High-purity magnesium screws modulate macrophage polarization during the tendon-bone healing process in the anterior cruciate ligament reconstruction rabbit model.

Magnesium (Mg) screws perform clinical potential in anterior cruciate ligament (ACL) reconstruction, and promote fibrocartilaginous entheses regeneration at the femoral entrance. We aim to prove that high-purity Magnesium (HP Mg) screws modulate macrophage polarization in fibrocartilage interface regeneration both in vitro and in vivo. HP Mg extracts performed good cytocompatibility and significantly promoted M2 macrophage polarization in the flow cytometry and ELISA assays. M2 macrophages stimulated fibrochondrocyte differentiation of co-cultured hBMSCs, and HP Mg extracts had synergistic effect on the process. Then we applied HP Mg screws, with Ti screws as control, in the ACL reconstruction rabbit model. In the histological and immunofluorescence analysis, HP Mg screws inhibited M1 polarization at 2 weeks and highly promoted M2 polarization at 2 and 4 weeks at the tendon-bone interface. Furthermore, regeneration of fibrocartilaginous entheses, rather than the fibrovascular scar interface, was detected in the HP Mg group at 12 weeks. For further mechanism study via RNA-seq detection and WB assays, we found that AKT1 was highly activated in M2 polarization, and HP Mg could stimulate AKT1 expression, rather than AKT2, in the early phase of tendon-bone healing. Our study elucidated macrophage polarization during tendon-bone healing process and emphasized HP Mg on M2 polarization and fibrocartilage interface regeneration via the selective activation of AKT1 and PI3K/AKT pathway.

Cancellous bone allograft is comparable to fibular strut allograft for augmentation in three- or four-part proximal humeral fractures.

BACKGROUND: Bone grafts have been used for augmentation and improving stability of reduced fractures in proximal humeral fractures. The aim of this study was to analyze the clinical and radiological outcomes after the use of cancellous bone allografts (CAs) for augmentation in 3- or 4-part proximal humeral fractures, and compare with fibular strut allografts (FAs). METHODS: Between November 2016 and February 2018, 55 patients, followed for at least 1 year, with 3- or 4-part proximal humeral fractures fixed with locking plates were included and grouped according to the type of allograft bone used for augmentation. In this retrospective analysis, we assessed and compared the clinical and radiological outcomes of the 2 groups, using the visual analog scale score, the Constant-Murley score (CMS), the disability of the arm, shoulder, and hand (DASH) score, the range of movement, neck-shaft angle (NSA), humeral head height (HHH), and the changes of NSA and HHH, as well as recording any complications. The repeatedly measured clinical and radiological outcomes were analyzed by linear mixed models. The differences in outcomes between groups at the final follow-up were compared using Student's t test. RESULTS: There were 28 patients in the CA group and 27 patients in the FA group with an average follow-up of 14.5 months. The mean age of all patients was 64 (36-86). Nonsignificant group effects were observed on CMS (ß = -8.792, P = .216), DASH (ß = 1.329, P = .094), NSA (ß = 1.432, P = .752), and HHH (ß = 1.660, P = .628). At the final follow-up, the patients in the CA group showed no significant differences in visual analog scale (1.8 vs. 2.2, P = .276), CMS (81.5 vs. 75.4, P = .072), and DASH (11.0 vs. 13.5, P = .235) scores compared with the FA group. There were no significant differences in the change of NSA (6 vs. 4, P = .387) or HHH (1 vs. 2, P = .261). CONCLUSIONS: Patients with 3- or 4-part proximal humeral fractures treated with locking plates combined with CAs have good clinical and radiographic outcomes, similar to those treated with FAs.

All-Trans Retinoic Acid Promotes Osteogenic Differentiation and Bone Consolidation in a Rat Distraction Osteogenesis Model.

