latissimus dorsi flap was designed cephalad to the latissimus dorsi muscle. After the flap was tunneled to the defect, vascular insufficiency of the skin flap was observed. Supercharging was subsequently performed by anastomosing the serratus anterior branch in a reverse manner to the lumbar perforator. The diameters of the vessels at the end-to-end anastomosis site were 1.0 mm (artery) and 1.2 mm (vein), respectively, and there was slight discrepancy in their calibers. After microvascular anastomosis, the vascular supply of the flap improved, and the flap survived uneventfully, without venous congestion. The patient was discharged 17 days after the surgery, and no recurrence of the tumor was observed at the 2-year follow-up. We report a case of successful salvage of a distally based latissimus dorsi flap by the reverse-supercharge technique based on a serratus anterior branch. This flap might be a suitable alternative for use in the lumbar region in the case of limited availability of reconstructive choices.

Modified Posterolateral Approach for Pterygium Colli.

Pterygium colli is a congenital deformity associated with malformation syndromes. Various surgical procedures have been reported, but these procedures have advantages and disadvantages. The modified posterolateral approach has been reported as a new surgical procedure for pterygium colli. However, there has been no confirmatory report. In this study, a case of pterygium colli that was treated with the modified posterolateral approach was reported.An 11-year-old girl with Turner syndrome was referred with chief complaints of web neck deformity and an abnormal hairline. The modified posterolateral approach was selected. Hairy excessive skin was excised at the posterolateral and posterior neck. An inferior skin incision was made parallel to the hairline, and a superior skin incision was made along the desired hairline. Hairless excessive skin was excised along the posterior midline of the neck. Undermining was extended over the sternocleidomastoid muscle, and flaps were rotated upward and inward. Z-plasty was performed at the posterior midline of the neck to prevent hypertrophic scar formation. The web neck deformity disappeared, but the patient expressed concern for excessive skin at the posterior midline. Thus, secondary surgery was performed 12 months later. The operative scar was opened 2 months after secondary surgery owing to suture abscess, and the wound was closed directly. The web neck deformity had not recurred, and the natural hairline was maintained at 65 months after the primary surgery.The modified posterolateral approach is beneficial for pterygium colli, because it allows the correction of the web neck deformity and abnormal hairline without a noticeable scar.

Exercise-Loaded Indocyanine Green Fluorescence Lymphangiography for Diagnosing Lymphedema.

BACKGROUND: Indocyanine green (ICG) fluorescence lymphography (ICGLG) that can visualize the lymphatic vessel and its flow noninvasively and dynamically was developed in 2007. It is frequently used to observe the function and pathway of the lymphatic vessels. ICGLG is simple and easy to perform, and it is useful for understanding the condition of the lymphatic system in real time. However, its protocol is not standardized. In addition, the lymphatic flow is enhanced by an exercise load such as walking. Till now, there is no report of exercise-loaded ICGLG. Therefore, we aimed to shorten the examination time and establish a standard ICGLG protocol. METHODS: We examined 63 patients (126 lower limbs) who visited our clinic for lower extremity edema. We observed detailed images of exercise-loaded ICGLG and examined the changes in findings over time in affected legs classified according to the International Society of Lymphedema. After ICG was injected, the participants exercised for 30 minutes. We observed the farthest proximal point where any ICG could be observed and the appearance of dermal backflow (DB), which is a specific finding of lymphedema, every 5 minutes. RESULTS: The proximal migration speed of ICG tended to slow as the disease stage worsened. For all disease stages, after 20 minutes of exercise, the DB appearance rate did not change further. The rates were 0% for legs with stage 0 lymphedema, 50% for legs with stage 1 lymphedema, and 100% for legs with stages 2a and 2b lymphedema. CONCLUSION: The appropriate exercise duration after ICG injection is 20 minutes. ICGLG is useful for screening for lymphedema.

Recurrent branch of anterior interosseous artery perforator-based propeller flap for distal forearm injuries: Report of 2 cases.

