Induction of osteoblast aggregation, detachment, and altered integrin expression by bear serum

Michael Overstreet, Timothy Floyd, Anna Polotsky, David S. Hungerford, Carmelita G. Frondoza

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Animal models have long been used to elucidate the mechanisms responsible for osteoporosis in humans. The American black bear, an animal that does not experience extensive bone loss normally associated with long-term immobilization (when hibernating), may provide an insight into the nature of the pathogenesis of the disease. Circulating growth and differentiation factors present in the serum may facilitate continued proliferation of bone-forming cells. The aim of our study was to determine the effects of bear serum on human osteoblasts when cultured for extended periods of time. Unexpectedly, exposure to the bear serum in vitro led to the detachment of osteoblasts from the surface of the culture plate after 3 d of incubation. The osteoblasts pulled off the polystyrene surface in sheets and aggregated into floating conglomerations of viable cells. In contrast, osteoblasts cultured in fetal calf serum maintained adherence to the surface of the culture plate. Detachment of osteoblasts propagated in bear serum was time dependent and was associated with an increased expression of integrins compared with osteoblasts propagated in fetal calf serum, as indicated by reverse transcriptase-polymerase chain reaction and immunostaining.

Original languageEnglish (US)
Pages (from-to)4-7
Number of pages4
JournalIn Vitro Cellular and Developmental Biology - Animal
Issue number1-2
StatePublished - Jan 2004
Externally publishedYes


  • Aggregation
  • Bear
  • Cell attachment
  • Integrin
  • Osteoblast

ASJC Scopus subject areas

  • Developmental Biology
  • Cell Biology


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