Role of interaction between reactive oxygen species and ferroptosis pathway in methylglyoxal-induced injury in mouse embryonic osteoblasts / 南方医科大学学报

OBJECTIVE@#To explore the interaction between reactive oxygen species (ROS) and ferroptosis in methylglyoxalinduced injury of mouse embryonic osteoblasts (MC3T3-E1 cells).@*METHODS@#MC3T3-E1 cells were treated with methylglyoxal to establish a cell model of diabetic osteoporosis. CCK-8 assay was used to detect the viability of MC3T3-E1 cells. Rhodamine 123 staining followed by photofluorography was used to examine mitochondrial membrane potential (MMP). The intracellular ROS level was detected by 2', 7'-dichlorodihydrofluorescein diacetate staining with photofluorograph. Alkaline phosphatase (ALP) activity in the cells was detected using an ALP kit, the number of mineralized nodules was determined with alizarin red S staining, and the level of iron ions was detected using a detection kit. The expression level of glutathione peroxidase 4 (GPX4, a marker protein that inhibits ferroptosis) in the osteoblasts was determined using Western blotting.@*RESULTS@#Treatment of MC3T3-E1 cells with 0.6 mmol/L methylglyoxal for 24 h significantly inhibited the expression level of GPX4 (P < 0.001), increased intracellular iron ion concentration, decreased the cell viability, increased the loss of MMP and intracellular ROS level, decreased both ALP activity and the number of mineralized nodules in the cells (P < 0.001). Co-treatment of MC3T3-E1 cells with 2 mmol/L N-acetylcysteine (NAC, a ROS scavenger) and methylglyoxal significantly increased the expression level of GPX4 (P < 0.01); co-treatment with 4 mmo/L FER-1 (a ferroptosis inhibitor) and methylglyoxal obviously decreased the intracellular ROS level (P < 0.001). Co-treatment of the cells either with NAC and methylglyoxal or with FER-1 and methylglyoxal attenuated methylglyoxal-induced injuries in the osteoblasts (P < 0.001).@*CONCLUSION@#The interaction between ROS and ferroptosis pathway plays an important role in methylglyoxal-induced injury of mouse embryonic osteoblasts.

Acupuncture combined with / 中国针灸

OBJECTIVE@#To observe the efficacy of acupuncture combined with @*METHODS@#A total of 180 children with cerebral palsy were randomly divided into a combined group (60 cases, 2 cases dropped off), an acupuncture group (60 cases, 4 cases dropped off) and a Chinese medication group (60 cases, 5 cases dropped off). On the basis of conventional treatment, the children in the combined group were treated with acupuncture [Baihui (GV 20), Sishencong (EX-HN 1), Shenting (GV 24), Benshen (GB 13), 30 min each time, twice a day] and @*RESULTS@#The total effective rate was 91.4% (53/58) in the combined group, which was higher than 80.4% (45/56) in the acupuncture group and 78.2% (43/55) in the Chinese medication group (@*CONCLUSION@#Acupuncture combined with

Changes in Metabolism and Function of Platelets Stored at Different Temperature / 中国实验血液学杂志

@#AAbstractObjective:To compare and analyze the metabolic and functional changes in platelets stored at 4 ℃ and ones stored at 22 ℃ with agitation so as to provide an experimental basis for the cryopreservation technology of platelets.@*METHODS@#Samples were collected from platelets stored at 4 ℃ in 2, 4, 6, 11, 15 and 21 days, and from ones stored at 22 ℃ with agitation during the same days, the metabolism indicators and thromboelastogram (TEM) were analysed.@*RESULTS@#In metabolism, there were no significant changes of pH, GLU，PCO2, PCO2 and MPV levels of platelets stored at 4 ℃ for <6 days (P＞0.05), However, the Plt count decreased, the PDW and LDH level incrseased (P＜0.05). At the same time, only MPV had no changes of platelets stored at 22 ℃ during above-mentioned same days (P＞0.05), while the pH, PCO2, GLU, Plt all decreased, and PO2, LDH, PDW incrseased (P＜0.05). There were significant changes about the pH value, PO2, Plt, MPV, LDH, GLU levels between the two kinds of stored platelets during the same storing period (P＜0.05). The pH value and MPV of platelets stored at 4 ℃ were obviously lower than ones stored at 22 ℃, while GLU, PO2, LDH and Plt levels showed reverse changes (P＜0.05). Meanwhile, the PCO2 of platelets stored at 4 ℃ not could be detected and the Plt count reduced rapidly from d15. In function, the MA level of platelets stored at 4 ℃ was slower than that of platelets stored at 22 ℃, that is, the MA level of platelets stored at 4 ℃ were higher than that of platelets stored at 22 ℃ during the same storeing period (P＜0.05).@*CONCLUSION@#Platelets stored at 4 ℃ have much slower metabolism than ones stored at 22 ℃, and the aggregation is stronger of platelets stored at 4 ℃ than that of ones at 22 ℃ during the same conservation period.

