Fibronectin and laminin promote differentiation of human mesenchymal stem cells into insulin producing cells through activating Akt and ERK.

Background: Islet transplantation provides a promising cure for Type 1 diabetes; however it is limited by a shortage of pancreas donors. Bone marrow-derived multipotent mesenchymal stem cells (MSCs) offer renewable cells for generating insulin-producing cells (IPCs).

Methods: We used a four-stage differentiation protocol, containing neuronal differentiation and IPC-conversion stages, and combined with pellet suspension culture to induce IPC differentiation.

Fabrication of vascularized bone grafts of predetermined shape with hydroxyapatite-collagen gel beads and autogenous mesenchymal stem cell composites.

Background: Advances in tissue-engineering techniques have enabled new procedures to be developed for bone regeneration. In this study, for engineering of structural tissues with supporting vascular networks, the authors attempted to produce vascularized tissue-engineered bone grafts using cultured mesenchymal stem cells/hydroxyapatite/collagen gel bead composites and vascular bundle implantation.

Methods: Twenty-four New Zealand White rabbits underwent implantation of ringed polytetrafluoroethylene vascular grafts (1 x 3 cm) in the medial thigh with the femoral vascular bundle passing through.

Type I collagen promotes proliferation and osteogenesis of human mesenchymal stem cells via activation of ERK and Akt pathways.

Biomaterials not only serve as scaffolds for bone regeneration, but may also exhibit inductive capability for bone growth. The goal of this study was to identify the best extracellular matrix protein for enhancing osteogenesis by hMSCs (human mesenchymal stem cells) and to investigate the underlying mechanism. Coating with collagen I, but not fibronectin, laminin, gelatin, and poly-L-lysine, enhanced late cell proliferation and promoted osteogenesis by hMSCs, as evidenced by an increase in Alizarin Red S staining, alkaline phosphatase activity and mRNA levels of Runx2 and osteocalcin.

In vivo angiogenesis effect of porous collagen scaffold with hyaluronic acid oligosaccharides.

Background: Tissue engineering is a promising solution for tissue defect repair. A key problem, however, is how to keep the engineered tissue alive after implantation. The ideal scaffold for tissue engineering would be biocompatible and biodegradable and, more importantly, would exhibit good interaction with endothelial cells to promote angiogenesis.

Apoptosis in chondrogenesis of human mesenchymal stem cells: effect of serum and medium supplements.

Apoptosis is an inevitable process during development and is evident in the formation of articular cartilage and endochondral ossification of growth plate. Mesenchymal stem cells (MSCs) can serve as alternative sources for cell therapy in focal chondral lesions or diffuse osteoarthritis. But there are few, if any, studies investigating apoptosis during chondrogenesis by MSCs.

The effects of fiber size on MG63 cells cultured with collagen based matrices.

The behavior of human osteoblast-like MG63 cells cultured on electrospun collagen fibers of three different sizes (50-200 nm, 200-500 nm, and 500-1000 nm in diameter) were investigated. The growth of MG63 cells on all three electrospun collagen fibers are the same and about 70% higher than those cultured on monomeric collagen and tissue-culture polystyrene (TCPS). The migration speed of MG63 cells, on the other hand, decreased as the diameter of nanofibers increased.

Characterization and osteogenic effects of mesenchymal stem cells on microbeads composed of hydroxyapatite nanoparticles/reconstituted collagen.

Natural bone is comprised of nanosized blade-like crystals of hydroxyapatite grown in close contact with collagen (Col) fibers. Characteristics of artificial bone tissue differ considerably with those of natural ones, mainly from the unusual self-organizing interaction between the apatite crystals and the proteic components. Nanoparticle spheres of hydroxyapatite (n-HA), dispersed in reconstituted fibrous Col, were prepared in three weight ratios of 75:25, 65:35, and 50:50 (n-HA:Col).

Fabrication of pre-determined shape of bone segment with collagen-hydroxyapatite scaffold and autogenous platelet-rich plasma.

