The stromal cell population in bone marrow has been the focus of much attention since it has been shown that this cell population can be expanded and differentiated into cells with the phenotype of bone, cartilage, muscle, stroma, neural, and fat cells. We evaluated umbilical cord blood (UCB) for the presence of these cells. From the mononuclear fraction of UCB, we demonstrated the presence of a subset of cells that have been maintained in continuous culture for more than 6 months (>10 passages). These adherent cell populations express adhesion molecules CD13+, CD29+, and CD44+, but not antigens of hematopoietic differentiation. Exposure of these cells to osteogenic agents resulted in an increase in expression of alkaline phosphatase and the appearance of hydroxyapatite nodules by Von Kossa staining. Incubation with adipogenic agents resulted in morphological change and staining with Oil Red O. In addition, when exposed to basic fibroblast growth factor and human epidermal growth factor the cells underwent changes consistent with cells of neural origin. These changes were demonstrated by a combination of immunofluorescent labeling and Western immunoblots for neural-specific markers. Thus, similar to what has been previously reported with bone marrow, cord blood contains a population of cells that can be expanded in culture and are able to express the phenotype of multiple lineages. Cord blood multilineage cells are slower to establish in culture, have a lower precursor frequency and a lower level of bone antigen expression, and lack constitutive expression of neural antigens when compared to bone marrow, suggesting a more primitive population. Cord blood may prove to be a new source of cells for cellular therapeutics for stromal, bone, and, potentially, neural repair.

To understand the mechanisms by which glucocorticoids promote differentiation of fetal rat calvaria derived osteoblasts to produce bone-like mineralized nodules in vitro, a panel of osteoblast growth and differentiation related genes that characterize development of the osteoblast phenotype has been quantitated in glucocorticoid-treated cultures. We compared the mRNA levels of osteoblast expressed genes in control cultures of subcultivated cells where nodule formation is diminished, to cells continuously (35 days) exposed to 10(-7) M dexamethasone, a synthetic glucocorticoid, which promotes nodule formation to levels usually the extent observed in primary cultures. Tritiated thymidine labelling revealed a selective inhibition of internodule cell proliferation and promotion of proliferation and differentiation of cells forming bone nodules. Fibronectin, osteopontin, and c-fos expression were increased in the nodule forming period. Alkaline phosphatase and type I collagen expression were initially inhibited in proliferating cells, then increased after nodule formation to support further growth and mineralization of the nodule. Expression of osteocalcin was 1,000-fold elevated in glucocorticoid-differentiated cultures in relation to nodule formation. Collagenase gene expression was also greater than controls (fivefold) with the highest levels observed in mature cultures (day 35). At this time, a rise in collagen and TGF beta was also observed suggesting turnover of the matrix. Short term (48 h) effects of glucocorticoid on histone H4 (reflecting cell proliferation), alkaline phosphatase, osteopontin, and osteocalcin mRNA levels reveal both up or down regulation as a function of the developmental stage of the osteoblast phenotype. A comparison of transcriptional levels of these genes by nuclear run-on assays to mRNA levels indicates that glucocorticoids exert both transcriptional and post-transcriptional effects. Further, the presence of glucocorticoids enhances the vitamin D3 effect on gene expression. Those genes which are upregulated by 1,25(OH)2D3 are transcribed at an increased rate by dexamethasone, while those genes which are inhibited by vitamin D3 remain inhibited in the presence of dexamethasone and D3. We propose that the glucocorticoids promote changes in gene expression involved in cell-cell and cell-extracellular matrix signaling mechanisms that support the growth and differentiation of cells capable of osteoblast phenotype development and bone tissue-like organization, while inhibiting the growth of cells that cannot progress to the mature osteoblast phenotype in fetal rat calvarial cultures.

. Nmp4/CIZ regulation of matrix metalloproteinase 13 (MMP-13) response to parathyroid hormone in osteoblasts. Am J Physiol Endocrinol Metab 287: E289 -E296, 2004. First published March 16, 2004; 10.1152/ajpendo.00517.2003.-Parathyroid hormone (PTH) regulation of matrix metalloproteinase-13 (MMP-13) expression in osteoblasts contributes to normal bone turnover. The PTH response region of the rat MMP-13 gene spans nucleotides (nt) Ϫ148 to Ϫ38 and supports binding of numerous transcription factors, including Runx2, necessary for osteoblast differentiation, c-Fos/c-Jun, and Ets-1. These trans-acting proteins mediate hormone induction via incompletely defined combinatorial interactions. Within this region, adjacent to the distal Runx2 site, is a homopolymeric(dA:dT) element (Ϫ119/Ϫ110 nt) that conforms to the consensus site for the novel transcription factor nuclear matrix protein-4/cas interacting zinc finger protein (Nmp4/CIZ). This protein regulates bone cell expression of type I collagen and suppresses BMP2-enhanced osteoblast differentiation. The aim of this study was to determine whether Nmp4/CIZ contributes to MMP-13 basal transcription and PTH responsiveness in osteoblasts. Electrophoretic mobility shift analysis confirms Nmp4/ CIZ binding within the MMP-13 PTH response region. Mutation of the Nmp4/CIZ element decreases basal activity of an MMP-13 promoter-reporter construct containing the first 1329 nt of the 5Ј-regulatory region, and overexpression of Nmp4/CIZ protein enhances the activity of the wild-type promoter. The same mutation of the homopolymeric(dA:dT) element enhances the MMP-13 response to PTH and PGE 2. Overexpression of Nmp4/CIZ diminishes hormone induction. Mutation of both the homopolymeric(dA:dT) element and the adjacent Runx2 site further augments the PTH response. On the basis of these data and previous studies, we propose that Nmp4/CIZ is a component of a multiprotein assemblage or enhanceosome within the MMP-13 PTH response region and that, within this context, Nmp4/ CIZ promotes both basal expression and hormonal synergy.collagen; collagenase; bone; endocrine PARATHYROID HORMONE (PTH) induction of matrix metalloproteinase-13 (MMP-13, also called collagenase-3) expression in osteoblasts is a key step in the process of normal bone turnover (33). Bone remodeling, endochondral bone formation, and bone repair all involve osteoblast expression of this enzyme (31, 38, 39). MMP-13 has a wide range of substrates, including types I, II, and III collagen, gelatin, aggrecan, perlecan, fibrillin, and the large isoform of tenascin C and thus also plays a significant role in tumor invasion and metastasis (20,21). Both transcriptional and posttranscriptional mechanisms stringently control the expression and activity of this potent MMP (20).PTH responsiveness of the MMP-13 gene is mediated by the region spanning nucleotides (nt) Ϫ38 through Ϫ148 (Fig. 1 and Refs. 10,14,25,[27][28][29]. This region contains two ciselements for the transcription factor Runx2, a master regulator of osteoblast differentiati...