Mitogenic activity of hydroxyapatite: Requirement for somatomedin C

H. S. Cheung, J. J. Van Wyk, W. E. Russell, D. J. McCarty

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Synovial hyperplasia is a feature of the chronic synovitis associated with basic calcium phosphate crystals [hydroxyapatite (HA), octacalcium phosphate, tri‐calcium phosphate] and calcium pyrophosphate. Each of these crystals stimulated mitosis of cultured human skin fibroblasts or canine synovial fibroblasts in a concentration‐dependent fashion. We examined the effect of pure somatomedin C (Sm‐C) on HA crystal induced mitogenesis. Confluent cultures of human fibroblasts were rendered quiescent by incubation in the presence of 1% platelet‐poor‐Sm‐C free plasma (PPSCFP) for 24 hours. HA crystals stimulated thymidine incorporation 2.3‐fold over control value. Addition of Sm‐C significantly augmented the effect of HA crystals (P < 0.01). Nearly identical effects were observed in the presence of 100 μg/ml HA crystals or 15 ng/ml PDGF. Monoclonal antibodies against Sm‐C had little effect on the basal 3H thymidine uptake by control cells incubated in 1% PPSCFP but blocked over 50% of the HA crystal of PDGF‐induced 3H thymidine incorporation both in the presence or absence of Sm‐C. The incomplete blocking suggested either the presence of other “progression” factors, such as insulin‐like growth factor II in the conditioned media or the possibility that HA or PDGF in high enough dosage enabled cells to escape their dependence on Sm‐C for DNA synthesis.

Original languageEnglish (US)
Pages (from-to)143-148
Number of pages6
JournalJournal of Cellular Physiology
Issue number2
StatePublished - Aug 1986
Externally publishedYes

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Cell Biology


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