Effect of low molecular weight heparin (dalteparin) and fondaparinux (Arixtra) on human osteoblasts in vitro

Pregnancy-associated osteoporosis following in vitro fertilization: A case report

This case report illustrates that in vitro fertilization (IVF) may be a potential risk factor for pregnancy-associated osteoporosis (PAO), highlighting the need for awareness and monitoring of bone health in women undergoing IVF treatments. PAO is a rare disease resulting from an imbalance of calcium in the body during pregnancy and lactation and presenting with fragility fractures. PAO occurs in late pregnancy or early postpartum period. A 28-year-old woman who conceived through IVF experienced severe back pain 2 days after delivery. Magnetic resonance imaging of the spine showed wedge-shaped fractures of T9-T12 vertebrae. Bone mineral density (BMD) was low on dual-energy x-ray absorptiometry. The laboratory tests were within the normal range. Based on the clinical manifestations, osteoporotic spine fracture, results of BMD, and exclusion of other causes of osteoporosis, the patient was diagnosed with PAO. Considering the deleterious effect of treatment with gonadotropin-releasing hormone and repeated superovulation on bone, we hypothesized that IVF may be an etiological factor for PAO.

Lipid and Bone Effects of Heparin Use During Hemodialysis

Unfractionated heparin (UFH) and low-molecular-weight heparins (LMWHs) are commonly prescribed anticoagulants for chronic hemodialysis (HD). The dialysis population comprises a unique group that receives heparin three times per week for a long period, with potential long-term cumulative metabolic effects such as osteoporosis and worsening lipid profile. HD patients have approximately half the number of lipases as healthy individuals, and their lipid metabolism is limited because of this decrease as well as partially inhibited function. Administration of UFH or LMWHs for anticoagulation can lead to metabolic starvation despite high triglyceride levels at the end of HD. In vitro studies indicate that UFH and LMWHs inhibit osteoblasts and promote osteoclasts. In patients on HD, long-term use of UFH or LMWHs did not worsen chronic kidney disease-mineral bone disease. Further investigation is needed to elucidate the underlining mechanisms of UFH and LMWHs and their possible influences on maintenance HD patients.

The effect of drugs on implant osseointegration- A narrative review

OBJECTIVE

This narrative review aims to investigate the effects of drugs on implant osseointegration, analyzing their potential positive or negative impact on the direct structural and functional connection between bone and load-carrying implants.

BACKGROUND

The review seeks to provide a comprehensive understanding of osseointegration, which refers to the successful integration of an implant with living bone, resulting in no progressive relative movement between them. Exploring the effects of drugs on implant osseointegration is crucial for optimizing outcomes and enhancing patient care in orthopedic implant procedures.

METHODS

Relevant studies on the effects of drugs on implant osseointegration were identified through a literature search. Electronic databases, including PubMed, Embase, and Google Scholar, were utilized, employing appropriate keywords and MeSH terms related to osseointegration, implants, and drug interventions. The search was limited to English studies.

DISCUSSION

This overview presents a detailed analysis of the effects of drugs on implant osseointegration. It explores drugs such as bisphosphonates, teriparatide, statins, angiotensin-converting enzyme inhibitors, beta-blockers, nitrites, and thiazide diuretics as promoters of osseointegration. Conversely, loop diuretics, non-steroidal anti-inflammatory drugs, corticosteroids, cyclosporine A, cisplatin, methotrexate, antibiotics, proton pump inhibitors (PPIs), antiepileptics, selective serotonin reuptake inhibitors (SSRIs), and anticoagulants are discussed as inhibitors of the process. The role of vitamin D3 remains uncertain. The complex relationship between drugs and the biology of implant osseointegration is emphasized, underscoring the need for further in vitro and in vivo studies to validate their effects CONCLUSION: This narrative review contributes to the literature by providing an overview of the effects of drugs on implant osseointegration. It highlights the complexity of the subject and emphasizes the necessity for more extensive and sophisticated studies in the future. Based on the synthesis of the reviewed literature, certain drugs, such as bisphosphonates and teriparatide, show potential for promoting implant osseointegration, while others, including loop diuretics and certain antibiotics, may impede the process. However, additional research is required to solidify these conclusions and effectively inform clinical practice.

Molybdenum as a Potential Biocompatible and Resorbable Material for Osteosynthesis in Craniomaxillofacial Surgery-An In Vitro Study

Titanium and stainless steel are commonly known as osteosynthesis materials with high strength and good biocompatibility. However, they have the big disadvantage that a second operation for hardware removal is necessary. Although resorbable systems made of polymers or magnesium are increasingly used, they show some severe adverse foreign body reactions or unsatisfying degradation behavior. Therefore, we started to investigate molybdenum as a potential new biodegradable material for osteosynthesis in craniomaxillofacial surgery. To characterize molybdenum as a biocompatible material, we performed in vitro assays in accordance with ISO Norm 10993-5. In four different experimental setups, we showed that pure molybdenum and molybdenum rhenium alloys do not lead to cytotoxicity in human and mouse fibroblasts. We also examined the degradation behavior of molybdenum by carrying out long-term immersion tests (up to 6 months) with molybdenum sheet metal. We showed that molybdenum has sufficient mechanical stability over at least 6 months for implants on the one hand and is subject to very uniform degradation on the other. The results of our experiments are very promising for the development of new resorbable osteosynthesis materials for craniomaxillofacial surgery based on molybdenum.

Low-Molecular-Weight Heparins (LMWH) and Synthetic Factor X Inhibitors Can Impair the Osseointegration Process of a Titanium Implant in an Interventional Animal Study

Background and objectives: Cementless total hip arthroplasty is a common surgical procedure and perioperative thromboprophylaxis is used to prevent deep vein thrombosis or pulmonary embolism. Osseointegration is important for long-term implant survival, and there is no research on the effect of different thromboprophylaxis agents on the process of osseointegration. Materials and Methods: Seventy rats were allocated as follows: Group I (control group), Group II (enoxaparin), Group III (nadroparin), and Group IV (fondaparinux). Ovariectomy was performed on all subjects, followed by the introduction of an intramedullary titanium implant into the femur. Thromboprophylaxis was administered accordingly to each treatment group for 35 days postoperatively. Results: Group I had statistically significantly lower anti-Xa levels compared to treatment groups. Micro-CT analysis showed that nadroparin had lower values compared to control in bone volume (0.12 vs. 0.21, p = 0.01) and percent bone volume (1.46 vs. 1.93, p = 0.047). The pull-out test showed statistically significant differences between the control group (8.81 N) compared to enoxaparin, nadroparin, and fondaparinux groups (4.53 N, 4 N and 4.07 N, respectively). Nadroparin had a lower histological cortical bone tissue and a higher width of fibrous tissue (27.49 μm and 86.9 μm) at the peri-implant area, compared to control (43.2 μm and 39.2 μm), enoxaparin (39.6 μm and 24 μm), and fondaparinux (36.2 μm and 32.7 μm). Conclusions: Short-term administration of enoxaparin, nadroparin, and fondaparinux can reduce the osseointegration of titanium implants, with nadroparin having the most negative effect. These results show that enoxaparin and fondaparinux are preferred to be administered due to a lesser negative impact on the initial implant fixation.

