Fat Pad Transplantation Research Articles

Bronchoscopic management of bronchopleural fistula using free fat pad transplant with platelet-rich plasma: a case study

BackgroundA bronchopleural fistula (BPF) occurs when an abnormal connection forms between the bronchial tubes and pleural cavity, often due to surgery, infection, trauma, radiation, or chemotherapy. The outcomes of both surgical and bronchoscopic treatments frequently prove to be unsatisfactory.Case presentationHere, we report a case of successful bronchoscopic free fat pad transplantation combined with platelet-rich plasma, effectively addressing a post-lobectomy BPF. Contrast-enhanced chest tomography revealed pleural thickening with heterogeneous consolidations over the right upper and middle lobes, indicative of destructive lung damage and bronchiectasis. The patient underwent thoracoscopic bilobectomy of the lungs. During surgery, severe adhesions and calcification of the chest wall and lung parenchyma were observed. The entire hilar structure was calcified, presenting challenges for dissection, despite the assistance of energy devices. Bronchoscopic intervention was required, during which two abdominal subcutaneous fat pads were retrieved.ConclusionThis innovative approach offers promise in the management of BPF and signals potential advancements in enhancing treatment efficacy and patient recovery.

Buccal Fat Pad Transplantation for Correction of Asian Upper Eyelid Depression: A Clinical Study.

To investigate the effect of buccal fat pad transplantation in front of the aponeurosis to correct Asian upper eyelid depression. Eighty-five individuals who were treated with buccal fat pad transplantation were recruited for this study. The upper eyelid depression data were collected before and after treatment, and the aesthetic outcomes were assessed using the Global Aesthetic Improvement Scale (GAIS) and the Likert scale. All patients obtained natural-looking eyelids, and the sunken contour deformity improved. The mean preoperative sunken depth was 6.7±1.0 mm (4-12 mm), and the mean sunken depth at the last follow-up was 4.2±0.9 mm (2-6 mm) (P <0.05). The visual analogue scale score was 2.12±1.75 (1-4) in the immediate postoperative period. The GAIS scores were satisfactory (very much improved, 89.4%; much improved, 7.1%; and improved, 3.5%). According to the Likert scale scores, all patients were satisfied with the clinical outcomes (excellent, 87.1%; very good, 9.4%; and good, 3.5%). A 'fair' or 'poor' result was not reported by any patient. Buccal fat pad transplantation corrects upper eyelid depression in a simple, safe, and effective manner and can efficiently fill the depressed portion and restore a beautiful double eyelid. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Coordinate control of basal epithelial cell fate and stem cell maintenance by core EMT transcription factor Zeb1.

Maintenance of undifferentiated, long-lived, and often quiescent stem cells in the basal compartment is important for homeostasis and regeneration of multiple epithelial tissues, but the molecular mechanisms that coordinately control basal cell fate and stem cell quiescence are elusive. Here, we report an epithelium-intrinsic requirement for Zeb1, a core transcriptional inducer of epithelial-to-mesenchymal transition, for mammary epithelial ductal side branching and for basal cell regenerative capacity. Our findings uncover an evolutionarily conserved role of Zeb1 in promoting basal cell fate over luminal differentiation. We show that Zeb1 loss results in increased basal cell proliferation at the expense of quiescence and self-renewal. Moreover, Zeb1 cooperates with YAP to activate Axin2 expression, and inhibition of Wnt signaling partially restores stem cell function to Zeb1-deficient basal cells. Thus, Zeb1 is a transcriptional regulator that maintains both basal cell fate and stem cell quiescence, and it functions in part through suppressing Wnt signaling.

Clinical Study of Applicability of Buccal Fat Pad Transplantation for Reconstruction after Partial Maxillary Resection

Clinical Study of Applicability of Buccal Fat Pad Transplantation for Reconstruction after Partial Maxillary Resection

Reconstruction with Pedicled Buccal Fat-pad Transplantation After Resection of Oral Cancer

Reconstruction with Pedicled Buccal Fat-pad Transplantation After Resection of Oral Cancer

A Novel Mammary Fat Pad Transplantation Technique to Visualize the Vessel Generation of Vascular Endothelial Stem Cells.

