Mitochondrial Electron Transport Chain Complex II Dysfunction Causes Premature Aging of Hematopoietic Stem Cells

Mitochondria are indispensable in maintaining hematopoietic stem cells (HSCs), and mitochondrial complex II (MCII) has been recognized as a key component of HSCs. However, the physiological role of MCII on long-term hematopoiesis and hematopoietic reconstitution capacity remains unknown. Hence, this study evaluated the impact of MCII dysfunctions on long-term HSC maintenance and hematopoietic homeostasis among conditional transgenic mice with a missense mutation in the succinate dehydrogenase complex subunit C gene (SdhcV69E). HSCs collected from SdhcV69E mice had a higher reactive oxygen species (ROS) accumulation and DNA damage in response to mitochondrial activation. Via the aging stress response, MCII dysfunctions caused decreased white blood cell count with myeloid-skewing property, macrocytic anemia, and thrombocytosis. Moreover, the HSCs of aged SdhcV69E mice exhibited greater ROS accumulation and lower membrane potential. Transplantation-induced replicative stress also caused premature senescent hematopoiesis. Furthermore, accelerated ROS accumulation and profound DNA damage in HSCs were observed in the SdhcV69E-derived cell recipients. The long-term hematopoietic reconstitution capacity was remarkably impaired in HSCs from the SdhcV69E-derived cell recipients. Taken together, MCII plays an essential role in long-term hematopoiesis, and MCII dysfunctions with aging or replicative stresses caused excessive ROS accumulation and DNA damage in HSCs, leading to premature senescence.

Delivering mRNAs to mouse tissues using the SEND system

mRNAs produced in a cell are almost always translated within the same cell. Some mRNAs are transported to other cells of the organism through processes involving membrane nanotubes or extracellular vesicles. A recent report describes a surprising new phenomenon of encapsulating mRNAs inside virus-like particles (VLPs) to deliver them to other cells in a process that was named SEND (Selective Endogenous eNcapsidation for cellular Delivery). Although the seminal work demonstrates the SEND process in cultured cells, it is unknown whether this phenomenon occurs in vivo . Here, we demonstrate the SEND process in living organisms using specially designed genetically engineered mouse models. Our proof of principle study lays a foundation for the SEND-VLP system to potentially be used as a gene therapy tool to deliver therapeutically important mRNAs to tissues.

Dll1 Can Function as a Ligand of Notch1 and Notch2 in the Thymic Epithelium

T-cell development in the thymus is dependent on Notch signaling induced by the interaction of Notch1, present on immigrant cells, with a Notch ligand, delta-like (Dll) 4, on the thymic epithelial cells. Phylogenetic analysis characterizing the properties of the Dll4 molecule suggests that Dll4 emerged from the common ancestor of lobe- and ray-finned fishes and diverged into bony fishes and terrestrial organisms, including mammals. The thymus evolved in cartilaginous fishes before Dll4, suggesting that T-cell development in cartilaginous fishes is dependent on Dll1 instead of Dll4. In this study, we compared the function of both Dll molecules in the thymic epithelium using Foxn1-cre and Dll4-floxed mice with conditional transgenic alleles in which the Dll1 or Dll4 gene is transcribed after the cre-mediated excision of the stop codon. The expression of Dll1 in the thymic epithelium completely restored the defect in the Dll4-deficient condition, suggesting that Dll1 can trigger Notch signaling that is indispensable for T-cell development in the thymus. Moreover, using bone marrow chimeras with Notch1- or Notch2-deficient hematopoietic cells, we showed that Dll1 is able to activate Notch signaling, which is sufficient to induce T-cell development, with both the receptors, in contrast to Dll4, which works only with Notch1, in the thymic environment. These results strongly support the hypothesis that Dll1 regulates T-cell development via Notch1 and/or Notch2 in the thymus of cartilaginous fishes and that Dll4 has replaced Dll1 in inducing thymic Notch signaling via Notch1 during evolution.

LMO2 is essential to maintain the ability of progenitors to differentiate into T-cell lineage in mice

Notch signaling primarily determines T-cell fate. However, the molecular mechanisms underlying the maintenance of T-lineage potential in pre-thymic progenitors remain unclear. Here, we established two murine Ebf1-deficient pro-B cell lines, with and without T-lineage potential. The latter expressed lower levels of Lmo2; their potential was restored via ectopic expression of Lmo2. Conversely, the CRISPR/Cas9-mediated deletion of Lmo2 resulted in the loss of the T-lineage potential. Introduction of Bcl2 rescued massive cell death of Notch-stimulated pro-B cells without efficient LMO2-driven Bcl11a expression but was not sufficient to retain their T-lineage potential. Pro-B cells without T-lineage potential failed to activate Tcf7 due to DNA methylation; Tcf7 transduction restored this capacity. Moreover, direct binding of LMO2 to the Bcl11a and Tcf7 loci was observed. Altogether, our results highlight LMO2 as a crucial player in the survival and maintenance of T-lineage potential in T-cell progenitors via the regulation of the expression of Bcl11a and Tcf7.

IMiDs uniquely synergize with TKIs to upregulate apoptosis of Philadelphia chromosome-positive acute lymphoblastic leukemia cells expressing a dominant-negative IKZF1 isoform

The long-term prognosis of Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph + ALL) is still unsatisfactory even after the emergence of tyrosine kinase inhibitors (TKIs) against chimeric BCR-ABL, and this is associated with the high incidence of genetic alterations of Ikaros family zinc finger 1 (IKZF1), most frequently the hemi-allelic loss of exons 4–7 expressing a dominant-negative isoform Ik6. We found that lenalidomide (LEN), a representative of immunomodulatory drugs (IMiDs), which have been long used for the treatment of multiple myeloma, specifically induced accumulation of Ik6 with the disappearance of functional isoforms within 24 h (i.e., abrupt and complete shut-down of the IKZF1 activity) in Ik6-positive Ph+ALL cells in a neddylation-dependent manner. The functional IKZF3 isoforms expression was also abruptly and markedly downregulated. The LEN treatment specifically suppressed proliferation of Ik6-positive-Ph+ALL cells by inducing cell cycle arrest via downregulation of cyclins D3 and E and CDK2, and of importance, markedly upregulated their apoptosis in synergy with the TKI imatinib (IM). Apoptosis of IM-resistant Ph+ALL cells with T315I mutation of BCR-ABL was also upregulated by LEN in the presence of the newly developed TKI ponatinib. Analyses of flow cytometry, western blot, and oligonucleotide array revealed that apoptosis was caspase-/p53-dependent and associated with upregulation of pro-apoptotic Bax/Bim, enhanced dephosphorylation of BCR-ABL/Akt, and downregulation of oncogenic helicase genes HILLS, CDC6, and MCMs4 and 8. Further, the synergism of LEN with IM was clearly documented as a significant prolongation of survival in the xenograft mice model. Because this synergism was further potentiated in vitro by dexamethasone, a key drug for ALL treatment, the strategy of repositioning IMiDs for the treatment of Ik6-positive Ph+ALL patients certainly shed new light on an outpatient-based treatment option for achieving their long-term durable remission and higher QOL, particularly for those who are not tolerable to intensified therapeutic approaches.