Heparin and Heparin-Based Drug Delivery Systems: Pleiotropic Molecular Effects at Multiple Drug Resistance of Osteosarcoma and Immune Cells

One of the main problems of modern health care is the growing number of oncological diseases both in the elderly and young population. Inadequately effective chemotherapy, which remains the main method of cancer control, is largely associated with the emergence of multidrug resistance in tumor cells. The search for new solutions to overcome the resistance of malignant cells to pharmacological agents is being actively pursued. Another serious problem is immunosuppression caused both by the tumor cells themselves and by antitumor drugs. Of great interest in this context is heparin, a biomolecule belonging to the class of glycosaminoglycans and possessing a broad spectrum of biological activity, including immunomodulatory and antitumor properties. In the context of the rapid development of the new field of “osteoimmunology,” which focuses on the collaboration of bone and immune cells, heparin and delivery systems based on it may be of intriguing importance for the oncotherapy of malignant bone tumors. Osteosarcoma is a rare but highly aggressive, chemoresistant malignant tumor that affects young adults and is characterized by constant recurrence and metastasis. This review describes the direct and immune-mediated regulatory effects of heparin and drug delivery systems based on it on the molecular mechanisms of (multiple) drug resistance in (onco) pathological conditions of bone tissue, especially osteosarcoma.

The anti-cancer properties of heparin and its derivatives: a review and prospect

Heparin, including unfractionated heparin (UFH), low-molecular-weight heparin (LMWH) and heparin derivatives, are commonly used in venous thromboembolism treatment and reportedly have beneficial effects on cancer survival. Heparin can affect the proliferation, adhesion, angiogenesis, migration and invasion of cancer cells via multiple mechanisms. The main mechanisms involve inhibition of heparanase, P-/L-selectin, angiogenesis, and interference with the CXCL12-CXCR4 axis. Here we summarize the current experimental evidence regarding the anti-cancer role of heparin and its derivatives, and conclude that there is evidence to support heparin’s role in inhibiting cancer progression, making it a promising anti-cancer agent.

Effects of Anticoagulant Medication on Bone-Healing

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A substantial proportion of patients undergoing orthopaedic care are prescribed some form of anticoagulant medication, whether for perioperative venous thromboembolism prophylaxis or chronic anticoagulation in the setting of a cardiac or other condition.

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An abundance of preclinical data suggests that many commonly used anticoagulant medications may have a harmful effect on bone-healing.

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The orthopaedic surgeon should be informed and mindful of the added variable that anticoagulation may play in the outcomes of fracture treatment and bone-healing.

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Heparin and warfarin appear to have a greater detrimental impact than low-molecular-weight heparin. Factor Xa inhibitors may confer the least risk, with some studies even suggesting the potential for enhancement of bone-healing.

Anticoagulants and Osteoporosis

Anticoagulant agents are widely used in the treatment of thromboembolic events and in stroke prevention. Data about their effects on bone tissue are in some cases limited or inconsistent (oral anti-vitamin K agents), and in others are sufficiently strong (heparins) to suggest caution in their use in subjects at risk of osteoporosis. This review analyses the effects of this group of drugs on bone metabolism, on bone mineral density, and on fragility fractures. A literature search strategy was developed by an experienced team of specialists by consulting the MEDLINE platform, including published papers and reviews updated to March 2019. Literature supports a detrimental effect of heparin on bone, with an increase in fracture rate. Low molecular weight heparins (LMWHs) seem to be safer than heparin. Although anti-vitamin K agents (VKAs) have a significant impact on bone metabolism, and in particular, on osteocalcin, data on bone mineral density (BMD) and fractures are contrasting. To date, the new direct oral anticoagulants (DOACs) are found to safe for bone health.

Effect of antithrombotic drugs on bone health

With the increasing consumption of antithrombotic drugs among old people, expected as well as unexpected side effects on bone health are considerable, e.g. osteoporosis, fragility fractures, etc. This review focuses on antithrombotic drugs and their effects on bone health. The following groups were reviewed: parenteral long-term use of unfractionated heparin (UFH) is associated with osteopenia. The oral intake of vitamin K antagonists (VKA) makes them more convenient than UFH but chronic use also results in osteopenia. Limited reports of bone loss have been associated with low molecular weight heparins (LMWH) and indirect factor Xa inhibitors but in contrast to VKA and UFH they are less associated with osteopenia. There have been limited studies evaluating the effect of new oral anticoagulants (NOACs) on bones. Overall, they are considered safer than other drugs. There have been no reports about acetylsalicylic acid (ASA) and clopidogrel causing osteopenia but their metabolism by the kidneys and liver can cause reduced 25-hydroxy-vitamin D levels and can theoretically contribute to osteoporosis. Some reports suggested that high dosage clopidogrel can also negatively affect bones. After a detailed literature review long-term use of antithrombotic drugs can negatively affect the bones. Their role in bone health needs to be studied in detail and the clinical use in geriatric patients should be prudent.

Pregnancy-associated osteoporosis: a UK case series and literature review

Mini Abstract: Pregnancy-associated osteoporosis (PAO) is a rare syndrome affecting women during late pregnancy and the early postpartum period. We set out to review the clinical features of ten cases of PAO from a single UK centre. Patients had attended the Royal National Hospital for Rheumatic Diseases, Bath (RNHRD) between January 2000 and June 2016. The principal criterion for inclusion was the occurrence of low trauma fractures either during pregnancy or the immediate post-partum period. Data were obtained from retrospective review of medical notes. Bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (Hologic ®Discovery system) at the lumbar spine and hip. Data pertaining to the pregnancy, as well as type and duration of treatment received, were reviewed. All ten cases presented with vertebral fractures. In four patients, no risk factors for fracture other than pregnancy or breastfeeding could be identified. Four patients were found to have vitamin D insufficiency at the time of diagnosis, and a further two patients had received treatment with low molecular weight heparin (LMWH). In one case, further investigation led to a diagnosis of osteogenesis imperfecta (OI) confirmed on genetic testing. In terms of treatment, eight out of the ten patients in this series received a bisphosphonate, most commonly risedronate due to its relatively short skeletal retention time. Clinicians should be aware of PAO, a rare but recognised complication of pregnancy. The condition should be especially considered in women presenting with new onset back pain in pregnancy or the postpartum period.