Background: Reconstruction of large segment of bony defects is frequently needed in hand surgery. Autogenous bone grafting is considered the standard in management of these bony defects but has limited source of graft material. Collagen and hydroxyapatite have been used as bone-filling materials and are known to serve as the osteoconductive scaffold for bone regeneration.

Development of two alginate-based wound dressings.

Two types of new alginate-based wound dressings, Type-AP and Type-AE, were fabricated by the EDC-activated crosslinking of alginate with Polyethyleneimine and Ethylenediamine, respectively. As compared with the commercial non-woven wound dressing, Kaltostat, both Type-AP and Type-AE dressings had higher degradation temperature, lower calcium content, and a sponge-like macroporous structure. In addition, these two alginate-based dressings had higher mechanical stress (12.

Influences of hyaluronan on type II collagen fibrillogenesis in vitro.

The effect to the kinetics of type II collagen fibrillogenesis with the addition of hyaluronan (HA), (Mw of 1.8x10(6) Da), at various concentrations of HA (0.01, 0.

Microspheres of collagen/beta-TCP with an open network fibrillar structure strengthened by chitosan.

A novel method of preparing collagen/beta-tricalcium phosphate microspheres with chitosan as the mechanical strength enhancer has been developed in this study. The process involved firstly droplet formation by discharging a mixture of collagen, beta-tricalcium phosphates and alginate into an aqueous solution of CaCl(2) by extruding through an air jet-syringe at 4 degrees C. The gel beads thus formed were collected and subsequently coated with chitosan to stabilize the surface of gel bead.

A novel method of encapsulating and cultivating adherent mammalian cells within collagen microcarriers.

A novel method of preparing collagen microcarriers was developed and used to entrap adherent cells for cell culturing. This new technique involved seeding of cells in micro gel beads comprised of collagen fibrils dispersed in alginate. The gel beads were washed with phosphate buffered saline (PBS) to remove alginate and the resulting microspheres, about 300-500 microm in diameter, contained evenly distributed collagen fibrils which provided a 3D biomimetic environment for cell growth.

Growth of mesenchymal stem cells on electrospun type I collagen nanofibers.

We reconstituted type I collagen nanofibers prepared by electrospin technology and examined the morphology, growth, adhesion, cell motility, and osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (MSCs) on three nano-sized diameters (50-200, 200-500, and 500-1,000 nm). Results from scanning electron microscopy showed that cells on the nanofibers had a more polygonal and flattened cell morphology. MTS (3-[4,5-dimethythiazol-2-yl]-5-[3-carboxy-methoxyphenyl]-2-[4-sul-fophenyl]-2H-tetrazolium compound) assay demonstrated that the MSCs grown on 500-1,000-nm nanofibers had significantly higher cell viability than the tissue culture polystyrene control.

Three-dimensional collagen fiber remodeling by mesenchymal stem cells requires the integrin-matrix interaction.

Tissue engineering aiming to repair or regenerate damaged tissues necessitates fabricating three-dimensional biomaterial scaffolds with controlled porosity for delivering cells. To facilitate cell distribution, a strategy using stem cell-based fabrication of biomaterials was tested in type II collagen fibers. Human mesenchymal stem cells when delivered in type II collagen assembled and reorganized these matrices and differentiated into spherical chondrocytes with the synthesis of cartilage proteins.

The internalized CdSe/ZnS quantum dots impair the chondrogenesis of bone marrow mesenchymal stem cells.

Mesenchymal stem cells (MSCs) are capable of differentiating into multiple cell lineages and are useful for therapeutic applications. Labeling the MSCs with fluorescent probes is beneficial in tracing the fate of MSCs after implantation. We have introduced the CdSe/ZnS quantum dots (QDs) into the human bone marrow MSCs and examined the effects of QDs on the proliferation and chondrogenesis of the cells.

The inhibition of osteogenesis with human bone marrow mesenchymal stem cells by CdSe/ZnS quantum dot labels.

CdSe/ZnS quantum dots (QDs) have recently been used as cell tracers for long term imaging of live cells. A number of studies indicate that introduction of quantum dots to cells have no apparent deleterious effects on the morphology or growth of cells. In the present study, the human bone marrow mesenchymal stem cells (hBMSCs) were used as a model to examine the effects of QDs on the growth and osteogenic differentiation of the cells.

