"In vitro" dissolution of coral in peritoneal or fibroblast cell cultures

Engineering tubular bone using mesenchymal stem cell sheets and coral particles

The development of bone tissue engineering has provided new solutions for bone defects. However, the cell-scaffold-based approaches currently in use have several limitations, including low cell seeding rates and poor bone formation capacity. In the present study, we developed a novel strategy to engineer bone grafts using mesenchymal stem cell sheets and coral particles. Rabbit bone marrow mesenchymal stem cells were continuously cultured to form a cell sheet with osteogenic potential and coral particles were integrated into the sheet. The composite sheet was then wrapped around a cylindrical mandrel to fabricate a tubular construct. The resultant tubular construct was cultured in a spinner-flask bioreactor and subsequently implanted into a subcutaneous pocket in a nude mouse for assessment of its histological characteristics, radiological density and mechanical property. A similar construct assembled from a cell sheet alone acted as a control. In vitro observations demonstrated that the composite construct maintained its tubular shape, and exhibited higher radiological density, compressive strength and greater extracellular matrix deposition than did the control construct. In vivo experiments further revealed that new bone formed ectopically on the composite constructs, so that the 8-week explants of the composite sheets displayed radiological density similar to that of native bone. These results indicate that the strategy of using a combination of a cell sheet and coral particles has great potential for bone tissue engineering and repairing bone defects.

Biomaterial effects in articular cartilage tissue engineering using polyglycolic acid, a novel marine origin biomaterial, IGF-I, and TGF-beta 1

Bovine articular chondrocytes were seeded on either polyglycolic acid (PGA) non-woven mesh scaffolds or a biomatrix from the species Porites lutea (POR). These constructs were cultured for 6 weeks in the presence of insulin-like growth factor (IGF)-I (10 ng/ml or 100 ng/ml) or transforming growth factor (TGF)-beta 1 (5 ng/ml or 30 ng/ml) to determine the in-vitro articular cartilage regeneration capacity of each. Histology, deoxyribonucleic acid content, collagen I and II (immunohistochemistry and enzyme-linked immunosorbent assay), and glycosaminoglycan (GAG) contents were measured at 0 weeks, 2 weeks, and 6 weeks to assess the characteristics of chondrogenesis. Both scaffolds supported the maintenance of the chondrocytic phenotype, as evidenced by the predominance of collagen II and the presence of rounded chondrocytes embedded in lacunae. Regardless of growth factor treatment, cells cultured on PGA scaffolds produced more collagen type II than those cultured on POR. Conversely, by 6 weeks, cells cultured on POR scaffolds produced more GAG than those cultured on PGA scaffolds, again regardless of the growth factor used. Across the two groups, 100 ng/ml of IGF-I had the greatest overall effect in GAG content. This work indicates that PGA and the POR scaffolds are both effective growth matrices for articular cartilage, with each scaffold exhibiting different yet desirable profiles of articular cartilage growth.

Effects of autologous platelet lysates on ceramic particle resorption and new bone formation in critical size defects: The role of anatomical sites

This study investigated the effects of rabbit autologous platelet lysates (APL) on the performance of fillers consisting of calcium carbonate ceramic particles (CP) pertinent to new bone formation and repair. Critical-size defects in rabbit femurs and calvaria were filled with CP alone, CP plus APL, and CP plus APL with or without thrombin (THR). After 6 weeks, resorption of CP occurred under all conditions tested in the present study. Compared with respective CP alone controls, addition of APL resulted in significantly higher ceramic resorption, as evidenced by decreased ceramic particle diameter (p < 0.01) and number (p < 0.01) at both defect sites. The presence of THR prevented reduction of both CP diameter and number in the femoral defect sites. Addition of APL to the CP resulted in a significant (p < 0.03) decrease in new bone area at the calvarial sites, but not at the femoral sites; moreover, when THR was added to the CP plus APL fillers, bone formation in the femoral defects was significantly (p < 0.05) reduced. In addition to differences in the respective anatomical and cellular milieu, the biochemical events induced by mechanical loading at the femurs may explain the reduced ceramic particle resorption as well as the enhanced new bone formation when compared with the results obtained at the calvarial defect sites.

Preparation of macroporous calcium phosphate cement tissue engineering scaffold

Unlike sintered hydroxyapatite there is evidence to suggest that calcium phosphate cement (CPC) is actively remodelled in vivo and because CPC is formed by a low-temperature process, thermally unstable compounds such as proteins may be incorporated into the matrix of the cement which can then be released after implantation. The efficacy of a macroporous CPC as a bone tissue engineering scaffold has been reported; however, there have been few previous studies on the effect of macroporosity on the mechanical properties of the CPC. This study reports a novel method for the formation of macroporous CPC scaffolds, which has two main advantages over the previously reported manufacturing route: the cement matrix is considerably denser than CPC formed from slurry systems and the scaffold is formed at temperatures below room temperature. A mixture of frozen sodium phosphate solution particles and CPC powder were compacted at 106 MPa and the sodium phosphate was allowed to melt and simultaneously set the cement. The effect of the amount of porogen used during processing on the porosity, pore size distribution and compressive strength of the scaffold was investigated. It was found that macroporous CPC could reliably be fabricated using cement:ice ratios as low as 5:2.

