Bone Marrow Derived CD34⁺CXCR4⁺ Cells Maintain Viability, Mobility and Sterility up to 72 Hours and Are Compatible with Balloon Dilatation Catheters Used for Intra Coronary Artery Infusion; Pre-Clinical Development of a Pharmaceutical Grade Cell Therapy for Acute Myocardial Infarction (AMR-001).

Background: Approximately 20% of patients suffering a ST segment elevated acute myocardial infarction (AMI) have progressive peri-infarct zone myocardial cell death causing ventricular remodeling and poor cardiac outcomes in spite of standard medical care. Neo-angiogenesis has been proposed as a natural, albeit insufficient response to mitigate ventricular remodeling resulting from an AMI. Stromal derived growth factor-1 (SDF-1), the ligand for the CXCR4 receptor, is expressed by bone marrow derived CD34⁺ cells and is produced in increased quantities in the peri-infarct zone. CD34⁺CXCR4⁺ cells are the cells naturally mobilized from bone marrow following an AMI to induce neo-angiogenesis. Thus we conducted a series of pre-clinical studies to develop a pharmaceutical grade bone marrow derived cell therapy product with neo-angiogenic potential for direct intra-coronary artery infusion in patients following an AMI.

Methods: Bone marrow samples were obtained from healthy volunteer donors using a mini-bone marrow harvest technique (MMH). Bone marrow was stored at 4°C for up to 24 hours then processed using Isolex (Baxter, Ill) selection to acquire CD34⁺ cells, formulated into a delivery apparatus and stored again at 4°C for up to an additional 48 hours in a shipping container. Following storage the cell therapy product was assessed for cell recovery, viability, sterility, CXCR-4 mobility in an SDF-1 gradient, and CFU growth before and after perfusion through the internal port of an intra-coronary artery balloon dilatation catheter.

Results :13 donors (11F and 2M), with a median age of 43 years (mean 43; range 21 – 61 years) yielded a median % CD34⁺ cells of total nucleated cells of 1.45% (mean 1.38%; range 0.92 – 1.71%) with a higher % in males vs. females (1.67 vs.1.33%) and older (≥ 45years) vs. younger (1.49 vs.1.26%) donors. CD34⁺ cell viability (median 96%; range 91–98%), % CD34⁺ mobility in an SDF-1 gradient (11.8; 4.5–34%), CFU growth (20; 14–54) and sterility were all maintained for up to 72 hours from MMH (table). Passage of the CD34⁺ cells through a balloon catheter did not adversely affect any of these parameters including % mobility (at 72 hours n=3; Pre% 34, 6, 18: Post 34, 18, 23). Multiple passages (n=3) through balloon dilatation catheters did not result in significant CD34⁺ cell loss (median recovery 99%; range 97–111%) or loss of viability (95%; range 92–98%).

Conclusion: Bone marrow derived CD34⁺ cells selected using the Isolex device and formulated for shipping and administration maintain for up to 72 hours a high viability, mobility in an in vitro SDF-1 gradient, CFU potential and remain sterile despite multiple passages through a balloon dilatation catheter without significant cell loss. This formulation (AMR-001) provides a pharmaceutical grade cell therapy for clinical evaluation in AMI.