Bovine mammary stem cells: new perspective for dairy science

An Update on Applications of Cattle Mesenchymal Stromal Cells

Simple Summary

Among livestock species, cattle are crucially important for the meat and milk production industry. Cows can be affected by different pathologies, such as mastitis, endometritis and lameness, which can negatively affect either food production or reproductive efficiency. The use of mesenchymal stromal cells (MSCs) is a valuable tool both in the treatment of various medical conditions and in the application of reproductive biotechnologies. This review provides an update on state-of-the-art applications of bovine MSCs to clinical treatments and reproductive biotechnologies.

Abstract

Attention on mesenchymal stromal cells (MSCs) research has increased in the last decade mainly due to the promising results about their plasticity, self-renewal, differentiation potential, immune modulatory and anti-inflammatory properties that have made stem cell therapy more clinically attractive. Furthermore, MSCs can be easily isolated and expanded to be used for autologous or allogenic therapy following the administration of either freshly isolated or previously cryopreserved cells. The scientific literature on the use of stromal cells in the treatment of several animal health conditions is currently available. Although MSCs are not as widely used for clinical treatments in cows as for companion and sport animals, they have the potential to be employed to improve productivity in the cattle industry. This review provides an update on state-of-the-art applications of bovine MSCs to clinical treatments and reproductive biotechnologies.

Alternatives to animal models and their application in the discovery of species susceptibility to SARS-CoV-2 and other respiratory infectious pathogens: A review

The emergence of the coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) inspired rapid research efforts targeting the host range, pathogenesis and transmission mechanisms, and the development of antiviral strategies. Genetically modified mice, rhesus macaques, ferrets, and Syrian golden hamsters have been frequently used in studies of pathogenesis and efficacy of antiviral compounds and vaccines. However, alternatives to in vivo experiments, such as immortalized cell lines, primary respiratory epithelial cells cultured at an air-liquid interface, stem/progenitor cell-derived organoids, or tissue explants, have also been used for isolation of SARS-CoV-2, investigation of cytopathic effects, and pathogen-host interactions. Moreover, initial proof-of-concept studies for testing therapeutic agents can be performed with these tools, showing that animal-sparing cell culture methods could significantly reduce the need for animal models in the future, following the 3R principles of replace, reduce, and refine. So far, only few studies using animal-derived primary cells or tissues have been conducted in SARS-CoV-2 research, although natural infection has been shown to occur in several animal species. Therefore, the need for in-depth investigations on possible interspecies transmission routes and differences in susceptibility to SARS-CoV-2 is urgent. This review gives an overview of studies employing alternative culture systems like primary cell cultures, tissue explants, or organoids for investigations of the pathophysiology and reverse zoonotic potential of SARS-CoV-2 in animals. In addition, future possibilities of SARS-CoV-2 research in animals, including previously neglected methods like the use of precision-cut lung slices, will be outlined.

Transcription factor E2F4 is a positive regulator of milk biosynthesis and proliferation of bovine mammary epithelial cells

The transcription factor E2F4 is a key determinant of cell differentiation and cell-cycle progression, but its function and regulatory mechanism are not completely understood. Here, we report that E2F4 acts as a positive regulator of the biosynthesis of milk components and proliferation of bovine mammary epithelial cells (BMECs). Overexpression of E2F4 in BMECs resulted in the upregulation of β-casein, triglyceride, and lactose levels and increased cell proliferation, whereas E2F4 knockdown by small interfering RNA had the opposite effects. We further detected that overexpression of E2F4 significantly increased the messenger RNA expression of mTOR, SREBP-1c, and Cyclin D1, and increased protein levels of SREBP-1c, and Cyclin D1, and the ratio of p-mTOR/mTOR, whereas E2F4 knockdown had the opposite effects. E2F4 was almost entirely located in the nucleus, and we further identified, via ChIP-qPCR analysis, that mTOR, SREBP-1c, and Cyclin D1 were E2F4 target genes, and exogenous administration of methionine, leucine, β-estradiol, and prolactin markedly increased the protein levels of E2F4 and its binding to the promoters of these three genes. In summary, our data reveal that E2F4 responds to extracellular stimuli and regulates the expression of mTOR, SREBP-1c, and Cyclin D1 for milk biosynthesis and proliferation of BMECs.

