Synapses between engram cells are believed to be substrates for memory storage, and the weakening or loss of these synapses leads to the forgetting of related memories. We found engulfment of synaptic components by microglia in the hippocampi of healthy adult mice. Depletion of microglia or inhibition of microglial phagocytosis prevented forgetting and the dissociation of engram cells. By introducing CD55 to inhibit complement pathways, specifically in engram cells, we further demonstrated that microglia regulated forgetting in a complement- and activity-dependent manner. Additionally, microglia were involved in both neurogenesis-related and neurogenesis-unrelated memory degradation. Together, our findings revealed complement-dependent synapse elimination by microglia as a mechanism underlying the forgetting of remote memories.

Under natural conditions, injured cells can be repaired rapidly through inherent biological processes. However, in the case of diabetes, cardiovascular disease, muscular dystrophy, and other degenerative conditions, the natural repair process is impaired. Repair of injury to the cell membrane is an important aspect of physiology. Inadequate membrane repair function is implicated in the pathophysiology of many human disorders. Recent studies show that Mitsugumin 53 (MG53), a TRIM family protein, plays a key role in repairing cell membrane damage and facilitating tissue regeneration. Clarifying the role of MG53 and its molecular mechanism are important for the application of MG53 in regenerative medicine. In this review, we analyze current research dissecting MG53′s function in cell membrane repair and tissue regeneration, and highlight the development of recombinant human MG53 protein as a potential therapeutic agent to repair multiple-organ injuries.

The neovascularization of ischemic tissue is a crucial initial step for the functional rehabilitation and wound healing. However, the short of seed cell candidate for the foundation of vascular network is still a big issue. Human adipose tissue derived mesenchymal stem cells (hADSCs), which possess multilineage potential, are capable of adipogenic, osteogenic, and chondrogenic differentiation. We examined whether this kind of stem cells could differentiate into endothelial-like cells and participate in blood vessel formation, and whether they could be used as an ideal cell source for therapeutic angiogenesis in ischemic diseases or vascularization of tissue constructs. The results showed that hADSCs, grown under appropriately induced conditions, displayed characteristics similar to those of vessel endothelium. The differentiated cells expressed endothelial cell markers CD34 and vWF, and had high metabolism of acetylated low-density lipoprotein and prostacyclin. In addition, the induced cells were able to form tube-like structures when cultured on matrigel. Our data indicated that induced hADSCs could exhibit characteristics of endothelial cells. Therefore, these cells, as a source of human endothelial cells, may find many applications in such realms as engineering blood vessels, endothelial cell transplantation for myocardial regeneration, and induction of angiogenesis for treatment of regional ischemia.

The functional realization is the most important problem in vascular tissue engineering. The small-caliber blood vessel substitutes are prone to thrombi, which results in functional loss of blood vessels. However, this is probably due to the imperfection of endothelial layer in the substitutes. In this study, MSCs were seeded on a series of porous PLGA films with various porosity and pore size made by sodium chloride (NaCl) particulate leaching, and cell proliferation on each film was inspected. The film made of the 75% (w/w) particulate proportion and 30-50 μm pore size maximized the proliferation rate and was chosen as the scaffolds for the differentiation of MSCs into endothelial cells. The induced cells expressed endothelial cells specific Flk-1, Ⅷ factor and CD34, possessed endothelial cells specific Weible-palade (W-P) body, and had the abilities of ingesting low density lipoprotein and secreting prostacyclin (PGI 2 ). The results show that MSCs not only have the ideal biological compatibility with the porous PLGA films, but also have the potency of differentiating into functional endothelial cells, which should facilitate the endothelialization in vascular tissue engineering.

Background: In the past 30 years, incidences of non-alcoholic fatty liver disease (NAFLD) has risen by 30%. However, there is still no clear mechanism or accurate method of anticipating liver failure. Here we reveal the phase transitions of liquid crystalline qualities in hepatic lipid droplets (HLDs) as a novel method of anticipating prognosis. Methods: NAFLD was induced by feeding C57BL/6J mice on a high-fat (HiF) diet. These NAFLD livers were then evaluated under polarized microscopy, X-ray diffraction and small-angle scattering, lipid component chromatography analysis and protein expression analysis. Optically active HLDs from mouse model and patient samples were both then confirmed to have liquid crystal characteristics. Liver MAP1LC3A expression was then evaluated to determine the role of autophagy in liquid crystal HLD (LC-HLD) formation. Results: Unlike the normal diet cohort, HiF diet mice developed NAFLD livers containing HLDs exhibiting Maltese cross birefringence, phase transition, and fluidity signature to liquid crystals. These LC-HLDs transitioned to anisotropic crystal at 0 °C and remain crystalline. Temperature increase to 42 °C causes both liquid crystal and crystal HLDs to convert to isotropic droplet form. These isotropic HLDs successfully transition to anisotropic LC with fast temperature decrease and anisotropic crystal with slow temperature decrease. These findings were duplicated in patient liver. Patient LC-HLDs with no inner optical activity were discovered, hinting at lipid saturation as the mechanism through which HLD acquire LC characteristics. Downregulation of MAP1LC3A in conjunction with increased LC-HLD also implicated autophagy in NAFLD LC-HLD formation. Conclusions: Increasing concentrations of amphiphilic lipids in HLDs favors organization into alternating hydrophilic and hydrophobic layers, which present as LC-HLDs. Thus, evaluating the extent of liquid crystallization with phase transition in HLDs of NAFLD patients may reveal disease severity and predict impending liver damage.