Lateral Laxity in Flexion Influences Patient-Reported Outcome After Total Knee Arthroplasty.

Introduction: Slight lateral laxity exists in normal knee especially in flexion. The lateral laxity in flexion has possibility to affect the outcome after total knee arthroplasty (TKA). Purpose: The purpose of this study was to determine how intraoperative laxity in flexion affects patient-reported outcome after total knee arthroplasty. Methods: We retrospectively analysed 98 knees with osteoarthritis that underwent total knee arthroplasty. After bone resection, ligament imbalance and joint component gaps were measured using an offset-type tensor while applying a 40-lb joint distraction force at 0° and 90° of knee flexion. The lateral laxity in flexion was determined by subtracting polyethylene insert thickness from the lateral gap at 90°. All patients were divided into three groups: ≤ 2 mm (A), 2-5 mm (B), and > 5 mm (C). One year after surgery, patients were asked to fill out questionnaires using the new Knee Society Score after examination outside the consultation room. Results: The mean intraoperative lateral laxities at 90° were - 0.2 ± 2.1 mm, 3.5 ± 0.7 mm, and 6.7 ± 1.9 mm in groups A, B, and C, respectively. The symptom score of group C was significantly lower than those of groups A or B. There were no significant differences in terms of satisfaction or the expectation and activity scores among all groups. There were no significant differences in terms of alignment after total knee arthroplasty among all groups. Conclusions: Excessive lateral laxity possibly resulted in worse patient-reported outcomes. However, slight lateral laxity of 2-5 mm might have no effect on patient-reported outcome and this slight varus imbalance could be acceptable. Altogether, our findings would lead to avoidance of excessive medial release in soft tissue balancing.

Cartilage tissues regulate systemic aging via ectonucleotide pyrophosphatase/phosphodiesterase 1 in mice.

Aging presents fundamental health concerns worldwide; however, mechanisms underlying how aging is regulated are not fully understood. Here, we show that cartilage regulates aging by controlling phosphate metabolism via ectonucleotide pyrophosphatase/phosphodiesterase 1 (Enpp1). We newly established an Enpp1 reporter mouse, in which an EGFP-luciferase sequence was knocked-in at the Enpp1 gene start codon (Enpp1/EGFP-luciferase), enabling detection of Enpp1 expression in cartilage tissues of resultant mice. We then established a cartilage-specific Enpp1 conditional knockout mouse (Enpp1 cKO) by generating Enpp1 flox mice and crossing them with cartilage-specific type 2 collagen Cre mice. Relative to WT controls, Enpp1 cKO mice exhibited phenotypes resembling human aging, such as short life span, ectopic calcifications, and osteoporosis, as well as significantly lower serum pyrophosphate levels. We also observed significant weight loss and worsening of osteoporosis in Enpp1 cKO mice under phosphate overload conditions, similar to global Enpp1-deficient mice. Aging phenotypes seen in Enpp1 cKO mice under phosphate overload conditions were rescued by a low vitamin D diet, even under high phosphate conditions. These findings suggest overall that cartilage tissue plays an important role in regulating systemic aging via Enpp1.

The IL-17-IL-17RA axis is required to promote osteosarcoma progression in mice.

Osteosarcoma is rare but is the most common bone tumor. Diagnostic tools such as magnetic resonance imaging development of chemotherapeutic agents have increased the survival rate in osteosarcoma patients, although 5-year survival has plateaued at 70%. Thus, development of new treatment approaches is needed. Here, we report that IL-17, a proinflammatory cytokine, increases osteosarcoma mortality in a mouse model with AX osteosarcoma cells. AX cell transplantation into wild-type mice resulted in 100% mortality due to ectopic ossification and multi-organ metastasis. However, AX cell transplantation into IL-17-deficient mice significantly prolonged survival relative to controls. CD4-positive cells adjacent to osteosarcoma cells express IL-17, while osteosarcoma cells express the IL-17 receptor IL-17RA. Although AX cells can undergo osteoblast differentiation, as can patient osteosarcoma cells, IL-17 significantly inhibited that differentiation, indicating that IL-17 maintains AX cells in the undifferentiated state seen in malignant tumors. By contrast, IL-17RA-deficient mice transplanted with AX cells showed survival comparable to wild-type mice transplanted with AX cells. Biopsy specimens collected from osteosarcoma patients showed higher expression of IL-17RA compared to IL-17. These findings suggest that IL-17 is essential to maintain osteosarcoma cells in an undifferentiated state and could be a therapeutic target for suppressing tumorigenesis.

