Predicting the quality of transplantable cord blood collections through prefreeze and postthaw Apgar scoring

Cord blood index predicts engraftment and early non-relapse mortality in adult patients with single-unit cord blood transplantation

How to select optimal cord blood (CB) remains an important clinical question. We developed and validated an index of CB engraftment, the cord blood index (CBI), which uses three weighted variables representing cell doses and HLA mismatches. We modeled the neutrophil engraftment time with competing events by random survival forests for competing risks as a function of the predictors: total nucleated cells, CD34, colony-forming units for granulocytes/macrophages, and the number of HLA mismatches at the antigen and allele levels. The CBI defined three groups that had different neutrophil engraftment rates at day 30 (High, 83.7% [95% CI, 79.2-88.1%]; Intermediate, 77.0% [95% CI, 73.7-80.2%]; Low, 68.4% [95% CI, 63.6-73.2%]), platelet engraftment rates at day 60 (High, 70.4% [95% CI, 64.9-75.9%]; Intermediate, 62.3% [95% CI, 58.5-66.0%]; Low, 49.3% [95% CI, 44.2-54.5%]), and non-relapse mortality at day 100 (High, 14.1% [95% CI, 9.9-18.3%]; Intermediate, 16.4% [95% CI, 13.5-19.3%]; Low, 21.3% [95% CI, 17.1-25.5%]). This novel approach is clinically beneficial and can be adopted immediately because it uses easily obtained pre-freeze data of CB.

Evaluation of post-thaw CFU-GM: clinical utility and role in quality assessment of umbilical cord blood in patients receiving single unit transplant

BACKGROUND

The CFU assay is considered the only in vitro assay that assesses the biologic function of hematopoietic stem and progenitor cells (HSPC).

STUDY DESIGN AND METHODS

To investigate the impact of post-thaw CFU-GM counts on the quality of umbilical cord blood (UCB), we studied transplant outcomes in 269 patients receiving single UCB transplant. We also correlated the post-thaw CFU-GM counts of 1912 units with the pre-freeze and post-thaw graft characteristics, hoping to optimize selection criteria of UCB. Data analysis included: total nucleated cells, viability, CD34+, nucleated red blood cells (NRBC), hematocrit, frozen storage time, and cord blood bank (CBB).

RESULTS

We demonstrated an association between post-thaw CFU-GM dose and the speed of neutrophil and platelet engraftment (p < 0.01). Higher post-thaw CFU-GM dose showed an increased benefit for neutrophil and platelet engraftment (p < 0.01). Post-thaw CD34+ cell dose and CFU-GM dose were strongly correlated (r = 0.78). However, CFU-GM dose showed additional benefit for patients receiving the lowest quartile of CD34+ dose. HLA disparity did not adversely impact either neutrophil or platelet engraftment. Post-thaw CFU-GM/million nucleated cells plated showed moderate correlation with pre-freeze and post-thaw CD34+ and weak correlation with other parameters. Post-thaw CFU-GM was not influenced by storage time, but was impacted by the CBB from which the unit is obtained (p < 0.01).

CONCLUSION

Post-thaw CFU-GM is an effective measure of the quality and efficacy of the UCB graft, particularly adding valuable clinical information when the CD34+ cell dose is low. Consideration of pre-freeze CD34+ cell content and CBB as additional selection criteria is warranted.

An objective flow cytometry method to rapidly determine cord blood potency in cryopreserved units

BACKGROUND

Cord blood banks have to determine the regenerative potential of cord blood units (CBUs) on a representative sample of the cryopreserved product before release to the transplant center. Potency can be measured by using a colony-forming unit (CFU) method, which delays the release of CBU by 7 to 14 days. To accelerate CBU qualification, we have developed a rapid method to assess the response of CD34 cells to interleukin (IL)-3. Flow cytometry was used to measure IL-3-induced STAT5 phosphorylation within CD34-cells. This IL-3 test was compared to the CFU method, as well as the aldehyde dehydrogenase (ALDH) enzyme-based assay.

STUDY DESIGN AND METHODS

Ten cryopreserved CBUs were analyzed for their contents in CD34 and CD45 viable cells, total CFUs, ADLHbright cells, and IL-3-responsive CD34+ cells. Extreme and mild warming event scenarios were simulated on CBUs and used as poor-quality samples. Segments, tubes, and bags from five CBUs were compared for their potency using IL-3 and CFU methods.

RESULTS

The IL-3 test was accurate in identifying the samples handled following standard operating procedures and those subjected to extreme warming events. Based on these results, a threshold of 55% of IL-3-responsive CD34 cells was established to identify good-quality samples. The IL-3 test was also the most sensitive to detect samples subjected to milder warming events.

CONCLUSIONS

Our new method for determining CBU functionality is rapid, unbiased, and robust. The IL-3 test described herein fulfills the requirements for validation, and we intend to implement this method in our cord blood bank facility.

Improving Quality and Potency Testing for Umbilical Cord Blood: A New Perspective

This article critically reviews current methods to test and characterize umbilical cord blood (UCB) for hematopoietic stem cell transplantation. These tests include total nucleated cell (TNC) count, viability, viable CD34-positive content, and the colony-forming unit assay. It is assumed that the data obtained are sufficient to perform a UCB stem cell transplant without actually determining the quality and potency of the stem cells responsible for engraftment. This assumption has led not only to a high graft failure rate attributed to low or lack of potency, but also to noncompliance with present statutes that require UCB stem cells to be of high quality and, indeed, potency for a transplant to be successful. New evidence now calls into question the quality of the data, based on the UCB processed TNC fraction because using this impure fraction masks and significantly underestimates the functionality of the stem cells in both the segment and the unit. It is proposed that UCB units should be processed to the mononuclear cell fraction and that new cost-effective technology that measures the quality and potency of UCB stem cells be implemented to achieve better practices in UCB testing. These changes would provide the transplant physician with the assurance that the stem cells will perform as intended and would reduce risk and increase safety and efficacy for the patient.

SIGNIFICANCE

Current stem cell transplantation of umbilical cord blood cells requires testing that includes four basic parameters that do not determine whether the stem cells are of high quality, as required by the Stem Cell Therapeutic and Research Act of 2005. No cord blood units collected or transplanted so far have been tested for stem cell quality or potency. New scientific evidence calls into question cord blood processing and testing practices required by regulatory agencies and standards organizations. A new perspective is described that includes stem cell quality and potency testing that could reduce graft failure rates.