Search

There is great need for soft biomaterials that match the stiffness of human tissues for tissue engineering and regeneration. Hydrogels are frequently employed for extracellular matrix functionalization and to provide appropriate mechanical cues. It is challenging, however, to achieve structural integrity and retain bioactive molecules in hydrogels for complex tissue formation that may take months to develop. This work aims to investigate mechanical and biochemical characteristics of silk hydrogels for soft tissue engineering, specifically for the nervous system. The stiffness of 1 to 8% silk hydrogels, measured by atomic force microscopy, is 4 to 33 kPa. The structural integrity of silk gels is maintained throughout embryonic chick dorsal root ganglion (cDRG) explant culture over 4 days whereas fibrin and collagen gels decrease in mass over time. Neurite extension of cDRGs cultured on 2 and 4% silk hydrogels exhibit greater growth than softer or stiffer gels. Silk hydrogels release <5% of neurotrophin-3 (NT-3) over 2 weeks and 11-day old gels show maintenance of growth factor bioactivity. Finally, fibronectin- and NT-3-functionalized silk gels elicit increased axonal bundling suggesting their use in bridging nerve injuries. These results support silk hydrogels as soft and sustainable biomaterials for neural tissue engineering. [ABSTRACT FROM AUTHOR]

Abstract: Here we describe a novel small polypeptide expressed in chick embryo and mouse adult tissues referred to as Rolly Protein (Rolp), expressed at the highest levels in tibial cartilage and lung respectively. Investigating its putative role in cartilage differentiation we found that its expression is restricted to proliferative stages consistently with a decreased proliferation rate observed in Rolp-silenced cells. Additional functional studies demonstrate that inhibition of Rolp expression causes a transcription modulation of genes involved in apoptosis. The results here provided strongly suggest an active role of Rolp in the control of cell proliferation and apoptosis. [Copyright &y& Elsevier]

There is increasing interest in developing new in vitro tissue models using typical tissue engineering approaches. This study was designed to (1) develop a novel three-dimensional (3D) in vitro model of bone by seeding murine primary osteoblasts and osteoclast precursors on a resorbable porous ceramic scaffold based on silicon-stabilized tricalcium phosphate (Skelite), and (2) investigate bone cell interactions in a 3D environment mimicking an in vivo condition and compare it to traditional two-dimensional (2D) cultures. Murine primary osteoblasts from C57Bl6/J mice and osteoclast precursors from C57Bl/6-Tg(ACTB-EGFP)1Osb/J mice were co-cultured on 3D Skelite scaffolds and on standard plastic culture dishes. The differentiation of these cells in both culture conditions was compared by histology (hematoxylin-eosin staining and polarized light analysis), immunohistochemistry (collagen type I), and gene expression analysis by real-time PCR for Runt-related transcription factor 2, osterix, osteocalcin, cathepsin K, and tartrate resistant acid phosphatase. To analyze and compare bone turnover in 3D and 2D co-cultures, we evaluated the modulation of RANKL and OPG mRNA expression. We observed an enhancement of osteoblast differentiation in the 3D mineralized environment that in turn promoted earlier osteoclast differentiation. In this paper, we also report that the increased osteoblast differentiation in the 3D model led to a deposition of extracellular matrix that faithfully reflected the morphology of bone tissue.