Osteogenic differentiation of human mesenchymal stem cells through alginate-graft-poly(ethylene glycol) microsphere-mediated intracellular growth factor delivery

Abstract

The intracellular delivery of growth factors increases opportunities for controlling cell behavior and maintaining tissue homeostasis. Recently, VEGFA was reported to enhance osteogenic differentiation of mesenchymal stem cells (MSCs) through an intracrine mechanism, suggesting a new strategy to promote bone tissue formation in osteoporotic patients. The goal of this study was to design and fabricate ligand-conjugated alginate-graft-poly(ethylene glycol) microspheres for intracellular delivery and release of VEGFA in primary human MSCs to enhance osteogenic differentiation as a potential therapeutic. Three types of microspheres were synthesized and characterized by scanning electron microscopy, in vitro drug release kinetics, MSC uptake and internalization: alginate alone (Alg), alginate-graft-poly(ethylene glycol) (Algg-PEG) and alginategraft-poly(ethylene glycol)-S-S-arginine-glycine-aspartic acid (Alg-g-RGD). Each of the different microsphere formulations successfully transported bioactive VEGFA into primary human MSCs within 48 h of culture, and significantly enhanced osteogenic differentiation compared to control treatments with empty microspheres (intracellular control) or non-encapsulated VEGFA (extracellular control). Adipogenic differentiation was not affected by the presence of VEGFA intracellularly or extracellularly. These results demonstrating the internalization of alginate-based microspheres and intracellular delivery of VEGFA support the efficacy of using this drug delivery and intracrine mechanism to control the fate of human MSCs and enhance osteogenic differentiation.

Dual-Cross-Linked Methacrylated Alginate Sub-Microspheres for Intracellular Chemotherapeutic Delivery

“…A549s cultured with no sub-microspheres, and cells cultured with non-fluorescent sub-microspheres, were prepared and analyzed as controls. 22 …”

“…24 Through the formation of a water/oil emulsion and subsequent exposure to calcium ions, alginate particles within the micrometer – nanometer size scale can be generated, and are often referred to as ionically crosslinked alginate particles. 20, 22, 25 …”

“…28 Dual-crosslinked sub-microspheres were generated with the subsequent addition of calcium chloride. 22 To evaluate the efficiency of internalization and the bioactivity of DOX-loaded Alg-MA sub-microspheres, human lung epithelial carcinoma cells (A549s) were utilized as a model system. We hypothesized the dual-crosslinking would result in a tighter hydrogel network for more efficient intracellular DOX delivery (Figure 1).…”

Preparation and characterization of vanillin-crosslinked chitosan therapeutic bioactive microcarriers

“…The cells exhibiting the desired stretched morphology on VCM suggests the presence of a conducive environment for cell anchorage and growth [47]. This combined function of delivering drug along with potential delivery of cells can be considered ideal to achieve native-tissue equivalents by ex vivo culturing, as well as to help complete tissue formation after implantation [48].…”

Fabrication and characterization of carboxymethyl chitosan/poly(vinyl alcohol) hydrogels containing alginate microspheres for protein delivery

“…Three kinds of alginate-based microspheres had been prepared and used for intracellular delivery of vascular endothelial growth factor A (VEGFA); results showed that each of the different microsphere formulations successfully transported bioactive VEGFA into primary human mesenchymal stem cells (MSCs) within 48 h of culture and significantly enhanced osteogenic differentiation. 22 In situ formed gels from alginate or its composites with pluronic or hydroxypropyl methylcellulose (HPMC) loaded with pilocarpine or gatifloxacin have shown improved drug bioavailability. 23,24 Formulations such as microspheres and hydrogels have been used for localized or targeted drug delivery in a sustained manner.…”