2020 Vol. 41, No. 5

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2020, 41(5): 1-1.
Breast cancer is the most common malignancy in women. Basic and translational breast cancer research relies heavily on experimental animal models. Ideally, such models for breast cancer should have commonality with human breast cancer in terms of tumor etiology, biological behavior, pathology, and response to therapeutics. This review introduces current progress in different breast cancer experimental animal models and analyzes their characteristics, advantages, disadvantages, and potential applications. Finally, we propose future research directions for breast cancer animal models.
As a transparent avascular tissue located at the front of the eyeball, the cornea is an important barrier to external damage. Both epithelial and endothelial cells of the cornea harbor primary cilia, which sense changes in the external environment and regulate intracellular signaling pathways. Accumulating evidence suggests that the primary cilium regulates corneal development in several ways, including participation in corneal epithelial stratification and maintenance of corneal endothelial cell morphology. In addition, the primary cilium has been implicated in the pathogenesis of several corneal diseases. In this review, we discuss recent findings that demonstrate the critical role of the primary cilium in corneal development. We also discuss the link between ciliary dysfunction and corneal diseases, which suggests that the primary cilium could be targeted to treat these diseases.
As of June 2020, Coronavirus Disease 2019 (COVID-19) has killed an estimated 440 000 people worldwide, 74% of whom were aged ≥65 years, making age the most significant risk factor for death caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. To examine the effect of age on death, we established a SARS-CoV-2 infection model in Chinese rhesus macaques (Macaca mulatta) of varied ages. Results indicated that infected young macaques manifested impaired respiratory function, active viral replication, severe lung damage, and infiltration of CD11b+ and CD8+ cells in lungs at one-week post infection (wpi), but also recovered rapidly at 2 wpi. In contrast, aged macaques demonstrated delayed immune responses with a more severe cytokine storm, increased infiltration of CD11b+ cells, and persistent infiltration of CD8+ cells in the lungs at 2 wpi. In addition, peripheral blood T cells from aged macaques showed greater inflammation and chemotaxis, but weaker antiviral functions than that in cells from young macaques. Thus, the delayed but more severe cytokine storm and higher immune cell infiltration may explain the poorer prognosis of older aged patients suffering SARS-CoV-2 infection.
The coronavirus disease 2019 (COVID-19) pandemic continues to pose a global threat to the human population. Identifying animal species susceptible to infection with the SARS-CoV-2/ HCoV-19 pathogen is essential for controlling the outbreak and for testing valid prophylactics or therapeutics based on animal model studies. Here, different aged Chinese tree shrews (adult group, 1 year old; old group, 5–6 years old), which are close relatives to primates, were infected with SARS-CoV-2. X-ray, viral shedding, laboratory, and histological analyses were performed on different days post-inoculation (dpi). Results showed that Chinese tree shrews could be infected by SARS-CoV-2. Lung infiltrates were visible in X-ray radiographs in most infected animals. Viral RNA was consistently detected in lung tissues from infected animals at 3, 5, and 7 dpi, along with alterations in related parameters from routine blood tests and serum biochemistry, including increased levels of aspartate aminotransferase (AST) and blood urea nitrogen (BUN). Histological analysis of lung tissues from animals at 3 dpi (adult group) and 7 dpi (old group) showed thickened alveolar septa and interstitial hemorrhage. Several differences were found between the two different aged groups in regard to viral shedding peak. Our results indicate that Chinese tree shrews have the potential to be used as animal models for SARS-CoV-2 infection.
Sperm are specialized cells that require adenosine triphosphate (ATP) to support their function. Maintaining sperm energy homeostasis in vitro is vitally important to improve the efficacy of boar sperm preservation. Metformin can activate 5′-AMP-activated protein kinase (AMPK) to improve metabolic flexibility and maintain energy homeostasis. Thus, the aim of the present study was to investigate whether metformin can improve boar sperm quality through AMPK mediation of energy metabolism. Sperm motility parameters, membrane integrity, acrosome integrity, mitochondrial membrane potential (ΔΨm), ATP content, glucose uptake, and lactate efflux were analyzed. Localization and expression levels of AMPK and phospho-Thr172-AMPK (p-AMPK) were also detected by immunofluorescence and western blotting. We found that metformin treatment significantly increased sperm motility parameters, ΔΨm, and ATP content during storage at 17 °C. Moreover, results showed that AMPK was localized at the acrosomal region, connecting piece, and midpiece of sperm and p-AMPK was distributed at the post-acrosomal region, connecting piece, and midpiece. When sperm were incubated with metformin for 4 h at 37 °C, sperm motility parameters, ΔΨm, ATP content, p-AMPK, glucose uptake, and lactate efflux all significantly increased, whereas the addition of Compound C treatment, an inhibitor of AMPK, counteracted these positive effects. Together, our results suggest that metformin promotes AMPK activation, which contributes to the maintenance of energy hemostasis and mitochondrial activity, thereby maintaining boar sperm functionality and improving the efficacy of semen preservation.
