Increased Generation of Hepatocytes Expressing Bone Marrow-Derived Markers after Hematopoietic Progenitors’ Mobilization in a Murine Model of Hepatic Damage.

The contribution bone marrow (BM) cells to the repair of a damaged liver has been described in animal models and in humans. This process has been explained both as a result of hematopoietic stem cell (HSC) trans-differentiation, as well as a result of cell fusion between HSC-derived cells with cells from non-hematopoietic tissues. In the present work we have investigated whether the mobilization of HSCs can increase the generation of BM- derived hepatocytes (BM-DHs) in damaged livers. With this purpose, Ly-5.1 mice were myeloablated and transplanted with 10⁷ BM cells from Ly-5.2 congenic mice, which also express the green fluorescent protein (EGFP) under the control of the b-actin promoter. Three months after transplantation, groups of 4–6 animals were injected with saline or with carbon tetrachloride (CCL₄) for three more months to induce a cirrhosis-like damage. A marked dysbalance in serologic parameters, together with an altered hepatic structure was observed in the CCL₄-treated animals. Part of the animals corresponding to each group were mobilized with G-CSF for one, two or three weeks. No difference in the mobilization of hematopoietic cells was observed in CCL₄-treated versus non-treated animals. One month after G-CSF treatment, animals were sacrificed and the presence of BM-DHs, identified as EGFP⁺CD45⁻ hepatocyte-like cells, with ability to accumulate glycogen, was evaluated by fluorescent immuno-histochemistry using specific antibodies for EGFP and the murine Ly-5.2 panleukocyte antigen and successive PAS staining. BM-DHs were clearly observed after hepatic damage (4 BM-DH/10⁶ cells) at rates similar to results already published by others. Moreover, the G-CSF mobilization significantly augmented the percentage of BM-DHs in the liver of CCl₄-treated and non CCl₄-treated mice (69/10⁶ and 23/10⁶ cells, respectively). Whether these BM-DHs result from the trans-differentiation of HSCs or from the in vivo fusion of HSC-derived cells, and whether the mobilization treatment improve the recovery of the damaged liver are now under study. Taken together, this data demonstrate that the mobilization of HSCs from the BM to the periphery markedly increases the presence of BM-DHs in the liver of transplanted mice, opening the possibility of using hematopoietic growth factors in the treatment of non-hematopoietic degenerative diseases.