CRL2^(APPBP2)-mediated TSPYL2 degradation counteracts human mesenchymal stem cell senescence

Cullin-RING E3 ubiquitin ligases(CRLs),the largest family of multi-subunit E3 ubiquitin ligases in eukaryotic cells,represent core cellular machinery for executing protein degradation and maintaining proteostasis.Here,we asked what roles Cullin proteins play in human mesenchymal stem cell(hMSC)homeostasis and senescence.To this end,we conducted a comparative aging phenotype analysis by individually knocking down Cullin members in three senescence models:replicative senescent hMSCs,Hutchinson-Gilford Progeria Syndrome hMSCs,and Werner syndrome hMSCs.Among all family members,we found that CUL2 deficiency rendered hMSCs the most susceptible to senescence.To investigate CUL2-specific underlying mechanisms,we then applied CRISPR/Cas9-mediated gene editing technology to generate CUL2-deficient human embryonic stem cells(hESCs).When we differentiated these into h MSCs,we found that CUL2 deletion markedly accelerates hMSC senescence.Importantly,we identified that CUL2 targets and promotes ubiquitin proteasome-mediated degradation of TSPYL2(a known negative regulator of proliferation)through the substrate receptor protein APPBP2,which in turn downregulates one of the canonical aging marker-P21^(waf1/cip1),and thereby delays senescence.Our work provides important insights into how CRL2^(APPBP2)-mediated TSPYL2 degradation counteracts hMSC senescence,providing a molecular basis for directing intervention strategies against aging and aging-related diseases.

Human ESC-derived vascular cells promote vascular regeneration in a HIF-1α dependent manner

Hypoxia-inducible factor(HIF-1α),a core transcription factor responding to changes in cellular oxygen levels,is closely associated with a wide range of physiological and pathological conditions.However,its differential impacts on vascular cell types and molecular programs modulating human vascular homeostasis and regeneration remain largely elusive.Here,we applied CRISPR/Cas9-mediated gene editing of human embryonic stem cells and directed differentiation to generate HIF-ia-deficient human vascular cells including vascular endothelial cells,vascular smooth muscle cells,and mesenchymal stem cells(MsCs),as a platform for discovering cell type-specific hypox-ia-induced response mechanisms.Through comparative molecular profiling across cell types under normoxic and hypoxic conditions,we provide insight into the indispensable role of HIF-1αin the promotion of ischemic vascular regeneration.We found human MSCs to be the vascular cell type most susceptible to HIF-1a deficiency,and that transcriptional inactivation of ANKZF1,an effector of HIF-1a,impaired pro-angiogenic processes.Altogether,our findings deepen the understanding of HIF-ia in human angiogenesis and support further explorations of novel therapeutic strategies of vascular regeneration against ischemic damage.

A single-nucleus transcriptomic atlas of primate testicular aging reveals exhaustion of the spermatogonial stem cell reservoir and loss of Sertoli cell homeostasis

The testis is pivotal for male reproduction,and its progressive functional decline in aging is associated with infertility.However,the regulatory mechanism underlying primate testicular aging remains largely elusive.Here,we resolve the aging-related cellular and molecular alterations of primate testicular aging by establishing a single-nucleus transcriptomic atlas.Gene-expression patterns along the spermatogenesis trajectory revealed molecular programs associated with attrition of spermatogonial stem cell reservoir,disturbed meiosis and impaired spermiogenesis along the sequential continuum.Remarkably,Sertoli cell was identified as the cell type most susceptible to aging,given its deeply perturbed age-associated transcriptional profiles.Concomitantly,downregulation of the transcription factor Wilms'Tumor 1(WTi),essential for Sertoli cell homeostasis,was associated with accelerated cellular senescence,disrupted tight junctions,and a compromised cell identity signature,which altogether may help create a hostile microenvironment for spermatogenesis.Collectively,our study depicts in-depth transcriptomic traits of non-human primate(NHP)testicular aging at single-cell resolution,providing potential diagnostic biomarkers and targets for therapeutic interventions against testicular aging and age-related male reproductive diseases.

Differential stem cell aging kinetics in Hutchinson-Gilford progeria syndrome and Werner syndrome

progeria syndrome （HGPS） and Wemer syndrome （WS） are two of the best characterized human progeroid syndromes. HGPS is caused by a point mutation in lamin A （LMNA） gene, resulting in the production of a truncated protein product-progerin. WS is caused by mutations in 14/RN gem）, encoding a loss-of-function RecQ DNA helicase. Here, by gene editing we created isogenic human embryonic stem cells （ESCs） with heterozygous （G608G/＋） or homozygous （G608G/G608G） LMNA mutation and biallelic WRN knockout, for modeling HGPS and WS pathogenesis, respectively. While ESCs and endothelial cells （ECs） did not present any features of premature senescence, HGPS- and WS-mesenchymal stem cells （MSCs） showed aging-associated phenotypes with different kinetics. WS-MSCs had early-onset mild premature aging phenotypes while HGPS-MSCs exhibited iate-onset acute premature aging characterisitcs. Taken together, our study compares and contrasts the distinct pathologies underpinning the two premature aging disorders, and provides reliable stem-cell based models to identify new therapeutic strategies for pathological and physiological aging.

FOXO3-engineered human mesenchymal progenitor cells efficiently promote cardiac repair after myocardial infarction

Dear Editor,Myocardial infarction(MI)is the irreversible cardiomyocyte death resulting from prolonged oxygen deprivation due to obstructed blood supply(ischemia),leading to contractile dysfunction and cardiac remodeling.In recent decades,stem cell transplantation has been extensively investigated for the repair of injured heart in animal studies and clinical trials(Kanelidis et al.,2017;Gyongyosi et al.,2018).

Exosomes from antler stem cells alleviate mesenchymal stem cell senescence and osteoarthritis

Dear Editor,Stem cell therapy holds enormous and revolutionary promise to treat various age-related diseases,such as diabetes,heart failure,and Parkinson’s disease.However,low retention and survival rate of delivered stem cells,partially due to immunological rejection,constitute major hurdles for the clinical implementation of stem cell therapy(Lei et al.,2021a).Since mounting evidence showed that several types of stem cells mainly exert their therapeutic effects through the secretion of paracrine effects,exosomes,which are released by stem cells and execute most paracrine functions,have begun to draw attention in the field(Tran and Damaser,2015).Exosomes are membrane-enclosed vesicles with an average diameter of∼100 nanometers secreted by the cells,containing cytokines.