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Crosslinking and the resultant changes in mechanical properties have been shown to influence cellular activity within collagen biomaterials. With this in mind, we sought to determine the effects of crosslinking on both the compressive modulus of collagen-glycosaminoglycan scaffolds and the activity of osteoblasts seeded within them. Dehydrothermal, 1-ethyl-3-3-dimethyl aminopropyl carbodiimide and glutaraldehyde crosslinking treatments were first investigated for their effect on the compressive modulus of the scaffolds. After this, the most promising treatments were used to study the effects of crosslinking on cellular attachment, proliferation, and infiltration. Our experiments have demonstrated that a wide range of scaffold compressive moduli can be attained by varying the parameters of the crosslinking treatments. 1-Ethyl-3-3-dimethyl aminopropyl carbodiimide and glutaraldehyde treatments produced the stiffest scaffolds (fourfold increase when compared to dehydrothermal crosslinking). When cells were seeded onto the scaffolds, the stiffest scaffolds also showed increased cell number and enhanced cellular distribution when compared to the other groups. Taken together, these results indicate that crosslinking can be used to produce collagen-glycosaminoglycan scaffolds with a range of compressive moduli, and that increased stiffness enhances cellular activity within the scaffolds.

Osteomyelitis is an inflammatory bone disease that is caused by an infecting microorganism and leads to progressive bone destruction and loss. The most common causative species are the usually commensal staphylococci, with and responsible for the majority of cases. Staphylococcal infections are becoming an increasing global concern, partially due to the resistance mechanisms developed by staphylococci to evade the host immune system and antibiotic treatment. In addition to the ability of staphylococci to withstand treatment, surgical intervention in an effort to remove necrotic and infected bone further exacerbates patient impairment. Despite the advances in current health care, osteomyelitis is now a major clinical challenge, with recurrent and persistent infections occurring in approximately 40% of patients. This review aims to provide information about staphylococcus-induced bone infection, covering the clinical presentation and diagnosis of osteomyelitis, pathophysiology and complications of osteomyelitis, and future avenues that are being explored to treat osteomyelitis.

CitationHaugh MG, Jaasma MJ, O'Brien FJ. The effect of dehydrothermal treatment on the mechanical and structural properties of collagen-GAG scaffolds. Journal of Biomedical Materials Research A. 2009 May;89(2):363-9.-Use LicenceAttribution-Non-Commercial-ShareAlike 1.0 You are free:• to copy, distribute, display, and perform the work.• to make derivative works. Under the following conditions:• Attribution -You must give the original author credit.• Non-Commercial -You may not use this work for commercial purposes.• AbstractThe mechanical properties of a tissue engineering scaffold are critical for preserving structural integrity and functionality during both in vivo implantation and long-term performance. In addition, the mechanical and structural properties of the scaffold can direct cellular activity within a tissue-engineered construct. In this context, the aim of this study was to investigate the effects of dehydrothermal (DHT) treatment on the mechanical and structural properties of collagen-glycosaminoglycan (CG) scaffolds.Temperature (105-180°C) and exposure period (24-120 h) of DHT treatment were varied to determine their effect on the mechanical properties, crosslinking density and denaturation of CG scaffolds. As expected, increasing the temperature and duration of DHT treatment resulted in an increase in the mechanical properties. Compressive properties increased up to 2-fold, while tensile properties increased up to 3.8-fold.Crosslink density was found to increase with DHT temperature but not exposure period.Denaturation also increased with DHT temperature and exposure period, ranging from 25% to 60% denaturation. Crosslink density was found to be correlated with compressive modulus, whilst denaturation was found to correlate with tensile modulus. Taken together, these results indicate that DHT treatment is a viable technique for altering the mechanical properties of CG scaffolds. The enhanced mechanical properties of DHTtreated CG scaffolds improves their suitability for use both in vitro and in vivo. In addition, this work facilitates investigation of the effects of mechanical properties and denaturation on cell activity in a 3D environment.

BackgroundBone grafts are required to repair large bone defects after tumour resection or large trauma. The availability of patients' own bone tissue that can be used for these procedures is limited. Thus far bone tissue engineering has not lead to an implant which could be used as alternative in bone replacement surgery. This is mainly due to problems of vascularisation of the implanted tissues leading to core necrosis and implant failure. Recently it was discovered that embryonic stem cells can form bone via the endochondral pathway, thereby turning in-vitro created cartilage into bone in-vivo. In this study we investigated the potential of human adult mesenchymal stem cells to form bone via the endochondral pathway.MethodsMSCs were cultured for 28 days in chondrogenic, osteogenic or control medium prior to implantation. To further optimise this process we induced mineralisation in the chondrogenic constructs before implantation by changing to osteogenic medium during the last 7 days of culture.ResultsAfter 8 weeks of subcutaneous implantation in mice, bone and bone marrow formation was observed in 8 of 9 constructs cultured in chondrogenic medium. No bone was observed in any samples cultured in osteogenic medium. Switch to osteogenic medium for 7 days prevented formation of bone in-vivo. Addition of β-glycerophosphate to chondrogenic medium during the last 7 days in culture induced mineralisation of the matrix and still enabled formation of bone and marrow in both human and rat MSC cultures. To determine whether bone was formed by the host or by the implanted tissue we used an immunocompetent transgenic rat model. Thereby we found that osteoblasts in the bone were almost entirely of host origin but the osteocytes are of both host and donor origin.ConclusionsThe preliminary data presented in this manuscript demonstrates that chondrogenic priming of MSCs leads to bone formation in vivo using both human and rat cells. Furthermore, addition of β-glycerophosphate to the chondrogenic medium did not hamper this process. Using transgenic animals we also demonstrated that both host and donor cells played a role in bone formation. In conclusion these data indicate that in-vitro chondrogenic differentiation of human MSCs could lead to an alternative and superior approach for bone tissue engineering.