Human bone cell enzyme expression and cellular heterogeneity: Correlation of alkaline phosphatase enzyme activity with cell cycle

Neal S Fedarko, P. Bianco, U. Vetter, P. Gehron Robey

Research output: Contribution to journalArticle

Abstract

Alkaline phosphatase, long implicated in biomineralization, is a feature of the osteoblast phenotype. Yet in cultured bone cells, only a fraction stain positive histochemically. To determine whether osteoblast enzyme expression reflects cellular heterogeneity with respect to cell cycle distribution or length of time in culture, the activities of alkaline phosphatase, tartrate-resistant and -sensitive acid phosphatases, and non-specific esterases were assayed kinetically and histochemically. In asynchronous subconfluent cultures, 6 cells/cm2. After 1 week, the percent of alkaline phosphatase positive-staining cells increased 5-fold, while activity increased 10-fold. Non-specific esterases and tartrate-sensitive acid phosphatase were constitutive throughout time in culture, whereas tartrate-resistant acid phosphatase activity appeared after 2 weeks. Cell cycle analysis of human bone cells revealed a growth fraction of 80%, an S phase of 8.5 h, G2 + 1/2 M of 4 h, and a G1 of 25-30 h. In synchronous cultures induced by a thymidine-aphidicolin protocol, alkaline phosphatase activity dropped precipitously at M phase and returned during G1. A majority of the alkaline phosphatase activity lost from the cell surface at mitosis was recovered in the medium. Tartrate-sensitive acid phosphatase and non-specific esterase levels were relatively stable throughout the cell cycle, while tartrate-resistant acid phosphatase activity was not assayable at the density used in synchronous cultures. From these data, variations in alkaline phosphatase activity appear to reflect the distribution of cells throughout the cell cycle.

Original languageEnglish (US)
Pages (from-to)115-121
Number of pages7
JournalJournal of Cellular Physiology
Volume144
Issue number1
StatePublished - Jul 1990
Externally publishedYes

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Enzyme activity
Alkaline Phosphatase
Acid Phosphatase
Cell Cycle
Bone
Cells
Bone and Bones
Carboxylesterase
Enzymes
Osteoblasts
Aphidicolin
Biomineralization
S Phase
Cell culture
Mitosis
Cell Division
Thymidine
Cultured Cells
Coloring Agents
Cell Culture Techniques

ASJC Scopus subject areas

  • Clinical Biochemistry
  • Cell Biology
  • Physiology

Cite this

Human bone cell enzyme expression and cellular heterogeneity : Correlation of alkaline phosphatase enzyme activity with cell cycle. / Fedarko, Neal S; Bianco, P.; Vetter, U.; Gehron Robey, P.

In: Journal of Cellular Physiology, Vol. 144, No. 1, 07.1990, p. 115-121.

Research output: Contribution to journalArticle

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abstract = "Alkaline phosphatase, long implicated in biomineralization, is a feature of the osteoblast phenotype. Yet in cultured bone cells, only a fraction stain positive histochemically. To determine whether osteoblast enzyme expression reflects cellular heterogeneity with respect to cell cycle distribution or length of time in culture, the activities of alkaline phosphatase, tartrate-resistant and -sensitive acid phosphatases, and non-specific esterases were assayed kinetically and histochemically. In asynchronous subconfluent cultures, 6 cells/cm2. After 1 week, the percent of alkaline phosphatase positive-staining cells increased 5-fold, while activity increased 10-fold. Non-specific esterases and tartrate-sensitive acid phosphatase were constitutive throughout time in culture, whereas tartrate-resistant acid phosphatase activity appeared after 2 weeks. Cell cycle analysis of human bone cells revealed a growth fraction of 80{\%}, an S phase of 8.5 h, G2 + 1/2 M of 4 h, and a G1 of 25-30 h. In synchronous cultures induced by a thymidine-aphidicolin protocol, alkaline phosphatase activity dropped precipitously at M phase and returned during G1. A majority of the alkaline phosphatase activity lost from the cell surface at mitosis was recovered in the medium. Tartrate-sensitive acid phosphatase and non-specific esterase levels were relatively stable throughout the cell cycle, while tartrate-resistant acid phosphatase activity was not assayable at the density used in synchronous cultures. From these data, variations in alkaline phosphatase activity appear to reflect the distribution of cells throughout the cell cycle.",
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