Engineering of implantable cartilaginous structures from bone marrow-derived mesenchymal stem cells

Fabrication of implantable cartilaginous structures that could be secured in the joint defect could provide an alternative therapeutic approach to prosthetic joint replacement. Herein we explored the possibility of using biodegradable hydrogels in combination with a polyglycolic acid (PGA) scaffold to provide an environment propitious to mesenchymal stem cells (MSCs) chondrogenic differentiation. We examined the influence of type I collagen gel and alginate combined with PGA meshes on the extracellular matrix composition of tissue-engineered transplants. MSCs were isolated from young rabbits, expanded in monolayers, suspended in each hydrogel, and loaded on PGA scaffolds. All constructs (n=48) were cultured in serum-free medium containing transforming growth factor beta-1, under dynamic conditions in specially designed bioreactors for 3-6 weeks. All cell-polymer constructs had a white, shiny aspect, and retained their initial size and shape over the culture period. Their thickness increased substantially over time, and no shrinkage was observed. All specimens developed a hyalin-like extracellular matrix containing glycosaminoglycans (GAGs) and type II collagen, but significant differences were observed among the three different groups. In PGA/MSCs and collagen-PGA/MSCs constructs, the cell growth phase and the chondrogenic differentiation phase of MSCs occurred during the first 3 weeks. In alginate-PGA/MSCs constructs, cells remained round in the hydrogel and cartilage extracellular matrix deposition was delayed. However, at 6 weeks, alginate-PGA/MSCs constructs exhibited higher contents of GAGs and lower contents of type I collagen. These results suggest that the implied time for the transplantation of in vitro engineered constructs depends, among other factors, on the nature of the scaffold envisioned. In this study, we demonstrated that the use of a composite hydrogel-PGA scaffold supported the in vitro growth of implantable cartilaginous structures cultured in a bioreactor system.

Preparation of nano-sized particles from collagen II by a high-voltage electrostatic field system

The pilot study describes a novel method for preparing nano-sized particles from collagen II using a high-voltage electrostatic field system. Observations from transmission electron microscopy showed that, in one of the cases, the nano-sized collagen II particles exhibited good sphericity, and the particles were in the range of 23.3+/-1.7 nm in diameter at the experimental setting of 3 kV cm(-1), for a 3 h treatment period and at 25 degrees C (with a collagen concentration of 0.2 mg ml(-1)). When the treatment temperature increased to 30 degrees C, the collagen II began to lose the tendency to form individually separated spherically shaped nano-particles. Moreover, a fibrous structure of collagen II was formed instead of a nano-particle shape at the temperature of 37 degrees C. This result is probably contributed to by an entropy-driven process that is termed fibrillogenesis, a larger force causing the collagen molecules to self-assemble and then form collagen fibrils. It is interesting to note that this is practically the first attempt to produce nano-particles directly from collagen II solution under the treatment of a high-voltage electrostatic field, together with a set of working parameters for the collagen concentration and low-temperature setting.

Mechanical Properties and Cellular Proliferation of Electrospun Collagen Type II

A suitable technique for articular cartilage repair and replacement is necessitated by inadequacies of current methods. Electrospinning has potential in cartilage repair by producing scaffolds with fiber diameters in the range of native extracellular matrix. Chondrocytes seeded onto such scaffolds may prefer this environment for differentiation and proliferation, thus approaching functional cartilage replacement tissue. Scaffolds of collagen type II were created by an electrospinning technique. Individual scaffold specimens were prepared and evaluated as uncross-linked, cross-linked, or crosslinked/seeded. Uncross-linked scaffolds contained a minimum and average fiber diameter of 70 and 496 nm, respectively, whereas cross-linked scaffolds possessed diameters of 140 nm and 1.46 microm. The average thickness for uncross-linked scaffolds was 0.20 +/- 0.02 mm and 0.52 +/- 0.07 mm for cross-linked scaffolds. Uniaxial tensile tests of uncross-linked scaffolds revealed an average tangent modulus, ultimate tensile strength, and ultimate strain of 172.5 +/- 36.1 MPa, 3.3 +/- 0.3 MPa, and 0.026 +/- 0.005 mm/mm, respectively. Scanning electron microscopy of cross-linked scaffolds cultured with chondrocytes demonstrated the ability of the cells to infiltrate the scaffold surface and interior. Electrospun collagen type II scaffolds produce a suitable environment for chondrocyte growth, which potentially establishes the foundation for the development of articular cartilage repair.