Comparative, osteochondral defect repair: stem cells versus chondrocytes versus bone morphogenetic protein-2, solely or in combination.

Full-thickness articular cartilage damage does not resolve spontaneously. Studies with growth factors, implantation of autologous chondrocytes and mesenchymal stem cells have led to variable, to some extent inconsistent, results. This work compares osteochondral knee-defect repair in rabbits upon implantation of a previously described alginate/(poly(lactic-co-glycolic) acid (PLGA) osteochondral scaffold in distinct conditions. Systems were either in vitro pre-cultured with a small number of allogeneic chondrocytes under fibroblast growth factor (FGF)-2 stimulation or the same amount of allogeneic, marrow derived, mesenchymal stem cells (without any pre-differentiation), or loaded with microsphere-encapsulated bone morphogenetic protein (BMP)-2 within the alginate layer, or holding combinations of one or the other cell type with BMP-2. The experimental limit was 12 weeks, because a foregoing study with this release system had shown a maintained tissue response for at least 24 weeks post-operation. After only 6 weeks, histological analyses revealed newly formed cartilage-like tissue, which resembled the adjacent, normal cartilage in cell as well as BMP-2 treated defects, but cell therapy gave higher histological scores. This advantage evened out until 12 weeks. Combinations of cells and BMP-2 did not result in any additive or synergistic effect. Equally efficient osteochondral defect repair was achieved with chondrocyte, stem cell, and BMP-2 treatment. Expression of collagen X and collagen I, signs of ongoing ossification, were histologically undetectable, and the presence of aggrecan protein indicated cartilage-like tissue. In conclusion, further work should demonstrate whether spatiotemporally controlled, on-site BMP-2 release alone could become a feasible therapeutic approach to repair large osteochondral defects.

Reticulated vitreous carbon: a useful material for cell adhesion and tissue invasion.

Diverse carbon materials have been used for tissue engineering and clinical implant applications with varying success. In this study, commercially available reticulated vitreous carbon (RVC) foams were tested in vitro and in vivo for compatibility with primary cell adhesion and tissue repair. Pores sizes were determined as 279 ± 98 µm. No hydroxyapatite deposition was detected after immersion of the foams in simulated body fluid. Nonetheless, RVC provided an excellent support for adhesion of mesenchymal stem cells (MSCs) as well as primary chondrocytes without any surface pre-treatment. Live cell quantification revealed neutral behaviour of the material with plastic adhered chondrocytes but moderate cytotoxicity with MSCs. Yet, rabbit implanted foams exhibited good integration in subcutaneous pockets and most importantly, total defect repair in bone. Probably due to the stiffness of the material, incompatibility with cartilage regeneration was found. Interestingly and in contrast to several other carbon materials, we observed a total lack of foreign body reactions. Our results and its outstanding porous interconnectivity and availability within a wide range of pore sizes convert RVC into an attractive candidate for tissue engineering applications in a variety of bone models and for ex vivo cell expansion for regenerative medical applications.

Growth inhibition by dehydrothyrsiferol - a non-Pgp modulator, derived from a marine red alga - in human breast cancer cell lines.

The novel marine terpenoid dehydrothyrsiferol (DHT) has been isolated from a Canarian red alga Laurencia viridis sp. nov (Ceramiales, Rhodomelaceae) (1). Its cytotoxicity against three human breast cancer cell lines, namely T47D, ZR-75-1, and Hs578T was examined and compared with the chemotherapeutic compound doxorubicin and the mitosis-inhibitor colchicine. Primary breast carcinomas exhibit MDR1 gene expression (3). As the investigated mammary cell lines did not exhibit rhodamine 123 efflux we proved in a P-glycoprotein (Pgp) overexpressing human epidermoid cancer cell line that the marine metabolite does not modulate Pgp mediated drug transport. Therefore, it could be used in Pgp expressing cancer cells without interference.

Inhibitory effects of a novel marine terpenoid on sensitive and multidrug resistant KB cell lines.

Mechanisms of growth inhibition by the novel marine compound dehydrothyrsiferol (DHT) were investigated in a sensitive and an MDR+ human epidermoid cancer cell line. DHT was found to circumvent multidrug resistance mediated by P-glycoprotein. Cell cycle analysis revealed an accumulation in S-phase. The anchorage independent clonogenic growth in soft agar was not significantly reduced at IC50 concentrations. Reduced cell growth caused by induction of apoptotic or necrotic cell death could not be verified. Therefore, cell proliferation during an incubation period of five days was measured and found to be significantly reduced. We conclude that growth inhibition by dehydrothyrsiferol in KB cancer cells is not mediated by apoptosis but by growth retardation; the reasons for this are worth being investigated in detail.

Value of serum soluble tumour necrosis factor concentrations in the diagnosis and prognosis of renal graft rejection.

Up to the present the histological diagnosis of rejection through biopsy is still the only possibility for a definite rejection diagnosis. We searched for a reliable non-invasive marker of renal graft rejection. By means of a highly sensitive enzyme-linked immunosorbent assay we investigated the changes in the concentration of serum soluble TNF receptor in kidney graft recipients with different clinical courses according to their graft tolerance. sTNF-R in 19 patients with stable graft function (5.3 +/- 3.2 ng/ml) did not differ significantly from those detected in 22 healty volunteers (4.1 +/- 2.2 ng/ml). In contrast 17 patients suffering from acute graft rejection showed highly significantly increases (23 +/- 8.3 ng/ml, P < 0.0001). These elevated concentrations returned to prerejection rejection values after a 3-day anti-rejection therapy with high-dose methylprednisolone. In 18 patients with an irreversible, chronic kidney graft rejection we could demonstrate significantly increased sTNF-R values (20 +/- 7.9 ng/ml); eight of those patients did not reflect on the anti-rejection therapy, so that the elevated concentrations remained even after the administration of high-dose corticosteroids and ATG. Additionally we found soluble TNF receptor concentrations to be increased earlier than other commonly used biochemical parameters such as creatinine. Soluble TNF-R also proved to be useful for the differentiation of cyclosporin nephrotoxicity. Therefore we believe that the soluble TNF-R and its concentration course may be of diagnostic and prognostic value in kidney graft rejection, as it supports the diagnosis of transplant rejection, indicates the rejection event very early, and reflects the response to anti-rejection therapy.