Initiation of Osteoclast Bone Resorption by Interstitial Collagenase*
- L. Shannon Holliday‡§,
- Howard G. Welgus‡,
- Catherine J. Fliszar‡,
- G. Michael Veith¶,
- John J. Jeffrey‖ and
- Stephen L. Gluck‡§**‡
- From the Departments of ‡Medicine, §Cell Biology and Physiology, ¶Biology, and the **George M. O’Brien Center for Kidney and Urological Diseases, Washington University School of Medicine, St. Louis, Missouri 63110 and the ‖Department of Biochemistry, Albany Medical College, Albany, New York 12208
Abstract
Osteoclasts form an acidic compartment at their attachment site in which bone demineralization and matrix degradation occur. Although both the cysteine proteinases and neutral collagenases participate in bone resorption, their roles have remained unclear. Here we show that interstitial collagenase has an essential role in initiating bone resorption, distinct from that of the cysteine proteinases. Treatment of osteoclasts with cysteine proteinase inhibitors did not affect the number of resorption lacunae (“pits”) formed on the surface of dentine slices, but it generated abnormal pits that were demineralized but filled with undegraded matrix. Treatment with metalloproteinase inhibitors did not alter the qualitative features of lacunae, but it greatly reduced the number of pits and surface area resorbed. Treatment of bone cells with an inhibitory anti-rat interstitial collagenase antiserum reduced bone resorption markedly. In the presence of collagenase inhibitors, resorption was restored by pretreatment of dentine slices with rat interstitial collagenase or by precoating the dentine slices with collagenase-derived gelatin peptides or heat-gelatinized collagen. Immunostaining revealed that interstitial collagenase is produced at high levels by stromal cells and osteoblasts adjacent to osteoclasts. These results indicate that interstitial collagenase can function as a “coupling factor,” allowing osteoblasts to initiate bone resorption by generating collagen fragments that activate osteoclasts.
Footnotes
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↵* This work was supported by National Institutes of Health Grants AR32087 (to H. G. W. and S. L. G.), HD05291 (to J. J. J.), and DK38848, DK09976, DK45181 (to S. L. G.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‡ To whom correspondence should be addressed: Renal Division, Washington University School of Medicine, 660 S. Euclid Ave., Box 8126, St. Louis, MO 63110. Tel.: 314-362-8762; Fax: 314-362-8237; E-mail:sgluck{at}imgate.wustl.edu.
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↵1 The abbreviations used are: SC44463,N-[3-(N′-hydroxycarboxamido)-2-(2-methylpropyl)propanoyl]-O-methyl-l-tyrosine-N-methylamide; αMEM, α minimum essential medium; FBS, fetal bovine serum; scanning EM, scanning electron microscopy; rIC, rat interstitial collagenase; MMP, matrix metalloproteinase; TIMP, tissue inhibitor of metalloproteinase.
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↵2 An inhibitor of mammalian MMPs:K i versus human MMP-1, 1.45 nm; K i versus rIC (MMP-13), 0.65 nm (26, 27).
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↵3 This treatment did not significantly affect the resorptive activity of osteoclasts on the slice.
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- Received February 27, 1997.
- Revision received May 20, 1997.