Influence of the Right Ventricular Lead Location on Ventricular Arrhythmias in Cardiac Resynchronization Therapy / 中华医学杂志(英文版)

<p><b>Background</b>The influence of different right ventricular lead locations on ventricular arrhythmias (VTA) in patients with a cardiac resynchronization therapy (CRT) is not clear. This study aimed to evaluate the influence on VTA in patients with a CRT when right ventricular lead was positioned at the right ventricular middle septum (RVMS) and the right ventricular apical (RVA).</p><p><b>Methods</b>A total of 352 patients implanted with a CRT-defibrillator (CRT-D) between May 2012 and July 2016 in the Department of Cardiology of Anhui Provincial Hospital were included. Two-year clinical and pacemaker follow-up data were collected to evaluate the influence of the right ventricular lead location on VTA. Patients were divided into the RVMS group (n = 155) and the RVA group (n = 197) based on the right ventricular lead position. The VTA were compared between these two groups using a Kaplan-Meier curve and Cox multivariate analysis.</p><p><b>Results</b>When the left ventricular lead location was not considered, RVMS and RVA locations did not affect VTA. However, the subgroup analysis results showed that when the left ventricular lead was positioned at the anterolateral cardiac vein (ALCV), the RVMS group had an increased risk of ventricular arrhythmias and appropriate defibrillation (hazard ratio [HR] = 3.29, P = 0.01 and HR = 4.33, P < 0.01, respectively); when the left ventricular lead was at the posterolateral cardiac vein (PLCV), these risks in the RVMS group decreased (HR = 0.45, P = 0.02 and HR = 0.33, P < 0.01, respectively), and when the left ventricular lead was at the lateral cardiac vein, there was no difference between the two groups. In regard to inappropriate defibrillation, there was no significant difference among all these groups.</p><p><b>Conclusions</b>When the left ventricular lead was positioned at ALCV or PLCV, the right ventricular lead location was associated with VTA and appropriate defibrillation after CRT. Greater distances between leads not only improved cardiac function but also may reduce the risk of VTA.</p>

Bone morphogenetic protein 2-induced human dental pulp cell differentiation involves p38 mitogen-activated protein kinase-activated canonical WNT pathway / 国际口腔科学杂志·英文版

Both bone morphogenetic protein 2 (BMP2) and the wingless-type MMTV integration site (WNT)/β-catenin signalling pathway play important roles in odontoblast differentiation and dentinogenesis. Cross-talk between BMP2 and WNT/β-catenin in osteoblast differentiation and bone formation has been identified. However, the roles and mechanisms of the canonical WNT pathway in the regulation of BMP2 in dental pulp injury and repair remain largely unknown. Here, we demonstrate that BMP2 promotes the differentiation of human dental pulp cells (HDPCs) by activating WNT/β-catenin signalling, which is further mediated by p38 mitogen-activated protein kinase (MAPK) in vitro. BMP2 stimulation upregulated the expression of β-catenin in HDPCs, which was abolished by SB203580 but not by Noggin or LDN193189. Furthermore, BMP2 enhanced cell differentiation, which was not fully inhibited by Noggin or LDN193189. Instead, SB203580 partially blocked BMP2-induced β-catenin expression and cell differentiation. Taken together, these data suggest a possible mechanism by which the elevation of β-catenin resulting from BMP2 stimulation is mediated by the p38 MAPK pathway, which sheds light on the molecular mechanisms of BMP2-mediated pulp reparative dentin formation.