Metabolic dysfunction-associated fatty liver disease (MAFLD) is characterized by deregulated hepatic lipid metabolism; however, the association between MAFLD development and mitochondrial dysfunction has yet to be confirmed. Herein, we employed high-resolution respirometry, blue native polyacrylamide gel electrophoresis-based in-gel activity measurement and immunoblot analysis to assess mitochondrial function in obesity-induced mouse models with varying degrees of MAFLD. Results showed a slight but significant decrease in hepatic mitochondrial respiration in some MAFLD mice compared to mice fed a standard diet. However, the activities and levels of mitochondrial oxidative phosphorylation complexes remained unchanged during obesity-induced MAFLD progression. These results suggest that mitochondrial function, particularly oxidative phosphorylation, was mildly affected during obesity-induced MAFLD development. Moreover, transcriptome profiling of mouse and human liver tissues with varying degrees of MAFLD revealed that the decreased activation of mitochondria-related pathways was only associated with MAFLD of a high histological grade, whereas the major regulators of mitochondrial biogenesis were not altered in mice or humans during MAFLD development. Collectively, our results suggest that impaired hepatic mitochondrial function is not closely associated with obesity-induced MAFLD. Therefore, therapeutic strategies targeting mitochondria for the treatment of MAFLD should be reconsidered.
Letters to the editor
With a population of around 4 000 individuals, the Kalash people have been living in the Hindu-Kush mountain valleys of present-day northern Pakistan for centuries. Due to their mysterious origin and fairer European complexion, the genetic history of this ethnic group has been investigated previously using different markers. To date, however, the maternal genetic architecture has not been systematically dissected based on high-resolution complete mitochondrial genomes (mitogenomes), making their maternal genetic history, especially their genetic connection with Europeans from a matrilineal perspective, unclear. To unravel this issue, we analyzed mitogenome data of 34 Kalash samples together with 6 075 individuals from across Eurasia. Our results indicated exclusive western Eurasian origin of the Kalash people, represented by eight haplogroups. Among these haplogroups, J2b1a7a and R0a5a (accounting for ~50% of the Kalash gene pool) displayed in situ differentiations in the Kalash and could be traced to the Mediterranean region. Age estimations suggested these haplogroups arose in the Kalash population ~2.26 and 3.01 thousand years ago (kya), a time frame consistent with the invasion of Alexander III of Macedon to the region. One possible explanation for the maternal genetic contribution from Europeans to the Kalash people would be the involvement of women in foreign campaigns of ancient Greek warfare, followed by a founder effect. Our study thus sheds important light on the genetic origin of the Kalash community of Pakistan.
Changes in gene expression occur as animals, including primates, age. Macaques have long been used as a model species for primate evolution and biomedical studies. Here, to study gene expression in Tibetan macaques (Macaca thibetana, TMs) and its differences to humans, we applied RNA-Seq to obtain the blood transcriptomes of 24 TMs. In total, 2 523 age-associated differentially expressed genes (DEGs) were identified. Several pathways and processes that regulate aging, including the FoxO signaling pathway, autophagy, and platelet activation, were significantly enriched in the up-regulated DEGs. Two significantly age-related modules were identified by weighted gene co-expression network analysis (WGCNA). The TMs and humans shared 279 common DEGs, including 111 up-regulated and 141 down-regulated genes with advancing age in the same expression direction. However, 27 age-related DEGs presented the opposite expression direction in TMs as that in humans. For example, INPPL1, with inhibitory effects on the B cell receptor signaling pathway, was up-regulated in humans but down-regulated in TMs. In general, our study suggests that aging is a critical factor affecting gene expression in the captive TM population. The similarities and differences in gene expression patterns between TMs and humans could provide new insights into primate evolution and benefit TM model development.
Osteonecrosis is a common human disease in orthopedics. It is difficult to treat, and half of patients may need artificial joint replacement, resulting in a considerable economic burden and a reduction in quality of life. Hormones are one of the major causes of osteonecrosis and high doses of corticosteroids are considered the most dangerous factor. Because of the complexity of treatment, we still need a better animal model that can be widely used in drug development and testing. Tree shrews are more closely related to primates than rodents. As such, we constructed a successful tree shrew model to establish and evaluate steroid-associated osteonecrosis (SAON). We found that low-dose lipopolysaccharide (LPS) combined with high-dose methylprednisolone (MPS) over 12 weeks could be used to establish a tree shrew model with femoral head necrosis. Serum biochemical and histological analyses showed that an ideal model was obtained. Thus, this work provides a useful animal model for the study of SAON and for the optimization of treatment methods.
