Induction of Human Osteoprogenitor Chemotaxis, Proliferation, Differentiation, and Bone Formation by Osteoblast Stimulating Factor-1/Pleiotrophin: Osteoconductive Biomimetic Scaffolds for Tissue Engineering

Abstract

The process of bone growth, regeneration, and remodeling is mediated, in part, by the immediate cell-matrix environment. Osteoblast stimulating factor-1 (OSF-1), more commonly known as pleiotrophin (PTN), is an extracellular matrix-associated protein, present in matrices, which act as targets for the deposition of new bone. However, the actions of PTN on human bone progenitor cells remain unknown. We examined the effects of PTN on primary human bone marrow stromal cells chemotaxis, differentiation, and colony formation (colony forming unit-fibroblastic) in vitro, and in particular, growth and differentiation on three-dimensional biodegradable porous scaffolds adsorbed with PTN in vivo. Primary human bone marrow cells were cultured on tissue culture plastic or poly(DL-lactic acid-co-glycolic acid) (PLGA; 75:25) porous scaffolds with or without addition of recombinant human PTN (1 pg-50 ng/ml) in basal and osteogenic conditions. Negligible cellular growth was observed on PLGA scaffold alone, generated using a super-critical fluid mixing method. PTN (50 g/ml) was chemotactic to human osteoprogenitors and stimulated total colony formation, alkaline phosphatase-positive colony formation, and alkaline phosphatase-specific activity at concentrations as low as 10 pg/ml compared with control cultures. The effects were time-dependent. On three-dimensional scaffolds adsorbed with PTN, alkaline phosphatase activity, type I collagen formation, and synthesis of cbfa-1, osteocalcin, and PTN were observed by immunocytochemistry and PTN expression by in situ hybridization. PTN-adsorbed constructs showed morphologic evidence of new bone matrix and cartilage formation after subcutaneous implantation as well as within diffusion chambers implanted into athymic mice. In summary, PTN has the ability to promote adhesion, migration, expansion, and differentiation of human osteoprogenitor cells, and these results indicate the potential to develop protocols for de novo bone formation for skeletal repair that exploit cell-matrix interactions. (J Bone Miner Res 2003;18:47-57)

Proximal and Total Humerus Reconstruction With the Use of an Aortograft Mesh

“…Several studies have focused on the proximal femur to try to understand the complex relationship of tendon-bone interfaces [16,27,33]. Osteoconductive scaffolds [53], metallic anchors for soft tissues [20], predetermined suture sites embedded in the metallic prostheses [50], and coating of the prostheses with novel materials [14,16,45], have been described to promote soft tissue ingrowth and improve function after limb salvage with endoprostheses. All of the surgical options for proximal humerus reconstruction have been associated with instability [25], recurrent dislocation [25,38], and overall poor function [36,38].…”

Increased trabecular bone formation in mice lacking the growth factor midkine

“…In fact, the three transgenic mouse models overexpressing Ptn all display a higher bone mineral density, which is in line with in vitro experiments demonstrating that Ptn promotes migration, differentiation, and function of osteoblasts. (21)(22)(23)(44)(45)(46) In addition, there is recent evidence that these effects are also of physiologic relevance because low bone formation and osteopenia have been described in mice lacking Ptn. (47) Given the fact that our own analysis of Ptn-deficient mice did not reveal such a phenotype compared with wild-type littermates on a mixed genetic background, it appears that the backcrossing of the Ptn deficiency into a 129S2/SV genetic background is primarily responsible for the discrepancies between the two publications.…”

Effects of arachidonic acid and docosahexaenoic acid on differentiation and mineralization of MC3T3‐E1 osteoblast‐like cells

“…After 14 days, with medium changes every 3 days, formation of mineralizing plaques was visualized by a modified von Kossa staining technique for phosphate (black) on fixed cell layers. 40,41 Cells were rinsed three times in 0.9% NaCl solution (pH 7.2) and fixed in 4% (v/v) paraformaldehyde in 0.9% (w/v) NaCl solution at room temperature for 10 min. Cells were then rinsed three times in deionized distilled water (ddH 2 O), incubated with 3% (w/v) AgNO 3 in the dark for 30 min, and exposed to ultraviolet light (254 nm) for 30 min.…”