Effects of rosiglitazone vs metformin on circulating osteoclast and osteogenic precursor cells in postmenopausal women with type 2 diabetes mellitus.

CONTEXT: Thiazolidinediones are associated with increased fractures in type 2 diabetes mellitus (T2D). One explanation is that activation of peroxisome proliferator-activated receptor-γ expression alters bone remodeling cells. OBJECTIVE: To investigate whether osteoclast and osteogenic precursor cells are altered by rosiglitazone (RSG) treatment in T2D as compared to metformin (MET) treatment. DESIGN: A randomized controlled trial of RSG or MET for 52 weeks, followed by 24 weeks of MET. SETTING: Data were generated at a tertiary care center. PATIENTS: Seventy-three T2D postmenopausal women participated. MAIN OUTCOME MEASURES: Peripheral blood mononuclear cells were isolated and cultured with receptor activator of nuclear factor κB ligand and stained for tartrate-resistant acid phosphatase to measure circulating osteoclast precursors. Peripheral blood mononuclear cells were also characterized for osteogenic, endothelial, and calcification markers by flow cytometry with the ligands osteocalcin (OCN), CD34, and CD 146. RESULTS: Tartrate-resistant acid phosphatase-positive cells increased between weeks 0 and 52 (RSG, 2.9 ± 2 to 14.0 ± 3 U/L, P = .001; MET, 3.3 ± 2 to 16.7 ± 2 U/L, P = .001), increasing further in the RSG group after changing to MET (to 26.5 ± 5 U/L, P = .05 vs wk 52). With RSG, OCN+ cells with CD34 but without CD146 fell from weeks 0 to 52 (20.1 ± 1% to 15.5 ± 2%; P = .03), remaining stable through week 76. The OCN+ cells lacking both CD34 and CD146 increased from weeks 0 to 52 (67.3 ± 2 to 74.4 ± 2%; P = .02), but returned to baseline after switching to MET. CONCLUSION: In postmenopausal women with T2D, circulating osteoclast precursor cells increase with both RSG and MET, and increase further when switching from RSG to MET. Subpopulations of cells that may be involved in the osteogenic lineage pathway are also altered with RSG. Further work is necessary to elucidate how these changes may relate to fracture risk.

Circulating osteogenic precursor cells in type 2 diabetes mellitus.

CONTEXT: Type 2 diabetes mellitus (T2D) is associated with an increased risk of fractures and low bone formation. However, the mechanism for the low bone formation is not well understood. Recently, circulating osteogenic precursor (COP) cells, which contribute to bone formation, have been characterized in the peripheral circulation. OBJECTIVE: Our objective was to characterize the number and maturity of COP cells in T2D. PATIENTS, DESIGN, AND SETTING: Eighteen postmenopausal women with T2D and 27 controls participated in this cross-sectional study at a clinical research center. MAIN OUTCOME MEASURES: COP cells were characterized using flow cytometry and antibodies against osteocalcin (OCN) and early stem cell markers. Histomorphometric (n = 9) and molecular (n=14) indices of bone turnover and oxidative stress were also measured. RESULTS: The percentage of OCN(+) cells in peripheral blood mononuclear cells was lower in T2D (0.8 ± 0.2 vs. 1.6 ± 0.4%; P < 0.0001), whereas the percentage of OCN(+) cells coexpressing the early marker CD146 was increased (OCN(+)/CD146(+): 33.3 ± 7 vs. 12.0 ± 4%; P < 0.0001). Reduced histomorphometric indices of bone formation were observed in T2D subjects, including mineralizing surface (2.65 ± 1.9 vs. 7.58 ± 2.4%, P = 0.02), bone formation rate (0.01 ± 0.1 vs. 0.05 ±0.2 µm(3)/um(2) · d, P = 0.02), and osteoblast surface (1.23 ±0.9 vs. 4.60 ± 2.5%, P = 0.03). T2D subjects also had reduced molecular expression of the osteoblast regulator gene Runx2 but increased expression of the oxidative stress markers p66(Shc) and SOD2. CONCLUSIONS: Circulating OCN(+) cells were decreased in T2D, whereas OCN(+)/CD146(+) cells were increased. Histomorphometric indices of bone formation were decreased in T2D, as was molecular expression of osteoblastic activity. Stimulation of bone formation may have beneficial therapeutic skeletal consequences in T2D.

