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\title{Mini-organs and early embryos in vitro: what is at stake?}

\alttitle{Mini-organes et embryons pr\'{e}coces \textit{in vitro} : quels enjeux ?}

\author{\firstname{Melina} \lastname{Thetiot}\CDRorcid{0000-0001-7911-6134}\IsCorresp}
\address{Institut Pasteur, Universit\'{e} Paris Cit\'{e}, CNRS UMR3738, Zebrafish Neurogenetics Unit, Department of Developmental and Stem Cell Biology, F-75015 Paris, France}
\email[M. Thetiot]{melina.thetiot@pasteur.fr}

\author{\firstname{Pascale} \lastname{Cossart}\CDRorcid{0000-0001-8871-6780}}
\address{Institut Pasteur, Universit\'{e} Paris Cit\'{e}, Department of Cell Biology and Infection, F-75015 Paris, France}
\email[P. Cossart]{pascale.cossart@pasteur.fr}

\author{\firstname{Laure} \lastname{Bally-Cuif}\CDRorcid{0000-0001-6611-6274}}
\addressSameAs{1}{Institut Pasteur, Universit\'{e} Paris Cit\'{e}, CNRS UMR3738, Zebrafish Neurogenetics Unit, Department of Developmental and Stem Cell Biology, F-75015 Paris, France}
\email[L. Bally-Cuif]{laure.bally-cuif@pasteur.fr}

\shortrunauthors

\keywords{\kwd{Stem cells} 
\kwd{Organoids}
\kwd{Embryoids}
\kwd{Human development}
\kwd{Disease modeling}
\kwd{Ethics in biomedical research}}

\altkeywords{\kwd{Cellules souches}
\kwd{Organo\"{i}des}
\kwd{Embryo\"{i}des}
\kwd{D\'{e}veloppement humain}
\kwd{Mod\'{e}lisation des maladies}
\kwd{\'{E}thique de la recherche biom\'{e}dicale}}

\thanks{French Acad\'{e}mie des Sciences,  
Roux-Cantarini program,  LabEx Revive (ANR-10-LABX-0073).}

\begin{abstract}
Organoids and embryoids are self-organizing 3D cellular models derived
from human pluripotent stem cells or dissociated stem cells from
primary tissue, able of partially mimicking the development and
function of tissues, organs, or embryos in vitro. Research
using these models is advancing rapidly, starting to overcome
challenges in studying human development, evolution, and disease. The
conference from the French Acad\'{e}mie des Sciences ``Mini-organs and
early embryos in vitro: what is at stake?'' illustrated the
promise of organoids and embryoids in basic and translational research.
The lectures emphasized recent biomedical applications, particularly in
disease modeling, drug discovery, and regenerative medicine. Current
challenges and future directions have also been discussed alongside
with the ethical implications of generating functional structures from
human cells in vitro.
\end{abstract}

\begin{altabstract} 
Les organo\"{i}des et les embryo\"{i}des sont des mod\`{e}les
cellulaires tridimensionnels issus de cellules souches humaines,
capables de reproduire partiellement, \textit{in vitro}, le
d\'{e}veloppement et le fonctionnement de tissus, d'organes ou
d'embryons. La recherche utilisant ces mod\`{e}les progresse rapidement
et commence \`{a} surmonter les obstacles li\'{e}s \`{a} l'\'{e}tude du
d\'{e}veloppement, de l'\'{e}volution et des maladies humaines. La
conf\'{e}rence de l'Acad\'{e}mie des Sciences intitul\'{e}e
\guillemotleft{} Mini-organes et embryons pr\'{e}coces \textit{in vitro}
: quels enjeux ? {}\guillemotright{} a illustr\'{e} le potentiel des
organo\"{i}des et des embryo\"{i}des dans la recherche fondamentale et
translationnelle. Les pr\'{e}sentations ont mis en avant des
applications biom\'{e}dicales r\'{e}centes, notamment dans la
mod\'{e}lisation des maladies, la d\'{e}couverte de th\'{e}rapies et la
m\'{e}decine r\'{e}g\'{e}n\'{e}rative. Les d\'{e}fis actuels et les
perspectives futures ont \'{e}galement \'{e}t\'{e} abord\'{e}s, de
m\^{e}me que les implications \'{e}thiques li\'{e}es \`{a} la
g\'{e}n\'{e}ration, \textit{in vitro}, de structures fonctionnelles
\`{a} partir de cellules humaines.
\end{altabstract} 