Transthyretin amyloid deposition in ligamentum flavum (LF) is significantly correlated with LF and epidural fat hypertrophy in patients with lumbar spinal stenosis.

Lumbar spinal stenosis (LSS) is a degenerative disease characterized by intermittent claudication and numbness in the lower extremities. These symptoms are caused by the compression of nerve tissue in the lumbar spinal canal. Ligamentum flavum (LF) hypertrophy and spinal epidural lipomatosis in the spinal canal are known to contribute to stenosis of the spinal canal: however, detailed mechanisms underlying LSS are still not fully understood. Here, we show that surgically harvested LFs from LSS patients exhibited significantly increased thickness when transthyretin (TTR), the protein responsible for amyloidosis, was deposited in LFs, compared to those without TTR deposition. Multiple regression analysis, which considered age and BMI, revealed a significant association between LF hypertrophy and TTR deposition in LFs. Moreover, TTR deposition in LF was also significantly correlated with epidural fat (EF) thickness based on multiple regression analyses. Mesenchymal cell differentiation into adipocytes was significantly stimulated by TTR in vitro. These results suggest that TTR deposition in LFs is significantly associated with increased LF hypertrophy and EF thickness, and that TTR promotes adipogenesis of mesenchymal cells. Therapeutic agents to prevent TTR deposition in tissues are currently available or under development, and targeting TTR could be a potential therapeutic approach to inhibit LSS development and progression.

Remnant tissue enhances early postoperative biomechanical strength and infiltration of Scleraxis-positive cells within the grafted tendon in a rat anterior cruciate ligament reconstruction model.

When ruptured, ligaments and tendons have limited self-repair capacity and rarely heal spontaneously. In the knee, the Anterior Cruciate Ligament (ACL) often ruptures during sports activities, causing functional impairment and requiring surgery using tendon grafts. Patients with insufficient time to recover before resuming sports risk re-injury. To develop more effective treatment, it is necessary to define mechanisms underlying ligament repair. For this, animal models can be useful, but mice are too small to create an ACL reconstruction model. Thus, we developed a transgenic rat model using control elements of Scleraxis (Scx), a transcription factor essential for ligament and tendon development, to drive GFP expression in order to localize Scx-expressing cells. As anticipated, Tg rats exhibited Scx-GFP in ACL during developmental but not adult stages. Interestingly, when we transplanted the flexor digitorum longus (FDP) tendon derived from adult Scx-GFP+ rats into WT adults, Scx-GFP was not expressed in transplanted tendons. However, tendons transplanted from adult WT rats into Scx-GFP rats showed upregulated Scx expression in tendon, suggesting that Scx-GFP+ cells are mobilized from tissues outside the tendon. Importantly, at 4 weeks post-surgery, Scx-GFP-expressing cells were more frequent within the grafted tendon when an ACL remnant was preserved (P group) relative to when it was not (R group) (P vs R groups (both n = 5), p<0.05), and by 6 weeks, biomechanical strength of the transplanted tendon was significantly increased if the remnant was preserved (P vsR groups (both n = 14), p<0.05). Scx-GFP+ cells increased in remnant tissue after surgery, suggesting remnant tissue is a source of Scx+ cells in grafted tendons. We conclude that the novel Scx-GFP Tg rat is useful to monitor emergence of Scx-positive cells, which likely contribute to increased graft strength after ACL reconstruction.

A machine learning-based scoring system and ten factors associated with hip fracture occurrence in the elderly.

