According to the  Food and Drug Administration’s (FDA) Regulatory Considerations for Human Cell, Tissue, and Cellular and Tissue-Based Products: Minimal Manipulation and Homologous Use/Guidance for Industry and Food and Drug Administration Staff (November 2017), the FDA “generally consider an human cell, tissue, and cellular and tissue-based products to be for homologous use when it is used to repair, reconstruct, replace, or supplement:

• Recipient cells or tissues that are identical (eg, skin for skin) to the donor cells or tissues, and perform one or more of the same basic functions in the recipient as the cells or tissues performed in the donor; or
• Recipient cells or tissues that may not be identical to the donor’s cells or tissues, but that perform one or more of the same basic functions in the recipient as the cells or tissues performed in the donor