Organoids are promising tools for species-specific in vitro toxicological studies

Organoids are three-dimensional self-aggregating structures generated from stem cells (SCs) or progenitor cells in a process that recapitulates molecular and cellular stages of early organ development. The differentiation process leads to the appearance of specialized mature cells and is connected with changes in the organoid internal structure rearrangement and self-organization. The formation of organ-specific structures in vitro with highly ordered architecture is also strongly influenced by the extracellular matrix. These features make organoids as a powerful model for in vitro toxicology. Nowadays this technology is developing very quickly. In this review we present, from a toxicological and species-specific point of view, the state of the art of organoid generation from adult SCs and pluripotent SCs: embryonic SCs or induced pluripotent SCs. The current culture organoid techniques are discussed for their main advantages, disadvantages and limitations. In the second part of the review, we concentrated on the characterization of species-specific organoids generated from tissue-specific SCs of different sources: mammary (bovine), epidermis (canine), intestinal (porcine, bovine, canine, chicken) and liver (feline, canine).

Cyclase-associated protein 1 is a key negative regulator of milk synthesis and proliferation of bovine mammary epithelial cells

Adenylyl cyclase-associated protein (CAP) is a highly conserved protein. Previous reports have suggested that CAP1 may be a negative regulator of cellular proliferation, migration, and adhesion and the development of cell carcinomas. The molecular mechanism of CAP1 regulation of downstream pathways, as well as how CAP1 is regulated by environmental stimuli and upstream signalling, is not well understood. In this present study, we assessed the role of CAP1 in milk synthesis and proliferation of bovine mammary epithelial cells. Using gene overexpression and silencing methods, CAP1 was found to negatively regulate milk synthesis and proliferation of cells via the PI3K-mTOR/SREBP-1c/Cyclin D1 signalling pathway. Hormones, such as prolactin and oestrogen, and amino acids, such as methionine and leucine, stimulate MMP9 expression and trigger CAP1 degradation, and thus, abrogate its inhibition of synthesis of milk protein, fat, and lactose by and proliferation of bovine mammary epithelial cells. The results of our study help deepen our understanding of the regulatory mechanisms underlying milk synthesis and aid in characterizing the molecular mechanisms of CAP1. Previous reports have suggested that CAP1 is a negative regulator of cellular proliferation and anabolism, but the molecular mechanisms are largely unknown. In this present study, we identified CAP1 as a negative regulator of milk synthesis and proliferation of bovine mammary epithelial cells. Our results will deepen our understanding of the regulatory mechanisms underlying milk synthesis and aid in exploring the molecular mechanisms of CAP1.

Mesenchymal stem cell: Basic research and potential applications in cattle and buffalo

Characteristic features like self-renewal, multilineage differentiation potential, and immune-modulatory/anti-inflammatory properties, besides the ability to mobilize and home distant tissues make stem cells (SCs) a lifeline for an individual. Stem cells (SCs) if could be harvested and expanded without any abnormal change may be utilized as an all-in-one solution to numerous clinical ailments. However, slender understanding of their basic physiological properties, including expression potential, behavioral alternations during culture, and the effect of niche/microenvironment has currently restricted the clinical application of SCs. Among various types of SCs, mesenchymal stem cells (MSCs) are extensively studied due to their easy availability, straightforward harvesting, and culturing procedures, besides, their less likelihood to produce teratogens. Large ruminant MSCs have been harvested from various adult tissues and fetal membranes and are well characterized under in vitro conditions but unlike human or other domestic animals in vivo studies on cattle/buffalo MSCs have mostly been aimed at improving the animals' production potential. In this document, we focused on the status and potential application of MSCs in cattle and buffalo.

Identification and Characterization of a Stem Cell-Like Population in Bovine Milk: A Potential New Source for Regenerative Medicine in Veterinary

