Background: Mesenchymal stromal cells (MSCs) are multipotent progenitor cells used in several cell therapies. MSCs are characterized by the expression of CD73, CD90, and CD105 cell markers, and the absence of CD34, CD45, CD11a, CD19, and HLA-DR cell markers. CD90 is a glycoprotein present in the MSC membranes and also in adult cells and cancer stem cells. The role of CD90 in MSCs remains unknown. Here, we sought to analyse the role that CD90 plays in the characteristic properties of in vitro expanded human MSCs. Methods: We investigated the function of CD90 with regard to morphology, proliferation rate, suppression of T-cell proliferation, and osteogenic/adipogenic differentiation of MSCs by reducing the expression of this marker using CD90-target small hairpin RNA lentiviral vectors. Results: The present study shows that a reduction in CD90 expression enhances the osteogenic and adipogenic differentiation of MSCs in vitro and, unexpectedly, causes a decrease in CD44 and CD166 expression. Conclusion: Our study suggests that CD90 controls the differentiation of MSCs by acting as an obstacle in the pathway of differentiation commitment. This may be overcome in the presence of the correct differentiation stimuli, supporting the idea that CD90 level manipulation may lead to more efficient differentiation rates in vitro.

Photodynamic therapy (PDT) combines light, molecular oxygen and a photosensitizer to induce oxidative stress in target cells. Certain hydrophobic photosensitizers, such as aluminium-phthalocyanine chloride (AlPc), have significant potential for antitumor PDT applications. However, hydrophobic molecules often require drug-delivery systems, such as nanostructures, to improve their pharmacokinetic properties and to prevent aggregation, which has a quenching effect on the photoemission properties in aqueous media. As a result, this work aims to develop and test the efficacy of an AlPc in the form of a nanoemulsion to enable its use in anticancer PDT. The nanoemulsion was developed using castor oil and Cremophor ELP®, and a monodisperse population of nanodroplets with a hydrodynamic diameter of approximately 25 nm was obtained. While free AlPc failed to show significant activity against human breast adenocarcinoma MCF-7 cells in an in vitro PDT assay, the AlPc in the nanoemulsion showed intense photodynamic activity. Photoactivated AlPc exhibited a 50 % cytotoxicity concentration (CC50) of 6.0 nM when applied to MCF-7 cell monolayers and exerted a powerful cytotoxic effect on MCF-7 cell spheroids. Through the use of spontaneous emulsification, a stable AlPc nanoemulsion was developed that exhibits strong in vitro photodynamic activity on cancer cells.

Photodynamic therapy is generally considered to be safer than conventional anticancer therapies, and it is effective against different kinds of cancer. However, its clinical application has been significantly limited by the hydrophobicity of photosensitizers. In this work, a system composed of the hydrophobic photosensitizer aluminum–phthalocyanine chloride (AlPc) associated with water dispersible poly(methyl vinyl ether-co-maleic anhydride) nanoparticles is described. AlPc was associated with nanoparticles produced by a method of solvent displacement. This system was analyzed for its physicochemical characteristics, and for its photodynamic activity in vitro in cancerous (murine mammary carcinoma cell lineage 4T1, and human mammary adenocarcinoma cells MCF-7) and noncancerous (murine fibroblast cell lineage NIH/3T3, and human mammary epithelial cell lineage MCF-10A) cell lines. Cell viability and the elicited mechanisms of cell death were evaluated after the application of photodynamic therapy. This system showed improved photophysical and photochemical properties in aqueous media in comparison to the free photosensitizer, and it was effective against cancerous cells in vitro.

Perspectives on the application of nanotechnology in photodynamic therapy for the treatment of melanoma