The effect of synthetic cannabinoids and their combination with TGF-β3 on wound healing of cell cultured human bone cell monolayers and 3D models. The role of synthetic cannabinoid HU308 and HU308/TGF-β3 combinations on cellular adhesion, proliferation, wound healing, nitric oxide, MMP-2 and ECM protein regulation of MG-63 osteoblast monolayers and 3D models

Abstract

Despite the ongoing political debate regarding the legality of medical marijuana, clinical investigations of the therapeutic use of cannabinoids are now more prevalent than at any time in history. Cannabinoids have been shown to have analgesic, anti-spasmodic, anticonvulsant, anti-tremor, anti-psychotic, anti-inflammatory, anti-oxidant, anti-emetic and appetite-stimulant properties. There are mainly two well-known cannabinoid receptors, CB1 and CB2, located in the central (CB1) and peripheral (CB2) nervous systems as well as the immune system. More recently, endocannabinoids (ligands) and their receptors have also been found in the skeleton which appear as the main body system and physiologically regulated by CB2. This study aimed to examine the effect of both CB1 and CB2 receptor stimulation on wound closure response of MG-63 osteoblast bone cell monolayers using different treatments with cannabinoid such as Winn55,212-2, URB602 and HU308. Also, cell adhesion, cell proliferation and cell length was investigated. The study also aimed to examine the effect of HU308 treatments in combination with TGF-β3 (transforming growth factor beta -3) on wound healing, cell adhesion and extracellular matrix up regulation (collagen type I, fibronectin and protien S-100A6) as well as other biological factors such as secretion of matrix metalloproteinase (MMP-2) and nitric oxide (NO). Finally, this study investigated HU308/TGF-β3 combination treatment on the regulation of extracellular matrix (collagen type I, fibronectin and protien S-100A6) in a 3D multilayer system of MG-63 osteoblast bone cells. Wound healing assays of MG-63 monolayers revealed accelerated wound repair as well as increased cell proliferation mainly regulated through CB2 receptors, and that treatments with HU308 and HU308/TGF-β3 achieved minimum closure timings compared with control groups (P<0.05). Our finding suggested that proliferation rate with 500nM HU308 was significantly higher than control and TGF-β3/HU308 combination groups (P<0.05). Interestingly, percentage of wound remained open after 15 hours for combination groups was 17.6%±1.32 whereas treatment with 500nM HU308 had 20%±2.25 indicating that the combination groups took the lead throughout wound healing. It was also observed that bridge formation in all treatment groups was taking place between 15 to 20 hour periods whereas within control treatments bridge formation started to take place after 25 hours. Cell surface attachment was examined via the trypsinization assay in which the time taken to trypsinize cells from the surface provided a means of assessing the strength of attachment. The results indicated that higher concentrations of HU308 (2μM), induced significant force of cell attachment compared with control and concentrations of 500nM and 1μM (P<0.05). However, groups treated with TGF-β3 and combination HU308/TGF-β3 indicated reduced cell surface attachment compared with control groups, indicating enhanced cell migration. Immunofluorescence staining as well as Elisa based semi-quantification technique indicated that both collagen type I and fibronectin were unregulated using higher concentrations of HU308 with decreased cell proliferation compared to lower concentrations. Nevertheless, protein S-100A6 was up-regulated in treatments with HU308, TGF-β3 and their combination HU308/TGF-β3 (P<0.05), indicating the positive role of these treatments in promoting cell differentiation. MMP-2 levels in the current study were also shown to be concentration-dependent, i.e. higher concentrations of HU308 significantly reduced MMP-2 secretion leading to decreased cell migration, while HU308/TGF-β3 combination treatment increased MMP-2 levels, indicating an increase in cell migration. The current study also examined levels of nitric oxide synthesis in relation to different treatments with HU308, TGF-β3 and HU308/TGF-β3 combination. It was found that nitric oxide up-regulation influences rate of MG-63 osteoblast wound healing in a concentration dependent manner. Lastly, UpCell culture dishes proved to have efficacy in obtaining a multilayer model of MG-63 osteoblast system in-vitro through changes in cell morphology. It was also found that treatments with HU308, TGF-β3 and HU308/TGF-β3 combination influenced collagen type I, fibronecton and protein S-100A6 secretion. These findings supported the earlier Elisa based semi-quantification results obtained for monolayer cultures.