Despite various options for the reconstruction of soft tissue defects in the distal forearm, perforator-based propeller flap is rarely used. Here, we presented 2 cases of distal forearm injuries that were repaired using the recurrent branch of anterior interosseous artery perforator-based propeller flap. Patients in these cases were 57 and 67 years of age. Wounds resulting from farming machine injury and pyogenic extensor tenosynovitis following cat bite wounds were localized to the distal forearm and dorsum of the hand. Defect dimensions were 5 cm × 10 cm and 5 cm × 8 cm. The 12 cm × 7 cm and 21 cm × 4 cm sized recurrent branch of anterior interosseous artery perforator-based propeller flap was designed adjacent to the wounds. In the latter case, the absence of the posterior interosseous artery in the distal forearm was observed. One perforator from the recurrent branch of the anterior interosseous artery emerged through the septum between the extensor digiti minimi and extensor carpi ulnaris 7.5 cm and 6.0 cm proximal to the ulnar head in cases 1 and 2, respectively. Perforators were identified using multidetector computed tomographic angiography and handheld Doppler. Extending to two-thirds or almost the full length of the forearm, the flaps were raised and rotated by 90° and 120° to cover the defect. The donor sites were closed using free skin graft. Both flaps survived. Except for minor wound dehiscence and hemarthrosis, no other postoperative complications occurred. Patients returned to work or daily activities at 3- and 4-month follow-up after surgery.

Three-Dimensional Imaging of Lymphatic System in Lymphedema Legs Using Interstitial Computed Tomography-lymphography.

As a new trial, we used interstitial computed tomography-lymphography (CT-LG) in 10 patients with lower extremity lymphedema (n=20 limbs) at stage 0, 1, 2, or 3 under the International Society of Lymphology (ISL) classification. In all cases, CT-LG, lymphoscintigraphy, and indocyanine green fluorescence-lymphography (ICG-LG) were performed. In the examination of the ascending level of depicted lymphatic vessels, we measured the diameters of lymphatic vessels detected with CT-LG and conducted an image analysis of dermal backflow of lymph (DB). CT-LG had better resolution than lymphoscintigraphy and enabled the clear visualization of lymphatic vessels with a minimum lumen size of 0.7 mm. CT-LG also showed the three-dimensional architecture of the DB, which originated from deep lymphatic collectors via branched small lymphatic vessels. Our findings are quite valuable not only for detailed examinations of lymphedematous sites and for the lymphedema surgery, but also for investigations of the pathogenesis of lymphedema which has not yet been established. We observed that lymphoscintigraphy could show the lymphatic vessels up to the thigh level in all cases, whereas CT-LG enabled the vessels' visualization up to the leg level at maximum. In conclusion, CT-LG provided adequate and detailed three-dimensional imaging of the lymphatic system in lymphedema patients.

Laser-Assisted Indocyanine Green Angiography Aids in the Reconstruction of Gustilo Grade IIIB Open Lower-Limb Fractures.

Background The treatment of trauma to the lower extremities often carries a high risk of complications. To the best of our knowledge, no study has been published regarding the treatment of open lower-limb fractures using laser-assisted indocyanine green angiography (LA-ICG). Here we retrospectively evaluated LA-ICG-based therapeutic interventions and reported the use of LA-ICG and its results in this application. Patients and Methods Between January 2011 and December 2015, a total of 23 cases with Gustilo grade IIIB open lower-limb fractures were investigated. LA-ICG was used to demonstrate the presence of necrotic tissue and determine the range of debridement. We compared 13 patients treated using LA-ICG from 2013 to 2015 with 10 patients treated without LA-ICG from 2010 to 2013. We reviewed tissue necrosis and other outcomes of these patients. Results The tissue necrosis rate in the LA-ICG-used group was significantly lower than that in the LA-ICG-free group. There were also significant differences in the average number of instances of tissue necrosis per patient, debridements, and deep-site infections. There was no flap loss. Conclusion By using LA-ICG, not only plastic surgeons but also clinicians in all associated departments including orthopedics can perform early reliable debridement and share in trauma treatment planning. We will continue to accumulate similar cases and hope to further improve LA-ICG techniques.

