Papers by Teuvo A Hentunen
Do microRNAs regulate bone marrow stem cell niche physiology?
Gene, 2012
The adult bone marrow, situated within the bone cavity, comprises three distinct stem cell popula... more The adult bone marrow, situated within the bone cavity, comprises three distinct stem cell populations: hematopoietic stem cells (HSCs), mesenchymal stromal/stem cells (MSCs) and endothelial progenitor/stem cells (EPCs). HSCs are a well-characterized population of self-renewing cells that give rise to all blood cells. The definition of MSCs is more complex due to the limited understanding of MSC properties. In general, MSCs are considered multipotent stromal cells that are able to differentiate into various cell types, including osteoblasts, chondrocytes and adipocytes. Compared to HSCs and MSCs, EPCs are a newly discovered population of stem/progenitor cells with the capacity to differentiate into endothelial cells, the cells forming the inner lining of a blood vessel. Although functionally different, HSCs, MSCs and EPCs, like stem cells in general, share the ability to self-renew and differentiate into one or more cell types. The homeostasis inside the bone marrow and within the entire body is sustained by an intricate network of growth factors and transcription factors that orchestrate the proliferation and differentiation of these multipotent stem/progenitor cells. Increasing evidence indicates that microRNAs (miRNAs), small non-coding RNAs, are among the key players of this concert. This review summarizes the current insights into miRNA-mediated regulation of bone marrow stem/progenitor cell maintenance and differentiation. Furthermore, the potential contribution of miRNAs in bone marrow stem cell niches is discussed.
Characterization of microRNA expression in bone cells
Bone, 2012
Journal of Clinical Investigation, 1998
Cellular and molecular characterization of osteoclasts (OCL) has been extremely difficult since O... more Cellular and molecular characterization of osteoclasts (OCL) has been extremely difficult since OCL are rare cells, and are difficult to isolate in large numbers. We used the tartrate-resistant acid phosphatase promoter to target the bcl -X L and/or Simian Virus 40 large T antigen (Tag) genes to cells in the OCL lineage in transgenic mice as a means of immortalizing OCL precursors. Immunocytochemical studies confirmed that we had targeted Bcl-X L and/or Tag to OCL, and transformed and mitotic OCL were readily apparent in bones from both Tag and bcl -X L /Tag mice. OCL formation in primary bone marrow cultures from bcl -X L , Tag, or bcl -X L /Tag mice was twofold greater compared with that of nontransgenic littermates. Bone marrow cells from bcl -X L /Tag mice, but not from singly transgenic bcl -X L or Tag mice, have survived in continuous culture for more than a year. These cells form high numbers of bone-resorbing OCL when cultured using standard conditions for inducing OCL formation, with ف 50% of the mononuclear cells incorporated into OCL. The OCL that form express calcitonin receptors and contract in response to calcitonin. Studies examining the proliferative capacity and the resistance of OCL precursors from these transgenic mice to apoptosis demonstrated that the increased numbers of OCL precursors in marrow from bcl -X L /Tag mice was due to their increased survival rather than an increased proliferative capacity compared with Tag, bcl -X L , or normal mice. Histomorphometric studies of bones from bcl -X L /Tag mice also confirmed that there were increased numbers of OCL precursors (TRAP ϩ mononuclear cells) present in vivo. These data demonstrate that by targeting both bcl -X L and Tag to cells in the OCL lineage, we have immortalized OCL pre-cursors that form bone-resorbing OCL with an efficiency that is 300-500 times greater than that of normal marrow. ( J. Clin. Invest. 1998. 102:88-97.) Key words: osteoclasts • bcl -X L • Simian Virus 40 large T antigen • precursors • transgenic • apoptosis
Endocrinology, 1999
We recently developed an immortalized osteoclast (OCL) precursor cell line that forms large numbe... more We recently developed an immortalized osteoclast (OCL) precursor cell line that forms large numbers of OCLs. This cell line was derived from mice doubly transgenic for bcl-X L and large T antigen that was targeted to cells in the OCL lineage (bcl-X L /Tag cells). We have now characterized these cells in terms of their surface and enzymatic phenotype, responsiveness to osteotropic factors, and differentiation potential. The bcl-X L /Tag cells expressed interleukin-1 receptors 1 and 2, gelatinase B (MMP9), as well as Mac-1, CD16/CD32 (Fc␥ receptors), CD45.2 (common leukocyte marker), CD86 (costimulatory molecule expressed on B cells, follicular dendritic cells, and thymic epithelium), major histocompatibility complex I, and nonspecific esterase when cocultured with MC3T3E1 cells. However, they did not express the antigens for F4/80 (mature macrophage/dendritic cell marker) by immunostaining. Treatment of bcl-X L /Tag cells, cocul-
Calcified Tissue International, 2005
