Thomas Freude

Transforming growth factor β1 inhibits bone morphogenic protein (BMP)-2 and BMP-7 signaling via upregulation of Ski-related novel protein N (SnoN): possible mechanism for the failure of BMP therapy?

BackgroundBone morphogenic proteins (BMPs) play a key role in bone formation. Consequently, it was expected that topical application of recombinant human (rh)BMP-2 and rhBMP-7 would improve the healing of complex fractures. However, up to 36% of fracture patients do not respond to this therapy. There are hints that a systemic increase in transforming growth factor β1 (TGFβ1) interferes with beneficial BMP effects. Therefore, in the present work we investigated the influence of rhTGFβ1 on rhBMP signaling in primary human osteoblasts, with the aim of more specifically delineating the underlying regulatory mechanisms.MethodsBMP signaling was detected by adenoviral Smad-binding-element-reporter assays. Gene expression was determined by reverse transcription polymerase chain reaction (RT-PCR) and confirmed at the protein level by western blot. Histone deacetylase (HDAC) activity was determined using a test kit. Data sets were compared by one-way analysis of variance.ResultsOur findings showed that Smad1/5/8-mediated rhBMP-2 and rhBMP-7 signaling is completely blocked by rhTGFβ1. We then investigated expression levels of genes involved in BMP signaling and regulation (for example, Smad1/5/8, TGFβ receptors type I and II, noggin, sclerostin, BMP and activin receptor membrane bound inhibitor (BAMBI), v-ski sarcoma viral oncogene homolog (Ski), Ski-related novel protein N (SnoN) and Smad ubiquitination regulatory factors (Smurfs)) and confirmed the expression of regulated genes at the protein level. Smad7 and SnoN were significantly induced by rhTGFβ1 treatment while expression of Smad1, Smad6, TGFβRII and activin receptor-like kinase 1 (Alk1) was reduced. Elevated SnoN expression was accompanied by increased HDAC activity. Addition of an HDAC inhibitor, namely valproic acid, fully abolished the inhibitory effect of rhTGFβ1 on rhBMP-2 and rhBMP-7 signaling.ConclusionsrhTGFβ1 effectively blocks rhBMP signaling in osteoblasts. As possible mechanism, we postulate an induction of SnoN that increases HDAC activity and thereby reduces the expression of factors required for efficient BMP signaling. Thus, inhibition of HDAC activity may support bone healing during rhBMP therapy in patients with elevated TGFβ serum levels.

Quercetin Protects Primary Human Osteoblasts Exposed to Cigarette Smoke through Activation of the Antioxidative Enzymes HO-1 and SOD-1

Smokers frequently suffer from impaired fracture healing often due to poor bone quality and stability. Cigarette smoking harms bone cells and their homeostasis by increased formation of reactive oxygen species (ROS). The aim of this study was to investigate whether Quercetin, a naturally occurring antioxidant, can protect osteoblasts from the toxic effects of smoking. Human osteoblasts exposed to cigarette smoke medium (CSM) rapidly produced ROS and their viability decreased concentration- and time-dependently. Co-, pre- and postincubation with Quercetin dose-dependently improved their viability. Quercetin increased the expression of the anti-oxidative enzymes heme-oxygenase- (HO-) 1 and superoxide-dismutase- (SOD-) 1. Inhibiting HO-1 activity abolished the protective effect of Quercetin. Our results demonstrate that CSM damages human osteoblasts by accumulation of ROS. Quercetin can diminish this damage by scavenging the radicals and by upregulating the expression of HO-1 and SOD-1. Thus, a dietary supplementation with Quercetin could improve bone matter, stability and even fracture healing in smokers.