Hip fractures are fragility fractures frequently seen in persons over 80-years-old. Although various factors, including decreased bone mineral density and a history of falls, are reported as hip fracture risks, few large-scale studies have confirmed their relevance to individuals older than 80, and tools to assess contributions of various risks to fracture development and the degree of risk are lacking. We recruited 1395 fresh hip fracture patients and 1075 controls without hip fractures and comprehensively evaluated various reported risk factors and their association with hip fracture development. We initially constructed a predictive model using Extreme Gradient Boosting (XGBoost), a machine learning algorithm, incorporating all 40 variables and evaluated the model's performance using the area under the receiver operating characteristic curve (AUC), yielding a value of 0.87. We also employed SHapley Additive exPlanation (SHAP) values to evaluate each feature importance and ranked the top 20. We then used a stepwise selection method to determine key factors sequentially until the AUC reached a plateau nearly equal to that of all variables and identified the top 10 sufficient to evaluate hip fracture risk. For each, we determined the cutoff value for hip fracture occurrence and calculated scores of each variable based on the respective feature importance. Individual scores were: serum 25(OH)D levels (<10 ng/ml, score 7), femoral neck T-score (<-3, score 5), Barthel index score (<100, score 3), maximal handgrip strength (<18 kg, score 3), GLFS-25 score (≥24, score 2), number of falls in previous 12 months (≥3, score 2), serum IGF-1 levels (<50 ng/ml, score 2), cups of tea/day (≥5, score -2), use of anti-osteoporosis drugs (yes, score -2), and BMI (<18.5 kg/m2, score 1). Using these scores, we performed receiver operating characteristic (ROC) analysis and the resultant optimal cutoff value was 7, with a specificity of 0.78, sensitivity of 0.75, and AUC of 0.85. These ten factors and the scoring system may represent tools useful to predict hip fracture.

Potential function of Scx+/Sox9+ cells as progenitor cells in rotator cuff tear repair in rats.

Tendons and their attachment sites to bone, fibrocartilaginous tissues, have poor self-repair capacity when they rupture, and have risks of retear even after surgical repair. Thus, defining mechanisms underlying their repair is required in order to stimulate tendon repairing capacity. Here we used a rat surgical rotator cuff tear repair model and identified cells expressing the transcription factors Scleraxis (Scx) and SRY-box 9 (Sox9) as playing a crucial role in rotator cuff tendon-to-bone repair. Given the challenges of establishing stably reproducible models of surgical rotator cuff tear repair in mice, we newly established Scx-GFP transgenic rats in which Scx expression can be monitored by GFP. We observed tissue-specific GFP expression along tendons in developing ScxGFP transgenic rats and were able to successfully monitor tissue-specific Scx expression based on GFP signals. Among 3-, 6-, and 12-week-old ScxGFP rats, Scx+/Sox9+ cells were most abundant in 3-week-old rats near the site of humerus bone attachment to the rotator cuff tendon, while we observed significantly fewer cells in the same area in 6- or 12-week-old rats. We then applied a rotator cuff repair model using ScxGFP rats and observed the largest number of Scx+/Sox9+ cells at postoperative repair sites of 3-week-old relative to 6- or 12-week-old rats. Tendons attach to bone via fibrocartilaginous tissue, and cartilage-like tissue was seen at repair sites of 3-week-old but not 6- or 12-week-old rats during postoperative evaluation. Our findings suggest that Scx+/Sox9+ cells may function in rotator cuff repair, and that ScxGFP rats could serve as useful tools to develop therapies to promote rotator cuff repair by enabling analysis of these activities.

Effects of Remnant Tissue Preservation on Tunnel Enlargement After Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction Using the Hamstring Tendon.