Several cell surface markers were used to isolate monocytes as osteoclast progenitors with an imm... more Several cell surface markers were used to isolate monocytes as osteoclast progenitors with an immunomagnetic cell separation system. Use of this system with specific monocyte antibodies produced 99% pure monocytes. When purified monocytes were cultured on bovine bone slices in the presence of receptor activator of nuclear factor-jB (RANKL), macrophagecolony stimulating factor (M-CSF), tumor necrocis factor alpha (TNF-a), and dexamethasone for 14 days, CD14 + CD11b + , and CD61 + monocytes had approximately 90-, 30-and 20-fold higher osteoclast formation capacities/plated cells compared to the control culture. CD15 + monocytes generated few tartrate-resistant acid phosphatase-positive multinucleated cells (TRACP+ MNC), and CD169 + monocytes generated no TRACP+ MNC. This suggests, that there are various subsets of monocytes in the blood circulation and that they have different capacities in osteoclast formation. These results show that circulating human osteoclast progenitors can be efficiently purified by immunomagnetic cell separation system using anti-CD14, -CD11b, and -CD61 antibodies. These purified monocyte fractions had different ability to give rise to osteoclasts. CD169 was not found to be suitable for osteoclast progenitor isolation. Optimal concentration of dexamethasone for osteoclast formation and bone resorption was 10 nM. To develop a human resorption assay, osteoclasts were first induced for 7 days, whole media were replaced, cultures were continued for additional 3 days and C-terminal telopeptide of type I collagen was determined from culture media. This assay was shown to be functional, since two well-known resorption inhibitors, bafilomycin A 1 and calcitonin, dose-dependently inhibited the resorption activity of osteoclasts.
A murine model of inflammatory bone disease
Bone, 2000
We have recently reported the identification of a new recessive mutation on murine chromosome 18 ... more We have recently reported the identification of a new recessive mutation on murine chromosome 18 that results in tail kinks and deformity in the lower extremities of mice. Preliminary examination of the bones of these mice showed that there are abnormalities present that resembled chronic recurrent multifocal osteomyelitis. Accordingly, this new mutation was named "CMO." In this report, we describe the histology of bones in CMO mice, as well as the capacity of the bone marrow cells from these animals to form osteoclasts (OCLs). In addition, we tested conditioned media from non-adherent marrow cells and total marrow cells from CMO mice for their capacity to induce OCL formation in normal murine marrow cultures. These studies demonstrated that the bone disease in these animals is inflammatory in nature, and a soluble factor(s) that is not IL-1alpha, IL-6 or TNF-alpha is released by marrow cells from CMO animals and enhances OCL formation in normal murine marrow cultures.
Bone and mineral, 1994
An activity that recruits osteoclasts has been identified and partially characterized from bone m... more An activity that recruits osteoclasts has been identified and partially characterized from bone matrix. Bone-derived osteoclast recruiting activity (BORA) was co-purified with osteogenin, a bone inductive protein. Osteogenin was extracted from bovine bone with 6 M urea and purified by chromatography on hydroxyapatite, heparin-Sepharose and Sephacryl S-200 gel filtration. The biologically active osteoclast formation-stimulating material was further purified by C18 reverse phase HPLC. BORA is obviously distinct from osteogenin and transforming growth factor beta (TGF-beta), since further purified osteogenin and pure TGF-beta did not stimulate the formation of osteoclast-like cells. BORA (0.1-10 micrograms/ml) stimulated the formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNC) in a dose-dependent manner. These multinucleated cells resorbed bone when cultured on bovine bone slices. The effect of BORA is primarily directed to differentiate osteoclas...
Cyclooxygenase Inhibitors Interfere Human Mesemchymal Stem Cell Differentation Into Osteoblasts by Converting the Mesenchymal Cells Into Adipocytes
Clinical chemistry, 2000
Osteoclasts secrete tartrate-resistant acid phosphatase (TRAP; EC 3.1.3.2) 5b into the circulatio... more Osteoclasts secrete tartrate-resistant acid phosphatase (TRAP; EC 3.1.3.2) 5b into the circulation. We studied the release of TRAP 5b from osteoclasts using a mouse in vitro osteoclast differentiation assay. We developed and characterized a polyclonal antiserum in rabbits, using purified human osteoclastic TRAP 5b as antigen. The antiserum was specific for TRAP in Western analysis of mouse osteoclast culture medium and was used to develop an immunoassay. We cultured mouse bone marrow-derived osteoclast precursor cells for 3-7 days with or without clodronate in the presence of vitamin D and analyzed the number of osteoclasts formed and the amount of TRAP 5b activity released into the culture medium. TRAP 5b activity was not secreted from osteoclast precursor cells. Addition of clodronate-containing liposomes decreased in a dose-dependent manner the number of osteoclasts and TRAP 5b activity released in 6-day cultures. The amount of TRAP 5b activity in the medium detected by the immun...
The Journal of Cell Biology
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Papers by Teuvo A Hentunen