A new lymphography protocol and interpretation principles based on functional lymphatic anatomy in lower limb lymphedema.

Indirect lymphatic system imaging is essential for diagnosing lymphatic diseases. The basic methodology involves intradermal or subcutaneous injection of a contrast agent into the surrounding lymphatic capillary, and the flow of the contrast agent is identified using a detector. Many contrast agents that use near-infrared dye, including indocyanine green (ICG) fluorescent lymphography, are available. ICG is rapidly spreading as a convenient and safe lymphedema diagnostic method, because it does not involve radiation exposure, and the imaging equipment is more compact than other devices. The lymphatic system is a semi-open circulatory system with numerous lymphatic capillaries acting as blind ends. Anatomical information on the injection site and observation of specific lymphatic vessels and nodes is important. However, this anatomical information is lacking. Recent reports suggest that ICG fluorescent lymphography can be applied to cadavers in the same manner as living bodies. Furthermore, these reports have demonstrated the functional aspects of the capillary lymph vessel networks as well as their relationship with lymphatic vessels and lymph nodes. This review article describes the historical progression from the old to the new functional lymphatic anatomy and introduces a new functional lymphography technique for the lower limbs.

Architecture of the subendothelial elastic fibers of small blood vessels and variations in vascular type and size.

Most blood vessels contain elastin that provides the vessels with the resilience and flexibility necessary to control hemodynamics. Pathophysiological hemodynamic changes affect the remodeling of elastic components, but little is known about their structural properties. The present study was designed to elucidate, in detail, the three-dimensional (3D) architecture of delicate elastic fibers in small vessels, and to reveal their architectural pattern in a rat model. The fine vascular elastic components were observed by a newly developed scanning electron microscopy technique using a formic acid digestion with vascular casts. This method successfully visualized the 3D architecture of elastic fibers in small blood vessels, even arterioles and venules. The subendothelial elastic fibers in such small vessels assemble into a sheet of meshwork running longitudinally, while larger vessels have a higher density of mesh and thicker mesh fibers. The quantitative analysis revealed that arterioles had a wider range of mesh density than venules; the ratio of density to vessel size was higher than that in venules. The new method was useful for evaluating the subendothelial elastic fibers of small vessels and for demonstrating differences in the architecture of different types of vessels.

A new severity classification of lower limb secondary lymphedema based on lymphatic pathway defects in an indocyanine green fluorescent lymphography study.

Most protocols for lymphatic imaging of the lower limb conventionally inject tracer materials only into the interdigital space; however, recent studies indicate that there are four independent lymphatic vessel groups (anteromedial, anterolateral, posteromedial, and posterolateral) in the lower limb. Thus, three additional injection sites are needed for lymphatic imaging of the entire lower limb. We aimed to validate a multiple injection designed protocol and demonstrate its clinical benefits. Overall, 206 lower limbs undergoing indocyanine green fluorescent lymphography with the new injection protocol were registered retrospectively. To assess the influence of predictor variables on the degree of severity, multivariable logistic regression models were used with individual known risk factors. Using a generalized linear model, the area under the curve (AUC) of the conventional clinical model, comprising known severity risk factors, was compared with that of the modified model that included defects in the posterolateral and posteromedial groups. Multivariable logistic regression models showed a significant difference for the posteromedial and posterolateral groups. The AUC of the modified model was significantly improved compared to that of the conventional clinical model. Finding defects in the posteromedial and posterolateral groups is a significant criterion for judging lymphedema severity and introducing a new lymphedema severity classification.

A phase III, multicenter, single-arm study to assess the utility of indocyanine green fluorescent lymphography in the treatment of secondary lymphedema.