Influence of alginate on type II collagen fibrillogenesis.

Collagen II is the majority of extracellular matrix components in articular cartilage, which with the major functions of preventing expansion of the tissue and distributing the load of body weight. To obtain man-made ECM, the reconstitution of collagen could be conducted in the presence of negatively charged polysaccharide, such as alginate. Alginate is an anionic polysaccharide capable of eversible gelated in calcium ion solution to prepare different shapes of biomaterials.

An in vivo study of a bone grafting material consisting of hydroxyapatite and reconstituted collagen.

This study aims to evaluate the performance of our recently developed microspheres of hydroxyapatite/reconstituted collagen as a bone grafting material. The microspheres were fabricated into a circular disc and implanted in a pre-drilled hole in a rat's calvaria. The bone tissue had regenerated and grown into the disc bone graft 4 weeks following implantation.

A new anti-adhesion film synthesized from polygalacturonic acid with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide crosslinker.

The most commonly used anti-adhesion device for separation and isolation of wounded tissues after surgery is the polymeric film. In this study, a new anti-adhesion membrane based on polygalacturonic acid (PGA) has been synthesized, and its biocompatibility and anti-adhesion capabilities evaluated. The PGA film was reacted with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) to obtain a cross-linked PGA film with an 86% gel content and a 47% water content when immersed in aqueous solution.

Microencapsulation of parathyroid tissue with photosensitive poly(L-lysine) and short chain alginate-co-MPEG.

Human parathyroid glands were encapsulated using the alginate-PLL system in this study. In order to improve the mechanical strength and the biocompatibility, the microcapsules were fabricated with a three-layer structure that consisted of alginate/photosensitive poly(L-lysine)/short chain alginate-co-MPEG. These modified microcapsules were used for encapsulating human parathyroid tissue.

Studies on the microspheres comprised of reconstituted collagen and hydroxyapatite.

Microspheres comprised of hydroxyapatite particles, dispersed in reconstituted fibrous collagen, were prepared and characterized. The hydroxyapatite particles distributed evenly throughout the collagen matrix of the microsphere. Diameters of the reconstituted collagen fibers ranged from 30 to 90 nm, and exhibited a regular banding pattern with cross-striation of 50-60 nm under transmission electron microscope, suggesting that the reconstitution of collagen was not hindered by the hydroxyapatite particulates.

Osteogenic enrichment of bone-marrow stromal cells with the use of flow chamber and type I collagen-coated surface.

The stromal cells of the bone marrow are able to attach to the surface and differentiate into cells with bone-forming capability when stimulated with osteogenic supplements. In this study, we have employed a flow-chamber device containing a collagen-coated surface to enrich the potential osteoprogenitor cells from bone marrow stromal cells (BMSCs). The population of the cells attached to the collagen-coated substratum is about twice that attached to the uncoated surface.

Collagen-hydroxyapatite/tricalcium phosphate microspheres as a delivery system for recombinant human transforming growth factor-beta 1.

The purpose of this study is to evaluate the carrier capability of collagen-hydroxyapatite/tricalcium phosphate (Col-HA/TCP) microspheres to the rhTGF-beta 1 (recombinant human transforming growth factor-beta 1). After anesthesia, a bone defect (7.0 mm in diameter and 10.

Collagen as an immobilization vehicle for bone marrow stromal cells enriched with osteogenic potential.

The bone marrow contains mesenchymal cells that can be divided into two categories: cells of hemopoietic lineage and stromal cells. The stromal cells are adhesive to the surface of culture dish, and could be differentiated into cells with bone-forming capability when stimulated with osteogenic supplements. In this study, we have employed collagen to immobilize cells with osteogenic potential from bone marrow.

Collagen-hydroxyapatite microspheres as carriers for bone morphogenic protein-4.

The purpose of the current study is to evaluate the carrier capability of collagen-hydroxyapatite microspheres to the bone morphogenic proteins (BMP). After anesthesia, a bone defect (6.0 mm in diameter and 10.