Comparison of bonding properties of five adhesives in primary dentin / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the microtensile bond strength (µTBS) of five dentin adhesives and their respective fracture modes.</p><p><b>METHODS</b>The flat dentine surfaces of 75 primary teeth were randomly divided into five groups,which was treated with FL-BondII(group A), Clearfil Protect Bond(group B), Clearfil SE Bond(group C), Adper(TM) Easy One(group D), and Single Bond 2(group E) respectively. The µTBS was determined with microtensile tester and the fracture mode was observed by scanning electron microscope(SEM).</p><p><b>RESULTS</b>The mean µTBS for group A,B,C,D and E was (28.3 ± 2.2), (32.4 ± 2.5), (38.3 ± 2.8), (32.9 ± 3.4) and (23.2 ± 1.9) MPa respectively. There was significant difference between group C and group A,E (P < 0.01), and no significant difference between group C and group B,D. There was no significant difference between group A and group E (P > 0.05). The SEM indicated that there was no significant difference in the fracture mode.</p><p><b>CONCLUSIONS</b>The bonding property of Clearfil Protect Bond is equivalent to Clearfil SE Bond and Adper(TM) Easy One, superior to Single Bond 2 and more suitable for primary dentin bonding .</p>

Neuroprotective effect of epigallocatechin-3-gallate on lateral geniculate nucleus after optic nerve crush in rats / 中华实验眼科杂志

Background Researches demonstrated that epigallocatechin-3-gallate(EGCG) can protect retinal ganglion cells(RGCs) against damage induced by retinal ischemia-reperfusion and optic nerve crush(ONC),but the effect of EGCG on lateral geniculate nucleus(LGN) was under study.Objective This study was designed to detect neuroprotective effect of EGCG on LGN in the rat model with ONC.Methods Forty-eight 7-week-old female clean Wistar rats were randomly divided into normal control group,sham operation+EGCG group,ONC+normal saline(NS) group and ONC+EGCG group.ONC models were created by clamping the optical nerve for 60 seconds with the clipper with the force of 40 grams in the right eyes of 24 rats.The EGCG solution(25mg/kg) was intraperitoneally injected from 2 days before operation daily for 5 consecutively days and orally administered(2mg/kg) after that,and NS was used in the same way for ONC+NS group.Four weeks after ONC,the brain tissue of the rats was obtained,and the neurons of dorsal LGN(dLGN) were counted by Nissl staining under the light microscopy.The expression of neurofilament triplet L(NF-L) was detected by immunohistochemistry and Western blot analysis.Meanwhile,the neuronal nitric oxide synthase(nNOS) positive cells were counted.Results Compared with normal control group,no significant differences were found in neuron number both between sham operation+EGCG group or ipsilateral LGN of operative eyes in ONC+normal saline group and ONC+EGCG group(P=0.906,0.561,0.794,0.646 respectively) in 4 weeks after ONC,but loss of neurons in contralateral LGN in both ONC+normal saline group and ONC+EGCG group were observed(P=0.000,0.015 respectively).However,compared with ONC+normal saline group,the density of neurons in ONC+EGCG group was higher(P=0.007).Moreover,a higher expression level of NF-L protein was seen in ONC+EGCG group compared with ONC+normal saline group at contralateral LGN of operative eyes(P=0.002).Concerning the number of nNOS positive cells in LGN,there was no significant difference among normal control group,sham operation+EGCG group and ONC+EGCG group(P＞0.05).The number of nNOS positive cells in the contralateral LGN of operative eyes of ONC+normal saline group was higher than that of ONC+EGCG group(P=0.000).Conclusion EGCG plays the protective effect on LGN after ONC in rats through mediating the expression of nNOS.

Effects of epigallocatechin-3-gallate on expression of glial fibrillary acidic protein in optic nerve crush model / 中华实验眼科杂志