Endothelial cells (ECs) are the fundamental building blocks of the vascular architecture and mediate vascular growth and remodeling to ensure proper vessel development and homeostasis. However, studies on endothelial lineage hierarchy remain elusive due to the lack of tools to gain access as well as to directly evaluate their behavior in vivo. To address this shortcoming, a new tissue model to study angiogenesis using the mammary fat pad has been developed. The mammary gland develops mostly in the postnatal stages, including puberty and pregnancy, during which robust epithelium proliferation is accompanied by extensive vascular remodeling. Mammary fat pads provide space, matrix, and rich angiogenic stimuli from the growing mammary epithelium. Furthermore, mammary fat pads are located outside the peritoneal cavity, making them an easily accessible grafting site for assessing the angiogenic potential of exogenous cells. This work also describes an efficient tracing approach using fluorescent reporter mice to specifically label the targeted population of vascular endothelial stem cells (VESCs) in vivo. This lineage tracing method, coupled with subsequent tissue whole-mount microscopy, enable the direct visualization of targeted cells and their descendants, through which the proliferation capability can be quantified and the differentiation commitment can be fate-mapped. Using these methods, a population of bipotent protein C receptor (Procr) expressing VESCs has recently been identified in multiple vascular systems. Procr+ VESCs, giving rise to both new ECs and pericytes, actively contribute to angiogenesis during development, homeostasis, and injury repair. Overall, this manuscript describes a new mammary fat pad transplantation and in vivo lineage tracing techniques that can be used to evaluate the stem cell properties of VESCs.

A Novel Mammary Fat Pad Transplantation Technique to Visualize the Vessel Generation of Vascular Endothelial Stem Cells

Endothelial cells (ECs) are the fundamental building blocks of the vascular architecture and mediate vascular growth and remodeling to ensure proper vessel development and homeostasis. However, studies on endothelial lineage hierarchy remain elusive due to the lack of tools to gain access as well as to directly evaluate their behavior in vivo. To address this shortcoming, a new tissue model to study angiogenesis using the mammary fat pad has been developed. The mammary gland develops mostly in the postnatal stages, including puberty and pregnancy, during which robust epithelium proliferation is accompanied by extensive vascular remodeling. Mammary fat pads provide space, matrix, and rich angiogenic stimuli from the growing mammary epithelium. Furthermore, mammary fat pads are located outside the peritoneal cavity, making them an easily accessible grafting site for assessing the angiogenic potential of exogenous cells. This work also describes an efficient tracing approach using fluorescent reporter mice to specifically label the targeted population of vascular endothelial stem cells (VESCs) in vivo. This lineage tracing method, coupled with subsequent tissue whole-mount microscopy, enable the direct visualization of targeted cells and their descendants, through which the proliferation capability can be quantified and the differentiation commitment can be fate-mapped. Using these methods, a population of bipotent protein C receptor (Procr) expressing VESCs has recently been identified in multiple vascular systems. Procr+ VESCs, giving rise to both new ECs and pericytes, actively contribute to angiogenesis during development, homeostasis, and injury repair. Overall, this manuscript describes a new mammary fat pad transplantation and in vivo lineage tracing techniques that can be used to evaluate the stem cell properties of VESCs.

