Xenobots: Una nueva forma de vida sintética se reproduce por primera vez

Una supercomputadora diseño una nueva versión de los ‘Xenobots' que son capaces de reproducirse solos de una manera nunca antes observada por la ciencia

Un equipo de investigadores estadounidense creó, mediante inteligencia artificial una nueva versión de los ‘Xenobots' -unas máquinas biológicas hechas a base de células de rana- y el resultado fue sorprendente: los nuevos robots orgánicos son capaces de autoreproducirse de una manera jamás observada antes por la ciencia.

Según da cuenta el periodista Omar Kardoudi en El Confidencial, este mismo equipo de investigadores ya había creado en 2020 los ‘Xenobots' 1.0, que fueron los primeros robots 100% orgánicos creados por el hombre. Luego desarrollaron los ‘Xenobots' 2.0, capaces de moverse por su cuenta, organizarse en enjambres, autocurarse y tener memoria. 

Ahora dejaron en manos de un supercomputador el diseño de esta nueva y revolucionaria versión y han publicado los resultados de sus estudios en la revista Proceedings of the National Academy of Sciences.

La base de los ‘Xenobots' son las células embrionarias de la rana Xenopus laevis, que se encuentran en la superficie del animal y que, en circunstancias normales, acaban convirtiéndose en piel. "Estarían situadas en el exterior de un renacuajo, manteniendo alejados a los patógenos y redistribuyendo la mucosidad", asegura el doctor Michael Levin, profesor de biología y director del Allen Discovery Center de la Universidad de Tufts, en EE.UU., que ha sido uno de los creadores de los ‘Xenobots'."Pero los estamos poniendo en un contexto novedoso. Les estamos dando la oportunidad de reimaginar su multicelularidad".

En video: cómo es la nueva vida artificial

Otro de los investigadores de la Universidad de Tufts, el profesor Douglas Blackiston, asegura que la gente ha pensado durante mucho tiempo que hemos visto todas las formas en que la vida puede reproducirse o replicarse. Pero admite que esto es algo que nunca se había observado antes.

"Se trata de células de rana que se replican de una forma muy diferente a como lo hacen las ranas. Ningún animal o planta conocido por la ciencia se replica de esta manera", comenta Sam Kriegman, autor principal del nuevo estudio e investigador posdoctoral en el Centro Allen de Tuft y en el Instituto Wyss de Ingeniería Inspirada Biológicamente de la Universidad de Harvard.

Para encontrar esas nuevas formas de reproducción, los científicos usaron el superordenador de la Universidad de Vermont (UVM) con una inteligencia artificial especializada en evolución biológica para conseguir lo que ellos llaman "réplica cinemática" basada en el movimiento. La IA probó miles de millones de diseños con formas distintas como la de los triángulos, cuadrados, pirámides o estrellas de mar hasta que por fin se decidió por una que recuerda al famoso comecocos.

Estos ‘Xenobots' comecocos nadan por la placa petri recogiendo cientos de células individuales que ensamblan dentro de sus bocas para montar bebés de ‘Xenobot' que en pocos días acabarán moviéndose igual que su progenitor. Estos nuevos ‘Xenobots' pueden hacer lo mismo que sus padres, crear copias de sí mismas que también serán capaces de reproducirse de la misma manera.

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La publicación científica (en inglés): "Autorreplicación cinemática en organismos reconfigurables"

Kinematic self-replication in reconfigurable organisms

View ORCID ProfileSam Kriegman, View ORCID ProfileDouglas Blackiston, View ORCID ProfileMichael Levin, and Josh Bongard

PNAS December 7, 2021 118 (49) e2112672118;https://doi.org/10.1073/pnas.2112672118

  1. Edited by Terrence J. Sejnowski, Salk Institute for Biological Studies, La Jolla, CA, and approved October 22, 2021 (received for review July 9, 2021)

Significance

Almost all organisms replicate by growing and then shedding offspring. Some molecules also replicate, but by moving rather than growing: They find and combine building blocks into self-copies. Here we show that clusters of cells, if freed from a developing organism, can similarly find and combine loose cells into clusters that look and move like they do, and that this ability does not have to be specifically evolved or introduced by genetic manipulation. Finally, we show that artificial intelligence can design clusters that replicate better, and perform useful work as they do so. This suggests that future technologies may, with little outside guidance, become more useful as they spread, and that life harbors surprising behaviors just below the surface, waiting to be uncovered.

