Lens Regeneration: The Application of iSyTE and In Silico Approaches to Evaluate Gene Expression in Lens Organoids.

Several protocols have been established for the generation of lens organoids from embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and other cells with regenerative potential in humans or various animal models. It is important to examine how well the regenerated lens organoids reflect lens biology, in terms of its development, homeostasis, and aging. Toward this goal, the iSyTE database (integrated Systems Tool for Eye gene discovery; https://research.bioinformatics.udel.edu/iSyTE/ ), a bioinformatics resource tool that contains meta-analyzed gene expression data in wild-type lens across different embryonic, postnatal, and adult stages, can serve as a resource for comparative analysis. This article outlines the approaches toward effective use of iSyTE to gain insights into normal gene expression in the mouse lens, enriched expression in the lens, and differential gene expression in select mouse gene-perturbation cataract/lens defects models, which in turn can be used to evaluate expression of key lens-relevant genes in lens organoids by transcriptomics (e.g., RNA-sequencing (RNA-seq), microarrays, etc.) or other downstream methods (e.g., RT-qPCR, etc.).

Experimental Framework for Assessing Mouse Retinal Regeneration Through Single-Cell RNA-Sequencing.

Retinal degenerative diseases including age-related macular degeneration and glaucoma are estimated to currently affect more than 14 million people in the United States, with an increased prevalence of retinal degenerations in aged individuals. An expanding aged population who are living longer forecasts an increased prevalence and economic burden of visual impairments. Improvements to visual health and treatment paradigms for progressive retinal degenerations slow vision loss. However, current treatments fail to remedy the root cause of visual impairments caused by retinal degenerations-loss of retinal neurons. Stimulation of retinal regeneration from endogenous cellular sources presents an exciting treatment avenue for replacement of lost retinal cells. In multiple species including zebrafish and Xenopus, Müller glial cells maintain a highly efficient regenerative ability to reconstitute lost cells throughout the organism's lifespan, highlighting potential therapeutic avenues for stimulation of retinal regeneration in humans. Here, we describe how the application of single-cell RNA-sequencing (scRNA-seq) has enhanced our understanding of Müller glial cell-derived retinal regeneration, including the characterization of gene regulatory networks that facilitate/inhibit regenerative responses. Additionally, we provide a validated experimental framework for cellular preparation of mouse retinal cells as input into scRNA-seq experiments, including insights into experimental design and analyses of resulting data.

Trabecular Meshwork Regeneration for Glaucoma Treatment Using Stem Cell-Derived Trophic Factors.

Glaucoma is one of the leading causes of irreversible blindness. Stem cell therapy has shown promise in the treatment of primary open-angle glaucoma in animal models. Stem cell-free therapy using stem cell-derived trophic factors might be in demand in patients with high-risk conditions or religious restrictions. In this chapter, we describe methods for trabecular meshwork stem cell (TMSC) cultivation, secretome harvesting, and protein isolation, as well as assays to ensure the health of TMSC post-secretome harvesting and for secretome periocular injection into mice for therapeutic purposes.

Isolation and Characterization of Extracellular Vesicles to Activate Retina Regeneration.

Mammals do not possess the ability to spontaneously repair or regenerate damaged retinal tissue. In contrast to teleost fish which are capable of retina regeneration through the action of Müller glia, mammals undergo a process of reactive gliosis and scarring that inhibits replacement of lost neurons. Thus, it is important to discover novel methods for stimulating mammalian Müller glia to dedifferentiate and produce progenitor cells that can replace lost retinal neurons. Inducing an endogenous regenerative pathway mediated by Müller glia would provide an attractive alternative to stem cell injections or gene therapy approaches. Extracellular vesicles (EVs) are now recognized to serve as a novel form of cell-cell communication through the transfer of cargo from donor to recipient cells or by the activation of signaling cascades in recipient cells. EVs have been shown to promote proliferation and regeneration raising the possibility that delivery of EVs could be a viable treatment for visual disorders. Here, we provide protocols to isolate EVs for use in retina regeneration experiments.

