Ordered collagen membranes: production and characterization

Synergistic effects of nanoattapulgite and hydroxyapatite on vascularization and bone formation in a rabbit tibia bone defect model

Hydroxyapatite (HA) is a promising scaffold material for the treatment of bone defects. However, the lack of angiogenic properties and undesirable mechanical properties (such as fragility) limits the application of HA. Nanoattapulgite (ATP) is a nature-derived clay mineral and has been proven to be a promising bioactive material for bone regeneration due to its ability to induce osteogenesis. In this study, polyvinyl alcohol/collagen/ATP/HA (PVA/COL/ATP/HA) scaffolds were printed. Mouse bone marrow mesenchymal stem/stromal cells (BMSCs) and human umbilical vein endothelial cells (HUVECs) were used in vitro to assess the biocompatibility and the osteogenesis and vascularization induction potentials of the scaffolds. Subsequently, in vivo micro-CT and histological staining were carried out to evaluate new bone formation in a rabbit tibial defect model. The in vitro results showed that the incorporation of ATP increased the printing fidelity and mechanical properties, with values of compressive strengths up to 200% over raw PC-H scaffolds. Simultaneously, the expression levels of osteogenic-related genes and vascularization-related genes were significantly increased after the incorporation of ATP. The in vivo results showed that the PVA/COL/ATP/HA scaffolds exhibited synergistic effects on promoting vascularization and bone formation. The combination of ATP and HA provides a promising strategy for vascularized bone tissue engineering.

Collagen, polycaprolactone and attapulgite composite scaffolds for in vivo bone repair in rabbit models

Although numerous materials have been explored as bone scaffolds, many of them are limited by their low osteoconductivity and high biodegradability. Therefore, new materials are desired to induce bone cell proliferation and facilitate bone formation. Attapulgite (ATP) is a hydrated silicate that exists in nature as a fibrillar clay mineral and is well known for its large specific surface area, high viscosity, and high absorption capacity, and therefore has the potential to be a new type of bone repair material due to its unique physicochemical properties. In this study, composite scaffolds composed of collagen/polycaprolactone/attapulgite (CPA) or collagen/polycaprolactone (CP) were fabricated through a salt-leaching method. The morphology, composition, microstructure, physical, and mechanical characteristics of the CPA and CP scaffolds were assessed. Cells from the mouse multipotent mesenchymal precursor cell line (D1 cells) were cocultured with the scaffolds, and cell adhesion, proliferation, and gene expression on the CPA and CP scaffolds were analyzed. Adult rabbits with radius defects were used to evaluate the performance of these scaffolds in repairing bone defects over 4-12 weeks. The experimental results showed that the cells demonstrated excellent attachment ability on the CPA scaffolds, as well as remarkable upregulation of the levels of osteoblastic markers such as Runx2, Osterix, collagen 1, osteopontin, and osteocalcin. Furthermore, results from radiography, micro-computed tomography, histological and immunohistochemical analysis demonstrated that abundant new bones were formed on the CPA scaffolds. Ultimately, these results demonstrated that CPA composite scaffolds show excellent potential in bone tissue engineering applications, with the capacity to be used as effective bone regeneration and repair scaffolds in clinical applications.

Use of a Collagen Membrane to Enhance the Survival of Primary Intestinal Epithelial Cells

Intestinal epithelial cell culture is important for biological, functional, and immunological studies. Since enterocytes have a short in vivo life span due to anoikis, we aimed to establish a novel and reproducible method to prolong the survival of mouse and human cells. Cells were isolated following a standard procedure, and cultured on ordered-cow's collagen membranes. A prolonged cell life span was achieved; cells covered the complete surface of bio-membranes and showed a classical enterocyte morphology with high expression of enzymes supporting the possibility of cryopreservation. Apoptosis was dramatically reduced and cultured enterocytes expressed cytokeratin and LGR5 (low frequency). Cells exposed to LPS or flagellin showed the induction of TLR4 and TLR5 expression and a functional phenotype upon exposure to the probiotic Bifidobacterium bifidum or the pathogenic Clostridium difficile. The secretion of the homeostatic (IL-25 and TSLP), inhibitory (IL-10 and TGF-β), or pro-inflammatory mediators (IL-1β and TNF) were induced. In conclusion, this novel protocol using cow's collagen-ordered membrane provides a simple and reproducible method to maintain intestinal epithelial cells functional for cell-microorganism interaction studies and stem cell expansion. J. Cell. Physiol. 232: 2489-2496, 2017. © 2016 Wiley Periodicals, Inc.

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.