Preclinical good laboratory practice-compliant safety study to evaluate biodistribution and tumorigenicity of a cartilage advanced therapy medicinal product (ATMP).

BACKGROUND: The clinical development of advanced therapy medicinal products (ATMPs), a new class of drugs, requires initial safety studies that deviate from standard non-clinical safety protocols. The study provides a strategy to address the safety aspects of biodistribution and tumorigenicity of ATMPs under good laboratory practice (GLP) conditions avoiding cell product manipulation. Moreover, the strategy was applied on a human ATMP for cartilage repair. METHODS: The testing strategy addresses biodistribution and tumorigenicity using a multi-step analysis without any cell manipulation to exclude changes of test item characteristics. As a safeguard measurement for meeting regulatory expectations, the project design and goals were discussed continuously with the regulatory authority using a staggered scientific advice concept. Subsequently, the strategy was applied to co.don chondrosphere® (huChon spheroid), a tissue-engineered matrix-free ATMP of human normal chondrocytes. In both the biodistribution and tumorigenicity studies, huChon spheroids were implanted subcutaneously into 40 immunodeficient mice. Biodistribution was studied 1 month after implantation. A skin disc containing the huChon spheroid, two surrounding skin rings and selected organs were analyzed by validated, gender-specific, highly-sensitive triplex qPCR and by immunohistochemistry (IHC). RESULTS: No human DNA was detected in distant skin rings and analyzed organs. IHC revealed no direct or indirect indications of cell migration. Tumorigenicity was assessed 6 months after huChon spheroid implantation by palpation, macroscopic inspection, histology and IHC. No mice from the huChon spheroid group developed a tumor at the implantation site. In two mice, benign tumors were detected that were negative for HLA-ABC, suggesting that they were of spontaneous murine origin. CONCLUSIONS: In summary, the presented strategy using a multi-step analysis was confirmed to be suitable for safety studies of ATMPs.

Comprehensive characterization of chondrocyte cultures in plasma and whole blood biomatrices for cartilage tissue engineering.

Many synthetic polymers and biomaterials have been used as matrices for 3D chondrocyte seeding and transplantation in the field of cartilage tissue engineering. To develop a fully autologous carrier for chondrocyte cultivation, we examined the feasibility of allogeneic plasma and whole blood-based matrices and compared them to agarose constructs. Primary articular chondrocytes isolated from 12-month-old pigs were embedded into agarose, plasma and whole blood matrices and cultivated under static-free swelling conditions for up to four weeks. To evaluate the quality of the synthesized extracellular matrix (ECM), constructs were subjected to weekly examinations using histological staining, spectrophotometry, immunohistochemistry and biochemical analysis. In addition, gene expression of cartilage-specific markers such as aggrecan, Sox9 and collagen types I, II and X was determined by RT-PCR. Chondrocyte morphology was assessed via scanning electron microscopy and viability staining, including proliferation and apoptosis assays. Finally, (13) C NMR spectroscopy provided further evidence of synthesis of ECM components. It was shown that chondrocyte cultivation in allogeneic plasma and whole-blood matrices promoted sufficient chondrocyte viability and differentiation behaviour, resulting in neo-formation of a hyaline-like cartilage matrix.

RGD-dependent integrins are mechanotransducers in dynamically compressed tissue-engineered cartilage constructs.

Recent studies have shown that integrins act as mechanoreceptors in articular cartilage. In this study, we examined the effect of blocking RGD-dependent integrins on both ECM gene expression and ECM protein synthesis. Chondrocytes were isolated from full-depth porcine articular cartilage and seeded in 3% agarose constructs. These constructs were loaded in compression with 15% strain at 0.33 and 1 Hz for 12h, in the presence or absence of GRGDSP, which blocks RGD-dependent integrin receptors. The levels of mRNA for aggrecan, collagen II and MMP-3 were determined by semi-quantitative PCR at several time points up to 24h post-stimulation. DNA and sGAG content were determined at several time points up to 28 days post-stimulation. At 0.33 Hz, the mRNA levels for aggrecan and MMP-3 were increased after loading, but the mRNA levels for collagen II remained unchanged. Incubation with GRGDSP counteracted these effects. Loading at 1 Hz led to increased mRNA levels for all three molecules directly after loading and these effects were counteracted by incubation with GRGDSP. The constructs that were loaded at 0.33 Hz showed a lower amount of sGAG, compared to the unstrained control. In contrast, loading at 1 Hz caused an increase in sGAG deposition over the culture period. Blocking integrins had only a counteracting effect on the long-term biosynthetic response of constructs that were compressed at 1 Hz. The results confirmed the role of RGD-dependent integrins as mechanotransducers in the regulation of both ECM gene expression and matrix biosynthesis for chondrocytes seeded in agarose under the applied loading regime. Interestingly, this role seems to be dependent on the applied loading frequency.

Near intron positions are reliable phylogenetic markers: an application to holometabolous insects.

Today, the reconstruction of the organismal evolutionary tree is based mainly on molecular sequence data. However, sequence data are sometimes insufficient to reliably resolve in particular deep branches. Thus, it is highly desirable to find novel, more reliable types of phylogenetic markers that can be derived from the wealth of genomic data. Here, we consider the gain of introns close to older preexisting ones. Because correct splicing is impeded by very small exons, nearby pairs of introns very rarely coexist, that is, the gain of the new intron is nearly always associated with the loss of the old intron. Both events may even be directly connected as in cases of intron migration. Therefore, it should be possible to identify one of the introns as ancient (plesiomorphic) and the other as novel (derived or apomorphic). To test the suitability of such near intron pairs (NIPs) as a marker class for phylogenetic analysis, we undertook an analysis of the evolutionary positions of bees and wasps (Hymenoptera) and beetles (Coleoptera) in relation to moths (Lepidoptera) and dipterans (Diptera) using recently completed genome project data. By scanning 758 putatively orthologous gene structures of Apis mellifera (Hymenoptera) and Tribolium castaneum (Coleoptera), we identified 189 pairs of introns, one from each species, which are located less than 50 nt from each other. A comparison with genes from 5 other holometabolan and 9 metazoan outgroup genomes resulted in 22 shared derived intron positions found in beetle as well as in butterflies and/or dipterans. This strongly supports a basal position of hymenopterans in the holometabolous insect tree. In addition, we found 31 and 12 intron positions apomorphic for A. mellifera and T. castaneum, respectively, which seem to represent changes inside these branches. Another 12 intron pairs indicate parallel intron gains or extraordinarily small exons. In conclusion, we show here that the analysis of phylogenetically nested, nearby intron pairs is suitable to identify evolutionarily younger intron positions and to determine their relative age, which should be of equal importance for the understanding of intron evolution and the reconstruction of the eukaryotic tree.