Pin1-mediated regulation of articular cartilage stem/progenitor cell aging

Cartilage stem/progenitor cells (CSPCs) was recently isolated and identified from the cartilage tissue. CSPCs is essential for repair and regeneration of cartilage in osteoarthritis (OA). Aging is a primary risk factor for cartilage damage and joint OA. Although studies have confirmed the link between cell aging and OA, the underlying molecular mechanisms regulating CSPCs aging are not fully understood. In this study, we investigated the role of Pin1 in the aging of rat knee joint CSPCs. We isolated CSPCs from rat knee joints and demonstrated that, in long-term in vitro culture, Pin1 protein levels are significantly reduced. At the same time, expression of the senescence-related β-galactosidase and the senescence marker p16^INK4A were markedly elevated. In addition, Pin1 overexpression reversed the progression of cellular senescence, as evidenced by the down-regulation of senescence-related β-galactosidase, increased EdU positive cells and diminished levels of p16^INK4A. In contrast, Pin1 siRNA incorporation promoted CSPCs senescence. In addition, we also observed the distribution of cell cycles through flow cytometry and revealed that Pin1 deficiency results in cell cycle arrest in the G1 phase, suggesting severe lack of proliferation ability, a sign of cellular senescence. Collectively, these results validated that Pin1 is an essential regulator of CSPCs aging.

Human papillomavirus DNA in pharyngeal scrapes as a marker of HPV-related squamous cell cancer of the oropharynx

BACKGROUND

Recent studies have indicated that human papillomavirus is an etiologic agent for a subset of head and neck cancers associated with better prognosis, therefore, prompt confirmation of such etiology seems to be crucial for choosing the optimal therapeutic option. Standard HPV diagnosis is currently based on histopathological material. In the present study, the novel diagnostic method based on pharyngeal brush biopsy is proposed.

OBJECTIVES

The aim of this study was to evaluate the usefulness of the Real-Time PCR-based (RT-PCR) test in detecting HPV-related cancer of the oropharynx using superficial scraps taken from the oropharyngeal region.

STUDY DESIGN

Ninety patients with head and neck squamous cell cancer were enrolled in the study. The presence of HPV DNA in pharyngeal superficial scrapes assessed by RT-PCR was compared to the HPV status in the tumor tissue samples determined by a combined RT-PCR/P16(INK4A) expression algorithm. Analytical sensitivity and specificity were calculated and the clinical outcome was analyzed in correlation to the HPV status.

RESULTS

HR-HPV DNA in pharyngeal swabs was revealed in 25 cases (28.4%) and simultaneously confirmed in all corresponding tissue samples. Sensitivity and specificity of the viral status assessment in the brush biopsies in respect to the RT-PCR/P16(INK4A) 20 were 100% and 96.2%, respectively. HR-HPV positive status was associated with an excellent clinical outcome and reduced hazard ratio of recurrence and disease-related death.

CONCLUSIONS

The proposed novel method of HPV status assessment using RT-PCR and superficial scraps appeared to be highly sensitive, specific, and useful in predicting the clinical outcome.

p16(INK4A) mediates age-related changes in mesenchymal stem cells derived from human dental pulp through the DNA damage and stress response

Mesenchymal stem cells derived from human dental pulp (DP-MSCs) are characterized by self-renewal and multi-lineage differentiation, which play important roles in regenerative medicine. Autologous transfers, as non-immunogenic, constitute the safest approach in cellular transplantations. However, their use may be limited by age-related changes. In the study, we compared DP-MSCs isolated from human in five age groups: 5-12 y, 12-20 y, 20-35 y, 35-50 y, and >50 y. We tested the effect of age on proliferation, differentiation, senescence-associated β-galactosidase (SA-β-gal), cell cycle and programmed cell death. DP-MSCs showed characteristics of senescence as a function of age. Meanwhile, the expression of p16(INK4A) and γ-H2A.X significantly increased with age, whereas heat shock protein 60 (HSP60) was decreased in the senescent DP-MSCs. Reactive oxygen species (ROS) staining showed the number of ROS-stained cells and the DCFH fluorescent level were higher in the aged group. Further we examined the senescence of DP-MSCs after modulating p16(INK4A) signaling. The results indicated the dysfunction of DP-MSCs was reversed by p16(INK4A) siRNA. In summary, our study indicated p16(INK4A) pathway may play a critical role in DP-MSCs age-related changes and the DNA damage response (DDR) and stress response may be the main mediators of DP-MSCs senescence induced by excessive activation of p16(INK4A) signaling.