Parathyroid hormone stimulates circulating osteogenic cells in hypoparathyroidism.

CONTEXT: The osteoanabolic properties of PTH may be due to increases in the number and maturity of circulating osteogenic cells. Hypoparathyroidism is a useful clinical model because this hypothesis can be tested by administering PTH. OBJECTIVE: The objective of the study was to characterize circulating osteogenic cells in hypoparathyroid subjects during 12 months of PTH (1-84) administration. DESIGN: Osteogenic cells were characterized using flow cytometry and antibodies against osteocalcin, an osteoblast-specific protein product, and stem cell markers CD34 and CD146. Changes in bone formation from biochemical markers and quadruple-labeled transiliac crest bone biopsies (0 and 3 month time points) were correlated with measurements of circulating osteogenic cells. SETTING: The study was conducted at a clinical research center. PATIENTS: Nineteen control and 19 hypoparathyroid patients were included in the study. INTERVENTION: Intervention included the administration of PTH (1-84). RESULTS: Osteocalcin-positive cells were lower in hypoparathyroid subjects than controls (0.7 ± 0.1 vs. 2.0 ± 0.1%; P < 0.0001), with greater coexpression of the early cell markers CD34 and CD146 among the osteocalcin-positive cells in the hypoparathyroid subjects (11.0 ± 1.0 vs. 5.6 ± 0.7%; P < 0.001). With PTH (1-84) administration, the number of osteogenic cells increased 3-fold (P < 0.0001), whereas the coexpression of the early cell markers CD34 and CD146 decreased. Increases in osteogenic cells correlated with circulating and histomorphometric indices of osteoblast function: N-terminal propeptide of type I procollagen (R(2) = 0.4, P ≤ 0.001), bone-specific alkaline phosphatase (R(2) = 0.3, P < 0.001), osteocalcin (R(2) = 0.4, P < 0.001), mineralized perimeter (R(2) = 0.5, P < 0.001), mineral apposition rate (R(2) = 0.4, P = 0.003), and bone formation rate (R(2) = 0.5, P < 0.001). CONCLUSIONS: It is likely that PTH stimulates bone formation by stimulating osteoblast development and maturation. Correlations between circulating osteogenic cells and histomorphometric indices of bone formation establish that osteoblast activity is being identified by this methodology.

Tolerization of dendritic cells by T(S) cells: the crucial role of inhibitory receptors ILT3 and ILT4.

Immunoglobulin-like transcript 3 (ILT3) and ILT4 belong to a family of inhibitory receptors expressed by human monocytes and dendritic cells. We show here that CD8+CD28(-) alloantigen-specific T suppressor (TS) cells induce the up-regulation of ILT3 and ILT4 on monocytes and dendritic cells, rendering these antigen-presenting cells (APCs) tolerogenic. Tolerogenic APCs show reduced expression of costimulatory molecules and induce antigen-specific unresponsiveness in CD4+ T helper cells. Studies of human heart transplant recipients showed that rejection-free patients have circulating TS cells, which induce the up-regulation of ILT3 and ILT4 in donor APCs. These findings demonstrate an important mechanism of immune regulation.