Parenteral anticoagulants in heart disease: Current status and perspectives (Section II)

Anticoagulants are a mainstay of cardiovascular therapy, and parenteral anticoagulants have widespread use in cardiology, especially in acute situations. Parenteral anticoagulants include unfractionated heparin, low-molecular-weight heparins, the synthetic pentasaccharides fondaparinux, idraparinux and idrabiotaparinux, and parenteral direct thrombin inhibitors. The several shortcomings of unfractionated heparin and of low-molecular-weight heparins have prompted the development of the other newer agents. Here we review the mechanisms of action, pharmacological properties and side effects of parenteral anticoagulants used in the management of coronary heart disease treated with or without percutaneous coronary interventions, cardioversion for atrial fibrillation, and prosthetic heart valves and valve repair. Using an evidence-based approach, we describe the results of completed clinical trials, highlight ongoing research with currently available agents, and recommend therapeutic options for specific heart diseases.

Culture Medium Supplements Derived from Human Platelet and Plasma: Cell Commitment and Proliferation Support

Present cell culture medium supplements, in most cases based on animal sera, are not fully satisfactory especially for the in vitro expansion of cells intended for human cell therapy. This paper refers to (i) an heparin-free human platelet lysate (PL) devoid of serum or plasma components (v-PL) and (ii) an heparin-free human serum derived from plasma devoid of PL components (Pl-s) and to their use as single components or in combination in primary or cell line cultures. Human mesenchymal stem cells (MSC) primary cultures were obtained from adipose tissue, bone marrow, and umbilical cord. Human chondrocytes were obtained from articular cartilage biopsies. In general, MSC expanded in the presence of Pl-s alone showed a low or no proliferation in comparison to cells grown with the combination of Pl-s and v-PL. Confluent, growth-arrested cells, either human MSC or human articular chondrocytes, treated with v-PL resumed proliferation, whereas control cultures, not supplemented with v-PL, remained quiescent and did not proliferate. Interestingly, signal transduction pathways distinctive of proliferation were activated also in cells treated with v-PL in the absence of serum, when cell proliferation did not occur, indicating that v-PL could induce the cell re-entry in the cell cycle (cell commitment), but the presence of serum proteins was an absolute requirement for cell proliferation to happen. Indeed, Pl-s alone supported cell growth in constitutively activated cell lines (U-937, HeLa, HaCaT, and V-79) regardless of the co-presence of v-PL. Plasma- and plasma-derived serum were equally able to sustain cell proliferation although, for cells cultured in adhesion, the Pl-s was more efficient than the plasma from which it was derived. In conclusion, the cells expanded in the presence of the new additives maintained their differentiation potential and did not show alterations in their karyotype.

Evaluation of costs and outcomes associated with pharmacological thromboprophylaxis (unfractionated heparin and low molecular weight heparins) of venous thromboembolism at orthopedic ward in Clinical Hospital Stip

Clinical trials have shown Low-molecular weight heparins (LMWHs) to be at least as safe and efficacious as unfractionated heparin (UFH) for preventing venous thromboembolism (VTE) in patients undergoing major orthopedic surgery who are at highest risk of developing VTE. The retrospective study was conducted at orthopedic department in Clinical Hospital – Stip for period of 12 months (January-December 2013), where LMWHs and UFH are accepted thromboprophylaxis options. 320 patients (144 males and 157 females, medium age 58 years and 70 years, respectively) were hospitalized for various types of major orthopedic surgical interventions. 212 (66%) patients were admitted because of hip or knee fractures, 26 (8%) had conditions after hip or knee fractures and 82 (26%) were hospitalized for removal or implanting of osteosynthetic devices. After the surgical intervention, patients were subjected to anticoagulant prophylaxis (UFH or LMWHs). Which type of prophylaxis will be used depended exclusively on the surgeon’s decision. VTE complications resulting death were observed in 8 (2.5%) out of 13 patients. Death because of PE occurred in 2 (25%) out of 8 patients, compared to 6 (75%) patients who had fatal DVT complications. The average hospital cost for patients treated with LMWHs prophylaxis as first line thromboprophylaxis option was 52831.92 MKD/patient compared to 70082.24 MKD/patient for UFH first line thromboprophylaxis option. We observed that LMWHs thromboprophylaxis, applied in recommended doses subcutaneously once a day, is potentially more effective and cost saving option compared to UFH and should be considered as pharmacological treatment of first choice for the prevention of VTE (DVT and PE) in patients recovering from major orthopedic surgery at the orthopedic department in Clinical Hospital Stip. Keywords: Thromboprophylaxis, major orthopedic surgery, LMWHs, UFH

Guidance for the treatment of deep vein thrombosis and pulmonary embolism

This guidance document focuses on the diagnosis and treatment of venous thromboembolism (VTE). Efficient, cost effective diagnosis of VTE is facilitated by combining medical history and physical examination with pre-test probability models, D dimer testing and selective use of confirmatory imaging. Clinical prediction rules, biomarkers and imaging can be used to tailor therapy to disease severity. Anticoagulation options for acute VTE include unfractionated heparin, low molecular weight heparin, fondaparinux and the direct oral anticoagulants (DOACs). DOACs are as effective as conventional therapy with LMWH and vitamin K antagonists. Thrombolytic therapy is reserved for massive pulmonary embolism (PE) or extensive deep vein thrombosis (DVT). Inferior vena cava filters are reserved for patients with acute VTE and contraindications to anticoagulation. Retrievable filters are strongly preferred. The possibility of thoracic outlet syndrome and May-Thurner syndrome should be considered in patients with subclavian/axillary and left common iliac vein DVT, respectively in absence of identifiable triggers. The optimal duration of therapy is dictated by the presence of modifiable thrombotic risk factors. Long term anticoagulation should be considered in patients with unprovoked VTE as well as persistent prothrombotic risk factors such as cancer. Short-term therapy is sufficient for most patients with VTE associated with transient situational triggers such as major surgery. Biomarkers such as D dimer and risk assessment models such the Vienna risk prediction model offer the potential to customize VTE therapy for the individual patient. Insufficient data exist to support the integration of bleeding risk models into duration of therapy planning.

