No abstract

The results of this study demonstrate that IGF-1 and TGF-beta1 can act in combination to regulate proliferation and differentiation of periosteal mesenchymal cells during chondrogenesis.

Studies in rodents have implicated various cytokines as paracrine mediators of increased osteoclastogenesis during estrogen deficiency, but increases in RANKL, the final effector of osteoclastogenesis, have not been demonstrated. Thus, we isolated bone marrow mononuclear cells expressing RANKL on their surfaces by two-color flow cytometry using FITC-conjugated osteoprotegerin-Fc (OPG-Fc-FITC) as a probe. The cells were characterized as preosteoblastic marrow stromal cells (MSCs), T lymphocytes, or B lymphocytes by using Ab’s against bone alkaline phosphatase (BAP), CD3, and CD20, respectively, in 12 premenopausal women (Group A), 12 early postmenopausal women (Group B), and 12 age-matched, estrogen-treated postmenopausal women (Group C). Fluorescence intensity of OPG-Fc-FITC, an index of the surface concentration of RANKL per cell, was increased in Group B over Groups A and C by two- to threefold for MSCs, T cells, B cells, and total RANKL-expressing cells. Moreover, in the merged groups, RANKL expression per cell correlated directly with the bone resorption markers, serum C-terminal telopeptide of type I collagen and urine N-telopeptide of type I collagen, in all three cell types and inversely with serum 17β-estradiol for total RANKL-expressing cells. The data suggest that upregulation of RANKL on bone marrow cells is an important determinant of increased bone resorption induced by estrogen deficiency

Some cosmological solutions of massive strings are obtained in Bianchi I space-time following the techniques used by Letelier and Stachel. A class of solutions corresponds to string cosmology associated with/without a magnetic field and the other class consists of pure massive strings, obeying the Takabayashi equation of state ρ = (1 + ω)λ .

We recently identified circulating osteoblastic cells using antibodies to osteocalcin (OCN) or alkaline phosphatase (AP). We now provide a more detailed characterization of these cells. Specifically, we demonstrate that 46% of OCN positive (OCN pos ) cells express AP, and 37% also express the hematopoietic/endothelial marker, CD34. Using two different anti-OCN antibodies and forward/side light scatter characteristics by flow cytometry, we find that OCN pos cells consist of two distinct populations: one population exhibits low forward/side scatter, consistent with a small cell phenotype with low granularity, and a second population has higher forward/side scatter (larger and more granular cell). The smaller, low granularity population also co-expresses CD34, whereas the larger, more granular cells are CD34 negative. Using samples from 26 male subjects aged 28 to 68 years, we demonstrate that the concentration of circulating OCN pos cells increases as a function of age (R = 0.59, P = 0.002). By contrast, CD34 pos cells tend to decrease with age (R = −0.31, P = 0.18); as a consequence, the ratio of OCN pos :CD34 pos cells also increases significantly with age (R = 0.54, P = 0.022). These findings suggest significant overlap between circulating cells expressing OCN and those expressing the hematopoietic/endothelial marker, CD34. Further studies are needed to define the precise role of circulating OCN pos cells not only in bone remodeling but rather also potentially in the response to vascular injury.