Targeting of plasminogen activator inhibitor-1 activity promotes elimination of chronic myeloid leukemia stem cells

Therapeutic strategies that target leukemic stem cells (LSC) provide potential advantages in the treatment of chronic myeloid leukemia (CML). Here we showed that selective blockade of plasminogen activator inhibitor-1 (PAI-1) enhances the susceptibility of CML-LSC to tyrosine kinase inhibitor (TKI), which facilitates the eradication of CML-LSC and leads to sustained remission of the disease. We demonstrated for the first time that the TGF-−PAI-1 axis was selectively augmented in CMLLSC in the bone marrow (BM), thereby protecting CML-LSC from TKI treatment. Furthermore, the combined administration of the TKI imatib plus a PAI-1 inhibitor, in a mouse model of CML, significantly enhanced the eradication of CML cells in the BM and prolonged the survival of CML mice. The combined therapy of imatinib and a PAI-1 inhibitor prevented the recurrence of CML-like disease in serially transplanted recipients, indicating the elimination of CML-LSC. Interestingly, PAI-1 inhibitor treatment augmented membrane-type matrix metalloprotease-1 (MT1-MMP)-dependent motility of CML-LSC, and the anti-CML effect of PAI-1 inhibitor was extinguished by the neutralizing antibody for MT1-MMP, underlining the mechanistic importance of MT1-MMP. Our findings provide evidence of, and a rationale for, a novel therapeutic tactic, based on the blockade of PAI- 1 activity, for CML patients.

Podoplanin is indispensable for cell motility and platelet-induced epithelial-to-mesenchymal transition-related gene expression in esophagus squamous carcinoma TE11A cells

Background

The transmembrane glycoprotein podoplanin (PDPN) is upregulated in some tumors and has gained attention as a malignant tumor biomarker. PDPN molecules have platelet aggregation-stimulating domains and, are therefore, suggested to play a role in tumor-induced platelet activation, which in turn triggers epithelial-to-mesenchymal transition (EMT) and enhances the invasive and metastatic activities of tumor cells. In addition, as forced PDPN expression itself can alter the propensity of certain tumor cells in favor of EMT and enhance their invasive ability, it is also considered to be involved in the cell signaling system. Nevertheless, underlying mechanisms of PDPN in tumor cell invasive ability as well as EMT induction, especially by platelets, are still not fully understood.

Methods

Subclonal TE11A cells were isolated from the human esophageal squamous carcinoma cell line TE11 and the effects of anti-PDPN neutralizing antibody as well as PDPN gene knockout on platelet-induced EMT-related gene expression were measured. Also, the effects of PDPN deficiency on cellular invasive ability and motility were assessed.

Results

PDPN-null cells were able to provoke platelet aggregation, suggesting that PDPN contribution to platelet activation in these cells is marginal. Nevertheless, expression of platelet-induced EMT-related genes, including vimentin, was impaired by PDPN-neutralizing antibody as well as PDPN deficiency, while their effects on TGF-β-induced gene expression were marginal. Unexpectedly, PDPN gene ablation, at least in either allele, engendered spontaneous N-cadherin upregulation and claudin-1 downregulation. Despite these seemingly EMT-like alterations, PDPN deficiency impaired cellular motility and invasive ability even after TGF-β-induced EMT induction.

Conclusions

These results suggested that, while PDPN seems to function in favor of maintaining the epithelial state of this cell line, it is indispensable for platelet-mediated induction of particular mesenchymal marker genes as well as the potentiation of motility and invasion capacity.

Inhibition of plasminogen activator inhibitor-1 attenuates against intestinal fibrosis in mice

Background/Aims

Intestinal fibrosis is a major complication of Crohn’s disease (CD). The profibrotic protein transforming growth factor-β (TGF-β) has been considered to be critical for the induction of the fibrotic program. TGF-β has the ability to induce not only the expression of extracellular matrix (ECM) including collagen, but also the production of plasminogen activator inhibitor-1 (PAI-1) that prevents enzymatic degradation of the ECM during the onset of fibrotic diseases. However, the significance of PAI-1 in the developing intestinal fibrosis has not been fully understood. In the present study, we examined the actual expression of PAI-1 in fibrotic legion of intestinal inflammation and its correlation with the abnormal ECM deposition.

Methods

Chronic intestinal inflammation was induced in BALB/c mice using 8 repeated intrarectal injections of 2,4,6-trinitrobenzene sulfonic acid (TNBS). TM5275, a PAI-1 inhibitor, was orally administered as a carboxymethyl cellulose suspension each day for 2 weeks after the sixth TNBS injection.

Results

Using a publicly available dataset (accession number, GSE75214) and TNBS-treated mice, we observed increases in PAI-1 transcripts at active fibrotic lesions in both patients with CD and mice with chronic intestinal inflammation. Oral administration of TM5275 immediately after the onset of intestinal fibrosis upregulated MMP-9 (matrix metalloproteinase 9) and decreased collagen accumulation, resulting in attenuation of the fibrogenesis in TNBS-treated mice.

Conclusions

PAI-1-mediated fibrinolytic system facilitates collagen degradation suppression. Hence, PAI-1 inhibitor could be applied as an anti-fibrotic drug in CD treatment.

Blockade of plasminogen activator inhibitor-1 empties bone marrow niche sufficient for donor hematopoietic stem cell engraftment without myeloablative conditioning

Upon hematopoietic stem cell transplantation (HSCT), the availability of recipients' niches in the bone marrow (BM) is one of the factors that influence donor HSC engraftment and hematopoietic reconstitution. Therefore, myeloablative conditioning, such as irradiation and/or chemotherapy, which creates empty niches in the recipients' BM, is required for the success of HSCT. However, the conventional myeloablation causes extensive damages to the patients' BM, which results in the treatment-induced severe complications and even mortality. Thus, alternative and mild conditioning could fulfill the need for safer HSCT-based therapies for hematological and nonhematological disorders. Recently, we have demonstrated that pharmacological inhibition of plasminogen activator inhibitor-1 (PAI-1) activity increases cellular motility and cause detachment of HSCs from the niches. In this study, we performed HSCT using a PAI-1 inhibitor without any myeloablative conditioning. Donor HSCs were transplanted to recipient mice that were pretreated with saline or a PAI-1 inhibitor. Saline pretreated nonmyeloablative recipients showed no engraftment. In contrast, donor cell engraftment was detected in the PAI-1 inhibitor pretreated recipients. Multilineage differentiation, including lymphoid and myeloid cells, was observed in the PAI-1 inhibitor pretreated recipients. Donor-derived cells that exhibited multilineage reconstitution as well as the existence of stem/progenitor cells were detected in the secondary recipients, confirming the maintenance of donor HSCs in the BM of PAI-1 inhibitor pretreated primary recipients. The results indicate that the PAI-1 blockade vacates functional niches in the recipients' BM, which allows the engraftment of long-term multilineage HSCs without myeloablative conditioning.