Establishing estrogen-responsive mouse mammary organoids from single Lgr5+ cells

Recent evidence suggests that mammary cells expressing R-spondin receptor and Wnt pathway regulator Lgr5, regarded as a stem cell marker in multiple tissues, might represent mammary stem cells (MaSCs). Whether L gr5 marks a multipotent subpopulation of Lin-CD24low/medCD49fhigh MaSCs remains controversial. To some extent the differing results reflect different assays used to assess properties of stemness, including lineage tracing in vivo, mammosphere culture, and mammary fat pad transplantation assays. To address this issue directly, we isolated Lgr5+ cells from mammary glands of Lgr5-lacZ mice and established organoids based on principles adapted from studies of Wnt-driven Lgr5+ cell populations in other organs. Mammary organoids were grown from single Lgr5+ mammary cells in Matrigel, the substratum of choice for intestinal organoids, and in a growth factor cocktail containing EGF, Wnt3a and R-spondin, designed to optimally activate the endogenous Wnt signaling program of stem cells. Colonies derived from single Lgr5+ cells manifest at least four distinct cell populations: Lgr5+ and Lgr5- basal cells and c-Kit+ and c-Kit- luminal cells that spontaneously organize into a ductal structure with basal cells around the periphery and luminal cells lining an interior cavity, reminiscent of normal mammary duct structure. Lgr5+ cell-derived organoids were sustainable during prolonged passaging. In contrast, although Lgr5- cells expand into primary colonies, colony-forming efficiency immediately dissipated upon passaging. Furthermore, reproductive hormones induce epithelial cell proliferation resulting in marked increases in lumen diameter accompanied by squamous transdifferentiation. We propose this estrogen-responsive, self-organizing duct-like structure derived from single murine Lgr5+ mammary cells represents a "mini-breast" organoid.

The Cleared Mammary Fat Pad Transplantation Assay for Mammary Epithelial Organogenesis.

Cleared mammary fat pad (MFP) transplantation has been a standard technique for studies of mammary development and cancer for several decades. The mammary gland is comprised of several fundamental components: The epithelial compartment contains basal/myoepithelial cells and luminal cells, and the stromal compartment (called the MFP) contains adipocytes, smooth muscle cells, fibroblasts, and immune cells. In 3- to 4-wk-old female mice, the mammary epithelium is concentrated very close to the nipple and has not yet grown beyond the mammary lymph node to penetrate the bulk of the MFP. This developmental feature provides an anatomical fixed point, and enables one to cut away the portion of the MFP from the nipple to the lymph node, leaving behind the majority of the MFP free of epithelium. The "cleared" MFP can serve as a supportive native microenvironment fully sufficient for the organogenesis of injected donor epithelium. Normal mammary epithelial donor cells will produce histologically and functionally normal mammary ductal epithelium several weeks posttransplant, with the exception that the ducts will not be connected to the nipple. The assay described here provides a powerful platform for assessing the developmental and tumorigenic potential of engineered cells of interest.

A new method for meniscus repair using type I collagen scaffold and infrapatellar fat pad.

The aim of this study was to investigate a new method for meniscal repair by combinative transplantation with type I collagen scaffold and infrapatellar fat pad. Two-mm cylindrical defects at the anterior part of bilateral medial menisci were prepared in nine Japanese white rabbits. The 18 knees were equally divided into three groups: I, no treatment; II, collagen scaffold transplantation; and III, collagen scaffold and infrapatellar fat pad transplantation. Another three rabbits (six knees) underwent sham surgery and served as controls. Rabbits were sacrificed at eight weeks after transplantation. Surface area of the medial meniscus was evaluated using macrophotographs. Ishida score for meniscal regeneration was used for assessment. To evaluate the composition of regenerated tissue, immunohistochemistry was analyzed with anti-type I and anti-type II collagen antibodies, and anti-Ki67 antibody. To investigate the effects of collagen scaffold on human meniscus, cells were isolated from human meniscus and infrapatellar fat pad, and cultured with collagen scaffold for three weeks. After that, gene expression was evaluated by using quantitative real-time polymerase chain reaction. In group I, the meniscus shrank anterior to posterior, and the surface area was significantly less than that of normal meniscus. However, the surface area was maintained in group III. Ishida score and Ki67-positive cell ratio in group III were significantly higher than that in any other group, and staining with type I and type II collagen was similar to that of the control. Expression of matrix metalloproteinase was significantly lower in cocultures of collagen scaffold, meniscus cell, and infrapatellar fat pad cell than in monocultured meniscus cell, and expression of interleukin-1β was not increased. This new method for meniscal repair by combinative transplantation with type I collagen scaffold and infrapatellar fat pad showed meniscal regeneration and potential for suppressing inflammation.