Background Our previous study demonstrated that epigallocateehin-gallate(EGCG),an active ingredient of green tea,has protective effect on optical nerve after optic nerve crush.Astrocyte was proved to play key role in the repair of nerve tissue,but the influence of EGCG on astrocyte is unclear.Glial flbrillary acidic protein (GFAP) is a special marker for astrocyte. Objective The aim of this study was to investigate the effect of EGCG on the expression of GFAP in optic nerve tissue after optic nerve crush. Methods Seventy-two clean Wistar rats were randomly divided into normal control group,sham+EGCG group,optic nerve crush+normal saline group(vehicle group),optic nerve crush+EGCG group.Optic nerve crush models were established by clamping optical nerve for 60 seconds by minitype optic nerve clipper with the force of 40 gram.Only ocular tissue was cut in the rats in sham group.Normal saline solution or EGCG(25 mg/kg)was intraperitoneally injected daily for 5 days consecutively and orally administered(2 mg/kg)daily afterwards.The expression of GFAP in optic nerve was detected by immunohistochemistry and quantified by Western blotting analysis on day 7,14 and 28 after modeling. Results lmmunochemistry showed that GFAP were weakly expressed in the rats of both normal group and sham+EGCG group with the sliSht brown staining in optic nerve tissue.The deeply brown staining for GFAP was seen in vehicle group,and the staining intensity weakened in optic nerve crush+EGCG group compared to vehicle group on days 7,14 and 28 after modeling.Western blotting analysis revealed that the expression level of GFAP in rat optic nerve tissue of vehicle group was significantly enhanced in comparison with normal control group(P＜0.01).On day 7 and 14 after optic nerve modeling,the expression levels of GFAP were evidently decreased in optic nerve crush+EGCG group in comparison with vehicle group(P＜0.05).However,on day 28 after modeling,no significant difference wag found in the expression levels of GFAP between vehicle group and optic nerve erush+EGCG group(P＞0.05). Conclusion EGCG down-regulates optic nerve crush-induced of GFAP in the optic nerve and therefore attenuates the activity of astrocytes,suggesting that EGCG might reduce the formation of glial scar.

Effect on expression of vascular smooth muscle cell calcium channel in rats exposed in low temperature / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To observe the expression of vascular smooth muscle cells calcium channel α1C subunit (LTCCα1C) in rats exposed in low temperature.</p><p><b>METHODS</b>Cold-induced hypertension was established and blood pressure was measured every two weeks. The mRNA expression of L type calcium channel α1C was determined by RT-PCR.</p><p><b>RESULTS</b>The blood pressure of the rats exposed to cold environment increased. The blood pressure of experimental groups [(102.8 ± 2.25) mm Hg] began to increase from the first two weeks, compared with the control group [(89.2 ± 3.73) mm Hg], there were significant difference (P < 0.05). The blood pressure of experimental groups were (114.5 ± 4.21), (121.9 ± 3.03) mm Hg respectively at 4, 6 weeks. Compared with the control group, the expression of LTCCα1C mRNA of the cold exposure group increased significantly (P < 0.01). There was a significant correlation between the expression of LTCCα1C mRNA and the blood pressure of the rats (r = 0.86, P < 0.01).</p><p><b>CONCLUSION</b>Repeated cold exposure can establish cold-induced hypertension, and the level of vascular smooth muscle cells LTCCα1C expression increase.</p>

Clinicopathologic study of sinonasal inflammatory myofibroblastic tumor / 中华病理学杂志

<p><b>OBJECTIVE</b>To study the clinicopathologic features, immunophenotype and ultrastructural features of sinonasal inflammatory myofibroblastic tumors (IMT).</p><p><b>METHODS</b>The clinical and histologic features of 5 cases of sinonasal IMT were reviewed. Immunohistochemical study for vimentin, MSA, SMA, calponin, h-caldesmon, desmin, ALK, fibronectin, CK, S-100 and Ki-67 was carried out. Ultrastructural examination was also performed in two of the cases.</p><p><b>RESULTS</b>The patients age ranged from 28 to 62 years (mean = 43 years). The male-to-female ratio was 2:3. The clinical presentation included nasal obstruction, nasal discharge, nasal bleeding, facial pain, facial swelling, toothache and tear overflow. All of the 5 patients suffered from disease relapses; and 4 of them had recurrences for more than 5 times. One patient had lymph node metastasis and 3 patients died of the disease. Histologically, the tumor cells were arranged in interlacing fascicles and sometimes haphazard in fashion. They were spindly in shape, cytoplasm eosinophilic with mild nuclear atypia and a low mitotic activity. The intervening stroma was myxoid in appearance accompanied by lymphocyte and plasma cell infiltration, abundant blood vessels and focal collagenized areas. In 3 of the recurrent cases, the tumor cells displayed increased nuclear atypia and mitotic activity (average about 5 to 6 per 10 high-power fields), accompanied by patchy necrosis, less inflammatory cell infiltration and focal sarcomatous changes. Immunohistochemical study showed that the tumor cells were diffusely positive for vimentin. SMA, MSA, calponin and fibronectin were variably expressed. Desmin was weakly positive in 1 case. The staining for h-caldesmon, ALK, S-100 and CK was negative. The Ki-67 proliferation index increased with tumor recurrences. Electron microscopy revealed abundant rough endoplasmic reticulum and dense body formation in the cytoplasm. There were an increased amount of collagen fibers in the stroma.</p><p><b>CONCLUSIONS</b>IMT rarely occurs in nasal cavity and paranasal sinuses. The tumor is prone to local invasion and recurrences, with subsequent progression to frank malignancy and distant metastasis, resulting in high mortality and poor prognosis. Complete surgical resection remains the main modality of treatment.</p>