Milk is a complex fluid required for development, nutrition and immunological protection to the newborn offspring. Interestingly, latest finding proved the presence of novel stem cell population in human milk with multilineage differentiation potential. Given that little is known about cellular milk content in other mammalian species such as bovine, the purpose of our study was to isolate and characterize a potential stem cell-like population in bovine milk. In detail, we first analyzed the phenotype of the isolated cells able to grow in plastic adherence and then their capability to differentiate into osteogenic, chondrogenic, and adipogenic lineages. Bovine milk stem cells (bMSCs) resulted plastic adherent and showed a heterogeneous population with epithelial and spindle-shaped cells. Successively, their immunophenotype indicated that bovine milk cells were positive for the typical epithelial markers E-cadherin, cytokeratin-14, cytokeratin-18, and smooth muscle actin. Notably, a subset (30%-40%), constantly observed in purified milk cells, showed the typical mesenchymal surface antigens CD90, CD73, and CD105. Furthermore, the same percentage of bMSCs expressing CD90, CD73, and CD105 presented the stemness markers SOX2 and OCT4 translocated in their nuclei. Finally, our data showed that bMSCs were able to differentiate into osteoblasts, chondroblasts, and adipocytes. In addition, the flow cytometry analysis revealed the presence of a subpopulation of events characterized by typical extracellular vesicles (EVs, size 0.1-1 μm), which did not contain nuclei and were positive for the same markers identified on the surface of bMSCs (CD73, CD90, and CD105), and thus might be considered milk cell-derived EVs. In conclusion, our data suggest that bovine milk is an easily available source of multipotent stem cells able to differentiate into multiple cell lineages. These features can open new possibilities for development biology and regenerative medicine in veterinary area to improving animal health.

Consequences of dietary energy source and energy level on energy balance, lactogenic hormones, and lactation curve characteristics of cows after a short or omitted dry period

Omitting the dry period (DP) generally reduces milk production in the subsequent lactation. The aim of this study was to evaluate the effect of dietary energy source-glucogenic (G) or lipogenic (L)-and energy level-standard (std) or low-on milk production; energy balance (EB); lactogenic hormones insulin, insulin-like growth factor 1 (IGF-1), and growth hormone (GH); and lactation curve characteristics between wk 1 and 44 postpartum in cows after a 0-d or 30-d DP. Cows (n = 110) were assigned randomly to 3 transition treatments: a 30-d DP with a standard energy level required for expected milk yield [30-d DP(std)], a 0-d DP with the same energy level as cows with a 30-d DP [0-d DP(std)], and a 0-d DP with a low energy level [0-d DP(low)]. In wk 1 to 7, cows were fed the same basal ration but the level of concentrate increased to 6.7 kg/d for cows fed the low energy level and to 8.5 kg/d for cows fed the standard energy level in wk 4. From wk 8 postpartum onward, cows received a G ration (mainly consisting of corn silage and grass silage) or an L ration (mainly consisting of grass silage and sugar beet pulp) with the same energy level contrast (low or std) as in early lactation. Cows fed the G ration had greater milk, lactose, and protein yields, lower milk fat percentage, greater dry matter and energy intakes, and greater plasma IGF-1 concentration compared with cows fed the L ration. Dietary energy source did not affect EB or lactation curve characteristics. In cows with a 0-d DP, the reduced energy level decreased energy intake, EB, and weekly body weight gain, but did not affect milk production or lactation curve characteristics. A 30-d DP resulted in a greater total predicted lactation yield, initial milk yield after calving, peak milk yield, energy intake, energy output in milk, days to conception [only when compared with 0-d DP(low)], plasma GH concentration [only when compared with 0-d DP(std)], and decreased weekly body weight gain compared with a 0-d DP. A 30-d DP decreased both the increasing and the declining slope parameters of the lactation curve and the relative rate of decline in milk yield (indicating greater lactation persistency) compared with a 0-d DP, and decreased plasma insulin and IGF-1 concentration, and EB. In conclusion, feeding a G ration after wk 7 in milk improved energy intake and milk production, but did not affect EB compared with an L ration. For cows without a DP, a reduced dietary energy level did not affect milk production and lactation curve characteristics, but did decrease EB and weekly body weight gain. A 30-d DP increased milk yield and lactation persistency, but decreased milk fat and protein content, EB, and plasma insulin and IGF-1, compared with a 0-d DP.

At the dawn of a new discovery: the potential of breast milk stem cells

Breast milk contains bioactive molecules that provide a multitude of immunologic, developmental and nutritional benefits to the infant. Less attention has been placed on the cellular nature of breast milk, which contains thousands to millions of maternal cells in every milliliter that the infant ingests. What are the properties and roles of these cells? Most studies have examined breast milk cells from an immunologic perspective, focusing specifically on the leukocytes, mainly in the early postpartum period. In the past decade, research has taken a multidimensional approach to investigating the cells of human milk. Technologic advances in single cell analysis and imaging have aided this work, which has resulted in the breakthrough discovery of stem cells in breast milk with multilineage potential that are transferred to the offspring during breastfeeding. This has generated numerous implications for both infant and maternal health and regenerative medicine. This review summarizes the latest knowledge on breast milk stem cells, and discusses their known in vitro and in vivo attributes as well as potential functions and applications.