\maketitle

\end{noXML}

\vspace*{4pt}

\twocolumngrid

\section{Introduction}

Organoid and embryoid research stands at the forefront of biomedical
innovation, offering unprecedented insights into human development and
disease. This rapidly expanding field holds promise for both
fundamental biological discoveries and translational medical
applications. Like a previous Symposium in 2019, co-organized by the
Acad\'{e}mie de M\'{e}decine and the Acad\'{e}mie des Sciences, on the
same topic, the conference ``Mini-organs and early embryos in vitro:
what is at stake?'' from the French Acad\'{e}mie des Sciences, held on
November 12, 2024 in the historical Palais de
l'Institut de France in Paris, aimed to highlight the latest advances
in organoid and embryoid research. Organized by Laure Bally-Cuif and
Pascale Cossart, members of the Acad\'{e}mie des Sciences, the
conference explored organoids and embryoids potential, limitations,
biomedical applications, and inherent ethical considerations.


\begin{figure*}
\includegraphics{fig01}
\caption{From stem cells to complex 3D models. Schema illustrating the
progression from pluri- or multipotent cell types, such as embryonic
stem cells (ESCs), induced pluripotent stem cells (iPSCs), and primary
tissue-derived cells, to self-organizing 3D culture systems known as
organoids or embryoids. These structures mimic biological tissues,
organs, or even whole organisms in terms of complexity and function,
providing advanced models for biomedical research. Created in
\url{https://BioRender.com}.\label{fig1}}
\end{figure*}


Organoids and embryoids are three-dimensional (3D) structures derived
from pluripotent stem cells, such as embryonic stem cells (ESCs) and
induced pluripotent stem cells (iPSCs), as well as from adult stem
cells (ASCs), that self-organize and partially mimic the cellular
complexity, function, and architecture of a tissue, organ, or organism
(Figure~\ref{fig1}). Differentiated skin or blood cells from human patients can
be experimentally reverted to a pluripotent state and then guided
in vitro to generate cells from \mbox{various} organs. Consequently,
organoids have been extensively developed as models for studying human
biology and diseases, encompassing nearly every organ from the
intestine to the brain. Embryoids, a more recent experimental approach,
help study early developmental and implantation stages that are
inaccessible in vivo.



The primary goals of generating organoids and embryoids are to advance
our understanding of fundamental biology by exploring cellular
properties, abnormalities, and diseases. Within this frame, Nathalie
Vergnolle, director of the Digestive Health Research Institute in
Toulouse, France, illustrated how intestinal organoids serve as
powerful models for studying intestinal biology, such as epithelial
regeneration, chronic inflammatory diseases, and drug responses,
emphasizing their potential in precision medicine. Similarly, Botond
Roska, founding Director of the Institute for Molecular and Clinical
Ophthalmology at the University of Basel, Switzerland, highlighted the
use of retinal organoids in developing gene therapies for eye
disorders, and screening protective compounds for photoreceptors. In
the context of neurodevelopmental research, Sandrine Passemard,
Professor in Child Neurology at Universit\'{e} Paris Cit\'{e} and
H\^{o}pital Robert Debr\'{e} in Paris, France, demonstrated how brain
organoids help model disorders such as Coffin-Siris and Timothy
syndromes, revealing key genetic and cellular mechanisms underlying
these conditions.