Pollutions of indoor fine particles in four types of public places and the influencing factors / 中华预防医学杂志

<p><b>OBJECTIVE</b>To study the levels of pollutions caused by fine particulate matter (PM(2.5)) in the public places and investigate the possible influencing factors.</p><p><b>METHODS</b>A total of 20 public places in four types such as rest room in bath center, restaurant, karaoke bars and cyber cafe in Tongzhou district in Beijing were chosen in this study; indoor and outdoor PM(2.5) was monitored by TSI sidepak AM510. Data under varying conditions were collected and analyzed, such as doors or windows or mechanical ventilation devices being opened, rooms cramped with people and smoking.</p><p><b>RESULTS</b>The average concentration of indoor PM(2.5) in 20 public places was (334.6 +/- 386.3) microg/m(3), ranging from 6 microg/m(3) to 1956 microg/m(3); while in bath center, restaurant, karaoke bars and cyber cafe were (116.9 +/- 100.1)microg/m(3), (317.9 +/- 235.3) microg/m(3), (750.6 +/- 521.6)microg/m(3) and (157.5 +/- 98.5) microg/m(3) respectively. The concentrations of PM(2.5) in restaurant (compared with bath center: Z = -10.785, P < 0.01; compared with karaoke bars: Z = -10.488, P < 0.01; compared with cyber cafe: Z = -7.547, P < 0.01) and karaoke bars (compared with bath center: Z = -16.670, P < 0.01; compared with cyber cafe: Z = -15.682, P < 0.01) were much higher than those in other two places. Single-factor analysis revealed that the average concentration of indoor PM(2.5) in 20 public places was associated with the number of smokers per cube meters(9.13 x 10(-3); r = 0.772, F = 26.579, P < 0.01) and ventilation score [(2.5 +/- 1.5) points; r = 0.667, F = 14.442, P < 0.01], and there were significant correlation between the average indoor and outdoor levels in restaurant [(317.9 +/- 235.3) microg/m(3), (67.8 +/- 78.9) microg/m(3); r = 0.918, F = 16.013, P = 0.028] and cyber cafe [(157.5 +/- 98.5) microg/m(3), (67.7 +/- 43.7) microg/m(3); r = 0.955, F = 30.785, P = 0.012]. Furthermore, significant correlation was observed between the average concentration of indoor PM(2.5) [(157.5 +/- 98.5) microg/m(3)]and the number of people per cube meters (288.7 x 10(-3)) in cyber cafe (r = 0.891, F = 11.615, P = 0.042). Multiple regression analysis showed that smoking (b' = 0.581, t = 3.542, P = 0.003) and ventilation (b' = -0.348, t = -2.122, P = 0.049) were the major factors that may influence the concentration of indoor PM(2.5) in four public places. With cluster analysis, the results showed that the major factors that influence the concentration of indoor PM(2.5) was the outdoor PM(2.5) levels [(49.6 +/- 39.5) microg/m(3); b = 1.556, t = 3.760, P = 0.007] when ventilation (score > 2) was relatively good. The number of smokers per cube meters (14.7 x 10(-3)) became the major influence factor when the ventilation score </= 2 (b = 140.957, t = 3.108, P = 0.013) and 51.8% increases of indoor PM(2.5) was attributed to smoking.</p><p><b>CONCLUSION</b>This study indicated that smoking was the main source of indoor PM(2.5) in public places. Outdoor PM(2.5) should be correlated with indoor PM(2.5) concentration under drafty situation.</p>

