人乳牙牙髓基质细胞的分离培养与牙再生能力

背景:在牙组织工程和牙再生的研究中,寻找合适的种子细胞是当前的中心和热点.目的:分离培养儿童乳牙牙髓基质细胞,比较研究矿化诱导前后牙本质涎磷蛋白表达的差异.设计、时间及地点:观察性实验,于2006-12/2007-12在大庆油田总医院中心实验室完成.对象:选择8～10岁儿童8名,男4名,女4名,排除传染病及内分泌疾病史,乳牙排除牙体牙髓牙周疾病.牙髓取材于颌外门诊拔除的滞留乳磨牙.方法:通过组织块贴壁法获得乳牙牙髓基质细胞,并在含体积分数10%胎生血清的DMEM培养基中原代培养14 d,消化传代后用添加有10-8 mol/L地塞米松,50 μmol/L左旋抗坏血酸,10 nmol/L维生素D3,10 mmol/L β-磷酸甘油钠的DMEM/F12培养基诱导培养14 d,用不含添加成分的完全DMEM培养基培养作对照.主要观察指标:显微镜下观察细胞形态变化和生长规律.免疫细胞化学染色比较诱导前后牙本质涎磷蛋白的表达差异.结果:乳牙牙髓基质细胞呈成纤维细胞样贴壁生长,经矿化诱导14 d后多数细胞由梭形转变成多角形和柱型,胞核大而圆,B0%以卜细胞的细胞质牙本质涎磷蛋白表达阳性.而未经诱导的细胞仍为梭形,仅有2%的细胞牙本质涎磷蛋白染色呈阳性.结论:乳牙牙髓基质细胞经矿化诱导培养后具有向成牙本质细胞分化的潜能,可以尝试作为牙再生研究新的种子细胞来源.     

变形链球菌诱导牙髓细胞MMP-8 mRNA的表达及意义

目的采用变形链球菌诱导体外培养的人牙髓成纤维细胞,观察变形链球菌对人牙髓成纤维细胞中MMP-8影响,探讨MMP-8在牙髓炎症过程中的作用机制。方法采用组织块法体外培养人牙髓成纤维细胞,通过变形链球菌上清液诱导建立牙髓细胞损伤实验模型,利用RT-PCR方法检测经变球链球菌诱导人牙髓成纤维细胞中MMP-8的表达。结果经变形链球菌诱导后的人牙髓成纤维细胞中MMP-8的表达增强。结论变形链球菌能够促进人牙髓成纤维细胞中MMP-8的合成和分泌,从而导致牙髓中细胞外基质的降解,产生不可逆性牙髓损伤。     

Carisolv去龋治疗乳牙龋病效果分析

目的 评价Carisolv去龋治疗乳牙龋病的临床效果.方法 将100颗龋损乳牙分为2组各50颗牙,观察组采用Carisolv去龋,对照组采用传统牙钻去龋,均应用复合体充填,2 a后进行疗效评价.结果 失访10颗牙,观察组治疗成功率89.1％(41/46),对照组65.9％(29/44),2组比较差异有统计学意义(P＜0.01);观察组充填物脱落或折断、继发龋发生率以及对牙髓的影响均低于对照组(P＜0.05).结论 Carisolv去龋治疗乳牙龋病疗效确切,较传统牙钻去龋更具优势.     

骨形态发生蛋白4调节人牙髓干细胞在脱细胞的牙髓基质中促进成骨/成血管分化的研究

目的探究骨形态发生蛋白4(BMP4)与脱细胞人牙髓细胞外基质是否共同调节人牙髓干细胞(hDPSCs)介导的成骨/成血管分化。方法从健康的人第三磨牙中分离出牙髓,改良组织块法培养hDPSCs并进行鉴定,用十二烷基硫酸钠(SDS)和Triton X-100制作脱细胞化细胞外基质(dECM),电子显微镜观察其结构,Cell Counting Kit-8分析细胞增殖生长曲线。使用重组腺病毒BMP4感染hDPSCs。HE和DAPI染色后,当看不到完整的细胞核时,分别在dECM和三维(3D)VitroGel系统中培养细胞,并通过碱性磷酸酶染色(ALP)与实时定量聚合酶链反应(qRT-PCR)评估骨/牙本质/血管生成标记的表达。结果提取hDPSCs并完成鉴定,制作脱细胞牙髓细胞外基质并于镜下观察无细胞核存在。Cell Counting Kit-8分析结果表明,dECM可以支持hDPSCs的生长和增殖且没有明显的细胞毒性。ALP染色结果显示,BMP4和dECM协同促进hDPSCs成骨分化。qRT-PCR结果显示,成骨和成血管细胞基因的表达增加。结论dECM可促进hDPSCs增殖,而BMP4+dECM促进hDPSCs在体外成骨和成血管分化。     