Abnormal T-cell repertoire is consistent with immune process underlying the pathogenesis of paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal disorder of the hematopoietic stem cell (HSC). Somatic mutations in the PIG-A gene result in the deficiency of several glycosylphosphatidylinositol-linked proteins from the surface of blood cells. This explains intravascular hemolysis but does not explain the mechanism of bone marrow failure that is almost invariably seen in PNH. In view of the close relationship between PNH and idiopathic aplastic anemia (IAA), it has been suggested that the 2 disorders might have a similar cellular pathogenesis, namely, that autoreactive T-cell clones are targeting HSCs. In this paper, we searched for abnormally expanded T-cell clones by size analysis of the complementarity-determining region 3 (CDR3) in the beta variable chain (BV) messenger RNA (mRNA) of the T-cell receptor (TCR) in 19 patients with PNH, in 7 multitransfused patients with hemoglobinopathy. and in 11 age-matched healthy individuals. We found a significantly higher degree of skewness in the TCR BV repertoire of patients with PNH, compared with controls (R(2) values 0.82 vs 0.91, P <.001). The mean frequency of skewed families per individual was increased by more than 2-fold in patients with PNH, compared with controls (28% +/- 19.6% vs 11.4% +/- 6%, P =.002). In addition, several TCR BV families were significantly more frequently skewed in patients with PNH than in controls. These findings provide experimental support for the concept that PNH, like IAA, has an immune pathogenesis. In addition, the identification of expanded T-cell clones by CDR3 size analysis will help to investigate the effect of HSC-specific T cells on normal and PNH HSCs.

Age-related dysregulation in CD8 T cell homeostasis: kinetics of a diversity loss.

Relative diversity and representation of peripheral T cells bearing different TCR Vbeta families are remarkably tightly regulated between birth and advanced adulthood. By contrast, individual elderly humans and C3H.SW and B10.BR aged mice display drastic disruption in such regulation. It was suggested that the alterations in the murine aged T cell compartment were due to age-related clonal T cell expansions (TCE). Here, we studied the kinetics of homeostatic dysregulation of T cell populations in aged C57BL/6 (B6) mice. Using mAb staining, we show that the percentages of alphabeta+CD8+ or CD4+ T cells bearing different TCRVbeta elements remain virtually constant in mice up to 12 mo of age. In 22-mo-old mice, however, there is a dramatic disturbance of this pattern owing to the emergence of CD8+ TCE. Expanded T cells did not show any obvious bias in Vbeta usage and were derived in all cases examined thus far from a single clone. TCE appeared later in life, compared with B cell clonal expansions. However, and in contrast to those detected in humans, TCE were frequently unstable disappearing within 2-4 mo, with other TCE appearing within the same time frame. Additional studies carried on thymic T cells, thymectomized mice, and young T transferred cells into Rag1-/- mice suggest that the clonal expansions occur in the periphery and that their onset is accelerated by decreased thymic output and/or function(s).

Cellular basis of B cell clonal populations in old mice.

Previous studies from this laboratory have shown that >85% of old mice have stable B cell clonal populations detectable by Ig heavy chain complementary-determining region 3 mRNA size analysis and confirmed by sequence analysis. B cells from the same clone are frequently detected in several lymphoid compartments of the same mouse. We now report the phenotype of all ten stable B cell clonal populations detected in five 20-month-old C57BL/6 mice. These clonal B cells appear to develop in the periphery and nine of the ten B cell clonal populations expressed the CD5 cell surface marker. Stable B cell expansions may be dominated by cells at two stages of differentiation. Some B cell populations were detected with DNA as well as RNA and represent large clonal populations of B cells, detectable in several lymphoid compartments. These populations are found predominantly in B cell populations expressing CD45R/B220 and the mRNA coding for the membrane-bound form of the mu Ig heavy chain, which suggests a predominance of B lymphocytes in these populations. In other cases, smaller clonal populations were detected only in splenic RNA samples. These clonal populations were found predominantly among CD45R/B220- B cells and did not express the membrane-bound form of the micro Ig heavy chain. We offer the hypothesis that the B cell clonal populations present in old mice may be precursors of the two types of B cell neoplasms which are dominated by CD5+ B cells (B cell chronic lymphocytic leukemia) or plasma cells (multiple myeloma).

Differentiation of human CD8 T cells: implications for in vivo persistence of CD8+ CD28- cytotoxic effector clones.

