Download optimization of neuronal cultures derived from human induced

MANTRA
Multiwell Automated Neuronal Transmission Assay
OPTIMIZATION OF NEURONAL CULTURES DERIVED FROM HUMAN INDUCED PLURIPOTENT
STEM CELLS FOR HIGH THROUGHPUT ASSAYS OF SYNAPTIC FUNCTION
Pascal Laeng, Chris M. Hempel, James J. Mann, Jeffrey R. Cottrell and David J. Gerber, Galenea Corp, Cambridge MA 02139
Introduction
Alterations in synaptic transmission are associated with a number of
psychiatric and neurological disorders, suggesting that approaches directly
targeting synaptic function represent an attractive strategy for CNS drug
discovery. We previously described the development of a high-throughput
screening technology, termed the MANTRA™ (Multiwell Automated
NeuroTRansmission Assay) system, for identifying modulators of synaptic
function (Hempel CM et al., 2011) in rodent primary neuronal cultures. We
are employing the MANTRA system in an integrated drug discovery platform
that targets synaptic transmission at multiple levels.
SypHy Responses Measured on MANTRA: Similar
Frequency-dependence in Rat and Human Neurons
SypHy Delivered by AAV Transduction
a
a
Synaptophysin
H+
H+
H+
iCell Neurons – No glia
iCell Neurons – with glia
H+
Rat Neurons
H+
H+
b
Effect of Glia on MANTRA Activity
(3/5 weeks)
pHluorin
SypHy
b
Human
Neurons
Synaptotagmin
(6 weeks)
b
Overlay
b
**
Synapsin
The MANTRA system can be applied first to define synaptic functional
alterations in CNS disease model systems and then to perform screening
campaigns to identify compounds that restore normal synaptic function. In
addition to neuronal cultures from genetic mouse models, neurons derived
from human iPSC represent a valuable cellular model system for measuring
neurotransmission abnormalities in a human disease-relevant context.
c
***
1
d
2
3
Amplitude (F/F)
0.8
Rat Neurons
Human Neurons
0.2
(***p <0.001; **p < 0.01)
0
30
60
90
120
150
180
Time (sec)
(a) Human neurons show measurable pre-synaptic activity with lower
magnitude but similar overall waveform shapes and frequency
dependence compared to rat neurons
hiPSC
hNeurons
a
High Resolution Analysis of Presynaptic
Responses in Rat and Human Neurons
Human Neurons
Materials & Methods
Reporter Viral Transduction. For analysis of presynaptic function, cultures were infected with an adenoassociated virus (AAV) used to deliver a synaptophysin-pHluorin fusion fluorescent reporter construct (sypHy). The
synaptophysin-pHluorin reporter and the human synapsin promoter sequences were as previously described
(Hempel CM et al., 2011). The expression construct was generated by custom cDNA synthesis (Blue Heron Bio). A
recombinant adeno-associated virus of mixed serotype 1/2 (AAV1/2) was generated (GeneDetect). At 1 DIV or 7
DIV respectively, iCell and rat neurons were infected with the hSyn-SypHy-AAV.
High-resolution sypHy assays. To elicit action potentials 1 ms voltage pulses (4 or 6V) were passed using CX3
electrodes positioned manually inside individual wells of a 96-well plate. Stimulus patterns were delivered by a
stimulus isolation unit (Coulbourn Instruments) controlled by Igor Pro software (Wavemetrics) and a DAQ system
(National Instruments). Cultures were illuminated by a 475 nm LED (Cairn), filtered with a 470/525
emission/excitation filter cube (Zeiss), and imaged with a 1.3 NA 40x oil-immersion objective lens and an iXON
EMCCD camera (Andor) with 100 msec exposures at a frequency of 1 Hz. Fluorescence intensities were extracted
using ImageJ and analyzed with custom routines (Igor Pro).