Distraction osteogenesis (DO) is used to treat specific disorders associated with growth abnormalities and/or loss of bone stock secondary to trauma or disease. However, a high rate of complications and discomfort hamper its further application in clinical practice. Here, we investigated the effects of all-trans retinoic acid (ATRA) on osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (rBMSCs) and bone consolidation in a rat DO model. Different doses of ATRA were used to treat rBMSCs. Cell viability and osteogenic differentiation were assessed using CCK-8 and alkaline phosphatase staining, respectively. The mRNA expression of osteogenic differentiation-genes (including ALP, Runx2, OCN, OPN, OSX, and BMP2) and angiogenic genes (including VEGF, HIF-1, FLK-2, ANG-2, and ANG-4) were determined by quantitative real-time PCR analysis. Further, we locally injected ATRA or PBS into the gap in the rat DO model every 3 days until termination. X-rays, micro-computed tomography (Micro-CT), mechanical testing, and immunohistochemistry stains were used to evaluate the quality of the regenerates. ATRA promoted osteogenic differentiation of rBMSCs. Moreover, ATRA elevated the mRNA expression levels of osteogenic differentiation-genes and angiogenic genes. In the rat model, new bone properties of bone volume/total tissue volume and mechanical strength were significantly higher in the ATRA-treatment group. Micro-CT examination showed more mineralized bone after the ATRA-treatment, and immunohistochemistry demonstrated more new bone formation after ATRA-treatment than that in the PBS group. In conclusion, as a readily available and very cost effective bio-source, ATRA may be a novel therapeutic method to enhance bone consolidation in the clinical setting.

All-trans retinoic acid improves the viability of ischemic skin flaps in diabetic rat models.

AIMS: Endothelial progenitor cells (EPCs) play a critical role in neovascularization, which enhances proliferation under all-trans retinoic acid (ATRA) treatment. However, the effects of ATRA on the skin flap survival in diabetic flap ischemia remains unknown. METHODS: Ischemic random skin flaps were made in 40 diabetic Sprague-Dawley rats with 20 normal rats used as control in this study. At 7 days postoperatively, the surviving area of each skin flap was measured. Immunofluorescence staining was used to analyze capillary density and EPCs recruited to the flaps. The expression of ANG2 and VEGF was determined by Western blotting. Circulating EPC number was determined by flow cytometry. In vitro tube formation experiment was used to analyze the function of EPCs. RESULTS: The flap survival rate and capillary density of ATRA-treated flap were significantly increased. Fluorescence-activated cell sorting (FACS) analysis demonstrated a marked increase in systemic CD34+/Flk-1+ EPCs in ATRA-treated rat. The expression of ANG2 and VEGF was increased in diabetic flap tissues under ATRA administration. Furthermore, ATRA administration restored the impaired function of diabetic EPCs in tube formation. CONCLUSION: ATRA could notably exert preventive effects against skin flap necrosis and promote neovascularization in diabetic rats, which may partially through elevating the expression of ANG2 and VEGF, and augmenting EPC mobilization.

Baicalin alleviates osteomyelitis by regulating TLR2 in the murine model.

Osteomyelitis is an inflammation of bone caused by invading organisms. TLR2, inflammatory cytokines and mitogen-activated protein kinase (MAPK) signaling pathway are involved in osteomyelitis. Baicalin, the major active constituent of the isolated root of Scutellaria lateriflora Georgi, has been shown to have anti-inflammatory effects. In this study, the potentials of baicalin against osteomyelitis were evaluated. We treated mice and MC3T3-E1 cells with baicalin together with Staphylococcus aureus infection, and then analyzed the mice bone destruction, the expressions of TLR2 and osteogenic marker, the serum levels of proinflammatory factors and activation of MAPK signaling pathway. We also knocked down TLR2 by shRNA in MC3T3-E1 cells and detected the role of TLR2 in baicalin mediated inhibition of osteomyelitis. It was found that baicalin alleviated bone destruction in osteomyelitis. Baicalin decreased TLR2, alkaline phosphatase, osteopontin and collagen type I expressions. Baicalin decreased serum levels of proinflammatory factors IL-1ß, IL-6 and CRP. Baicalin inhibited activation of MAPK signaling pathway. The inhibition of osteomyelitis by baicalin depended on TLR2 inhibition. In summary, baicalin is able to alleviate osteomyelitis by regulating TLR2.