Cell polarization enables restriction of signalling into microdomains. Polarization of lymphocytes following formation of a mature immunological synapse (IS) is essential for calcium-dependent T-cell activation. Here, we analyse calcium microdomains at the IS with total internal reflection fluorescence microscopy. We find that the subplasmalemmal calcium signal following IS formation is sufficiently low to prevent calcium-dependent inactivation of ORAI channels. This is achieved by localizing mitochondria close to ORAI channels. Furthermore, we find that plasma membrane calcium ATPases (PMCAs) are re-distributed into areas beneath mitochondria, which prevented PMCA up-modulation and decreased calcium export locally. This nano-scale distribution-only induced following IS formation-maximizes the efficiency of calcium influx through ORAI channels while it decreases calcium clearance by PMCA, resulting in a more sustained NFAT activity and subsequent activation of T cells.

Polycomb group (PcG) proteins are key epigenetic regulators of hematopietic stem cell (HSC) fate. The PcG members Ezh2 and Ezh1 are important determinants of embryonic stem cell identity, and the transcript levels of these histone methyltransferases are inversely correlated during development. However, the role of Ezh1 in somatic stem cells is largely unknown. Here we show that Ezh1 maintains repopulating HSCs in a slow-cycling, undifferentiated state, protecting them from senescence. Ezh1 ablation induces significant loss of adult HSCs, with concomitant impairment of their self-renewal capacity due to a potent senescence response. Epigenomic and gene expression changes induced by Ezh1 deletion in senesced HSCs demonstrated that Ezh1-mediated PRC2 activity catalyzes monomethylation and dimethylation of H3K27. Deletion of Cdkn2a on the Ezh1 null background rescued HSC proliferation and survival. Our results suggest that Ezh1 is an important histone methyltransferase for HSC maintenance.

Recent results indicate that Ca2+ transport by organella contributes to shaping Ca2+ signals and exocytosis in adrenal chromaffin cells. Therefore, accurate measurements of [Ca2+] inside cytoplasmic organella are essential for a comprehensive analysis of the Ca2+ redistribution that follows cell stimulation. Here we have studied changes in Ca2+ inside the endoplasmic reticulum, mitochondria, and nucleus by imaging aequorins targeted to these compartments in cells stimulated by brief depolarizing pulses with high K+ solutions. We find that Ca2+ entry through voltage-gated Ca2+ channels generates subplasmalemmal high [Ca2+]c domains adequate for triggering exocytosis. A smaller increase of [Ca2+]c is produced in the cell core, which is adequate for recruitment of the reserve pool of secretory vesicles to the plasma membrane. Most of the Ca2+ load is taken up by a mitochondrial pool, M1, closer to the plasma membrane; the increase of [Ca2+]M stimulates respiration in these mitochondria, providing local support for the exocytotic process. Relaxation of the [Ca2+]c transient is due to Ca2+ extrusion through the plasma membrane. At this stage, mitochondria release Ca2+ to the cytosol through the Na+/Ca2+ exchanger, thus maintaining [Ca2+]c discretely increased, especially at core regions of the cell, for periods that outlast the duration of the stimulus.

No abstract

Periodontitis is a chronic inflammatory condition leading to destruction of the tooth supporting tissues, which if left untreated may cause tooth loss. The treatment of periodontitis mainly aims to arrest the inflammatory process by infection control measures, although in some specific lesions a limited periodontal regeneration can also be attained. Current regenerative approaches are aimed to guide the cells with regenerative capacity to repopulate the lesion and promote new cementum and new connective tissue attachment. The first phase in periodontal tissue regeneration involves the differentiation of mesenchymal cells into cementoblasts to promote new cementum, thus facilitating the attachment of new periodontal ligament fibers to the root and the alveolar bone. Current regenerative approaches limit themselves to the confines of the lesion by promoting the self‐regenerative potential of periodontal tissues. With the advent of bioengineered therapies, several studies have investigated the potential use of cell therapies, mainly the use of undifferentiated mesenchymal cells combined with different scaffolds. The understanding of the origin and differentiation patterns of these cells is, therefore, important to elucidate their potential therapeutic use and their comparative efficacy with current technologies. This paper aims to review the in vitro and experimental studies using cell therapies based on application of cementoblasts and mesenchymal stem cells isolated from oral tissues when combined with different scaffolds.

No abstract

Patients with cancer are poorly represented in coronavirus disease 2019 (COVID-19) series, and heterogeneous series concerning hematology patients have been published. This study aimed to analyze the impact of COVID-19 in patients with lymphoma. We present a multicenter retrospective study from 19 centers in Madrid, Spain, evaluating risk factors for mortality in adult patients with COVID-19 and lymphoma. About 177 patients (55.9% male) were included with a median follow-up of 27 days and a median age of 70 years. At the time of COVID-19 diagnosis, 49.7% of patients were on active treatment. The overall mortality rate was 34.5%. Age >70 years, confusion, urea concentration, respiratory rate, blood pressure, and age >65 score ≥2, heart disease, and chronic kidney disease were associated with higher mortality risk ( P < 0.05). Active disease significantly increased the risk of death (hazard ratio, 2.43; 95% confidence interval, 1.23-4.77; P = 0.01). However, active treatment did not modify mortality risk and no differences were found between the different therapeutic regimens. The persistence of severe acute respiratory syndrome coronavirus 2-positive polymerase chain reaction after week 6 was significantly associated with mortality (54.5% versus 1.4%; P < 0.001). We confirm an increased mortality compared with the general population. In view of our results, any interruption or delay in the start of treatment should be questioned given that active treatment has not been demonstrated to increase mortality risk and that achieving disease remission could lead to better outcomes.

Nuñez J, Sanz‐Blasco S, Vignoletti F, Muñoz F, Arzate H, Villalobos C, Nuñez L, Caffesse RG, Sanz M. Periodontal regeneration following implantation of cementum and periodontal ligament‐derived cells. J Periodont Res 2012; 47: 33–44. © 2011 John Wiley & Sons A/SBackground and Objective:  The periodontal regeneration of bone defects is often unsatisfactory and could be largely improved by cell therapy. Therefore, the purpose of this study was to evaluate the regenerative potential of implanting canine cementum‐derived cells (CDCs) and canine periodontal ligament‐derived cells (PDLDCs) in experimentally created periodontal intrabony defects in beagle dogs.Material and Methods:  Cells were obtained from premolars extracted from four beagle dogs. Three‐wall intrabony periodontal defects, 3 mm wide and 4 mm deep, were surgically created in their second and fourth premolars and plaque was allowed to accumulate. Once the defects were surgically debrided, periodontal regeneration was attempted by random implantation of collagen sponges embedded with 750,000 CDCs, 750,000 PDLDCs or culture medium. After 3 mo of healing, specimens were obtained and periodontal regenerative outcomes were assessed histologically and histometrically.Results:  The histological analysis showed that a minimal amount of new cementum was formed in the control group (1.56 ± 0.39 mm), whereas in both test groups, significantly higher amounts of new cementum were formed (3.98 ± 0.59 mm in the CDC group and 4.07 ± 0.97 mm in the PDLDC group). The test groups also demonstrated a larger dimension of new connective tissue, resulting in a significantly more coronal level of histological attachment.Conclusion:  This proof‐of‐principle study suggests that cellular therapy, in combination with a collagen sponge, promoted periodontal regeneration in experimental intrabony periodontal defects.