The effect of thyroid hormone on the cell proliferation of periodontal ligament in rat

Abstract

[한글]

이 연구의 목적은 갑상선 호르몬이 흰쥐의 치주 인대 세포의 증식과 사멸에 미치는 영향을 분석하기 위함이다. 400-500g 사이의 수컷 흰쥐 (Sprague-Dawley rats) 24마리를 사용하였다. 실험동물은 3 집단으로 분류하였다; 정상 대조군 4마리, 생리식염수 투여군 10마리, 갑상선 호르몬 투여 실험군 10마리. 1주일간의 적응기간 후 생리식염수 주사군은 체중 당 1ml/kg의 생리식염수를 1주일간 복강 투여하였다. T3 실험군은 체중 당 100㎍/kg의 3,3'',5-triiodo-L-thyronine (T3, T63971™, Sigma-Aldrich Korea LTD)를 1주일간 복강 투여 하였다. 1주일 후 실험동물을 희생시켜 조직학적 분석 및 비교를 시행하였다. 하악 중절치의 치주 인대를 H-E 염색과 면역학적 염색 방법인 PCNA와 TUNEL 방법으로 관찰하였다. 조직학적 소견 상 T3투여군의 치주인대에서는 상대적으로 울혈된 혈관들이 다수 관찰되었다. 또한 새로운 골 형성도 더 많이 관찰되었다. 치수내에서도 많은 혈관의 증식과 울혈이 관찰되었다.

통계학적 분석을 위해 Kruskal-Wallis 1-way Anova 방법을 사용하였고 각 군당 비교를 위하여 Mann-Whitney U-Wilcoxon Rank Sum W Test 방법을 사용하였다.

T3 실험군에서 PCNA-positive 세포의 수는 정상 대조군과 생리식염수 투여군과 비교하여 통계학적 유의차 있게 높게 나타났다 (p<0.01). 정상 대조군과 생리식염수 투여군간에는 통계학적 유의차가 없었다 (p>0.01).

모든 군에서 TUNEL positive 세포는 매우 드물게 발견되었다. 각 군간 통계학적 유의차는 없었다 (p>0.01).

전신적 T3 호르몬의 투여는 다른 외부자극 없이 치주 인대 세포의 turn over rate을 증가시켰고 치아 맹출 속도를 증가시키는데 기여한다.

[영문]The purpose of this study was to evaluate the effects of thyroid hormone (3,3'',5-triiodo-L-thyronine) on cell proliferation and cell death in the periodontal ligament of rat. Twenty-four adult male Sprague- Dawley rats, weighing 400-500g, were used in this study. The animals were divided into 3 groups; control group (n=4), normal saline injection group (n=10), and thyroid hormone injection group (n=10). After one-week of adaptation period, the control group received the intraperitoneal injection of normal saline every morning for 7 days with the amount of 1ml/kg body weight, and for the experimental group, of 3,3'',5-triiodo-L-thyronine (T3, T63971™, Sigma- Aldrich Korea LTD) every morning for 7 days with the amount of 100㎍/kg body weight. The rats were sacrificed for histological study. Each sample was divided into two specimens; right and left incisors. One incisor was sectioned along the long axis and the other incisor was cross sectioned near the apex. Sections were collected onto silane coated glass slides at a thickness of 5㎛. The sections were stained with hematoxylin-eosin. Additional immunohistochemical staining procedures of proliferating cell nuclear antigen (PCNA) and TdT-mediated dUTP-biotin nick end labeling (TUNEL) were carried out. Light microscopic images were photographed, analyzed and compared. In microscopic examination with H-E stain, T3 injection group showed the typical histologic feature. There were a lot of congested blood vessels in the periodontal tissue. The cells of periodontal tissue showed abundant new bone formation compared those in the control group. In pulp, the number of blood vessel was increased in the same area of magnification and each blood vessel was highly congested.

The data were analyzed statistically with Kruskal-Wallis 1-way Anova with the significance level at p<0.01. To compare between groups, Mann-Whitney U-Wilcoxon Rank Sum W Test was used. Data were expressed as median and range. The number of PCNA-positive cell in the T3 injection group was significantly higher than those of control group and those of normal saline injection group (p<0.01). There was no difference with the number of PCNA-positive cell between in control group and in normal saline injection group (p>0.01). In every groups, TUNEL-positive cells were only rarely found. There was no specificity of the distribution of the TUNEL-positive cells in every group. No statistically significant differences were noted among control group, normal saline injection group and T3 injection group (p>0.01).

Systemic T3 injection enhanced the turnover rate of cells in the periodontal ligament without any other external stimulation and may cause to increase the eruption rate of tooth in rat.