REVIEW Hematopoietic SCT with cryopreserved grafts: adverse reactions after transplantation and cryoprotectant removal before infusion Z Shu 1 , S Heimfeld 2 and D Gao 1 Transplantation of hematopoietic stem cells (HSCs) has been successfully developed as a part of treatment protocols for a large number of clinical indications, and cryopreservation of both autologous and allogeneic sources of HSC grafts is increasingly being used to facilitate logistical challenges in coordinating the collection, processing, preparation, quality control testing and release of the final HSC product with delivery to the patient. Direct infusion of cryopreserved cell products into patients has been associated with the development of adverse reactions, ranging from relatively mild symptoms to much more serious, life-threatening complications, including allergic/gastrointestinal/cardiovascular/neurological complications, renal/hepatic dysfunctions, and so on. In many cases, the cryoprotective agent (CPA) used—which is typically dimethyl sulfoxide (DMSO)—is believed to be the main causal agent of these adverse reactions and thus many studies recommend depletion of DMSO before cell infusion. In this paper, we will briefly review the history of HSC cryopreservation, the side effects reported after transplantation, along with advances in strategies for reducing the adverse reactions, including methods and devices for removal of DMSO. Strategies to minimize adverse effects include medication before and after transplantation, optimizing the infusion procedure, reducing the DMSO concentration or using alternative CPAs for cryopreservation and removing DMSO before infusion. For DMSO removal, besides the traditional and widely applied method of centrifugation, new approaches have been explored in the past decade, such as filtration by spinning membrane, stepwise dilution-centrifugation using rotating syringe, diffusion-based DMSO extraction in microfluidic channels, dialysis and dilution-filtration through hollow-fiber dialyzers and some instruments (CytoMate, Sepax S-100, Cobe 2991, microfluidic channels, dilution-filtration system, etc.) as well. However, challenges still remain: development of the optimal (fast, safe, simple, automated, controllable, effective and low cost) methods and devices for CPA removal with minimum cell loss and damage remains an unfilled need. Bone Marrow Transplantation advance online publication, 30 September 2013; doi:10.1038/bmt.2013.152 Keywords: Hematopoietic stem cells; cellular therapy; dimethyl sulfoxide; side effects; removal of DMSO INTRODUCTION Since the pioneering, Nobel prize-winning work by Thomas et al. 1 on transplantation of BM in the 1950s, 1 hematopoietic stem cell transplantation (HSCT) as a treatment option has been evaluated and successfully applied to a wide variety of malignancies and BM failure syndromes, including Hodgkin’s and non-Hodgkin’s lymphoma, 2–10 other lymphoid/myeloid 2–6,8,11–13 or leukemia malignancies, 5–8,14–18 myelodysplastic syndromes, 7,15 certain solid tumors, 3,5,6,12,13 sarcomas, 3,19 amyloidosis 2,8,20 and Fanconi anemia. 18 SCT has been performed using HSC from allogeneic, autologous and syngeneic donors. In addition to BM, HSC collected from mobilized PB or umbilical cord blood are currently in wide-spread clinical use, with the potential for transplantation of HSC derived from embryonic stem cell or induced pluripotent stem cell sources in the not-too-distant future. 21,22 Each of these HSC-containing populations can have certain advantages/disadvantages relative to the other sources, such as more rapid availability, easier collection, reduced risk to donors, reduced incidence of GVHD and lower requirement of HLA compatibility between donors and recipients. 16,18 Importantly, for most types of transplants, cryopreservation of HSC is a necessary and essential component of the clinical protocol. Long-term storage provides a solution to various logistical aspects such as the obligatory time interval needed between collection of the patient’s HSC product, treatment with high-dose therapy and subsequent infusion of the product in the case of autologous transplantation, or in the case of cord blood transplantation the mismatch between supply (when the baby is born) and demand (when the patient is ready to receive the unit). Cryopreservation also supports better HSC product characteriza- tion and quality control, improved donor screening for HLA or other markers that can impact successful outcomes, and optimal transportation from the point of collection to the site of infusion. Since the first studies of HSC freezing by Barnes and Loutit in 1955, 23 many experiments have been performed to optimize cryopreservation protocols to enhance overall recovery and functional capacity of HSC after freezing–thawing and transfusion. Numerous excellent reviews of stem cell cryopreservation have been published, ranging from basic scientific principles to clinical cell processing protocols. 24–28 The most widely applied cryopreservation protocols for HSC have the following general features: after collection, cells are washed and resuspended in a basal salt solution supplemented with some protein, which also contains one or more cryoprotective agents (CPA). Dimethyl 1 Department of Mechanical Engineering and Department of Bioengineering, University of Washington, Seattle, WA, USA and 2 Division of Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, WA, USA. Correspondence: Dr D Gao, Department of Mechanical Engineering and Department of Bioengineering, University of Washington, Seattle, WA 98195, USA or Dr S Heimfeld, Division of Clinical Research, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North D5-102, Seattle, WA 98109, USA. E-mail: dayong@u.washington.edu or sheimfel@fhcrc.org Received 15 May 2013; accepted 15 May 2013 Bone Marrow Transplantation (2013), 1–8 & 2013 Macmillan Publishers Limited All rights reserved 0268-3369/13 www.nature.com/bmt