Comparison of the Gene Expression Profiles of Human Hematopoietic Stem Cells between Humans and a Humanized Xenograft Model

The aim of this study is to evaluate the feasibility of NOD/Shi-scid-IL2Rγ^null(NOG) mice transplanted with human CD34⁺/CD38^-/Lin^-/low hematopoietic cells from cord blood (CB) as an experimental model of the gene expression in human hematopoiesis. We compared the gene expressions of human CD34⁺/CD38^-/Lin^-/low cells from human bone marrow (BM) and in xenograft models. The microarray data revealed that 25 KEGG pathways were extracted from the comparison of human CD34⁺/CD38^-/Lin^-/low HSCs between CB and BM, and that 17 of them--which were mostly related to cellular survival, RNA metabolism and lymphoid development--were shared with the xenograft model. When the probes that were commonly altered in CD34⁺/CD38^-/Lin^-/low cells from both human and xenograft BM were analyzed, most of them, including the genes related hypoxia, hematopoietic differentiation, epigenetic modification, translation initiation, and RNA degradation, were downregulated. These alterations of gene expression suggest a reduced differentiation capacity and likely include key alterations of gene expression for settlement of CB CD34⁺/CD38^-/Lin^-/low cells in BM. Our findings demonstrate that the xenograft model of human CB CD34⁺/CD38^-/Lin^-/low cells using NOG mice was useful, at least in part, for the evaluation of the gene expression profile of human hematopoietic stem cells.

Maintenance of Bone Homeostasis by DLL1-Mediated Notch Signaling

Adult bone mass is maintained through a balance of the activities of osteoblasts and osteoclasts. Although Notch signaling has been shown to maintain bone homeostasis by controlling the commitment, differentiation, and function of cells in both the osteoblast and osteoclast lineages, the precise mechanisms by which Notch performs such diverse and complex roles in bone physiology remain unclear. By using a transgenic approach that modified the expression of delta‐like 1 (DLL1) or Jagged1 (JAG1) in an osteoblast‐specific manner, we investigated the ligand‐specific effects of Notch signaling in bone homeostasis. This study demonstrated for the first time that the proper regulation of DLL1 expression, but not JAG1 expression, in osteoblasts is essential for the maintenance of bone remodeling. DLL1‐induced Notch signaling was responsible for the expansion of the bone‐forming cell pool by promoting the proliferation of committed but immature osteoblasts. However, DLL1‐Notch signaling inhibited further differentiation of the expanded osteoblasts to become fully matured functional osteoblasts, thereby substantially decreasing bone formation. Osteoblast‐specific expression of DLL1 did not alter the intrinsic differentiation ability of cells of the osteoclast lineage. However, maturational arrest of osteoblasts caused by the DLL1 transgene impaired the maturation and function of osteoclasts due to a failed osteoblast‐osteoclast coupling, resulting in severe suppression of bone metabolic turnover. Taken together, DLL1‐mediated Notch signaling is critical for proper bone remodeling as it regulates the differentiation and function of both osteoblasts and osteoclasts. Our study elucidates the importance of ligand‐specific activation of Notch signaling in the maintenance of bone homeostasis. J. Cell. Physiol. 232: 2569–2580, 2017. © 2016 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals Inc.

Common marmoset CD117+ hematopoietic cells possess multipotency

Analysis of the hematopoiesis of non-human primates is important to clarify the evolution of primate-specific hematopoiesis and immune regulation. However, the engraftment and development of the primate hematopoietic system are well-documented only in humans and are not clear in non-human primates. Callithrix jacchus (common marmoset, CM) is a New World monkey with a high rate of pregnancy and small size that lives in closed colonies. As stem cell factor (SCF) is an essential molecule for hematopoietic stem cell development in mice and humans, we focused on CD117, the SCF receptor, and examined whether CD117-expressing cells possess the hematopoietic stem/progenitor cell characteristics of newborn marmoset-derived hematopoietic cells that can develop into T cells and B cells. When CD117(+) cell fractions of the bone marrow were transplanted into immunodeficient NOD (non-obese diabetic)/Shi-scid, common γc-null (NOG) mice, these cells engrafted efficiently in the bone marrow and spleens of the NOG mice. The CD117(+) cells developed into myeloid lineage cells, CD20(+) B cells and CD3(+) T cells, which could express CM cytokines in vivo. The development of B cells did not precede that of T cells. The development of CD8(+) T cells was dominant in NOG mice. The engraftment was comparable for both CD117(+)CD34(+) cells and CD117(+)CD34(-) cells. These results suggest that the CD117(+) cell fraction can differentiate into all three cell lineages, and the development of marmoset immunity in the xenogeneic environment follows diverse developmental pathways compared with human immunity.

Inhibition of plasminogen activator inhibitor type-1 activity enhances rapid and sustainable hematopoietic regeneration

The prognosis of patients undergoing hematopoietic stem cell transplantation (HSCT) depends on the rapid recovery and sustained life-long hematopoiesis. The activation of the fibrinolytic pathway promotes hematopoietic regeneration; however, the role of plasminogen activator inhibitor-1 (PAI-1), a negative regulator of the fibrinolytic pathway, has not yet been elucidated. We herein demonstrate that bone marrow (BM) stromal cells, especially osteoblasts, produce PAI-1 in response to myeloablation, which negatively regulates the hematopoietic regeneration in the BM microenvironment. Total body irradiation in mice dramatically increased the local expression levels of fibrinolytic factors, including tissue-type plasminogen activator (tPA), plasmin, and PAI-1. Genetic disruption of the PAI-1 gene, or pharmacological inhibition of PAI-1 activity, significantly improved the myeloablation-related mortality and promoted rapid hematopoietic recovery after HSCT through the induction of hematopoiesis-promoting factors. The ability of a PAI-1 inhibitor to enhance hematopoietic regeneration was abolished when tPA-deficient mice were used as recipients, thus indicating that PAI-1 represses tPA-dependent hematopoietic regeneration. The PAI-1 inhibitor not only accelerated the expansion of the donor HSCs during the early-stage of regeneration, but also supported long-term hematopoiesis. Our results indicate that the inhibition of PAI-1 activity could be a therapeutic approach to facilitate the rapid recovery and sustained hematopoiesis after HSCT.

