A dynamical systems model for the measurement of cellular senescence

Senescent cells provide a good in vitro model to study ageing. However, cultures of ‘senescent’ cells consist of a mix of cell subtypes (proliferative, senescent, growth-arrested and apoptotic). Determining the proportion of senescent cells is crucial for studying ageing and developing new anti-degenerative therapies. Commonly used markers such as doubling population, senescence-associated β-galactosidase, Ki-67, γH2AX and TUNEL assays capture diverse and overlapping cellular populations and are not purely specific to senescence. A newly developed dynamical systems model follows the transition of an initial culture to senescence tracking population doubling, and the proportion of cells in proliferating, growth-arrested, apoptotic and senescent states. Our model provides a parsimonious description of transitions between these states accruing towards a predominantly senescent population. Using a genetic algorithm, these model parameters are well constrained by an in vitro human primary fibroblast dataset recording five markers at 16 time points. The computational model accurately fits to the data and translates these joint markers into the first complete description of the proportion of cells in different states over the lifetime. The high temporal resolution of the dataset demonstrates the efficacy of strategies for reconstructing the trajectory towards replicative senescence with a minimal number of experimental recordings.

Transient induction of telomerase expression mediates senescence and reduces tumorigenesis in primary fibroblasts

Telomerase is an enzymatic ribonucleoprotein complex that acts as a reverse transcriptase in the elongation of telomeres. Telomerase activity is well documented in embryonic stem cells and the vast majority of tumor cells, but its role in somatic cells remains to be understood. Here, we report an unexpected function of telomerase during cellular senescence and tumorigenesis. We crossed Tert heterozygous knockout mice (mTert+/−) for 26 generations, during which time there was progressive shortening of telomeres, and obtained primary skin fibroblasts from mTert+/+ and mTert−/− progeny of the 26th cross. As a consequence of insufficient telomerase activities in prior generations, both mTert+/+ and mTert−/− fibroblasts showed comparable and extremely short telomere length. However, mTert−/− cells approached cellular senescence faster and exhibited a significantly higher rate of malignant transformation than mTert+/+ cells. Furthermore, an evident up-regulation of telomerase reverse-transcriptase (TERT) expression was detected in mTert+/+ cells at the presenescence stage. Moreover, removal or down-regulation of TERT expression in mTert+/+ and human primary fibroblast cells via CRISPR/Cas9 or shRNA recapitulated mTert−/− phenotypes of accelerated senescence and transformation, and overexpression of TERT in mTert−/− cells rescued these phenotypes. Taking these data together, this study suggests that TERT has a previously underappreciated, protective role in buffering senescence stresses due to short, dysfunctional telomeres, and preventing malignant transformation.

Grammatophyllum speciosum Ethanolic Extract Promotes Wound Healing in Human Primary Fibroblast Cells

Grammatophyllum speciosum is a plant in Orchidaceae family which contains a variety of phytochemical compounds that might be beneficial for medicinal use. This study aimed to evaluate the activity of pseudobulb of G. speciosum extract (GSE) in wound healing processes in human primary fibroblast cells along with in vitro antioxidant activity and total phenolic content of GSE. Scratch wound healing assay indicated that GSE was capable of increasing migration rate after 6 and 9 hours of treatment. Besides, the extract was able to scavenge DPPH, ABTS, and superoxide anion radicals indicating the antioxidative property of GSE. This study suggested a novel role of the of pseudobulb extract of G. speciosum as a wound healing enhancer. The results from this study might be beneficial for the development of further novel active compounds for skin wound healing.

