. Author manuscript; available in PMC: 2009 Jun 22.

Published in final edited form as: Nat Protoc. 2006;1(4):2012–2018. doi: 10.1038/nprot.2006.323

TABLE 1.

Troubleshooting table.

Problem	Possible reason	Solution
Collagen gels with embedded fibroblasts did not contract.	Wrong number of fibroblasts added to the gels.	Ensure number of fibroblasts 3.5−4.5 × 10⁵ per gel.
	Fibroblasts died in the gels because of low pH.	Neutralize the collagen solution with sterile NaOH before adding fibroblasts.
Some gels contracted whereas others did not.	Fibroblasts were poorly mixed in the collagen solution.	Mix fibroblasts with the collagen solution by gently inverting the tubes.
Poor epithelial differentiation.	Density of keratinocytes on the gels was too low.	Seed proper number, 1.0−1.2 ×10⁶ oral epithelial cells on the gels.
	Failure to maintain cultures on air-liquid interface.	Check cultures daily for the medium levels. Aspirate media from inside the inserts.
None, few or disturbed epithelial layers.	Cultures were disturbed while placing into the cassettes or during during histological processing.	While harvesting the cultures, do not disturb them. Make sure the cultures do not move along the sponges in the cassettes.