Anticoagulation via anti-Factor Xa inhibition

Hospital-acquired deep vein thrombosis (DVT) affects 10-25% of medical patients and up to 60% of surgical patients. While thromboprophylaxis is without a doubt under utilized in the hospital setting, there is also a need for more efficacious agents. Fondaparinux, the first of a new class of agents Factor Xa inhibitiors, has recently come into clinical use. It is a synthetic pentasaccharide and indirect Factor Xa inhibitor with a predictable antithrombotic action. Being a synthetic product, there are no concerns about supply, nor viral or prion protein contamination. Initial large international trials in orthopaedic patients demonstrated its superior efficacy to standard thromboprophylaxis. Further trials confirmed its superior efficacy in venous thromboembolism (VTE) prevention, both in medical and surgical patient groups, as well as treatment of pulmonary embolism and DVT. Its use has also recently been evaluated in acute coronary syndromes and angioplasty. Fondaparinux currently has licenses in the UK for thromboprophylaxis and treatment of VTE and a license for the management of acute coronary syndrome is likely to be forthcoming. It has a favourable side effect profile and if the price is acceptable, is likely to take over from low molecular weight heparins in these indications as the drug of choice on the grounds of efficacy and safety.

Does Anticoagulant Medication Alter Fracture-Healing? A Morphological and Biomechanical Evaluation of the Possible Effects of Rivaroxaban and Enoxaparin Using a Rat Closed Fracture Model

Low molecular weight heparin (LMWH) is routinely used to prevent thromboembolism in orthopaedic surgery, especially in the treatment of fractures or after joint-replacement. Impairment of fracture-healing due to increased bone-desorption, delayed remodelling and lower calcification caused by direct osteoclast stimulation is a well-known side effect of unfractioned heparin. However, the effect of LMWH is unclear and controversial. Recent studies strongly suggest impairment of bone-healing in-vitro and in animal models, characterized by a significant decrease in volume and quality of new-formed callus. Since October 2008, Rivaroxaban (Xarelto) is available for prophylactic use in elective knee- and hip-arthroplasty. Recently, some evidence has been found indicating an in vitro dose independent reduction of osteoblast function after Rivaroxaban treatment. In this study, the possible influence of Rivaroxaban and Enoxaparin on bone-healing in vivo was studied using a standardized, closed rodent fracture-model. 70 male Wistar-rats were randomized to Rivaroxaban, Enoxaparin or control groups. After pinning the right femur, a closed, transverse fracture was produced. 21 days later, the animals were sacrificed and both femora harvested. Analysis was done by biomechanical testing (three-point bending) and micro CT. Both investigated substances showed histomorphometric alterations of the newly formed callus assessed by micro CT analysis. In detail the bone (callus) volume was enhanced (sign. for Rivaroxaban) and the density reduced. The bone mineral content was enhanced accordingly (sign. for Rivaroxaban). Trabecular thickness was reduced (sign. for Rivaroxaban). Furthermore, both drugs showed significant enlarged bone (callus) surface and degree of anisotropy. In contrast, the biomechanical properties of the treated bones were equal to controls. To summarize, the morphological alterations of the fracture-callus did not result in functionally relevant deficits.

Managing Extended Oral Anticoagulation After Unprovoked Venous Thromboembolism

Venous thromboembolism (VTE), which includes deep venous thrombosis and pulmonary embolism, is a major public health problem associated with increased morbidity and mortality. Despite the high recurrence risk associated with unprovoked VTE, extended anticoagulation remains controversial. Oral antithrombotic agents for extended VTE treatment comprise the vitamin K antagonists, aspirin, and the direct oral anticoagulants (also known as target-specific oral anticoagulants and formerly known as the new or novel oral anticoagulants) including rivaroxaban, dabigatran, apixaban, and edoxaban. The efficacy of these anticoagulants in reducing the risk of VTE recurrence (>80%-90% relative risk reduction) is offset by the risk of major bleeding that approaches 3% per year. Stratifying risks of recurrence and bleeding to identify patients at low, intermediate, or high risk and carefully considering the pharmacologic profile of the antithrombotic agents will help clinicians in choosing the optimal anticoagulant and duration and/or surveillance strategy. This review will discuss the current guidelines for extended VTE treatment, review the clinical trials involving the direct oral anticoagulants, and present the clinical considerations and concerns involving extended therapy.

The Effect of Low Molecular Weight Heparins on Fracture Healing

Venous Thromboembolism is a serious complication in the trauma patient. The most commonly studied and used anticoagulant treatment in prophylaxis of thrombosis is heparin. The prolonged use of unfractionated heparin has been connected with increased incidence of osteoporotic fractures. Low molecular-weight-heparins (LMWHs) have been the golden rule in antithrombotic therapy during the previous two decades as a way to overcome the major drawbacks of unfractioned heparin. However there are few studies reporting the effects of LMWHs on bone repair after fractures. This review presents the studies about the effects of LMWHs on bone biology (bone cells and bone metabolism) and underlying the mechanisms by which LMWHs may impair fracture healing process. The authors' research based on literature concluded that there are no facts and statistics for the role of LMWHs on fracture healing process in humans and the main body of evidence of their role comes from in vitro and animal studies. Further large clinical studies designed to compare different types of LMWHs, in different dosages and in different patient or animal models are needed for exploring the effects of LMWHs on fracture healing process.

Postpartum osteoporosis and vertebral fractures in two patients treated with enoxaparin during pregnancy

Postpartum osteoporosis (PPO) is a rare disease associated with pregnancy and lactation period. Here, we report severe PPO and multiple vertebral compression fractures in two patients treated with enoxaparin--low-molecular-weight heparin (LMWH)--throughout their pregnancy. A 34-year-old woman who has delivered her second baby 3 months ago presented with severe low-back pain. She was treated with enoxaparin 40 mg/day for 8 months during her pregnancy. Dual-energy X-ray absorptiometry (DEXA) showed low T- and Z-scores in lumbar (L) vertebras. In magnetic resonance imaging (MRI), severe height losses in thoracic (T) 12, L1, and L2 vertebras were detected. She was diagnosed to have severe PPO and multiple vertebral compression fractures and was prescribed risedronate 35 mg/week, calcium, and vitamin D. The other patient was a 36-year-old woman diagnosed with PPO and vertebral fractures at the third week postpartum. She was also treated with enoxaparin 60 mg/day during her pregnancy. Severe osteoporosis in L vertebras and height losses indicative for compression fractures in T5-8, T11-12, and L2-5 vertebras were detected by DEXA and MRI, respectively. She was treated with calcitonin 200 U/day, calcium, and vitamin D. These findings suggest that vertebral compression fractures and PPO may be one of the causes of severe back pain in postpartum patients. Treatment with LMWH during pregnancy might be considered as a new risk factor for this rare condition.

