OBJECTIVE:To develop and to characterize a human preadipocyte cell strain with high capacity for adipose differentiation serving as a model for studying human adipocyte development and metabolism in vitro. METHODS: Cells were derived from the stromal cells fraction of subcutaneous adipose tissue of an infant with Simpson ± Golabi ± Behmel syndrome (SGBS). Adipose differentiation was induced under serum-free culture conditions by exposure to 10 nM insulin, 200 pM triiodothyronine, 1 mM cortisol and 2 mM BRL 49653, a PPARg agonist. RESULTS: During the differentiation process SGBS cells developed a gene expression pattern similar to that found in differentiating human preadipocytes with a characteristic increase in fat cell-speci®c mRNAs encoding lipoprotein lipase (LPL), glycero-3-phosphate dehydrogenase (GPDH), GLUT4, leptin and others. Differentiated SGBS cells exhibited an increase in glucose uptake upon insulin stimulation and in glycerol release upon catecholamine exposure. SGBS adipocytes were morphologically, biochemically and functionally identical to in vitro differentiated adipocytes from healthy subjects. However, while preadipocytes from healthy control infants rapidly lost their capacity to differentiate after a few cell divisions in culture, SGBS cells maintained their differentiation capacity over many generations: upon appropriate stimulation 95% of SGBS cells of generation 30 developed into adipocytes. A mutation in the glypican 3 gene was not detected in the patient. Thus, it remains unclear whether the molecular alteration in SGBS cells is also responsible for the high differentiation capacity and further investigations are required. CONCLUSION: The human cell strain described here provides an almost unlimited source of human preadipocytes with high capacity for adipose differentiation and may, therefore, represent a unique tool for studying human fat cell development and metabolism. International Journal of Obesity (2001) 25, 8 ± 15

The establishment of cartilage regenerative medicine is an important clinical issue, but the search for cell sources able to restore cartilage integrity proves to be challenging. Human mesenchymal stromal cells (MSCs) are prone to form epiphyseal or hypertrophic cartilage and have an age-related limited proliferation. On the other hand, it is difficult to obtain functional chondrocytes from human embryonic stem cells (ESCs). Moreover, the ethical issues associated with human ESCs are an additional disadvantage of using such cells. Since their discovery in 2006, induced pluripotent stems cells (iPSCs) have opened many gateways to regenerative medicine research, especially in cartilage tissue engineering therapies. iPSCs have the capacity to overcome limitations associated with current cell sources since large numbers of autologous cells can be derived from small starting populations. Moreover, problems associated with epiphyseal or hypertrophic-cartilage formation can be overcome using iPSCs. iPSCs emerge as a promising cell source for treating cartilage defects and have the potential to be used in the clinical field. For this purpose, robust protocols to induce chondrogenesis, both in vitro an in vivo, are required. This review summarises the recent progress in iPSC technology and its applications for cartilage repair.

We analyzed tissue and cells from a stationary and a rapidly growing hyperplastic callus from a patient with osteogenesis imperfecta (OI) type IV and compared the results with those of compact bone and skin fibroblasts of an age-matched control.Collagen and protein contents per cell were low in the callus tissues and collagen I and III were overmodified as evidenced by an elevated level of hydroxylysine. The degree of lysyl hydroxylation was highest in those regions that appeared most immature by histological examination. Lysyl hydroxylation approached normal levels in collagen from the stationary callus and from the center of the growing callus. Overmodification of collagen was not seen in compact bone or cell cultures (neither skin fibroblasts nor callus cells) from the patient. Elevation of hydroxylysine in collagen from OI patients is generally attributed to mutations that delay triple helix formation. Our observations suggest that the varying degree of collagen modifications may occur in consequence of regulatory mechanisms during bone development and tissue repair. These mechanisms may be defective in some patients with 01 as seen in this case with hyperplastic callus formation.

