Umbilical cord blood-derived mesenchymal cell fate after mouse umbilical cord blood transplantation

Neonatal umbilical cord blood transplantation halts skeletal disease progression in the murine model of MPS-I

Umbilical cord blood (UCB) is a promising source of stem cells to use in early haematopoietic stem cell transplantation (HSCT) approaches for several genetic diseases that can be diagnosed at birth. Mucopolysaccharidosis type I (MPS-I) is a progressive multi-system disorder caused by deficiency of lysosomal enzyme α-L-iduronidase, and patients treated with allogeneic HSCT at the onset have improved outcome, suggesting to administer such therapy as early as possible. Given that the best characterized MPS-I murine model is an immunocompetent mouse, we here developed a transplantation system based on murine UCB. With the final aim of testing the therapeutic efficacy of UCB in MPS-I mice transplanted at birth, we first defined the features of murine UCB cells and demonstrated that they are capable of multi-lineage haematopoietic repopulation of myeloablated adult mice similarly to bone marrow cells. We then assessed the effectiveness of murine UCB cells transplantation in busulfan-conditioned newborn MPS-I mice. Twenty weeks after treatment, iduronidase activity was increased in visceral organs of MPS-I animals, glycosaminoglycans storage was reduced, and skeletal phenotype was ameliorated. This study explores a potential therapy for MPS-I at a very early stage in life and represents a novel model to test UCB-based transplantation approaches for various diseases.

Increase of circulating CD11b(+)Gr1(+) cells and recruitment into the synovium in osteoarthritic mice with hyperlipidemia

Although recent studies suggest that hyperlipidemia is a risk factor for osteoarthritis (OA), the link between OA and hyperlipidemia is not fully understood. As the number of activated, circulating myeloid cells is increased during hyperlipidemia, we speculate that myeloid cells contribute to the pathology of OA. Here, we characterized myeloid cells in STR/Ort mice, a murine osteoarthritis model, under hyperlipidemic conditions. Ratios of myeloid cells in bone marrow, the spleen, and peripheral blood were determined by flow cytometry. To examine the influence of the hematopoietic environment, including abnormal stem cells, on the hematopoietic profile of STR/Ort mice, bone marrow transplantations were performed. The relationship between hyperlipidemia and abnormal hematopoiesis was examined by evaluating biochemical parameters and spleen weight of F₂ animals (STR/Ort x C57BL/6J). In STR/Ort mice, the ratio of CD11b⁺Gr1⁺ cells in spleens and peripheral blood was increased, and CD11b⁺Gr1⁺ cells were also present in synovial tissue. Splenomegaly was observed and correlated with the ratio of CD11b⁺Gr1⁺ cells. When bone marrow from GFP-expressing mice was transplanted into STR/Ort mice, no difference in the percentage of CD11b⁺Gr1⁺ cells was observed between transplanted and age-matched STR/Ort mice. Analysis of biochemical parameters in F₂ mice showed that spleen weight correlated with serum total cholesterol. These results suggest that the increase in circulating and splenic CD11b⁺Gr1⁺ cells in STR/Ort mice originates from hypercholesterolemia. Further investigation of the function of CD11b⁺Gr1⁺ cells in synovial tissue may reveal the pathology of OA in STR/Ort mice.

Bone marrow-engrafted cells after mice umbilical cord blood transplantation differentiate into osteoblastic cells in response to fracture and placement of titanium screws

As the in vivo function of bone marrow-engrafted umbilical cord blood (UCB)-derived mesenchymal cells (UCBCs) after UCB transplantation is unknown, we examined in vivo osteoblastic differentiation using mouse UCB transplantation and fracture models. UCBCs obtained from GFP transgenic mice were intravenously injected into irradiated C57BL/6 mice. After three months, the in vivo osteoblastic differentiation potential of bone marrow-engrafted UCBCs was examined histologically using a mouse fracture model. GFP-positive UCBCs were detected in the bone marrow of recipient mice. On day 7, UCBCs were observed in the fracture gap and surrounding the titanium screws of the fixation device. The UCBCs were also positive for alkaline phosphatase and von Kossa staining. By day 14, UCBCs were observed around and within a formed intramedullary callus. The newly formed woven bone consisted of ALP- and von Kossa-positive cells. Our findings suggest that UCBCs contribute to the fracture healing process after bone marrow engraftment and that UCBC transplantation can fully reconstruct not only hematopoietic cells but also mesenchymal cell lineages.