BACKGROUND: The effects of remnant tissue preservation on tunnel enlargement after anatomic double-bundle anterior cruciate ligament (ACL) reconstruction have not yet been established. HYPOTHESIS: The preservation of ACL remnant tissue may significantly reduce the degree and incidence of tunnel enlargement after anatomic double-bundle ACL reconstruction, while the remnant-preserving procedure may not significantly increase the incidence of tunnel coalition after surgery. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: A total of 79 patients underwent anatomic double-bundle ACL reconstruction. Based on the Crain classification of ACL remnant tissue, 40 patients underwent the remnant-preserving procedure (group P), and the remaining 39 patients underwent the remnant-resecting procedure (group R). There were no differences between the 2 groups concerning all background factors, including preoperative knee instability and intraoperative tunnel positions. All patients were examined using computed tomography and a standard physical examination at 2 weeks and 1 year after surgery. RESULTS: During surgery, the femoral and tibial anteromedial (AM) tunnel sizes in both groups averaged 6.6 and 6.5 mm, respectively. The femoral and tibial posterolateral (PL) tunnel sizes in both groups averaged 6 and 6 mm, respectively. There were no differences in the intraoperative tunnel positions and tunnel sizes between groups. Concerning the femoral AM tunnel, the degree of tunnel enlargement in the oblique coronal and oblique axial views in group P was significantly less than that in group R (P = .0068 and .0323, respectively). Regarding the femoral AM tunnel cross-sectional area, the degree and incidence of tunnel enlargement in group P were significantly less than those in group R (P = .0086 and .0278, respectively). There were no significant differences in tunnel coalition between groups. In each group, there were no significant relationships between tunnel enlargement and each clinical outcome. CONCLUSION: Remnant preservation in anatomic double-bundle ACL reconstruction reduced enlargement of the femoral AM tunnel and did not increase the incidence of tunnel coalition. This is one of the advantages of remnant-preserving ACL reconstruction.

Is the Grafted Tendon Shifted Anteriorly in the Femoral Tunnel at the Postremodeling Phase After Anterior Cruciate Ligament Reconstruction? A Clinical MRI Study.

BACKGROUND: Based on previous in vitro studies, it has been commonly believed that during anterior cruciate ligament (ACL) reconstruction with hamstring tendon, the grafted tendon is shifted anteriorly in the tunnel permanently after the graft is anchored to the tunnel wall. However, this has not been proven by in vivo studies. HYPOTHESIS: At 1 year after anatomic double-bundle ACL reconstruction, the grafted tendons may not be shifted anteriorly in the femoral tunnel but anchored to the bony wall at the center of the tunnel. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Participants consisted of 40 patients who underwent anatomic double-bundle ACL reconstruction. The grafted tendons located in the femoral tunnel were examined 1 year after surgery using 2 different magnetic resonance imaging (MRI) protocols. In the first substudy, with 20 patients, the grafted tendon location was evaluated on an inclined sagittal multiplanar reconstruction (MPR) image taken using a standard T2-weighted protocol. In the second substudy with the remaining 20 patients, tendon location was evaluated on a pure axial MPR image taken using a VISTA (volume isotropic turbo spin echo acquisition) protocol. RESULTS: On the inclined sagittal T2-weighted images of the anteromedial (AM) graft, the anterior width of the newly formed fibrous tissue, which surrounded the tendon graft, was significantly greater than the posterior width (P = .001). The center of the grafted tendon was slightly (mean, 2.5% of the tunnel diameter) but significantly (P = .0310) shifted posteriorly from the tunnel center. On the axial T2-VISTA images, the center of the AM graft was slightly but significantly shifted posteriorly (3.9%; P = .022) and medially (5.5%; P = .002) from the tunnel center. The center of the posterolateral (PL) graft was not significantly shifted to any direction from the center of the tunnel. CONCLUSION: The grafted tendons were not shifted anteriorly in the femoral tunnel 1 year after anatomic double-bundle ACL reconstruction. The PL graft was located approximately at the center of the tunnel outlet, while the AM graft was slightly but significantly shifted posteriorly and proximally.

Mice Deficient in Angiopoietin-like Protein 2 (Angptl2) Gene Show Increased Susceptibility to Bacterial Infection Due to Attenuated Macrophage Activity.

