Generation and Long-term Maintenance of Nerve-free Hydra

Summary

Through a double treatment with colchicine, a plant-derived toxin that kills dividing cells, nerve-free Hydra vulgaris can be generated. These Hydra cannot feed or egest on their own. This paper describes an improved method for long-term maintenance of nerve free Hydra vulgaris in the laboratory.

Abstract

The interstitial cell lineage of Hydra includes multipotent stem cells, and their derivatives: gland cells, nematocytes, germ cells, and nerve cells. The interstitial cells can be eliminated through two consecutive treatments with colchicine, a plant-derived toxin that kills dividing cells, thus erasing the potential for renewal of the differentiated cells that are derived from the interstitial stem cells. This allows for the generation of Hydra that lack nerve cells. A nerve-free polyp cannot open its mouth to feed, egest, or regulate osmotic pressure. Such animals, however, can survive and be cultured indefinitely in the laboratory if regularly force-fed and burped. The lack of nerve cells allows for studies of the role of the nervous system in regulating animal behavior and regeneration. Previously published protocols for nerve-free Hydra maintenance involve outdated techniques such as mouth-pipetting with hand-pulled micropipette tips to feed and clean the Hydra. Here, an improved protocol for maintenance of nerve-free Hydra is introduced. Fine-tipped forceps are used to force open the mouth and insert freshly killed Artemia. Following force-feeding, the body cavity of the animal is flushed with fresh medium using a syringe and hypodermic needle to remove undigested material, referred to here as "burping". This new method of force-feeding and burping nerve-free Hydra through the use of forceps and syringes eliminates the need for mouth-pipetting using hand-pulled micropipette tips. It thus makes the process safer and significantly more time efficient. To ensure that the nerve cells in the hypostome have been eliminated, immunohistochemistry using anti-tyrosine-tubulin is conducted.

Introduction

The nervous system of Hydra consists of a nerve net, with neurons associated with both epithelial tissue layers¹. The nerve net is denser in the hypostome and peduncle and less dense in the body column². The nerve cells originate from interstitial stem cells, which are multipotent stem cells that give rise to secretory cells, nematocytes, germ cells, and neurons¹. It is possible to eliminate the interstitial cells of Hydra vulgaris through treatment with colchicine^3,4, a plant-derived toxin that kills dividing cells. Alth....

Protocol

1. Double Colchicine Treatment

1. Make a 0.4% colchicine (weight/volume) solution in Hydra medium^3,4,17.
   Caution: Colchicine is acutely toxic, fatal if swallowed, may cause genetic defects, and may cause eye damage. Handle the powder in a fume hood and wear full Personal Protective Equipment (PPE).
2. Incubate Hydra vulgaris (AEP strain was used here) that have been starved for 24 h in 0.4% colchicine at a ratio of 5 Hydra per mL of colchicine solution in a Petri dish for 8 h at room temperature in the dark.

Results

Immediately following the initial 8 h colchicine treatment, all Hydra survive. Some of these Hydra will have only tentacle stubs remaining (Figure 3A), while others will have completely lost their tentacles (Figure 3B). Over the following 1 or 2 days, the tentacles will continue to shrink until all Hydra have lost their tentacles. About 1 week following the treatment, t.......

Discussion

Hydra interstitial cells can be eliminated through a double colchicine treatment^3,4. In the days following the first treatment, it is critical to prevent contact between individual Hydra to avoid fusion of Hydra pieces into deformed Hydra. Also, animals that can eat unassisted following the first treatment must be removed as the second colchicine treatment may not be sufficient to eliminate the remaining interstitial cells from.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Colchicine	Acros Organics	227120010
1 mL Syringe	BD	301025
Brine Shrimp Eggs	Brine Shrimp Direct	N/A	Can be purchased locally
Brine Shrimp Hatchery Dish	Brine Shrimp Direct	N/A
60 mm x 15 mm Petri Dish	Celltreat	229663
30 G x 3/4" Hypodermic Needle	Covidien	1188830340	A 27G needle may also be used
2 x Fine-tip Tweezers	Dumont	0109-5-PO
Rifampicin	EMD Millipore	557303
Goat anti-mouse lgG, Pab (HRP Conjugate)	Enzo	ADI-SAB-100-J
Bovine Serum Albumin (BSA)	Fisher	BP9703-100
Scalpel	Fisher	08-920A
Fetal Bovine Serum (FBS)	Gibco	10437028
DAPI (4',6-Diamidino-2-Phenylindole, Dihydrochloride)	Invitrogen	D1306
PBS Tablets	MP Bio	2810305
Monoclonal Anti-Tubulin, Tyrosine	Sigma	T9028
Dimethyl Sulfoxide (DMSO)	Sigma	D2650
Hydrogen Peroxide	Sigma	216763
Paraformaldehyde (PFA)	Sigma	P6148
Triton X - 100	Sigma	T9284
Tween 20	Sigma	P1379
Urethane	Sigma	U2500
Air Pump	Tetra	77846-00
Glass Pasteur Pipette	VWR	53283-916	Length of the pipet does not matter
15 mL Tube	VWR	89039-670
P320 Sandpaper	3M	IBGABBV00397	Can be purchased at local home improvement store