Effects of Culture Substrate Made of Poly(N-isopropylacrylamide-co-acrylic acid) Microgels on Osteogenic Differentiation of Mesenchymal Stem Cells

Abstract

Poly(N-isopropylacrylamide) (PNIPAM)-based polymers and gels are widely known and studied for their thermoresponsive property. In the biomaterials category, they are regarded as a potential cell culture substrate, not only because of their biocompatibility, but also their special character of allowing controlled detachment of cells via temperature stimulus. Previous research about PNIPAM-based substrates mostly concentrated on their effects in cell adhesion and proliferation. In this study, however, we investigate the influence of the PNIPAM-based substrate on the differentiation capacity of stem cells. Especially, we choose P(NIPAM-AA) microgels as a culture dish coating and mesenchymal stem cells (MSCs) are cultured on top of the microgels. Interestingly, we find that the morphology of MSCs changes remarkably on a microgel-coated surface, from the original spindle form to a more stretched and elongated cell shape. Accompanied by the alternation in morphology, the expression of several osteogenesis-related genes is elevated even without inducing factors. In the presence of full osteogenic medium, MSCs on a microgel substrate show an enhancement in the expression level of osteopontin and alizarin red staining signals, indicating the physical property of substrate has a direct effect on MSCs differentiation.

Dynamic adhesive environment alters the differentiation potential of young and ageing mesenchymal stem cells

“…1A). For this time the cells developed an extended and flattened fibroblast-like morphology which is in accordance with other studies utilizing PNIPAM microgels [49]. Fig.…”

“…The use of PNIPAM for culturing stem cells has also been previously explored: Shi et al [19] studied the proliferation and multi-differentiation potentials of human mesenchymal stem cells (MSCs) on thermo-responsive PNIPAM grafted PDMS surface showing that the proliferation is not significantly different from that on a surface coated with gelatin. They demonstrated however that PNIPAM-grafted surface was favorable for the osteogenic differentiation of MSCs, an effect confirmed in a recent investigation utilizing PNIPAM microgels [49] although without using the thermos-responsive property of the polymer for cell harvesting. In the biomaterials field, PNIPAM is regarded as potential cell culture substrata not only because of its biocompatibility, but also due to its special property of allowing controlled detachment of cells [49].…”

“…They demonstrated however that PNIPAM-grafted surface was favorable for the osteogenic differentiation of MSCs, an effect confirmed in a recent investigation utilizing PNIPAM microgels [49] although without using the thermos-responsive property of the polymer for cell harvesting. In the biomaterials field, PNIPAM is regarded as potential cell culture substrata not only because of its biocompatibility, but also due to its special property of allowing controlled detachment of cells [49]. Zhang et al [20] described a number of chemically defined thermo-responsive hydrogels as substrata for long-term culture of human embryonic stem cells and evaluated 2-(dimethylamino)ethyl acrylate to be strongly in favor.…”

“…However, in both early and late passage groups, first, cycled during the differentiation and second, before it (see 1st vs. 3rd and 2nd vs 4th columns respectively) we found significantly less ALP activity when ADSCs were cultured under dynamic adhesive conditions (p b 0.05). It has to be admitted here that the observed inhibition has nothing to do with the properties of the PNIPAM, shown to even promote the osteogenic differentiation of stem cells [19,49], but is direct result from the thermo-cycling. In the late p 14 group (2nd vs 4th columns) the ALP activity was also reduced in the control samples (p b 0.05) presumably due to an altered functionality of ADSCs from the ageing.…”

Ultralow Self-Cross-Linked Poly(N-isopropylacrylamide) Microgels Prepared by Solvent Exchange

“…When the aqueous temperature is above the VPTT, the microgels rapidly shrink and thus release water and internal active matters . This property helps PNIPAm microgels to be widely used in biosensors, − biocatalysis, , cell engineering, − and drug delivery systems. − …”