Lineage Tracing in the Mammary Gland Using Cre/lox Technology and Fluorescent Reporter Alleles.

Lineage tracing using Cre/lox technology has become a well-established technique to study the contribution of different (stem) cell populations to organ development and function. When used in the mammary gland, it forms a valuable addition to the already existing experimental toolbox and an important alternative to other readouts measuring stem cell potential, such as the fat pad transplantation assay.Here I describe how to set up and analyze an in vivo lineage tracing experiment using tamoxifen-inducible Cre/lox technology, highlighting the specific challenges that the investigator faces when employing this method and interpreting the results in the mammary gland.

Abstract P5-03-03: Effect of rapamycin on the function and transformation of aged murine mammary stem cells

Abstract Age is the number one risk fact for breast cancer with only 5% of all breast cancers occurring in women under 40 years old and age specific incidence of invasive breast cancer increases from less than 1.5% at age 40, to about 3% at age 50 and over 4% by age 70 in American women. Recent research implicated that adult mammary stem cells (MaSCs) might be responsible for the initiation and progression of certain types of breast cancer. Our preliminary study showed that aging is associated with a significant increase of MaSC frequency, but with a functional decline of self-renewal and differentiation as well as increased neoplastic transformation potential. These findings indicate that aged MaSCs might be the precursors of preneoplastic lesions and serve as the cell of origin for malignant transformation in breast tissue. Therefore, intervention of MaSC aging process could be an effective method for cancer prevention. The drug of rapamycin has been shown to extend life span and ameliorate age-related pathologies (e.g., cancer) in murine models, and a recent study suggested that rapamycin's anti-aging effect may partially act through enhancing the function of tissue-specific stem cells. It is unknown whether rapamycin treatment will also enhance the function of aged MaSCs and decrease their transformation potential. In this study, we fed C57BL/6 mice with microencapsulated rapamycin-containing food (14 mg/kg, food designed to deliver ∼2.24 mg of rapamycin per kg body weight/day to achieve about 4 ng/ml of rapamycin per kg body weight/day) or control diet with empty capsules for 2 year (starting at 2-month old) or 5-10 days (starting at 25.5-month old) and then isolated primary mammary cells at 26-month old for MaSC quantification using an in vitro mammosphere formation and 3D-ECM sphere differentiation assay as well as by the in vivo cleared mammary fat pad transplantation assay. Our findings indicate that short-term (5-10 days) or long-term (&amp;gt; 2 year) rapamycin treatment reversed phenotypic changes associated with aged MaSC, which was mainly characterized by decreased luminal-to-basal cell ratio and increased MaSC frequency. Histological analysis of regenerated glands of aged MaSCs derived from control and rapamycin-treated mice showed a significant decrease of early neoplastic transformation potential in rapamycin-treated group. Subsequent in vivo serial transplantation and mating experiments revealed that rapamycin treatment reverted aged MaSCs more resemble to young MaSCs in self-renewal/differentiation function during regeneration and improved lobulo-alveolar differentiation function for lactation. In conclusion, our findings suggest that rapamycin can rejuvenate the function of aged MaSCs as well as reduce their incidence of preneoplastic transformation. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-03-03.