Macrophages play crucial roles in combatting infectious disease by promoting inflammation and phagocytosis. Angiopoietin-like protein 2 (ANGPTL2) is a secreted factor that induces tissue inflammation by attracting and activating macrophages to produce inflammatory cytokines in chronic inflammation-associated diseases such as obesity-associated metabolic syndrome, atherosclerosis, and rheumatoid arthritis. Here, we asked whether and how ANGPTL2 activates macrophages in the innate immune response. ANGPTL2 was predominantly expressed in proinflammatory mouse bone marrow-derived differentiated macrophages (GM-BMMs) following GM-CSF treatment relative to anti-inflammatory cells (M-BMMs) established by M-CSF treatment. Expression of the proinflammatory markers IL-1ß, IL-12p35, and IL-12p40 significantly decreased in GM-BMMs from Angptl2-deficient compared with wild-type (WT) mice, suggestive of attenuated proinflammatory activity. We also report that ANGPTL2 inflammatory signaling is transduced through integrin α5ß1 rather than through paired immunoglobulin-like receptor B. Interestingly, Angptl2-deficient mice were more susceptible to infection with Salmonella enterica serovar Typhimurium than were WT mice. Moreover, nitric oxide (NO) production by Angptl2-deficient GM-BMMs was significantly lower than in WT GM-BMMs. Collectively, our findings suggest that macrophage-derived ANGPTL2 promotes an innate immune response in those cells by enhancing proinflammatory activity and NO production required to fight infection.

ANGPTL2 increases bone metastasis of breast cancer cells through enhancing CXCR4 signaling.

Bone metastasis of breast cancer cells is a major concern, as it causes increased morbidity and mortality in patients. Bone tissue-derived CXCL12 preferentially recruits breast cancer cells expressing CXCR4 to bone metastatic sites. Thus, understanding how CXCR4 expression is regulated in breast cancer cells could suggest approaches to decrease bone metastasis of breast tumor cells. Here, we show that tumor cell-derived angiopoietin-like protein 2 (ANGPTL2) increases responsiveness of breast cancer cells to CXCL12 by promoting up-regulation of CXCR4 in those cells. In addition, we used a xenograft mouse model established by intracardiac injection of tumor cells to show that ANGPTL2 knockdown in breast cancer cells attenuates tumor cell responsiveness to CXCL12 by decreasing CXCR4 expression in those cells, thereby decreasing bone metastasis. Finally, we found that ANGPTL2 and CXCR4 expression levels within primary tumor tissues from breast cancer patients are positively correlated. We conclude that tumor cell-derived ANGPTL2 may increase bone metastasis by enhancing breast tumor cell responsiveness to CXCL12 signaling through up-regulation of tumor cell CXCR4 expression. These findings may suggest novel therapeutic approaches to treat metastatic breast cancer.

Angiopoietin-like protein 2 renders colorectal cancer cells resistant to chemotherapy by activating spleen tyrosine kinase-phosphoinositide 3-kinase-dependent anti-apoptotic signaling.

Angiopoietin-like protein 2 (ANGPTL2) plays an important role in inflammatory carcinogenesis and tumor metastasis by activating tumor angiogenesis and tumor cell chemotaxis and invasiveness. However, it is unclear whether ANGPTL2 expression has an effect on tumor cell survival. Here, we explored that possibility by determining whether ANGPTL2 expression altered survival of human colorectal cancer cell lines treated with antineoplastic drugs. To do so, we generated SW480 cells expressing ANGPTL2 (SW480/ANGPTL2) and control (SW480/Ctrl) cells. Apoptosis induced by antineoplastic drug treatment was significantly decreased in SW480/ANGPTL2 compared to control cells. Expression of anti-apoptotic BCL-2 family genes was upregulated in SW480/ANGPTL2 compared to SW480/Ctrl cells. To assess signaling downstream of ANGPTL2 underlying this effect, we carried out RNA sequencing analysis of SW480/ANGPTL2 and SW480/Ctrl cells. That analysis, combined with in vitro experiments, indicated that Syk-PI3K signaling induced expression of BCL-2 family genes in SW480/ANGPTL2 cells. Furthermore, ANGPTL2 increased its own expression in a feedback loop by activating the spleen tyrosine kinase-nuclear factor of activated T cells (Syk-NFAT) pathway. Finally, we observed a correlation between higher ANGPTL2 expression in primary unresectable tumors from colorectal cancer patients who underwent chemotherapy with a lower objective response rate. These findings suggest that attenuating ANGPTL2 signaling in tumor cells may block tumor cell resistance to antineoplastic therapies.

Serum ANGPTL2 levels reflect clinical features of breast cancer patients: implications for the pathogenesis of breast cancer metastasis.

