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Ezra Long
Ezra Long

Tissue Culture History Pdf Download =LINK=

The success of plant biotechnology relies on the fundamental techniques of plant tissue culture. Understanding basic biology of plants is a prerequisite for proper utilization of the plant system or parts thereof. Plant tissue culture helps in providing a basic understanding of physical and chemical requirements of cell, tissue, organ culture, their growth and development. Establishment of cell, tissue and organ culture and regeneration of plantlets under in vitro conditions has opened up new avenues in the area of plant biotechnology.

Tissue Culture History Pdf Download

The source material for primary insect cell line culture is an important consideration. Ovaries were the first insect tissues used throughout the 1960s and 1970s, predominantly with Lepidoptera. Adult female mosquito tissues such as salivary glands or midguts could be used to generate cell lines that would be relevant to specific stages of virus-mosquito interactions that influence in vivo vector competence. For example, cell lines could be used to provide some preliminary information on the susceptibility of midgut or salivary gland cells prior to in vivo transmission studies. Embryos are now commonly used as the source for mosquito cell cultures as they contain cells with the potential to differentiate into larval and adult tissues, resulting in a wide diversity of cell morphologies.

Finally, for the past ten years plant tissue culture has truly exploded and now more than ten thousand people are engaged in this field: International Congress held in July 1982 at Lake Yamanaka, Japan is evidence for this effusive development.

It is well recognized that two-dimensional (2D) cell culture does not provide optimal conditions to reach the complex organization and the specific cellular contacts observed in the mammary gland in vivo. Indeed, once mammary epithelial cells are removed from their native tissue environment and cultured on standard plastic supports, they lose essential interactions with their microenvironment such as the extracellular matrix (ECM), the other cells of the epithelium including myoepithelial cells, or the stroma. As a direct consequence, their phenotype and morphology change and they lose polarity. For milk-secreting mammary epithelial cells, the lack of relevant polarized morphology results in non-functional differentiation [2]. Most certainly, the signals regulating major cellular functions such as proliferation, metabolism, differentiation and apoptosis are lost following disconnection from the native microenvironment. Although mammary epithelial cells can proliferate as monolayers on plastic, they are subsequently unable to produce key milk proteins such as caseins and to maintain native milk secretory activity. It is only when receiving signals from ECM proteins plus hormones (prolactin, growth factors) that structures similar to those observed in vivo and tissue-specific gene expression (e.g., casein genes) occur [3, 4]. From the 70 s, in vitro mouse mammary culture evolved from basic monolayers of cells to complex 3D culture systems considering the importance of the cell polarization and microenvironment. Three-D and organoids cell culture developments made with murine mammary cells have promptly been adapted to human cells for similar research objectives.

Over the past decades, ex vivo 3D culture assays with murine and human cells have been designed to recapitulate ductal invasion and elongation, morphogenic programs of alveologenesis, as well as functional differentiation [5]. With these aims, several proteins of the extracellular matrix such as collagen or laminin, have been tested to coat plastic dishes as a support sheet for seeding the cells. On collagen gels, cells were shown to reorganize and form 3D structures like those observed in vivo and exhibiting milk protein genes expression [6]. In another rodent model, Streuli et al. demonstrated that mammary epithelial cells grown in laminin-rich gels underwent functional differentiation based on the expression of the casein genes [4]. From this period onward, type I collagen and laminin gels have been widely used in 3D culture systems. However, while cells cultured on collagen gels did indeed form a confluent epithelial layer with surface polarization, they showed low secretory and myoepithelial specializations [7]. To overcome this problem, floating collagen gels have been used to grow primary mouse mammary epithelial cells. Briefly, floating gels consisted in detaching the sheet of collagen matrix with attached cells from the plastic support, making floating culture rafts allowing access to the basolateral surface of the cells. With floating gels, intracellular protein synthesis increased to a constant level through 7 days of culture. These hydrogels, however, did not fit certain specific applications such as in vivo tissue implantation assays due to mass loss after sample transplantation. Composite scaffold gels have therefore been developed to overcome these problems. Addition of mucopolysaccharide hyaluronan to collagen is an example of composite gel created to improve scaffold integrity while reducing mass loss (unpublished results cited [8]). Many natural and synthetic polymeric materials have been investigated as alternatives to ECM proteins for 3D cell culture systems but still remain unsuitable for some specific applications [9].

