Aging: A cell source limiting factor in tissue engineering

Tissue engineering has yet to reach its ideal goal,i.e.creating profitable off-theshelf tissues and organs,designing scaffolds and three-dimensional tissue architectures that can maintain the blood supply,proper biomaterial selection,and identifying the most efficient cell source for use in cell therapy and tissue engineering.These are still the major challenges in this field.Regarding the identification of the most appropriate cell source,aging as a factor that affects both somatic and stem cells and limits their function and applications is a preventable and,at least to some extents,a reversible phenomenon.Here,we reviewed different stem cell types,namely embryonic stem cells,adult stem cells,induced pluripotent stem cells,and genetically modified stem cells,as well as their sources,i.e.autologous,allogeneic,and xenogeneic sources.Afterward,we approached aging by discussing the functional decline of aged stem cells and different intrinsic and extrinsic factors that are involved in stem cell aging including replicative senescence and Hayflick limit,autophagy,epigenetic changes,miRNAs,mTOR and AMPK pathways,and the role of mitochondria in stem cell senescence.Finally,various interventions for rejuvenation and geroprotection of stem cells are discussed.These interventions can be applied in cell therapy and tissue engineering methods to conquer aging as a limiting factor,both in original cell source and in the in vitro proliferated cells.

Conduction system disorders and electro-cardiographic findings in COVID-19 deceased patients in 2021,Shiraz,Iran

BACKGROUND Cardiac conduction disorders and electrocardiographic(ECG)changes may occur as a manifestation of coronavirus disease 2019(COVID-19),especially in severe cases.AIM To describe conduction system disorders and their association with other electrocardiographic parameters in patients who died of COVID-19.METHODS In this cross-sectional study,electrocardiographic and clinical data of 432 patients who expired from COVID-19 between August 1st,2021,and December 1st,2021,in a tertiary hospital were reviewed.RESULTS Among 432 patients who died from COVID-19,atrioventricular block(AVB)was found in 40(9.3%).Among these 40 patients,28(6.5%)suffered from 1st degree AVB,and 12(2.8%)suffered from complete heart block(CHB).Changes in ST-T wave,compatible with myocardial infarction or localized myocarditis,appeared in 189(59.0%).Findings compatible with myocardial injury,such as fragmented QRS and prolonged QTc,were found in 91 patients(21.1%)and 28 patients(6.5%),respectively.In patients who died of COVID-19,conduction disorder was unrelated to any underlying medical condition.Fragmented QRS,axis deviation,and ST-T changes were significantly related to conduction system disorder in patients who died of COVID-19(P value<0.05).CONCLUSION Conduction system disorders are associated with several other ECG abnormalities,especially those indicative of myocardial ischemia or inflammation.Most patients(73.14%)who died of COVID-19 demonstrated at least one ECG abnormality parameter.Since a COVID-19 patient's ECG gives important information regarding their cardiac health,our findings can help develop a risk stratification method for at-risk COVID-19 patients in future studies.