Plastic Surgery Research Council
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PSRC 60th Annual Meeting

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Donor-Recipient Chimeric Cell Transplantation as a Novel Rescue Therapy for Acute Radiation Syndrome: A Preliminary Report
Grzegorz Kwiecien, MD, Joanna Cwykiel, MSc, Maria Madajka, PhD, Adam Bobkiewicz, MD, Safak Uygur, MD, Maria Siemionow, MD, PhD, DSc.
Cleveland Clinic, Cleveland, OH, USA.

PURPOSE:
Victims of nuclear disasters present with acute radiation syndrome as a result of exposure to ionizing radiation. Impairment of immune system with subsequent sepsis is the most common cause of mortality. Following high exposure, stem cell transplantation is the only effective treatment but it carries several risks and access to stem cell sources is insufficient in case of extremely high demands. Therefore there is an urgent need to develop new effective therapies of acute radiation syndrome. The aim of this study was to test efficacy of ex-vivo created donor-recipient chimeric cells (DRCC) in reconstitution of bone marrow compartment following total body γ-irradiation (TBI).

METHODS:
Sixteen Lewis (RT1l) rats were exposed to sublethal dose (7Gy) of Cs-137 TBI. Irradiated rats were divided into 4 experimental groups (n=4 each) based on therapeutic approach: Group 1 - no intervention; Group 2 - normal saline injection; Group 3 - allogeneic bone marrow transplantation (BMT) [ACI (RT1a)]; and Group 4 - DRCC transplantation [ACI/LEW (RT1a/RT1l]. Saline as well as cellular therapeutics were delivered into the femoral bone at 6 hours following TBI. DRCC were created by ex-vivo fusion of bone marrow cells derived from fully MHC mismatched LEW (RT1l) and ACI (RT1a) donors. Briefly, donor and recipient cells were isolated, separately stained with the PKH26 and PKH67 fluorescent dyes, fused with polyethylene glycol (PEG) and sorted by flow cytometry. Cells presenting double staining were transplanted in a dose 10-12 x 106. All animals received supportive treatment with prophylactic antibiotics, fluids, and softened food during 90-days follow-up. Blood samples were evaluated using hemocytometer at 0, 5, 10, 20, 30, 40, 60 and 90 days after TBI. Reconstitution of CD3, CD4, CD8a, CD45RA, CD90 and CD11b/c positive cell populations was assessed by flow cytometry and donor specific chimerism was detected by PCR.

RESULTS:
We have successfully created DRCC by ex-vivo fusion of bone marrow derived cells. Survival rates in groups without cellular therapy (Groups 1-2) was 75%, in Group 3 treated with BMT was 50%, and in Group 4 treated with DRCC was 100%. Clinical signs of graft versus host disease (GVHD) were observed in 50% of animals that received BMT. Hematologic analysis revealed markedly increased peripheral leukocyte counts in DRCC treated animals between day 20th and 60th following transplantation, whereas red blood cell and platelet counts did not differ between groups. Differential counts confirmed regenerative effect of DRCC on both the lymphocyte and polymorphonuclear cell lineages. Evaluation of CD3, CD4, CD8a, CD45RA, CD90 and CD11b/c positive cells by flow cytometry as well as PCR assessment of donor-specific chimerism are currently in progress.

CONCLUSION:
Transplantation of DRCC after ionizing radiation exposure proved to be the most effective rescue therapy against acute radiation syndrome, as confirmed by 100% of recipients’ survival and expedited recovery of the hematopoietic system without developing GVHD. Our novel approach of DRCC transplantation may act as a bridging therapy supporting hematopoietic recovery and ameliorating injuries in patients exposed to the harmful effects of radiation.


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