Factors circulating in the blood of type 2 diabetes mellitus patients affect osteoblast maturation - Description of a novel in vitro model

Type 2 diabetes mellitus (T2DM) is one of the most frequent metabolic disorders in industrialized countries. Among other complications, T2DM patients have an increased fracture risk and delayed fracture healing. We have demonstrated that supraphysiological glucose and insulin levels inhibit primary human osteoblasts׳ maturation. We aimed at developing a more physiologically relevant in vitro model to analyze T2DM-mediated osteoblast changes. Therefore, SCP-1-immortalized pre-osteoblasts were differentiated with T2DM or control (non-obese and obese) sera. Between both control groups, no significant changes were observed. Proliferation was significantly increased (1.69-fold), while AP activity and matrix mineralization was significantly reduced in the T2DM group. Expression levels of osteogenic marker genes and transcription factors were altered, e.g. down-regulation of RUNX2 and SP-7 or up-regulation of STAT1, in the T2DM group. Active TGF-β levels were significantly increased (1.46-fold) in T2DM patients׳ sera. SCP-1 cells treated with these sera showed significantly increased TGF-β signaling (2.47-fold). Signaling inhibition effectively restored osteoblast maturation in the T2DM group. Summarizing our data, SCP-1 cells differentiated in the presence of T2DM patients׳ serum exhibit reduced osteoblast function. Thus, this model has a high physiological impact, as it can identify circulating factors in T2DM patients׳ blood that may affect bone function, e.g. TGF-β.

Balloon osteoplasty—a new technique for reduction and stabilisation of impression fractures in the tibial plateau: A cadaver study and first clinical application

PurposeFractures of the tibial plateau are among the most severe injuries of the knee joint and lead to advanced gonarthrosis if the reduction does not restore perfect joint congruency. Many different reduction techniques focusing on open surgical procedures have been described in the past. In this context we would like to introduce a novel technique which was first tested in a cadaver setup and has undergone its successful first clinical application.MethodsSince kyphoplasty demonstrated effective ways of anatomical correction in spine fractures, we adapted the inflatable instruments and used the balloon technique to reduce depressed fragments of the tibial plateau.ResultsThe technique enabled us to restore a congruent cartilage surface and bone reduction.ConclusionsIn this technique we see a useful new method to reduce depressed fractures of the tibial plateau with the advantages of low collateral damage as it is known from minimally invasive procedures.

BMP9 a possible alternative drug for the recently withdrawn BMP7? New perspectives for (re-)implementation by personalized medicine.

Promotion of rhBMP2 and rhBMP7 for the routine use to support fracture healing has been hampered by high costs, safety concerns and reasonable failure rates, imposing restrictions in its clinical use. Since there is little debate regarding its treatment potential, there is rising need for a better understanding of the mode of action of these BMPs to overcome its drawbacks and promote more efficacious treatment strategies for bone regeneration. Recently, BMP9, owing to its improved osteogenic potential, is gaining attention as a promising therapeutic alternative. Our study aimed at identifying specific gene expression patterns which may predict and explain individual responses to rhBMP7 and rhBMP9 treatments. Therefore, we investigated the effect of rhBMP7 and rhBMP9 on primary human osteoblasts from 110 donors and corresponding THP-1-derived osteoclasts. This was further compared with each other and our reported data on rhBMP2 response. Based on the individual donor response, we found three donor groups profiting from rhBMP treatment either directly via stimulation of osteoblast function or viability and/or indirectly via inhibition of osteoclasts. The response on rhBMP7 treatment correlated with expression levels of the genes BAMBI, SOST, Noggin, Smad4 and RANKL, while the response of rhBMP9 correlated to the expression levels of Alk6, Endoglin, Smurf1, Smurf2, SOST and RANKL in these donors. Noteworthy, rhBMP9 treatment showed significantly increased osteogenic activity (AP activity and Smad nuclear translocation) when compared to the two clinically used rhBMPs. Based on patient’s respective expression profiles, clinical application of rhBMP9 either solely or in combination with rhBMP2 and/or rhBMP7 can become a promising new approach to fit the patient’s needs to promote fracture healing.

