Enhanced protein-metabolite correlation analysis: To investigate the association between Staphylococcus aureus mastitis and metabolic immune pathways.

Mastitis is a disease characterized by congestion, swelling, and inflammation of the mammary gland and usually caused by infection with pathogenic microorganisms. Furthermore, the development of mastitis is closely linked to the exogenous pathway of the gastrointestinal tract. However, the regulatory mechanisms governing the gut-metabolism-mammary axis remain incompletely understood. The present study revealed alterations in the gut microbiota of mastitis rats characterized by an increased abundance of the Proteobacteria phylum. Plasma analysis revealed significantly higher levels of L-isoleucine and cholic acid along with 7-ketodeoxycholic acid. Mammary tissue showed elevated levels of arachidonic acid metabolites and norlithocholic acid. Proteomic analysis showed increased levels of IFIH1, Tnfaip8l2, IRGM, and IRF5 in mastitis rats, which suggests that mastitis triggers an inflammatory response and immune stress. Follistatin (Fst) and progesterone receptor (Pgr) were significantly downregulated, raising the risk of breast cancer. Extracellular matrix (ECM) receptors and focal adhesion signaling pathways were downregulated, while blood-milk barrier integrity was disrupted. Analysis of protein-metabolic network regulation revealed that necroptosis, protein digestion and absorption, and arachidonic acid metabolism were the principal regulatory pathways involved in the development of mastitis. In short, the onset of mastitis leads to changes in the microbiota and alterations in the metabolic profiles of various biological samples, including colonic contents, plasma, and mammary tissue. Key manifestations include disturbances in bile acid metabolism, amino acid metabolism, and arachidonic acid metabolism. At the same time, the integrity of the blood-milk barrier is compromised while inflammation is promoted, thereby reducing cell adhesion in the mammary glands. These findings contribute to a more comprehensive understanding of the metabolic status of mastitis and provide new insights into its impact on the immune system.

Aryl hydrocarbon receptor activation by Lactobacillus reuteri tryptophan metabolism alleviates Escherichia coli-induced mastitis in mice.

The intestinal microbiota has been associated with the occurrence and development of mastitis, which is one of the most serious diseases of lactating women and female animals, but the underlying mechanism has not yet been elucidated. Aryl hydrocarbon receptor (AhR) activation by microbiota tryptophan metabolism-derived ligands is involved in maintaining host homeostasis and resisting diseases. We investigated whether AhR activation by microbiota-metabolic ligands could influence mastitis development in mice. In this study, we found that AhR activation using Ficz ameliorated mastitis symptoms, which were related to limiting NF-κB activation and enhancing barrier function. Impaired AhR activation by disturbing the intestinal microbiota initiated mastitis, and processed Escherichia coli (E. coli)-induced mastitis in mice. Supplementation with dietary tryptophan attenuated the mastitis, but attenuation was inhibited by the intestinal microbiota abrogation, while administering tryptophan metabolites including IAld and indole but not IPA, rescued the tryptophan effects in dysbiotic mice. Supplementation with a Lactobacillus reuteri (L. reuteri) strain with the capacity to produce AhR ligands also improved E. coli-induced mastitis in an AhR-dependent manner. These findings provide evidence for novel therapeutic strategies for treating mastitis, and support the role of metabolites derived from the intestinal microbiota in improving distal disease.

Retinoic acid ameliorates low-grade endotoxemia-induced mastitis by limiting inflammatory responses in mice.

Mastitis is a serious disease for humans and animals, which causes huge economic losses in the dairy industry and is hard to prevent due to the complex and unclear pathogenesis. Subacute ruminal acidosis (SARA) has contributed to the development of mastitis by inducing ruminal dysbiosis and subsequent low-grade endotoxemia (LGE), however, how ruminal metabolic changes regulate this progress is still unclear. Our previous study revealed that cows with SARA had increased ruminal retinoic acid (RA) levels, a metabolic intermediate of vitamin A that plays an essential role in mucosal immune responses. Hence, the aim of this study was to investigate the protective effect of RA on LGE-induced mastitis and the underlying mechanisms in mice. The results showed that RA alleviated LGE-induced mastitis, as evidenced by RA significantly reduced the increase in mammary proinflammatory cytokines and improved blood-milk barrier injury caused by LGE. In addition, RA increased the expression of tight junction proteins, including ZO-1, occludin and claudin-3. Furthermore, we found that RA limited the mammary inflammatory responses by inhibiting the activation of NF-κB and NLRP3 signaling pathways. These findings suggest that RA effectively alleviates LGE-induced mastitis and implies a potential strategy for the treatment and prevention of mastitis and other diseases.