OBJECTIVE: Indocyanine green (ICG) fluorescent lymphography might be useful for assessing patients undergoing lymphatic surgery for secondary lymphedema. The present clinical trial aimed to confirm whether ICG fluorescent lymphography would be useful in evaluating lymphedema, identifying lymphatic vessels suitable for anastomosis, and confirming patency of lymphaticovenular anastomosis in patients with secondary lymphedema. METHODS: The present phase III, multicenter, single-arm, open-label, clinical trial (HAMAMATSU-ICG study) investigated the accuracy of lymphedema diagnosis via ICG fluorescent lymphography compared with lymphoscintigraphy, rate of identification of lymphatic vessels at the incision site, and efficacy for confirming patency of lymphaticovenular anastomosis. The external diameter of the identified lymphatic vessels and the distance from the skin surface to the lymphatic vessels using preoperative ICG fluorescent lymphography were measured intraoperatively under surgical microscopy. RESULTS: When the clinical decision for surgery at each research site was made, the standard diagnosis of lymphedema was considered correct. For the 26 upper extremities, a central judgment committee who was unaware of the clinical presentation confirmed the imaging diagnosis was accurate for 100.0% of cases, whether the assessments had been performed via lymphoscintigraphy or ICG lymphography. In contrast, for the 88 lower extremities, the accuracy of the diagnosis compared with the diagnosis by the central judgment committee was 70.5% and 88.2% for lymphoscintigraphy and ICG lymphography, respectively. The external diameter of the identified lymphatic vessels was significantly greater in the lower extremities than in the upper extremities (0.54 ± 0.21 mm vs 0.42 ± 0.14 mm; P < .0001). Also, the distance from the skin surface to the lymphatic vessels was significantly longer in the lower extremities than in the upper extremities (5.8 ± 3.5 mm vs 4.4 ± 2.6 mm; P = .01). For 263 skin incisions, with the site placement determined using ICG fluorescent lymphography, the rate of identification of lymphatics vessels suitable for anastomosis was 97.7% (95% confidence interval, 95.1%-99.2%). A total of 267 lymphaticovenular anastomoses were performed. ICG fluorescent lymphography was judged as "useful" for confirming patency after the anastomosis in 95.1% of the cases. CONCLUSIONS: ICG fluorescent lymphography could be useful for improving the treatment of patients with secondary lymphedema from the outpatient setting to surgery.

The use of 33 MHz ultra-high-frequency ultrasonography for the evaluation of sweat glands in the axilla with osmidrosis.

BACKGROUND: This study aimed to assess the use of 33 MHz ultra-high-frequency ultrasonography (33MHz-UHFUS) for evaluating axillary sweat glands with osmidrosis in comparison with histological techniques. Axillary osmidrosis is a common problem in Asian societies, and the number and size of apocrine sweat glands have a strong relationship with osmidrosis severity. Currently, there are no methods to evaluate sweat gland distribution non-invasively. METHODS: In this study, 35 skin specimens from 10 fresh human cadavers without osmidrosis and retrospective ultrasonographic images from 20 patients with osmidrosis were used. Skin specimens were embedded in paraffin, thinly sliced, and finally stained with hematoxylin and eosin. Histologically, the apocrine and eccrine glands were evaluated, and the top and bottom depths of follicles were measured from the skin surface. In 33 MHz ultrasonography images, the depths of sweat glands were measured, and the mean grey value was calculated using Image J. RESULTS: Compared to histological data, 33MHz-UHFUS could be used to identify sweat glands as a hyperechoic structure between the dermis and fat layer. Furthermore, it could evaluate sweat gland distribution but could not distinguish between types of sweat glands. CONCLUSIONS: The distribution of sweat glands in the axilla can be non-invasively evaluated via 33MHz-UHFUS.

HAMAMATSU-ICG study: Protocol for a phase III, multicentre, single-arm study to assess the usefulness of indocyanine green fluorescent lymphography in assessing secondary lymphoedema.

