Stem cell activity of porcine c-kit+ hematopoietic cells (original) (raw)

2003, Experimental Hematology

Objective. A marker for hematopoietic stem cells (HSCs) of pigs, which are considered to be the most suitable donors for clinical xenotransplantation, has not yet been identified. In this study, we examined the HSC activity of porcine c-kit ϩ bone marrow cells (BMCs). Methods. The HSC activity of porcine c-kit ϩ BMCs was evaluated both in vitro using colonyforming unit (CFU) and cobblestone area-forming cell (CAFC) assays and in vivo in nonobese diabetic/severe combined immunodeficiency transgenic (NOD/SCID-Tg) mice carrying porcine cytokine transgenes. Results. Purified c-kit ϩ BMCs were substantially enriched for both CFUs and CAFCs in vitro and their transplantation led to long-term porcine hematopoiesis in vivo in mice. Although porcine chimerism was detectable in the peripheral blood of NOD/SCID-Tg mice receiving porcine c-kit ؊ BMCs at early time points after transplantation, the levels were markedly lower than those in mice receiving purified c-kit ϩ BMCs (0.2% Ϯ 0.14% vs 7.7% Ϯ 1.6% and 0.17% Ϯ 0.17% vs 5.6% Ϯ 2.1% at weeks 3 and 6, respectively). Importantly, all mouse recipients of porcine c-kit ϩ BMCs showed durable multilineage chimerism (Ͼ19 weeks), whereas no recipients of porcine c-kit ؊ BMCs sustained long-term engraftment. Moreover, porcine HSCs that had engrafted for 19 weeks in the recipients of porcine c-kit ϩ BMCs gave rise to clonogenic progenitors in vitro and reconstituted porcine hematopoiesis in secondary recipients. Conclusion. The present study demonstrates that c-kit is an essential marker of both longterm-repopulating HSCs and progenitor cells with early engraftment capacity. Ć 2003 International Society for Experimental Hematology. Published by Elsevier Inc. The development of methods for isolating the rare pluripotent hematopoietic stem cell (HSC) population, which is capable of self-renewal and multilineage differentiation in transplant recipients, has been a major challenge in the field of stem cell transplantation. The expression of the glycoprotein CD34 has often served as the hallmark of HSCs in many species [1,2]. However, increasing evidence indicates that functional HSCs also exist in the CD34 Ϫ cell population, and CD34 expression on HSCs can be variable depending on their state of activation [3-10]. A recent study using transgenic mice showed that human CD34 and mouse CD34 are regulated differently with respect to expression in longterm HSCs in bone marrow [11]. The expression of human