The aim of this study was to investigate the in vitro response of human craniofacial muscle-derived myotubes (primitive/nascent muscle fibres), in three-dimensional constructs, to strain in vitro to mimic clinical scenarios, using expression of the mechanoresponsive gene gelatinase-A/matrix metalloproteinase-2 (MMP-2) as a marker of remodelling of muscle extracellular matrix. Three-dimensional (3D) constructs of cells derived from explants of human masseter muscle (human craniofacial muscle-derived cells; hCMDC) in collagen sponges were subjected to mechanical, uniaxial strain using the Bio-Stretch system. 3D myotube constructs were exposed to the strain regimes of rapid ramp stretch (RRS) or cyclical ramp strain (CRS) with 7.5% and 15% strain. The activity of MMP-2 was assessed by zymography of construct-conditioned medium, whilst lysates of the constructs were used to measure creatine phosphokinase (CPK) activity to confirm the presence of myotubes in the strained constructs. Scanning electron microscopy of the collagen sponges and the CPK assays confirmed the presence of myotubes. MMP-2 was expressed by all the samples and controls, but expression was found to be significantly higher in those cultures strained continuously (RRS), compared to cyclical strain (CRS), and in those strained at 15% compared to 7.5%. Thus, MMP-2 expression, and hence extracellular matrix remodelling, is up-regulated in response to strain and is dependent upon the amount and type of strain to which the muscle is subjected.
As the number of adults that seek orthodontic treatment continues to grow, so too is the popularity of lingual fixed appliances. Although the aesthetic advantages associated with these systems are obvious, for some orthodontists, there has been a reluctance to offer lingual-based treatment to their patients. This is often based upon the perceived problems associated with lingual braces, relating to discomfort and difficulties with speech for the patient, and problems in using these appliances for the orthodontist. Although some of these factors have been investigated, the current evidence base is weak, possibly due to the fact that these are evolving appliance systems. Among the studies that have been carried out to date, pain and discomfort for the patient appears to be similar following the placement of labial or lingual appliances, although the onset can be earlier with lingual brackets and the location different, with the tongue more frequently being involved. Customized lingual brackets may be associated with less pain than pre-fabricated. In addition, patients do seem to be more likely to experience difficulties with speech and mastication when fitted with a lingual appliance. However, there is some evidence that the lingual surfaces of the teeth are more resistant to early demineralization and caries. Little data exist regarding treatment outcome and ease of use for the orthodontist, either between lingual or labial appliances or between different lingual systems. Further research is required to investigate the efficiency of lingual appliance systems, both for the patient and orthodontist.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.