Unilateral lupus mastitis.

Lupus mastitis is a rare clinical manifestation associated with systemic lupus erythematosus or discoid lupus erythematosus. It is necessary to make a correct diagnosis to differentiate it from inflammatory breast cancer. The histological study shows involvement of the adipose tissue of the breast with histopathological findings of cutaneous lupus erythematosus. Direct immunofluorescence detects the lupus band at the dermal-epidermal junction. The treatment of choice is hydroxychloroquine. We present a case of unilateral lupus mastitis in a patient with no previous diagnosis of lupus with complete remission after the use of hydroxychloroquine and topical corticosteroids.

LC/MS-based untargeted lipidomics reveals lipid signatures of nonpuerperal mastitis.

BACKGROUND: Nonpuerperal mastitis (NPM) is a disease that presents with redness, swelling, heat, and pain during nonlactation and can often be confused with breast cancer. The etiology of NPM remains elusive; however, emerging clinical evidence suggests a potential involvement of lipid metabolism. METHOD: Liquid chromatography‒mass spectrometry (LC/MS)-based untargeted lipidomics analysis combined with multivariate statistics was performed to investigate the NPM lipid change in breast tissue. Twenty patients with NPM and 10 controls were enrolled in this study. RESULTS: The results revealed significant differences in lipidomics profiles, and a total of 16 subclasses with 14,012 different lipids were identified in positive and negative ion modes. Among these lipids, triglycerides (TGs), phosphatidylethanolamines (PEs) and cardiolipins (CLs) were the top three lipid components between the NPM and control groups. Subsequently, a total of 35 lipids were subjected to screening as potential biomarkers, and the chosen lipid biomarkers exhibited enhanced discriminatory capability between the two groups. Furthermore, pathway analysis elucidated that the aforementioned alterations in lipids were primarily associated with the arachidonic acid metabolic pathway. The correlation between distinct lipid populations and clinical phenotypes was assessed through weighted gene coexpression network analysis (WGCNA). CONCLUSIONS: This study demonstrates that untargeted lipidomics assays conducted on breast tissue samples from patients with NPM exhibit noteworthy alterations in lipidomes. The findings of this study highlight the substantial involvement of arachidonic acid metabolism in lipid metabolism within the context of NPM. Consequently, this study offers valuable insights that can contribute to a more comprehensive comprehension of NPM in subsequent investigations. TRIAL REGISTRATION: Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine (Number: 2019-702-57; Date: July 2019).

Phenotypic evaluation of mast cells in bovine mammary tissue and mastitis in the context of fibrosis.

This research paper addresses the hypothesis that mast cells (MCs) contribute to the formation of mammary fibrosis. MCs are important immune regulatory and immune modulatory cells that play major roles in the inflammatory process. Since there is no detailed knowledge, this research study aimed to comparatively investigate the presence, localization, and immunophenotypes of MCs in healthy and mastitic mammary tissues. A total of 264 mammary samples were evaluated for the examination of mast cells and fibrosis. The mean mast cell number in both acute and chronic mastitis samples were very significantly higher than the control group P < 0.001). A 7.9-fold increase in the number of mast cells was found when the chronic mastitis group was compared with the control (healthy) group. Immunohistochemistry revealed presence of all three immune phenotypes in control and mastitic mammary samples (tryptase + (MCT), chymase + (MCC) and both chymase and tryptase + (MCTC). The mean MCT, MCC, and MCTC numbers in the chronic mastitis group were found to be significantly higher than the control (P < 0.001 for all three phenotypes) but did not differ significantly between control and acute mastitis samples. When the mean numbers of MCT, MCC, and MCTC in the control group and chronic mastitis group were compared, a 10.5, 7.8, and a 4.1-fold increase was observed, respectively. The amount of connective tissue was strongly increased in tissues with chronic mastitis and a 3.01-fold increase was detected compared to the control group. A statistically significant relation was also found between the amount of fibrosis and the increased number of total MCs (P < 0.001).

A mimicker of inflammatory breast carcinoma: Lupus mastitis and evolving imaging features.

