Quantitative analysis of composite umbilical cord tissue health using a standardized explant approach and an assay of metabolic activity

Abstract

Background: Umbilical cord (UC) tissue can be collected in a noninvasive procedure and is enriched in progenitor cells with potential therapeutic value. Mesenchymal stromal cells (MSCs) can be reliably harvested from fresh or cryopreserved UC tissue by explant outgrowth with no apparent impact on functionality. A number of stem cell banks offer cryopreservation of UC tissue, alongside cord blood, for future cell-based applications. In this setting, measuring and monitoring UC quality is critical.

Materials and methods: UC explants were evaluated using a plating and scoring system accounting for cell attachment and proliferation. Explant scores for fresh and cryopreserved-then-thawed tissue from the same UC were compared. Metabolic activity of composite UC tissue was also assayed after exposure of the tissue to conditions anticipated to affect UC quality and compared with explant scores within the same UC.

Results: All fresh and cryopreserved tissues yielded MSC-like cells, and cryopreservation of the tissue did not prevent the ability to isolate MSCs by the explant method. Thawed UC tissue scores were 91% (±0.6%; P = 0.0009) that of the fresh, biologically identical tissue. Within the same UC, explant scores correlated well to both cell yield (R² = 0.85) and tissue metabolic activity (R² = 0.69).

Discussion: A uniform explant scoring assay can provide information about the quality of composite UC tissue. Such quantitative measurement is useful for analysis of tissue variability and process monitoring. Additionally, a metabolic assay of UC tissue health provides results that correlate well to explant scoring results.

Keywords: cryopreservation; mesenchymal stromal cells; stem cell banking; umbilical cord tissue.