Accelerated neuronal and synaptic maturation by BrainPhys medium increases A\u03b2 secretion and alters A\u03b2 peptide ratios from iPSC-derived cortical neurons

Tugce Munise Satir,Lotta Agholme,Selina Wray,Petra Bergström,Faisal Hayat Nazir,Henrik Zetterberg,Kaj Blennow,Dzeneta Vizlin-Hodzic,Erik Hardselius

doi:10.1038/s41598-020-57516-7

Abstract

One of the neuropathological hallmarks of Alzheimer’s disease (AD) is cerebral deposition of amyloid plaques composed of amyloid β (Aβ) peptides and the cerebrospinal fluid concentrations of those peptides are used as a biomarker for AD. Mature induced pluripotent stem cell (iPSC)-derived cortical neurons secrete Aβ peptides in ratios comparable to those secreted to cerebrospinal fluid in human, however the protocol to achieve mature neurons is time consuming. In this study, we investigated if differentiation of neuroprogenitor cells (NPCs) in BrainPhys medium, previously reported to enhance synaptic function of neurons in culture, would accelerate neuronal maturation and, thus increase Aβ secretion as compared to the conventional neural maintenance medium. We found that NPCs cultured in BrainPhys displayed increased expression of markers for cortical deep-layer neurons, increased synaptic maturation and number of astroglial cells. This accelerated neuronal maturation was accompanied by increased APP processing, resulting in increased secretion of Aβ peptides and an increased Aβ38 to Aβ40 and Aβ42 ratio. However, during long-term culturing in BrainPhys, non-neuronal cells appeared and eventually took over the cultures. Taken together, BrainPhys culturing accelerated neuronal maturation and increased Aβ secretion from iPSC-derived cortical neurons, but changed the cellular composition of the cultures.

Highlights

One of the neuropathological hallmarks of Alzheimer’s disease (AD) is cerebral deposition of amyloid plaques composed of amyloid β (Aβ) peptides and the cerebrospinal fluid concentrations of those peptides are used as a biomarker for AD
To determine if culturing induced pluripotent stem cell (iPSC)-derived neuroprogenitor cells (NPCs) in BrainPhys would accelerate the differentiation towards functional cortical neurons and if this would affect the secretion of amyloid beta precursor protein (APP) cleavage products, we performed a comparative study where human iPSC-derived NPCs were differentiated into neurons in BrainPhys in parallel with Neuronal maintenance medium (NMM)
No statistically significant increase in the mRNA levels of PAX6 (Fig. 1CI), a marker of radial glial progenitor cells, was observed, they showed a tendency to increase in BrainPhys, while levels of TBR1 mRNA (Fig. 1CII), a marker of cortical layer VI and post-mitotic projection neurons, increased significantly

Summary

Introduction

One of the neuropathological hallmarks of Alzheimer’s disease (AD) is cerebral deposition of amyloid plaques composed of amyloid β (Aβ) peptides and the cerebrospinal fluid concentrations of those peptides are used as a biomarker for AD. We investigated if differentiation of neuroprogenitor cells (NPCs) in BrainPhys medium, previously reported to enhance synaptic function of neurons in culture, would accelerate neuronal maturation and, increase Aβ secretion as compared to the conventional neural maintenance medium. We found that NPCs cultured in BrainPhys displayed increased expression of markers for cortical deep-layer neurons, increased synaptic maturation and number of astroglial cells This accelerated neuronal maturation was accompanied by increased APP processing, resulting in increased secretion of Aβ peptides and an increased Aβ38 to Aβ40 and Aβ42 ratio. We found that neuronal differentiation of NPCs for less than 35 days in BrainPhys increased neurite branching, as well as the expression of markers for deep-layer cortical neurons, synaptic activity and glial cells in the cultures. Future studies will reveal the consequences of the observed increased β-cleavage and secretion of Aβ38

Methods

Results

Conclusion