INTRODUCTION: Secondary lymphoedema of the extremities is an important quality-of-life issue for patients who were treated for their malignancies. Indocyanine green (ICG) fluorescent lymphography may be helpful for assessing lymphoedema and for planning lymphaticovenular anastomosis (LVA). The objective of the present clinical trial is to confirm whether or not ICG fluorescent lymphography using the near-infrared monitoring camera is useful for assessing the indication for LVA, for the identification of the lymphatic vessels before the conduct of LVA, and for the confirmation of the patency of the anastomosis site during surgery. METHODS AND ANALYSIS: This trial is a phase III, multicentre, single-arm, open-label clinical trial to assess the efficacy and safety of ICG fluorescent lymphography when assessing and treating lymphoedema of patients with secondary lymphoedema who are under consideration for LVA. The primary endpoint is the identification rate of the lymphatic vessels at the incision site based on ICG fluorescent lymphograms obtained before surgery. The secondary endpoints are 1) the sensitivity and specificity of dermal back flow determined by ICG fluorescent lymphography as compared with 99mTc lymphoscintigraphy-one of the standard diagnostic methods and 2) the usefulness of ICG fluorescent lymphography when confirming the patency of the anastomosis site after LVA. ETHICS AND DISSEMINATION: The protocol for the study was approved by the Institutional Review Board of each institution. The trial was filed for and registered at the Pharmaceuticals and Medical Devices Agency in Japan. The trial is currently on-going and is scheduled to end in June 2020. TRIAL REGISTRATION NUMBER: jRCT2031190064; Pre-results.

Detailed Vascular Anatomy and Flap Harvest Technique of the Serratus Anterior/Rib Composite Flap.

BACKGROUND: The hemodynamics of blood flowing from the anterior serratus to the ribs has yet to be analyzed in detail in serratus anterior/rib composite flaps. The authors focused on new blood circulation, whereby the slip arteries branched from the serratus anterior branch, off the thoracodorsal artery and the intercostal arteries, directly through the interconnecting vessels (axial route). The authors analyzed in detail the hemodynamics of serratus anterior/rib composite flaps and developed a new method for flap elevation. METHODS: The axial route was identified and analyzed by performing macroscopic autopsies of formalin perfusion-fixed cadavers involving three-dimensional computed tomographic angiography and vascular corrosion casting. Flap elevation was performed with new blood circulation, which included the axial route, and blood flow was evaluated using indocyanine green fluorescence angiography. RESULTS: The interconnecting vessels penetrated the intercostal muscles at a mean distance of 4.5 cm from the anterior margin of the attachment sites of the serratus anterior muscle to the ribs and at a mean distance of 7.4 cm from the costochondral junction. The interconnecting vessels had a mean diameter of 0.5 mm. Vascular corrosion casting helped identify multiple capillaries that were distributed from the intercostal arteries to the periosteum of the ribs. In addition, intraoperative indocyanine green fluorescence angiography confirmed blood flow from the slip arteries to the intercostal arteries. CONCLUSION: Good blood flow in harvested graft tissue can be achieved by including the axial route with the periosteal blood circulation at the rib attachment sites of the serratus anterior in a serratus anterior/rib composite flap.

Correlations between Tracer Injection Sites and Lymphatic Pathways in the Leg: A Near-Infrared Fluorescence Lymphography Study.