Medication-induced osteoporosis: screening and treatment strategies

Drug-induced osteoporosis is a significant health problem and many physicians are unaware that many commonly prescribed medications contribute to significant bone loss and fractures. In addition to glucocorticoids, proton pump inhibitors, selective serotonin receptor inhibitors, thiazolidinediones, anticonvulsants, medroxyprogesterone acetate, aromatase inhibitors, androgen deprivation therapy, heparin, calcineurin inhibitors, and some chemotherapies have deleterious effects on bone health. Furthermore, many patients are treated with combinations of these medications, possibly compounding the harmful effects of these drugs. Increasing physician awareness of these side effects will allow for monitoring of bone health and therapeutic interventions to prevent or treat drug-induced osteoporosis.

Heparin concentration is critical for cell culture with human platelet lysate

BACKGROUND AIMS

Culture media for mesenchymal stromal cells (MSCs) are generally supplemented with fetal bovine serum. Human platelet lysate (hPL) has been proven to be a very effective alternative without the risk of xenogeneic infections or immune reactions. In contrast to fetal bovine serum, hPL comprises plasma, and anticoagulants-usually unfractionated heparin (UFH)-need to be added to prevent gel formation.

METHODS

Cultures of MSCs in hPL media with various concentrations of UFH and enoxaparin, a low-molecular-weight heparin (LMWH), were systematically compared with regard to proliferation, fibroblastoid colony-forming unit frequency, immunophenotype and in vitro differentiation.

RESULTS

At least 0.61 IU/mL UFH or 0.024 mg/mL LMWH was necessary for reliable prevention of coagulation of hPL pools used in this study. Higher concentrations impaired cellular proliferation in a dose-dependent manner even without benzyl alcohol, which is commonly added to heparins as a bacteriostatic agent. Colony-forming unit frequency was also reduced at higher heparin concentrations, particularly with LMWH, whereas no significant effect was observed on cellular morphology or immunophenotype. High concentrations of heparins reduced the in vitro differentiation toward adipogenic and osteogenic lineages.

CONCLUSIONS

Heparin concentration is critical for culture of MSCs in hPL media; this is of particular relevance for cellular therapy where cell culture procedures need to be optimized and standardized.

The mechanisms of nadroparin-mediated inhibition of proliferation of two human lung cancer cell lines

OBJECTIVES

Clinical data suggest that heparin treatment improves survival of lung cancer patients, but the mechanisms involved are not fully understood. We investigated whether low molecular weight heparin nadroparin, directly affects lung cancer cell population growth in conventionally cultured cell lines.

MATERIALS AND METHODS

A549 and CALU1 cells' viability was assessed by MTT and trypan blue exclusion assays. Cell proliferation was assessed using 5-bromo-2-deoxyuridine incorporation. Apoptosis and cell-cycle distribution were analysed by flow cytometry; cyclin B1, Cdk1, p-Cdk1 Cdc25C, p-Cdc25C and p21 expressions were analysed by western blotting. mRNA levels were analysed by real time RT-PCR.

RESULTS

Nadroparin inhibited cell proliferation by 30% in both cell lines; it affected the cell cycle in A549, but not in CALU-1 cells, inducing arrest in the G(2) /M phase. Nadroparin in A549 culture inhibited cyclin B1, Cdk1, Cdc25C and p-Cdc25C, while levels of p-Cdk1 were elevated; p21 expression was not altered. Dalteparin caused a similar reduction in A549 cell population growth; however, it did not alter cyclin B1 expression as expected, based on previous reports. Fondaparinux caused minimal inhibition of A549 cell population growth and no effect on either cell cycle or cyclin B1 expression.

CONCLUSIONS

Nadroparin inhibited proliferation of A549 cells by inducing G(2) /M phase cell-cycle arrest that was dependent on the Cdc25C pathway, whereas CALU-1 cell proliferation was halted by as yet not elucidated modes.

Heparin-induced skin lesions

Heparins are widely used for prophylaxis and treatment of thromboembolic diseases. Besides bleeding complications, heparin-induced skin lesions are the most frequent unwanted adverse effects of subcutaneous heparin treatment. Evidence suggests that these lesions are more common than previously thought. Lesions are most frequently due to either allergic reactions or to possibly life-threatening heparin-induced thrombocytopenia. Early recognition and adequate treatment are highly important, because although both complications initially show a similar clinical picture, their treatment should be fundamentally different. Furthermore, risk factors associated with the patient, drug, and treatment regimen have been identified. We review the clinical range of heparin-induced skin lesions, emphasise evidence and controversies in epidemiology, diagnosis, and differential diagnosis, and discuss the management of patients with these skin lesions.

Pulmonary embolism in children

Unlike in adults, pulmonary embolism (PE) is an infrequent event in children. It has a marked bimodal distribution during the paediatric years, occurring predominantly in neonates and adolescents. The most important predisposing factors to PE in children are the presence of a central venous line (CVL), infection, and congenital heart disease. Clinical signs of PE are non-specific in children or can be masked by underlying conditions. Diagnostic testing is necessary in children, especially with the lack of clinical prediction rules. Recommendations for tests are derived from adult studies with ventilation/perfusion (V/Q) scintigraphy being well established. There exists an increasing role for computerised tomography pulmonary angiography (CTPA) and magnetic resonance pulmonary angiography (MRPA). Thrombotic events in children are initially treated with unfractionated heparin (UFH) or low molecular weight heparin (LMWH). For the extended anticoagulant therapy LMWH or vitamin K antagonists can be used with duration of treatment recommendations extrapolated from adult data. Mortality rates for PE in children are reported to be around 10%, with death usually related to the underlying disease processes. Exact data about recurrence risk in children is unknown. Because of the difference in aetiology, presentation, diagnostic methods and treatment between adults and children further research is necessary to assess the validity of recommendations for children.

