Senescent hepatocyte secretion of matrix metalloproteinases is regulated by nuclear factor-κB signaling

The Role of Stem Cells as Therapeutics for Ischaemic Stroke

Stroke remains one of the leading causes of death and disability worldwide. Current reperfusion treatments for ischaemic stroke are limited due to their narrow therapeutic window in rescuing ischaemic penumbra. Stem cell therapy offers a promising alternative. As a regenerative medicine, stem cells offer a wider range of treatment strategies, including long-term intervention for chronic patients, through the reparation and replacement of injured cells via mechanisms of differentiation and proliferation. The purpose of this review is to evaluate the therapeutic role of stem cells for ischaemic stroke. This paper discusses the pathology during acute, subacute, and chronic phases of cerebral ischaemic injury, highlights the mechanisms involved in mesenchymal, endothelial, haematopoietic, and neural stem cell-mediated cerebrovascular regeneration, and evaluates the pre-clinical and clinical data concerning the safety and efficacy of stem cell-based treatments. The treatment of stroke patients with different types of stem cells appears to be safe and efficacious even at relatively higher concentrations irrespective of the route and timing of administration. The priming or pre-conditioning of cells prior to administration appears to help augment their therapeutic impact. However, larger patient cohorts and later-phase trials are required to consolidate these findings.

Structural dysregulation of the pulmonary autograft was associated with a greater density of p16INK4A-vascular smooth muscle cells

The present study tested the hypothesis that a senescent phenotype of vascular smooth muscle cells (VSMCs) may represent the seminal event linked to maladaptive pulmonary autograft remodeling of a small number of patients that underwent the Ross procedure. The diameter of the pulmonary autograft (47±4 mm) of three male patients was significantly greater compared to the pulmonary artery (26±1 mm) excised from bicuspid aortic valve (BAV) patients. The pulmonary autograft was associated with a neointimal region and the adjacent medial region was significantly thinner compared to the pulmonary artery of BAV patients. Structural dysregulation was evident as elastin content of the medial region was significantly reduced in the pulmonary autograft compared to the pulmonary artery of BAV patients. By contrast, collagen content of the medial region of the pulmonary autograft and the pulmonary artery of BAV patients was not significantly different. Reduced medial elastin content of the pulmonary autograft was associated with increased protein levels of matrix metalloproteinase-9. The latter phenotype was not attributed to a robust inflammatory response as the percentage of Mac-2⁽⁺⁾-infiltrating monocytes/macrophages was similar between groups. A senescent phenotype was identified as protein levels of the cell cycle inhibitor p27^kip1 were upregulated and the density of p16^INK4A/non-muscle myosin IIB⁽⁺⁾-VSMCs was significantly greater in the pulmonary autograft compared to the pulmonary artery of BAV patients. Thus, senescent VSMCs may represent the predominant cellular source of increased matrix metalloproteinase-9 protein expression translating to maladaptive pulmonary autograft remodeling characterized by elastin degradation, medial thinning and neointimal formation.

The ascending aorta of male hypertensive bicuspid aortic valve patients preferentially associated with a cellular aneurysmal phenotype

Male sex and hypertension represent risk factors in the progression of an aortic aneurysm. The present study examined the morphological/cellular phenotype of the ascending aorta (AA) of male and female patients diagnosed with a bicuspid aortic valve (BAV) to test the hypothesis that hypertension-induced remodeling of male BAV patients preferentially recapitulated the expression of a panel of proteins favoring aneurysm formation. The diameter of the AA of hypertensive male (35 ± 6 mm) and female (39 ± 5 mm) BAV patients was comparable to normotensive patients reflecting an early phase of vessel expansion. Morphological/structural remodeling of the medial region of the AA of male normotensive and hypertensive BAV patients were comparable. Protein levels of non-muscle myosin IIB, the cell cycle inhibitor p27kip1, tumor suppressor p53 and matrix metalloproteinase-2 and -9 were significantly upregulated in the AA of male hypertensive BAV patients. In female hypertensive BAV patients, collagen content was significantly increased whereas elastin content and medial width of the AA were similar to normotensive BAV patients. In the AA of female hypertensive BAV patients, matrix metalloproteinase-9 and p27kip1 protein levels were unchanged whereas p53 and matrix metalloproteinase-2 protein expression was significantly reduced. Nestin protein levels were diminished in the AA of male and female hypertensive BAV patients. Thus, sexual dimorphic remodeling of the AA was prevalent in hypertensive BAV patients. Moreover, during the early phase of vessel expansion, the AA of male hypertensive BAV patients was preferentially associated with the upregulation of a panel of proteins linked to progressive dilatation and potential aneurysm formation.

Why Senescent Cells Are Resistant to Apoptosis: An Insight for Senolytic Development

Cellular senescence is a process that leads to a state of irreversible cell growth arrest induced by a variety of intrinsic and extrinsic stresses. Senescent cells (SnCs) accumulate with age and have been implicated in various age-related diseases in part via expressing the senescence-associated secretory phenotype. Elimination of SnCs has the potential to delay aging, treat age-related diseases and extend healthspan. However, once cells becoming senescent, they are more resistant to apoptotic stimuli. Senolytics can selectively eliminate SnCs by targeting the SnC anti-apoptotic pathways (SCAPs). They have been developed as a novel pharmacological strategy to treat various age-related diseases. However, the heterogeneity of the SnCs indicates that SnCs depend on different proteins or pathways for their survival. Thus, a better understanding of the underlying mechanisms for apoptotic resistance of SnCs will provide new molecular targets for the development of cell-specific or broad-spectrum therapeutics to clear SnCs. In this review, we discussed the latest research progresses and challenge in senolytic development, described the significance of regulation of senescence and apoptosis in aging, and systematically summarized the SCAPs involved in the apoptotic resistance in SnCs.

Senescent hepatocytes enhance natural killer cell activity via the CXCL-10/CXCR3 axis

Cellular senescence and natural killer (NK) cells play an important role in liver diseases. Chemokines, a component of the senescence-associated secretory phenotype, can recruit NK cells and are involved in the development of various liver diseases. The effect of the C-X-C motif chemokine ligand (CXCL)-9, −10, −11/C-X-C motif chemokine receptor (CXCR)3 axis in senescent hepatocytes remains unknown. The chemokines secreted by senescent hepatocytes, the contribution of the CXCL-9, −10, −11/CXCR3 axis to the migration of NK cells, and the effect of senescent hepatocytes on the function of NK cells were investigated in the present study. The results demonstrated significantly increased levels of C-C motif chemokine ligand 2 and CXCL-1, −2 and −10 in the supernatant of senescent AML12 cells. Despite increased mRNA expression of CXCL-9, −10, and −11 in these cells, western blotting revealed significantly enhanced expression of only CXCL-10. The expression of CXCR3 on the surface of NK cells stimulated by senescent AML12 cells was upregulated (fold change, >3). Following incubation with the supernatant of senescent hepatocytes, both CD107a and interferon γ expression in NK cells increased by >2.5-fold. The cytotoxic effect of NK cells was notably higher stimulated by senescent AML12 cells. Chemotaxis and blocking assays demonstrated that the senescent hepatocytes enhanced the migration of NK cells via the CXCL-10/CXCR3 axis. The present study suggests that senescent hepatocytes secrete various chemokines, including CXCL-10, resulting in the upregulation and activation of CXCR3 in NK cells and the enhancement of NK cell migration via the CXCL-10/CXCR3 axis.