Standardization of a Novel Semi-Automatic Software for Neurite Outgrowth Measurement

Summary

Neurite outgrowth assays provide a quantitative value about regenerative neuronal processes. The advantage of this semi-automatic software is that it segments cell bodies and neurites separately by creating a mask and measures various parameters such as neurite length, number of branch points, cell-body cluster area, and number of cell clusters.

Abstract

Effective live-imaging techniques are crucial to assess neuronal morphology in order to measure neurite outgrowth in real time. The proper measurement of neurite outgrowth has been a long-standing challenge over the years in the neuroscience research field. This parameter serves as a cornerstone in numerous in vitro experimental setups, ranging from dissociated cultures and organotypic cultures to cell lines. By quantifying the neurite length, it is possible to determine if a specific treatment worked or if axonal regeneration is enhanced in different experimental groups. In this study, the aim is to demonstrate the robustness and accuracy of the Incucyte Neurotrack neurite outgrowth analysis software. This semi-automatic software is available in a time-lapse microscopy system which offers several advantages over commonly used methodologies in the quantification of the neurite length in phase contrast images. The algorithm masks and quantifies several parameters in each image and returns neuronal cell metrics, including neurite length, branch points, cell-body clusters, and cell-body cluster areas. Firstly, we validated the robustness and accuracy of the software by correlating its values with those of the manual NeuronJ, a Fiji plug-in. Secondly, we used the algorithm which is able to work both on phase contrast images as well as on immunocytochemistry images. Using specific neuronal markers, we validated the feasibility of the fluorescence-based neurite outgrowth analysis on sensory neurons in vitro cultures. Additionally, this software can measure neurite length across various seeding conditions, ranging from individual cells to complex neuronal nets. In conclusion, the software provides an innovative and time-effective platform for neurite outgrowth assays, paving the way for faster and more reliable quantifications.

Introduction

In sciatic nerves, it is possible to measure axonal regeneration¹. Additionally, in vitro studies have shown the feasibility of monitoring axonal outgrowth^2,3 to comprehend its various phases, from axonal sprouting to axonal degeneration, in both healthy and injured neurons. By tracking these processes, it is possible to measure parameters such as axonal polarity, initiation, stability, and branching. The last parameter is crucial to understand neuropathic pain perception^4,5,6. Similar....

Protocol

1. Scanning the vessel on the machine

NOTE: The detection is performed by the built-in Basler Ace 1920-155 µm camera.

1. Open the program by clicking Connect to Device and selecting Schedule - To Acquire. Then click the + sign.
2. Specify whether the vessel will be scanned repeatedly or only 1x by choosing the option Scan on Schedule or Scan Once Now, respectively.
<.......

Discussion

Accurately measuring how neurons grow in healthy, injured, and diseased conditions is a critical parameter in many experimental setups within the neuroscience field. Whether working with organotypic cultures of whole DRG explants or dissociated cultures, properly measuring axonal outgrowth has been a significant challenge over the last 20 years. Without reliable and accurate quantification of neurite outgrowth, it is impossible to assess if a specific treatment, such as retinoic acid (for 4 days) for NSC-34 cells

Materials

Name	Company	Catalog Number	Comments
Collagenase A	Merck / Roche	10103586001
Dispase II (neutral protease, grade II)	Merck / Roche	4942078001
Dulbecco's modified eagle's medium	Merck / Sigma	D5796
Fetal bovin serum	Merck / Sigma	F7524
Ham's F-12 Nutrient Mix (1X)	ThermoFisher Scientific	21765029
Ham's F12 w/ L-Glutamine	Euroclone	ECM0135L
Hanks' Balanced Salt Solution	Euroclone	ECM0507L
HBSS (10X), no calcium, no magnesium, no phenol red	ThermoFisher Scientific	14185045
HyClone Characterized Fetal Bovine Serum (U.S.)	Cytiva	SH30071.03
Incucyte, Neurotrack Analysis Software	Sartorius	9600-0010
L-15 Medium (Leibovitz)	Millipore/Sigma	L5520
Laminin Mouse Protein, Natural	ThermoFisher Scientific	23017015
L-Cysteine	Merck / Sigma	C7352
Leibovitz's L-15 medium w/o L-glutamine	Euroclone	ECB0020L
mouse NGF 2.5S (>95%)	Alomone Labs	N-100
Neurobasal Medium [-] Glutamine	ThermoFisher Scientific	21103049
NSC-34	CELLutions Biosystems Inc (Ontario, Canada)	CLU140
Papain from papaya latex	Sigma	P4762
Penicillin-Streptomycin (5,000 U/mL)	ThermoFisher Scientific	15070063
Percoll (Density 1.130 g/mL)	Cytiva	17089101
Poly-D-Lysine Solution (1mg/mL)	EMD Millipore/Merck	A-003-E
Poly-L-Lysine Solution (0-01%)	Sigma	P4832
Recombinant Human NT-3	PeproTech	450-03
Retinoic Acid	Merck / Sigma	R2625
Trypsin-EDTA solution	Sigma	T3924
β-Tubulin III (Tuj1) antibody	Merck / Sigma	T8660