Mammary Gland Disease Research Articles

The effect of the nisin-based pharmaceutical formulation used in the treatment plan for cows with subclinical mastitis on the milk microbiota

Due to the growing threat of antimicrobial resistance, the search and development of new drugs to treat infectious mammary gland diseases of high yielding cows is an urgent task. The paper presents data on the microbiota composition of milk from high yielding cows suffering from subclinical mastitis; 144 microbial isolates were recovered from 70 milk samples; with the highest number of Staphylococcus aureus and Streptococcus dysgalactiae detected (22.2 and 16.0%, respectively). The study showed that a significant number of Staphylococcus aureus isolates (53.1%) were resistant to I generation cephalosporins; 52.6% of the isolated Streptococcus dysgalactiae strains showed resistance to tetracyclines; 33.3% of Staphylococcus haemolyticus isolates were resistant to macrolides. 42.1; 35.3 and 62.5% of Enterococcus faecium, Aerococcus viridans and coliform bacteria isolates, respectively, were resistant to penicillins. 38.5% of Staphylococcus epidermidis isolates were found to be resistant to tetracyclines. Corynebacterium pseudotuberculosis isolates showed equal resistance to penicillin and tetracycline antimicrobials (20.0%). The research revealed presence of multi-drug resistant coliform bacteria, Streptococcus dysgalactiae, Aerococcus viridans, Staphylococcus aureus strains. Experiments to study the effect of the new nisin-based pharmaceutical formulation on microbiota of milk from cows with subclinical mastitis were carried out using 35 high yielding cows. A microbiological testing of cow milk on day 14 from the beginning of the treatment showed that the number of microbiota-free samples increased to 88.6%, while in 1.4% of cases Staphylococcus aureus isolates were recovered (103 CFU/mL). The titers of coliform and Staphylococcus aureus bacteria isolated in 1.4% (101 CFU/mL) and 2.7% (102 CFU/mL) of cases, respectively, were not etiologically significant.

The efficacy of intravenous application of the Mycobacterium Cell Wall Fraction (AMPLIMUNE) in the treatment of subclinical mastitis caused by S. Aureus.

The aim of the study was to investigate the effect of the immunostimulant Mycobacterium Cell Wall Fraction (MCWF) on the treatment of S. aureus SCM by intravenous application. The study included 45 HF dairy cows in 2nd and 3rd month after parturition divided into three groups (n = 15 per group): the MC + group - cows with S. aureus SCM treated with MCWF; the MC- group - cows with S. aureus SCM, with no treatment; and the C group - the control group of healthy cow with no treatment. Samples were collected 0th (I sample), 7th (II), and 14th day (III) from the day of SCM diagnosis and on day 21st (IV). A greater influx of leukocytes was confirmed into milk after 7 days after MCWF treatment in MC + group, which was followed by increase of WBC and LYM in blood. These results support the hypothesis of effective action of MCWF, and in quarters with lower-grade infection, bacteriological cure was achieved. The MC- group had a statistically higher concentration of TBARS and CAT activity in milk, while MC + group had lower blood serum LDH activity, which indicates a positive effect of the MCWF application and a lower exposure of the tissue to lipide peroxidation and inflammation caused by S. aureus. The application of MCWF would give new possibilities in the prevention and therapy of mammary gland diseases without fear of the presence of residues and the emergence of bacterial resistance. In future studies, the effects of local and systemic application of MCWF in the treatment of S. aureus SCM should be compared.

A Rapid and Inexpensive PCR Test for Mastitis Diagnosis Based on NGS Data.

Mastitis is a common mammary gland disease of dairy cattle caused by a wide range of organisms including bacteria, fungi and algae. Mastitis contributes to economic losses of dairy farms due to reduced yield and poor quality of milk. Since the correct identification of pathogens responsible for the development of mastitis is crucial to the success of treatment, it is necessary to develop a quick and accurate test to distinguish the main pathogens causing this disease. In this paper, we describe the development of a test based on the multiplex polymerase chain reaction (PCR) method allowing for the identification of Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis and Staphylococcus aureus. When creating our test, we relied on the results from new generation sequencing (NGS) for accurate determination of species affiliation. The multiplex PCR test was verified on 100 strains including veterinary samples, ATCC and Polish Collection of Microorganisms (PCM) reference strains. The obtained results indicate that this test is accurate and displays high specificity. It may serve as a valuable molecular tool for the detection of major mastitis pathogens.