Effective expansion of engrafted human hematopoietic stem cells in bone marrow of mice expressing human Jagged1

The human immune system can be reconstituted in experimental animals by transplanting human hematopoietic stem cells (hHSCs) into immunodeficient mice. To generate such humanized mice, further improvements are required, particularly to ensure that transplanted hHSCs are maintained in mice and proliferate long enough to follow prolonged immune responses to chronic diseases or monitor therapeutic effects. To prepare the relatively human bone marrow environment in mice, we generated nonobese diabetic/severe combined immunodeficiency/interleukin-2 receptor gamma chain null (NOG) mice expressing human Jagged1 (hJ1) in an osteoblast-specific manner (hJ1-NOG mice) to examine whether Notch signaling induced by hJ1 mediates hHSC proliferation and/or maintenance in mice. The established hJ1-NOG mice possess relatively larger bone marrow space and thinner cortical bone compared with nontransgenic littermates, but the number of c-kit(+) Sca-1(+) lineage(-) cells was not significantly different between hJ1-NOG and nontransgenic littermates. In the transplantation experiments of CD34(+) cells obtained from human cord blood, CD34(+)CD38(-) cells (hHSCs) were more increased in hJ1-NOG recipient mice than in nontransgenic littermates in mouse bone marrow environment. In contrast, the transplanted mouse c-kit(+) Sca-1(+) lineage(-) cells did not show significant increase in the same hJ1-NOG mice. These results suggest that hJ1-NOG mice could contribute to the growth of transplanted human CD34(+) cells in a human-specific manner and be useful to study the in vivo behavior and/or development of human stem cells, including cancer stem cells and immune cells.

Severe Asherman's syndrome complicated with placenta increta conceived by intracytoplasmic sperm injection following hysteroscopic surgery

Although severe Asherman's syndrome is a disease that may cause infertility, pregnancy and childbirth are possible by performing hysteroscopic surgery. However, the obstetrical outcome is not always satisfactory. We report a case where severe Asherman's syndrome occurred following a cesarean section. Hysteroscopic surgery was performed due to secondary infertility, and pregnancy was achieved through a subsequent intracytoplasmic sperm injection. At 23 weeks of gestation, the patient was hospitalized due to the threat of premature labor, and a cesarean section was performed at 29 weeks of gestation after pregnancy-induced hypertension occurred. It was determined to be abnormal adherent placentation such as placenta increta through intraoperative findings, and a cesarean hysterectomy was performed. The pathological diagnosis of the uterus was placenta increta. Due to the risk of complications from placenta increta in pregnancies following hysteroscopic surgery in patients with severe Asherman's syndrome, it is important to realize the high risk involved in such cases during the pregnancy course, and careful perinatal management should be required.

Trends in the incidence of uterine cancer in Niigata, Japan: a population-based study from 1982 to 2007

This study investigated trends in the incidence of uterine cancer in Japan. Data from the Gynecological Cancer Registry of Niigata comprising all new cases of uterine cancer registered for the entire female population aged 15 years and over a 25-year period were examined. The age-standardized ratio of carcinoma in situ has substantially increased among females < 40 years of age (from 3.8 (in the period of 1982-1989) to 40.9 (2000-2007). There was a significant trend in increasing incidence of invasive cervical cancer for those < 40 years of age (from 4.7 to 13.1), whereas a significant trend of decreasing incidence for the 50+ year age group. The ratios of corpus cancer were increased approximately two-folds both among the population aged < 50 years and those aged 50+ years and thus becoming equivalent to invasive cervical cancer. This prefecture-wide population-based study shows the practical trend in uterine cancer in Japanese females. The current health service must emphasize education among young adults concerning cervical cancer prevention while concentrating on screening. Avoiding risk factors, such as obesity, and increasing protective factors may lower risk for corpus cancer both in younger and older females.

Establishment of a xenograft model of human myelodysplastic syndromes

BACKGROUND

To understand how myelodysplastic syndrome cells evolve from normal stem cells and gain competitive advantages over normal hematopoiesis, we established a murine xenograft model harboring bone marrow cells from patients with myelodysplastic syndromes or acute myeloid leukemia with myelodysplasia-related changes.

DESIGN AND METHODS

Bone marrow CD34(+) cells obtained from patients were injected, with or without human mesenchymal stem cells, into the bone marrow of non-obese diabetic/severe combined immunodeficient/IL2Rγ(null) hosts. Engraftment and differentiation of cells derived from the patients were investigated by flow cytometry and immunohistochemical analysis.

RESULTS

Co-injection of patients' cells and human mesenchymal stem cells led to successful engraftment of patient-derived cells that maintained the immunophenotypes and genomic abnormalities of the original patients. Myelodysplastic syndrome-originated clones differentiated into mature neutrophils, megakaryocytes, and erythroblasts. Two of the samples derived from patients with acute myeloid leukemia with myelodysplasia-related changes were able to sustain neoplastic growth into the next generation while these cells had limited differentiation ability in the murine host. The hematopoiesis of mice engrafted with patients' cells was significantly suppressed even when human cells accounted for less than 1% of total marrow mononuclear cells. Histological studies revealed invasion of the endosteal surface by patient-derived CD34(+) cells and disruption of extracellular matrix architecture, which probably caused inhibition of murine hematopoiesis.

CONCLUSIONS

We established murine models of human myelodysplastic syndromes using cells obtained from patients: the presence of neoplastic cells was associated with the suppression of normal host hematopoiesis. The efficiency of engraftment was related to the presence of an abnormality in chromosome 7.

Adipose tissue-derived mesenchymal stem cells facilitate hematopoiesis in vitro and in vivo: advantages over bone marrow-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) have emerged as a new therapeutic modality for reconstituting the hematopoietic microenvironment by improving engraftment in stem cell transplantation. However, the availability of conventional bone marrow (BM)-derived MSCs (BMSCs) is limited. Recent studies showed that a large number of MSCs can be easily isolated from fat tissue (adipose tissue-derived MSCs [ADSCs]). In this study, we extensively evaluated the hematopoiesis-supporting properties of ADSCs, which are largely unknown. In vitro coculture and progenitor assays showed that ADSCs generated significantly more granulocytes and progenitor cells from human hematopoietic stem cells (HSCs) than BMSCs. We found that ADSCs express the chemokine CXCL12, a critical regulator of hematopoiesis, at levels that are three fold higher than those with BMSCs. The addition of a CXCL12 receptor antagonist resulted in a lower yield of granulocytes from ADSC layers, whereas the addition of recombinant CXCL12 to BMSC cocultures promoted the growth of granulocytes. In vivo cell homing assays showed that ADSCs facilitated the homing of mouse HSCs to the BM better than BMSCs. ADSCs injected into the BM cavity of fatally irradiated mice reconstituted hematopoiesis more promptly than BMSCs and subsequently rescued mice that had received a low number of HSCs. Secondary transplantation experiments showed that ADSCs exerted favorable effects on long-term HSCs. These results suggest that ADSCs can be a promising therapeutic alternative to BMSCs.

