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Beltrán-Rivera A, García-Arrarás JE. Cellular dedifferentiation. Revisiting Betty Hay's legacy. Dev Biol 2025; 523:1-8. [PMID: 40164323 DOI: 10.1016/j.ydbio.2025.03.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2024] [Revised: 03/25/2025] [Accepted: 03/28/2025] [Indexed: 04/02/2025]
Abstract
The concept of mature specialized cells and the stability of the differentiated state was fundamentally challenged by Elizabeth Hay's groundbreaking observations on amphibian limb regeneration, published in 1959. Building on previous work by C.S. Thornton, she discovered that muscle cells could dedifferentiate and transform into progenitor cells within the regeneration blastema reshaping our understanding of cell differentiation. This pivotal finding reshaped our understanding of cell differentiation, opening new avenues of research. Though controversial, her findings significantly advanced the fields of cell plasticity and regenerative biology.
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Chuong CM, Wu P, Yu Z, Liang YC, Widelitz RB. Organizational principles of integumentary organs: Maximizing variations for effective adaptation. Dev Biol 2025; 522:171-195. [PMID: 40113027 DOI: 10.1016/j.ydbio.2025.03.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2024] [Revised: 03/16/2025] [Accepted: 03/17/2025] [Indexed: 03/22/2025]
Abstract
The integument serves as the interface between an organism and its environment. It primarily comprises ectoderm-derived epithelium and mesenchyme derived from various embryonic sources. These integumentary organs serve as a barrier defining the physiological boundary between the internal and exterior environments and fulfill diverse functions. How does the integument generate such a large diversity? Here, we attempt to decipher the organizational principles. We focus on amniotes and use appendage follicles as the primary examples. The integument begins as a simple planar sheet of coupled epithelial and mesenchymal cells, then becomes more complex through the following patterning processes. 1) De novo Turing periodic patterning process: This process converts the integument into multiple skin appendage units. 2) Adaptive patterning process: Dermal muscle, blood vessels, adipose tissue, and other components are assembled and organized around appendage follicles when present. 3) Cyclic renewal: Skin appendage follicles contain stem cells and their niches, enabling physiological molting and regeneration in the adult animal. 4) Spatial variations: Multiple appendage units allow modulation of shape, size, keratin types, and color patterns of feathers and hairs across the animal's surface. 5) Temporal phenotypic plasticity: Cyclic renewal permits temporal transition of appendage phenotypes, i.e. regulatory patterning or integumentary metamorphosis, throughout an animal's lifetime. The diversities in (4) and (5) can be generated epigenetically within the same animal. Over the evolutionary timescale, different species can modulate the number, size, and distributions of existing ectodermal organs in the context of micro-evolution, allowing effective adaptation to new climates as seen in the variation of hair length among mammals. Novel ectodermal organs can also emerge in the context of macro-evolution, enabling animals to explore new ecological niches, as seen in the emergence of feathers on dinosaurs. These principles demonstrate how multi-scale organ adaption in the amniotes can maximize diverse and flexible integumentary organ phenotypes, producing a vast repertoire for natural selection and thereby providing effective adaptation and evolutionary advantages.
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Affiliation(s)
- Cheng Ming Chuong
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA.
| | - Ping Wu
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA
| | - Zhou Yu
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA
| | - Ya-Chen Liang
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA
| | - Randall B Widelitz
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA
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Nam J, Min B, Baek A, Lee SY, Ha J, Cho MJ, Kim J. Mammalian Blastema: Possibility and Potentials. Int J Stem Cells 2025; 18:126-134. [PMID: 40059074 PMCID: PMC12122245 DOI: 10.15283/ijsc24121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2024] [Revised: 11/26/2024] [Accepted: 11/26/2024] [Indexed: 06/02/2025] Open
Abstract
Regeneration is a process that restores the structure and function of injured tissues or organs. Regenerative capacities vary significantly across species, with amphibians and fish demonstrating a high regenerative capacity even after severe injuries. This capacity is largely attributed to the formation of a blastema, a mass of multipotent cells reprogrammed from differentiated cells at the injury site. In contrast, mammals exhibit limited regenerative capacities, with blastema- like cells forming only in specific contexts, such as antler or digit tip regeneration. An interesting aspect of blastema formation in highly regenerative organisms is the temporary expression of pluripotency factors as known as the Yamanaka factors (YFs), which is a key requirement for reprogramming somatic cells into induced pluripotent stem cells (iPSCs). While iPSCs hold pros and cons, direct or partial reprogramming with YF has been proposed as a safer alternative. Since blastema formation and partial reprogramming are similar in terms of YF expressions, we found blastema-like cells in mammalian reprogramming with YF. This review outlines the characteristics of blastema across various organisms, emphasizing interspecies differences. We also explore studies on partial reprogramming and the possibility of inducing blastema-like cells via the temporary expression of YF in mammals.