Beyond their biomedical applications, organoids and embryoids also
provide a unique opportunity to explore the genetic basis of
developmental disorders and early embryogenesis. Denis Duboule,
Professor at EPFL, Lausanne, Switzerland, and Coll\`{e}ge de France,
Paris, France, discussed how embryo models, such as embryoids,
gastruloids, and blastoids, contribute to understanding mammalian
development, fertility, and congenital disorders. As these models
advance in replicating human development and function, the conference
ended by examining the necessity of addressing their ethical and
societal implications. Herv\'{e} Chneiweiss, currently Chair of the
Inserm ethics committee, showcased the HYBRIDA project to emphasize the
importance of harmonizing ethical guidelines, defining clear regulatory
boundaries, and ensuring responsible research practices in organoid
studies.


\section{Intestinal organoids: past, present and\newline future in research and medicine}

Nathalie Vergnolle's presentation focused on the intestine, emphasizing
the regenerative capacity of the intestinal epithelium, which is rich
in stem cells. A key structure, the intestinal crypt, where intestinal
stem cells reside, continuously undergoes proliferation,
differentiation, and apoptosis, leading to the rapid renewal of the
epithelium in less than a week. Since Hans Clevers' pioneering
experiment demonstrating the successful in vitro reproduction
of an intestinal epithelium \citep{Satoetal2009}, further studies have
shown that human colon crypts can form colonospheres, which
subsequently generate colonoids within 10 to 12 days
\citep{dAldebertetal2020}.

Intestinal organoids, derived from non-transformed tissues (including
small biopsies), provide valuable models for studying developmental
biology, cellular organization, and fundamental processes such as
proliferation, differentiation, and cell death. Importantly, they
reproduce key epithelial functions, including secretory, absorptive,
and barrier functions, making them highly relevant for research in both
physiology and pathophysiology. One major pharmacological application
involves the study of protease-activated receptors (PARs), whose
pro-inflammatory and pro-nociceptive effects have been identified
\citep{Vergnolleetal2001,Vergnolleetal1999}. The impact of thrombin on
the intestinal epithelium has also been investigated, leading to the
testing of PAR-1 and PAR-4 antagonists to assess their effects on
epithelial maturation \citep{Sebertetal2018}.

In the field of pathophysiology, organoids serve as models for chronic
inflammatory diseases after treatment with inflammatory cytokines or
deriving organoids directly from patient cells
\citep{dAldebertetal2020}. Notably, organoid cultures from Crohn's
disease or ulcerative colitis patient tissues maintain an inflammatory
phenotype. Observed phenotypic changes in inflammatory disease models
include alterations in organoid size, increased cell death and debris,
and disruptions in polarity and barrier function. Given the role of the
intestinal epithelium in protease secretion, researchers tested a
serine protease inhibitor on diseased organoids, successfully restoring
organoid size, polarity, junctional integrity, and budding formation.
This finding highlights the therapeutic potential of organoid-based
studies. Furthermore, organoid models play a crucial role in drug
screening for therapeutic development, with the ultimate goal of
restoring a healthy epithelial phenotype.

In the context of precision medicine, intestinal organoids offer a
means to overcome patient-specific drug resistance. By testing
treatments such as anti-TNF, methylprednisolone, and 5-ASA on
organoids, researchers can evaluate drug efficacy based on parameters
like size and polarity. One of the most promising applications is in
colorectal cancer, where a strong correlation has been observed between
organoid responses and patient outcomes. In the future, addressing the
time constraint in obtaining results, which currently takes around six
weeks, will be crucial.

Despite their advantages, several challenges remain in intestinal
organoid research. These include improving co-cultures with gut
microbiota, enhancing system complexity through vascularization, and
developing novel techniques such as organ-on-a-chip models. Future
applications for intestinal organoid cultures extend beyond research,
with promising prospects in in vitro clinical trials,
precision medicine approaches, and tissue engraftment for epithelial
regeneration. These advancements are expected to drive rapid progress
in regenerative and precision medicine, further expanding the potential
applications of intestinal organoids.