猪牙乳头细胞与β-磷酸三钙支架构建牙髓牙本质复合体样结构

目的:牙乳头细胞是牙髓细胞、牙本质细胞的前体细胞,应用组织工程方法探讨以猪牙乳头细胞为种子细胞构建牙髓牙本质复合体的可行性. 方法:实验于2004-03/2005-11在上海市口腔医学重点实验室完成.以第1代猪牙乳头细胞为种子细胞与β-磷酸三钙为支架材料复合后接种在裸鼠皮下.移植在裸鼠皮下的β-磷酸三钙支架与牙乳头细胞复合物为实验组,同期移植牙胚作为阳性对照组,同期植入的空白β-磷酸三钙支架材料作阴性对照组.每组3个样本,在同一裸鼠皮下植入.8周后取材进行组织学(苏木精-伊红染色及Goldner'三色法染色)、牙本质涎蛋白免疫组织化学及透射电镜检测.结果:①移植物组织学切片显示在支架材料孔隙内形成了牙髓牙本质复合体样结构,由牙本质基质样物质、前期牙本质样物质及牙髓样组织组成.在牙本质样物质内部可见少量牙本质小管,牙髓样组织外层细胞较为密集且单层排列,表现出成牙本质细胞样细胞的特征.②免疫组织化学染色显示,在邻近成牙本质细胞样细胞周围的前期牙本质内牙本质涎蛋白呈阳性表达.③透射电镜结果显示,实验组局部可见牙本质小管样结构.结论:以猪牙乳头细胞为种子细胞、β-磷酸三钙为支架材料,成功构建出牙髓牙本质复合体样结构.     

猪牙乳头细胞与β-磷酸三钙支架构建牙髓牙本质复合体样结构

目的：牙乳头细胞是牙髓细胞、牙本质细胞的前体细胞，应用组织工程方法探讨以猪牙乳头细胞为种子细胞构建牙髓牙本质复合体的可行性。方法：实验于2004-03／2005-11在上海市口腔医学重点实验室完成。以第1代猪牙乳头细胞为种子细胞与β-磷酸三钙为支架材料复合后接种在裸鼠皮下。移植在裸鼠皮下的β-磷酸三钙支架与牙乳头细胞复合物为实验组，同期移植牙胚作为阳性对照组，同期植入的空白β-磷酸三钙支架材料作阴性对照组。每组3个样本，在同一裸鼠皮下植入。8周后取材进行组织学（苏木精-伊红染色及Goldner＇色法染色）、牙本质涎蛋白免疫组织化学及透射电镜检测。结果：①移植物组织学切片显示在支架材料孔隙内形成了牙髓牙本质复合体样结构，由牙本质基质样物质、前期牙本质样物质及牙髓样组织组成。在牙本质样物质内部可见少量牙本质小管，牙髓样组织外层细胞较为密集且单层排列，表现出成牙本质细胞样细胞的特征。②免疫组织化学染色显示，在邻近成牙本质细胞样细胞周围的前期牙本质内牙本质涎蛋白呈阳性表达。③透射电镜结果显示，实验组局部可见牙本质小管样结构。结论：以猪牙乳头细胞为种子细胞、β-磷酸三钙为支架材料，成功构建出牙髓牙本质复合体样结构。     

有关儿童牙病治疗的几个问题

儿童牙病的治疗,包括乳牙的治疗和年轻恒牙的治疗两个部分。由于各自的特点,其治疗方法有所不同,现分述如下。乳牙的治疗: 1.乳牙龋病的治疗:注意固位型,两相邻牙的邻面龋,一定要分开充填。浅龋:涂氟或备洞充填。中龋:备洞垫底充填。深龋:去净腐质未穿髓者,用氧化锌、水门汀双层垫底后充填。去净腐质穿髓者,不再保髓而做干髓治疗。因为乳牙牙本质较薄,钙化较低,深龋近髓时容易引起慢性牙髓炎或牙髓环疽,     