Automated In Vivo Phenotypic Screening Platform for Identifying Factors that Affect Cell Regeneration Kinetics.

Various strategies for replacing retinal neurons lost in degenerative diseases are under investigation, including stimulating the endogenous regenerative capacity of Müller Glia (MG) as injury-inducible retinal stem cells. Inherently regenerative species, such as zebrafish, have provided key insights into mechanisms regulating MG dedifferentiation to a stem-like state and the proliferation of MG and MG-derived progenitor cells (MGPCs). Interestingly, promoting MG/MGPC proliferation is not sufficient for regeneration, yet mechanistic studies are often focused on this measure. To fully account for the regenerative process, and facilitate screens for factors regulating cell regeneration, an assay for quantifying cell replacement is required. Accordingly, we adapted an automated reporter-assisted phenotypic screening platform to quantify the pace of cellular regeneration kinetics following selective cell ablation in larval zebrafish. Here, we detail a method for using this approach to identify chemicals and genes that control the rate of retinal cell regeneration following selective retinal cell ablation.

Controlled Release of Molecules to Enhance Cell Survival and Regeneration.

Controlled release or controlled drug delivery comprises the set of techniques and approaches to improve bioavailability through improved safety and/or efficacy using a carrier material for the molecule of interest. The predictability and tunability of these carriers make them ideal for protection, localization, and sustained presentation of a wide range of therapeutics, including growth factors implicated in cell survival and regeneration. Here we provide a method for encapsulating epidermal growth factor in a degradable polymer matrix for delivery to the cornea. Additional notes are included to demonstrate the wide-ranging capabilities of such methods for other materials, therapeutic agents, and sites of action within the eye.

Efficiently directing differentiation and homing of mesenchymal stem cells to boost cartilage repair in osteoarthritis via a nanoparticle and peptide dual-engineering strategy.

Mesenchymal stem cells (MSCs) are expected to be useful therapeutics in osteoarthritis (OA), the most common joint disorder characterized by cartilage degradation. However, evidence is limited with regard to cartilage repair in clinical trials because of the uncontrolled differentiation and weak cartilage-targeting ability of MSCs after injection. To overcome these drawbacks, here we synthesized CuO@MSN nanoparticles (NPs) to deliver Sox9 plasmid DNA (favoring chondrogenesis) and recombinant protein Bmp7 (inhibiting hypertrophy). After taking up CuO@MSN/Sox9/Bmp7 (CSB NPs), the expressions of chondrogenic markers were enhanced while hypertrophic markers were decreased in response to these CSB-engineered MSCs. Moreover, a cartilage-targeted peptide (designated as peptide W) was conjugated onto the surface of MSCs via a click chemistry reaction, thereby prolonging the residence time of MSCs in both the knee joint cavity of mice and human-derived cartilage. In a surgery-induced OA mouse model, the NP and peptide dual-modified W-CSB-MSCs showed an enhancing therapeutic effect on cartilage repair in knee joints compared with other engineered MSCs after intra-articular injection. Most importantly, W-CSB-MSCs accelerated cartilage regeneration in damaged cartilage explants derived from OA patients. Thus, this new peptide and NPs dual engineering strategy shows potential for clinical applications to boost cartilage repair in OA using MSC therapy.

Multilayered hydrogel scaffold construct with native tissue matched elastic modulus: A regenerative microenvironment for urethral scar-free healing.