Delta-like 4 is indispensable in thymic environment specific for T cell development

The thymic microenvironment is required for T cell development in vivo. However, in vitro studies have shown that when hematopoietic progenitors acquire Notch signaling via Delta-like (Dll)1 or Dll4, they differentiate into the T cell lineage in the absence of a thymic microenvironment. It is not clear, however, whether the thymus supports T cell development specifically by providing Notch signaling. To address this issue, we generated mice with a loxP-flanked allele of Dll4 and induced gene deletion specifically in thymic epithelial cells (TECs). In the thymus of mutant mice, the expression of Dll4 was abrogated on the epithelium, and the proportion of hematopoietic cells bearing the intracellular fragment of Notch1 (ICN1) was markedly decreased. Corresponding to this, CD4 CD8 double-positive or single-positive T cells were not detected in the thymus. Further analysis showed that the double-negative cell fraction was lacking T cell progenitors. The enforced expression of ICN1 in hematopoietic progenitors restored thymic T cell differentiation, even when the TECs were deficient in Dll4. These results indicate that the thymus-specific environment for determining T cell fate indispensably requires Dll4 expression to induce Notch signaling in the thymic immigrant cells.

Expression of Delta-like 1 in the splenic non-hematopoietic cells is essential for marginal zone B cell development

The Notch ligand Delta-like 1 (Dll1) is critical for the generation of marginal zone (MZ) B cells in the spleen. However, the precise mechanism underlying the differentiation of MZB cells is unclear. To determine whether hematopoietic cells or non-hematopoietic cells provides the Dll1-mediated signals to primitive hematopoietic cells, we transplanted lineage(-)c-kit(+)Sca-1(+) (KSL) bone marrow cells derived from wild-type (Dll1(+/+)) GFP-transgenic mice into lethally irradiated Dll1 conditional knockout (cKO) mice. After transplantation, we examined the kinetics of hematopoietic reconstitution and found that although the frequency of stem/progenitor subsets and of more mature lymphoid, myeloid, and erythroid lineages were normal, the donor-derived hematopoietic cells failed to differentiate into MZB cells. We further demonstrated that while the splenic stromal cells of wild-type mice expressed Dll1 molecule, the splenic stromal cells of recipient Dll1 cKO mice deleted the expression of Dll1. These results suggesting that the expression of Dll1 in splenic non-hematopoietic stromal cells, but not hematopoietic cells, is essential for the development of MZB cells.

Primary retroperitoneal mucinous cystadenocarcinoma associated with pregnancy

Primary retroperitoneal mucinous cystadenocarcinoma (PRMC) is an extremely rare tumor. Only 30 cases have been reported previously in the English literature, and little information is available concerning its treatment and prognosis. The patient was a 28-year-old woman, presenting with a right mid-abdominal tumor at 26 weeks of gestation. At 31 weeks of gestation, she underwent an exploratory laparotomy and was diagnosed with a PRMC. No disseminated tumor was observed, and an excision of only the tumor was performed. She had an uneventful vaginal delivery at 38 weeks of gestation and remains free of disease at 13 months after the operation. This report describes a case of PRMC associated with pregnancy. The optimal management of these retroperitoneal masses during pregnancy is discussed. Based on limited experience and the current literature, a PRMC with an intact capsule and no dissemination appears to have a good prognosis and can be treated by tumor excision alone in patients who wish to preserve fertility

Humanizing bone marrow in immune-deficient mice

Humanized mice are useful for studying human hematopoietic stem cells (HSCs) and their niche. In particular, clonal study of human HSC enables precise comparison of in vivo behavior between murine and human HSCs. A single HSC is able to reconstitute hematopoiesis even after serial transplantations in mice. While the life span of somatic cells is over that of individual in mice, this is not the case in humans. Clonal studies of human HSCs clearly demonstrated their aging in hosts. Since murine studies have demonstrated that HSCs are protected from aging by their niche in bone marrow, the humanizing niche model will reveal the precise mechanism by which human HSCs are protected from exhaustion in vivo. Direct transplantation of human mesenchymal stem cells into mouse bone marrow results in reconstitution of the functional human hematopoietic microenvironment comprised of pericytes, myofibroblasts, reticular cells, osteocytes in bone, bone-lining osteoblasts, and endothelial cells. These humanized mouse models are essential for testing whether the insights on hematopoiesis from mouse studies are applicable to humans before clinical application.

Angiopoietin-1 supports induction of hematopoietic activity in human CD34- bone marrow cells

OBJECTIVE

Hematopoietic stem cells (HSCs) consist of heterogenous subpopulations, one of which is CD34(-) HSCs. Recent development of successful engraftment by intra-bone marrow transplantation revealed severe combined immunodeficiency (scid) mouse-repopulating cell (SRC) activity in human CD34(-) cord blood (CB) cells. On the other hand, CD34(-) cells from bone marrow (BM) cells remain relatively undefined. Here, we investigated pre-SRC populations in human BM CD34(-) cells and the effect of the niche-related factor, angiopoietin-1, on them.

METHODS

Two populations in BM CD34(-) cells (namely M cells and S cells) were purified by flow cytometry. Then, they were cocultured with six growth factors on the hematopoietic-supportive mouse BM stromal cell line, HESS-5 or AHESS-5 that were engineered to produce human angiopoietin-1, because we detected Tie2 expression on M cells and S cells. Cultured cells were assessed for their in vitro and in vivo hematopietic activities.

RESULTS

After 7 days in coculture, AHESS-5 was stronger more effective than HESS-5 in converting M and S cells to CD34(+) cells (M cells: 67.4% vs 17.5%, n =6, p < 0.001) (S cells: 42.3% vs 2.3%, n = 6, p < 0.001). Furthermore, both M and S cells were able to engraft in immunodeficient mice after they were cocultured on AHESS-5.

CONCLUSIONS

Results suggest that angiopoietin-1 supports SRC activities in human CD34(-) BM cells, as murine studies demonstrated. Furthermore, identification of previously undetected subpopulations of BM CD34(-) HSCs unveils heterogenous components in the stem cell pool.

