Effects of microplastics on the bones: a comprehensive review

A growing role for the skeleton in human health and longevity emerged recently. However, knowledge regarding the effects of new risk factors, linked to modern life, for bone diseases is not documented satisfactorily. Micro- and nanoplastics (MPs) are environmental and health concerns due to their widespread detection in the human surrounding environment. This narrative review aims to critically summarize current knowledge on the effects of MPs on bone and bone marrow and to explore potential links to human bone diseases, such as osteoporosis. Worryingly, MPs were recently detected in human bone tissue. In the last years, in vitro studies have shown that MPs affect cell viability, induce cell senescence, alter adipogenic cell differentiation, modify gene expression, increase reactive oxygen species production, trigger inflammatory responses, and promote osteoclastogenesis. MPs have also been associated with the impairment of the bone marrow mesenchymal stromal cell differentiation potential. Experimental animal studies indicated that MPs ingestion disturbs gut microbiota and reduces white blood cell counts, suggesting compromised bone marrow function. MPs have been detected in bone tissue following intragastric administration and were shown to affect various blood cells. Additionally, MPs accumulation in bones reduced their growth and impaired trabecular microarchitecture likely due to the osteoblasts' decreased osteogenic function. Although numerous in vitro and in vivo studies have described the effects of MPs on cells and bone tissue using animal models, the mechanistic impact of MPs accumulation in human bones or bone marrow remains largely unexplored.