Rare case of lupus mastitis in a 58-year-old female with discoid lupus erythematosus presented with fever, left breast swelling, and painful palpable lesion. Accurate imaging and histopathologic evaluation allowed for appropriate management and regression of breast findings with hydroxychloroquine treatment, emphasizing the need to avoid unnecessary biopsies and surgeries.

Diverse myeloid cells are recruited to the developing and inflamed mammary gland.

The immune system plays fundamental roles in the mammary gland, shaping developmental processes and controlling inflammation during infection and cancer.Here, we reveal unanticipated heterogeneity in the myeloid cell compartment duringdevelopment of virgin, pregnant, lactating and involuting mouse mammary glands,and in milk. We investigate the functional consequences of individual and compoundchemokine receptor deficiency on cell recruitment. Diverse myeloid cell recruitmentwas also shown in models of sterile inflammation and bacterial infection.Strikingly, we have shown that inflammation and infection can alter the abundanceof terminal end buds, a key developmental structure, within the pubertal mammarygland. This previously unknown effect of inflammatory burden during puberty couldhave important implications for understanding pubertal development.

Ultrasonic multimodality imaging features and the classification value of nonpuerperal mastitis.

OBJECTIVE: To explore the value of ultrasonic multimodality imaging for characterizing nonpuerperal mastitis (NPM) lesions and feasibility of distinguishing different subtypes. METHODS: Thirty-eight NPM lesions were assessed using conventional ultrasonography (US), strain elastography (SE), and contrast-enhanced ultrasound (CEUS). The lesions were confirmed pathologically and classified as granulomatous lobular mastitis (GLM), plasma cell mastitis (PCM), or nonspecific mastitis (NSM). Furthermore, diagnostic indicators were evaluated. The diagnostic performances of the modalities were compared using the area under the receiver operating characteristic curve (AUC). RESULTS: The overall morphological features on US differed significantly between the GLM and PCM groups (p = 0.002). Lesion size (≤10 mm) (p = 0.003) and mean SE score (p = 0.001) differed significantly between the PCM and NSM groups. The frequent NPM characteristic on CEUS was hyperenhancement with (or without) increased lesion size; intergroup differences were not significant. Breast Imaging Reporting and Data System > 3 was considered to indicate malignancy; accordingly, the accuracy of US alone, US with CEUS, and US with SE was 10.5%, 21.1%, and 65.8%, respectively. Moreover, the AUC for US with SE for classifying GLM and PCM was 0.616. CONCLUSION: CEUS cannot accurately classify NPM subtypes, while US and SE are valuable for classification.

Development and Pathology of the Equine Mammary Gland.

An understanding of the anatomy, histology, and development of the equine mammary gland underpins study of the pathology of diseases including galactorrhoea, agalactia, mastitis, and mammary tumour development. This review examines the prenatal development of the equine mammary gland and the striking degree to which the tissue undergoes postnatal development associated with the reproductive cycle. The gland is characterised by epithelial structures arranged in terminal duct lobular units, similar to those of the human breast, supported by distinct zones of intra- and interlobular collagenous stroma. Mastitis and mammary carcinomas are two of the most frequently described equine mammary pathologies and have an overlap in associated clinical signs. Mastitis is most frequently associated with bacterial aetiologies, particularly Streptococcus spp., and knowledge of the process of post-lactational regression can be applied to preventative husbandry strategies. Equine mammary tumours are rare and carry a poor prognosis in many cases. Recent studies have used mammosphere assays to reveal novel insights into the identification and potential behaviour of mammary stem/progenitor cell populations. These suggest that mammospheres derived from equine cells have different growth dynamics compared to those from other species. In parallel with studying the equine mammary gland in order to advance knowledge of equine mammary disease at the interface of basic and clinical science, there is a need to better understand equine lactational biology. This is driven in part by the recognition of the potential value of horse and donkey milk for human consumption, particularly donkey milk in children with 'Cow Milk Protein Allergy'.

Rare Initial Manifestation of Lupus as Lobular Panniculitis of the Breast-A Case Report and Review of the Literature.