BACKGROUND: The primary aim of this study was to determine the detailed anatomy of the lymphatics in the lower extremity using fresh human cadavers with indocyanine green fluorescence lymphography. The secondary aim was to apply the anatomical results to establish a new protocol for lymphography based on feasible allocations for tracer injection sites. METHODS: One hundred lower extremities from 53 fresh human cadavers were used for this study. The authors injected indocyanine green solution subcutaneously at 19 points around the foot along the borderline between the dorsum and planta according to anatomical landmarks. Immediately after the indocyanine green injections, gentle hand massage was applied at each injection site to facilitate indocyanine green uptake into the lymphatic vessels. Fluorescent images of the lymphatics were obtained using a near-infrared camera system. Imaging data of the lymphatics were analyzed to find correlations between the injection sites and the identified lymphatic vessels. RESULTS: The lymphatic system in the lower extremity was divided into four distinct lymphatic groups: anteromedial, anterolateral, posterolateral, and posteromedial. The lymphatic vessels in all except the posterolateral group connected to the inguinal nodes, and those in the posterolateral group connected to the popliteal nodes. The authors successfully elucidated correlations between the injection sites in the foot and each lymphatic group. CONCLUSION: The new classification of the four lymphatic groups in the lower extremity and identification of their origins in the foot enabled the authors to propose a new protocol for lymphography that includes four injection sites in specific circumflex locations.

A Fresh Cadaver Study on Indocyanine Green Fluorescence Lymphography: A New Whole-Body Imaging Technique for Investigating the Superficial Lymphatics.

BACKGROUND: Identification of the lymphatic system in cadavers is painstaking because lymphatic vessels have very thin walls and are transparent. Selection of appropriate contrast agents is a key factor for successfully visualizing the lymphatics. In this study, the authors introduce a new imaging technique of lymphatic mapping in the whole bodies of fresh cadavers. METHODS: Ten fresh human cadavers were used for this study. The authors injected 0.1 ml of indocyanine green fluorescence solution subcutaneously at multiple spots along the watershed lines between lymphatic territories and hand and foot regions. After the body was scanned by the near-infrared camera system, fluorescent tissues were harvested and histologic examination was performed under the microscope equipped with the infrared camera system to confirm that they were the lymphatics. RESULTS: Subcutaneously injected indocyanine green was immediately transported into the lymphatic vessels after gentle massage on the injection points. Sweeping massage along the lymphatic vessels facilitated indocyanine green transport inside the lymphatic vessel to move toward the lymph nodes. The lymphatic system was visualized well in the whole body. Histologic examinations confirmed that indocyanine green was detected in the lymphatic lumens specifically, even when located far from the injected points. CONCLUSIONS: The lymphatic system could be visualized in whole-body fresh cadavers, as in living bodies, using indocyanine green fluorescence lymphography. Compatibility of indocyanine green lymphography would facilitate the use of cadaveric specimens for macroscopic and microscopic analyses.

High molecular weight hyaluronan protects cartilage from degradation by inhibiting aggrecanase expression.

Hyaluronan (HA) is an extracellular matrix (ECM) component of articular cartilage and has been used to treat patients with osteoarthritis (OA). A disintegrin and metalloproteinases with thrombospondin motifs (ADAMTSs) play an important role in cartilage degradation in OA. We have previously reported that ADAMTS4 and ADAMTS9 were induced by cytokine stimulation. However, the effect of HA on the cytokine-inducible ADAMTS9 has never been investigated. Moreover, it is unclear whether HA protects cartilage by suppressing aggrecan degradation. Here, we examined the effects of HA on ADAMTS expression in vitro and on cartilage degradation in vivo. ADAMTS9 expression was higher than that of the other aggrecanases (ADAMTS4 and 5) in human chondrocytes, chondrocytic cells, and rat cartilage. ADAMTS4 and 9 mRNA levels were upregulated in cytokine-stimulated chondrocytes and chondrocytic cells. Pre-incubation with HA significantly inhibited ADAMTS9 mRNA expression in cytokine-stimulated cells. In a rat OA model, Adamts5 and 9 mRNA levels were transiently increased after surgery; intra-articular HA injections attenuated the induction of Adamts5 and 9 mRNA. HA also blocked aggrecan cleavage by aggrecanase in OA rats in a molecular size-dependent manner. These results demonstrate that HA attenuates induced aggrecanases expression in OA and thereby protects articular cartilage degradation by this enzyme. Our findings provide insight into the molecular basis for the beneficial effects of HA in OA. © 2018 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 36:3247-3255, 2018.