Abstract
Background: Studies with extracellular vesicles (EVs), including exosomes, isolated from mesenchymal stem cells (MSC) indicate benefits for the treatment of musculoskeletal pathologies as osteoarthritis (OA) and osteoporosis (OP). However, little is known about intercellular effects of EVs derived from pathologically altered cells that might influence the outcome by counteracting effects from “healthy” MSC derived EVs. We hypothesize, that EVs isolated from osteoblasts of patients with hip OA (coxarthrosis/CA), osteoporosis (OP), or a combination of both (CA/OP) might negatively affect metabolism and osteogenic differentiation of bone-marrow derived (B)MSCs.Methods: Osteoblasts, isolated from bone explants of CA, OP, and CA/OP patients, were compared regarding growth, viability, and osteogenic differentiation capacity. Structural features of bone explants were analyzed via μCT. EVs were isolated from supernatant of naïve BMSCs and CA, OP, and CA/OP osteoblasts (osteogenic culture for 35 days). BMSC cultures were stimulated with EVs and subsequently, cell metabolism, osteogenic marker gene expression, and osteogenic differentiation were analyzed.Results: Trabecular bone structure was different between the three groups with lowest number and highest separation in the CA/OP group. Viability and Alizarin red staining increased over culture time in CA/OP osteoblasts whereas growth of osteoblasts was comparable. Alizarin red staining was by trend higher in CA compared to OP osteoblasts after 35 days and ALP activity was higher after 28 and 35 days. Stimulation of BMSC cultures with CA, OP, and CA/OP EVs did not affect proliferation but increased caspase 3/7-activity compared to unstimulated BMSCs. BMSC viability was reduced after stimulation with CA and CA/OP EVs compared to unstimulated BMSCs or stimulation with OP EVs. ALP gene expression and activity were reduced in BMSCs after stimulation with CA, OP, and CA/OP EVs. Stimulation of BMSCs with CA EVs reduced Alizarin Red staining by trend.Conclusion: Stimulation of BMSCs with EVs isolated from CA, OP, and CA/OP osteoblasts had mostly catabolic effects on cell metabolism and osteogenic differentiation irrespective of donor pathology and reflect the impact of tissue microenvironment on cell metabolism. These catabolic effects are important for understanding differences in effects of EVs on target tissues/cells when harnessing them as therapeutic drugs.
Highlights
IntroductionThe presence of extracellular vesicles, i.e., exosomes (further referred to as EVs, according to Théry et al, 2018), was initially demonstrated in studies with normal and neoplastic cell lines as exfoliation of membranous vesicles containing 5’-nucleotidase activity (Trams et al, 1981)
The presence of extracellular vesicles, i.e., exosomes, was initially demonstrated in studies with normal and neoplastic cell lines as exfoliation of membranous vesicles containing 5’-nucleotidase activity (Trams et al, 1981)
extracellular vesicles (EVs) are defined as intraluminal vesicles (ILVs) that are released into the extracellular milieu by the fusion of multivesicular bodies (MVBs) with the plasma membrane (Edgar, 2016)
Summary
The presence of extracellular vesicles, i.e., exosomes (further referred to as EVs, according to Théry et al, 2018), was initially demonstrated in studies with normal and neoplastic cell lines as exfoliation of membranous vesicles containing 5’-nucleotidase activity (Trams et al, 1981) At first, they were regarded as waste products, but recently they were attributed with a possible therapeutic potential (Edgar, 2016). EVs are defined as intraluminal vesicles (ILVs) that are released into the extracellular milieu by the fusion of multivesicular bodies (MVBs) with the plasma membrane (Edgar, 2016) Their size varies between 30 and 150 nm and they are packed with a specific set of molecules, consisting of RNA, DNA, and proteins. That EVs isolated from osteoblasts of patients with hip OA (coxarthrosis/CA), osteoporosis (OP), or a combination of both (CA/OP) might negatively affect metabolism and osteogenic differentiation of bone-marrow derived (B)MSCs
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