ABSTRACT: Lupus mastitis is a rare complication of systemic or discoid lupus erythematosus with an uncommon initial presentation when limited to the breast. In this article, we report a 42-year-old woman who presented with constant pain and tenderness in her breasts. Ultrasound imaging of the left breast revealed a 14-mm oval mass, suspicious for malignancy; a needle core biopsy was performed. Sections showed necrosis of the fat lobules with associated mixed nodular lymphoplasmacytic aggregates. Karyorrhectic debris, fibrinoid necrosis of small vessels, and microcalcifications were all present while the background breast parenchyma was unremarkable. The diagnosis of lupus mastitis was rendered. Subsequent serology showed negative dsDNA but positive antinuclear antibodies, C4, and anti -Sjögren';s-syndrome-related antigen A antibodies. Clinical features of active systemic disease were not identified at the patient's follow-up dermatology appointment 1 month after the biopsy, and she elected management for her nodules with steroids. To the best of our knowledge, only 40 other cases of lupus mastitis have been reported in the English literature, of which 25 presented as a mass and only in 6 lupus mastitis of the breast was the initial presentation. In conclusion, we bring much needed awareness to lupus mastitis as the first presentation of disease.

Clinicopathological evaluation of idiopathic granulomatous mastitis patients: A retrospective analysis from a tertiary care hospital in Turkey.

Idiopathic granulomatous mastitis (IGM) is a chronic inflammatory disease of the breast with unknown etiology that is characterized by granuloma formation. We analyzed the clinical, radiological, and therapeutic approaches; the recurrence rate of the disease; and the pathological findings diagnosed with mastitis in a retrospective study. We evaluated a total of 77 patients subjected to core needle or excisional biopsy with preliminary diagnosis of mastitis between January 2017-December 2019 who diagnosed with IGM, nonspecific mastitis/abscess, or periductal mastitis/plasma cell mastitis as a result of their pathological assessment. The mean age was 39.24 ± 10.6. Though 65 patients were diagnosed with IGM (84.4%), other diagnoses were reported as nonspecific mastitis/abscess (n = 9), periductal mastitis (n = 2) and plasma cell mastitis (n = 1). Recurrence occurred in 30 (39%) patients during follow-up. In patients without IGM, the number of 5-year postpartum mastitis diagnoses was significantly higher (p = 0.0008) while number of 2-year postpartum mastitis diagnoses was lower (p = 0.255) compared to those in IGM patients. The rates of axillary lymphadenopathy, bacterial culture, parity, and menopausal status were not different in patients without IGM. Linear correlation analysis did not reveal a significant relationship between radiological preliminary diagnosis and pathological diagnosis with BI-RADS classification. A detailed assessment, accompanied with clinical, radiological, and pathological findings, should be performed to achieve an accurate diagnosis and effective patient management in IGM. Furthermore, IGM should always be considered in the differential diagnosis of mastitis among breast masses.

Somatic cell count in buffalo milk using fuzzy clustering and image processing techniques.

This research communication presents an automatic method for the counting of somatic cells in buffalo milk, which includes the application of a fuzzy clustering method and image processing techniques (somatic cell count with fuzzy clustering and image processing|, SCCFCI). Somatic cell count (SCC) in milk is the main biomarker for assessing milk quality and it is traditionally performed by exhaustive methods consisting of the visual observation of cells in milk smears through a microscope, which generates uncertainties associated with human interpretation. Unlike other similar works, the proposed method applies the Fuzzy C-Means (FCM) method as a preprocessing step in order to separate the images (objects) of the cells into clusters according to the color intensity. This contributes signficantly to the performance of the subsequent processing steps (thresholding, segmentation and recognition/identification). Two methods of thresholding were evaluated and the Watershed Transform was used for the identification and separation of nearby cells. A detailed statistical analysis of the results showed that the SCCFCI method is able to provide results which are consistent with those obtained by conventional counting. This method therefore represents a viable alternative for quality control in buffalo milk production.

Size of supernumerary teats in sheep correlates with complexity of the anatomy and microenvironment.