Abstract

All living systems perpetuate themselves via growth in or on the body, followed by splitting, budding, or birth. We find that synthetic multicellular assemblies can also replicate kinematically by moving and compressing dissociated cells in their environment into functional self-copies. This form of perpetuation, previously unseen in any organism, arises spontaneously over days rather than evolving over millennia. We also show how artificial intelligence methods can design assemblies that postpone loss of replicative ability and perform useful work as a side effect of replication. This suggests other unique and useful phenotypes can be rapidly reached from wild-type organisms without selection or genetic engineering, thereby broadening our understanding of the conditions under which replication arises, phenotypic plasticity, and how useful replicative machines may be realized.

Like the other necessary abilities life must possess to survive, replication has evolved into many diverse forms: fission, budding, fragmentation, spore formation, vegetative propagation, parthenogenesis, sexual reproduction, hermaphroditism, and viral propagation. These diverse processes however share a common property: all involve growth within or on the body of the organism. In contrast, a non-growth-based form of self-replication dominates at the subcellular level: molecular machines assemble material in their external environment into functional self-copies directly, or in concert with other machines. Such kinematic replication has never been observed at higher levels of biological organization, nor was it known whether multicellular systems were even capable of it.

Despite this lack, organisms do possess deep reservoirs of adaptive potential at all levels of organization, allowing for manual or automated interventions that deflect development toward biological forms and functions different from wild type (1), including the growth and maintenance of organs independent of their host organism (2-4), or unlocking regenerative capacity (5-7). Design, if framed as morphological reconfiguration, can reposition biological tissues or redirect self-organizing processes to new stable forms without recourse to genomic editing or transgenes (8). Recent work has shown that individual, genetically unmodified prospective skin (9) and heart muscle (10) cells, when removed from their native embryonic microenvironments and reassembled, can organize into stable forms and behaviors not exhibited by the organism from which the cells were taken, at any point in its natural life cycle. We show here that if cells are similarly liberated, compressed, and placed among more dissociated cells that serve as feedstock, they can exhibit kinematic self-replication, a behavior not only absent from the donating organism but from every other known plant or animal. Furthermore, replication does not evolve in response to selection pressures, but arises spontaneously over 5 d given appropriate initial and environmental conditions.

Results

Pluripotent stem cells were collected from the animal pole of Xenopus laevis embryos (SI Appendix, Fig. S1A), raised for 24 h in 14°C mild saline solution. These excised cells, if left together as an animal cap (11) (SI Appendix, Fig. S1 A and B) or brought back in contact after dissociation (12) (SI Appendix, Fig. S1 C and D), naturally adhere and differentiate into a spheroid of epidermis covered by ciliated epithelium (13, 14) over 5 d (9) (SI Appendix, section S1 and Fig. 1A). The resulting wild-type reconfigurable organisms move using multiciliated cells present along their surface (which generate flow through the coordinated beating of hair-like projections) and typically follow helical trajectories through an aqueous solution for a period of 10 to 14 d before shedding cells and deteriorating as their maternally provided energy stores are depleted.

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Fig. 1.

Spontaneous kinematic self-replication. (A) Stem cells are removed from early-stage frog blastula, dissociated, and placed in a saline solution, where they cohere into spheres containing 3,000 cells. The spheres develop cilia on their outer surfaces after 3 d. When the resulting mature swarm is placed amid 60,000 dissociated stem cells in a 60-mm-diameter circular dish (B), their collective motion pushes some cells together into piles (C and D), which, if sufficiently large (at least 50 cells), develop into ciliated offspring (E) themselves capable of swimming, and, if provided additional dissociated stem cells (F), build additional offspring. In short, progenitors (p) build offspring (o), which then become progenitors. This process can be disrupted by withholding additional dissociated cells. Under these, the currently best known environmental conditions, the system naturally self-replicates for a maximum of two rounds before halting. The probability of halting () or replicating( 1 ) depends on a temperature range suitable for frog embryos, the concentration of dissociated cells, the number and stochastic behavior of the mature organisms, the viscosity of the solution, the geometry of the dish's surface, and the possibility of contamination. (Scale bars, 500 m.)

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