Identification of a Hematopoietic Cell Dedifferentiation-Inducing Factor YUNYUAN LI, 1 HANS ADOMAT, 2 EMMA TOMLINSON GUNS, 2 PAYMAN HOJABRPOUR, 3 VINCENT DURONIO, 3 TERRY-ANN CURRAN, 1 REZA BARADAR JALILI, 1 WILLIAM JIA, 1,4 ZAHID DELWAR, 5 YUN ZHANG, 1 SANAM SALIMI ELIZEI, 1 AND AZIZ GHAHARY 1 * 1 Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada 2 Vancouver Prostate Centre, Vancouver, British Columbia, Canada 3 Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada 4 Brain Research Centre, University of British Columbia, Vancouver, British Columbia, Canada 5 Department of Experimental Medicine, University of British Columbia, Vancouver, British Columbia, Canada It has long been realized that hematopoietic cells may have the capacity to trans-differentiate into non-lymphohematopoietic cells under specific conditions. However, the mechanisms and the factors for hematopoietic cell trans-differentiation remain unknown. In an in vitro culture system, we found that using a conditioned medium from proliferating fibroblasts can induce a subset of hematopoietic cells to become adherent fibroblast-like cells (FLCs). FLCs are not fibroblasts nor other mesenchymal stromal cells, based on their expression of type-1 collagen, and other stromal cell marker genes. To identify the active factors in the conditioned medium, we cultured fibroblasts in a serum-free medium and collected it for further purification. Using the fractions from filter devices of different molecular weight cut-offs, and ammonium sulfate precipitation collected from the medium, we found the active fraction is a protein. We then purified this fraction by using fast protein liquid chromatography (FPLC) and identified it by mass spectrometer as macrophage colony-stimulating factor (M-CSF). The mechanisms of M-CSF-inducing trans-differentiation of hematopoietic cells seem to involve a tyrosine kinase signalling pathway and its known receptor. The FLCs express a number of stem cell markers including SSEA-1 and -3, OCT3/4, NANOG, and SOX2. Spontaneous and induced differentiation experiments confirmed that FLCs can be further differentiated into cell types of three germ layers. These data indicate that hematopoietic cells can be induced by M-CSF to dedifferentiate to multipotent stem cells. This study also provides a simple method to generate multipotent stem cells for clinical applications. J. Cell. Physiol. 231: 1350–1363, 2016. ß 2015 Wiley Periodicals, Inc. Stem cells have provided exciting prospects for cell-based clinical applications. They are undifferentiated cells defined by their abilities to self-renew and differentiate into mature cells. Classically, stem cells can be divided into adult stem cells and embryonic stem cells (pluripotent). Compared to embryonic stem cells, adult stem cells are not pluripotent, but do have many advantages, such as convenience toobtain, diminished ethical issues, and lower tumor risk when used in vivo. Adult stem cells often reside in the different tissues of body and provide the capacity for tissue repair and regeneration during tissue turnover or injury(Bjornson et al., 1999). Normally, many different types of adult stem cells exist. For instance, mesenchymal stem cells (MSCs) are located in bone marrow and adipose tissue can give rise to multiple mesenchymal lineages (Ding et al., 2011). Hematopoietic stem cells (HSCs) in bone marrowcontribute to mature cells of various blood lineages (Spangrude et al., 1988). Epithelial stem cells located attached hair follicles can generate keratinocytes (Ohyama et al., 2006). Satellite cells in skeletal muscle are myogenic stem cells responsible for the repair of skeletal muscle (Chen and Goldhamer, 2003). All suggest the importance of adult stem cells in tissue renewal and regeneration. Unfortunately, unlike embryonic stem cells, adult stem cells usually have limited potency and give rise only to the cells within the tissue of residence. In addition, adult stem cells other than HSCs are normally difficult to isolate and grow in vitro. Therefore, the search for convenient sources of adult stem cells with pluripotency or multipotency is of significant importance. Hematopoietic stem cells (HSCs) are relatively easily accessible sources of adult stem cells. They can be obtained from bone marrow, cord blood, and peripheral blood. It had been postulated that HSCs possess the capacity to trans-differentiate into the non-hematopoietic lineages in vivo. In the past decade, researchers have found that HSCs can directly trans-differentiate into non-lymphohematopoietic cells such as muscle fibers (Gussoni et al., 1999), hepatocytes Conflicts of interest: The authors declare that they have no conflict of interest. Contract grant sponsor: Canadian Institute of Health Research (CIHR). Contract grant sponsor: BC Spectra Energy. Contract grant sponsor: International Brotherhood of Electrical Workers. Contract grant sponsor: Rick Hansen Foundation. *Correspondence to: Aziz Ghahary, Department of Surgery, University of British Columbia, 4520 ICORD, 818 10th Avenue, Vancouver, BC V5Z 1M9. E-mail: aghahary@mail.ubc.ca Manuscript Received: 20 August 2015 Manuscript Accepted: 2 November 2015 Accepted manuscript online in Wiley Online Library (wileyonlinelibrary.com): 3 November 2015. DOI: 10.1002/jcp.25239 ORIGINAL RESEARCH ARTICLE 1350 Journal of Journal of Cellular Physiology Cellular Physiology © 2015 WILEY PERIODICALS, INC.