Prediction of myometrial invasion in patients with endometrial carcinoma: comparison of magnetic resonance imaging, transvaginal ultrasonography, and gross visual inspection

This study evaluated the accuracy of magnetic resonance imaging (MRI) and transvaginal ultrasonography (TVUS) in preoperative detection of myometrial invasion by endometrial cancer. We also evaluated the results of gross visual inspection (GVI) of surgical specimens compared with histopathological diagnosis. One hundred and seventy-seven women underwent preoperative pelvic MRI, TVUS, and intraoperative GVI. Myometrial tumor invasion was evaluated histologically and classified as absent (depth a), superficial (depth b: < or = 50% invasion), or deep (depth c: > 50% invasion). The accuracy of MRI, TVUS, and GVI were 64.0, 66.9, and 63.8%, respectively. The positive predictive values of of each modality for depth a were 52.6, 51.4, and 52.2%, respectively. The accuracy of each in detecting deep myometrial invasion (depth c) were 84.0, 86.9, 83.1%. Although evaluation of depth a was limited with all modalities, MRI and TVUS were shown to be reliable for preoperative evaluation of deep myometrial invasion. The high accuracy of these three methods suggests that they are useful either interchangeably or in combination.

Clonal analysis of thymus-repopulating cells presents direct evidence for self-renewal division of human hematopoietic stem cells

To elucidate the in vivo kinetics of human hematopoietic stem cells (HSCs), CD34+CD38– cells were infected with lentivirus vector and transplanted into immunodeficient mice. We analyzed the multilineage differentiation and self-renewal abilities of individual thymus-repopulating clones in primary recipients, and their descending clones in paired secondary recipients, by tracing lentivirus gene integration sites in each lymphomyeloid progeny using a linear amplification-mediated polymerase chain reaction (PCR) strategy. Our clonal analysis revealed that a single human thymus-repopulating cell had the ability to produce lymphoid and myeloid lineage cells in the primary recipient and each secondary recipient, indicating that individual human HSCs expand clonally by self-renewal division. Furthermore, we found that the proportion of HSC clones present in the CD34+ cell population decreased as HSCs replicated during extensive repopulation and also as the differentiation capacity of the HSC clones became limited. This indicates the restriction of the ability of individual HSCs despite the expansion of total HSC population. We also demonstrated that the extensive self-renewal potential was confined in the relatively small proportion of HSC clones. We conclude that our clonal tracking studies clearly demonstrated that heterogeneity in the self-renewal capacity of HSC clones underlies the differences in clonal longevity in the CD34+ stem cell pool.

Radiation myelopathy after radioactive iodine therapy for spine metastasis

A case of radiation myelopathy after radioactive iodine therapy is reported. This is the first report to describe radiation myelopathy after I-131 therapy. A 62-year-old female with spinal metastasis of T10 received I-131 therapy. She presented with radiation myelopathy 34 months after the irradiation. We need to recognize the possibility of this serious complication even in the case of I-131 therapy. There is a risk of radiation myelopathy even after I-131 therapy, especially in cases with spinal cord compression such as this.

Expression of CD90 on keratinocyte stem/progenitor cells

BACKGROUND

The identification and purification of keratinocyte stem cells (KSCs) that are capable of self-renewal and maintenance of differentiating cell populations could contribute both to our understanding of the biology of these cells, and to significant clinical applications, such as the culturing of keratinocytes for transplantation to severe burn wounds. Here, we report the detection of CD90(+) cells in cultured normal human epidermal keratinocytes and adult skin.

OBJECTIVES

To investigate the biological function of CD90(+) and CD90(-) keratinocytes.

METHODS

CD90(+) and CD90(-) keratinocytes were purified from adult skin and cultured keratinocytes using fluorescent activated cell sorting, and their biological abilities were analysed using both in vitro and in vivo assays.

RESULTS

Flow cytometry (FCM) analysis identified approximately 18% of post-primary neonatal keratinocytes as CD90(+). However, during expansion of the culture, the expression level of CD90 rapidly decreased to about 2.5% at passage 10, while most of the keratinocytes maintained expression of alpha6 integrin. Purified CD90(+) keratinocytes demonstrated a sixfold higher cell growth rate than CD90(-) cells and the ability to form large (over 3 mm in diameter) colonies. We then quantitatively evaluated both populations using a previously described in vivo human epidermal cyst formation assay. Enhanced green fluorescent protein (EGFP)-labelled CD90(+) or CD90(-) keratinocytes were subcutaneously injected into nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. Six weeks after transplantation, EGFP(+) cell clusters in human epidermal cysts were evaluated using image analysis software. EGFP(+) cell cluster areas in the basal layer, derived from EGFP(+) CD90(+) cells, were eightfold larger than clusters of EGFP(+) CD90(-) cells. Furthermore, immunohistochemical staining and FCM analysis indicated that CD90 was expressed in most of the basal layer of the normal human epidermis.

CONCLUSIONS

These results indicated that CD90 is a useful marker for the detection of human KSC-enriched populations in cultured human keratinocytes.

Reconstitution of the functional human hematopoietic microenvironment derived from human mesenchymal stem cells in the murine bone marrow compartment

Hematopoiesis is maintained by specific interactions between both hematopoietic and nonhematopoietic cells. Whereas hematopoietic stem cells (HSCs) have been extensively studied both in vitro and in vivo, little is known about the in vivo characteristics of stem cells of the nonhematopoietic component, known as mesenchymal stem cells (MSCs). Here we have visualized and characterized human MSCs in vivo following intramedullary transplantation of enhanced green fluorescent protein-marked human MSCs (eGFP-MSCs) into the bone marrow (BM) of nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice. Between 4 to 10 weeks after transplantation, eGFP-MSCs that engrafted in murine BM integrated into the hematopoietic microenvironment (HME) of the host mouse. They differentiated into pericytes, myofibroblasts, BM stromal cells, osteocytes in bone, bone-lining osteoblasts, and endothelial cells, which constituted the functional components of the BM HME. The presence of human MSCs in murine BM resulted in an increase in functionally and phenotypically primitive human hematopoietic cells. Human MSC-derived cells that reconstituted the HME appeared to contribute to the maintenance of human hematopoiesis by actively interacting with primitive human hematopoietic cells.

