In vitro and in vivo evaluation of akermanite bioceramics for bone regeneration.
ABSTRACT This study investigated the effects of a calcium magnesium silicate bioceramic (akermanite) for bone regeneration in vitro and in vivo, with beta-tricalcium phosphate (beta-TCP) as a control. In vitro, the human bone marrow-derived mesenchymal stromal cells (hBMSCs) were cultured in an osteogenic medium supplemented with a certain concentration of two bioceramics' extracts for 20 days. An MTT assay showed that akermanite extract promoted proliferation of hBMSC significantly more than did beta-TCP extract. The results of alkaline phosphatase (ALP) activity test and the expression of osteogenic marker genes such as ALP, osteopontin (OPN), osteocalcin (OCN) and bone sialoprotein (BSP) demonstrated that the osteogenic differentiation of hBMSC was enhanced more by akermanite extract than by beta-TCP extract. In vivo, a histomorphology analysis and histomorphometry of the two porous bioceramics implants in rabbit femur defect models indicated that both in early- and late-stage implantations, akermanite promoted more osteogenesis and biodegradation than did beta-TCP; and in late-stage implantations, the rate of new bone formation was faster in akermanite than in beta-TCP. These results suggest that akermanite might be a potential and attractive bioceramic for tissue engineering.
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ABSTRACT: Alkaline phosphatase (ALP) catalyzes the hydrolysis of phosphate esters and it seems to be a prerequisite for normal skeletal mineralization. Also, ALP is the most widely recognized marker of osteoblast phenotypes. By a tissue regenerative technique called Guided Bone Regeneration (GBR), it is possible nowadays to regenerate small bony defects. The aim of the present study was to investigate early events in bone healing and neogenesis by studying histochemically the temporal and local appearance of the marker Alkaline Phosphatase (ALP) in a GBR model system. Nine healthy volunteers (5 males, 4 females, mean age 31.7 years) participated in the experiment. After raising a mucoperiosteal flap from the mandibular second molar to the retromolar area in each volunteer, a hollow titanium test cylinder was placed into a congruent bony bed and the coronal end of the cylinder was closed with an ePTFE-membrane. Then the flap was adapted and sutured to obtain primary wound closure. After 2, 7 and 12 weeks, the regenerated tissue within the cylinders was harvested. Histologically, ALP activity was observed associated with the osteoid seams in the very basal part of the regenerate where new bone trabeculae were in the process of being formed. More coronally, large round cells seemed to secrete an ALP-positive substance since in the center of such cell clusters strong ALP activity located extracellularly was detected. In the present experiment, ALP seemed to have been an early sign of osteoblast secretion of a matrix which subsequently was determined to become osteoid. ALP activity was never seen isolated within connective tissue and away from bone. This is an indication that its source is linked to existing bone. The present study has documented for the first time the appearance of ALP activity in guided bone regenerations in humans. It has revealed that: 1) Osteogenesis in guided bone regeneration is preceded by localized, marked expression of ALP in an organized connective tissue environment. 2) Bone neogenesis is an early event in this experimental setup and may be detected already 2 weeks after wounding. 3) Expression of ALP and subsequent bone neogenesis is originating from and topographically linked to pre-existing bone structures.Clinical Oral Implants Research 05/2001; 12(2):121-7. · 3.43 Impact Factor
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ABSTRACT: Most tissue engineering (TE) strategies for creating functional replacement tissues or organs rely on the application of temporary three-dimensional scaffolds to guide the proliferation and spread of seeded cells in vitro and in vivo. The characteristics of TE scaffolds are major concerns in the quest to fabricate ideal scaffolds. This paper identifies essential structural characteristics and the pre-requisites for fabrication techniques that can yield scaffolds that are capable of directing healthy and homogeneous tissue development. Emphasis is given to solid freeform (SFF), also known as rapid prototyping, technologies which are fast becoming the techniques of choice for scaffold fabrication with the potential to overcome the limitations of conventional manual-based fabrication techniques. SFF-fabricated scaffolds have been found to be able to address most, if not all the macro- and micro-architectural requirements for TE applications. This paper reviews the application/potential application of state-of-the-art SFF fabrication techniques in creating TE scaffolds. The advantages and limitations of the SFF techniques are compared. Related research carried out worldwide by different institutions, including the authors' research are discussed.Biomaterials 07/2003; 24(13):2363-78. · 7.60 Impact Factor
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ABSTRACT: Bioactive ceramics developed during the past few decades have interesting properties from the biological standpoint, but their effects on cellular events remain partially unknown. In the current work, we investigated cellular viability, proliferation, morphology changes and metabolic activity of rat primary culture osteoblasts in contact with the ionic products from the dissolution of a bioactive glass with 60% of silica (BG60S) and a biphasic calcium phosphate (BCP). We observed that although osteoblasts cultured with BG60S showed vacuole formation, cell viability was increased when compared to BCP and control. The vacuole formation was not due to the presence of high calcium concentration in the ionic products from the dissolution of BG60S and was not related to nitric oxide production from the osteoblasts. We did find that high silicon concentration could induce cellular vacuole formation. Additionally, energy dispersive spectroscopy analysis indicated that vacuole contained 75% more silicon than other regions in the cell outside the vacuole. We further found that collagen production was higher in osteoblast cultured in the presence of BG60S compared to BCP and control, while alkaline phosphatase production was similar among cells incubated with BG60S, BCP and control. Together, our results indicate that osteoblast vacuole formation was due to high silicon contents in the dissolution of BG60S and we can suggest that despite the vacuole formation, there is no significant alteration in the bioceramic cell interaction.Biomaterials 08/2004; 25(15):2941-8. · 7.60 Impact Factor