Current and future management of pediatric venous thromboembolism

Venous thromboembolism (VTE) is an increasingly common complication encountered in tertiary care pediatric settings. The purpose of this review is to summarize the epidemiology, current and emerging pharmacotherapeutic options, and management of this disease. Over 70% of VTE occur in children with chronic diseases. Although they are seen in children of all ages, adolescents are at greatest risk. Pediatric VTE is associated with an increased risk of in-hospital mortality; recurrent VTE and post-thrombotic syndrome are commonly seen in survivors. In recent years, anticoagulation with low molecular weight heparin has emerged as the mainstay of therapy, but compliance is limited by its onerous subcutaneous administration route. New anticoagulants either already approved for use in adults or in the pipeline offer the possibility of improved dose stability and oral routes of administration. Current recommended anticoagulation course durations are derived from very limited case series and cohort data, or extrapolations from adult literature. However, the pathophysiologic underpinnings of pediatric VTE are dissimilar from those seen in adults and are often variable within groups of pediatric patients. Clinical studies and trials in pediatric VTE are underway which will hopefully improve the quality of evidence from which therapeutic guidelines are derived.

Heparin-like polysaccharides reduce osteolytic bone destruction and tumor growth in a mouse model of breast cancer bone metastasis

TGF-β regulates several steps in cancer metastasis, including the establishment of bone metastatic lesions. TGF-β is released from bone during osteoclastic bone resorption and it stimulates breast cancer cells to produce osteolytic factors such as interleukin 11 (IL-11). We conducted a cell-based siRNA screen and identified heparan sulfate 6-O-sulfotransferase 2 (HS6ST2) as a critical gene for TGF-β-induced IL-11 production in highly bone metastatic MDA-MB-231(SA) breast cancer cells. HS6ST2 attaches sulfate groups to glucosamine residues in heparan sulfate glycosaminoglycans. We subsequently showed how heparin and a high-molecular-weight Escherichia coli K5-derived heparin-like polysaccharide (K5-NSOS) inhibited TGF-β-induced IL-11 production in MDA-MB-231(SA) cells. In addition, K5-NSOS inhibited bone resorption activity of human osteoclasts in vitro. We evaluated the therapeutic potential of K5-NSOS and fragmin in a mouse model of breast cancer bone metastasis. MDA-MB-231(SA) cells were inoculated into the left cardiac ventricle of athymic nude mice which were treated with fragmin, K5-NSOS, or vehicle once a day for four weeks. Both heparin-like glycosaminoglycans inhibited weight reduction, decreased osteolytic lesion area, and reduced tumor burden in bone. In conclusion, our data imply novel mechanisms involved in TGF-β induction and support the critical role of heparan sulfate glycosaminoglycans in cancer metastasis as well as indicate that K5-NSOS is a potential antimetastatic and antiresorptive agent for cancer therapy. This study illustrates the potential to translate in vitro siRNA screening results toward in vivo therapeutic concepts.

Parenteral anticoagulants: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

This article describes the pharmacology of approved parenteral anticoagulants. These include the indirect anticoagulants, unfractionated heparin (UFH), low-molecular-weight heparins (LMWHs), fondaparinux, and danaparoid, as well as the direct thrombin inhibitors hirudin, bivalirudin, and argatroban. UFH is a heterogeneous mixture of glycosaminoglycans that bind to antithrombin via a unique pentasaccharide sequence and catalyze the inactivation of thrombin, factor Xa, and other clotting enzymes. Heparin also binds to cells and plasma proteins other than antithrombin causing unpredictable pharmacokinetic and pharmacodynamic properties and triggering nonhemorrhagic side effects, such as heparin-induced thrombocytopenia (HIT) and osteoporosis. LMWHs have greater inhibitory activity against factor Xa than thrombin and exhibit less binding to cells and plasma proteins than heparin. Consequently, LMWH preparations have more predictable pharmacokinetic and pharmacodynamic properties, have a longer half-life than heparin, and are associated with a lower risk of nonhemorrhagic side effects. LMWHs can be administered once daily or bid by subcutaneous injection, without coagulation monitoring. Based on their greater convenience, LMWHs have replaced UFH for many clinical indications. Fondaparinux, a synthetic pentasaccharide, catalyzes the inhibition of factor Xa, but not thrombin, in an antithrombin-dependent fashion. Fondaparinux binds only to antithrombin. Therefore, fondaparinux-associated HIT or osteoporosis is unlikely to occur. Fondaparinux exhibits complete bioavailability when administered subcutaneously, has a longer half-life than LMWHs, and is given once daily by subcutaneous injection in fixed doses, without coagulation monitoring. Three additional parenteral direct thrombin inhibitors and danaparoid are approved as alternatives to heparin in patients with HIT.

Adverse effects of heparin

All the adverse effects of heparins are related to their wide variety of biological activities, with bleeding being the most important safety issue, resulting directly from the potency of heparin as an anticoagulant. However, it is hard to define the bleeding risk, since it depends on numerous parameters including the indication, dosage, method, and duration of heparin application, the clinical study design and definition of bleeding as well as patient characteristics and determinants of bleeding such as type of surgery and co-medication. Nonbleeding complications of heparins are caused by binding of heparin molecules to proteins other than antithrombin and to cells, which is generally more pronounced with unfractionated heparin than with low-molecular-weight heparins. Accordingly, heparin-induced thrombocytopenia, the most severe nonbleeding adverse reaction, occurs about 10 times less with low-molecular-weight heparins than with unfractionated heparin. Frequent and therefore important adverse reactions of heparins are skin lesions resulting from delayed-type hypersensitivity reactions. All the other undesirable effects are discussed as well, but they are mostly clinically irrelevant.

The influence of low molecular weight heparin on the expression of osteogenic growth factors in human fracture healing

PURPOSE

Anticoagulant therapy with low molecular weight heparins (LMWH) and mechanical compression is considered the gold standard for the prevention of thrombosis. However, evidence exists that LMWHs impair bone metabolism. The aim of this study was therefore to analyse alterations in the expression of M-CSF, VEGF and TGF-ß1 after treatment with enoxaparin in patients with long bone fracture to investigate the effect of LMWH on human fracture healing.

METHODS

A total of 81 patients with long bone fractures were included in the study and divided into two groups. One group comprised patients who received enoxaparin and the other group, patients who did not receive enoxaparin postoperatively. Growth factor levels were analysed in patients' serum and different groups were retrospectively compared.

RESULTS

M-CSF serum concentrations were found to be significantly higher only at 48 weeks after surgery in enoxaparin. Mean overall VEGF serum concentration was higher in patients with enoxaparin. TGF-β1 serum concentrations were higher at 48 weeks after surgery in patients with enoxaparin.

