Using Lyve1-Cre+ Mice to Visualize Lymphatics for Laser Capture Microdissection

Background: Lymphedema is characterized by limb swelling secondary to lymphatic dysfunction. Lymphedema most frequently develops following breast cancer treatment due to iatrogenic damage of the lymphatics from surgery and radiation. Lymphedema affects 20-40% of breast cancer survivors. There is no cure for this disease. For determination of successful delivery of gene-based therapies, target cells are often isolated and analyzed via real-time PCR. One method to isolate a region of cells within a tissue section is laser capture microdissection (LCM). This process involves outlining the desired regions, which are cut on membrane slides and captured using a laser. Using LCM requires visualization and identification of the target tissue. In the case of lymphedema therapies, the target tissue is lymphatic vasculature. Rationale of Project: While lymphatics can be visualized using immunohistochemistry antibodies specific to lymphatic markers, the process is time consuming and can interfere with RNA levels in the tissue. Another option to visualize lymphatics is to use Lyve1-Cre+ mice. These mice express enhanced green fluorescent protein on lymphatic cells. The purpose of this project is to assess the utility of Lyve1-Cre+ and develop the methodology to capture the lymphatics in the murine tail to enable utilization of this methodology in murine tail model of lymphedema. Methodology Development: Samples of Lyve1-Cre+ mouse tails were harvested. Sections (10µm) were captured on LCM slides and dehydrated. The slides were visualized on the LCM microscope system, lymphatics vessels fluoresced green. They were captured via laser dissection. The captured samples were analyzed for the lymphatic specific genes (Prox1 and Lyve1) via quantitative real-time PCR to determine the purity of capture.

A subcellular cookie cutter for spatial genomics in human tissue

Intracellular heterogeneity contributes significantly to cellular physiology and, in a number of debilitating diseases, cellular pathophysiology. This is greatly influenced by distinct organelle populations and to understand the aetiology of disease it is important to have tools able to isolate and differentially analyse organelles from precise location within tissues. Here we report the development of a subcellular biopsy technology that facilitates the isolation of organelles, such as mitochondria, from human tissue. We compared the subcellular biopsy technology to laser capture microdissection (LCM) that is the state of art technique for the isolation of cells from their surrounding tissues. We demonstrate an operational limit of (>20 micron) for LCM and then, for the first time in human tissue, show that subcellular biopsy can be used to isolate mitochondria beyond this limit.

Laser Capture Microdissection optimization for high-quality RNA in mouse brain tissue

Laser Capture Microdissection (LCM) is a method that allows to select and dissecting specific structures, cell populations, or even single cells from different types of tissue to extract DNA, RNA, or proteins. It is easy to perform and precise, avoiding unwanted signals from irrelevant cells, because gene expression may be affected by a bulk of heterogeneous material in a sample. However, despite its efficiency, several steps can affect the sample RNA integrity. In comparison to DNA, RNA is a much more unstable molecule and represents a challenge in the LCM method. Here we describe an optimized protocol to provide good concentration and high-quality RNA in specific structures, such as Dentate Gyrus and CA1 in the hippocampus, basolateral amygdala and anterior cingulate cortex of mouse brain tissue.

Robust Acquisition of High Resolution Spatial Transcriptomes from Preserved Tissues with Immunofluorescence Based Laser Capture Microdissection

The functioning of tissues is fundamentally dependent upon not only the phenotypes of the constituent cells but also their spatial organization in the tissue. However, obtaining comprehensive transcriptomic data based on established phenotypes while retaining this spatial information has been challenging. Here we present a general and robust method based on immunofluorescence-guided laser capture microdissection (immuno-LCM-RNAseq) to enable acquisition of finely resolved spatial transcriptomes with as few as tens of cells from snap-frozen or RNAlater-treated tissues, overcoming the long-standing problem of significant RNA degradation during this lengthy process. The efficacy of this approach is exemplified by the characterization of differences at the transcript isoform level between cells at the tip versus the main capillary body of the mouse small intestine lacteal. With the extensive repertoire of phenotype-specific antibodies that are presently available, our method provides a powerful means by which spatially resolved cellular states can be delineated in situ with preserved tissues. Moreover, such high quality spatial transcriptomes defined by immuno-markers can be used to compare with clusters obtained from single-cell RNAseq studies of dissociated cells as well as applied to bead-based spatial transcriptomics approaches that require such information a priori for cell identification.