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Affiliation(s)
- Juhyeon Nam
- Center for Gene and Cell therapy, Korea Research Institute Bioscience and Biotechnology (KRIBB), Daejeon, Korea
- Department of Functional Genomics, KRIBB School of Bioscience, Korea University of Science & Technology, Daejeon, Korea
| | - Byungkuk Min
- Center for Gene and Cell therapy, Korea Research Institute Bioscience and Biotechnology (KRIBB), Daejeon, Korea
| | - Areum Baek
- Center for Gene and Cell therapy, Korea Research Institute Bioscience and Biotechnology (KRIBB), Daejeon, Korea
- Stem Cell Convergence Research Center, KRIBB, Daejeon, Korea
| | - Sang-Yun Lee
- Center for Gene and Cell therapy, Korea Research Institute Bioscience and Biotechnology (KRIBB), Daejeon, Korea
| | - Jeongmin Ha
- Stem Cell Convergence Research Center, KRIBB, Daejeon, Korea
| | - Min Ji Cho
- Center for Gene and Cell therapy, Korea Research Institute Bioscience and Biotechnology (KRIBB), Daejeon, Korea
- Stem Cell Convergence Research Center, KRIBB, Daejeon, Korea
| | - Janghwan Kim
- Center for Gene and Cell therapy, Korea Research Institute Bioscience and Biotechnology (KRIBB), Daejeon, Korea
- Department of Functional Genomics, KRIBB School of Bioscience, Korea University of Science & Technology, Daejeon, Korea
- Stem Cell Convergence Research Center, KRIBB, Daejeon, Korea
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Tajer B, Savage AM, Whited JL. The salamander blastema within the broader context of metazoan regeneration. Front Cell Dev Biol 2023; 11:1206157. [PMID: 37635872 PMCID: PMC10450636 DOI: 10.3389/fcell.2023.1206157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Accepted: 07/26/2023] [Indexed: 08/29/2023] Open
Abstract
Throughout the animal kingdom regenerative ability varies greatly from species to species, and even tissue to tissue within the same organism. The sheer diversity of structures and mechanisms renders a thorough comparison of molecular processes truly daunting. Are "blastemas" found in organisms as distantly related as planarians and axolotls derived from the same ancestral process, or did they arise convergently and independently? Is a mouse digit tip blastema orthologous to a salamander limb blastema? In other fields, the thorough characterization of a reference model has greatly facilitated these comparisons. For example, the amphibian Spemann-Mangold organizer has served as an amazingly useful comparative template within the field of developmental biology, allowing researchers to draw analogies between distantly related species, and developmental processes which are superficially quite different. The salamander limb blastema may serve as the best starting point for a comparative analysis of regeneration, as it has been characterized by over 200 years of research and is supported by a growing arsenal of molecular tools. The anatomical and evolutionary closeness of the salamander and human limb also add value from a translational and therapeutic standpoint. Tracing the evolutionary origins of the salamander blastema, and its relatedness to other regenerative processes throughout the animal kingdom, will both enhance our basic biological understanding of regeneration and inform our selection of regenerative model systems.