The unsuitable deformation stimulus, harsh urine environment, and lack of a regenerative microenvironment (RME) prevent scaffold-based urethral repair and ultimately lead to irreversible urethral scarring. The researchers clarify the optimal elastic modulus of the urethral scaffolds for urethral repair and design a multilayered PVA hydrogel scaffold for urethral scar-free healing. The inner layer of the scaffold has self-healing properties, which ensures that the wound effectively resists harsh urine erosion, even when subjected to sutures. In addition, the scaffold's outer layer has an extracellular matrix-like structure that synergizes with adipose-derived stem cells to create a favorable RME. In vivo experiments confirm successful urethral scar-free healing using the PVA multilayered hydrogel scaffold. Further mechanistic study shows that the PVA multilayer hydrogel effectively resists the urine-induced inflammatory response and accelerates the transition of urethral wound healing to the proliferative phase by regulating macrophage polarization, thus providing favorable conditions for urethral scar-free healing. This study provides mechanical criteria for the fabrication of urethral tissue-engineered scaffolds, as well as important insights into their design.

Mitochondrial 'Birth-Death' coordinator: An intelligent hydrogen nanogenerator to enhance intervertebral disc regeneration.

Currently, mitochondrial dysfunction caused by oxidative stress is a growing concern in degenerative diseases, notably intervertebral disc degeneration (IVDD). Dysregulation of the balance of mitochondrial quality control (MQC) has been considered the key contributor, while it's still challenging to effectively harmonize different MQC components in a simple and biologically safe way. Hydrogen gas (H2) is a promising mitochondrial therapeutic molecule due to its bio-reductivity and diffusibility across cellular membranes, yet its relationship with MQC regulation remains unknown. Herein, we propose a mitochondrial 'Birth-Death' coordinator achieved by an intelligent hydrogen nanogenerator (Fe@HP-OD), which can sustainably release H2 in response to the unique microenvironment in degenerated IVDs. Both in vitro and in vivo results prove alleviation of cellular oxidative stress and restoration of nucleus pulposus cells function, thereby facilitating successful IVD regeneration. Significantly, this study for the first time proposes the mitochondrial 'Birth-Death' coordination mechanism: 1) attenuation of overactivated mitochondrial 'Death' process (UPRmt and unselective mitophagy); and 2) activation of Adenosine 5'-monophosphate-activated protein kinase (AMPK) signaling pathway for mitochondrial 'Birth-Death' balance (mitochondrial biogenesis and controlled mitophagy). These pioneering findings can fill in the gaps in molecular mechanisms for H2 regulation on MQC homeostasis, and pave the way for future strategies towards restoring equilibrium of MQC system against degenerative diseases.

Characterization of Age-Dependent Changes in Skeletal Muscle Repair and Regeneration Using a Mouse Model of Acute Muscle Injury.

Acute skeletal muscle injury initiates a process of necrosis, debris clearance, and ultimately tissue regeneration via myogenesis. While skeletal muscle stem cells (MuSCs) are responsible for populating the proliferative myogenic progenitor pool to fuel muscle repair, recruited and resident immune cells have a central role in the regulation of muscle regeneration via the execution of phagocytosis and release of soluble factors that act directly on MuSCs to regulate myogenic differentiation. Therefore, the timing of MuSC proliferation and differentiation is closely linked to the populations and behaviors of immune cells present within skeletal muscle. This has important implications for aging and muscle repair, as systemic changes in immune system function contribute to a decline in muscle regenerative capacity. Here, we present adapted protocols for the isolation of mononuclear cells from skeletal muscles for the quantification of immune cell populations using flow cytometry. We also describe a cardiotoxin skeletal muscle injury protocol and detail the expected outcomes including immune cell infiltration to the injured sites and formation of new myocytes. As immune cell function is substantially influenced by aging, we extend these approaches and outcomes to aged mice.

Magnetically induced anisotropic structure in an injectable hydrogel for skeletal muscle regeneration.

