In Vitro Regulation of Osteoblast Activity

During calcification of bone, large amounts of phosphate (P_i) must be transported from the circulation to the osteoid. Likely candidates for osteoblast P_i transport are the type II sodium-phosphate cotransporters NaPi-IIa and NaPi-IIb that facilitate transcellular P_i flux in kidney and intestine, respectively. We have therefore determined the cotransporters'' expression in osteoblast-like cells. We have also studied the cotransporters'' regulation by P_i and during mineralization in vitro. Phosphate uptake and cotransporter protein expression was investigated at early, late and mineralizing culture stages of mouse (MC3T3-E1) and rat (UMR-106) osteoblast-like cells. Both NaPi-IIa and NaPi-IIb were expressed by both osteoblast-like cell lines. NaPi-IIa was upregulated in both cell lines one week after confluency. After 7 days in 3mM P_i NaPi-IIa was strongly upregulated in both cell lines. NaPi-IIb expression was unaffected by both culture stage and P_i supplementation. The expression of both cotransporters was unaffected by P_i deprivation. In vitro mineralization at 1.5mM P_i was preceded by a three-fold increase in osteoblast sodium-dependent P_i uptake and a corresponding upregulation of both NaPi-IIa and NaPi-IIb. Their expression thus seem regulated by phosphate in a manner consistent with their playing a role in transcellular P_i flux during mineralization.

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“…That the phenotype of cultured osteoblast-like cells changes with culture stage has been described previously (for a review see ref. [36]). …”

Section: Discussionmentioning

confidence: 99%

Type II Na+-Pi Cotransporters in Osteoblast Mineral Formation: Regulation by Inorganic Phosphate

Lundquist

Murer

Biber

2007

Cell Physiol Biochem

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An New in Vitro Model of Breast Cancer Metastasis to Bone

Mastro¹,

Vogler²

2007

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) 01-04-2007 REPORT TYPE ABSTRACT:Human (hFOB 1.19) and murine (MC3T3-E1) osteoblasts grew for extended periods (up to 10 months) in a specialized bioreactor. Over time the cells formed multilayers and a collagenous matrix with mineralized nodules and small chips of "bone". The number of cell layers in the bone-like tissue peaked at about 30 to 60 days and then declined. This change was reflected in the cell morphology. Wth time, the osteoblasts transitioned from multilayer cuboidal cells to flat osteocyte-like cells. We characterized the response of MC3T3-E1 bone-like tissue at various stages of maturity to metastatic human MDA-MB-231 breast cancer cells using a variety of approaches. The cancer cells attached, grew, and penetrated the matrix. Within 2 days of coculture, the cancer cells replicated and organized into linear files. Close inspection of both 2D optical sections and 3D reconstructions revealed concomitant remodeling of the tissue. Over 3 days of co-culture, cuboidal osteoblasts became elongated and aligned themselves with cancer cells. The osteoblasts responded with production of IL-6, a characteristic osteoblast inflammatory stress cytokine. These data support our idea that the bioreactor will serve as a useful in vitro model to study the interaction of metastatic breast cancer cells and osteoblasts. SUBJECT TERMSNone provided.

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In Vitro Regulation of Osteoblast Activity

Cited by 2 publications

References 246 publications

Type II Na<sup>+</sup>-P<sub>i</sub> Cotransporters in Osteoblast Mineral Formation: Regulation by Inorganic Phosphate

Type II Na<sup>+</sup>-P<sub>i</sub> Cotransporters in Osteoblast Mineral Formation: Regulation by Inorganic Phosphate

An New in Vitro Model of Breast Cancer Metastasis to Bone

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