Rescue of odontogenesis in Dmp1-deficient mice by targeted re-expression of DMP1 reveals roles for DMP1 in early odontogenesis and dentin apposition in vivo

Dentin matrix protein 1 (DMP1) is expressed in both pulp and odontoblast cells and deletion of the Dmp1 gene leads to defects in odontogenesis and mineralization. The goals of this study were to examine how DMP1 controls dentin mineralization and odontogenesis in vivo. Fluorochrome labeling of dentin in Dmp1-null mice showed a diffuse labeling pattern with a 3-fold reduction in dentin appositional rate compared to controls. Deletion of DMP1 was also associated with abnormalities in the dentinal tubule system and delayed formation of the third molar. Unlike the mineralization defect in Vitamin D receptor-null mice, the mineralization defect in Dmp1-null mice was not rescued by a high calcium and phosphate diet, suggesting a different effect of DMP1 on mineralization. Re-expression of Dmp1 in early and late odontoblasts under control of the Col1a1 promoter rescued the defects in mineralization as well as the defects in the dentinal tubules and third molar development. In contrast, re-expression of Dmp1 in mature odontoblasts, using the Dspp promoter, produced only a partial rescue of the mineralization defects. These data suggest that DMP1 is a key regulator of odontoblast differentiation, formation of the dentin tubular system and mineralization and its expression is required in both early and late odontoblasts for normal odontogenesis to proceed.     

Oligodendrocyte ablation affects the coordinated interaction between granule and Purkinje neurons during cerebellum development

Oligodendrocytes (OLs) are the glial cells of the central nervous system (CNS) classically known to be devoted to the formation of myelin sheaths around most axons of the vertebrate brain. We have addressed the role of these cells during cerebellar development, by ablating OLs in vivo. Previous analyses had indicated that OL ablation during the first six postnatal days results into a striking cerebellar phenotype, whose major features are a strong reduction of granule neurons and aberrant Purkinje cells development. These two cell types are highly interconnected during cerebellar development through the production of molecules that help their proliferation, differentiation and maintenance. In this article, we present data showing that OL ablation has major effects on the physiology of Purkinje (PC) and granule cells (GC). In particular, OL ablation results into a reduction of sonic hedgehog (Shh), Brain Derived Neurotrophic Factor (BDNF), and Reelin (Rln) expression. These results indicate that absence of OLs profoundly alters the normal cerebellar developmental program.     

Osteoactivin fragments produced by ectodomain shedding induce MMP-3 expression via ERK pathway in mouse NIH-3T3 fibroblasts

Intact osteoactivin, a novel type I membrane glycoprotein, were shed at a dibasic motif in the juxtamembrane region in C2C12 myoblasts. Extracellular fragments were secreted into the culture media by a putative metalloprotease. Extracellular fragments of osteoactivin, but not control protein, induced matrix metalloprotease-3 (MMP-3) expression in NIH-3T3 fibroblasts. Epidermal growth factor (ERK) kinase inhibitors inhibited the osteoactivin-mediated MMP-3 expression, whereas the extracellular fragment of osteoactivin activated ERK1/2 and p38 in the mitogen-activated protein kinase pathway. Our results suggest that the extracellular fragments of osteoactivin produced by shedding act as a growth factor to induce MMP-3 expression via the ERK pathway in fibroblasts.     

Pathogenic mitochondrial DNA-induced respiration defects in hematopoietic cells result in anemia by suppressing erythroid differentiation

Anemia is a symptom in patients with Pearson syndrome caused by the accumulation of mutated mitochondrial DNA (mtDNA). Such mutated mtDNAs have been detected in patients with anemia. This suggested that respiration defects due to mutated mtDNA are responsible for the anemia. However, there has been no convincing experimental evidence to confirm the pathophysiological relation between respiration defects in hematopoietic cells and expression of anemia. We address this issue by transplanting bone marrow cells carrying pathogenic mtDNA with a large-scale deletion (ΔmtDNA) into normal mice. The bone marrow-transplanted mice carried high proportion of ΔmtDNA only in hematopoietic cells, and resultant the mice suffered from macrocytic anemia. They show abnormalities of erythroid differentiation and weak erythropoietic response to a stressful condition. These observations suggest that hematopoietic cell-specific respiration defects caused by mtDNAs with pathogenic mutations are responsible for anemia by inducing abnormalities in erythropoiesis.     