Skeletal muscle integrity and its intrinsic aligned architecture are crucial for locomotion, postural support, and respiration functions, impacting overall quality of life. However, volumetric muscle loss (VML) can exceed intrinsic regenerative potential, leading to fibrosis and impairments. Autologous muscle grafting, the current gold standard, is constrained by tissue availability and success rates. Therefore, innovative strategies like cell-based therapies and scaffold-based approaches are needed. Our minimally invasive approach involves a tunable injectable hydrogel capable of achieving an aligned architecture post-injection via a low-intensity static magnetic field (SMF). Our hydrogel formulation uses gellan gum as the backbone polymer, enriched with essential extracellular matrix components such as hyaluronic acid and collagen type I, enhancing bio-functionality. To achieve an aligned architectural biomimicry, collagen type I is coupled with iron oxide magnetic nanoparticles, creating magnetic collagen bundles (MagC) that align within the hydrogel when exposed to a SMF. An extensive study was performed to characterize MagC and assess the hydrogel's stability, mechanical properties, and biological response in vitro and in vivo. The proposed system, fully composed of natural polymers, exhibited mechanical properties similar to human skeletal muscle and demonstrated effective biological performances, supporting its potential as a safe and patient-friendly treatment for VML.

Dental stem cell dynamics in periodontal ligament regeneration: from mechanism to application.

Periodontitis, a globally prevalent chronic inflammatory disease is characterized by the progressive degradation of tooth-supporting structures, particularly the periodontal ligament (PDL), which can eventually result in tooth loss. Despite the various clinical interventions available, most focus on symptomatic relief and lack substantial evidence of supporting the functional regeneration of the PDL. Dental stem cells (DSCs), with their homology and mesenchymal stem cell (MSC) properties, have gained significant attention as a potential avenue for PDL regeneration. Consequently, multiple therapeutic strategies have been developed to enhance the efficacy of DSC-based treatments and improve clinical outcomes. This review examines the mechanisms by which DSCs and their derivatives promote PDL regeneration, and explores the diverse applications of exogenous implantation and endogenous regenerative technology (ERT) aimed at amplifying the regenerative capacity of endogenous DSCs. Additionally, the persistent challenges and controversies surrounding DSC therapies are discussed, alongside an evaluation of the limitations in current research on the underlying mechanisms and innovative applications of DSCs in PDL regeneration with the aim of providing new insights for future development. Periodontitis, a chronic inflammatory disease, represents a major global public health concern, affecting a significant proportion of the population and standing as the leading cause tooth loss in adults. The functional periodontal ligament (PDL) plays an indispensable role in maintaining periodontal health, as its structural and biological integrity is crucial for the long-term prognosis of periodontal tissues. It is widely recognized as the cornerstone of periodontal regeneration Despite the availability of various treatments, ranging from nonsurgical interventions to guided tissue regeneration (GTR) techniques, these methods have shown limited success in achieving meaningful PDL regeneration. As a result, the inability to fully restore PDL function underscores the urgent need for innovative therapeutic strategies at reconstructing this essential structure. Stem cell therapy, known for its regenerative and immunomodulatory potential, offers a promising approach for periodontal tissue repair. Their application marks a significant paradigm shift in the treatment of periodontal diseases, opening new avenues for functional PDL regeneration. However, much of the current research has primarily focused on the regeneration of alveolar bone and gingiva, as these hard and soft tissues can be more easily evaluated through visual assessment. The complexity of PDL structure, coupled with the intricate interactions among cellular and molecular components, presents significant scientific and clinical hurdles in translating DSC research into practical therapeutic applications. This review provides a thorough exploration of DSC dynamics in periodontal regeneration, detailing their origins, properties, and derived products, while also examining their potential mechanisms and applications in PDL regeneration. It offers an in-depth analysis of the current research, landscape, acknowledging both the progress made and the challenges that remain in bridging the gap between laboratory findings and clinical implementation. Finally, the need for continued investigation into the intricate mechanisms governing DSC behavior and the optimization of their use in regenerative therapies for periodontal diseases is also emphasized.

Identification of a Regenerative Protocol for Recellularizing Human Auricular Cartilage Scaffolds.