SypHy
Ph. Contrast/SypHy
(a) The pH-sensitive GFP, pHluorin, tagged to synaptophysin (sypHy) was
chosen as the reporter for the MANTRA system. An adeno-associated
virus (AAV) of mixed 1/2 serotype was used to deliver sypHy to neuronal
cultures. SypHy expression was driven by the human synapsin promoter
(hSyn-sypHy-AAV).
Before Stimulation After Stimulation
Upper right:
Lower panel:
Expression of SypHy in iCell Neurons infected at 1DIV
and fixed at 2 weeks. MAP2 expressing cells represent
more than 95% of the cells in the culture and synapsin is
expressed in all neurons (presence of puncta). Arrows
show cells not stained for GFP.
Co-expression of hSypHy and synapsin can be detected
(arrow heads, higher magnification).
Expression of SypHy in iCell Neurons 4 weeks post
transduction. Most neurons express hSypHy (70%) in cell
body and axons.
ROI
Modulated
Synapsin
dF/F0 4V= 0.144
6V= 0.303
(Avg of 5 ROIs)
(b) Characterization of iCell Neurons transduced by hSyn-sypHy-AAV.
Upper left:
Rat Neurons
Localization and quantification of synaptic response in rat and iCell
neurons. Arrow heads and circles show active presynaptic sites in iCell and
rat neurons respectively. Preliminary data suggest that pre-synaptic
responses are similar in active synapses between rat and iCell neurons.
This suggests that the difference in MANTRA activity observed between rat
and human neurons might reflect a difference in the total number of mature
synapses/neurons present in the cultures.
a
MANTRA System Instrumentation
- Glia
+ Glia
(b) Synapsin immunofluorescence at higher magnification shows more
punctuate staining in axons and less staining in the cell body of
human
neurons in presence of rat or human (not shown) glia.
Conclusions

Transduced iCell neuronal cultures display measurable levels of
evoked presynaptic activity after 6 weeks in culture.

Enables application of human neurons to hit/lead (compound A)
validation in CNS drug discovery

Further optimization required for HTS in human neurons
a
Applications of MANTRA for New Functional
Phenotypic Assays in hiPSC-derived Neurons
1. The high-throughput capacity of the MANTRA system provides a
unique capability to test multiple conditions in parallel to generate
human iPSC-derived neurons with optimal synaptic functionality.
b
Rat Glia – No Neurons
• 10 Hz for 1 second at indicated
voltage
• Each voltage averaged over 5
trials
b
No
Neurons
(a) Sustained Ca2+ influx over the duration of the stimulus train indicates
reliable generation of action potentials by each stimulus pulse in iCell
Neurons.
The MANTRA instrumentation (left) consists of integrated 96-well parallel
imaging and field stimulation systems. Right, top shows the instrument deck
with its multiple technology components. Right, bottom shows the design of
the electrode tip module.
Map2
n =1
Co-cultures Neuron-Glia
Fluo-4 imaging on MANTRA
Response to 60 V, 10 Hz train
200 ms sampling interval
Stimulus: 10 stimuli delivered
over 1 sec.
• Signal averaged over 5 wells
GFP
(a) Triple immunofluorescence of iCell neurons grown for 6 weeks in
absence or presence of rat glia. Similar results were obtained with
human glia (not shown).
Evoked Ca+2 Flux in Human Neurons
•
•
•
•
b
+ Rat Glia
Ph. contrast
Evoked Ca+2 Transients. For analysis of ability of neurons to initiate action potentials following field stimulation,
neurons were incubated in assay buffer containing Fluo-4 for 1 hour and assayed on the MANTRA platform as
described below.