Extreme obesity reduces bone mineral density: complementary evidence from mice and women

Objective: To evaluate the effects of body adiposity on bone mineral density in the presence and absence of ovarian hormones in female mice and postmenopausal women. Research Methods and Procedures: We assessed percentage body fat, serum leptin levels, and bone mineral density in ovariectomized and non‐ovariectomized C57BL/6 female mice that had been fed various calorically dense diets to induce body weight profiles ranging from lean to very obese. Additionally, we assessed percentage body fat and whole body bone mineral density in 37 overweight and extremely obese postmenopausal women from the Women's Contraceptive and Reproductive Experiences study. Results: In mice, higher levels of body adiposity (>40% body fat) were associated with lower bone mineral density in ovariectomized C57BL/6 female mice. A similar trend was observed in a small sample of postmenopausal women. Discussion: The complementary studies in mice and women suggest that extreme obesity in postmenopausal women may be associated with reduced bone mineral density. Thus, extreme obesity (BMI > 40 kg/m²) may increase the risk for osteopenia and osteoporosis. Given the obesity epidemic in the U.S. and in many other countries, and, in particular, the rising number of extremely obese adult women, increased attention should be drawn to the significant and interrelated public health issues of obesity and osteoporosis.     

GSK3β/eEF2K信号通路对小鼠肺纤维化过程的影响*

目的: 探讨糖原合成酶激酶-3(GSK3β)/真核延伸因子激酶2(eEF2K)信号通路对肺纤维化进程的影响,为临床治疗肺纤维化寻找新的思路。方法: 采用一次性气管注射法构建C57BL/6雄性小鼠博莱霉素肺纤维化模型,造模14 d后将动物分成模型组、阴性抑制组与抑制组(n=5),另设空白组不作处理。抑制组使用腹腔注射TDZD-8(4 mg/kg),阴性抑制组腹腔注射二甲基亚砜(DMSO)溶液,28 d后处死采集指标。采用苏木精-伊红染色法检测小鼠肺脏病变情况;试剂盒水解法检测肺组织中羟脯氨酸(Hyp)的含量;采用Western blot法检测肺脏中GSK3β、磷酸化GSK3β(p-GSK3β)、eEF2K、p-eEF2K(Ser70)、p-eEF2K(Ser392)、p-eEF2K(Ser470)、基质金属蛋白酶-2前体蛋白(pro-MMP-2)、基质金属蛋白酶-2(MMP-2)蛋白表达水平,使用免疫组织化学法检测肺脏中MMP-2、胶原蛋白I(Col I)、胶原蛋白Ⅲ(Col Ⅲ)、α-平滑肌蛋白(α-SMA)的表达。结果: 与空白组相比,模型组中GSK3β、p-GSK3β、p-eEF2K(Ser70)、p-eEF2K(Ser392)、p-eEF2K(Ser470)、pro-MMP-2、MMP-2、Col I、Col Ⅲ、α-SMA蛋白表达水平升高,eEF2K蛋白表达水平降低(P＜0.05);与模型组相比,抑制组GSK3β、p-GSK3β、p-eEF2K(Ser70)、p-eEF2K(Ser392)、p-eEF2K(Ser470)、pro-MMP-2、MMP-2、Col I、Col Ⅲ、α-SMA蛋白表达降低,eEF2K蛋白表达升高(P＜ 0.05)。结论: GSK3β能通过Ser70、Ser392、Ser470这3个位点磷酸化激活eEF2K,增加纤维化指标含量,促进肺纤维化形成,加重肺组织病变。     

Characteristics of replication and pathogenicity of SARS-CoV-2 Alpha and Delta isolates

The continuously arising of SARS-CoV-2 variants has been posting a great threat to public health safety globally, from B.1.17 (Alpha), B.1.351 (Beta), P.1 (Gamma), B.1.617.2 (Delta) to B.1.1.529 (Omicron). The emerging or reemerging of the SARS-CoV-2 variants of concern is calling for the constant monitoring of their epidemics, pathogenicity and immune escape. In this study, we aimed to characterize replication and pathogenicity of the Alpha and Delta variant strains isolated from patients infected in Laos. The amino acid mutations within the spike fragment of the isolates were determined via sequencing. The more efficient replication of the Alpha and Delta isolates was documented than the prototyped SARS-CoV-2 in Calu-3 and Caco-2 cells, while such features were not observed in Huh-7, Vero E6 and HPA-3 cells. We utilized both animal models of human ACE2 (hACE2) transgenic mice and hamsters to evaluate the pathogenesis of the isolates. The Alpha and Delta can replicate well in multiple organs and cause moderate to severe lung pathology in these animals. In conclusion, the spike protein of the isolated Alpha and Delta variant strains was characterized, and the replication and pathogenicity of the strains in the cells and animal models were also evaluated.