P-040: RED BLOOD CELLS ADHESION AND OCCLUSION INDEX IN A PATIENT WITH SICKLE CELL DISEASE PRIOR AND POST HEMATOPOIETIC STEM CELL TRANSPLANT (HSCT)

Abstract

Purpose: Successful, full chimerism hematopoietic stem cell transplant (HSCT) from a matched sibling donor is curative for sickle cell disease (SCD). Current cell therapy trials of less established strategies typically have reduction in pain events as their primary endpoint, which is important, but not equivalent to a cure. Therapies with curative intent need to also be comprehensively assessed using analytical assays that provide detailed and robust functional assessment of red blood bell (RBC) properties. We hypothesize that microfluidic BioChip Assays can complement clinical assessments of efficacy in curative therapies. To test this, we assessed RBC adhesion using SCD BioChip A and RBC deformability using SCD BioChip D, before and after HSCT. Materials and methods: Venous blood samples were collected in EDTA tubes from a patient with SCD at University Hospitals, Cleveland Medical Center. The samples were tested with the SCD Biochip A and D at multiple time points between 2016 and 2022. SCD BioChip A devices were fabricated using lamination processes and were functionalized with Intercellular Adhesion Molecule 1 (ICAM-1) and Laminin (LN). Whole blood was injected into the ICAM-1 and LN-immobilized microchannels. An inverted microscope and microscopy camera were used to obtain high-resolution images of the whole channel for processing (Adobe Photoshop, San Jose, CA) and quantification of adhered RBCs per unit area (32 mm2). Adhesion Indices for ICAM-1 and LN were calculated. SCD BioChip D devices were fabricated using standard soft lithography protocols. RBCs were isolated from whole blood, re-suspended in PBS at 20% hematocrit, and passed through the device with a constant inlet pressure. Following a wash step, the microchannel was imaged, processed and Occlusion Index (OI) was quantified Results: The ICAM-1 and LN RBC Adhesion Indices are shown in Figure 1a and 1b. Occlusion Index is shown in Figure 1c. The green rectangle represents the normal range value for the HbAA controls as previously established. The patient had high Adhesion indices in both ICAM-1 and LN before HSCT, and decrease in Adhesion Indices to the normal range was observed after HSCT. The LN Adhesion Index was still within the normal range one year after HSCT, while the ICAM-1 Adhesion Index increased. Regarding the OI, the patient had high levels before HSCT which decreased 5 months after transplant but increased at 1-year follow-up. The number of hospital visits related to pain crisis were elevated before HSCT; after HSCT, the patient did not have any pain related visits for 5 months, but between 6 and 12 months from HSCT, the patient experienced new pain related visits. Conclusion: The Adhesion Index for ICAM-1 and LN and OI were abnormal in the patient with SCD pre-transplant, and decreased to normal levels in the first 5 months post-transplant with no pain related visits recorded in that period. Adhesion and Occlusion indices increased at 1-year post transplant as the number of pain related visits recorded in that period. These results suggest that SCD BioChip microfluidic devices could be an effective platform to estimate the RBCs functional properties to validate the efficacy of experimental cell-based therapies in SCD patients. a) RBCs Adhesion Index before and after the HSCT to Laminin a) and ICAM1 b). Occlusion index before and after HSCT c) Number of pain related visit before and after HSCT d). The authors do not declare any conflict of interest