Intracellular release of 17-β estradiol from cationic polyamidoamine dendrimer surface-modified poly (lactic-co-glycolic acid) microparticles improves osteogenic differentiation of human mesenchymal stromal cells

Abstract

Human bone marrow mesenchymal stromal cells (MSCs) are considered a potential cell source for MSC-based bone regeneration, but improvements in the proliferation and differentiation capacity of MSCs are necessary for practical applications. Estrogen effectively improves MSC capabilities and has strong potential as a regulator of MSCs. The aim of this study was to develop a delivery system that provides intracellular release of estrogen and test its ability to improve osteogenic differentiation of MSCs. Biodegradable poly (lactic-co-glycolic acid) (PLGA) microparticles were developed that entrap 17-β estradiol (E2) and provide intracellular release of E2. The results show that we can prepare PLGA particles with efficient loading of E2 and maintain release of E2 up to 7 days. Surface modifying E2-loaded PLGA particles with cationic polyamidoamine dendrimers enabled increased uptake by human MSCs. Human MSC uptake of the E2-loaded PLGA particles significantly upregulates osteogenic differentiation markers of alkaline phosphatase and osteocalcin. In conclusion, cationic-modified PLGA particles can serve as a tool for intracellular delivery of estrogen to effectively execute estrogen regulation of MSCs. This approach has the potential to improve the osteogenic capabilities of MSCs and to develop appropriate environments of implantation for MSC-based bone tissue engineering.

FIG. 1.

Microphotographs (A) and in vitro release profile (B) of E2-loaded PLGA particles with cationic charge modification (formulation 4 from Table 3). PLGA, poly (lactic-co-glycolic acid); E2, 17-β estradiol.

FIG. 2.

Confocal microscopic images of human MSCs after 1 and 24 h incubation with rhodamine-loaded PLGA particles (formulation 4 from Table 3) observed by overlaying images obtained by Zeiss-701. (A) DAPI staining of nucleus; (B) rhodamine staining for PLGA particles; (C) LysoTracker Green staining for Lysozymes; (D) Merged images. The control was cells incubated with no particles. Scale bar = 20 μm. MSC, mesenchymal stromal cell. Color images available online at www.liebertonline.com/ten.

FIG. 3.

Osteogenic differentiation markers and estrogen receptor of MSCs improved by uptake of E2-loaded PLGA particles (formulation 4 from Table 3). Fold changes of ALP (A), Cbfa-1 (B) and estrogen receptor-α (ESR1) (C) of human MSCs using real-time polymerase chain reaction. *p < 0.05 vs osteogenic-supplemented medium (OS). Target gene expression is normalized to GAPDH expression. ALP, alkaline phosphatase; Cbfa-1, core binding factor alpha 1.