\section{Developing new therapies using human\newline organoids}

Botond Roska discussed the visual system, highlighting the complex
pathway through which visual information is processed, from images to
the retina, then in the brain to the lateral geniculate nucleus (LGN),
and finally to the cortex. Before transmitting information to higher
visual centers, the retina processes approximately 30 different visual
features, underscoring its critical role in visual perception. However,
studying retinal diseases presents significant challenges due to the
retina's intricate organization, which consists of more than ten
different cell types. Many retinal diseases are cell-type specific,
making animal models inadequate for accurately replicating human
retinal pathologies. A promising alternative is the development of
human retinal organoids derived from iPSCs \citep{Cowanetal2020}, which
facilitate high-throughput research and therapeutic applications.

These organoids have become instrumental in therapy development,
particularly in gene therapy for vision restoration as exemplified by
DNA base editing for Stargardt disease, and drug discovery for
photoreceptor protection. As a prerequisite for human gene therapy,
Botond Roska's team developed AAV-based gene therapy vectors to allow
efficient and long-lasting transgene expression in targeted retinal
cells. This approach improves the efficacy of gene therapies aimed at
restoring visual function \citep{Juttneretal2019}. A particularly
promising application is the development of DNA base editing therapies
for Stargardt disease, a juvenile form of macular degeneration caused
by a G-to-A mutation (c.5882G${>}$A) in the \textit{ABCA4} gene, leading
to foveal degeneration. This novel therapeutic approach has
successfully corrected the mutation in approximately 70\% of
patient-derived retinal organoids \citep{Mulleretal2025}, demonstrating
significant potential for future clinical applications. 

Retinal organoids also play a critical role in identifying compounds
that protect photoreceptors from degeneration, a major cause of vision
loss. Cone cells, in particular, are highly vulnerable under
low-glucose conditions, necessitating therapies that slow down their
deterioration. Researchers have developed a cone-specific labeling
technique to track cone health, and AI-based analysis of
cone-GFP-labeled organoids in 96-well plates enables large-scale
screening, testing up to 15,000 organoids. Promising compounds
identified in primary screenings undergo dose-response assays to assess
their effectiveness in preserving cone function \citep{Spirigetal2023}.

Looking ahead, the field aims to develop a complete eye model that
integrates all retinal components, providing an even more comprehensive
system for studying vision and advancing therapeutic strategies.
Retinal organoids thus represent a transformative tool in ophthalmic
research, bridging the gap between basic science and clinical
applications.


\section{Modelling neurodevelopmental disorders in children using human brain organoids: current progress and challenges}

Since their recent development \citep{Lancasteretal2013}, organoids have
provided crucial insights into brain development, especially on the
fundamental interspecies differences in cortical progenitors. In
humans, basal radial glial cells play a key role in cortical expansion,
a feature that brain organoids have helped to model effectively. Both
guided and non-guided organoids preserve differentiation processes
similar to those of the fetal brain while retaining identical genetic
information (Figure~\ref{fig2}).

\begin{figure*}
\vspace*{-1pt}
\includegraphics{fig02}
\vspace*{-1pt}
\caption{Brain organoids recapitulate the very early stages of human
brain development in vitro, especially neurogenesis. (A)
Guided cortical organoid at day in vitro 32, featuring apical radial
glial cells expressing EMX1 (red), which are located and polarized
similarly to the ventricular zone around the ventricular lumen.
Intermediate progenitors expressing TBR2 (white) are present in the
subventricular zone. Nuclei are stained with DAPI (blue). (B) Guided
cortical organoid at day in vitro 50, showing basal radial glial cells
(HOPX$^{+}$, red), apical radial glial cells (Sox2$^{+}$, green) and
intermediate progenitors (TBR2$^{+}$, white). Scale bar:
$50~\upmu\mathrm{m}$ (A, B). Figure kindly provided by S.
Passemard.\label{fig2}}
\vspace*{-1pt}
\end{figure*}