牙胚组织中成釉蛋白表达免疫组织化学和原位杂交的特点

目的:观察人牙胚组织中成釉蛋白的表达特点。方法:实验于2002-02/04在解放军第四军医大学口腔内科实验室完成。取孕5个月流产男性胎儿(产妇知情同意),截取上、下颌骨,常规方法制备人牙胚组织石蜡切片。用兔抗人AMBN多克隆抗体,对人牙胚组织石蜡切片和正常狗牙周组织石蜡切片进行免疫组织化学染色。标记人成釉蛋白cDNA探针,对人牙胚组织石蜡切片进行原位杂交。结果:①免疫组织化学染色发现成釉蛋白由内釉上皮细胞在分化为成熟成釉细胞前开始表达,分泌期成釉细胞高度表达并持续整个釉质形成期,新形成的牙釉质染色阳性;成牙本质细胞在分泌牙本质基质之前开始表达成釉蛋白,在牙本质形成过程中成牙本质细胞持续表达成釉蛋白,呈弱阳性,前期牙本质中呈弱阳性染色;上皮根鞘细胞染色阳性。狗牙周组织染色发现牙骨质表层细胞呈强阳性染色,新形成的牙骨质中可见阳性染色颗粒,呈网状分布。②对人牙胚组织石蜡切片的原位杂交显示,成釉蛋白在成釉细胞、成牙本质细胞、上皮根鞘细胞中有表达,表达部位与免疫组织化学结果一致。结论:内釉上皮首先表达成釉蛋白,之后前成牙本质细胞达成釉蛋白。成釉细胞、成牙本质细胞、上皮根鞘细胞表达成釉蛋白。     

牙胚组织中成釉蛋白表达免疫组织化学和原位杂交的特点

目的：观察人牙胚组织中成釉蛋白的表达特点。 方法：实验于2002—02／04在解放军第四军医大学口腔内科实验室完成。取孕5个月流产男性胎儿（产妇知情同意），截取上、下颌骨，常规方法制备人牙胚组织石蜡切片。用兔抗人AMBN多克隆抗体，对人牙胚组织石蜡切片和正常狗牙周组织石蜡切片进行免疫组织化学染色。标记人成釉蛋白cDNA探针，对人牙胚组织石蜡切片进行原位杂交。 结果：①免疫组织化学染色发现成釉蛋白由内釉上皮细胞在分化为成熟成釉细胞前开始表达，分泌期成釉细胞高度表达并持续整个釉质形成期，新形成的牙釉质染色阳性；成牙本质细胞在分泌牙本质基质之前开始表达成釉蛋白。在牙本质形成过程中成牙本质细胞持续表达成釉噩白，呈弱阳性，前期牙本质中呈弱阳性染色；上皮根鞘细胞染色阳性。狗牙周组织染色发现牙骨质表层细胞呈强阳性染色，新形成的牙骨质中可见阳性染色颗粒，呈网状分布。②对人牙胚组织石蜡切片的原位杂交显示，成釉蛋白在成釉细胞、成牙本质细胞、上皮根鞘细胞中有表达，表达部位与免疫组织化学结果一致。 结论：内釉上皮首先表达成釉蛋白，之后前成牙本质细胞达成釉蛋白。成釉细胞、成牙本质细胞、上皮根鞘细胞表达成釉蛋白。     

