Laminin, VEGF, and bone matrix protein expression in uroepithelial bone induction--a canine model

Laminin-5 and type I collagen promote adhesion and osteogenic differentiation of animal serum-free expanded human mesenchymal stromal cells

Mesenchymal stromal cells (MSC) are differentiation competent cells and may generate, among others, mature osteoblasts or chondrocytes in vitro and in vivo. Laminin-5 and type I collagen are important components of the extracellular matrix. They are involved in a variety of cellular and extracellular activities including cell attachment and osteogenic differentiation of MSC. MSC were isolated and expanded using media conforming good medical practice (GMP)-regulations for medical products. Cells were characterized according to the defined minimal criteria for multipotent MSC. MTT- and BrdU-assays were performed to evaluate protein-dependent (laminin-5, laminin-1, type I collagen) metabolic activity and proliferation of MSC. MSC-attachment assays were performed using protein-coated culture plates. Osteogenic differentiation of MSC was measured by protein-dependant mineralization and expression of osteogenic marker genes (osteopontin, alkaline phophatase, Runx2) after three, seven and 28 days of differentiation. Marker genes were identified using quantitative reverse-transcription polymerase chain reaction. Expansion of MSC in GMP-conforming media yielded vital cells meeting all minimal criteria for MSC. Attachment assay revealed a favorable binding of MSC to laminin-5 and type I collagen at a protein concentration of 1-5 fmol/µL. Compared to plastic, osteogenic differentiation was significantly increased by laminin-5 after 28 days of culture (P<0.04). No significant differences in gene expression patterns were observed. We conclude that laminin-5 and type I collagen promote attachment, but laminin-1 and laminin-5 promote osteogenic differentiation of MSC. This may influence future clinical applications.

Osteogenesis depending on geometry of porous hydroxyapatite scaffolds

The effect of the configuration of porous cylindrical hydroxyapatite (HA) scaffold and laminin preparation of the scaffold on bone formation was estimated. HA scaffolds with a hollow center of 2 or 4 mm in diameter and those without a hollow center were used. The scaffolds were immersed in laminin solution or in culture medium. Bone marrow cells were obtained from the femora of male Fischer 344 rats. Cell suspension was prepared at 1 x 10(6) cells/mL density. The cells were seeded into HA scaffolds. Each scaffold was implanted in the dorsal subcutis of rats for 4 weeks. Bone formation in scaffolds was observed histologically. The quantity of osteocalcin was measured immunochemically. Many pores containing bone were identified in the laminin-immersed HA scaffold with a hollow center measuring 4 mm in diameter than those without and those with a hollow center measuring 2 mm in diameter. A greater quantity of osteocalcin was detected in the HA scaffold with immersion in laminin than in that without immersion in laminin. However, the results of the immunochemical assay for osteocalcin showed that a hollow center in the scaffold did not contribute to bone formation compared to scaffolds without a hollow center. It is considered that laminin may act as an adhesive for effective cell attachment to the walls of the pores in an HA scaffold.