Uteroglobin, a Possible Ligand of the Lipoxin Receptor Inhibits Serum Amyloid A-Driven Inflammation

Serum amyloid A (SAA) production is increased by inflamed arthritic synovial tissue, where it acts as a cytokine/chemoattractant for inflammatory and immune cells and as an inducer of matrix degrading enzymes. SAA has been shown to bind lipoxin A4receptor, a member of the formyl-peptide related 2 G-protein coupled receptor family (ALX) and elicit proinflammatory activities in human primary fibroblast-like synoviocytes (FLS). We report on the identification of uteroglobin, a small globular protein with potent anti-inflammatory activities, as a possible ligand of ALX. Uteroglobin-specific association with ALX was demonstrated by an enzyme immunoassay experiment employing a cell line engineered to express the human ALX receptor. Uteroglobin’s interaction with ALX resulted in the inhibition of SAA responses, such as attenuation of phospholipase A2activation and cellular chemotaxis. In FLS, uteroglobin showed an antagonism against SAA-induced interleukin-8 release and decreased cell migration. These novel roles described for uteroglobin via ALX may help elucidate genetic and clinical observations indicating that a polymorphism in the uteroglobin promoter is linked to disease outcome, specifically prediction of bone erosion in patients with rheumatoid arthritis or severity of IgA glomerulonephritis and sarcoidosis.

Expression of the familial Mediterranean fever gene and activity of the C5a inhibitor in human primary fibroblast cultures

Familial Mediterranean fever (FMF) is an inherited disease whose manifestations are acute but reversible attacks of sterile inflammation affecting synovial and serosal spaces. The FMF gene (MEFV) was recently cloned, and it codes for a protein (pyrin/marenostrin) homologous to known nuclear factors. We previously reported the deficient activity of a C5a/interleukin (IL)–8 inhibitor, a physiologic regulator of inflammatory processes, in FMF serosal and synovial fluids. We now describe the concomitant expression ofMEFV and C5a/IL-8–inhibitor activity in primary cultures of human fibroblasts. Fibroblasts grown from synovial and peritoneal tissues displayed C5a/IL-8–inhibitor activity that could be further induced with phorbol myristate acetate (PMA) and IL-1β. Very low levels of chemotactic inhibitor were evident in skin fibroblast cultures or in peritoneal and skin fibroblasts obtained from FMF patients. MEFV was expressed in peritoneal and skin fibroblasts at a lower level than in neutrophils and could be further induced by PMA and IL-1β. In the FMF cultures, the MEFV transcript carried the M694V mutation, consistent with the genetic defect found in patients with this disease. MEFV was also expressed in other cell lines that do not produce C5a/IL-8 inhibitor. These findings suggest that human primary fibroblast cultures express MEFV and produce C5a/IL-8–inhibitor activity. The interrelationship between pyrin, the MEFV product, and the C5a/IL-8 inhibitor requires further investigation.

Expression of the familial Mediterranean fever gene and activity of the C5a inhibitor in human primary fibroblast cultures

Familial Mediterranean fever (FMF) is an inherited disease whose manifestations are acute but reversible attacks of sterile inflammation affecting synovial and serosal spaces. The FMF gene (MEFV) was recently cloned, and it codes for a protein (pyrin/marenostrin) homologous to known nuclear factors. We previously reported the deficient activity of a C5a/interleukin (IL)–8 inhibitor, a physiologic regulator of inflammatory processes, in FMF serosal and synovial fluids. We now describe the concomitant expression ofMEFV and C5a/IL-8–inhibitor activity in primary cultures of human fibroblasts. Fibroblasts grown from synovial and peritoneal tissues displayed C5a/IL-8–inhibitor activity that could be further induced with phorbol myristate acetate (PMA) and IL-1β. Very low levels of chemotactic inhibitor were evident in skin fibroblast cultures or in peritoneal and skin fibroblasts obtained from FMF patients. MEFV was expressed in peritoneal and skin fibroblasts at a lower level than in neutrophils and could be further induced by PMA and IL-1β. In the FMF cultures, the MEFV transcript carried the M694V mutation, consistent with the genetic defect found in patients with this disease. MEFV was also expressed in other cell lines that do not produce C5a/IL-8 inhibitor. These findings suggest that human primary fibroblast cultures express MEFV and produce C5a/IL-8–inhibitor activity. The interrelationship between pyrin, the MEFV product, and the C5a/IL-8 inhibitor requires further investigation.