DLS 5.0 - The Biomechanical Effects of Dynamic Locking Screws

Introduction Indirect reduction of dia-/metaphyseal fractures with minimally invasive implant application bridges the fracture zone in order to protect the soft-tissue and blood supply. The goal of this fixation strategy is to allow stable motion at the fracture site to achieve indirect bone healing with callus formation. However, concerns have arisen that the high axial stiffness and eccentric position of locked plating constructs may suppress interfragmentary motion and callus formation, particularly under the plate. The reason for this is an asymmetric fracture movement. The biological need for sufficient callus formation and secondary bone healing is three-dimensional micro movement in the fracture zone. The DLS was designed to allow for increased fracture site motion. The purpose of the current study was to determine the biomechanical effect of the DLS_5.0. Methods Twelve surrogate bone models were used for analyzing the characteristics of the DLS_5.0. The axial stiffness and the interfragmentary motion of locked plating constructs with DLS were compared to conventional constructs with Locking Head Screws (LS_5.0). A quasi-static axial load of 0 to 2.5 kN was applied. Relative motion was measured. Results The dynamic system showed a biphasic axial stiffness distribution and provided a significant reduction of the initial axial stiffness of 74.4%. Additionally, the interfragmentary motion at the near cortex increased significantly from 0.033 mm to 0.210 mm (at 200N). Conclusions The DLS may ultimately be an improvement over the angular stable plate osteosynthesis. The advantages of the angular stability are not only preserved but even supplemented by a dynamic element which leads to homogenous fracture movement and to a potentially uniform callus distribution.

Reconstruction of displaced acromio-clavicular joint dislocations using a triple suture-cerclage: description of a safe and efficient surgical technique

PurposeIn this retrospective study we investigated the clinical and radiological outcome after operative treatment of acute Rockwood III-V injuries of the AC-joint using two acromioclavicular (AC) cerclages and one coracoclavicular (CC) cerclage with resorbable sutures.MethodsBetween 2007 and 2009 a total of 39 patients fit the inclusion criteria after operative treatment of acute AC joint dislocation. All patients underwent open reduction and anatomic reconstruction of the AC and CC-ligaments using PDS® sutures (Polydioxane, Ethicon, Norderstedt, Germany). Thirty-three patients could be investigated at a mean follow up of 32±9 months (range 24–56 months).ResultsThe mean Constant score was 94.3±7.1 (range 73–100) with an age and gender correlated score of 104.2%±6.9 (88-123%). The DASH score (mean 3.46±6.6 points), the ASES score (94.6±9.7points) and the Visual Analogue Scale (mean 0.5±0,6) revealed a good to excellent clinical outcome. The difference in the coracoclavicular distance compared to the contralateral side was <5 mm for 28 patients, between 5-10 mm for 4 patients, and more than 10 mm for another patient. In the axial view, the anterior border of the clavicle was within 1 cm (ventral-dorsal direction) of the anterior rim of the acromion in 28 patients (85%). Re-dislocations occured in three patients (9%).ConclusionOpen AC joint reconstruction using AC and CC PDS cerclages provides good to excellent clinical results in the majority of cases. However, radiographically, the CC distance increased significantly at final follow up, but neither the amount of re-dislocation nor calcifications of the CC ligaments or osteoarthritis of the AC joint had significant influence on the outcome.Level of evidenceCase series, Level IV

Anti-diabetic treatment regulates pro-fibrotic TGF-β serum levels in type 2 diabetics

BackgroundThe single-center, open-label, four-arm, exploratory study investigates the relation of different anti-diabetics to serum levels of active TGF-β, a known pro-fibrotic stimulus, before and after a defined test meal.FindingsWe investigated sera of patients with type 2 diabetes mellitus (T2DM) treated with metformin and sulfonylurea, insulin glargine or a DPP-4 inhibitor (DPP4i). Patients’ sera were analyzed before and 5 h after a defined test meal at intervals of 30 min.The sulfonylurea/metformin group exhibited the highest basal levels of active TGF-β (31.50 ± 3.58 ng/ml). The glargine/metformin group had active TGF-β levels (24.98 ± 1.90 ng/ml) that were comparable to those of the healthy participants (22.12 ± 2.34 ng/ml). The lowest basal levels of active TGF-β were detected in the DPP-4i/metformin group (12.28 ± 0.84 ng/ml). Following the intake of a standardized meal, active TGF-β levels decreased (approx. 30%) in healthy subjects as well as in the sulfonylurea/metformin group and in the glargine/metformin group. After 5 h, the active TGF-β levels were normalized to basal levels. Active TGF-β levels in the DPP-4i/metformin group did not change significantly after the test meal. Overall plasma levels of insulin and proinsulin were comparable between healthy participants, and T2DM patients in the glargin/metformin group and in the DPP4i/metformin group. However, no correlation between active TGF-β levels, glucose, insulin or pro-insulin levels was detected.ConclusionsT2DM patients often exhibit elevated levels of pro-fibrotic active TGF-β. Our results suggest that glargine/metformin and DPP4i/metformin treatment may more effectively reduce active TGF-β serum levels than the sulfonylurea/metformin treatment.