ПРИЧИНЫ ВЫБЫТИЯ ГОЛШТИНИЗИРОВАННОГО ЧЕРНО-ПЕСТРОГО И ГОЛШТИНСКОГО СКОТА В ЗАВИСИМОСТИ ОТ УРОВНЯ ИНБРИДИНГА

The aim of the study is to investigate the influence of the inbreeding level on the causes of culling. The paper presents the results of the analysis of the influence of the inbreeding level on the causes of cul-ling in the population of Black-and-White and Holstein cattle in the Moscow Region (n = 31,835). The inbreeding coefficient (Fx) was calculated using the Wright-Kislovsky formula. Three groups were formed: the first (n = 25,320) included those with Fx = 0.2–1 %, the second (n = 6,214) with Fx = 1.01–6.25 %, and the third (n = 301) with Fx = 6.27–31.25 %. A systematic increase in the percentage of culling due to limb disease, gynecological diseases, other non-infectious diseases, bronchopneumonia, udder injuries, salpingitis, necrobacteriosis, abortion, and old age is noted. A wave-like increase in the reasons for leaving by groups was noted: metabolic disorders from 7.57 % in the first to 7.64 % in the third group; gynecological diseases – from 6.37 to 7.31; zoobrac – from 5.46 to 5.65; mammary gland diseases – from 4.30 to 6.65; low productivity – from 2.94 to 3.32; limb injuries – from 0.49 to 1 %. The percentage of exterior defects increased from 0.15 % in the first group to 0.21 % in the second, abomasum displacement, rumen acidosis, invasive diseases and pyometra also tended to increase and amounted to 0.07 and 0.13 %; 0.06 and 0.08; 0.04 and 0.08; 0.004 and 0.02 %, respectively. It can be concluded that the increase in the level of inbreeding affected the percentage of cows culled on dairy complexes in the Moscow Region. A reliable difference was noted between all groups according to the Bartlett test and Cochran's Q test at a significance level of α = 0.05.

Organopathology of the mammary gland in female carnivores: current state of research issues

Organopathology of the mammary gland in female carnivores: current state of research issues

A Decision Tree to Guide Human and Mouse Mammary Organoid Model Selection.

Over the past 50 years, researchers from the mammary gland field have launched a collection of distinctive 3D cell culture systems to study multiple aspects of mammary gland physiology and disease. As our knowledge about the mammary gland evolves, more sophisticated 3D cell culture systems are required to answer more and more complex questions. Nowadays, morphologically complex mammary organoids can be generated in distinct 3D settings, along with reproduction of multiple aspects of the gland microenvironment. Yet, each 3D culture protocol comes with its advantages and limitations, where some culture systems are best suited to study stemness potential, whereas others are tailored towards the study of mammary gland morphogenesis. Therefore, prior to starting a 3D mammary culture experiment, it is important to consider and select the ideal culture model to address the biological question of interest. The number and technical requirements of novel 3D cell culture methods vastly increased over the past decades, making it currently challenging and time consuming to identify the best experimental testing. In this chapter, we provide a summary of the most promising murine and human 3D organoid models that are currently used in mammary gland biology research. For each model, we will provide a brief description of the protocol and an overview of the expected morphological outcome, the advantages of the model, and the potential pitfalls, to guide the reader to the best model of choice for specific applications.

Analysis of Host Specific Risk Factors Associated with Occurrence of Bovine Clinical Mastitis in Tamil nadu

Globally, bovine mastitis is the most prevalent inflammatory disease of mammary gland that causes economic loss to the dairy industry. It is vital to study the risk factors associated with mastitis in order to design suitable prevention and control strategies. With this objective a survey was conducted among dairy farmers (n=300) in Tamil Nadu to identify the host specific risk factors associated with clinical mastitis. Species (OR=1.88, CI 95%= 1.15- 3.08, p=0.01), breed (OR=0.22, CI 95%= 0.12- 0.41, p<0.001), parity of cow (OR=0.69, CI 95%= 0.51- 0.93, p=0.02), lactation stage (OR=0.55, CI 95%= 0.40- 0.74, p<0.001) and milk yield (OR=2.77, CI 95%= 1.95- 3.93, p<0.001) were identified as significant risk factor for clinical mastitis in lactating dairy cows in the study area. Understanding these factors assists dairy farmers in mitigating clinical mastitis in their herds.