Shape decomposition algorithms for laser capture microdissection

Background In the context of biomarker discovery and molecular characterization of diseases, laser capture microdissection is a highly effective approach to extract disease-specific regions from complex, heterogeneous tissue samples. For the extraction to be successful, these regions have to satisfy certain constraints in size and shape and thus have to be decomposed into feasible fragments. Results We model this problem of constrained shape decomposition as the computation of optimal feasible decompositions of simple polygons. We use a skeleton-based approach and present an algorithmic framework that allows the implementation of various feasibility criteria as well as optimization goals. Motivated by our application, we consider different constraints and examine the resulting fragmentations. We evaluate our algorithm on lung tissue samples in comparison to a heuristic decomposition approach. Our method achieved a success rate of over 95% in the microdissection and tissue yield was increased by 10–30%. Conclusion We present a novel approach for constrained shape decomposition by demonstrating its advantages for the application in the microdissection of tissue samples. In comparison to the previous decomposition approach, the proposed method considerably increases the amount of successfully dissected tissue.

A Systematic Comparison of Protocols for Recovery of High-Quality RNA from Human Islets Extracted by Laser Capture Microdissection v1

The isolation of high-quality RNA from endocrine pancreas sections represents a considerable challenge largely due to the high ribonuclease levels. Laser capture microdissection (LCM) of mammalian islets, in association with RNA extraction protocols, has emerged as a feasible approach to characterizing their genetic and proteomic profiles. However, a validated protocol to obtain highquality RNA from LCM-derived human pancreas specimens that is appropriate for next-generation sequencing analysis is still lacking. In this study, we applied four methods (Picopure extraction kit, Qiazol protocol, Qiazol + Clean-up kit, and RNeasy Microkit + Carrier) to extract RNA from human islets obtained from both non-diabetic individuals and patients with type 2 diabetes who had undergone partial pancreatectomy, as well as handpicked islets from both non-diabetic and diabetic organ donors. The yield and purity of total RNA were determined by 260/280 absorbance using Nanodrop 100 and the RNA integrity number with a bioanalyzer. The results indicated that among the four methods, the RNeasy MicroKit + Carrier (Qiagen) provides the highest yield and purity.

P–289 Progesterone receptor is not downregulated in endometrial epithelial compartment during embryo receptivity phase in assisted reproductive cycles

Study question Is progesterone receptor (PGR) downregulation disrupted within endometrial epithelial compartment, during embryo receptivity phase in assisted reproductive technology (ART) cycles? Summary answer PGR is not downregulated in endometrial epithelial cells from ART cycles during embryo receptivity phase. What is known already Progesterone (P4) promotes the downregulation of its own progesterone receptor (PGR). During the mid-luteal phase, PGR is downregulated in endometrial epithelial cells (EEC), a critical process for embryo implantation. Embryos are unable to attach to the maternal surface when PGR expression is sustained in EEC. Non-physiologic ovarian steroid produced or employed in ART cycles may alter endometrial development compromising its receptivity. Scarce information is available whether PGR is downregulated in EEC from ARTs including ovarian stimulation for in vitro fertilization (IVF) cycles or hormonal endometrial preparation for frozen thawed embryo transfer (HEP-FET). Study design, size, duration Cross sectional study including endometrial samples from fertile women during natural cycle (FNC, n = 23), from infertile women submitted to IVF (n = 19) and from infertile women who underwent mock HEP-FET (n = 35). Samples were obtained between 2018–2019. Sample size was calculated considering a power of 90%, alpha error=0.05, an expected PGR expression of 2 and 0.5 in ART and FNC groups, respectively, having a standard deviation=0.9. At least 9 patients would be necessary in each group. Participants/materials, setting, methods Endometrial samples were obtained during mid-luteal phase scheduled 7 days after ovulation in FNC, 5 days after oocyte retrieval in IVF without embryo transfer or 5 days after P4 supplementation in HEP-FET. Immunohistochemistry was employed to quantify PGR using histologic score (Hscore). PGR mRNA levels were determined by qRT-PCR from EEC dissected by laser capture microdissection. Anova test was used for comparing means of Hscore and mRNA among groups. Statistical significance was established as P < 0.05. Main results and the role of chance No statistical differences were found in demographic characteristics including age, body mass index or endometrial thickness. The PGR expression was reduced in FNC compared to IVF and HP-FET endometria (0.6 ± 0.1, 1.9 ± 0.9 and 2.2 ± 0.9 respectively; P < 0.0001). The PGR mRNA levels from ECC dissected by laser capture microdissection were higher in IVF and HP-ET cycles compared to FNC (10.6 ± 3.1, 13.6 ± 2.3 and 0.8 ± 0.1 respectively; P < 0.0001) corroborating the elevated PGR Hscore in EEC from ART cycles. Limitations, reasons for caution This is a descriptive study reporting failure of PGR downregulation in endometria from ART cycles with vaginal P4 supplementation during the luteal-phase. Whether interference or resistance to P4 signal is the mechanism involved in the failure of PGR down regulation in ART cycles needs to be determined Wider implications of the findings: PGR downregulation within EEC was shown in FNC. The retained PGR expression detected in most ART cycles may interfere with embryo implantation and might explain the restricted pregnancy success. Future studies might reveal whether PGR evaluation in EEC can predict embryo implantation. Trial registration number Not Aplicable