The Marine Sponge-Derived Inorganic Polymers, Biosilica and Polyphosphate, as Morphogenetically Active Matrices/Scaffolds for the Differentiation of Human Multipotent Stromal Cells: Potential Application in 3D Printing and Distraction Osteogenesis

Abstract

The two marine inorganic polymers, biosilica (BS), enzymatically synthesized from ortho-silicate, and polyphosphate (polyP), a likewise enzymatically synthesized polymer consisting of 10 to >100 phosphate residues linked by high-energy phosphoanhydride bonds, have previously been shown to display a morphogenetic effect on osteoblasts. In the present study, the effect of these polymers on the differential differentiation of human multipotent stromal cells (hMSC), mesenchymal stem cells, that had been encapsulated into beads of the biocompatible plant polymer alginate, was studied. The differentiation of the hMSCs in the alginate beads was directed either to the osteogenic cell lineage by exposure to an osteogenic medium (mineralization activation cocktail; differentiation into osteoblasts) or to the chondrogenic cell lineage by incubating in chondrocyte differentiation medium (triggering chondrocyte maturation). Both biosilica and polyP, applied as Ca2+ salts, were found to induce an increased mineralization in osteogenic cells; these inorganic polymers display also morphogenetic potential. The effects were substantiated by gene expression studies, which revealed that biosilica and polyP strongly and significantly increase the expression of bone morphogenetic protein 2 (BMP-2) and alkaline phosphatase (ALP) in osteogenic cells, which was significantly more pronounced in osteogenic versus chondrogenic cells. A differential effect of the two polymers was seen on the expression of the two collagen types, I and II. While collagen Type I is highly expressed in osteogenic cells, but not in chondrogenic cells after exposure to biosilica or polyP, the upregulation of the steady-state level of collagen Type II transcripts in chondrogenic cells is comparably stronger than in osteogenic cells. It is concluded that the two polymers, biosilica and polyP, are morphogenetically active additives for the otherwise biologically inert alginate polymer. It is proposed that alginate, supplemented with polyP and/or biosilica, is a suitable biomaterial that promotes the growth and differentiation of hMSCs and might be beneficial for application in 3D tissue printing of hMSCs and for the delivery of hMSCs in fractures, surgically created during distraction osteogenesis.

Ultrastructural changes during osteogenic differentiation in mesenchymal stromal cells cultured in alginate hydrogel

“…Thus in our experiment, cells did not develop multicellular clusters, typical for osteogenic differentiation of cellular monolayer as observed by us and others [1, 22, 23], but were evenly dispersed. We decided to immobilize cells at low concentration to avoid the cell clustering process, so we could analyze the osteogenic differentiation of single cells.…”

Proliferation and differentiation of mesenchymal stem cells on scaffolds containing chitosan, calcium polyphosphate and pigeonite for bone tissue engineering

“…6,[34][35][36] PolyP-mediated modulation of osteoblast-specific gene expression has been studied in MC3T3E1, SaOS2 and MSCs. 20,34,37,38 To the best of our knowledge, there were no reports available to support the role of Pg and its composite scaffolds in bone formation. In this study, we developed CS-based scaffolds and tested the components, CaPP and Pg particles, for their ability to promote bone formation in vitro and in vivo.…”

Polyphosphate: A Morphogenetically Active Implant Material Serving as Metabolic Fuel for Bone Regeneration

“…). In addition to those studies with polyP in the nanoparticle application form, it has been demonstrated that Na‐polyP, complexed with Ca 2+ in solution, causes an osteogenic differentiation of human multipotent stromal cells as well as an expression of the genes encoding for BMP‐2 and collagen‐I …”