Direct evidence for ex vivo expansion of human hematopoietic stem cells

To characterize human hematopoietic stem cells (HSCs), xenotransplantation techniques such as the severe combined immunodeficiency (SCID) mouse repopulating cell (SRC) assay have proven the most reliable methods thus far. While SRC quantification by limiting dilution analysis (LDA) is the gold standard for measuring in vitro expansion of human HSCs, LDA is a statistical method and does not directly establish that a single HSC has self-renewed in vitro. This would require a direct clonal method and has not been done. By using lentiviral gene marking and direct intra-bone marrow injection of cultured CD34+ CB cells, we demonstrate here the first direct evidence for self-renewal of individual SRC clones in vitro. Of 74 clones analyzed, 20 clones (27%) divided and repopulated in more than 2 mice after serum-free and stroma-dependent culture. Some of the clones were secondary transplantable. This indicates symmetric self-renewal divisions in vitro. On the other hand, 54 clones (73%) present in only 1 mouse may result from asymmetric divisions in vitro. Our data demonstrate that current ex vivo expansion conditions result in reliable stem cell expansion and the clonal tracking we have employed is the only reliable method that can be used in the development of clinically appropriate expansion methods.

Long-term conservative therapy for endometrial adenocarcinoma in young women

BACKGROUND

To evaluate the efficacy and safety of long-term conservative therapy with medroxyprogesterone acetate (MPA) for endometrial carcinoma in young patients who had experienced failure after initial therapy or relapse, we reviewed the clinical and pathologic records of eight patients diagnosed with well-differentiated endometrial adenocarcinoma without myometrial invasion who were treated with MPA for over 6 months because of treatment failure or relapse.

RESULTS

The average duration of MPA treatment was 22 months. All patients were followed-up for a mean of 76.5 months. Seven patients responded to initial MPA treatment within a period of 14 months (mean, 7.9 months). All these patients experienced relapse and the mean time to relapse was 11.6 months (range, 4-33 months). All six patients with relapse were treated with additional treatments of MPA, and all but one responded to this treatment within a period of 16 months (mean, 8.0 months). Six patients ultimately underwent hysterectomy. All presented well-differentiated endometrioid adenocarcinomas without extrauterine disease. Three became pregnant and two delivered full-term normal infants. No patient died of the disease.

CONCLUSION

Although lesions are expected to disappear with prolonged MPA treatment, this form of progestin therapy is hazardous because recurrence occurs frequently. Only strictly selected patients should therefore be indicated for long-term MPA treatment and careful evaluation before and after treatment should be performed.

Complete response to docetaxel and carboplatin combination chemotherapy for a stage IV uterine papillary serous carcinoma: a case report

We report a case of a stage IV uterine papillary serous carcinoma (UPSC) with multiple organ metastases. The patient was treated with docetaxel and carboplatin combination chemotherapy. After five courses, uterine tumor, Douglas tumor, lymphadenopathy, and distant metastases on magnetic resonance imaging or computed tomography scan were completely resoluted. Moreover, endometrial biopsy showed no carcinoma tissues after six courses. We suggest that this regimen may be effective for treatment of advanced-stage UPSC.

Association between single nucleotide polymorphisms of estrogen receptor alpha gene and efficacy of HRT on bone mineral density in post-menopausal Japanese women

BACKGROUND

Although HRT for post-menopausal women can protect against bone loss, variations in bone responses exist. We studied whether single nucleotide polymorphisms (SNP) of the estrogen receptor-alpha (ERalpha) gene contribute to the effect of HRT on lumbar spine bone mineral density (BMD).

METHODS

Subjects were 84 post-menopausal women who had been taking HRT for 3 years to treat osteopenia or osteoporosis. Eighteen SNP in the ERalpha gene were characterized by a single nucleotide primer extension assay.

RESULTS

Genotyping of the 84 individuals revealed that all SNP were quite common, the minor allele frequency being > or = 20%. A SNP in intron 6 (IVS6+14144) was significantly associated with the response to HRT for the first 3 years after starting treatment (P = 0.043, 0.025 and 0.032 for the first, second and third years respectively). Haplotype analysis revealed that a combination of SNP IVS6+14144 and IVS4+4238 was significantly correlated with the response to HRT; women with haplotype G-G (IVS6 14144-IVS4 4238) showed a significantly higher response (P = 0.014, 0.043 and 0.010 for the first second and third year respectively).

CONCLUSIONS

These results suggest that a specific SNP and the haplotype of the selected SNP could be used to predict the effect of HRT on lumbar BMD.

Placental site trophoblastic tumor presenting as subaponeurotic metastasis

Cases of metastatic placental site trophoblastic tumor (PSTT) have a very poor prognosis because these tumors tend to be less sensitive to chemotherapy than other types of gestational trophoblastic disease. We describe the case of a 25-year-old woman who presented with occipital tumor and abnormal vaginal bleeding. Hysterectomy, bilateral salpingo-oophorectomy, and occipital tumor removal revealed a primary PSTT in the uterus, with ovarian and occipital subaponeurotic metastases. She received etoposide, methotrexate, actinomycin-D/cyclophosphamide, vincristine chemotherapy and had a complete clinical remission. Fifteen months later, she had a recurrent subaponeurotic occipital tumor invading the cranium and underwent tumor removal along with cranial bone followed by local irradiation. She was then treated with etoposide, cis-platinum/etoposide, methotrexate, actinomycin-D chemotherapy and again had a remission for 5 months. The patient, however, had a left parietal subaponeurotic tumor, invading the dura mater, and received local irradiation. Soon after, she developed left orbital bone metastasis, treated by local irradiation. These bone metastases responded to the radiation completely. However, multiple organ metastases were found, and she died of the disease. This represents the first case of PSTT with initial subaponeurotic metastasis in a living patient. New modalities of treatment for high-risk or metastatic PSTT need to be developed.

Cytoplasmic and mitochondrial Ca2+ levels in brown adipocytes

AIM

We elucidated the mitochondrial functions of brown adipocytes in intracellular signalling, paying attention to mitochondrial activity and noradrenaline- and forskolin-induced Ca(2+) mobilizations in cold-acclimated rats.

METHODS

A confocal laser-scanning microscope of brown adipocytes from warm- or cold-acclimated rats was employed using probes rhodamine 123 which is a mitochondria-specific cationic dye, and the cytoplasmic and mitochondrial Ca(2+) probes fluo-3 and rhod-2. X-ray microanalysis was also studied.

RESULTS

The signal of rhodamine 123 in the cells was decreased by antimycin A which effect was less in cold-acclimated cells than warm-acclimated cells. Cytoplasmic and mitochondrial Ca(2+) in cold-acclimated brown adipocytes double-loaded with fluo-3 and rhod-2 were measured. Noradrenaline induced the rise in cytoplasmic Ca(2+) ([Ca(2+)](cyto)) followed by mitochondrial Ca(2+) ([Ca(2+)](mito)), the effect being transformed into an increase in [Ca(2+)](cyto) whereas a decrease in [Ca(2+)](mito) by antimycin A or carbonyl cyanide m-chlorophenylhydrazone (CCCP). Antimycin A induced small Ca(2+) release from mitochondria. CCCP induced Ca(2+) release from mitochondria only after the cells were stimulated with noradrenaline. Further, forskolin also elicited an elevation in [Ca(2+)](cyto) followed by [Ca(2+)](mito) in the cells. The Ca measured by X-ray microanalysis was higher both in the cytoplasm and mitochondria whereas K was higher in the mitochondria of cold-acclimated cells in comparison to warm-acclimated cells.