OBJECTIVE: Utilizing biological scaffolds for cartilage tissue engineering is a promising tool for improving auricular reconstruction. Decellularized auricular scaffolds provide a means of regenerating cartilage for in vivo implantation, but identifying the ideal regenerative mix remains challenging. METHODS: Human cadaver auricular cartilage was decellularized and recellularized with either auricular chondrocytes alone, auricular chondrocytes with adipose-derived stem cells, or both cells with platelet-rich plasma. Confirmation of decellularization and recellularization was done by hematoxylin and eosin staining. Extracellular matrix preservation and production were determined by Masson's trichrome, Alcian blue, and Verhoeff-van Gieson staining. Collagen II assessments were made using immunohistochemistry. RESULTS: Decellularization of cadaver auricular cartilage was confirmed by the absence of cells, reduction in glycosaminoglycans, and the preservation of collagen and elastin. Recellularization was more efficient when chondrocytes were seeded with adipose-derived stem cells, which was enhanced by adding platelet-rich plasma. Coculture with platelet-rich plasma yielded better total collagen (56% increase) and glycosaminoglycan (47% increase) induction. Moreover, when platelet-rich plasma was added, collagen II induction was significantly increased (42%; P < 0.05). CONCLUSION: We identified a regenerative protocol that included auricular chondrocytes, adipose-derived stem cells, and platelet-rich plasma, which stimulated chondrogenesis on decellularized auricular cartilage. This finding provides a model to explore cartilage formation and the potential for improving auricular and cartilage-based reconstruction.

Microenvironment-responsive nanomedicines: a promising direction for tissue regeneration.

Severe tissue defects present formidable challenges to human health, persisting as major contributors to mortality rates. The complex pathological microenvironment, particularly the disrupted immune landscape within these defects, poses substantial hurdles to existing tissue regeneration strategies. However, the emergence of nanobiotechnology has opened a new direction in immunomodulatory nanomedicine, providing encouraging prospects for tissue regeneration and restoration. This review aims to gather recent advances in immunomodulatory nanomedicine to foster tissue regeneration. We begin by elucidating the distinctive features of the local immune microenvironment within defective tissues and its crucial role in tissue regeneration. Subsequently, we explore the design and functional properties of immunomodulatory nanosystems. Finally, we address the challenges and prospects of clinical translation in nanomedicine development, aiming to propose a potent approach to enhance tissue regeneration through synergistic immune modulation and nanomedicine integration.

Stem cell treatment for regeneration of the rotator cuff: study protocol for a prospective single-center randomized controlled trial (Lipo-cuff).

BACKGROUND: Rotator cuff tears (RCT) are a common musculoskeletal condition, especially in the aging population. The prevalence of rotator cuff tears varies based on factors like age, occupation, and activity level. In the general population, the prevalence of rotator cuff tears is estimated to be around 20 to 25%. Rotator cuff tears (RCT) have an impact in patients' pain level, shoulder function, sleep disturbance, and quality of life. Primary tendon surgery is in mostly cases necessary. This study aimed to examine if treatment of rotator cuff lesions with implantation of micro-fragmented adipose tissue can improve patients' reported pain and function compared to conventional surgery. METHODS: The study is a prospective superiority parallel-group single-center randomized controlled trial including 30 patients between 40 and 69 years of age in Denmark. Patients will be allocated 1:1 ratio to reconstruction of the supraspinatus tendon with an injection of micro-fragmented adipose tissue into the related muscle (stem cell treatment) or the standard of care (SOC), which is conventional surgery. Patients, project assistants, physicians, and outcome adjudicators are not blinded to randomization due to practical constraints. The radiologist and the statistician performing the analysis will be blinded. The primary outcome will be the Oxford shoulder score at 12 months post-surgery. DISCUSSION: This study will assess whether adding micro-fragmented adipose tissue therapy to conventional rotator cuff tear treatment can enhance recovery, accelerate return to daily activities, and improve functional outcomes. The research will also determine if this minimally invasive procedure could be standardized for routine patient care. TRIAL REGISTRATION: ClinicalTrials.gov NCT06505135. Registered on July 10, 2024.

