Objectives

Many in vitro studies have investigated the mechanism by which mechanical signals are transduced into biological signals that regulate bone homeostasis via periodontal ligament fibroblasts during orthodontic treatment, but the results have not been systematically reviewed. This review aims to do this, considering the parameters of various in vitro mechanical loading approaches and their effects on osteogenic and osteoclastogenic properties of periodontal ligament fibroblasts.

Aims

The success of anterior cruciate ligament reconstruction (ACLR) depends on osseointegration at the graft-tunnel interface and intra-articular ligamentization. Our aim was to conduct a systematic review of clinical and preclinical studies that evaluated biological augmentation of graft healing in ACLR.

Objective. Human bone marrow stromal cells (HBMSCs) are multipotent and can form bone, cartilage or other tissues under different inductive conditions. The aim of this study was to investigate the effects of enamel matrix derivative (EMD) on the growth and osteogenic differentiation of HBMSCs. Methods. HBMSCs were cultured in monolayer with EMD (1, 10, 50,100, 250μg/ml) in aMEM supplemented with 2% FBS for 3 days. Cells cultured in aMEM supplemented with 2% FBS (basal medium) served as the control group. Double-stranded DNA was quantified by PicoGreen assay. Quantitative RT-PCR was performed to determine the expression levels of RUNX2, osteopontin (OPN) and osteocalcin (OCN), dentin matrix protein1 (DMP1) and dentin sialophosphoprotein (DSPP) at different time points (day 0, 5 and 10) when exposed to 10μg/ml EMD or basal medium. Alkaline phosphatase specific activity (ALPSA) was determined after 5 and 10 days culture. Mineral deposition (as calcium) was visualised using Alizarin Red staining. Results. All EMD groups showed increased dsDNA content after 3 days culture. However, EMD at 50μg/ml appeared optimal giving a 6.8 fold increase over the control group (p<0.01). Relative to day 0, RUNX2 expression was reduced in the presence of 10μg/ml EMD by 50% after 5 days culture (it was reduced by 30% in the control group), After 10 days culture, RUNX2 expression increased 1.5 fold in the presence of 10μg/ml EMD (increased 1.2 fold in the control group) OPN expression patterns were broadly similar to RUNX2. However, after 5 days culture OCN expression increased 4 fold (increased 7 fold in the control group) but by day 10, expression levels in the presence of EMD had fallen back to day 0 levels whereas levels in the control still showed a 6 fold increase compared to day 0. DMP1 and DSPP expression levels remained at very low levels over the full 10 days in culture. After 10 days culture, HBMSCs treated with 10μg/ml EMD showed significant increase of ALPSA compared with the control group. Mineral deposition was observed in both groups, but to a visibly greater extent in EMD treated groups. Conclusions. EMD stimulated HBMCs proliferation and osteogenic differentiation in vitro, suggesting that EMD may be a useful adjunct in inducing HBMSCs down an osteogenic lineage for use in bone tissue engineering applications. Acknowledgments. ORSAS, LDI Bursary, Xiros

We examined whether enamel matrix derivative (EMD) could improve healing of the tendon–bone interface following reconstruction of the anterior cruciate ligament (ACL) using a hamstring tendon in a rat model. ACL reconstruction was performed in both knees of 30 Sprague-Dawley rats using the flexor digitorum tendon. The effect of commercially available EMD (EMDOGAIN), a preparation of matrix proteins from developing porcine teeth, was evaluated. In the left knee joint the space around the tendon–bone interface was filled with 40 µl of EMD mixed with propylene glycol alginate (PGA). In the right knee joint PGA alone was used. The ligament reconstructions were evaluated histologically and biomechanically at four, eight and 12 weeks (n = 5 at each time point). At eight weeks, EMD had induced a significant increase in collagen fibres connecting to bone at the tendon–bone interface (p = 0.047), whereas the control group had few fibres and the tendon–bone interface was composed of cellular and vascular fibrous tissues. At both eight and 12 weeks, the mean load to failure in the treated specimens was higher than in the controls (p = 0.009). EMD improved histological tendon–bone healing at eight weeks and biomechanical healing at both eight and 12 weeks. EMD might therefore have a human application to enhance tendon–bone repair in ACL reconstruction.