Abstract B035: Preneoplastic transformation of murine mammary stem cells by aging and inhibition by rapamycin

Abstract The number one risk fact for breast cancer is aging. Recent research implicated that adult mammary stem cells (MaSCs) might be responsible for the initiation and progression of certain types of breast cancer. We tested the hypothesis that aging-associated mammary tumorigenesis may be due to altered number and function of MaSCs using mouse models. MaSC-enriched basal cells, characterized by their immunophenotype (Lin-CD49fhighCD24med), were utilized for the evaluation of MaSC frequency and function during aging by in vitro mammosphere formation and 3D-ECM sphere differentiation assays and by in vivo cleared mammary fat pad transplantation (IVT) as we reported recently (Stem Cell Res. 2013). We found that the basal-to-luminal cell ratios analyzed by FACS and the frequency of MaSCs analyzed with in vitro assays increased steadily with increasing age in various strains of mice. Subsequent IVT using mammosphers or 3D-ECM structures formed by young (4 months) or old (28 months) MaSCs derived from C57BL/6 mice showed similar in vivo functional mammary gland regenerative capacity indicating similar self-renewal/differentiation ability between young and old MaSCs. However, we found that the regenerated glands from old MaSCs had significantly higher number of spontaneous hyperplastic and atypical ductal hyperplastic lesions than those from young MaSCs. These findings indicate that aged MaSCs can serve as the cell of origin for early neoplastic transformation in breast tissue. Because rapamycin treatment has been shown to ameliorate age-related pathologies including cancer in murine models, we fed old C57BL/6 mice with microencapsulated rapamycin-containing food or control diet to determine whether rapamycin treatment can inhibit the aging-associated alteration of MaSC number and function. Our findings indicate that short-term (5-10 days) or long-term (&amp;gt; 2 year) rapamycin treatment reversed phenotypic changes associated with aged mammary gland, which were mainly characterized by decreased luminal-to-basal cell ratio and increased MaSC frequency. Histological analysis of regenerated glands by aged MaSCs derived from control and rapamycin-treated mice showed a significant decrease of early neoplastic lesions in rapamycin-treated group. Subsequent whole genome transcriptome analysis with the second generation sequencing revealed age-associated differential expression of genes involved in immune, inflammatory, and wounding responses in both mammosphere-forming cells and stromal cells suggesting that these may be the main cellular processes contributing to the altered MaSC phenotypes and inhibited by rapamycin. In conclusion, our findings suggest that aging causes MaSC to increase its pool and to form early neoplastic lesions, which can be inhibited by rapamycin treatment. Citation Format: Lu-Zhe Sun, Abhik Bandyopadhyay, Qiaoxiang Dong, Hui Gao, Xiang Gu, Danhan Wang, Anqi Wu, Changjiang Huang. Preneoplastic transformation of murine mammary stem cells by aging and inhibition by rapamycin. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research: Genetics, Biology, and Clinical Applications; Oct 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2013;11(10 Suppl):Abstract nr B035.

Evidence for a multipotent mammary progenitor with pregnancy-specific activity

IntroductionThe mouse mammary gland provides a powerful model system for studying processes involved in epithelial tissue development. Although markers that enrich for mammary stem cells and progenitors have been identified, our understanding of the mammary developmental hierarchy remains incomplete.MethodsWe used the MMTV promoter linked to the reverse tetracycline transactivator to induce H2BGFP expression in the mouse mammary gland. Mammary epithelial cells (MECs) from virgin mice were sorted by flow cytometry for expression of the mammary stem cell/progenitor markers CD24 and CD29, and H2BGFP. Sorted populations were analyzed for in vivo repopulation ability, expression of mammary lineage markers, and differential gene expression.ResultsThe reconstituting activity of CD24+/CD29+ cells in cleared fat pad transplantation assays was not distinguished in GFP+ compared to GFP- subpopulations. However, within the CD24+/CD29lo luminal progenitor-enriched population, H2BGFP+, but not H2BGFP-, MECs formed mammary structures in transplantation assays; moreover, this activity was dramatically enhanced in pregnant recipients. These outgrowths contained luminal and myoepithelial mammary lineages and produced milk, but lacked the capacity for serial transplantation. Transcriptional microarray analysis revealed that H2BGFP+/CD24+/CD29lo MECs are distinct from H2BGFP-/CD24+/CD29lo MECs and enriched for gene expression signatures with both the stem cell (CD24+/CD29+) and luminal progenitor (CD24+/CD29lo/CD61+) compartments.ConclusionsWe have identified a population of MECs containing pregnancy-activated multipotent progenitors that are present in the virgin mammary gland and contribute to the expansion of the mammary gland during pregnancy.

