Evolution and development of Hertwig's epithelial root sheath

Authors

  • Xianghong Luan,

    1. Brodie Laboratory for Craniofacial Genetics and Department of Oral Biology, The University of Illinois College of Dentistry, Chicago, Illinois
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  • Yoshihiro Ito,

    1. Brodie Laboratory for Craniofacial Genetics and Department of Oral Biology, The University of Illinois College of Dentistry, Chicago, Illinois
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  • Thomas G.H. Diekwisch

    Corresponding author
    1. Brodie Laboratory for Craniofacial Genetics and Department of Oral Biology, The University of Illinois College of Dentistry, Chicago, Illinois
    • Department of Oral Biology, Director, Brodie Laboratory for Craniofacial Genetics, UIC College of Dentistry, 801 South Paulina Street, MC 841, Chicago, IL 60612
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Abstract

Periodontal regeneration and tissue engineering has re-awakened interest in the role of Hertwig's Epithelial Root Sheath (HERS), an epithelial tissue layer first discovered in amphibians more than a century ago. Using developmental, evolutionary, and cell biological approaches, we have, therefore, performed a careful analysis of the role of HERS in root formation and compared our data with clinical findings. Our developmental studies revealed HERS as a transient structure assembled in the early period of root formation and elongation and, subsequently, fenestrated and reduced to epithelial rests of Malassez (ERM). Our comparative evolutionary studies indicated that HERS fenestration was closely associated with the presence of a periodontal ligament and a gomphosis-type attachment apparatus in crocodilians and mammals. Based on these studies, we are proposing that HERS plays an important role in the regulation and maintenance of periodontal ligament space and function. Additional support for this hypothesis was rendered by our meta-analysis of recent clinical reports related to HERS function. Developmental Dynamics 235:1167–1180, 2006. © 2006 Wiley-Liss, Inc.

Ancillary