小鼠单纯疱疹病毒性角膜炎中基质金属蛋白酶-2、8、9阳性细胞计数及意义

目的探讨单纯疱疹病毒性角膜炎小鼠角膜中基质金属蛋白酶(MMP)-2、8、9阳性细胞计数、细胞来源及临床意义。方法建立小鼠单纯疱疹病毒性角膜基质炎(HSK)模型,分别收集正常角膜和感染1型单纯疱疹病毒(HSV-1)后2d、7d、14d的小鼠角膜,行免疫组化染色。在光学显微镜下对免疫组化切片的结果进行分析,观察不同时间点MMP-2、8、9在角膜组织中的定位,并分别统计中央角膜及周边角膜基质中MMP-2、8、9阳性细胞、MMP-2、8、9阳性的中性粒细胞及浸润的中性粒细胞、总细胞的数量,进行统计分析。结果感染后第2天,上述各细胞表达增加,主要位于浅表基质层及上皮下的炎性细胞,周边角膜组织中的中性粒细胞和MMP-2、8、9阳性细胞数明显高于中央角膜基质中;感染后第7天,MMP-2、8、9及中性粒细胞表达下降;感染后第14天可见中央角膜坏死及角膜溃疡形成,同时角膜基质和浸润的炎性细胞中尤其溃疡处,可见MMP-2、8、9表达显著增加。结论 HSV-1感染角膜后,大量中性粒细胞自角膜缘血管网侵入中央角膜基质。中性粒细胞与角膜细胞释放大量的蛋白水解酶(MMP-2、8、9),可能在角膜上皮炎、角膜溃疡穿孔、新生血管形成等过程中发挥重要作用。     

草酸铁溶液处理牙本质后黏结界面的超微形态

背景:基于流体动力学说,选择良好的生物材料封闭暴露的牙本质小管口是国际上对治疗牙齿敏感研究的热点。草酸铁溶液可以在牙本质小管内形成结晶样结构。目的:观察草酸铁溶液结合全酸蚀黏结系统处理牙本质后黏结界面的形态学变化。方法:选择无龋人离体智齿12颗,去除牙冠牙釉质,暴露牙本质。随机均分为实验组和对照组,32%磷酸酸蚀剂酸蚀牙本质黏结面,实验组用5.3%草酸铁溶液处理表面1min后充分冲洗10s,两组表面再充填树脂。平行牙长轴方向片切制备扫描电镜试样,在扫描电镜(SEM)下观察黏结界面的微观形态。结果与结论:实验组草酸铁产生的结晶样结构几乎堵塞全部牙本质小管开口,树脂层伸出无数短小树脂突嵌于硬化的牙本质小孔内。对照组局部区域混合层与其下方未脱矿的牙本质间有明显的裂隙出现,树脂突较粗,但长短不均匀,可见树脂突的断裂。提示,5.3%草酸铁溶液能够在牙本质小管内形成结晶,使牙本质小管口封闭良好。对照组可见树脂突的断裂,牙本质小管暴露,封闭不严密。说明5.3%草酸铁溶液结合全酸蚀黏结系统治疗牙本质龋能够提高其临床治愈率。     

Stimulation of reparative dentin formation by ex vivo gene therapy using dental pulp stem cells electrotransfected with growth/differentiation factor 11 (Gdf11)

Dental pulp progenitor/stem cells have the capacity to differentiate into odontoblasts and they provide a potential for dentin repair and regeneration by gene therapy. To develop a successful ex vivo gene therapy to induce reparative dentin formation rapidly and effectively after treatment of caries, we developed a three-dimensional pellet culture system of pulp cells electrotransfected with growth/differentiation factor 11 (Gdf11). The viability after electrotransfection was more than 85%, and the efficiency was about 70% as determined by flow cytometry. After 10 days of culture, the total amount of type I and type III collagen was 3-fold higher in the pEGFP-Gdf11-transfected pellet than in the control. Real-time RT-PCR analysis demonstrated that the expression of markers of odontoblast differentiation (alkaline phosphatase, dentin matrix protein 1 [Dmp1], dentin sialophosphoprotein [Dspp], enamelysin, and phosphate-regulating gene with homologies to endopeptidases on X-chromosome [Phex]) was increased in the pEGFP-Gdf11-transfected pellet compared with the control on day 14. On the basis of this in vitro evaluation, an in vivo investigation in the dog was performed. Autogenous transplantation of Gdf11-transfected cells cultured as a pellet on amputated pulp stimulated reparative dentin formation. Thus, Gdf11 gene therapy may be potentially used in endodontic treatment in dentistry.     

