Localization of Perlecan and Heparanase in Hertwigs Epithelial Root Sheath During Root Formation in Mouse Molars
Azumi Hirata 1* and Hiroaki Nakamura 1
1 Department of Oral Morphology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan (AH), and Department of Oral Histology, Matsumoto Dental University, Shiojiri, Japan (HN)
* To whom correspondence should be addressed. E-mail: yamagata{at}md.okayama-u.ac.jp.
Submitted on November 15, 2005
Accepted on 26 May 2006
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Abstract |
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During cementogenesis, dental follicular cells penetrate the ruptured Hertwigs epithelial root sheath (HERS) and differentiate into cementoblasts. The mechanisms involved in basement membrane degradation during this process have not been clarified. Perlecan, a heparan sulfate proteoglycan, is a component of all basement membrane. Degradation of heparan sulfate of perlecan by heparanase cleavage affects a variety of biological processes. We elucidated immunolocalization of perlecan and heparanase in developing murine molars to clarify their roles in cementoblast differentiation. At the initial stage of root formation, perlecan immunoreactivity was detected on the basement membrane of HERS. Weak heparanase immunoreactivity was detected in HERS cells. HERS showed intense staining for heparanase as root formation progressed. In contrast, labeling for perlecan disappeared from the basement membrane facing the dental follicle, and weak immunoreactivity for perlecan was detected on the inner side of the basement membrane of HERS. These findings suggest that perlecan removal is an important step for root and periodontal tissue formation. Heparanase secreted by the cells of HERS may contribute to root formation by degrading perlecan in the dental basement membrane.
Key Words:
Hertwig’s epithelial root sheath, basement membrane, murine model, heparanase, perlecan, root formation, cementogenesis