The Xaliproden Nanoscale Zirconium-Porphyrin Metal-Organic Framework (XAL-NPMOF) Promotes Photoreceptor Regeneration Following Oxidative and Inflammatory Insults.

Background: Age-related macular degeneration (AMD) is becoming the leading cause of blindness in the aged population. The death of photoreceptors is the principal event which is lack of curative treatment. Xaliproden, a highly selective synthetic 5-OH-tryptamine (5HT) 1A receptor agonist, has the neuroprotective potential. However, its application has been limited by the insoluble formulation, low utilization efficiency and side effects caused by systemic administration. Methods: Nanoscale zirconium-porphyrin metal-organic framework (NPMOF) was used as a skeleton and loaded with xaliproden (XAL) to prepare a novel kind of nanoparticle, namely, XAL-NPMOF. The human umbilical vein endothelial cells, zebrafish embryos and larvae were used to test the biotoxicity and fluorescence imaging capability of XAL-NPMOF both in vitro and in vivo. A photoreceptor degeneration model was generated by intense light injury in adult zebrafish and XAL-NPMOF was delivered to the injured retina by intraocular injection. The photoreceptor regeneration, inflammatory response and visual function were explored by immunohistochemistry, quantitative real-time polymerase chain reaction and optomotor response analysis. Results: Following a single XAL-NPMOF intraocular injection, the injured retina underwent the faster photoreceptor regeneration with a recovery of visual function via promoting cell proliferation, suppressing the inflammatory responses and increasing the expression of antioxidases. Conclusion: As an amplifier, NPMOF can enhance the anti-inflammatory efficacy and neuroprotective effect of xaliproden. XAL-NPMOF could be a novel and convenient option for the treatment of AMD.

Distinct muscle regenerative capacity of human induced pluripotent stem cell-derived mesenchymal stromal cells in Ullrich congenital muscular dystrophy model mice.

BACKGROUND: Ullrich congenital muscular dystrophy (UCMD) is caused by a deficiency in type 6 collagen (COL6) due to mutations in COL6A1, COL6A2, or COL6A3. COL6 deficiency alters the extracellular matrix structure and biomechanical properties, leading to mitochondrial defects and impaired muscle regeneration. Therefore, mesenchymal stromal cells (MSCs) that secrete COL6 have attracted attention as potential therapeutic targets. Various tissue-derived MSCs exert therapeutic effects in various diseases. However, no reports have compared the effects of MSCs of different origins on UCMD pathology. METHODS: To evaluate which MSC population has the highest therapeutic efficacy for UCMD, in vivo (transplantation of MSCs to Col6a1-KO/NSG mice) and in vitro experiments (muscle stem cell [MuSCs] co-culture with MSCs) were conducted using adipose tissue-derived MSCs, bone marrow-derived MSCs, and xeno-free-induced iPSC-derived MSCs (XF-iMSCs). RESULTS: In transplantation experiments on Col6a1-KO/NSG mice, the group transplanted with XF-iMSCs showed significantly enhanced muscle fiber regeneration compared to the other groups 1 week after transplantation. At 12 weeks after transplantation, only the XF-iMSCs transplantation group showed a significantly larger muscle fiber diameter than the other groups without inducing fibrosis, which was observed in the other transplantation groups. Similarly, in co-culture experiments, XF-iMSCs were found to more effectively promote the fusion and differentiation of MuSCs derived from Col6a1-KO/NSG mice than the other primary MSCs investigated in this study. Additionally, in vitro knockdown and supplementation experiments suggested that the IGF2 secreted by XF-iMSCs promoted MuSC differentiation. CONCLUSION: XF-iMSCs are promising candidates for promoting muscle regeneration while avoiding fibrosis, offering a safer and more effective therapeutic approach for UCMD than other potential therapies.

