Mesenchymal stem cells (MSCs), the archetypal multipotent progenitor cells derived in cultures of developed organs, are of unknown identity and native distribution. We have prospectively identified ...perivascular cells, principally pericytes, in multiple human organs including skeletal muscle, pancreas, adipose tissue, and placenta, on CD146, NG2, and PDGF-Rbeta expression and absence of hematopoietic, endothelial, and myogenic cell markers. Perivascular cells purified from skeletal muscle or nonmuscle tissues were myogenic in culture and in vivo. Irrespective of their tissue origin, long-term cultured perivascular cells retained myogenicity; exhibited at the clonal level osteogenic, chondrogenic, and adipogenic potentials; expressed MSC markers; and migrated in a culture model of chemotaxis. Expression of MSC markers was also detected at the surface of native, noncultured perivascular cells. Thus, blood vessel walls harbor a reserve of progenitor cells that may be integral to the origin of the elusive MSCs and other related adult stem cells.
Abstract Current limitations of exogenous scaffolds or extracellular matrix based materials have underlined the need for alternative tissue-engineering solutions. Scaffolds may elicit adverse host ...responses and interfere with direct cell–cell interaction, as well as assembly and alignment of cell-produced ECM. Thus, fabrication techniques for production of scaffold-free engineered tissue constructs have recently emerged. Here we report on a fully biological self-assembly approach, which we implement through a rapid prototyping bioprinting method for scaffold-free small diameter vascular reconstruction. Various vascular cell types, including smooth muscle cells and fibroblasts, were aggregated into discrete units, either multicellular spheroids or cylinders of controllable diameter (300–500 μm). These were printed layer-by-layer concomitantly with agarose rods, used here as a molding template. The post-printing fusion of the discrete units resulted in single- and double-layered small diameter vascular tubes (OD ranging from 0.9 to 2.5 mm). A unique aspect of the method is the ability to engineer vessels of distinct shapes and hierarchical trees that combine tubes of distinct diameters. The technique is quick and easily scalable.
Biofabrication of living structures with desired topology and functionality requires the interdisciplinary effort of practitioners of the physical, life and engineering sciences. Such efforts are ...being undertaken in many laboratories around the world. Numerous approaches are pursued, such as those based on the use of natural or artificial scaffolds, decellularized cadaveric extracellular matrices and, most lately, bioprinting. To be successful in this endeavor, it is crucial to provide in vitro micro-environmental clues for the cells resembling those in the organism. Therefore, scaffolds, populated with differentiated cells or stem cells, of increasing complexity and sophistication are being fabricated. However, no matter how sophisticated scaffolds are, they can cause problems stemming from their degradation, eliciting immunogenic reactions and other a priori unforeseen complications. It is also being realized that ultimately the best approach might be to rely on the self-assembly and self-organizing properties of cells and tissues and the innate regenerative capability of the organism itself, not just simply prepare tissue and organ structures in vitro followed by their implantation. Here we briefly review the different strategies for the fabrication of three-dimensional biological structures, in particular bioprinting. We detail a fully biological, scaffoldless, print-based engineering approach that uses self-assembling multicellular units as bio-ink particles and employs early developmental morphogenetic principles, such as cell sorting and tissue fusion.
Understanding the principles of biological self-assembly is indispensable for developing efficient strategies to build living tissues and organs. We exploit the self-organizing capacity of cells and ...tissues to construct functional living structures of prescribed shape. In our technology, multicellular spheroids (bio-ink particles) are placed into biocompatible environment (bio-paper) by the use of a three-dimensional delivery device (bio-printer). Our approach mimics early morphogenesis and is based on the realization that the genetic control of developmental patterning through self-assembly involves physical mechanisms. Three-dimensional tissue structures are formed through the postprinting fusion of the bio-ink particles, in analogy with early structure-forming processes in the embryo that utilize the apparent liquid-like behavior of tissues composed of motile and adhesive cells. We modeled the process of self-assembly by fusion of bio-ink particles, and employed this novel technology to print extended cellular structures of various shapes. Functionality was tested on cardiac constructs built from embryonic cardiac and endothelial cells. The postprinting self-assembly of bio-ink particles resulted in synchronously beating solid tissue blocks, showing signs of early vascularization, with the endothelial cells organized into vessel-like conduits.