Transforming growth factor beta released from natural coral implant enhances bone growth at calvarium of mature rat

Earlier studies have shown that transforming growth factor beta (TGF-beta) has the capability of enhancing bone formation after a single application to an orthotopic site. We investigated whether 1, 5, or 25 microg of recombinant human TGF-beta1 added to porous natural coral (NC) blocks could promote bone ingrowth in a critical size defect (CSD) model in nongrowing rats. A 6-mm CSD in the parietal bone of Wistar rats was filled with NC disks, which were retrieved at 3 and 8 weeks. We prepared undecalcified sections for microscopy and histomorphometry to study bone formation in the implants. The differences in the means of the measured variables were compared with a one-way analysis of variance and Tukey's Student range test, and p values smaller than 0.05 were considered statistically significant. Bone formation was enhanced in all the TGF-beta1-treated implants at 8 weeks in comparison with the controls, but none of the implants showed complete bridging across the defect. The number of macrophages and giant cells was reduced in the TGF-beta1 implants, which showed less resorption and more intact structure than the coral controls. Void areas without any fibrous tissue ingrowth were found only in the TGF-beta1-treated implants, which may partly explain the reduced resorption. The data suggested that TGF-beta1 induced enhanced but limited bone formation in mature rats and prevented resorption of the coral calcium carbonate matrix, possibly by hindering reactive cell formation and fibrous tissue ingrowth.

Resorption kinetics of eggshell: an in vivo study

Eggshell has been recently introduced as a bone substitute candidate in reconstructive surgery. The aim of this experimental study study was to determine its degradation rate in both a skeletal and extraskeletal site. In experiment 1, eggshell particles with four different sizes (50, 75, 150, and 300 microns in diameter) were implanted in subcutaneous pouches of 30 rats. In experiment 2, a fragment of ostrich eggshell was implanted on the nasal dorsum of 10 rats. Animals were sacrificed at 1 (N = 10), 2 (N = 10), and 4 months (N = 10) during the first stage of the study, and at 1 year during the second stage of the study. The results were assessed by X-ray examination and routine histological techniques. In experiment 1, all animals healed uneventfully. At 1 month, only 50-micron particles had undergone resorption. At 2 months, both 50- and 75-micron particles had undergone resorption. At 4 months, the 150- and 300-micron particles were resorbed incompletely. Histologically, the eggshell elicited a mild inflammatory reaction at 1 month that decreased progressively at further stages. In experiment 2, all animals except one healed uneventfully. Radiologically, the eggshell implant displayed a noticeable stability. Histologically, seven of nine implants were encapsulated, but two of them were surrounded by a bony rim. In conclusion, eggshell is a resorbable implant, but the degradation kinetic is size dependent. Large ostrich grafts are also suitable as onlay graft, but a complementary osteosynthesis is recommended to enhance osteointegration.

Natural coral as bone-defect-filling material

Natural coral (NC) has been studied experimentally and clinically as a bone substitute, but its resorption rate and possible replacement by bone still need to be defined in humans. In this study bicortical bone was harvested from the iliac crest of 10 patients. The defect was filled with a NC block, and changes were monitored by X-rays and quantitative CT scans for a mean of 2.1 years. A biopsy was taken at 1 year. The purpose of the study was to investigate the resorption rate and pattern of NC (Porites) implants and the replacement, if any, of the implant by new bone. The blocks underwent centripetal resorption, but all the blocks still could be detected by X-rays and CT scans at the end of the follow-up period. The density of the remaining block did not change. Seven of the 10 implants were smaller than 50% of their original size at the end of the study. Bone ingrowth could be observed only in two of seven biopsies. One implant had to be removed after 1.7 years due to infection. The study shows that resorption of natural coral proceeds centripetally and apparently more rapidly when accompanied by tissue ingrowth. None of the blocks resorbed completely, and the defect at the iliac crest had not been restored by the end of the study.

Coralline bone graft substitutes

Coralline porous ceramics are biocompatible and osteoconductive implants. They have proven to be effective as bone graft substitutes in large animal models and in humans. Bone and supporting soft tissue grow into and throughout their porosity if the implant is placed in direct apposition to viable bone and the interfaces are stabilized. The bone within the implant remodels in response to Wolff's law. Both the implant properties (chemistry and porosity) and the biologic environment modulate the rate of implant resorption. Composite technology with resorbable polymers can improve the mechanical properties of these ceramics.