Effect of pig‐specific cytokines on mobilization of hematopoietic progenitor cells in pigs and on pig bone marrow engraftment in baboons

Abstract

Mixed hematopoietic chimerism has been found to be a requirement for achieving specific immunologic hyporesponsiveness. Some of the requirements for in vitro and in vivo coexistence of discordant hematopoietic systems in the pig-to-baboon (or human) model have been investigated. We have tested the efficacy of pig-specific cytokines (PSC) (IL3, SCF, GM-CSF) in the mobilization of porcine bone marrow (BM) progenitors in vivo (i) in the pig and (ii) in baboons that underwent a conditioning regimen and porcine BM transplantation. In a preliminary in vitro study, porcine BM cells were incubated in various media to assess the effect of human plasma on pig progenitors in a colony-forming unit (CFU) assay. In in vivo studies, four pigs received PSC and one control pig did not. Six baboons underwent natural antibody removal, with subsequent pig BM transplantation. Four of these six underwent nonmyeloablative (n=2) or myeloablative (n=2) conditioning and all received PSC treatment. Two baboons did not receive PSC, one of which underwent a nonmyeloablative regimen. Sequential blood samples and BM biopsies in pigs and baboons were analyzed by CFU assay for the detection of porcine cells. Baboon samples were analyzed by polymerase chain reaction (PCR) to detect porcine DNA. In the case of the in vitro tests, colony forming by porcine progenitors was not inhibited by media containing human plasma and for the in vivo tests, PSC increased the number of progenitors in pig BM; mobilization of progenitors into the peripheral blood was observed. PSC-treated baboons which experienced transient depletion of leukocytes < 1,000/ml (as an effect of the conditioning regimen) had porcine BM cells detectable by PCR for as long as day 316 after BM transplantation. In conclusion we found that: (i) under the conditions of these studies, in vitro porcine progenitor cell growth was not inhibited by human plasma containing natural antibody and complement; (ii) PSC treatment led to an increased number of progenitors in pig BM and peripheral blood; (iii) the combination of an effective conditioning regimen and treatment with PSC was capable of inducing long-term survival of pig progenitors in baboons, although only a low level of engraftment was achieved.

High Incidence of Xenogenic Bone Marrow Engraftment in Pig-to-Baboon Intra-Bone Bone Marrow Transplantation

“…In vitro progenitor cell assays were performed according to methods previously described (21). Following 10–14 days of incubation in 5% CO 2 at 37°C, each culture dish was visually scored through an inverted microscope and evaluated for the presence and frequency of colony-forming units of granulocytes and/or macrophages (CFU-GM), colony-forming units of granulocytes, erythroid cells, macrophages, and/or megakaryocytes (CFU-GEMM) and burst-forming unit-erythroid (BFU-E).…”

Mixed chimerism and tolerance without whole body irradiation in a large animal model

“…PBSC collection has been described previously (20,21). A stem cell-mobilizing regimen consisting of recombinant porcine stem cell factor (pSCF; 100 µg/kg) in combination with recombinant porcine-IL-3 (pIL-3; 100 µg/kg) (both from Biotransplant, Boston, Massachusetts, USA), with or without recombinant human G-CSF (rhu G-CSF; Amgen Inc., Thousand Oaks, California, USA), was administered subcutaneously.…”

The porcine lung as a potential model for cystic fibrosis

“…Pigs express an ortholog of human GM-CSF (111). In addition, a cocktail of porcine IL3, stem cell factor, and GM-CSF stimulates the mobilization of porcine bone marrow (BM) progenitors in vivo in the pig and in baboons that underwent a conditioning regimen and porcine BM transplantation (132).…”