Exposure to ALS-FTD-CSF generates TDP-43 aggregates in glioblastoma cells through exosomes and TNTs-like structure

// Xuebing Ding 1,* , Mingming Ma 2,3,* , Junfang Teng 1 , Robert K.F. Teng 4 , Shuang Zhou 3 , Jingzheng Yin 1 , Ekokobe Fonkem 5 , Jason H. Huang 5 , Erxi Wu 3 and Xuejing Wang 1 1 Department of Neurology, The First affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China 2 Department of Neurology, People’s Hospital of Zhengzhou University, Zhengzhou, Henan, China 3 Department of Pharmaceutical Sciences, North Dakota State University, Fargo, ND, USA 4 College of Engineering, California State University, Los Angeles, CA, USA 5 Scott & White Neuroscience Institute, Texas A & M Health Science Center, College of Medicine, Temple, TX, USA * These authors have contributed equally to this work Correspondence to: Xuejing Wang, email: // Erxi Wu, email: // Keywords : TDP-43, ALS, FTD, exosomes, tunneling nanotubes Received : April 26, 2015 Accepted : June 12, 2015 Published : June 28, 2015 Abstract Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) represent a continuum of devastating neurodegenerative diseases, characterized by transactive response DNA-binding protein of 43 kDa (TDP-43) aggregates accumulation throughout the nervous system. Despite rapidly emerging evidence suggesting the hypothesis of ‘prion-like propagation’ of TDP-43 positive inclusion in the regional spread of ALS symptoms, whether and how TDP-43 aggregates spread between cells is not clear. Herein, we established a cerebrospinal fluid (CSF)-cultured cell model to dissect mechanisms governing TDP-43 aggregates formation and propagation. Remarkably, intracellular TDP-43 mislocalization and aggregates were induced in the human glioma U251 cells following exposure to ALS-FTD-CSF but not ALS-CSF and normal control (NC) -CSF for 21 days. The exosomes derived from ALS-FTD-CSF were enriched in TDP-43 C-terminal fragments (CTFs). Incubation of ALS-FTD-CSF induced the increase of mislocated TDP-43 positive exosomes in U251 cells. We further demonstrated that exposure to ALS-FTD-CSF induced the generations of tunneling nanotubes (TNTs)-like structure and exosomes at different stages, which mediated the propagation of TDP-43 aggregates in the cultured U251 cells. Moreover, immunoblotting analyses revealed that abnormal activations of apoptosis and autophagy were induced in U251 cells, following incubation of ALS-CSF and ALS-FTD-CSF. Taken together, our data provide direct evidence that ALS-FTD-CSF has prion-like transmissible properties. TNTs-like structure and exosomes supply the routes for the transfer of TDP-43 aggregates, and selective inhibition of their over-generations may interrupt the progression of TDP-43 proteinopathy.