Common dental infections in the primary care setting

Family physicians commonly encounter patients with dental infections, such as dental caries and periodontal disease. Dental caries is caused by bacteria that destroy the enamel and dentin; it can be detected by an oral examination that shows stained pits or fissures on the tooth surface. Use of fluoride is the most effective prevention measure for dental caries. Untreated caries may progress to pulpitis and, eventually, to necrosis of the pulp. In irreversible pulpitis, the tooth dies and the patient may have a localized abscess that can spread to surrounding tissue. Periodontal infections are caused by bacteria in the subgingival dental plaque. In gingivitis, the inflamed gums bleed easily with brushing or flossing; the condition can be controlled with good oral hygiene. Periodontitis is characterized by a loss of supportive bone structure caused by chronic gingivitis; it is also associated with some systemic diseases. Localized periodontitis is treated with mechanical debridement and good oral hygiene, whereas generalized periodontitis requires adjunct antibiotic therapy. Pericoronitis results when food particles become trapped under the gum of an impacted tooth. This condition can be controlled by removal of food debris and good oral hygiene. For patients in whom dental infections are disseminated and have invaded the deeper oral spaces, antibiotic treatment should be initiated at the time of referral.     

Characterization of enamel and dentin response to Nd:YAG picosecond laser ablation

OBJECTIVE: We investigated the main characteristics of human dental tissue under Nd:YAG picosecond laser ablation. SUMMARY BACKGROUND DATA: The use of ultrashort laser pulses for teeth ablation prevents overheating and is an alternative for mechanical material removal; it also minimizes the volume of damaged material. METHODS: Laser pulses of picosecond at 15 Hz repetition rates from a Q-switched and mode-locked Nd:YAG laser were focused on sound human molars for 30 seconds. Variation of light intensity in the pulse train allowed us to obtain drilled holes with different characteristics. Enamel and dentin surfaces were examined by optical and scanning electron microscope (SEM). The samples consisted of three sound human molars. The ablation rate was determined after taking an average of all samples. RESULTS: Images from the SEM showed an interesting contrast between the morphology of the ablated enamel and dentin regions. In enamel, the ablated region appears to be more superficial than in dentin. The dentin fragility normally causes cracks that originate in the ablated region. The ablation rates in both enamel and dentin demonstrate a saturation behavior as the laser intensity increases. Furthermore, the ablation rate in dentin is about eight times greater than in enamel for the same laser fluence. CONCLUSION: Our results show an important correlation between the surface morphology and the pulsed laser fluence, which is compatible to the ablation mechanisms presented when ultrashort laser pulses are used.     

草酸铁溶液处理牙本质后黏结界面的超微形态

背景：基于流体动力学说,选择良好的生物材料封闭暴露的牙本质小管口是国际上对治疗牙齿敏感研究的热点。草酸铁溶液可以在牙本质小管内形成结晶样结构。目的：观察草酸铁溶液结合全酸蚀黏结系统处理牙本质后黏结界面的形态学变化。方法：选择无龋人离体智齿12颗,去除牙冠牙釉质,暴露牙本质。随机均分为实验组和对照组,32%磷酸酸蚀剂酸蚀牙本质黏结面,实验组用5.3%草酸铁溶液处理表面1min后充分冲洗10s,两组表面再充填树脂。平行牙长轴方向片切制备扫描电镜试样,在扫描电镜（SEM）下观察黏结界面的微观形态。结果与结论：实验组草酸铁产生的结晶样结构几乎堵塞全部牙本质小管开口,树脂层伸出无数短小树脂突嵌于硬化的牙本质小孔内。对照组局部区域混合层与其下方未脱矿的牙本质间有明显的裂隙出现,树脂突较粗,但长短不均匀,可见树脂突的断裂。提示,5.3%草酸铁溶液能够在牙本质小管内形成结晶,使牙本质小管口封闭良好。对照组可见树脂突的断裂,牙本质小管暴露,封闭不严密。说明5.3%草酸铁溶液结合全酸蚀黏结系统治疗牙本质龋能够提高其临床治愈率。     