Abstract P5-03-04: Effect of aging on the function and transformation of murine mammary stem cells

Abstract Epidemiological studies have shown that the risk of getting breast cancer progressively increases with age. A woman is 100 times more susceptible to develop breast cancer in her 60s than in her 20s. A better understanding of altered cellular and molecular mechanisms leading to the development of sporadic breast cancers as a result of aging are urgently needed for its prevention and treatment in growing population of older women. Recent research implicated that adult mammary stem cells (MaSCs) might be responsible for the initiation and progression of certain types of breast cancer. But no studies have been reported on how lifelong exposure of MaSCs to endogenous and environmental stresses during aging compromises their self-renewal and differentiation function and predispose them to neoplastic transformation either spontaneously or after carcinogen exposure. In our study, we have investigated the effect of progressive aging and carcinogen exposure on MaSC number and function in a murine model. The FACS isolated MaSC enriched basal cells, characterized by their immunophenotype (Lin−CD49fhighCD24med) were utilized to evaluate MaSC frequency and function during aging by in vitro mammosphere formation and 3D-ECM sphere differentiation assay as well as by in vivo cleared mammary fat pad transplantation (IVT). The results of our study showed that the percentage of MaSCs analyzed by both FACS profile and in vitro assays, increased steadily with increasing age observed at 2, 7, 17 and 25 month-old C57BL/6 mice. Subsequent IVT using mammosphers or 3D structures formed by young (4 months) and old MaSCs (28 months) derived from C57BL/6 mice showed similar in vivo functional mammary gland regenerative capacity indicating similar self-renewal/differentiation ability between young and old MaSCs. However, we found that the regenerated glands from old MaSCs had significantly higher number of spontaneous pre-neoplastic lesions (52.0%) than those from young MaSCs (18.3%). Significantly, MaSC frequency was also increased by the in vivo exposure of a carcinogen, N-Methyl-N-Nitrosourea (MNU, 25 mg/kg body weight, once a week for three consecutive weeks), in old mice with no effect on total mammary cell number. Furthermore, the old MaSCs expanded by MNU treatment were still capable of in vivo regeneration with similar success rate as that of normal old MaSCs. But, we observed increased frequency of hyperplasia and dysplasia in the regenerated glands initiated by MNU treated old MaSC. Our results indicate that MaSCs might be the precursors of preneoplastic lesions and old MaSCs appear to be predisposed to premalignant transformation, which is enhanced by the exposure to a DNA damaging agent. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-03-04.

Who do they think they are? Wnt-responsive cells reveal their family trees

The nature of stem and progenitor cells in the mammary epithelium, and the relevance of cleared fat pad transplantation as a functional assay for them, has been thrown into doubt by recent lineage-tracking studies. Now two new studies based on tracking the progeny of Wnt-responsive cells are starting to help make sense of this fascinating problem.

Expanding Sca-1+ mammary stem cell in the presence of oestrogen and growth hormone