INTRODUCTION: Breast cancer is a leading cause of cancer-related death in women worldwide, and its metastasis is a major cause of disease mortality. Therefore, identification of the mechanisms underlying breast cancer metastasis is crucial for the development of therapeutic and diagnostic strategies. Our recent study of immunodeficient female mice transplanted with MDA-MB231 breast cancer cells demonstrated that tumor cell-derived angiopoietin-like protein 2 (ANGPTL2) accelerates metastasis through both increasing tumor cell migration in an autocrine/paracrine manner, and enhancing tumor angiogenesis. To determine whether ANGPTL2 contributes to its clinical pathogenesis, we asked whether serum ANGPTL2 levels reflect the clinical features of breast cancer progression. METHODS: We monitored the levels of secreted ANGPTL2 in supernatants of cultured proliferating MDA-MB231 cells. We also determined whether the circulating ANGPTL2 levels were positively correlated with cancer progression in an in vivo breast cancer xenograft model using MDA-MB231 cells. Finally, we investigated whether serum ANGPTL2 levels were associated with clinical features in breast cancer patients. RESULTS: Both in vitro and in vivo experiments showed that the levels of ANGPTL2 secreted from breast cancer cells increased with cell proliferation and cancer progression. Serum ANGPTL2 levels in patients with metastatic breast cancer were significantly higher than those in healthy subjects or in patients with ductal carcinoma in situ or non-metastatic invasive ductal carcinoma. Serum ANGPTL2 levels in patients negative for estrogen receptors and progesterone receptors, particularly triple-negative cases, reflected histological grades. CONCLUSIONS: These findings suggest that serum ANGPTL2 levels in breast cancer patients could represent a potential marker of breast cancer metastasis.

The secreted protein ANGPTL2 promotes metastasis of osteosarcoma cells through integrin α5ß1, p38 MAPK, and matrix metalloproteinases.

The tumor microenvironment can enhance the invasive capacity of tumor cells. We showed that expression of angiopoietin-like protein 2 (ANGPTL2) in osteosarcoma (OS) cell lines increased and the methylation of its promoter decreased with time when grown as xenografts in mice compared with culture. Compared with cells grown in normal culture conditions, the expression of genes encoding DNA demethylation-related enzymes increased in tumor cells implanted into mice or grown in hypoxic, serum-starved culture conditions. ANGPTL2 expression in OS cell lines correlated with increased tumor metastasis and decreased animal survival by promoting tumor cell intravasation mediated by the integrin α5ß1, p38 mitogen-activated protein kinase, and matrix metalloproteinases. The tolloid-like 1 (TLL1) protease cleaved ANGPTL2 into fragments in vitro that did not enhance tumor progression when overexpressed in xenografts. Expression of TLL1 was weak in OS patient tumors, suggesting that ANGPTL2 may not be efficiently cleaved upon secretion from OS cells. These findings demonstrate that preventing ANGPTL2 signaling stimulated by the tumor microenvironment could inhibit tumor cell migration and metastasis.

Angiopoietin-like protein 2 induced by mechanical stress accelerates degeneration and hypertrophy of the ligamentum flavum in lumbar spinal canal stenosis.

Chronic inflammation and subsequent fibrosis induced by mechanical stress play an important role in ligamentum flavum (LF) hypertrophy and degeneration in patients with lumbar spinal canal stenosis (LSCS). Angiopoietin-like protein 2 (Angptl2) is a chronic inflammatory mediator induced under various pathological conditions and increases the expression of TGF-ß1, which is a well-characterized mediator in LF hypertrophy. We investigated whether Angptl2 is induced by mechanical stress, and whether it contributes to LF hypertrophy and degeneration by activating the TGF-ß1 signaling cascade. In this study, we investigated human LF tissue and LF fibroblasts isolated from patients who underwent lumbar surgery. We found that Angptl2 was abundantly expressed in fibroblasts of hypertrophied LF tissues at both the mRNA and protein levels. This expression was not only positively correlated with LF thickness and degeneration but also positively correlated with lumbar segmental motion. Our in vitro experiments with fibroblasts from hypertrophied LF tissue revealed that mechanical stretching stress increases the expression and secretion of Angptl2 via activation of calcineurin/NFAT pathways. In hypertrophied LF tissue, expression of TGF-ß1 mRNA was also increased and TGF-ß1/Smad signaling was activated. Angptl2 expression in LF tissue was positively correlated with the expression of TGF-ß1 mRNA, suggesting cooperation between Angptl2 and TGF-ß1 in the pathogenesis of LF hypertrophy. In vitro experiments revealed that Angptl2 increased levels of TGF-ß1 and its receptors, and also activated TGF-ß1/Smad signaling. Mechanical stretching stress increased TGF-ß1 mRNA expression, which was partially attenuated by treatment with a calcineurin/NFAT inhibitor or Angptl2 siRNA, indicating that induction of TGF-ß1 expression by mechanical stretching stress is partially mediated by Angptl2. We conclude that expression of Angptl2 induced by mechanical stress in LF fibroblasts promotes LF tissue degeneration by activation of TGF-ß1/Smad signaling, which results in LF hypertrophy in patients with LSCS.