One of the major challenges in studying neurological diseases is the
difficulty of predicting early pathological events before the onset of
symptoms in patients. Historically, researchers have relied on
phenotypic characterization and animal models to understand disease
mechanisms, but these approaches present limitations. Since the brain
is one of the most~evolutionarily divergent organs across species,
developmental defects in the human brain cannot always be accurately
replicated in animal models, even when major developmental processes
are conserved. The generation of 3D brain organoids from patients'
own skin or blood cells has revolutionized the field by overcoming
these limitations, providing an accessible and physiologically relevant
platform for disease modeling.

Brain organoids have proven particularly valuable in studying
neurodevelopmental disorders, which can have either genetic or acquired
origins. Sandrine Passemard discussed several diseases modeled using
these organoids. In the case of Coffin-Siris Syndrome, the most common
cause is a monoallelic mutation in \textit{ARID1B}, leading to agenesis
of the corpus callosum. In 2024, researchers investigated the role of
SATB2-expressing neurons and found that, contrary to initial
assumptions, the number of these neurons remained constant. However,
they observed a significant reduction in axon formation, which they
attributed to defects in axon guidance genes
\citep{MartinsCostaetal2024}. Timothy Syndrome is caused by a G406R
gain-of-function mutation in \textit{CACNA1C}, leading to prolonged
calcium influx due to delayed inactivation of the Ca$_{\mathrm{v}}$1.2
channel. Studies using cortical organoids show that excitatory neurons
abnormally retain postnatal expression of exon 8a, resulting in
prolonged depolarization. Additionally, more complex organoid models
including ventral telencephalic structures reveal impaired migration of
inhibitory interneurons, linked to increased calcium influx. These
findings highlight how the mutation disrupts both excitatory and
inhibitory neuronal development, affecting overall cortical function
\citep{Bireyetal2022,Bireyetal2017,Pascaetal2011}. This discovery has led
to a therapeutic approach using antisense oligonucleotides targeting
exon 8a, as described in a 2024 study by Chen and Pasca
\citep{Chenetal2024}.


Brain organoids have also been used to study microcephaly, a condition
affecting 2.5\% of births that can result from environmental factors
(including Zika virus infection) or from chromosomal or genetic causes.
Genetic microcephaly was among the earliest neurodevelopmental
disorders modeled using brain organoids \citep{Lancasteretal2013}. A key
cellular defect identified was the premature differentiation of neural
progenitors, a mechanism now under investigation by Sandrine
Passemard's team.

Recent advances in brain organoid technology have led to the
development of assembloid models that integrate different brain
structures or cell types, enabling more sophisticated studies of neural
interactions. These include cortex-microglia assembloids,
cortex-choroid plexus assembloids, and cortex-blood vessel assembloids,
among others. By bridging clinical care and fundamental research, these
organoid models provide a powerful tool for dissecting the molecular
and cellular mechanisms underlying neurodevelopmental disorders. Moving
forward, their continued refinement will contribute to a more
comprehensive understanding of brain development and disease mechanisms
at a higher level of complexity.


\section{The making of embryos}

\vspace*{4pt}

Denis Duboule discussed the significance of developing embryo models to
study mammalian development, recognizing that while fundamental
principles of embryogenesis are shared across species, mammalian
embryos, and notably human embryos, exhibit unique characteristics that
require further investigation. The recent emergence of embryoids,
blastoids or gastruloids, has enabled researchers to~explore early
developmental stages that were \mbox{previously} inaccessible due to ethical
and legal constraints. These models provide invaluable insights into
mechanisms that cannot be analyzed in human embryos, from
pre-implantation to early organogenesis, yet they raise important
scientific and ethical questions regarding their biological status and
potential applications. While these embryo models mimic certain
developmental stages, they are not perfect copies of natural embryos
but rather experimental approaches designed to explore specific aspects
of early development.