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Affiliation(s)
| | | | - Jessica L. Whited
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA, United States
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Jou V, Lehoczky JA. Toeing the line between regeneration and fibrosis. Front Cell Dev Biol 2023; 11:1217185. [PMID: 37325560 PMCID: PMC10267333 DOI: 10.3389/fcell.2023.1217185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 05/23/2023] [Indexed: 06/17/2023] Open
Abstract
Understanding the remarkable capacity of vertebrates to naturally regenerate injured body parts has great importance for potential translation into human therapeutic applications. As compared to other vertebrates, mammals have low regenerative capacity for composite tissues like the limb. However, some primates and rodents can regenerate the distal tips of their digits following amputation, indicating that at least very distal mammalian limb tissues are competent for innate regeneration. It follows that successful digit tip regenerative outcome is highly dependent on the location of the amputation; those proximal to the position of the nail organ do not regenerate and result in fibrosis. This distal regeneration versus proximal fibrosis duality of the mouse digit tip serves as a powerful model to investigate the driving factors in determining each process. In this review, we present the current understanding of distal digit tip regeneration in the context of cellular heterogeneity and the potential for different cell types to function as progenitor cells, in pro-regenerative signaling, or in moderating fibrosis. We then go on to discuss these themes in the context of what is known about proximal digit fibrosis, towards generating hypotheses for these distinct healing processes in the distal and proximal mouse digit.
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Affiliation(s)
- Vivian Jou
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, United States
- Department of Orthopedic Surgery, Brigham and Women’s Hospital, Boston, MA, United States
| | - Jessica A. Lehoczky
- Department of Orthopedic Surgery, Brigham and Women’s Hospital, Boston, MA, United States
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Castilla-Ibeas A, Zdral S, Galán L, Haro E, Allou L, Campa VM, Icardo JM, Mundlos S, Oberg KC, Ros MA. Failure of digit tip regeneration in the absence of Lmx1b suggests Lmx1b functions disparate from dorsoventral polarity. Cell Rep 2023; 42:111975. [PMID: 36641754 DOI: 10.1016/j.celrep.2022.111975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 11/07/2022] [Accepted: 12/22/2022] [Indexed: 01/15/2023] Open
Abstract
Mammalian digit tip regeneration is linked to the presence of nail tissue, but a nail-explicit model is missing. Here, we report that nail-less double-ventral digits of ΔLARM1/2 mutants that lack limb-specific Lmx1b enhancers fail to regenerate. To separate the nail's effect from the lack of dorsoventral (DV) polarity, we also interrogate double-dorsal double-nail digits and show that they regenerate. Thus, DV polarity is not a prerequisite for regeneration, and the nail requirement is supported. Transcriptomic comparison between wild-type and non-regenerative ΔLARM1/2 mutant blastemas reveals differential upregulation of vascularization and connective tissue functional signatures in wild type versus upregulation of inflammation in the mutant. These results, together with the finding of Lmx1b expression in the postnatal dorsal dermis underneath the nail and uniformly in the regenerative blastema, open the possibility of additional Lmx1b roles in digit tip regeneration, in addition to the indirect effect of mediating the formation of the nail.
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Affiliation(s)
- Alejandro Castilla-Ibeas
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC; CSIC-SODERCAN-UC), Santander, Spain
| | - Sofía Zdral
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC; CSIC-SODERCAN-UC), Santander, Spain
| | - Laura Galán
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC; CSIC-SODERCAN-UC), Santander, Spain
| | - Endika Haro
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC; CSIC-SODERCAN-UC), Santander, Spain
| | - Lila Allou
- RG Development & Disease, Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Víctor M Campa
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC; CSIC-SODERCAN-UC), Santander, Spain
| | - Jose M Icardo
- Departamento de Anatomía y Biología Celular, Universidad de Cantabria, Santander, Spain
| | - Stefan Mundlos
- RG Development & Disease, Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Kerby C Oberg
- Department of Pathology and Human Anatomy, School of Medicine, Loma Linda University, Loma Linda, CA, USA
| | - Marian A Ros
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC; CSIC-SODERCAN-UC), Santander, Spain.
