146 - A novel microfluidic leukapheresis device continuously and selectively removes leukocytes from circulation in rats

Leukapheresis is used acutely to treat symptomatic hyperleukocytosis in leukemic patients. Centrifugation-based apheresis requires large-bore catheters and equipment with large extracorporeal volumes that may pose additional challenges (e.g., hypotension, need for sedation) in small infants and children and may delay chemotherapy while organizing personnel and equipment. The development of simple, compact apheresis devices may alleviate many of the downsides of current leukapheresis technology.

Objective:

Our goal was to test the efficiency and safety of a novel controlled incremental filtration (CIF)-based microfluidic leukapheresis device in a recirculation regime within a living animal. We hypothesized that CIF-based leukapheresis will significantly reduce the circulating leukocyte count in rats.

Design/Methods:

Eight-channel CIF-based devices were created using soft lithography from polydimethylsiloxane with an inlet and 2 outlet channels and flushed with heparin sulfate (10 U/ml) before use in animals. We induced a surgical plane of anesthesia in outbred Sprague-Dawley rats of both sexes (13.9 ± 0.5 wk; 1:1::M:F) with isoflurane, then cannulated the trachea, carotid artery, external jugular vein, and caudal artery. Leukapheresis was performed for 3 hours by connecting a CIF device (8 rats) between the carotid and jugular vessels with a withdrawal pump to remove concentrated WBC. Sham rats (8) had a bridge placed in lieu of the device to simulate flow. An inline flow meter was used to measure the flow rates (Fig. 1). We collected blood for serial CBC tests (animals’ and removed blood) and to evaluate organ function. Statistical analyses were performed in GraphPad Prism 9. Data are represented by mean ± SEM.

Results:

There were no differences in the weight (375 ± 28 vs 367 ± 22 g), hemodynamics (MAP 73 ± 3 vs 78 ± 2 mmHg) or the number of total blood volumes processed (3.2 ± 0.4 vs 2.3 ± 0.4-fold) between CIF and sham groups. Rats receiving leukapheresis had significantly decreased WBC (54 ± 3 vs 99 ± 6% of baseline), with a slight decrease in erythrocytes (81 ± 2 vs 87 ± 1%) and no differences in platelets (96 ± 4 vs 100 ± 5%), as compared to sham. This decrease was primarily through preferential removal of larger WBC (monocytes and granulocytes; Fig. 2). There were no differences between CIF and sham in circulating markers of organ injury (Table 1).

Conclusion(s):

Our data show that CIF-based leukapheresis is a safe and efficient method of performing leukapheresis in a compact device. Future studies include testing devices on leukemic blood and pre-clinical trials in large animal models.