The increasing relevance of embryo models is underscored by factors
such as declining fertility rates and the rising average age of
first-time parents, as well as the challenges of studying birth defects
due to the inaccessibility of critical developmental periods. Embryo
models can be classified as either integrated or non-integrated based
on their potential to progress to the fetal stage. Integrated models
aim to reproduce embryonic together with supporting extra-embryonic
tissues, in a coordinated manner, whereas non-integrated models mimic
only specific tissues, organs or anatomical structures of development.

Several types of embryo models have been developed to address specific
research questions.\unskip\break Blastoids are structures that mimic blastocyst
development. Mouse blastoids, first developed by 
\citet{Rivronetal2018}, cannot implant in the uterus, whereas human blastoids,
adapted by Rivron and Kagawa, utilize a permissive system that inhibits
all non-epiblast signals \citep{Kagawaetal2022}. These human blastoids can
implant in uterine mucosa organoids, providing a model for early human
implantation while raising the question of whether such models could
ever progress beyond this stage.

Whole-embryo models offer another avenue for investigating
embryogenesis by integrating essential cell types. Mouse whole-embryo
models require three cell types (epiblast, trophoblast and
extra-embryonic mesoderm cells) \citep{Sozenetal2018,Tarazietal2022},
whereas their human counterparts are more complex, involving a fourth
cell type essential for the formation of extra-embryonic structures
(hypoblast cells), as described by Hanna's team in 2023
\citep{Oldaketal2023}. With mouse embryos having been successfully
cultured for up to eight days \citep{AguileraCastrejonetal2021}, this
advancement raises the question of whether extending human development
in vitro is also feasible.

Non-integrated models, such as gastruloids derived from ESCs or iPSCs,
provide another powerful approach to study early development. Although
gastruloids lack full embryo organization, they allow researchers to
investigate specific developmental processes such as the organization
of the posterior embryonic body plan relative to the anteroposterior,
dorsoventral and mediolateral axes. Martinez Arias' research in 2017
showed that gastruloids primarily develop posterior identity, as
indicated by Mesp1 expression \citep{Turneretal2017}. These models serve as
experimental paradigms, enabling the manipulation of key signaling
pathways such as Bone Morphogenetic Protein using activators and
inhibitors to explore their role in human development.

Ultimately, the choice of an embryo model depends on the specific
research question raised. Some models are more suited for studying
implantation, while others offer insights into later events of cell
differentiation and patterning. However, the rapid expansion of embryo
modeling research places the scientific community in an unusual and
delicate position, as these models challenge conventional definitions
of embryonic identity and raise concerns about their potential future
applications. As research\unskip\break continues, it will be crucial to balance
scientific progress with ethical considerations, ensuring that embryo
models are used responsibly to enhance our understanding of fertility,
birth defects, and early human development.


\section{Organoids: from ethical issues to operational guidelines, the outputs of the\newline HYBRIDA project}

As a developing technology, organoids encounter both regulatory gaps
and excessive regulation, highlighting the need for harmonized
guidelines across EU Member States. Additionally, as these models
become more complex and increasingly resemble human tissues, they also
raise significant ethical concerns. In this context, Herv\'{e}
Chneiweiss provided an overview of the EU-funded HYBRIDA project
(2020--2024; \url{www.hybrida-project.eu}), which aims to
establish operational guidelines for organoid research, promote
research integrity through a responsible code of conduct, and explore
the implications of the living nature of organoids. While organoids are
not fully developed organs, they serve as valuable tools for research
and therapeutic applications. Despite significant advancements in this
field, animal models remain necessary due to the current limitations of
organoid systems.