Molecular complexity of mammary glands development: a review of lactogenic differentiation in epithelial cells

The mammary gland is a dynamic organ with various physiological processes like cellular proliferation, differentiation, and apoptosis during the pregnancy-lactation-involution cycle. It is essential to understand the molecular changes during the lactogenic differentiation of mammary epithelial cells (MECs, the milk-synthesizing cells). The MECs are organized as luminal milk-secreting cells and basal myoepithelial cells (responsible for milk ejection by contraction) that form the alveoli. The branching morphogenesis and lactogenic differentiation of the MECs prepare the gland for lactation. This process is governed by many molecular mediators including hormones, growth factors, cytokines, miRNAs, regulatory proteins, etc. Interestingly, various signalling pathways guide lactation and understanding these molecular transitions from pregnancy to lactation will help researchers design further research. Manipulation of genes responsible for milk synthesis and secretion will promote augmentation of milk yield in dairy animals. Identifying protein signatures of lactation will help develop strategies for persistent lactation and shortening the dry period in farm animals. The present review article discusses in details the physiological and molecular changes occurring during lactogenic differentiation of MECs and the associated hormones, regulatory proteins, miRNAs, and signalling pathways. An in-depth knowledge of the molecular events will aid in developing engineered cellular models for studies related to mammary gland diseases of humans and animals.

Аналитический обзор состояния репродуктивного здоровья девочек и девушек Московской области. Анализ работы

Introduction. The protection of the reproductive health of the younger generation is one of the most significant problems due to the steady growth of various gynecological diseases, including those that are asymptomatic, which has a significant impact on the reproductive potential of the young population. Purpose to reveal the prevalence of gynecological pathologies among girls in the Moscow region. Material and methods. We have analyzed the main gynecologic diseases among patients aged 0–17 years according to the results of preventive examinations and data of visits to the pediatric gynecologist in the outpatient clinic for the year 2021. Results. Recent analytical data on the prevalence of gynecological morbidity of girls and young women in Moscow region showed that in children aged 0–4 years and 5–9 years, inflammatory diseases of the vulva and vagina (vulvitis) and labia minora adhesions predominate. In patients aged 10–14 years gynecological pathology is represented by various menstrual cycle disorders, dysmenorrhea, inflammatory diseases of the vulva and vagina (vulvitis), non-inflammatory ovarian diseases (follicular cysts and cysts of the yellow body of the ovary) and also mammary gland diseases. The predominant gynecological pathology in girls aged 15–17 is inflammatory diseases of the vulva and vagina, menstrual disorders, non-inflammatory ovarian diseases (follicular cysts, cysts of the corpus luteum), fallopian tubes and the vagina, breast diseases, and sexually transmitted infections are also frequent. Conclusion. We can talk about the general trends in the prevalence of gynecological morbidity among girls and young women in Moscow region and in the whole territory of the Russian Federation. Following the order of the Russian Ministry of Health of 20.10.2020 № 1130n «On approval of the Order of medical care in the profile „obstetrics and gynecology“», we can achieve a reduction in gynecological morbidity among girls and young girls in the Moscow region by improving specialized gynecological care

Artificial intelligence assisted diagnoses of fine-needle aspiration of breast diseases: a single-center experience

Abstract: Purpose: Since 2010, physicians from Afghanistan have been uploading images of histological and cytological specimens to a telemedicine internet platform (iPath network) for expert evaluation. From this collective work, all cases with fine-needle aspirations (FNA) of mammary gland diseases were extracted and analyzed. The aim of the present retrospective feasibility study is to investigate the utility of artificial intelligence assisted diagnoses in fine-needle aspiration (FNA) of breast diseases.Material and Methods: A total of 3304 microphotographic images from 438 patients of smears from FNA of the mammary gland were available for this study. Telemedical expert diagnoses from 4 experienced cytopathologists were available in all 438 cases. Their diagnosis (malignant tumor of the mammary gland or benign mammary gland disease) was set as the gold standard. AI analysis was performed using i) clinical context data and ii) two different image recognition methods to determine the probability values for the presence of malignant breast tumor. Youden index and AUC (area under the curve) were used to evaluate test performance. Results: A score for invasive breast cancer (IBC) calculated from contextual variables agreed with the expert diagnosis (accuracy) in 85.2% and with the two image recognition systems in 78.4% and 65.2%. This simplifies health healthcare management of breast diseases in low income countries as in many patients the less expensive and less time-consuming technique of FNA may replace a histological examination.Conclusion: Image classification and analysis of context variables can be used to test the validity and plausibility of cytologic diagnoses, especially when cytologic interpretation has to be performed by people who are inexperienced in cytopathology.

