Lovastatin對於骨誘導生成及牙本質誘導生成能力之探討

Abstract

Statin類藥物是一種目前臨床上大量使用的高血脂症治療藥物，可有效降低總膽固醇，並減少心血管疾病發生率。近年來，有許多的實驗同時也發現，statin類藥物可以刺激BMP-2（Bone morphogic protein）的表現，而BMP2表現上升，可以促進人類骨頭以及牙髓組織的鈣化以及再生。 但是，statin類藥物光使用口服方式使用，不容易在患區維持足夠的作用濃度；若考慮局部注射方式，statin類藥物又有細胞毒性的問題。為了解決上述兩種問題，可以採用高分子包膜技術將適量之statin包覆進高分子外膜內，如此一來可以透過控制釋放機制，在患區維持適當之statin濃度，達成避免細胞毒性及維持有效濃度的雙重功效。 本實驗使用20隻雄性大白鼠，隨機分成四組，在各隻老鼠的下顎骨兩側分別做出一5mm大小之人工缺損，Group I置入1mg包有lovastatin的PLGA高分子，對側置入gelfoam做為對照組；Group II置入3mg 包有lovastatin的PLGA高分子及gelfoam；Group III置入1mg包有 lovastatin的PLGA高分子，對側則置入1mg不含lovastatin的PLGA高分子作為對照組；Group IV置入3mg 含有lovastatin的PLGA高分子及3mg不含lovastatin的PLGA高分子。在3、6、9、12週，使用cone-beam CT掃描實驗動物的缺損區觀察其變化，12週後犧牲實驗動物，將其下顎骨送病理切片，觀察骨頭生成的實際情形。 實驗結果可以觀察到，各組隨著時間變化，都有大小不一的缺損癒合狀況，但是癒合體積狀況最理想的是1mg含lovastatin的高分子，且在病理組織切片之下，也可以明顯看出新生骨的出現，由此可知，在適當的控制釋放機制之下，statin類藥物可以有效的促進骨頭的癒合及再生。 而在牙本質再生方面，在實驗中使用4隻李宋細小耳種迷你豬的乳牙前牙，一共24顆牙齒，將24顆牙齒隨機分為四實驗組，在牙齒上做出一個Class V的窩洞，並將牙髓腔暴露出來，在止血及沖洗後，Group I中直接以GIC填補起來；Group II則是先以MTA做覆髓動作，再以GIC填補；Group III則是先以lovastatin直接覆髓後，以GIC填補起來；Group IV則是先在牙髓表面注入帶有紅色螢光的乳牙牙髓幹細胞（SHED） 後，再以GIC填補。經過45天癒合後，將牙齒拔下來，先用牙科根尖X光機及CT掃描，觀察是否有鈣化物質生成，再將牙齒送組織切片觀察。 從CT掃描結果可以觀察到先使用MTA、lovastatin及SHED做覆髓處理後，牙髓腔內都有鈣化物質的生成，將拔下來的牙齒經過組織處理並切片染色後，也可以在顯微鏡底下發現修復性牙本質的生成，而且牙髓組織的活性及組成都是正常狀態。因此lovastatin對於牙本質再生方面，也同樣具有保護牙髓以及刺激修復性牙本質生成的能力。

The statins are commonly prescribed drugs that inhibit 3-hydroxy-3-methylglutaryl coenzyme A (HMG Co-A) reductase and decrease hepatic cholesterol biosynthesis, thereby reducing serum cholesterol concentrations and lowering the risk of heart attack. Recently, lots of studies found that statins showed enhanced expression of BMP-2 mRNA, which can induce the regeneration of bone and dental pulp tissue. However, the efficacy of statin using oral administration is not expected, because the ultimate systemic availability is only 2.4%, far less than bone formation needed. When injected locally, statin has the side effect of cytotoxicity. Therefore, a suitable control release device is important to deliver the drug. In this study, 20 male wistar rats were used. The animals were randomly divided into 4 groups. Artificial bony defects of 5mm were created with bone trephine bur on mandibular bodies of both sides. Group 1 received 1 mg PLGA nanoparticles containing lovastatin in the right side defects and gelfoam was placed in the left side defects which served as control. Group 2 received 3 mg PLGA nanoparticles containing lovastatin in the right side defects and gelfoam was placed in the left side defects. Group 3 received 1 mg PLGA nanoparticles containing lovastatin in the right side defects and 1 mg PLGA nanoparticles without lovastatin were placed in the left side defects. Group 4 received 3 mg PLGA nanoparticles containing lovastatin in the right side defects and 3 mg PLGA nanoparticles without lovastatin were placed in the left side defects. CBCT scan was used at 3, 6, 9, and 12 weeks after surgery to measure the progressive volume changes of the artificial bony defect. The rats were sacrificed at 12 weeks, and the mandible bones were sent for histological examination. According to the X-ray scan, each group shows the trend of bone healing through time, but group I has the most significant outcome. We can also find new bone formation under histological examination. Thus, using proper delivery device, lovastatin has the ability to induce bone healing and regeneration. In the odontogenic induction study, we used 4 miniature pigs, with a total number of 24 deciduous anterior teeth. All teeth were randomly divided into 4 groups. Class V cavities were created on each tooth, then the cavities were deepened to expose the pulp tissue. After bleeding control and irrigation. Group I were restored with GIC directly. Group II capped with MTA, then restored with GIC. Group III capped with lovastatin, then restored with GIC. Group IV capped with red fluorescent SHED, then restored with GIC. After a healing period of 45 days. All the teeth were extracted. After periapical film and CBCT scan, histological examination were used to examine the reparative dentin formation. Under CT scan, group I, II and III could find calcified images in pulp space. Under microscope, reparative dentin could be found in group I, II and III, and the underlying pulp tissue were all vital. Thus, lovastatin may have the ability to protect exposed pulp tissue and induce reparative dentin formation.