Our research group established a technology for forming three-dimensional cell constructs to regenerate osteochondro cells without scaffolding. The established technology employed spheroids to form cell constructs. We also developed a method for arranging spheroids in arbitrary positions to form cell constructs in complex shapes. However, we could only form cell constructs as expected when the formed spheroids were the appropriate sizes. This study, therefore, aimed to chronologically analyze the spheroid morphological characteristics of rabbit mechanical stem cells using the developed spheroid morphological evaluation system. We set the numbers of cells/wells as 2 × 10⁴, 3 × 10⁴, 4 × 10⁴, 5 × 10⁴, 6 × 10⁴, and 7 × 10⁴ and the passage number as 7. Further, we observed the cultured spheroids every 24 hours after seeding for five days. The analysis enabled us to specify an optimal range for the numbers of cells required to form spheroids with high degrees of circularity. We could also control the formed spheroid sizes by adjusting the cell count and culturing time.

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