Detection of immunoreactive proteins of Escherichia coli, Streptococcus uberis, and Streptococcus agalactiae isolated from cows with diagnosed mastitis.

Mastitis is a widespread mammary gland disease of dairy cows that causes severe economic losses to dairy farms. Mastitis can be caused by bacteria, fungi, and algae. The most common species isolated from infected milk are, among others, Streptococcus spp., and Escherichia coli. The aim of our study was protein detection based on both in silico and in vitro methods, which allowed the identification of immunoreactive proteins representative of the following species: Streptococcus uberis, Streptococcus agalactiae, and Escherichia coli. The study group included 22 milk samples and 13 serum samples obtained from cows with diagnosed mastitis, whereas the control group constituted 12 milk samples and 12 serum samples isolated from healthy animals. Detection of immunoreactive proteins was done by immunoblotting, while amino acid sequences from investigated proteins were determined by MALDI-TOF. Then, bioinformatic analyses were performed on detected species specific proteins in order to investigate their immunoreactivity. As a result, we identified 13 proteins: 3 (molybdenum cofactor biosynthesis protein B, aldehyde reductase YahK, outer membrane protein A) for E. coli, 4 (elongation factor Tu, tRNA uridine 5-carboxymethylaminomethyl modification enzyme MnmG, GTPase Obg, glyceraldehyde-3-phosphate dehydrogenase) for S. uberis, and 6 (aspartate carbamoyltransferase, elongation factor Tu, 60 kDa chaperonin, elongation factor G, galactose-6-phosphate isomerase subunit LacA, adenosine deaminase) for S. agalactiae, which demonstrated immunoreactivity to antibodies present in serum from cows with diagnosed mastitis. Due to the confirmed immunoreactivity, specificity and localization in the bacterial cell, these proteins can be considered considered potential targets in innovative rapid immunodiagnostic assays for bovine mastitis, however due to the limited number of examined samples, further examination is needed.

Cell scientist to watch – Felicity Davis

ABSTRACT Felicity Davis studied Pharmacy and then pursued her PhD, working on intracellular Ca2+ signalling in breast cancer metastasis, with Sarah Roberts-Thomson and Greg Monteith at the University of Queensland, Australia. She then joined the lab of Jim Putney at the National Institute of Environmental Health Sciences (NIH/NIEHS) in North Carolina as an NIH Visiting Fellow to study physiological functions of store-operated Ca2+ channels. Felicity then completed a second postdoc with Christine Watson at the University of Cambridge, UK, where she investigated the differentiation potential of mammary stem cells using single-cell lineage tracing. She set up her independent research group in Australia as an NHMRC Fellow in 2018. Since 2021, Felicity has led a lab at the EMBL-Australia Node in Single Molecule Science in Sydney and a team at Aarhus University in Denmark, funded by a Novo Nordisk Foundation Young Investigator Award. Her two groups use advanced imaging and novel mouse models to explore roles for intracellular Ca2+ signalling in mammary gland development, function and disease.

Fibrocystic disease of mammary gland in a Guinea pig: A case report

Fibrocystic disease of mammary gland in a Guinea pig: A case report

Attempt to Evaluate the Influence of Morphology, Blood Flow, and Hardness in Mammary Gland Malignant Disease

It is important to make an appropriate diagnosis category by evaluating the morphology, blood flow, and hardness of mammary gland disease in breast ultrasound, such as screening and detailed examination. Therefore, understanding the characteristics and effects of B-mode (BM), color Doppler (CD), and elastography (EG) in ultrasonography is considered to lead to improvement in examination accuracy. In this study, we clarified the impact of each function on qualitative diagnosis, with the aim of assisting technologists with high-accuracy breast ultrasound. The subjects were 531 malignant tumor cases. The final evaluation of ultrasonography was classified into 5 levels, BM was classified into 5 levels, CD was classified into 4 levels based on blood flow evaluation, and EG was classified into 9 levels based on the Tsukuba elasticity score. The contribution rates of BM, CD, and EG were 70.4%, 15.0%, and 14.6% in all cases (correlation ratio 0.87). BM was most important at the time of breast ultrasound. No difference was observed between CD and EG. In the evaluation by malignant tumor, each characteristic was seen in the degree of influence. It became clear that comprehensive evaluation is important for benign/malignant evaluation and histological-type estimation.

