Effects of thromboprophylaxis on mesenchymal stromal cells during osteogenic differentiation: an in-vitro study comparing enoxaparin with rivaroxaban

Low molecular weight heparin decreases pro-coagulant activity in clinical MSC products

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) are multipotent adult cells that can be isolated from tissues including bone marrow [MSC(BM)], adipose [MSC(AT)] and umbilical cord [MSC(CT)]. Previous studies have linked expression of tissue factor (TF) on MSC surfaces to a procoagulant effect. Venous thromboembolism (VTE), immediate blood-mediated inflammatory reaction (IBMIR) and microvascular thrombosis remain a risk with intravascular MSC therapy. We examined the effect of low molecular weight heparin (LMWH) on clinical-grade MSCs using calibrated automated thrombography (CAT).

METHODS

Clinical grade MSC(BM)s, MSC(AT)s and MSC(CT)s harvested at passage 4 were added to normal pooled plasma (NPP) to a final concentration of either 400 000 or 50 000 cells/mL. LMWH was added to plasma in increments of 0.1 U/mL. Thrombin generation (TG) was measured using CAT. Flow cytometry was conducted on the cells to measure MSC phenotype and TF load.

RESULTS

Presence of MSCs decreased lag time and increased peak TG. All cell lines demonstrated a dose response to LMWH, with MSC(AT) demonstrating the least thrombogenicity and most sensitivity to LMWH. TG was significantly reduced in all cell lines at doses of 0.2 U/mL LMWH and higher.

DISCUSSION

All MSC types and concentrations had a decrease in peak thrombin and TG with increasing amounts of LMWH. While this in vitro study cannot determine optimal dosing, it suggests that LMWH can be effectively used to lower the risk of VTE associated with intravascular administration of MSCs. Future in vivo work can be done to determine optimal dosing and effect on IBMIR and VTE.

Impaired bone healing by enoxaparin via inhibiting the differentiation of bone marrow mesenchymal stem cells towards osteoblasts

INTRODUCTION

Enoxaparin is widely used to prevent venous thromboembolism after orthopedic surgery and has some adverse effects, such as osteoporosis and delay in fracture healing. However, the exact mechanism delaying bone healing by enoxaparin is still unclear.

MATERIALS AND METHODS

X-ray and Micro-CT scanning were performed to detect the effects of enoxaparin on bone healing at rat model of bone defeat. CCK-8 assay and flow cytometry were conducted to measure the effects of enoxaparin on bone marrow mesenchymal stem cells (BMSCs). The mRNA/protein levels of osteocalcin (OCN), runt-related transcription factor 2 (Runx2) and bone morphogenetic protein 2 (BMP2) were analyzed by real-time PCR and western blotting, respectively. Alizarin red staining was used to observe the mineralized nodules.

RESULTS

Enoxaparin (2000 AXaIU/kg) not only profoundly increased the trabecular separation, but also notably decreased the trabecular bone volume/tissue volume, trabecular thickness, trabecular number and OCN level, in vivo. Additionally, significantly inhibiting proliferation of BMSCs by enoxaparin (1.0 and 10 AXaIU/ml) was detected. The apoptosis and the ratio of G phase cells in enoxaparin (0.1, 1.0 and 10 AXaIU/ml) group were obviously higher than that in control group. While the ratio of S phase cells was downregulated markedly by enoxaparin (0.1,1.0 and 10 AXaIU/ml) compared with the control group. Most importantly, inducing significant decreases of OCN/Runx2 mRNA/protein expression and formation of mineralized nodules by enoxaparin (0.1, 1.0 and 10 AXaIU/ml) were observed compared with the control group. While the notable decreases of BMP2 mRNA/protein level were only detected in enoxaparin (10 AXaIU/ml) group.

CONCLUSION

It was suggested that enoxaparin impaired bone healing through suppressing the differentiation of BMSCs towards osteoblasts.

Rifampicin has - Compared to clindamycin - A dose and time dependent effect on hMSCs during osteogenic differentiation in vitro

Background

The effects of rifampicin and clindamycin on human mesenchymal stromal cell (hMSC) were examined.

Methods

hMSC were cultured with rifampicin and clindamycin (0.5 μg/ml, 5 μg/ml, 50 μg/ml) and examinations of proliferation (Bromodeoxyuridine), calcification (Alizarin red) and mineralization (alkaline phosphatase) were performed after 7th, 14th and 21st days.

Results

With rifampicin (50 μg/ml) cultured hMSC showed a significant negative effect during proliferation, mineralization (7, 14 and 21 days) and calcification (21 days). Clindamycin seems to have no effect.

Conclusions

Rifampicin in a dosage of 50 μg/ml showed a negative impact on proliferation, mineralization and calcification of hMSC after 21 days.

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.

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.

Enoxaparin and rivaroxaban have different effects on human mesenchymal stromal cells in the early stages of bone healing

Objectives

Venous thromboembolism (VTE) is a major potential complication following orthopaedic surgery. Subcutaneously administered enoxaparin has been used as the benchmark to reduce the incidence of VTE. However, concerns have been raised regarding the long-term administration of enoxaparin and its possible negative effects on bone healing and bone density with an increase of the risk of osteoporotic fractures. New oral anticoagulants such as rivaroxaban have recently been introduced, however, there is a lack of information regarding how these drugs affect bone metabolism and post-operative bone healing.

Methods

We measured the migration and proliferation capacity of mesenchymal stem cells (MSCs) under enoxaparin or rivaroxaban treatment for three consecutive weeks, and evaluated effects on MSC mRNA expression of markers for stress and osteogenic differentiation.

Results

We demonstrate that enoxaparin, but not rivaroxaban, increases the migration potential of MSCs and increases their cell count in line with elevated mRNA expression of C-X-C chemokine receptor type 4 (CXCR4), tumor necrosis factor alpha (TNFα), and alpha-B-crystallin (CryaB). However, a decrease in early osteogenic markers (insulin-like growth factors 1 and 2 (IGF1, IGF2), bone morphogenetic protein2 (BMP2)) indicated inhibitory effects on MSC differentiation into osteoblasts caused by enoxaparin, but not by rivaroxaban.

Conclusions

Our findings may explain the adverse effects of enoxaparin treatment on bone healing. Rivaroxaban has no significant impact on MSC metabolism or capacity for osteogenic differentiation in vitro.

Cite this article: Dr H. Pilge. Enoxaparin and rivaroxaban have different effects on human mesenchymal stromal cells in the early stages of bone healing. Bone Joint Res 2016;5:95–100. DOI: 10.1302/2046-3758.53.2000595.