Assessment of suicidal risk is one of the most challenging tasks faced by health professionals, notably in emergency care. We compared telephone suicide risk assessment at prehospital Emergency ...Medical Services Dispatch Center (EMS-DC), with subsequent face-to-face evaluation at Psychiatric Emergency Service (PES), using French national Risk-Urgency-Danger standards (RUD).
Data were collected for all suicidal adult patients (N = 80) who were addressed by EMS-DC to PES between December 2018 and August 2019 and benefited from RUD assessment at both services. Suicidal risk was given a score of 1, 2, 3 or 4, in order of severity.
Mean of the differences between the RUD score at EMS-DC and PES was −0.825 (SD = 1.19), and was found to be significant (p < 0.01). The average time between RUD assessments was 420 min (SD = 448) and was negatively correlated with the difference in the RUD score (r = −0.295, p = 0.008). Associated suicide attempt increased the odds of a decrease in the RUD score (OR = 2.989; 95% CI = 1.141-8.069; p < 0.05).
Telephone evaluation of suicidal risk using RUD at EMS-DC yielded moderately higher scores than those obtained by a subsequent face-to face evaluation at PES, with this difference partially explained by the time between assessments, and by clinical and contextual factors.
With aging population, increase in longevity and decrease in the number of qualified donors, the need to find alternative solutions to current organ replacement methods is rapidly becoming a critical ...issue. Tissue engineering has appeared as a potentially viable solution. Classical tissue engineering is based on culturing cells in scaffolds, artificial extracellular matrix mimics, with the hope that the process leads to tissues and organs, that upon implantation can replace damaged, dysfunctional ones and lead to regeneration. However, building extensive living structures, such as tissues and organs is a task of monumental complexity. A recent approach to aid this endeavor is bioprinting. In this technique bioink particles, minitissues in the particular method to be described, are deposited into the biopaper, the temporary support structure, with the aid of special-purpose three-dimensional printer, the bioprinter. However, contrary to 3D printing of acellular materials, in the case of bioprinting deposition in itself does not lead to the final product. The functional biological structure results from the post-printing maturation, under near physiological conditions in bioreactors, a process that relies on fundamental early developmental processes akin to those used in embryonic morphogenesis and with no counterpart in the case of printing inanimate substance.
With the recent advances in tissue engineering in general and bioprinting in particular, preservation of the biological structures will soon become an indispensable part of the process. Three possible approaches to the preservation of the engineered tissues and organs seem to emerge, depending on their location in the body or the specific method of their preparation. One approach is to establish a depository of ready-to-use, of-the-shelf replacement organs. This will require the same preservation solutions that are currently used or under development for donor organs. In particular, this approach will benefit from efficient ways of storing and managing organs. This in turn would increase the demand for tissue engineered products, lead to increased funding of the field and eventually result in saving more lives or improving the quality of many patients’ lives. Another possible approach is that the postprinting maturation process takes place in vivo, utilizing the body, the ultimate bioreactor. This approach is limited to non-vital organs or cases where the original organ is not yet fully dysfunctional. Here, it is the recipient organism that carries out the preservation function until the engineered structure becomes fully functional. Finally, in case of in vivo bioprinting, the deposition of the cellular material is performed directly in the recipient. This approach is limited to parts of the body that are accessible for printing, such as skin. The latter two solutions are inherent to tissue engineering.
Novel methods of biofabricating functional tissues and organs, based on tissue engineering technologies thus may offer an alternative solution to mitigating the chronic shortage of donor organs including their preservation.
Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 15, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf ...file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Gabor Forgacs. Vita. Includes bibliographical references.
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