Pulpal effects of a high rep rate Nd:YAG laser

Molar teeth in male rats were used in this study to assess the effects of enamel surface treatments of pulp survivability. The occlusal surfaces of the first and third molars in each quadrant were treated with an Nd:YAG laser (Pulsemaster, Incisive Technologies, Inc.) using a 300-mum contact tip fiber, in a figure-8 motion, for a 30 sec ablation time. The second molars were not treated. Energy parameters/animal were as follows: (1) 0.6 W, 30 mJ energy, and 20 Hz, (2) 1.2 W, 30 mJ energy, and 40 Hz, (3) 1.8 W, 30 mJ energy, and 60 Hz, (4) 2.4 W, 30 mJ energy, and 80 Hz, (5) 0.6 W, 60 mJ energy, and 10 Hz, (6) 1.2 W, 60 mJ energy, and 20 Hz, (7) 1.8 W, 60 mJ energy, and 30 Hz, (8) 1.0 W, 100 mJ energy, and 10 Hz, and (9) 2.0 W, 100 mJ energy, and 20 Hz. Animals were sacrificed at two time periods (1 and 6 weeks, postoperatively). SEM analysis of enamel was performed at 2000x magnification to observe the parameter difference in surface quality. Microscopic examination of the histological samples was accomplished at 250x magnification. Surface analyses of tooth structure revealed a wide dispersion of enamel roughness, ranging from slightly etched to moderately cavitated. Power levels above 2.4 W exhibited significantly more roughness than lower energy parameters. Efforts were made to correlate the pulp biology effect with enamel surface condition to determine a safe threshold for survivability of the pulp tissue.(ABSTRACT TRUNCATED AT 250 WORDS)     

窝沟封闭术预防性治疗磨牙(牙合)面窝沟浅龋的近期疗效观察

目的探讨可见光固化窝沟封闭剂治疗磨牙窝沟浅龋的临床应用价值。方法实验组60例6~15岁患者牙合面窝沟浅龋,在去龋后用光固化窝沟封闭剂对龋损部位及窝沟进行封闭术,并采用对侧同名牙或邻牙也有窝沟浅龋者作对照。结果随访1年发现,实验组无1例发展为中龋,而对照组有28颗(32.94%)发展为中龋。结论光固化窝沟封闭术作为磨牙牙合面窝沟浅龋的预防性治疗方法,有较好的近期临床疗效。     

Morpho-structural aspects of Er:YAG-prepared class V cavities

OBJECTIVE: The aim of this study was to evaluate the ability of an Er:YAG laser (2960nm) to prepare class V cavities as compared with rotary instruments. MATERIALS AND METHODS: Twenty-six freshly extracted human molars were selected and randomly distributed in two groups. Non standardized class V cavities were prepared using (group 1) a diamond bur for enamel, plus a tungsten bur for dentin with water irrigation and (group 2) an Er:YAG laser (output parameters, enamel: 1000 mJ, 12Hz, dentin: 500 mJ, 20Hz) with a continuous flow of water. RESULTS: The SEM examination revealed characteristic micro-irregularities of the lased samples as compared with the conventional prepared cavities: group 1, the walls of the cavities were slightly curved and a smear layer plus muds covered peripheric walls as well as the depth of the cavity; rare dentinal tubules were opened; linear and circular surface irregularities were observed on the dentin; and group 2, the walls of the cavities were irregular, jagged; photo-ablation creates a real cleavage of hydroxyapatite prisms with respect to the enamel prism pathway; an homogeneous dentin with opened dentinal tubules covered the depth of the cavities; intertubular dentin is selectively more ablated than Er-YAG the peritubular dentin. CONCLUSIONS: Jagged outline as well as opened dentinal tubules are the main characteristics of the Er-YAG prepared class V cavities. Further investigations (ulstrastructural, histochemical properties of the lased dentin, resistance to traction of bonded resins) should be conducted.     

Effect of Low-Intensity Pulsed Ultrasound on a Rat Model of Dentin–Dental Pulp Injury and Repair

This study investigated histopathologic changes in dental pulp after treatment with low-intensity pulsed ultrasound (LIPUS). Fifty rats were randomly divided into an experimental group (n = 25) and a blank control group (n = 25). In the experimental group, a cavity was prepared in the bilateral maxillary first molars. The upper right first molars were stimulated with LIPUS (30 mW/cm², 1.5 MHz) for 20 min/d. The cavities prepared in the left teeth were used as experimental controls (i.e., no LIPUS). Five rats in each group were sacrificed at days 1, 3, 5, 7 and 14. Inflammatory response was visible at different time points after cavity preparation, peaking at day 3, after which it gradually weakened. More reparative dentin was found on the LIPUS treatment side. transforming growth factor-β1 expression increased after treatment, peaking at day 5 and returning to normal at day 14 on both sides, but was stronger with LIPUS treatment. SMAD2 and SMAD3 expressions in the dental pulp gradually increased after cavity preparation, especially in the experimental group. LIPUS promoted the repair of dentin–pulp complex injury, to a certain extent and should be investigated further as a potential therapy.