Nanoplastic impact on bone microenvironment: A snapshot from murine bone cells

Our world is made of plastic. Plastic waste deeply affects our health entering the food chain. The degradation and/or fragmentation of plastics due to weathering processes result in the generation of nanoplastics (NPs). Only a few studies tested NPs effects on human health. NP toxic actions are, in part, mediated by oxidative stress (OS) that, among its effects, affects bone remodeling. This study aimed to assess if NPs influence skeleton remodeling through OS. Murine bone cell cultures (MC3T3-E1 preosteoblasts, MLOY4 osteocyte-like cells, and RAW264.7 pre-osteoclasts) were used to test the NPs detrimental effects on bone cells. NPs affect cell viability and induce ROS production and apoptosis (by caspase 3/7 activation) in pre-osteoblasts, osteocytes, and pre-osteoclasts. NPs impair the migration capability of pre-osteoblasts and potentiate the osteoclastogenesis of preosteoclasts. NPs affected the expression of genes related to inflammatory and osteoblastogenic pathways in pre-osteoblasts and osteocytes, related to the osteoclastogenic commitment of pre-osteoclasts. A better understanding of the impact of NPs on bone cell activities resulting in vivo in impaired bone turnover could give more information on the possible toxicity consequence of NPs on bone mass and the subsequent public health problems, such as bone disease. Nanoplastics represent novel emerging contaminants in all the environmental compartments. Weathering, degradation, and fragmentation of large plastic debris can induce the production of nanoplastics. Because of their very small size, nanoplastics can interact with all living organisms, including humans, at all levels of biological organizations, entering the cells and altering different pathways. However, at present, the information concerning the toxicity of nanoplastics on conventional and non-conventional model organisms, as well as on humans is very limited. The present study enlarges the knowledge of nanoplastic toxicity, investigating diverse adverse effects induced on murine bone cells, a proxy of human cells, which can represent an additional target of these contaminants.