Within the HYBRIDA project, a Code of Responsible Conduct for
Researchers on Organoids and Related Fields was developed and built
upon the European Code of Conduct for Research Integrity (ECoC) to
ensure reliable and ethical research using organoids. This Code
provides guidance and promotes trust among scientists, evaluators,
ethics committees, and the broader public while emphasizing respect for
both researchers and donors. The approach follows the ``Ethics by
Design'' framework while also integrating the more recent concepts of
Reflexivity, Anticipation, and Deliberation (RAD). Additionally,
HYBRIDA Operational Guidelines (OGL) describes the procedures on good
research practices for organoids. These include MIAOU, which defines
the minimal information required for organoid research; ECHOES, a
checklist for ethical project evaluation; RICOCheck, a tool for ethics
committees to assess compliance; and TRUSTED, a list highlighting the
critical elements of the donation process.~Donors' informed consent
remains a critical component,\unskip\break requiring prior approval with
consideration of future applications. However, ethical questions
persist regarding the withdrawal of consent in long-term research.

One of the key ethical challenges stands around the definition of
organoids. While they model aspects of human organs, they are not
complete organs themselves, leading to ongoing debate \citep{WuFu2024}.
Some organoid structures and integrated embryonic models, possess
developmental potential, raising concerns about their classification.
Ethical discussions also address the possibility of embryonic models
reaching a ``tipping point'' where they become indistinguishable from
human embryos, making it essential to establish clear regulatory
boundaries. Strict prohibitions remain in place against testing any
kind of implantation of an embryonic model in humans. 

Research on neural organoids presents additional ethical complexities.
Studies such as those led by Pasca's team have raised concerns about
the potential for consciousness and self-awareness in brain organoids
\citep{Miuraetal2024,Kimetal2025}. As these models become more
advanced, a holistic and anticipatory ethical approach is required to
navigate the uncertainties surrounding their use in research and
medicine.

\section{Conclusions}

The conference ``Mini-organs and early embryos in vitro: what is at
stake?'' provided a comprehensive overview of some of the latest
advancements in organoid and embryoid research, highlighting their
potential in biomedical applications such as disease modeling, drug
discovery, regenerative medicine, and personalized therapies. The
discussions underscored both the scientific promise and the ethical
challenges associated with these rapidly evolving technologies. From
intestinal and retinal organoids to brain organoids and embryo models,
recent studies illustrate how these models are transforming our
understanding of human development and \mbox{pathology.}

However, as organoid complexity increases, it~becomes imperative to
establish ethical guidelines and regulatory frameworks to ensure
responsible research practices. The insights from the \mbox{HYBRIDA} project,
as well as broader ethical reflections, emphasized the need for a
balance between innovation and ethical responsibility. Moving forward,
interdisciplinary collaboration among scientists, ethicists, and
policymakers will be essential to harness the full potential of
organoids and embryoids while maintaining ethical integrity.

This conference reaffirmed the importance of continued dialogue between
the many players involved, and of research, to navigate the challenges
and opportunities presented by these groundbreaking technologies. As
the field advances, sustained efforts in refining organoid models,
integrating novel methodologies, and addressing ethical concerns will
be crucial to unlocking new therapeutic possibilities and deepening our
understanding of human biology.

\section*{Acknowledgements}

We are grateful to the French Acad\'{e}mie des Sciences for funding
this conference, to Anastasia Gestkoff-Bodin for on-site organization,
and to Antoine Triller, Secr\'{e}taire Perp\'{e}tuel, 
and Alain Fischer, Pr\'{e}sident of the Acad\'{e}mie des Sciences, for
their support. MT was funded by postdoctoral fellowships from
the Roux-Cantarini program and LabEx Revive (ANR-10-LABX-0073).

\CDRGrant[LabEx Revive]{ANR-10-LABX-0073}

\section*{Declaration of interests}

The authors do not work for, advise, own shares in, or receive funds
from any organization that could benefit from this article, and have
declared no affiliations other than their research organizations.

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