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Coral-Derived Hydroxyapatite-Based Macroporous Bioreactors Initiate the Spontaneous Induction of Bone Formation in Heterotopic Extraskeletal Sites
Published in Ugo Ripamonti, The Geometric Induction of Bone Formation, 2020
The central question in developmental biology, and thus regenerative medicine and tissue engineering alike, is the molecular basis of pattern formation (Reddi 1984; Lander 2007; De Robertis 2008). Developmental strides in understanding tissue induction and morphogenesis eventually discovered morphogenetic soluble molecular signals, or morphogens, that initiate pattern formation, tissue induction and morphogenesis (Turing 1952; Reddi 1984; Reddi 1997; Lander 2007; De Robertis 2008; Kerzberg and Wolpert 2007; Wolpert 1996).
Next Generation Tissue Engineering Strategies by Combination of Organoid Formation and 3D Bioprinting
Published in Naznin Sultana, Sanchita Bandyopadhyay-Ghosh, Chin Fhong Soon, Tissue Engineering Strategies for Organ Regeneration, 2020
Shikha Chawla, Juhi Chakraborty, Sourabh Ghosh
3D Bioprinting has evolved dramatically during the last decade as an approach that is at the crossroad of bioengineering and regenerative medicine. It offers humongous potential to design patient-specific and tissue/organ specific tissue engineered equivalents. The advent of rapid manufacturing technologies associated with the engineering aspect of bioprinting offers precise control over architecture and resolution, which makes this field way ahead of the current tissue engineering and regenerative medicine approaches (Cui et al. 2017). Bioprinting offers the possibility to guide the specific orientation of the encapsulated cells, thus effectively recapitulating the tissue/ organ specific microstructure, which in turn simulates the biological, mechanical and functional properties of the target tissue/organ. The promising potential of the field can be delineated from the fact that even in 2D culture systems micro-patterning based arrangement of cells lead to self-assembled gene expression patterns similar to early embryonic organization events (Warmflash et al. 2014). Morgani et al. reported similar results: mouse pluripotent stem cells cultured on micropatterned surfaces under the influence of specific morphogens could mimic embryonic spatial patterning akin to in vivo regionalized pattering of embryo (Morgani et al. 2018). It would be highly interesting if such approaches can be combined with 3D bioprinting to recapitulate fundamental pattern formation features of developmental stages.
Pancreatic Regeneration
Published in Jean Morisset, Travis E. Solomon, Growth of the Gastrointestinal Tract: Gastrointestinal Hormones and Growth Factors, 2017
Except for the embryonic development of the pancreas, where the influence of extracellular components for regular development has been demonstrated,15 there are no studies of pattern formation in this organ during regeneration. In other experimental systems three major mechanisms are discussed which are responsible for the regulation of pattern formation.
Reflections on doing training for the World Health Organization’s mental health gap action program intervention guide (mhGAP-IG)
Published in International Journal of Mental Health, 2019
The interview data was analyzed using thematic analysis – a diverse set of “theoretically flexible” approaches providing “robust, systematic framework[s] for coding qualitative data” through identifying themes (patterns of meaning) across a dataset (Braun & Clarke, 2014, p. 1–2). The thematic analysis was informed by Braun and Clarke’s (2014) reflexive six-stage process. The data was coded twice (by hand and using software) to enable deep familiarization with the data (key to thematic analysis) and to enable attention to both frequency but also to uniqueness. Identification of themes was an “active process of pattern formation and identification”, in contrast to the assumption that findings exist in the data, waiting to be discovered through analysis (Clarke, Braun, Terry, & Hayfield, 2019, p. 18). This means that researcher interpretation and subjectivity were “integral to the process of analysis” (Clarke et al., 2019, p. 6), which is a “decision-making process” (Elliott, 2018, p. 2850), and not a source of bias to be minimized as might be the case in more positivist research (Braun & Clarke, 2013). To deepen critical reflection and achieve complexity and depth of engagement with the data (Clarke et al., 2019), early findings were discussed at two workshops with invited global mental health specialists.
Exosomes as secondary inductive signals involved in kidney organogenesis
Published in Journal of Extracellular Vesicles, 2018
Mirja Krause, Aleksandra Rak-Raszewska, Florence Naillat, Ulla Saarela, Christina Schmidt, Veli-Pekka Ronkainen, Geneviève Bart, Seppo Ylä-Herttuala, Seppo J. Vainio
The embryonic kidney represents a classic model system that has been used to study the cellular and molecular mechanisms of cell and tissue interactions collectively named as a process of embryonic induction. Inductive interactions occur also later during organogenesis, and in the kidney, for example, these occur between epithelial and mesenchymal tissues [48]. Such molecules that mediate the embryonic inductive interactions and are involved in the associated pattern formation are called the morphogens [48,49]. A wealth of data have been generated that indicate a role for several growth factors in the inductive cell and tissue interactions such as the FGFs, TGF beta/BMP, Hedgehog and Wnt signals [50,51] but whether these serve as morphogens is still debatable. The identification of the exosomes and the data presented herein raise the possibility that the exosomes serve as a novel but apparently evolutionary ancient embryonic signalling system. The embryonic kidney model system derived data presented here confirm that indeed RNA species are transferred in association with the process of embryonic induction, being a universal mechanism in the coordination of morphogenesis. Thus, we can conclude that the exosomes provide a newly identified source of signalling with putative relevance to organogenesis. However, the mechanisms by which exosomes act in nephrogenesis remain to be investigated.
Regeneration of caudal fin in Poecilia latipinna: Insights into the progressive tissue morphogenesis
Published in Organogenesis, 2019
Sonam Patel, Isha Ranadive, Isha Desai, Suresh Balakrishnan
Mammoto and Ingber19 have suggested that a surgical cut disrupts the status quo of the interconnected tissues, which ultimately results in changes of the tensional and traction forces between the cells. Consequently, the elastic connective tissue is pulled away from the amputation plane, while epidermal cells are pushed beyond the wound surface towards the lost tissue part.12 This suggests the initiation of wound healing which is accomplished by 1 dpa with covering the wound surface by epithelial cells. Within 2 dpa, the WE thickens and it grows approximately 134.11 μm from the amputation plane and forms a structure called AEC. Nechiporuk and Keating16 have observed that the tissue, proximal to amputation plane begins to disorganize and the mesenchymal cells appear to move towards AEC. A distinctive bulge of proliferating cells called BL can be observed at 3 dpa. After the establishment of an interactive WE and BL, cell proliferation takes place very rapidly leading to increase in the size of the regenerate accompanied by pattern formation.12 This has been observed in our morphometry results showing maximum growth rate for 0–5 dpa interval. Hence, BrdU staining was performed to have a closer look at the cell proliferation happening in the regenerating caudal fin. Whole mount BrdU staining of the caudal fin at 1 dpa revealed that most of the proliferating cells were localized at the WE. Similar observations were made in zebrafish with BrdU staining at 1 dpa by Poleo et al.14 As the fin grows, the number of proliferating cells decreases, marking the onset of differentiation which can be seen in the BrdU staining for 4 dpa and 5 dpa. Although the cells lying proximal to the amputation plane start differentiating at 4 dpa, no defined structure can be seen at that point of time. The differentiation of the proliferating blastemal cells into lepidotrichia and actinotrichia can be observed for the first time in the tail tissues of 5 dpa stained with alcian blue-alizarin red. Similar observations were made by Konig et al.20 for adult zebrafish fin regeneration at 5 dpa.