Novel Vanadium-Loaded Ordered Collagen Scaffold Promotes Osteochondral Differentiation of Bone Marrow Progenitor Cells.

Bone and cartilage regeneration can be improved by designing a functionalized biomaterial that includes bioactive drugs in a biocompatible and biodegradable scaffold. Based on our previous studies, we designed a vanadium-loaded collagen scaffold for osteochondral tissue engineering. Collagen-vanadium loaded scaffolds were characterized by SEM, FTIR, and permeability studies. Rat bone marrow progenitor cells were plated on collagen or vanadium-loaded membranes to evaluate differences in cell attachment, growth and osteogenic or chondrocytic differentiation. The potential cytotoxicity of the scaffolds was assessed by the MTT assay and by evaluation of morphological changes in cultured RAW 264.7 macrophages. Our results show that loading of VOAsc did not alter the grooved ordered structure of the collagen membrane although it increased membrane permeability, suggesting a more open structure. The VOAsc was released to the media, suggesting diffusion-controlled drug release. Vanadium-loaded membranes proved to be a better substratum than C0 for all evaluated aspects of BMPC biocompatibility (adhesion, growth, and osteoblastic and chondrocytic differentiation). In addition, there was no detectable effect of collagen or vanadium-loaded scaffolds on macrophage viability or cytotoxicity. Based on these findings, we have developed a new ordered collagen scaffold loaded with VOAsc that shows potential for osteochondral tissue engineering.

Islet neogenesis associated protein (ingap): structural and dynamical properties of its active pentadecapeptide.

We have studied the structural and dynamical properties of the biologically active pentadecapeptide of the islet neogenesis associated protein (INGAP-PP) and of two other pentadecapeptides with the same amino acid composition but randomly scrambled primary sequences, using molecular dynamic simulations. Our data demonstrates that whilst the peptides with scrambled sequences show no definite prevalent structure in solution, INGAP-PP maintains a notably stable tertiary fold, namely, a conformer with a central beta-sheet and closed C-terminal. Such structure resembles the one corresponding to the amino acid sequence of human pancreatitis associated protein-1 (PAP-1), which presents 85% sequence homology with INGAP. These results could reasonably explain why the two scrambled sequences tested showed no biological activity, while INGAP-PP significantly increases beta-cells function and mass both in vitro and in vivo conditions. The capability of INGAP-PP to temporarily adopt other closely related conformations offers also a plausible explanation for the 50 fold experimental difference in potency between the active pentadecapeptide and the whole protein. They also suggest that the C-terminal region of INGAP-PP may plausibly be the locus for its interaction with the cell receptor. Consequently, the knowledge gathered through our data can help to obtain more potent INGAP-PP analogs, suitable for the prevention and treatment of diabetes.

Collagen stability, hydration and native state.

Molecular dynamics simulations of a collagen-like peptide (Pro-Hyp-Gly)4-Pro-Hyp-Ala-(Pro-Hyp-Gly)5 have been done in order to study the contribution of the hydration structure on keeping the native structure of collagen. The simulation shows that the absence of water produces a distortion on the molecular conformation and an increase in the number of intra-molecular hydrogen bonds. This is in agreement with previous experimental results showing the stiffness of collagen under severe drying and its increase in the thermal stability. This dehydrated material does not keep, however, the native structure.