CONCLUSIONS

These results suggest that noradrenaline and forskolin evoked an elevation in [Ca(2+)](cyto) followed by [Ca(2+)](mito), in which H(+) gradient across the inner membrane is responsible for the accumulation of calcium on mitochondria. Moreover, cAMP also plays a role in intracellular and mitochondrial Ca(2+) signalling in cold-acclimated brown adipocytes.

Placental site trophoblastic tumor presenting as subaponeurotic metastasis

Cases of metastatic placental site trophoblastic tumor (PSTT) have a very poor prognosis because these tumors tend to be less sensitive to chemotherapy than other types of gestational trophoblastic disease. We describe the case of a 25-year-old woman who presented with occipital tumor and abnormal vaginal bleeding. Hysterectomy, bilateral salpingo-oophorectomy, and occipital tumor removal revealed a primary PSTT in the uterus, with ovarian and occipital subaponeurotic metastases. She received etoposide, methotrexate, actinomycin-D/cyclophosphamide, vincristine chemotherapy and had a complete clinical remission. Fifteen months later, she had a recurrent subaponeurotic occipital tumor invading the cranium and underwent tumor removal along with cranial bone followed by local irradiation. She was then treated with etoposide, cis-platinum/etoposide, methotrexate, actinomycin-D chemotherapy and again had a remission for 5 months. The patient, however, had a left parietal subaponeurotic tumor, invading the dura mater, and received local irradiation. Soon after, she developed left orbital bone metastasis, treated by local irradiation. These bone metastases responded to the radiation completely. However, multiple organ metastases were found, and she died of the disease. This represents the first case of PSTT with initial subaponeurotic metastasis in a living patient. New modalities of treatment for high-risk or metastatic PSTT need to be developed

Competitive Repopulation Assay of Two Gene-Marked Cord Blood Units in NOD/SCID/γcnull Mice

In multiunit cord blood transplantation, hematopoietic stem cells from each unrelated cord blood (UCB) unit competitively reconstitute the hematopoietic system in a recipient. To evaluate the fate of the progeny of each UCB unit and to determine the effects of graft-versus-graft reaction, we established a novel competitive repopulation assay using NOD/SCID/gammac(null) mice in which human T lymphocytes develop from CD34+ cells. CD34+ cells from each UCB unit were labeled with recombinant lentivirus vectors carrying genes encoding either enhanced green fluorescent protein (EGFP) or enhanced yellow fluorescent protein (EYFP). Hematopoietic chimerism composed of both EGFP+ and EYFP+ cells was stably maintained up to 6 months after transplantation with purified CD34+ cells; the ratio of EGFP+ to EYFP+ cells in peripheral blood and bone marrow posttransplantation was equivalent to the ratio of these cells at transplantation. However, when mononuclear cells from two UCB units were cotransplanted with CD34+ cells, engraftment was highly competitive, with cells from only one or the other of the two UCB units surviving. Further subfractionations of mononuclear cells indicate that the skewed chimerism that is often observed in clinical multiunit cord blood transplantation may be mediated by the cooperation of both CD4+ and CD8+ T cells. The assay established here will be a useful tool for analyzing hematopoietic reconstitution in clinical multiunit cord blood transplantation.

In vivo and in vitro differentiation of myocytes from human bone marrow-derived multipotent progenitor cells

OBJECTIVE

Recent studies have shown that bone marrow (BM) contains cells capable of differentiating into myocytes in vivo. However, addition of demethylation drugs has been necessary to induce myocyte differentiation from BM cells in vitro, and precise mechanisms of BM cells' conversion to myocytes and the origin of those cells have not been established. We investigated the expression of myogenic markers during differentiation and maturation of myocytes from BM-derived multipotent adult progenitor cells (MAPC) under physiological culture condition.

MATERIALS AND METHODS

Frozen BM samples from 21 healthy donors were used as a source of MAPC. To induce myocyte differentiation MAPC was cultured in the presence of 5% FCS, VEGF, bFGF, and IGF-1, and the expressions of myocyte markers were examined at various time points. We also investigated engraftment and differentiation of MAPC-derived myocytes in vivo.

RESULTS

Frozen BM-derived MAPC, cultured under the physiological myogenic condition, demonstrated spatial expression patterns of several myocyte markers similar to that of authentic myocyte differentiation. When injected into murine muscles, MAPC treated with the myogenic condition engrafted and differentiated into myocyte marker-positive cells and myotubes in vivo.

CONCLUSION

For the first time, we were able to induce myocyte formation from BM cells under the physiological condition in vitro and demonstrated that treating cells with this condition prior to intramuscular injection increased efficiency of engraftment and differentiation in vivo.

A highly sensitive strategy for SCID-repopulating cell assay by direct injection of primitive human hematopoietic cells into NOD/SCID mice bone marrow

To measure the ability of human hematopoietic stem cells (HSCs), the SCID-repopulating cell (SRC) assay has been widely used. Conventionally, human HSCs are transplanted into a nonobese diabetic/severe combined immunodeficient (NOD/SCID) mouse via a tail vein. However, those cells must go through various obstacles until they reach the mouse marrow environment, which could explain the generally low homing efficiency in this system. Thus, the capability of HSCs may not be studied accurately by this intravenous transplantation method. In our attempt to reveal actual SRC potential, ie, self-renewal and multilineage differentiation in recipient bone marrow, we introduced cells into mouse marrow directly (intrabone marrow [iBM]) to minimize the effect of factors that may interfere with the homing of HSCs and compared the results obtained by intravenous and iBM methods. When cord blood CD34(+)CD38(-) cells were transplanted in NOD/SCID mice by iBM, a 15-fold higher frequency of SRC, 1 in 44 CD34(+)CD38(-) cells, was achieved compared with 1 in 660 by the intravenous method. Furthermore, the iBM transplant showed high levels of engraftment in the secondary transplantation. Pretreatment of CD34(+) cells with antibodies that block either very late antigen 4 (VLA-4) or VLA-5 reduced engraftment partially, whereas blockage of both molecules resulted in complete inhibition of engraftment, which suggests that VLA-4 and VLA-5 are involved in different processes in engraftment or have complementary roles. Our results indicate that the iBM injection strategy is a more sensitive and direct way to measure the capability of human SRCs and is useful to investigate the interaction of HSCs and marrow environment in vivo.