Effects of using different dentin conditioners on dentin regeneration.

This experiment aimed to evaluate the impact of several dentine etching and conditioning agents on growth factors (GFs) liberation from dentine slices. Eighteen dentine slices were obtained from nine premolars divided in to six groups, the slices immersed in one mL test solutions for 5 min; Group 1: white Mineral trioxide aggregate (MTA), Group 2: Phosphate buffered saline (PBS), Group 3: 37% phosphoric acid, Group 4: 17% Ethylenediaminetetraacetic Acid (EDTA), Group 5: 10% Maleic acid (MAc), and Group 6: 0.7% Fumaric acid. The solutions were removed and stored directly at for further detection and quantification of transforming GF beta 1 (TGF-b1), bone morphogenetic protein 2 (BMP2) and vascular endothelial growth factor (VEGF) by enzyme-linked immunosorbent assay (ELISA). One-way ANOVA was used to compare the mean release and standard deviation between groups (α = 0.05). Tukey's post hoc applied for multiple comparisons. After five min conditioning of dentine slices, white MTA released the highest level of TGF-b1, BMP2 and VEGF among all groups, followed by 0.7% Fumaric acid with no significant difference between them, but compared to 37% phosphoric acid and PBS groups significant difference observed, which they released the least amount of GFs amongst all groups. Based on the results of this research the detectable release of TGF-b1, BMP2 and VEGF by 0.7% fumaric acid was comparable with white MTA from dentin slices.

Negative cell cycle regulation by calcineurin is necessary for proper beta cell regeneration in zebrafish.

Stimulation of pancreatic beta cell regeneration could be a therapeutic lead to treat diabetes. Unlike humans, the zebrafish can efficiently regenerate beta cells, notably from ductal pancreatic progenitors. To gain insight into the molecular pathways involved in this process, we established the transcriptomic profile of the ductal cells after beta cell ablation in the adult zebrafish. These data highlighted the protein phosphatase calcineurin (CaN) as a new potential modulator of beta cell regeneration. We showed that CaN overexpression abolished the regenerative response, leading to glycemia dysregulation. On the opposite, CaN inhibition increased ductal cell proliferation and subsequent beta cell regeneration. Interestingly, the enhanced proliferation of the progenitors was paradoxically coupled with their exhaustion. This suggests that the proliferating progenitors are next entering in differentiation. CaN appears as a guardian which prevents an excessive progenitor proliferation to preserve the pool of progenitors. Altogether, our findings reveal CaN as a key player in the balance between proliferation and differentiation to enable a proper beta cell regeneration.

Older spiny mice (Acomys cahirinus) have delayed and spatially heterogenous ear wound regeneration.

The African spiny mouse (Acomys cahirinus) is a unique mammalian model of tissue regeneration, regenerating 4 mm ear-hole punches with cartilage, adipocytes, hair follicles, and muscle. However, the time to regenerate ear tissue varies from 20 to 90 days and muscle regeneration is inconsistent. Some report that older spiny mice have delayed regeneration without investigation on the regenerative capacity of muscle. We thought that delayed regeneration and inconsistent muscle regeneration could be linked via age-related nerve degeneration. While the current study found that spiny mice aged 6-9 months had delayed regeneration compared to 3-4 month-old spiny mice, the capacity of muscle regeneration was unrelated to age, and there was little evidence for age-related nerve degeneration. Instead, the regeneration of muscle, cartilage and adipocytes was spatially heterogeneous, declining in amount from the proximal to distal region of the regenerated tissue. Also, cartilage regeneration in the distal region was decreased in ≥22-month-old Acomys and adipocyte regeneration was decreased in those older than 6 months, compared to 3-4 month olds. While the underlying mechanisms for delayed and spatially heterogenous regeneration remain unclear, age and the spatial region of the regenerated tissue should be considered in experimental designs with spiny mice.