CD8 T cells contain a distinct subset of CD8+ CD28- cells. These cells are not present at birth and their frequency increases with age. They frequently contain expanded clones using various TCRalphabeta receptors and these clones can represent >50% of all CD8 cells, specially in old subjects or patients with chronic viral infections such as HIV-1. Herein, it is shown that a large fraction of CD8+ CD28- cells expresses intracellular perforin by three-color flow cytometry, in particular when this subset is expanded. Together with their known ability to exert potent re-directed cytotoxicity, this indicates that CD8+ CD28- T cells comprise cytotoxic effector cells. With BrdU labeling, we show that CD8+ CD28- cells derive from CD8+ CD28+ precursors in vitro. In addition, sorted CD8+ CD28+ cells gave rise to a population of CD8+ CD28- cells after allo-stimulation. Moreover, ex vivo CD8+ CD28+ cells contain the majority of CD8 blasts, supporting the notion that they contain the proliferative precursors of CD8+ CD28- cells. CD95 (Fas) expression was lower in CD8+ CD28- cells, and this subset was less prone to spontaneous apoptosis in ex vivo samples and more resistant to activation-induced cell death induced by a superantigen in vitro. Thus, the persistence of expanded clones in vivo in the CD8+ CD28- subset may be explained by antigen-driven differentiation from CD8+ CD28+ memory precursors, with relative resistance to apoptosis as the clones become perforin(+) effector cells.

Increased VH 11 and VH Q52 gene use by splenic B cells in old mice associated with oligoclonal expansions of CD5 + B cells.

A significant increase in the utilization of the VH gene families VH11 and Q52 was observed in LPS-stimulated splenic B lymphocytes from aged mice compared to young mice. VH gene usage was assayed by in situ DNA/RNA hybridization using VH family-specific and kappa chain probes. The observed age-dependent differences appear to reflect the preferential use of VH11 and Q52 VH gene use by the CD5 + B lymphocyte subset whose numbers in the spleen increase with age. The increased use of VH11 by splenic cells from old mice is associated with clonal expansions of splenic CD5 + B lymphocytes.

Expanded CD4+ and CD8+ T cell clones in elderly humans.

The diversity of the human TCR repertoire in aging has been studied by examining the profiles of complementarity-determining region 3 (CDR3) sizes expressed by the BV families. The TCRBV CDR3 profile, which shows size heterogeneity in young adult humans, is significantly restricted in aged humans. Clonal T cell expansions were identified using a PCR-based approach, in one or more BV families from all 14 healthy persons over the age of 65 that we studied. CD4+ T cell expansions were identified in 8 of 11 donors and CD8+ T cell expansions in 7 of 10 donors. These clonal expansions were stable during a 2-year period. Interestingly, more than half of the aged persons had clonal expansions within the BV3, -14, -16, and -23 families. Although there was no homology among the eight CDR3 sequences identified in clonal T cells from 8 aged persons, selective pressure on the expanded T cell clones was suggested by the fact that the BV families used by the T cell clones were not proportional to the number of genes in the different BV families.

Delayed arousal from anesthesia: a further similarity between stress and beta-1 adrenoceptor blockade.

The present studies investigated the role of beta adrenergic receptors in mediating arousal from anesthesia and the effects of stress on this process. In support of previous findings by others, it was found that blockade of beta-1 and beta-2 receptors by propranolol delayed arousal from halothane anesthesia and that this effect was attributable to blockade of beta-1 receptors because it was duplicated by betaxolol but not by ICI 118,551. Restraint stress also produced a delay in arousal from both halothane and hexobarbital anesthesia. This effect, which was observed at 0.5 but not 24 h after the stress, could not be explained by a stress-induced alteration in the metabolism of the anesthetic, as no difference in brain concentration of hexobarbital was found between stressed and control mice. The parallel effects of beta-1 blockade and stress further supports the hypothesis that stress produces an impairment in function at either the beta-1 receptor or some process coupled to this receptor.

Effect of yohimbine on nerve growth factor mRNA and protein levels in rat hippocampus.

Activation of noradrenergic receptors has been shown to increase expression of nerve growth factor (NGF) gene in brain cells in vitro. The present studies were undertaken to determine if this stimulation was effective in vivo as well. Rats were administered the norepinephrine-releasing drug, yohimbine (YOH), and had their hippocampi assayed for NGF mRNA and protein at various times after the injection. It was found that yohimbine caused a 3-fold increase of NGF mRNA levels at 24 h. Protein levels, however, were unaltered at this time. Thus norepinephrine release in vivo appears to be sufficient for increasing mRNA level but not for translation to protein.