CONCLUSION

This is the first comparative systemic measurement of M-CSF, VEGF and TGF-ß1 serum levels in patients with and without enoxaparin after long bone fracture. Significant differences of the expression of the growth factors after enoxaparin therapy were only observed at week 48 after surgery for M-CSF and TGF-ß1.

The effect of a new direct Factor Xa inhibitor on human osteoblasts: an in-vitro study comparing the effect of rivaroxaban with enoxaparin

BACKGROUND

Current treatments for the prevention of thromboembolism include heparin and low-molecular weight heparins (LMWHs). A number of studies have suggested that long term administration of these drugs may adversely affect osteoblasts and therefore, bone metabolism. Xarelto™ (Rivaroxaban) is a new anti-thrombotic drug for the prevention of venous thromboembolism in adult patients undergoing elective hip and knee replacement surgery. The aim of this in vitro study was to investigate the possible effects of rivaroxaban on osteoblast viability, function and gene expression compared to enoxaparin, a commonly used LMWH.

METHODS

Primary human osteoblast cultures were treated with varying concentrations of rivaroxaban (0.013, 0.13, 1.3 and 13 μg/ml) or enoxaparin (1, 10 and 100 μg/ml). The effect of each drug on osteoblast function was evaluated by measuring alkaline phosphatase activity. The MTS assay was used to assess the effect of drug treatments on cell proliferation. Changes in osteocalcin, Runx2 and BMP-2 messenger RNA (mRNA) expression following drug treatments were measured by real-time polymerase chain reaction (PCR).

RESULTS

Rivaroxaban and enoxaparin treatment did not adversely affect osteoblast viability. However, both drugs caused a significant reduction in osteoblast function, as measured by alkaline phosphatase activity. This reduction in osteoblast function was associated with a reduction in the mRNA expression of the bone marker, osteocalcin, the transcription factor, Runx2, and the osteogenic factor, BMP-2.

CONCLUSIONS

These data show that rivaroxaban treatment may negatively affect bone through a reduction in osteoblast function.

Effects of antithrombotic drugs fondaparinux and tinzaparin on in vitro proliferation and osteogenic and chondrogenic differentiation of bone-derived mesenchymal stem cells

An unexpected side effect of some classes of anticoagulants has been osteoporosis which may be, at least in part, related to deranged mesenchymal stem cell (MSC) function. The aim of the present study was to compare the effect of fondaparinux (FDP), a novel antithrombotic with a traditional widely used low molecular weight heparin, tinzaparin (TZP) on MSC proliferation and differentiation. MSCs were isolated from trabecular bone of 14 trauma patients by a collagenase-based digestion procedure and expanded in standard conditions until passage 3. Proliferation and differentiation of MSCs to chondrocytes and osteoblasts was assessed with or without the addition of FDP and TZP using standard in vitro assays and a broad range of drug concentrations. Flow cytometry was used for MSC phenotyping. In the age studied group (17-74 years old) the MSC frequency in collagenase-released fractions was 641/10(6) cells (range 110-2,158) and their growth characteristics were ∼4 days/population doubling. Cultures had a standard MSC phenotype (CD73+, CD105+, CD146+, CD106+, and CD166+). Cell proliferation was assessed by both colony-forming unit-fibroblast (CFU-F) and colorimetric tetrazolium salt XTT assays. In both assays, MSC proliferation was inhibited by the addition of TZP, particularly at high concentrations. In contrast, FDP had no effect on MSC proliferation. Osteogenic differentiation and chondrogenic differentiation were not affected by the addition of either TZP or FDP. Whilst MSC proliferation, but not differentiation, is negatively affected by TZP, there was no evidence for adverse effects of FDP in this in vitro model system which argues well for its use in the orthopedic setting.

Application, tolerance and safety of fondaparinux therapy in a German hospital: a prospective single-centre experience

INTRODUCTION

The pentasaccharide fondaparinux is widely approved for prophylaxis and treatment of thromboembolic diseases and therapy of acute coronary syndrome. It is also used off-label in patients with acute, suspected or antecedent heparin-induced thrombocytopenia (HIT). The aim of this prospective observational cohort study was to document fondaparinux' prescription practice, tolerance and therapy safety in a representative mixed German single-centre patient cohort.

PATIENTS AND METHODS

Between 09/2008 - 04/2009, 231 consecutive patients treated with fondaparinux were enrolled. Medical data were obtained from patient's records. The patients were clinically screened for thrombosis (Wells score), sequelae of HIT (4T's score), and bleeding complications (ISTH-criteria) and subjected to further assessment (i.e. sonography, HIT-diagnostics), if necessary. The mortality rate was assessed 30 days after therapy start.

RESULTS

Overall, 153/231 patients had a prophylactic, 74/231 patients a therapeutic, and 4/231 patients a successive prophylactic/therapeutic indication. In 11/231 patients fondaparinux was used due to suspected/antecedent HIT, in 5/231 patients due to a previous cutaneous delayed-type hypersensitivity to heparins. Other indications were rare. Three new/progressive thromboses were detected. No cases of HIT, major bleedings, or fatalities occurred.

CONCLUSIONS

Fondaparinux was well tolerated and was safe in prophylaxis and therapy; prescriptions mostly followed the current approval guidelines and were rarely related to HIT-associated indications (<5% of prescriptions), which is in contrast to previous study results in the U.S. (>94% of prescriptions were HIT-associated). A trend towards an individualised fondaparinux use based on the compound's inherent properties and the patients' risk profiles, i.e., antecedent HIT, bone fractures, heparin allergy, was observed.

Clinical pharmacology of direct and indirect factor Xa inhibitors

The limitations of conventional anticoagulants have stimulated the development of new anticoagulants. The central position of factor Xa (FXa) at the junction of the intrinsic and extrinsic pathways in the coagulation cascade means that direct and indirect FXa inhibitors have increasingly changed antithrombotic strategies. FXa inhibitors potently and selectively inhibit thrombin formation rather than thrombin activity. Direct FXa inhibitors may directly bind to FXa, whereas indirect inhibitors are dependent on antithrombin. Direct inhibitors may bind free FXa and, in contrast to indirect inhibitors, FXa within the prothrombinase complex or within clots as well. Fondaparinux is the prototype indirect FXa inhibitor and has been extensively studied in the prevention and treatment of thromboembolic diseases, including acute coronary syndromes. Due to a favourable efficacy and safety profile and convenient once-daily dosing without the need for monitoring, fondaparinux is preferentially recommended in recent guidelines dealing with antithrombotic treatment. A number of small-molecule direct FXa inhibitors are currently at different stages of clinical development. After an extensive clinical trial programme demonstrating superior efficacy without a significant increase in major bleeds compared with enoxaparin, rivaroxaban is now available for the prevention of thromboembolic events in patients undergoing orthopaedic surgery. Rivaroxaban also offers the convenience of oral once-daily dosing without the need for monitoring. Whereas most direct FXa inhibitors are orally active, otamixaban is administered intravenously, offering rapid on-off anticoagulant activity. Other compounds under development may offer additional options for tailored antithrombotic strategies according to differing indications, clinical situations and patient variables.