Sca-1 is controversial as a mammary stem cell marker in the literature, which may be due to the different isolation protocols and culture media used in different laboratories. The object of our study is to establish the Medium to promote the proliferation of mammary stem cell and explore the possibility of Sca-1 as mammary stem cell marker. We used BM medium supplemented with different concentration of 17Β-oestradiol and GH to find out MaECM medium which promoted the proliferation of mouse mammary epithelial cells and inhibited the growth of fibroblasts. Flow cytometry was used to isolate Sca-1(+) and Sca-1(-) cell populations from cultured mammary epithelial cells. Mammary fat pad transplantation and Mammosphere- forming assay were done to confirm the stem cell potential of Sca-1(+) cells. Differentiating culture was used to detect the differentiation potential of Sca-1(+) cells. Real-time PCR was carried out to analyse the expression of mammary stem cell-related genes in Sca-1(+) cells. We first selected the medium suitable for mammary stem cell growth. Stem cell medium BM was used to culture mammary organoids, which generated many fibroblasts. We established MaECM medium supplemented with oestrogen and growth hormone (GH), in which oestrogen promoted mammary epithelial cell proliferation and inhibited fibroblast growth, and GH obviously enhanced the effect of oestrogen on mammary epithelial cell proliferation. Flow cytometry showed that 50% of cells were Sca-1(+) under the culture of MaECM medium. We confirmed that Sca-1(+) cells regenerated mammary outgrowths when transplanted in vivo, formed mammospheres in vitro and differentiated into luminal epithelial cells with milk-secreting function and myoepithelial cells under Matrigel culture. Furthermore, gene expression analysis by Real-time PCR revealed that Sca-1(+) cells expressed markedly higher levels of mammary stem cell-related genes in comparison to Sca-1(-) cells. Our research demonstrates that Sca-1(+) mammary stem cells can be more easily isolated when cultured in the presence of oestrogen and GH.

A Mystery Wrapped in an Enigma: Matrigel Enhancement of Mammary Cell Growth and Morphogenesis

The analysis of normal mammary morphogenesis is facilitated by the use of mammary fat pad transplantation. The recent experiments on analysis of normal mammary epithelial stem cell activity rely heavily on this technique. In this review, we discuss the known and unknown attributes of using Matrigel in the injection of the mammary epithelial cell suspension. Matrigel greatly increases the "take" frequency of the injected cell suspension; however, there is some uncertainty regarding the interpretation of some of the results. After consideration of these issues, our conclusion is that Matrigel is important in order to obtain rigorous and reproducible results.

A Study of the Infrapatellar Fat Pad Transplantation to the Excised Articular Surface of the Patellar in Rat

A Study of the Infrapatellar Fat Pad Transplantation to the Excised Articular Surface of the Patellar in Rat

A tissue reconstitution model to study cancer cell‐intrinsic and ‐extrinsic factors in mammary tumourigenesis

The contribution of cancer cell-intrinsic and -extrinsic factors to metastatic breast cancer is still poorly understood, hampering development of novel therapeutic strategies that decrease breast cancer mortality. Cre/loxP-based conditional mouse models of breast cancer present unique opportunities to study sporadic tumour formation and progression in a controlled setting. Unfortunately, the generation of mouse strains carrying multiple mutant alleles needed for such studies is very time-consuming. Moreover, conditional mouse tumour models do not permit independent manipulation of tumour cell-intrinsic and -extrinsic factors. Although the latter can be achieved by cleared fat-pad transplantation of mouse mammary epithelial cells (MMECs) from tumour suppressor gene (TSG) knockouts into wild-type or mutant recipients, this procedure is not possible for mutations that cause embryonic lethality or preclude mammary gland development. Here we show that cleared fat-pad transplantations with MMECs isolated from K14cre;Cdh1(F/F); Trp53(F/F) mice expressing Cre recombinase under control of the cytokeratin-14 promoter and carrying conditional null alleles for p53 and E-cadherin (Cdh1) first resulted in the formation of phenotypically normal mammary glands, followed by the development of invasive metastatic mammary tumours. Tumour formation in the recipients mimicked tumour latency, spectrum, morphology, immunophenotype, and metastatic characteristics of the original mammary tumour model. This transplantation system, which can be expanded to other conditional TSG knockouts, permits independent genetic analysis of stromal factors and testing of additional cancer cell-intrinsic mutations that would otherwise be embryonic lethal or require intensive breeding.