Angiopoietin-like protein 2 accelerates carcinogenesis by activating chronic inflammation and oxidative stress.

UNLABELLED: Chronic inflammation has received much attention as a risk factor for carcinogenesis. We recently reported that Angiopoietin-like protein 2 (Angptl2) facilitates inflammatory carcinogenesis and metastasis in a chemically induced squamous cell carcinoma (SCC) of the skin mouse model. In particular, we demonstrated that Angptl2-induced inflammation enhanced susceptibility of skin tissues to "preneoplastic change" and "malignant conversion" in SCC development; however, mechanisms underlying this activity remain unclear. Using this model, we now report that transgenic mice overexpressing Angptl2 in skin epithelial cells (K14-Angptl2 Tg mice) show enhanced oxidative stress in these tissues. Conversely, in the context of this model, Angptl2 knockout (KO) mice show significantly decreased oxidative stress in skin tissue as well as a lower incidence of SCC compared with wild-type mice. In the chemically induced SCC model, treatment of K14-Angptl2 Tg mice with the antioxidant N-acetyl cysteine (NAC) significantly reduced oxidative stress in skin tissue and the frequency of SCC development. Interestingly, K14-Angptl2 Tg mice in the model also showed significantly decreased expression of mRNA encoding the DNA mismatch repair enzyme Msh2 compared with wild-type mice and increased methylation of the Msh2 promoter in skin tissues. Msh2 expression in skin tissues of Tg mice was significantly increased by NAC treatment, as was Msh2 promoter demethylation. Overall, this study strongly suggests that the inflammatory mediator Angptl2 accelerates chemically induced carcinogenesis through increased oxidative stress and decreased Msh2 expression in skin tissue. IMPLICATIONS: Angptl2-induced inflammation increases susceptibility to microenvironmental changes, allowing increased oxidative stress and decreased Msh2 expression; therefore, Angptl2 might be a target to develop new strategies to antagonize these activities in premalignant tissue.

Tumor cell-derived angiopoietin-like protein ANGPTL2 is a critical driver of metastasis.

Strategies to inhibit metastasis have been mainly unsuccessful in part due to insufficient mechanistic understanding. Here, we report evidence of critical role for the angiopoietin-like protein 2 (ANGPTL2) in metastatic progression. In mice, Angptl2 has been implicated in inflammatory carcinogenesis but it has not been studied in human tumors. In patients with lung cancer, elevated levels of ANGPTL2 expression in tumor cells within the primary tumor were associated with a reduction in the period of disease-free survival after surgical resection. Transcription factors NFATc, ATF2, and c-Jun upregulated in aggressive tumor cells promoted increased Angptl2 expression. Most notably, tumor cell-derived ANGPTL2 increased in vitro motility and invasion in an autocrine/paracrine manner, conferring an aggressive metastatic tumor phenotype. In xenograft mouse models, tumor cell-derived ANGPTL2 accelerated metastasis and shortened survival whereas attenuating ANGPTL2 expression in tumor cells-blunted metastasis and extended survival. Overall, our findings showed that tumor cell-derived ANGPTL2 drives metastasis and provided an initial proof of concept for blockade of its action as a strategy to antagonize the metastatic process.