Fabrication of polycaprolactone collagen hydrogel constructs seeded with mesenchymal stem cells for bone regeneration.

The osteogenic differentiation of bone marrow-derived human mesenchymal stem cells (MSCs) in a collagen I hydrogel was investigated. Collagen hydrogels with 7.5 x 10(5) MSCs ml(-1) were fabricated and cultured for 6 weeks in a defined, osteogenic differentiation medium. Histochemistry revealed morphologically distinct, chondrocyte-like cells, surrounded by a sulfated proteoglycan-rich extracellular matrix in the group treated with bone morphogenetic protein 2 (BMP-2), while cells cultured with dexamethasone, ascorbate-2-phosphate, and beta-glycerophosphate displayed a spindle-shaped morphology and deposited a mineralized matrix. Real-time polymerase chain reaction (RT-PCR) analyses revealed a specific chondrogenic differentiation with the expression of cartilage-specific markers in the BMP-2-treated group and a distinct expression pattern of the osteogenic markers alkaline phosphatase (ALP), type I collagen, osteocalcin (OC), and cbfa-1 in the group treated with an osteogenic standard medium. The collagen gels were used to engineer a cell laden medical grade epsilon-polycaprolactone (PCL)-hydrogel construct for segmental bone repair showing good bonding at the scaffold hydrogel interface and even cell distribution. The results show that MSCs cultured in a collagen I hydrogel are able to undergo a distinct osteogenic differentiation pathway when stimulated with specific differentiation factors and suggest that collagen I hydrogels are a suitable means to facilitate cell seeding of scaffolds for bone tissue engineering applications.

Multiphasic collagen fibre-PLA composites seeded with human mesenchymal stem cells for osteochondral defect repair: an in vitro study.

A promising approach for the repair of osteochondral defects is the use of a scaffold with a well-defined cartilage-bone interface. In this study, we used a multiphasic composite scaffold with an upper collagen I fibre layer for articular cartilage repair, separated by a hydrophobic interface from a lower polylactic acid (PLA) part for bone repair. Focusing initially on the engineering of cartilage, the upper layer was seeded with human mesenchymal stem cells (hMSCs) suspended in a collagen I hydrogel for homogeneous cell distribution. The constructs were cultured in a defined chondrogenic differentiation medium supplemented with 10 ng/ml transforming growth factor-beta1 (TGFbeta1) or in DMEM with 10% fetal bovine serum as a control. After 3 weeks a slight contraction of the collagen I fibre layer was seen in the TGFbeta1-treated group. Furthermore, a homogeneous cell distribution and chondrogenic differentiation was achieved in the upper third of the collagen I fibre layer. In the TGFbeta1-treated group cells showed a chondrocyte-like appearance and were surrounded by a proteoglycan and collagen type II-rich extracellular matrix. Also, a high deposition of glycosaminoglycans could be measured in this group and RT-PCR analyses confirmed the induction of chondrogenesis, with the expression of cartilage-specific marker genes, such as aggrecan and collagen types II and X. This multiphasic composite scaffold with the cartilage layer on top might be a promising construct for the repair of osteochondral defects.

Anterior cruciate ligament constructs fabricated from human mesenchymal stem cells in a collagen type I hydrogel.

BACKGROUND: Disruptions of the anterior cruciate ligament (ACL) of the knee joint are common and are currently treated using ligament or tendon grafts. In this study, we tested the hypothesis that it is possible to fabricate an ACL construct in vitro using mesenchymal stem cells (MSC) in combination with an optimized collagen type I hydrogel, which is in clinical use for autologous chondrocyte transplantation (ACT). METHODS: ACL constructs were molded using a collagen type I hydrogel containing 5 x 10(5) MSC/mL and non-demineralized bone cylinders at each end of the constructs. The constructs were kept in a horizontal position for 10 days to allow the cells and the gel to remodel and attach to the bone cylinders. Thereafter, cyclic stretching with 1 Hz was performed for 14 days (continuously for 8 h/day) in a specially designed bioreactor. RESULTS: Histochemical analysis for H and E, Masson-Goldner and Azan and immunohistochemical analysis for collagen types I and III, fibronectin and elastin showed elongated fibroblast-like cells embedded in a wavy orientated collagenous tissue, together with a ligament-like extracellular matrix in the cyclic stretched constructs. No orientation of collagen fibers and cells, and no formation of a ligament-like matrix, could be seen in the non-stretched control group cultured in a horizontal position without tension. RT-PCR analysis revealed an increased gene expression of collagen types I and III, fibronectin and elastin in the stretched constructs compared with the non-stretched controls. DISCUSSION: In conclusion, ACL-like constructs from a collagen type I hydrogel, optimized for the reconstruction of ligaments, and MSC have been fabricated. As shown by other investigators, who analyzed the influence of cyclic stretching on the differentiation of MSC, our results indicate a ligament-specific increased protein and gene expression and the formation of a ligament-like extracellular matrix. The fabricated constructs are still too weak for animal experiments or clinical application and current investigations are focusing on the development of a construct with an internal augmentation using biodegradable fibers.