Supernumerary nipples or teats (polythelia) are congenital accessory structures that may develop at any location along the milk line and have been implicated in the pathogenesis of mastitis. We describe the anatomy and histology of 27 spontaneously occurring supernumerary teats from 16 sheep, delineating two groups of teats - simple and anatomically complex - according to the complexity of the anatomy and microenvironment. Anatomically complex supernumerary teats exhibited significantly increased length and barrel diameter compared with simple supernumerary teats. A teat canal and/or teat cistern was present in anatomically complex teats, with smooth muscle fibres forming a variably well-organised encircling teat sphincter. Complex supernumerary teats also exhibited immune cell infiltrates similar to those of normal teats, including lymphoid follicle-like structures at the folds of the teat cistern-teat canal junction, and macrophages that infiltrated the peri-cisternal glandular tissue. One complex supernumerary teat exhibited teat end hyperkeratosis. These anatomical and histological features allow inference that supernumerary teats may be susceptible to bacterial ingress through the teat canal and we hypothesise that this may be more likely in those teats with less well-organised encircling smooth muscle. The teat cistern of anatomically complex teats may also constitute a focus of milk accumulation and thus a possible nidus for bacterial infection, potentially predisposing to mastitis. We suggest that size of the supernumerary teat, and relationship to the main teats, particularly in the case of 'cluster teats', should be considerations if surgical removal is contemplated.

Combining ultrasonography and mammography to improve diagnostic accuracy of plasma cell mastitis.

OBJECTIVE: To evaluate the diagnostic value of ultrasonography and mammography for plasma cell mastitis. METHODS: The ultrasonographic and mammographic images of 111 women with histopathologically confirmed plasma cell mastitis were retrospectively analyzed. The diagnostic accuracy of the two imaging methods was compared. RESULTS: Ultrasonography identified 91 out of 111 (82.0%) patients with plasma cell mastitis, while the other twenty (18.0%) patients were misdiagnosed. Mammography identified 83 (74.8%) out of 111 patients with plasma cell mastitis. Nineteen (17.1%) patients were misdiagnosed. There was no significant difference between the diagnostic accuracy of using two imaging tests (P = 0.127). Mammography clouds identified 11 out of 20 patients who were not diagnosed by ultrasonography. Meanwhile, 19 of the 28 cases misdiagnosed with mammography were correctly identified by ultrasonography. Overall, 91.9% (102/111) of the patients were identified by the combination of ultrasonography and mammography, which yielded statistically significant higher accuracy than using each single test only (P < 0.05). CONCLUSIONS: In diagnosis of plasma cell mastitis, high-frequency ultrasonography and mammography should be combined to improve the diagnostic accuracy.

Dimethyl itaconate protects against lippolysacchride-induced mastitis in mice by activating MAPKs and Nrf2 and inhibiting NF-κB signaling pathways.

Mastitis, as the main disease to affect the dry dairy cow with the characterized by increasing number of somatic cells in milk and reducing milk production, has been known as one of the most serious expensive disease for the dairy industry. Escherichia coli (E.coli), a gram negative bacterial, have normally been considered to be an opportunistic pathogen that can invade the mammary gland sometimes to cause inflammatory diseases. Lippolysacchride (LPS), as the co-cell wall component of the Escherichia coli (E.coli), is the main virulence factors to induce acute inflammation. Itaconate is an endogenous metabolite which has recently been reported to regulate the macrophage function and has the ability to reduce the secretion of pro-inflammatory cytokines, such as IL-6 and IL-12. Here, the aim of this study is to investigate the protective role of dimethyl itaconate (DI)-the membranepermeable derivative of itaconate, on LPS-induced mastitis in mice. To establish the model of mastitis, mice 5-7 day after delivery were utilized by nipple duct injection of LPS, while DI was treated 24h intraperitoneally before LPS injection. Further, the hematoxylin-eosin (H&E) staining was used to evaluate the pathological changes of the mammary gland, the inflammatory cytokines of TNF-α and IL-1ß and the myeloperoxidase (MPO) activity were also measured respectively by enzyme-linked immunosorbent assay (ELISA) and MPO assay kit. To clarify the underling mechanisms of the protective role of DI on mastitis, the MAPKs, NF-κB and Nrf2 signaling pathways were detected via western blotting. The results demonstrated that DI markedly decreased the pathological injury of mammary, and considerably reduced the production of TNF-α and IL-1ß, as well as up-regulated the Nrf2, HO-1, phosphorylation of p38 and ERK, but down-regulated TLR4 and phosphorylation of p65 NF-κB. Our research recommended that DI ameliorated LPS-induced mastitis which highlights itaconate may as a potential candidate to protect against mastitis.

Skin diseases of the breast and nipple: Inflammatory and infectious diseases.