Nearly 30 years ago, solubilized basement membrane preparation extracted from the Engelbreth-Holm-Swarm (EHS) mouse sarcoma (tumors) was developed as a potent hydrogel for the differentiation of functional mammary epithelial cells, due to its enrichment in specific ECM proteins and factors (laminin, collagen IV, and a number of growth factors). These hydrogels or ECM matrices, now well-known as the commercial mouse-sarcoma derived Matrigel and Geltrex, helped to model cell and tissue behaviors observed in normal development such as branching morphogenesis. With in vitro technique mixing 3D scaffolds and different culture media, it has even been demonstrated that the cells reform mammary terminal ductal-like structures with well-oriented luminal and basal cells [10, 11]. As example, Nguyen-Ngoc et al., observed epithelial ductal elongation and bifurcation with myoepithelial coverage when seeding mammary organoids of murine epithelial cells in mixture of Matrigel and collagen gels with growth factors enriched media [10]. Composed of several ECM proteins, Matrigel appeared to be much closer to the physiological reality of the cellular microenvironment. Unfortunately, its inconsistent composition, especially the concentrations of the growth factors and other biologically active components, confers to Matrigel a batch-to-batch variability affecting the reproducibility of experiments. Like collagen, Matrigel is unsuitable for certain experiments. When evaluating the role of mechanical and adhesive inputs on 3D tumor cell growth, invasion, and dissemination, Matrigel rigidity may limit epithelial growth and impair dissemination. Beck et al. in 2013 demonstrated that tumors preferentially disseminate into collagen I but not into Matrigel. As for collagen, they successfully tested addition of synthetic polymer mixtures to define the material properties that could induce dissemination into Matrigel [12]. Some more complex mixtures of stromal and basement membrane proteins exist as Humatrix, a gel containing both basement and non-basement membrane molecules. Due to its composition, this gel exhibits biochemical and biological properties different from those of Matrigel and was mainly used in human cancer studies.

The last few years have seen the organ-on-chip technology oncoming, combining bioengineering and microfluidics to mimic the microstructure, the dynamic mechanical properties and the biochemical functionalities of living organs. This technology consists of designing a bionic cellular system on a microfluidic chip possessing the characteristics of the microfluidic technology at a level of miniaturization. It takes the advantage of controlling precisely multiple parameters such as chemical concentration gradients and fluid flows. Mainly used for studies in humans, numerous tissue models including intestine, liver, lung, tumors and muscle have been developed. To our knowledge, however, only mammary tumor cells such as ductal carcinoma cells were studied in this way [17, 18]. Nevertheless, this technology must be mentioned because it might well represent a future for organoids and 3D cell culture of normal mammary gland cells. In one of the rare studies using organ-on-chip, a microdevice consisting of microchannels separated by a semi-permeable membrane mimicking the basement membrane was designed to recreate the 3D structural organization of the human mammary duct. In this device, which was originally developed for drug screening, breast tumor spheroids were co-cultured with human mammary duct epithelial cells and mammary fibroblast cells, in a continuous flow of culture media [17]. Later, a novel microfluidic system established with an in vitro co-culture model of breast cancer cells and human mammary epithelial cells was designed to study the effects of the anti-cancer drugs Paclitaxel and Tamoxifen on tumor migration [19]. Migration of cancer cells (the MDA-MB-231 cell line) was increased after co-culture with human mammary epithelial cells. Similarly, Gioiella et al. used a microfluidic device to simulate breast cancer on a chip and to mimic the epithelial-stroma interactions that occur in the stroma during the invasion of malignant breast epithelial cells [18]. The chip design includes an interface allowing physical contact between the separated stromal and epithelial tumor tissues. This type of co-culture system, which approximates the physiology of the studied organ, makes it possible to investigate biological and cellular mechanisms, as well as the cellular communication between tissues of different origins. Microfluidics is clearly an innovative and promising approach for drug screening. Although the organ-on-chip technology, which is in its infancy, has so far only been implemented in the field of cancerology, this cell culture system best approximates the scale of tissues and organs. It constitutes a relevant avenue for the future of in vitro culture. 350c69d7ab


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