Selective targeting of dipeptidyl-peptidase 4 (DPP-4) positive senescent chondrocyte ameliorates osteoarthritis progression.

Senescent cells increase in many tissues with age and induce age-related pathologies, including osteoarthritis (OA). Senescent chondrocytes (SnCs) are found in OA cartilage, and the clearance of those chondrocytes prevents OA progression. However, targeting SnCs is challenging due to the absence of a senescent chondrocyte-specific marker. Therefore, we used flow cytometry to screen and select senescent chondrocyte surface markers and cross-validated with published transcriptomic data. Chondrocytes expressing dipeptidyl peptidase-4 (DPP-4), the selected senescent chondrocyte-specific marker, had multiple senescence phenotypes, such as increased senescence-associated-galactosidase, p16, p21, and senescence-associated secretory phenotype expression, and showed OA chondrocyte phenotypes. To examine the effects of DPP-4 inhibition on DPP-4+ SnCs, sitagliptin, a DPP-4 inhibitor, was treated in vitro. As a result, DPP-4 inhibition selectively eliminates DPP-4+ SnCs without affecting DPP-4- chondrocytes. To assess in vivo therapeutic efficacy of targeting DPP-4+ SnCs, three known senolytics (ABT263, 17DMAG, and metformin) and sitagliptin were comparatively verified in a DMM-induced rat OA model. Sitagliptin treatment specifically and effectively eliminated DPP-4+ SnCs, compared to the other three senolytics. Furthermore, Intra-articular sitagliptin injection to the rat OA model increased collagen type II and proteoglycan expression and physical functions and decreased cartilage destruction, subchondral bone plate thickness and MMP13 expression, leading to the amelioration of OA phenotypes. Collectively, OARSI score was lowest in the sitagliptin treatment group. Taken together, we verified DPP-4 as a surface marker for SnCs and suggested that the selective targeting of DPP-4+ chondrocytes could be a promising strategy to prevent OA progression.

Application of droplet digital PCR method for DNA methylation-based age prediction from saliva.

The recent studies reported that DNA methylation markers show changes with age, and expected that the DNA methylation markers can be effectively used for estimation of age in forensic genetics. In this study, we applied droplet digital PCR (ddPCR) method to investigate the DNA methylation pattern in the CpG sites, and we constructed an age prediction model based on the ddPCR method. The ddPCR is capable of highly sensitive quantitation of nucleic acid and detection of sequence variations in gene by separating the sample into large number of partitions and clonally amplifying nucleic acids in each partition. We extracted DNA from saliva samples collected from several age groups. The DNA was bisulfite converted and subjected to ddPCR using specifically designed primers and probes. The methylation ratio of each sample was calculated and correlation between the methylation ratio and the chronological age was analyzed. In the results, methylated DNA ratio at the 4 CpG sites (cg14361627, cg14361627, cg08928145 and cg07547549) showed strong correlation with chronological age. Percent-methylation values at 4 CpG markers and chronological ages of the 76 individuals were analyzed by multiple regression analysis, and we constructed an age prediction model. We observed a strong correlation (Spearman's rho = 0.922) between predicted and chronological ages of 76 individuals with a MAD from chronological age of 3.3 years. Collectively, the result in this study showed the potential applicability of ddPCR to predict age from saliva.

The Insertion/Deletion Polymorphism of Angiotensin I Converting Enzyme Gene is Associated With Ossification of the Posterior Longitudinal Ligament in the Korean Population.

OBJECTIVE: To determine whether ACE insertion/deletion (I/D) polymorphism is associated with the ossification of the posterior longitudinal ligament (OPLL) of the spine in the Korean population. METHODS: A case-control study was conducted to investigate the association between I/D polymorphism of the angiotensin I converting enzyme (peptidyl-dipeptidase A) 1 (ACE) gene and OPLL. The 95 OPLL patients and 274 control subjects were recruited. Polymerase chain reaction for the genotyping of ACE I/D polymorphism was performed. The difference between the OPLL patients and the control subjects was compared using the contingency χ(2) test and the logistic regression analysis. For statistical analysis, SPSS, SNPStats, SNPAnalyzer, and Helixtree programs were used. RESULTS: The genotype and allele frequencies of ACE I/D polymorphism showed significant differences between the OPLL patients and the control subjects (genotype, p<0.001; allele, p=0.009). The frequencies of D/D genotype and D allele in the OPLL group were higher than those in the control group. In logistic regression analysis, ACE I/D polymorphism was associated with OPLL (dominant model; p=0.002; odd ratio, 2.20; 95% confidence interval, 1.33-3.65). CONCLUSION: These results suggest that the deletion polymorphism of the ACE gene may be a risk factor for the development of OPLL in the Korean population.

Expression of autotaxin (NPP-2) is closely linked to invasiveness of breast cancer cells.

Autotaxin (ATX), originally isolated from human melanoma cells, is a novel metastasis-enhancing motogen and angiogenesis factor. In the present study, we compared the expression level of ATX mRNA between normal and breast cancer tissues and found that the expression of ATX mRNA was closely linked to invasiveness of cancer cells. Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemical analysis showed higher cellular ATX mRNA expression in the cancer than normal breast tissues. MDA-MB-435S breast cancer cells, expressing higher amount of ATX mRNA, showed greater relative invasiveness to fibroblast-conditioned medium (FCM) than MCF7, MDA-MB-231, and HBL-100 breast cancer cells. Furthermore, ATX-transfected MCF7 cells showed increased motility and invasiveness than vector-transfected MCF7 cells. Collectively, our results suggest that the expression of ATX is closely linked to the invasiveness of breast cancer cells.