Primary Cultures for IHC – Viability Assays

By Dr. Jean-Christophe Rochet *

A. Preparation of primary mesencephalic cultures

1. The mesencephalic neurons and glia are dissociated from neuronal tissue with trypsin (final concentration, 26 mg/ml in 0.9% [w/v] NaCl)
2. Cells are plated on coverslips previously treated with poly-L-lysine (5 mg/ml).
3. The media consists of DMEM, 10% (v/v) FBS, 10% (v/v) HS, penicillin (100 U/ml), and streptomycin (100 mg/ml).
4. Four days later, the cells were treated for 48 hr with AraC (20 mM) to inhibit the growth of glial cells.
   

B. Lentiviral transductions of primary cultures

1. AraC-treated primary cultures are transduced with lentiviral particles in the presence of polybrene (6 mg/ml).
2. Control cells were incubated without lentivirus.
3. After a 72 hr transduction period, the cells were treated with fresh media for an additional 48 hr and analyzed immunocytochemically.

C. Immunocytochemistry of primary midbrain cultures

1. Primary cells were fixed in 4% (w/v) paraformaldehyde in PBS for 30 min.
2. The cells were permeabilized and blocked simultaneously for 1 hr with PBS containing 1% (w/v) BSA, 10% (v/v) FBS, and 0.3% (v/v) Triton X-100.
3. After washing with PBS, the cells were treated overnight at 4°C with an anti-MAP2 monoclonal IgG (1:500) and an anti-TH polyclonal antibody (1:500) to monitor relative dopaminergic cell viability.
4. To determine the lentiviral transduction efficiency, untransduced cells or cells transduced with lacZ lentivirus (expressing beta-galactosidase fused to the V5 epitope) are treated at room temperature for 1 hr with:
   • (i) an anti-V5 monoclonal antibody (1:200) and an anti-MAP2 polyclonal antibody (1:500), or
   • (ii) an anti-V5 monoclonal antibody (1:200) and an anti-TH polyclonal antibody (1:500).
5. After washing, the cells were treated for 1 hr at room temperature with goat anti-mouse IgG conjugated to AlexaFluor® 488 (1:1000) and goat anti-rabbit IgG conjugated to AlexaFluor® 594 (1:2000).
6. The primary and secondary antibodies were prepared by diluting stock antibody solutions in PBS with 1% (w/v) BSA.
7. The coverslips were mounted onto slides using ProLong Gold Antifade® reagent, dried at room temperature overnight, and sealed with clear nail polish.

D. Measurement of primary neuron viability

1. MAP2- and TH-immunoreactive primary neurons can be counted in 10 randomly chosen observation fields for each experimental condition at a total magnification of 200x.
2. The data should be expressed as the percentage of MAP2-positive neurons that are also TH-positive.
3. Each experiment should be repeated 3 to 4 times using embryonic neurons isolated from independent animals.
4. Statistical analyses can be carried out using the program GraphPad Prism®, Version 4.0

Purdue University