Insufficiency fractures of the pelvic ring

The demographic changes in society automatically lead to an increase in specific diseases and injuries in the older generation. Therefore, the proportion of osteoporotic and fatigue fractures increases in total and also the absolute number of insufficiency fractures of the pelvic ring. In younger people pelvic ring fractures are mostly due high speed trauma. In the elderly this often occurs by low energy trauma or even with no trauma which is then designated as insufficiency fracture. The problematic of such fractures is insufficiently covered in the conventional classification. Conventional radiological diagnostics must often be supplemented by slice imaging procedures. The therapy forms must be more closely adapted to the general condition and physical health of the patient than by classical fractures and the substantially reduced sustainability of osteosynthesis in altered bones must be taken into consideration.ZusammenfassungDie demografischen Veränderungen unserer Gesellschaft führen zwangsläufig zu einer Zunahme der spezifischen Erkrankungen und Verletzungen der älteren Generation. So steigt auch der prozentuale Anteil an osteoporotischen und Ermüdungsfrakturen insgesamt und damit die absolute Anzahl der Insuffizienzfrakturen des Beckenrings. Beim jungen Menschen ist eine Beckenringfraktur meist Folge eines Hochrasanztraumas. Im Alter kommt es oft bereits bei Niedrigenergietraumen oder gar ohne Trauma zu dieser Verletzung, welche dann als Insuffizienzfraktur zu werten ist, deren Problematik in der konventionellen Klassifikation nicht ausreichend abgebildet wird. Oft muss die konventionelle radiologische Diagnostik durch schnittbildgebende Verfahren ergänzt werden. Die Therapieformen müssen stärker als bei den klassischen Frakturen an den Allgemeinzustand und die Lebensumstände des Patienten angepasst werden und die deutlich verminderte Haltekraft der Osteosynthesen im veränderten Knochen berücksichtigen.AbstractThe demographic changes in society automatically lead to an increase in specific diseases and injuries in the older generation. Therefore, the proportion of osteoporotic and fatigue fractures increases in total and also the absolute number of insufficiency fractures of the pelvic ring. In younger people pelvic ring fractures are mostly due high speed trauma. In the elderly this often occurs by low energy trauma or even with no trauma which is then designated as insufficiency fracture. The problematic of such fractures is insufficiently covered in the conventional classification. Conventional radiological diagnostics must often be supplemented by slice imaging procedures. The therapy forms must be more closely adapted to the general condition and physical health of the patient than by classical fractures and the substantially reduced sustainability of osteosynthesis in altered bones must be taken into consideration.

Precision in the Planning of Open Wedge HTO

INTRODUCTION The high tibial osteotomy (HTO) is regarded as an established method for varus deformity. To quantify the varus deformity, the anatomic and the mechanical leg axis can be determined. The success of HTO depends on the correct assessment of the preoperative axis deviation and the exact as planned correction. The aim of the retrospective study was to verify the accuracy (± 1.5° of mechanical tibiofemoral angle tolerance compared to the planning) with the preoperative planning compared to the postoperative result after correction using the TomoFix™ plate in open wedge HTO. MATERIALS AND METHOD A retrospective study of patients was carried out after open wedge HTO with the TomoFix™ plate. A full-weight bearing, long-standing anteroposterior radiograph of the whole lower extremity was performed before and after correction. The mechanical angles in the frontal plane were determined and compared with the plan as drawn. RESULTS The preoperative mechanical tibiofemoral angle (mTFA) was -5.33 ± 3.29° (varus) and at follow-up -0.3 ± 3.0° (varus). The mean correction was 4.9 ± 2.9°. The planned mTFA was 2.2 ± 1.6°(valgus). The corrected lower extremity showed a mean difference of -2.5 ± 3.4° in angle correction of the varus deformity as preoperatively assumed to be the optimal correction compared to the planning. The planning goal was not achieved in 73 % of the cases. CONCLUSION The results are comparable to those of other publications. However, taking into account the required accuracy of the drawn plan combined with the surgical precedure, it is not possible to achieve results within the desired tolerance.