MANTRA Assays. Plates containing neuronal cultures were placed on an Evolution P3 liquid handling robot (EP3;
Perkin Elmer) with which culture medium was replaced with assay buffer containing (in mM): NaCl 119, KCl 2.5,
dextrose 30, HEPES 25, MgCl2 2, CaCl2 2, D-AP5 0.05, and DNQX 0.02. Test compounds, were added as part of
this wash step. Plates were transferred to a 30ºC incubator for one hour, transferred to the plate tray in the
MANTRA instrument, and subjected to a read/field stimulation protocol. Fluorescence readings were made using a
475/535 excitation/emission filter. Unless specified otherwise, field stimuli were 30V, 0.2 msec. The temperature of
the cabinet was set at 32ºC. Wells were imaged at 1 Hz with 300 msec exposures. Data files were processed
using in-house analysis routines (Igor Pro) and stored in a custom mySQL database.
Presence of Glia Increases Neurite Outgrowth
and Synapsin Expression in Human Neurons
(b) Compound A shows same effects on synaptic function in rat and human
iPSC-derived neurons measured on MANTRA
Use of human neurons for neurotransmission screening applications
requires that cultures achieve a sufficient degree of synaptic maturation to
yield a measureable proportion of synapses with pre- and post-synaptic
functionality. Here, we show that cultures of human neurons derived from
induced pluripotent stem cells (iPSCs) can be utilized in the MANTRA
system for synaptic functional assays.
Cell Culture. Post-mitotic human neurons derived from iPSCs (“iCell® Neurons”, Cellular Dynamics International,
USA) and primary neuronal cultures isolated from E18 rat embryos were seeded in 96-well plates (Greiner) coated
with poly-D-lysine with or without laminin. For some experiments, iCell Neurons or rat neurons were cultured with
rat or human astrocytes (Lonza) grown as a monolayer. iCell Neurons and rat neurons were seeded on the same
plates and tested in parallel. iCell Neurons grown in the absence of glia were maintained in serum free medium
provided by the manufacturer, while rat neurons were maintained in Neurobasal medium (Invitrogen) plus 2% B-27
Supplement (Invitrogen), 500 µM glutamine (Invitrogen), and 6.25 µM glutamate (Sigma). When neurons were cocultured with glia, medium consisted of Advanced DMEM/F12 plus 1% fetal calf serum. Cultures were analyzed
between 2 and 7 weeks in vitro on the MANTRA system or on a fluorescence microscope imaging system. For
both systems, fluorescence imaging was performed in parallel with field stimulation trains. Immunofluorescence
analysis was performed at different time points to evaluate the expression and localization of presynaptic proteins
and the sypHy reporter.
iCell Neurons grown in presence of glia show larger presynaptic
responses at all frequencies.
0.4
0.0
4
mNeurons
0.6
- Glia
KO/transgenic
MAP2
(b) The EV50 of evoked Ca2+ transients in iCell neurons is similar to that
measured from rat forebrain neuronal cultures, indicating a similar
action potential threshold. Pretreatment with TTX fully blocked evoked
Ca2+ transients at all stimulus intensities (not shown).
+ Rat
Neurons
+ iCell
Neurons
- Glia
Rat Glia + Rat Neurons
Rat Glia + hiCell Neurons
2. Ultimately, the MANTRA system can be used to characterize synaptic
abnormalities in neurons derived from patients and to screen for
compounds to restore normal synaptic transmission.
Galenea is interested in developing these 2 approaches via
collaborations. If your group is interested please contact us at
[email protected].
+ Glia (Rat)
(a) Phase contrast – 5 DIV post
seeding of neurons on rat glia.
(b) Analysis of expression of SypHy in
live
cultures (not-fixed) at 6 weeks
post- transduction
shows
no
detectable
signal in glia cultured
in the absence of seeded neurons
(negative
control,
low
magnification).
Acknowledgements
We thank members of Cellular Dynamics International, Vanessa Ott,
George Kopitas, Susan DeLaura, Lucas Chase and Rachel Llanas for
operational and technical support with iCell Neurons, and members of
Galenea, Eva Xia and Marie Fitzpatrick for MANTRA system operation.
This work was funded in part by NIH grant 1RC4MH092889-01.