Q1: Is the cartilage induced by the chondrogenic induction medium hyaline cartilage or fibrocartilage?
Theoretically, it is fibrocartilage.
Q2: Is coverslipping required after staining the chondrogenic induction samples?
When assessing results after chondrogenic induction—specifically after staining tissue sections with Alcian Blue to document the outcome—the cells are already dead. Since the samples are generally not used for further applications, coverslipping is not required.
Q3: Can the culture medium still be used if precipitation appears?
If only a small amount of flocculent precipitate is present—typically caused by the precipitation of cholesterol or proteins—the medium can still be used after centrifuging at 400–600 g for 5 minutes and collecting the supernatant. However, if the medium becomes heavily turbid, discolored, or exhibits substantial precipitation, it indicates contamination or degradation; discard it immediately.
Q4: How can I resolve issues where cartilage microspheres fail to form or cells do not aggregate after induction?
Ensure you use culture vessels made of low-adhesion materials. Avoid using cells with high passage numbers, as this diminishes their differentiation potential, and ensure that the cell density is sufficient. Chondrogenic induction requires cells to be cultured as aggregates rather than as an adherent monolayer; therefore, the cells must be centrifuged into a pellet for culture. We recommend using 1.5 × 10⁵ to 2.5 × 10⁵ cells per microsphere.
Q5: Why is the Alcian Blue staining very faint?
Insufficient induction time, improper fixation, or the use of degraded staining solution can all result in faint Alcian Blue staining. Ensure an induction period of at least 21 days, follow proper fixation protocols, and use a fresh Alcian Blue staining solution (pH 2.5).
Q6: What causes significant cell death during the initial stages of induction?
Failure to preheat the culture medium, an excessively high concentration of Dexamethasone, or the mechanical shock caused by abrupt medium changes can all lead to cell death. Before performing any procedures, preheat the culture medium to 37°C, and perform medium changes gently by dispensing the fluid along the inner wall of the culture well.
Q7: Why do the cartilage microspheres become loose, fall apart, or disperse and adhere to the culture vessel surface?
Insufficient centrifugation during the aggregation step, poor cell viability, or overly rough handling can all cause the cartilage microspheres to become loose, disintegrate, or flatten out and adhere to the vessel surface. You can effectively prevent these issues by increasing the centrifugation force used for aggregation, utilizing cells in good physiological condition, and avoiding vigorous pipetting (trituration) of the microspheres.
Q8: Why do the centers of the microspheres appear dark or necrotic?
The darkening and necrosis observed in the centers of the microspheres are caused by excessive microsphere size leading to hypoxia, delayed medium exchange, and nutrient deficiency. To prevent this, the size of the microspheres must be controlled, and the culture medium should be exchanged every 2 to 3 days.