Serum concentrations of procollagen I C-terminal propeptide (PICP) were studied in 74 patients with various forms of non-lethal osteogenesis imperfecta and 27 unaffected family members. Using the standard deviation (SD) score, PICP concentrations were found to be > or = -1 SD in 16%, between -1 and -2 SD in 26% and < or = -2 SD in 58% of the patients with osteogenesis imperfecta compared to healthy controls. PICP values were lowest in osteogenesis imperfecta type I (-2.4 +/- 0.4 SD, n = 37) followed by type III (-1.9 +/- 0.5 SD, n = 13) and type IV (-1.3 +/- 0.7 SD, n = 20). Four patients with osteogenesis imperfecta with an atypical clinical course had normal or even elevated levels which may indicate heterogeneity in the underlying primary defects. In osteogenesis imperfecta type I, PICP concentrations proved to be a helpful serum marker for pedigree screening. Osteocalcin was high in 25 of 28 patients with osteogenesis imperfecta in the first decade but only in 1 of 18 older patients. Insulin-like growth factor-I was within the normal range in 53 cases of osteogenesis imperfecta, decreased in 2 and elevated in 3 patients. We conclude that PICP concentration is a useful parameter in the clinical management of osteogenesis imperfecta, including the assessment of future therapeutic interventions.

Background and purpose: A main challenge in the therapy of osteoarthritis (OA) is the development of drugs that will modify the disease. Reliable test systems are necessary to enable an efficient screening of therapeutic substances. We therefore established a chondrocyte-based in vitro cell culture model in order to characterize different p38MAPK inhibitors. Experimental approach: Interleukin-1b (IL-1b)-stimulated human OA chondrocytes were treated with the p38MAPK inhibitors Birb 796, pamapimod, SB203580 and the new substance CBS-3868. Birb 796-and SB203580-treated cells were analysed in a genome-wide microarray analysis. The efficacy of all inhibitors was characterized by quantitative gene expression analysis and the quantification of PGE2 and NO release. Key results: Microarray analysis revealed inhibitor-specific differences in gene expression. Whereas SB203580 had a broad effect on chondrocytes, Birb 796 counteracted the IL-1b effect more specifically. All p38MAPK inhibitors significantly inhibited the IL-1b-induced gene expression of COX-2, mPGES1, iNOS, matrix metalloproteinase 13 (MMP13) and TNFRSF11B, as well as PGE2 release. Birb 796 and CBS-3868 showed a higher efficacy than SB203580 and pamapimod at inhibiting the expression of COX-2 and MMP13 genes, as well as PGE2 release. In the case of mPGES1 and TNFRSF11B gene expression, CBS-3868 exceeded the efficacy of Birb 796. Conclusions and implications:Our test system could differentially characterize inhibitors of the same primary pharmaceutical target. It reflects processes relevant in OA and is based on chondrocytes that are mainly responsible for cartilage degradation. It therefore represents a valuable tool for drug screening in between functional in vitro testing and in vivo models.

In rare cases of osteogenesis imperfecta, an "overshoot" growth of new bone may occur, which, clinically gives the impression of a tumour. This condition is known as hyperplastic callus formation. Morphology showed an excessive mixed desmal-chondral osteoneogenesis. Atypical collagen fibrils in non-callus tissue represent an indicator for this callus formation in individual patients.

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A patient suffering from a severe form of Ehlers-Danlos syndrome is presented (EDS type VII). The presence of bilateral congenital hip dislocation, generalized joint hypermobility and a soft hyperelastic skin with abnormal scarring suggested a specific collagen type I defect. SDS-PAGE analysis of collagens secreted into the medium of fibroblast cultures showed a retarded migration of more than half of the alpha 2(I) chains. CNBr peptide mapping of the HPLC-purified altered chain localized the mutant locus to the N-terminal region of the protein. cDNA analysis of the corresponding gene COL1A2 revealed, in addition to the expected collagen sequence, a transcript missing the entire exon 6. This exon encodes a major crosslinking site within collagen fibres as well as the N-propeptidase cleavage site. The skipping of exon 6 is caused by a splice site mutation substituting an A for a G at the first nucleotide of intron 6.