Certain dermatologic conditions are unique to the breast and nipple, whereas others may incidentally involve these structures. All require a nuanced approach to diagnosis and treatment because of the functional, sexual, and aesthetic importance of this area. The lactating patient requires special management because certain treatment options are contraindicated. All dermatologic conditions involving the breast and nipple require careful evaluation because malignancy of the breast can be mistaken for a benign condition or may trigger the development of certain dermatologic conditions. The second article in this continuing medical education series reviews common and uncommon inflammatory and infectious conditions of the breast and nipple and provides insight into both the diagnosis and the treatment of this heterogeneous group of diseases. For the purposes of this article, these conditions are divided into 4 distinct categories: 1) dermatitis; 2) radiation-induced changes; 3) mastitis; and 4) miscellaneous dermatologic conditions of the breast and nipple.

IgG4-related sclerosing mastitis in a 49-year-old patient with multiple, tumor-like nodules-Diagnostic accuracy of core needle biopsy.

Recently, it has been reported that IgG4-related disease may occur in the breast manifesting as nodular sclerosing interstitial mastitis. Here we report a case with multiple tumor-like nodules in one breast. The histologic diagnosis was established on core needle biopsies, and treatment was initiated without open biopsy. Diagnosis of IgG4-related sclerosing mastitis should be suspected in cases of tumor-like lesions on imaging with an interstitial plasma cell-rich sclerosing inflammation on histology.

Exosomes Play an Important Role in the Progression of Plasma Cell Mastitis via the PI3K-Akt-mTOR Signaling Pathway.

BACKGROUND: Plasma cell mastitis (PCM) is one of the most frequently encountered inflammatory diseases of the nonlactating breast. However, its pathogenesis has remained unknown. METHODS: In this study, we observed the ultrastructure changes of PCM by a transmission electron microscope. The transcriptome expression difference of exosomes was detected by RNA-Seq; then, we confirmed the key difference genes by western blot and immunohistochemistry. Finally, we established the mouse PCM model by tissue homogenate injection to validate the role of exosomes on the progression of PCM. RESULTS: The analysis of the exosomal transcriptome expression difference between PCM and normal mammary tissues using RNA-Seq showed the differential genes and enrichment pathways involved in the course of PCM. The decreased HSP90AA1 and EEF2, excessive production of p-AKT, and p-mTOR were consistent with clinical specimens. Inhibition of exosome secretion significantly inhibited inflammatory cell infiltration, and the mammary duct had maintained a better structure in the PCM mouse model. CONCLUSION: Our results revealed the role of exosomes acting as critical signal introduction facilitators in the progression of plasma cell mastitis and identified potential key genes in the regulation of this process. These results will help to dissect the molecular mechanism of PCM and provide therapeutic targets.

Bifunctional role of ephrin A1-Eph system in stimulating cell proliferation and protecting cells from cell death through the attenuation of ER stress and inflammatory responses in bovine mammary epithelial cells.

Structural and functional development of the mammary gland is constant in the mammary gland life cycle. Eph receptors and their ligands, ephrins, control events through cell-to-cell interactions during embryonic development, and adult tissue homeostasis; however, little information on participation of ephrin A1, a representative ligand of the Eph receptor, in the development and function of normal mammary glands is known. In this study, we demonstrated functional effects of the ephrin A1-Eph system and mechanisms of its action on bovine mammary epithelial (MAC-T) cells. The in vitro cultured MAC-T cells expressed the ephrin A1 ligand and EphA1, A2, A4, A7, and A8 among the eight members of the Eph A family. Our results revealed that ephrin A1 induced MAC-T cell cycle progression and stimulated cell proliferation with abundant expression of nucleic PCNA and cyclin D1 proteins. Additionally, ephrin A1 induced activation of intracellular signaling molecules involved in PI3 K/AKT and MAPK signaling, and the proliferation-stimulating effect of ephrin A1 was mediated by activation of these pathways. Furthermore, ephrin A1 influenced expression and activation of various ER stress-related proteins and protected MAC-T cells from stress-induced cell death. Finally, ephrin A1 alleviated LPS-induced cell death through down-regulation of inflammatory cytokines. In conclusion, the results of this study suggest that the Eph A-ephrin A1 system is a positive factor in the increase and maintenance of epithelial cells in mammary glands of cows; the signaling system contributes to development, remodeling, and functionality of normal mammary glands and could overcome mastitis in cows and other mammals.