Tohoku J. Exp. Med., 2001, 194 (4)

Restoring Effect of Human Parathyroid Hormone (1-34) on Trabecular Connectivity in Ovariectomized Rats

TSUNEHISA TSUCHIDA, NAOHISA MIYAKOSHI, TAKUYA KUDO, YASUKI TAMURA,
YUJI KASUKAWA, KOJI SUZUKI and KOZO SATO

Department of Orthopedic Surgery, Akita University School of Medicine, Akita 010-8543

The purpose of this study was to determine if the loss of the trabecular connectivities can be recovered by human parathyroid hormone-(1-34) therapy in ovariectomized (OVX) rats. Seven-month old female Wistar rats underwent ovariectomy or sham-operation at the beginning of the experiment. All sham operated groups (sham groups) were sacrificed after 0 (initial-BL group), 4, 8, 12, and 16 weeks, and one-third of the OVX rats were sacrificed as the baseline controls (OVX-BL groups) at 4, 8, and 12 weeks after OVX. Four weeks PTH or its vehicle treatment for residual OVX rats was started at 4, 8, or 12 weeks after OVX (OVX+PTH groups, OVX+vehicle groups). h-PTH (6.0 mg/kg) was injected subcutaneously six times a week for 4 weeks for each group. Their proximal right tibiae were processed for undecalcified Villanueva bone staining sections for bone histomorphometry. Furthermore, changes in trabecular connectivities were determined by node-strut analysis. h-PTH completely restored OVX-induced cancellous bone loss by stimulating bone formation. In node-strut analysis, node number in the OVX-BL-4, -8, and -12 groups was decreased to 53%, 49% and 44% of the initial-BL value respectively, and that in the OVX-4, -8, -12+PTH groups recovered to 80%, 66%, 56% of the initial-BL value respectively. However, they were lower than those in their corresponding sham groups. The findings of this study suggested that decreased trabecular connectivity by OVX was recovered by intermittent h-PTH administration. However, delayed treatment blunted the restoration of trabecular connectivity.

Keywords —— human parathyroid hormone; trabecular connectivity; ovariectomy; bone histomorphometry; node-strut analysis

© 2001 Tohoku University Medical Press

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Tohoku J. Exp. Med., 2001, 194, 213-221

Address for reprint: Tsunehisa Tsuchida, Department of Orthopedic Surgery, Akita University School of Medicine, 1-1-1 Hondo, Akita 010-8543, Japan.

e-mail: tsuchy@ma4.justnet.ne.jp

A part of this study was presented at the Second Joint Meeting of the American Society for Bone and Mineral Research and The International Bone and Mineral Society, San Francisco, December 4, 1998; Bone, 1998, 23, S518. (abstract)