Low allergenic potential with fondaparinux: results of a prospective investigation

OBJECTIVE

To determine the incidence and causes of skin reactions to the synthetic pentasaccharide fondaparinux.

PATIENTS AND METHODS

Patients who received prophylactic/therapeutic subcutaneous fondaparinux treatment for more than 7 days were prospectively examined for cutaneous adverse effects between September 1, 2008, and April 30, 2009. When indicated, other procedures, such as skin biopsy, allergy testing, and clinical/laboratory assessment for thrombosis and heparin-induced thrombocytopenia, were performed.

RESULTS

Overall, 231 patients were enrolled. No patient developed typical delayed type IV hypersensitivity (DTH) erythematous skin lesions. However, one female patient experienced abdominal pruritus at sites of injection. Histology revealed a mild lymphohistiocytic infiltrate, confirming a DTH reaction. Heparin-induced thrombocytopenia, as another possible underlying pathomechanism for cutaneous lesions, was ruled out clinically and serologically. Hence, the overall incidence of fondaparinux-induced allergic skin lesions was 0.4% (95% confidence interval, 0.01%-2.4%). No cross-allergies were observed in patients with DTH reaction to heparins.

CONCLUSION

Fondaparinux has a low allergenic potential. The incidence of allergic cutaneous DTH reactions is almost 20 times lower compared to that with commonly used heparins. These results, together with the known low prevalence of secondary thrombotic events or heparin-induced thrombocytopenia during fondaparinux therapy, suggest that in selected patients fondaparinux might substantially improve patient care, therapeutic safety, and cost-effectiveness of anticoagulant therapy.

TRIAL REGISTRATION

clinicaltrials.gov identifier: NCT00510432.

Influence of long-term thromboprophylaxis with low-molecular-weight heparin (enoxaparin) on changes of bone metabolism markers in pregnant women

This is a first descriptive, retrospective, observational study aiming to evaluate the changes in bone turnover markers in pregnant women and to assess the effect of a long-term treatment with low-molecular-weight heparin (LMWH), specifically, enoxaparin. Study involved 50 pregnant Caucasian women with thrombophilia. The patients either received prophylactic enoxaparin once daily subcutaneously (N = 35) or were observed without treatment (N = 15). Concentrations of total serum alkaline phosphatase (total AP), bone alkaline phosphatase (bone AP), osteoprotegerin (OPG), and the receptor activator of nuclear factor κB ligand (RANKL) were measured at 15, 25, and 35 weeks of gestation. Total serum AP increased with gestational age. In the group treated with enoxaparin, the percentage of bone AP concentration was lower (P < .05) than in the control group. Serum OPG also increased with gestational age, but no significant difference was found between the groups with- and without treatment. Despite the OPG increased, RANKL did not change.

Review: Low-molecular-weight heparin-induced osteoporosis and osteoporotic fractures: a myth or an existing entity?

Long-term use of unfractioned heparin data has been associated with a 2.2-5% incidence of heparin-induced osteoporotic fracture, but for low-molecular-weight heparin (LMWH) data is scarce and there is lack of clarity of the risks of osteoporosis and osteoporotic fractures. In this paper we review the differential diagnosis of osteoporosis and osteoporotic fractures, and we conduct a systematic review of all related cases from case reports and trials. Two new cases of possible LMWH-induced osteoporosis are also presented and the difficulties in making the diagnosis are highlighted. The authors conclude that, until large clinical trials are designed to investigate pre- and post-treatment bone density and to compare different dosages of LMWH effect on the bone density in different patient groups, no safe conclusions can be made.

The current role of anticoagulants in cardiovascular medicine

Thrombotic events in cardiovascular disease are a huge burden to healthcare budgets. Anticoagulant use is recommended for thrombotic event prevention in many cardiovascular diseases, including stroke prevention in atrial fibrillation, treatment and secondary prevention of acute coronary syndrome. Current parenteral anticoagulants include unfractionated heparin, low-molecular-weight heparins (LMWHs) and fondaparinux. Patients with acute coronary syndrome usually receive unfractionated heparin or a LMWH on hospital admission, both exhibit similar efficacy in reducing mortality and myocardial infarction rates; however, LMWHs may have a better safety profile and do not require routine coagulation monitoring. In acute coronary syndrome, fondaparinux use results in significantly lower mortality compared with LMWHs or unfractionated heparin. However, parenteral drugs are inconvenient for long-term outpatient use. Vitamin K antagonists are currently the only oral anticoagulants available for long-term use, but multiple drawbacks hinder their use. A large unmet need exists for new convenient and well-tolerated oral anticoagulants that do not require routine monitoring.

Glycosaminoglycan composition changes with MG-63 osteosarcoma osteogenesis in vitro and induces human mesenchymal stem cell aggregation

Osteogenic differentiation is coordinated by the exposure of cells to temporal changes in a combination of growth factors and elements within the extracellular matrix (ECM). Many of the key proteins that drive these changes share the property of being dependent on ECM glycosaminoglycans (GAGs) for their activity. Here, we examined whether GAGs isolated from proliferating, differentiating and mineralizing MG-63 osteosarcoma cells differed in their physical properties, and thus in their capacities to coordinate the osteogenic cascade both in human MG-63 osteosarcoma cells and primary human mesenchymal stem cells (hMSCs). Our results show that the size distribution of GAGs, the expression of GAG-carrying proteoglycan cores and the expression of enzymes involved in their modification systematically change as MG-63 cells mature in culture. When dosed back onto cells exogenously in soluble form, GAGs regulated MG-63 survival and growth in a dose-dependent manner, but not differentiation in either cell type. In contrast, hMSCs aggregated into distinct colonies when grown on GAG-coated substrates, while MG-63 cells did not. Heparin-coated substrates improved hMSC viability without inducing aggregation. These results suggest a complex role for GAGs in coordinating the emergence of the osteoblast phenotype, and provide further evidence for the use of heparans in bone tissue repair applications.