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Johnson GL, Glasser MB, Charles JF, Duryea J, Lehoczky JA. En1 and Lmx1b do not recapitulate embryonic dorsal-ventral limb patterning functions during mouse digit tip regeneration. Cell Rep 2022; 41:111701. [PMID: 36417876 PMCID: PMC9727699 DOI: 10.1016/j.celrep.2022.111701] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Revised: 09/09/2022] [Accepted: 10/31/2022] [Indexed: 11/23/2022] Open
Abstract
The mouse digit tip regenerates following amputation. How the regenerate is patterned is unknown, but a long-standing hypothesis proposes developmental patterning mechanisms are re-used during regeneration. The digit tip bone exhibits dorsal-ventral (DV) polarity, so we focus on En1 and Lmx1b, two factors necessary for DV patterning during limb development. We investigate whether they are re-expressed during regeneration in a developmental-like pattern and whether they direct DV morphology of the regenerate. We find that both En1 and Lmx1b are expressed in the regenerating digit tip epithelium and mesenchyme, respectively, but without DV polarity. Conditional genetics and quantitative analysis of digit tip bone morphology determine that genetic deletion of En1 or Lmx1b in adult digit tip regeneration modestly reduces bone regeneration but does not affect DV patterning. Collectively, our data suggest that, while En1 and Lmx1b are re-expressed during mouse digit tip regeneration, they do not define the DV axis during regeneration.
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Affiliation(s)
- Gemma L. Johnson
- Department of Orthopedic Surgery, Brigham and Women’s Hospital, Boston, MA 02115, USA,Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Morgan B. Glasser
- Department of Orthopedic Surgery, Brigham and Women’s Hospital, Boston, MA 02115, USA
| | - Julia F. Charles
- Department of Orthopedic Surgery, Brigham and Women’s Hospital, Boston, MA 02115, USA,Department of Medicine, Brigham and Women’s Hospital, Boston, MA 02115, USA
| | - Jeffrey Duryea
- Department of Radiology, Brigham and Women’s Hospital, Boston, MA 02115, USA
| | - Jessica A. Lehoczky
- Department of Orthopedic Surgery, Brigham and Women’s Hospital, Boston, MA 02115, USA,Lead contact,Correspondence:
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Tower RJ, Busse E, Jaramillo J, Lacey M, Hoffseth K, Guntur AR, Simkin J, Sammarco MC. Spatial transcriptomics reveals metabolic changes underly age-dependent declines in digit regeneration. eLife 2022; 11:71542. [PMID: 35616636 PMCID: PMC9135401 DOI: 10.7554/elife.71542] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 05/18/2022] [Indexed: 12/12/2022] Open
Abstract
De novo limb regeneration after amputation is restricted in mammals to the distal digit tip. Central to this regenerative process is the blastema, a heterogeneous population of lineage-restricted, dedifferentiated cells that ultimately orchestrates regeneration of the amputated bone and surrounding soft tissue. To investigate skeletal regeneration, we made use of spatial transcriptomics to characterize the transcriptional profile specifically within the blastema. Using this technique, we generated a gene signature with high specificity for the blastema in both our spatial data, as well as other previously published single-cell RNA-sequencing transcriptomic studies. To elucidate potential mechanisms distinguishing regenerative from non-regenerative healing, we applied spatial transcriptomics to an aging model. Consistent with other forms of repair, our digit amputation mouse model showed a significant impairment in regeneration in aged mice. Contrasting young and aged mice, spatial analysis revealed a metabolic shift in aged blastema associated with an increased bioenergetic requirement. This enhanced metabolic turnover was associated with increased hypoxia and angiogenic signaling, leading to excessive vascularization and altered regenerated bone architecture in aged mice. Administration of the metabolite oxaloacetate decreased the oxygen consumption rate of the aged blastema and increased WNT signaling, leading to enhanced in vivo bone regeneration. Thus, targeting cell metabolism may be a promising strategy to mitigate aging-induced declines in tissue regeneration.
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Affiliation(s)
- Robert J Tower
- Department of Orthopaedics, Johns Hopkins University, Baltimore, United States
| | - Emily Busse
- Department of Surgery, Tulane School of Medicine, New Orleans, United States
| | - Josue Jaramillo
- Department of Surgery, Tulane School of Medicine, New Orleans, United States
| | - Michelle Lacey
- Department of Mathematics, Tulane University, New Orleans, United States
| | - Kevin Hoffseth
- Department of Biological & Agricultural Engineering, Louisiana State University, Baton Rouge, United States
| | - Anyonya R Guntur
- Center for Molecular Medicine, Maine Medical Center Research Institute, Scarborough, United States
| | - Jennifer Simkin
- Department of Orthopaedic Surgery, Louisiana State University Health Sciences Center, New Orleans, United States
| | - Mimi C Sammarco
- Department of Surgery, Tulane School of Medicine, New Orleans, United States
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