Characteristic Analysis of Cooperation Hydrogen Production Using Rhodopseudomonas sp. DT and Enterobacter Aerogenes / 微生物学通报

Cooperation hydrogen production was carried out using Rhodopseudomonas sp. DT and Enterobacter aerogenes. The effects of the initial ratio of Rhodopseudomonas sp. DT and E. aerogenes, culture temperature, and carbon source on the cooperation hydrogen production were investigated. The results suggested that cooperation hydrogen production rate was highly affected by the initial ratio of Rhodopseudomonas sp. DT and E. aerogenes. The mixed bacteria of Rhodopseudomonas sp. DT and E. aerogenes with 1:1 initial ratio benefited to the cooperation hydrogen production, which led the hydrogen production rate and duration of gas production to 3.1 mol H2/mol glucose and 81 h, respectively. The pH dynamics analysis of culture medium further discovered that the pH of the mixed bacteria with 1:1 initial ratio changed from 6 to 7 smaller than other conditions, which was probably fitted to produce hydrogen. Furthermore, the mixed bacteria with 1:1 initial ratio had the higher hydrogen production efficiency at temperatures of 28?C and 37?C than at 20?C, and without any hydrogen production at temperature of 50?C. The carbon sources of glucose, succinate acid, malic acid could be used to produce hydrogen by the mixed bacteria. Even the soluble starch, unused by Rhodopseudomonas sp. DT, was also decomposed by the mixed bacteria to produce hydrogen with the conversion efficiency of 8.22%. The glucose was the optimal carbon resource, and the conversion efficiency could reach to 36.11%. The results, further, implied that the cooperation hydrogen production could enlarge the use of the carbon sources.

Survey of TORCH Infection in Women before Pregnancy or in The Early Period of Pregnancy in Beijing / 中国康复理论与实践

@#ObjectiveTo investigate the positive rates of serum antibodies to TORCH in women who want to have a baby or in the early period of pregnancy.MethodsSerum TORCH-IgM or TORCH-IgG in 500 women were measured with IgM capture ELISA.ResultsThe positive rates of serum TORCH-IgM were 0 in TOX samples,0.2% in RV samples,0.2% in CMV samples,1.4% in COXB samples and 0 in HSV samples;while the positive rates of serum TORCH-IgG were 0.2% in TOX samples,51.6% in RV samples.ConclusionSerum TORCH-IgM and TORCH-IgG screening in women who want to be a mother or in the early period of pregnancy should be strengthened.

Effect of host derived matrix metalloproteinase on the degradation of root dentin collagen / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the effect of dentin matrix metalloproteinase (MMP) on the degradation of root dentin collagen.</p><p><b>METHODS</b>Root dentin powder was demineralized with acetic acid (pH 4.0) at 4 degrees C for 14 d, then dialysed and centrifuged. Precipitation was divided into 7 groups, with 6 samples in each group, and each sample was 50.0 mg. One milliliter artificial saliva with a different reagent was added in each sample respectively. The reagents were 2 mmol/L APMA (MMP activator), 2 mmol/L EDTA, 100 mmol/L EDTA, 200 mmol/L EDTA, 0.2% and 0.02% chlorhexidine (MMP inhibitor), and the blank artificial saliva was taken as control. The amount of degraded collagen of each sample was determined with hydroxyproline assay kit. Scanning electron microscope was employed to observe the morphological and structural changes of root dentin which was demineralized or put into artificial saliva after being demineralized.</p><p><b>RESULTS</b>The mean amount of degraded collagen in APMA group was significantly higher than that in the blank group (P < 0.05). The mean amount of degraded collagen in 2 mmol/L, 100 mmol/L, 200 mmol/L EDTA, 0.02% and 0.2% chlorhexidine groups was dramatically lower than that of the APMA group and the blank (P < 0.01). SEM observation indicated that the structural integrity of the collagen network on root surface dentin still existed in root dentin surface after being demineralized alone, while collagenous fibril was destructed and the structural integrity on root dentin surface disappeared after being demineralized and treated by artificial saliva.</p><p><b>CONCLUSIONS</b>MMP in root dentin can degrade root dentin collagen after being activated at low pH followed by neutralization. The results suggest that host MMP may play an important role in the process of dentin caries formation.</p>