Long-Term Culture of Stem Cells on Phosphate-Based Glass Microspheres: Synergistic Role of Chemical Formulation and 3D Architecture

The Effects of Fucoidan Derived from Sargassum filipendula and Fucus vesiculosus on the Survival and Mineralisation of Osteogenic Progenitors

Osteosarcoma is a bone cancer primarily affecting teenagers. It has a poor prognosis and diminished quality of life after treatment due to chemotherapy side effects, surgical complications and post-surgical osteoporosis risks. The sulphated polysaccharide fucoidan, derived from brown algae, has been a subject of interest for its potential anti-cancer properties and its impact on bone regeneration. This study explores the influence of crude, low-molecular-weight (LMW, 10-50 kDa), medium-molecular-weight (MMW, 50-100 kDa) and high-molecular-weight (HMW, >100 kDa) fractions from Sargassum filipendula, harvested from the Colombian sea coast, as well as crude fucoidan from Fucus vesiculosus, on a specific human osteoprogenitor cell type, human embryonic-derived mesenchymal stem cells. Fourier transform infrared spectroscopy coupled with attenuated total reflection (FTIR-ATR) results showed the highest sulphation levels and lowest uronic acid content in crude extract from F. vesiculosus. There was a dose-dependent drop in focal adhesion formation, proliferation and osteogenic differentiation of cells for all fucoidan types, but the least toxicity was observed for LMW and MMW. Transmission electron microscopy (TEM), JC-1 (5,50,6,60-tetrachloro-1,10,3,30-tetraethylbenzimi-dazolylcarbocyanine iodide) staining and cytochrome c analyses confirmed mitochondrial damage, swollen ER and upregulated autophagy due to fucoidans, with the highest severity in the case of F. vesiculosus fucoidan. Stress-induced apoptosis-like cell death by F. vesiculosus fucoidan and stress-induced necrosis-like cell death by S. filipendula fucoidans were also confirmed. LMW and MMW doses of <200 ng/mL were the least toxic and showed potential osteoinductivity. This research underscores the multifaceted impact of fucoidans on osteoprogenitor cells and highlights the delicate balance between potential therapeutic benefits and the challenges involved in using fucoidans for post-surgery treatments in patients with osteosarcoma.

In vitro immunomodulatory effect of solid versus porous phosphate-based glass microspheres using macrophages

This study aimed to investigate the immunomodulatory effect of two different forms of phosphate-based glass microspheres (solid and porous), on human macrophages. Human THP-1 monocytes were converted to M0 macrophages after being treated with 100 ng/mL phorbol 12-myristate 13-acetate for 48 h. The differentiated cells were analysed for the CD14 marker using flow cytometry. The adhesion, spreading, and viability of M0 macrophages grown directly or indirectly (extracts) at varying concentrations of solid and porous glass microspheres (GMs) were analysed via phase contrast microscopy, confocal microscopy, and XTT assay. The expression of IL-8, IL-1β, IL-6, IL-10, TNF-α, and IL-12p70 cytokines was investigated using flow cytometry. The conversion to M0 macrophages was confirmed by their adherent nature, increased granularity, and CD14 expression. The results showed that both solid and porous GMs or extracts favored the attachment, spreading, and proliferation of macrophages in a comparable manner to cells grown in a normal tissue culture medium. Only the higher concentration of porous GMs (10 mg/mL) changed the morphology of M0 macrophages and increased the expression of IL-1β and IL-8 pro-inflammatory cytokines; this could be related to the fast degradation nature of porous GMs. Of the six cytokines analysed, M0 macrophages grown directly or indirectly with GMs only expressed IL-1β, IL-10, and IL-8. Accordingly, solid microspheres may have advantages as regenerative agents due to their controlled degradation.

Evolution of silicate bioglass particles as porous microspheres with a view towards orthobiologics

Although FDA approved and clinically utilised, research on 45S5 Bioglass® and S53P4 including other bioactive glasses continues in order to advance their applicability for a range of alternate applications. For example, rendering these particles porous would enable incorporation of varying biological payloads (i.e. cells, drugs and growth factors) and making them spherical would enhance their flow properties enabling delivery to target sites via minimally invasive injection procedures. This paper reports on the manufacture of solid (non-porous; SGMS) and highly porous microspheres (PGMS) with large external pores and fully interconnected porosity from bioactive silicate glass formulations (45S5 and S53P4) via a single stage flame spheroidisation process and their physicochemical properties including in vitro biological response. Morphological and physical characterisation of the SGMS and PGMS revealed interconnected porosity up to 65 ± 5%. Mass loss studies comparing between SGMS and PGMS revealed 1.5 times higher mass loss for the PGMS over 28 days. Also, in vitro bioactivity studies using simulated body fluid (SBF) revealed hydroxyapatite (HA) formation at earlier time point for PGMS compared to their SGMS counterparts (i.e day 1 for PGMS and day 3 for SGMS of 45S5). In addition, HA layers were also formed in cell culture media, with the exception of SGMS of 45S5, which revealed CaP formation with a ratio of 1.52-1.78. Direct cell seeding and indirect cell culture studies (via incubation with microsphere degradation products) revealed mouse 3T3 cells were able to grow and undergo osteogenic differentiation in vitro, confirming cytocompatibility of both 45S5 and S53P4 SGMS and PGMS. More importantly and especially for orthobiologic applications, cells were observed to have migrated within the pores of the PGMS. As such, the PGMS developed from these bioactive silicate glasses are highly promising candidate materials for orthobiologics and alternate applications requiring delivery of biologic payloads.