[In vitro fabrication of tendon substitutes using human mesenchymal stem cells and a collagen type I gel]. / Herstellung von Sehnenkonstrukten aus humanen mesenchymalen Stammzellen und einem Kollagen Typ I Gel.

BACKGROUND AND PURPOSE: Reconstruction of tendon tissue is problematic in many cases. Since direct tendon suture is often impossible, major reconstruction with the use of free tendon transplants or tendon transposition is necessary. Important motor units often have to be sacrificed for reconstructive purposes. In this study we investigated whether long tendon-like substitutes can be fabricated in vitro from human mesenchymal stem cells (MSCs) and a collagen type I gel when cultured under cyclic stretching conditions. MATERIAL AND METHODS: MSCs were obtained from bone marrow aspirates of the iliac crest. Cells were suspended in a collagen type I gel and polymerized in a glass-cylinder with defined size. The fabricated tendon substitutes underwent static stretching for 14 days followed by cyclic stretching for 21 days in a special manufactured bioreactor. Non-stretched substitutes served as a control. RESULTS: Macroscopically the stretched tendon substitutes showed an increased opacity and a smoother surface structure compared to the non-stretched control. The stretched substitutes displayed more spindle-shaped, longitudinal orientated cells, a tendon-like organization of the collagen matrix, and a parallel organization of the collagen fibers when stained with Hematoxylin/Eosin and Elastica. CONCLUSION: Long tendon substitutes could be fabricated from MSCs and a collagen type I gel by cyclic stretching and showed tendon-like parallel collagen fibers and spindle-shaped cells. The use of MSCs in combination with adequate scaffold materials has great therapeutic potential for the development of autologous transplantable tendon substitutes.

[Becoming sedentary, acculturation and infectious diseases: socio-ecological problems of the Bayaka Pygmies]. / Sédentarisation, acculturation et maladies infectieuses, un problème socio-ecologique des Pygmées Bayaka.

The falling of tropical rain forests in Equatorial Africa, and the subsequent penetration of Bantu hoe farmers into the former jungle regions are depriving the Pygmies of the basis for their traditional way of life as roaming hunters and gatherers. Most of the former roaming groups now live in permanent settlements near Bantu villages. But becoming sedentary and adapting to the habits of the Bantu have had catastrophic results for the Pygmies: today, this people suffers to a great extent from infectious diseases and animal parasites, which were once almost unknown among them. In particular, Yaws, a skin disease which is widespread in Africa affects whole tribes. With the loss of their cultural identity their social structure also collapses: formerly free Pygmies get employed as cheap labour on coffee plantations.

[Ethology of the Mediterranean blenny Blennius rouxi Cocco 1833]. / Zur Ethologie des Mittelmeer-Schleimfisches sslennius rouxi Cocco 1833

The Mediterranean blenny Blennius rouxi has been studied mainly in the Banyuls-sur-Mer region. Data on its behaviour have been obtained by skin diving, SCUBA diving and observations in captivity. At Banyuls-sur-Mer Blennius rouxi lives at a depth of 1 to 42m. As an exception among Mediterranean blennies, Bl. rouxi feeds by grazing off the substrate. Algae, sponges and polychaetes (Sedentaria) are the main components of its food (HEYMER and ZANDER, in press). We could not confirm that the colouration, a white body with a conspicuous dark horizontal band, can be regarded as a signal of cleaning activity in statu nascendi. The male male have a spatial territory in which they occupy haptic holes. The female female lead a vagabond life and actively join the male male in their territories during the breeding season. Head nodding is an agonistic behaviour against other female female and has an attractive significance for spawning-motivated female female. The male male threaten with a widely opened mouth (threat yawning). Our data and observations on the ethology of Bl. rouxi are discussed and compared with those known of Bl. sphinx, Bl. incognitus, and Bl. zvonimiri, its nearest relatives.

[The phylogenetic importance of the behavior of the dragonfly Epallage fatime Charp. 1840]. / Der stammesgeschichtliche Aussagewert des Verhaltens der Libelle Epallage fatime Charp. 1840

The behaviour of the dragonfly E. fatime was observed in the field in the Near East, in Turkey and on Rhodos in the summers of 1971 and 1973. A short ethogram of the species is given and its behaviour compared with that of other dragonflies. On this basis its phylogenetic position is discussed.