Pharmacodynamic structure of deer antler base protein and its mammary gland hyperplasia inhibition mechanism by mediating Raf-1/MEK/ERK signaling pathway activation.

Mammary gland hyperplasia (MGH) is a common mammary disease whose main pathogenesis is the disruption of estradiol (E2) and progesterone (P) secretion, thereby causing overproliferation of mammary epithelial cells and mammary gland tissue hyperplasia. Deer antler base is a traditional Chinese medicine that has been used for many years to treat MGH. However, its pharmacological mechanism and pharmacodynamic material basis are unclear. In this study, we for the first time used the graded salting method to classify deer antler base protein (CNCP) as CNCP-A, CNCP-B, and CNCP-C and explored the pharmacological mechanism of the anti-MGH properties of CNCP. We found that CNCP could regulate the hormonal levels of E2, P, and follicle stimulating hormone (FSH) and improve the histopathological condition. The potential mechanism might be related to the recombinant C-Raf proto oncogene serine/threonine protein kinase/mitogen-activated protein/extracellular regulated protein kinase (Raf-1/MEK/ERK) signaling pathway. By upregulating the protein expression of the follicle stimulating hormone receptor (FSHR), cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) inhibited the activation of the downstream Raf-1/MEK/ERK signaling pathway, which in turn inhibited the proliferation of mammary epithelial cells. We analyzed the physicochemical properties of CNCP-A, CNCP-B, and CNCP-C and obtained CNCP-C-I by column chromatographic purification of the best pharmacophore protein CNCP. Using high-performance liquid gel filtration chromatography (HPGFC), we determined the molecular weight of CNCP-C-I and identified it by high-performance liquid tandem mass spectrometry (LC-MS/MS) to obtain the first match for a high confidence protein KRT1. This study provides a theoretical basis for the development of effective traditional Chinese medicines with low toxicity levels for the prevention and treatment of mammary gland diseases.

Novel polymorphisms of the KCNB1 gene and their association with production traits in Indian Sahiwal cattle

Mastitis in cattle is a prevalent mammary gland disease that contributes significantly to the increase in veterinary expenditures in the dairy sector. KCNB1 (Potassium voltage-gated channel, subfamily B member 1) gene is involved in regulating apoptosis, cell proliferation and differentiation, udder epithelial tissue maintenance and repair, mammary gland development and recommended as a candidate gene for production related traits in cattle. The purpose of this research was to detect the genetic variants of KCNB1 gene in Sahiwal cattle and to analyze the association between polymorphisms with milk production traits, udder traits, and teat traits in Sahiwal cattle. A total of 87 cattle were genotyped by polymerase chain reaction-restriction fragment length polymorphism technique. Two single nucleotide polymorphisms within the non-coding sequence of KCNB1 gene were identified (g.78216220G>A and g.78216335A>G). Analysis of productivity traits within the genotyped animals revealed that the SNP1-Msp1 locus (g.78216220G>A) located at intron 1 was associated with milk production traits, but the SNP2-BspHI locus (g.78216335A>G) had no association with milk production. Significant associations were also observed between SNP1-Msp1 and SNP2-BspHI loci with both udder and teat traits. Our results demonstrate that polymorphisms in the cattle KCNB1 gene were associated with milk production, udder and teat traits and might be utilized as a genetic marker for marker-assisted selection in cattle breeding programs.

Tea Polyphenols Protect the Mammary Gland of Dairy Cows by Enhancing Antioxidant Capacity and Regulating the TGF-β1/p38/JNK Pathway.

Tea polyphenols (TPs) are the main active substances in tea and they have many beneficial effects, such as anti-inflammation, antioxidant, anti-cancer and metabolic regulation effects. The quality of milk is affected by mammary gland diseases and there are substantial economic losses resulting from reduced milk production as a consequence of inflammatory injury of the mammary gland. In this study, transcriptome analysis and molecular biology techniques were used to study the effects of TPs on inflammatory injury of the mammary gland. After intervention with TPs, a total of 2085 differentially expressed genes were identified, including 1189 up-regulated genes and 896 down-regulated genes. GO analysis showed that differentially expressed genes played an important role in proton transmembrane transport, oxidation-reduction reactions and inflammatory response. KEGG enrichment suggested that differential genes were concentrated in the TGF-β pathway and active oxygen metabolism process. Experiments were performed to confirm that TPs increased SOD, CAT, T-AOC and GSH-Px content along with a reduction in MDA. Meanwhile, TPs inhibited the expression of TGF-β1 and reduced the phosphorylation of p38 and JNK. The expression of inflammatory cytokines IL-1β, IL-6 and TNF-α were significantly decreased after intervention with TPs. In summary, all the data indicated that TPs protected the mammary gland by enhancing the antioxidant capacity and down-regulating the TGF-β1/p38/JNK pathway.