The rise of the plasmid-encoded colistin resistance gene mcr-1 is a major concern globally. Here, during a routine surveillance, an unexpectedly high prevalence of Escherichia coli with reduced susceptibility to colistin (69.9%) was observed in a Chinese broiler farm. Fifty-three (63.9%) E. coli isolates were positive for mcr-1. All identified mcr-1-positive E. coli (MCREC) were multidrug resistant and carried other clinically significant resistance genes. Furthermore, the mcr-1 genes were mainly located on the IncI2 and IncHI2 plasmids. Conjugation experiments unraveled the co-transfer of mcr-1 with other antibiotic resistance genes (blaCTX-M-55, blaCTX-M-14, floR, and fosA3) via the IncI2 (n=3) and IncHI2 (n=4) plasmids. The stable genetic context mcr-1-pap2 was common in the IncI2 plasmids, whereas ISApl1-mcr-1-pap2-ISApl1 was mainly found in the IncHI2 plasmids. The dominance of mcr-1-bearing IncI2 and IncHI2 plasmids and co-selection of mcr-1 with other antimicrobial resistance genes might contribute to the exceptionally high prevalence of mcr-1 in this broiler farm. Our results emphasized the importance of appropriate antibiotic use in animal production.
Theloderma pyaukkya is recorded for the first time in China based on a specimen collected from western Yunnan. Morphologically, the specimen shows good agreement with the original description of T. pyaukkya, and phylogenetically is clustered with the type specimens and holotype of T. pyaukkya from Kachin State (northern Myanmar) with strong support. The taxonomic status of T. pyaukkya from Chin State (western Myanmar) needs further examination. In addition, Theloderma moloch is also recorded in Yunnan for the first time. This brings the number of Theloderma species recorded in Yunnan, China, to seven, namely, T. albopunctatum, T. baibungense, T. bicolor, T. gordoni, T. moloch, T. pyaukkya, and T. rhododiscus.
We report on a new species, Micryletta dissimulans sp. nov. , from the lowland forests of southern Thailand, which is described based on molecular and morphological evidence. The new species is characterized by a combination of the following characters: small body size (20.3–22.4 mm in males, 24.4–26.7 mm in females); slender body habitus; head longer than wide; snout rounded in dorsal and lateral view; eye length equal to snout length; tibiotarsal articulation reaching to tympanum; dorsal surface slightly granulated to shagreened; supratympanic fold indistinct, ventrally edged in black with large black spot behind eye; outer metatarsal tubercle absent; dorsum reddish-brown with merging irregular-shaped brown blotches edged in beige, no black spots on dorsum; body flanks brown with large black spots edged in whitish mottling, two large black blotches in axillary and inguinal areas on each side; lateral sides of head black, with white patches on lips absent, whitish mottling on tympanum and axillary region; ventral surface pinkish to bluish-gray, translucent, laterally with dark-brown marbled pattern, medially immaculate; throat in males dark-gray with sparse white mottling laterally; iris copper-orange. The new species is divergent from all other congeners in 16S rRNA gene sequences (5.0%–7.4%). To date, Micryletta dissimulans sp. nov. is only known from a single locality in Saba Yoi District, Songkhla Province, Thailand, at an elevation of 120 m a.s.l., but is also expected to occur in neighboring parts of Malaysia. We suggest Micryletta dissimulans sp. nov. be considered as a Data Deficient (DD) species following the IUCN’s Red List categories (IUCN Standards and Petitions Committee, 2019).
A new stream salamander species, Batrachuperus daochengensis sp. nov. , from southwestern China, is described herein based on morphological and molecular evidence. Molecular phylogeny derived from the mitochondrial gene together with previous nuclear data revealed that B. daochengensis sp. nov. is sister to B. yenyuanensis. The new species differs from all other species of the genus by the following combination of characters: brown horny epidermis on tips of fingers and toes absent; tubercles on palms and soles absent; costal grooves 12; dorsal brown, mottled with blackish spots; fingers 2-3-4-1 in order of decreasing length; tips of longest digits of fore- and hindlimbs largely separated by one to two costal spaces when adpressed towards each other along sides of body. The new species is currently known in the central and southern Shaluli Mountains in southwestern China.
Cryptic diversity (CD), the presence of highly divergent phylogenetic lineages within closed morphological species, has been documented for many taxa. Great arachnid orders such as Araneae or Scorpiones are well studied and many cases of CD have been described therein; to date, however, related research on smaller arachnid orders, such as whip spiders (Amblypygi), remains lacking. In the current study, we investigated CD based on cytochrome oxidase 1 (COI) in three nominal species of the genus Heterophrynus (H. alces, H. batesii, and H. longicornis), represented by 65 specimens. The sequences were compared using three different methods. All three species showed geographically structured CD. Thus, given its existence in this genus, it is important that CD and its spatial distribution be considered in future studies and possible conservation projects.