The relationship of the occurrence of mastitis in cats in daughters with parents according to anamnesis

Studies on the relationship between the occurrence of mastitis in daughters and parents according to anamnesis were carried out in the period from 2013 to 2021. on the basis of veterinary clinics in the cities of Rostov-on-Don (Dr. also on the basis of the North Caucasian Zonal Scientific Research Veterinary Institute - a branch of the FGBNU FRANC. The study included 235 cats admitted to veterinary clinics with a diagnosis of mastitis and with reliable anamnestic data of parents (mothers). For the first time, we found that mothers whose daughters fell ill with inflammation of the mammary gland most often developed pathologies such as mastitis and tumors of the mammary gland, while in the largest number of animals the pathology proceeded in a moderate or severe form. Thus, it can be argued that there is a correlation between the occurrence of mastitis in daughters and the presence of breast diseases in their mothers and the severity of the course of the pathological process. In the course of the research, an analysis was also made for the first time of the severity of the course of mastitis in relation to parents (mother-daughter). When analyzing the anamnestic data, it was found that in cats whose mothers had a history of mammary gland diseases, severe and moderate mastitis is most often noted. Significantly less often, a mild course of mastitis is recorded. And in cats, mothers who did not have a history of mammary gland diseases most often noted a mild course of the pathological process, while moderate and severe were recorded much less frequently. Based on the data obtained, it can be concluded that the daughters obtained from mothers with breast diseases in the anamnesis are dominated by severe and moderate inflammation of the mammary gland.

Best practices to quantify the impact of reproductive toxicants on development, function, and diseases of the rodent mammary gland

Work from numerous fields of study suggests that exposures to hormonally active chemicals during sensitive windows of development can alter mammary gland development, function, and disease risk. Stronger links between many environmental pollutants and disruptions to breast health continue to be documented in human populations, and there remain concerns that the methods utilized to identify, characterize, and prioritize these chemicals for risk assessment and risk management purposes are insufficient. There are also concerns that effects on the mammary gland have been largely ignored by regulatory agencies. Here, we provide technical guidance that is intended to enhance collection and evaluation of the mammary gland in mice and rats. We review several features of studies that should be controlled to properly evaluate the mammary gland, and then describe methods to appropriately collect the mammary gland from rodents. Furthermore, we discuss methods for preparing whole mounted mammary glands and numerous approaches that are available for the analysis of these samples. Finally, we conclude with several examples where analysis of the mammary gland revealed effects of environmental toxicants at low doses. Our work argues that the rodent mammary gland should be considered in chemical safety, hazard and risk assessments. It also suggests that improved measures of mammary gland outcomes, such as those we present in this review, should be included in the standardized methods evaluated by regulatory agencies such as the test guidelines used for identifying reproductive and developmental toxicants.

Longitudinal Intravital Microscopy Using a Mammary Imaging Window with Replaceable Lid

The branched structure of the mammary gland is highly dynamic and undergoes several phases of growth and remodeling after birth. Intravital microscopy in combination with skin flap surgery or implantation of imaging windows has been used to study the dynamics of the healthy mammary gland at different developmental stages. Most mammary imaging technologies are limited to a time frame of hours to days, whereas the majority of mammary gland remodeling processes occur in time frames of days to weeks. To study mammary gland remodeling, methods that allow optical access to the tissue of interest for extended time frames are required. Here, an improved version of the titanium mammary imaging window with a replaceable lid (R.MIW) is described that allows high-resolution imaging of the mammary gland with a cellular resolution for up to several weeks. Importantly, the R.MIW provides tissue access over the entire duration of the intravital imaging experiment and could therefore be used for local tissue manipulation, labeling, drug administration, or image-guided microdissection. Taken together, the R.MIW enables high-resolution characterization of the cellular dynamics during mammary gland development, homeostasis, and disease.