Endothelial progenitor cells for diabetic cardiac and kidney disease

The management of diabetes mellitus and its resultant end organ dysfunction represents a major challenge to global health-care systems. Diabetic cardiac and kidney disease commonly co-occur and are significant contributors to the morbidity and mortality of patients with diabetes, carrying a poor prognosis. The tight link of these parallel end organ manifestations suggests a deeper common underlying pathology. Here, we outline the mechanistic link between diabetic cardiac and kidney disease, providing evidence for the role of endothelial dysfunction in both processes and the potential for cellular therapy to correct these disorders. Specifically, we review the preclinical and clinical evidence for endothelial progenitor cell therapy in cardiac, kidney, and cardio-renal disease applications. Finally, we outline novel approaches to endothelial progenitor cell therapy through cell enhancement and the use of extracellular vesicles, discussing published and future work.

Advances in Therapies to Treat Neonatal Hypoxic-Ischemic Encephalopathy

Neonatal hypoxic-ischemic encephalopathy (HIE) is a condition that results in brain damage in newborns due to insufficient blood and oxygen supply during or after birth. HIE is a major cause of neurological disability and mortality in newborns, with over one million neonatal deaths occurring annually worldwide. The severity of brain injury and the outcome of HIE depend on several factors, including the cause of oxygen deprivation, brain maturity, regional blood flow, and maternal health conditions. HIE is classified into mild, moderate, and severe categories based on the extent of brain damage and resulting neurological issues. The pathophysiology of HIE involves different phases, including the primary phase, latent phase, secondary phase, and tertiary phase. The primary and secondary phases are characterized by episodes of energy and cell metabolism failures, increased cytotoxicity and apoptosis, and activated microglia and inflammation in the brain. A tertiary phase occurs if the brain injury persists, characterized by reduced neural plasticity and neuronal loss. Understanding the cellular and molecular aspects of the different phases of HIE is crucial for developing new interventions and therapeutics. This review aims to discuss the pathophysiology of HIE, therapeutic hypothermia (TH), the only approved therapy for HIE, ongoing developments of adjuvants for TH, and potential future drugs for HIE.

Matrix Degradability Contributes to the Development of Salivary Gland Progenitor Cells with Secretory Functions

Synthetic matrices that are cytocompatible, cell adhesive, and cell responsive are needed for the engineering of implantable, secretory salivary gland constructs to treat radiation induced xerostomia or dry mouth. Here, taking advantage of the bioorthogonality of the Michael-type addition reaction, hydrogels with comparable stiffness but varying degrees of degradability (100% degradable, 100DEG; 50% degradable, 50DEG; and nondegradable, 0DEG) by cell-secreted matrix metalloproteases (MMPs) were synthesized using thiolated HA (HA-SH), maleimide (MI)-conjugated integrin-binding peptide (RGD-MI), and MI-functionalized peptide cross-linkers that are protease degradable (GIW-bisMI) or nondegradable (GIQ-bisMI). Organized multicellular structures developed readily in all hydrogels from dispersed primary human salivary gland stem cells (hS/PCs). As the matrix became progressively degradable, cells proliferated more readily, and the multicellular structures became larger, less spherical, and more lobular. Immunocytochemical analysis showed positive staining for stem/progenitor cell markers CD44 and keratin 5 (K5) in all three types of cultures and positive staining for the acinar marker α-amylase under 50DEG and 100DEG conditions. Quantitatively at the mRNA level, the expression levels of key stem/progenitor markers KIT, KRT5, and ETV4/5 were significantly increased in the degradable gels as compared to the nondegradable counterparts. Western blot analyses revealed that imparting matrix degradation led to >3.8-fold increase in KIT expression by day 15. The MMP-degradable hydrogels also promoted the development of a secretary phenotype, as evidenced by the upregulation of acinar markers α-amylase (AMY), aquaporin-5 (AQP5), and sodium-potassium chloride cotransporter 1 (SLC12A2). Collectively, we show that cell-mediated matrix remodeling is necessary for the development of regenerative pro-acinar progenitor cells from hS/PCs.

Inflammation Confers Healing Advantage to Corneal Epithelium Following Subsequent Injury

Recent evidence shows that epithelial stem/progenitor cells in barrier tissues such as the skin, airways and intestines retain a memory of previous injuries, which enables tissues to accelerate barrier restoration after subsequent injuries. The corneal epithelium, the outermost layer of the cornea, is the frontline barrier for the eye and is maintained by epithelial stem/progenitor cells in the limbus. Herein, we provide evidence that inflammatory memory also exists in the cornea. In mice, eyes that had been exposed to corneal epithelial injury exhibited faster re-epithelialization of the cornea and lower levels of inflammatory cytokines following subsequent injury (either the same or a different type of injury) relative to naïve eyes without previous injury. In ocular Sjögren's syndrome patients, corneal punctate epithelial erosions were significantly reduced after experiencing infectious injury compared with before. These results demonstrate that previous exposure of the corneal epithelium to inflammatory stimuli enhances corneal wound healing in response to a secondary assault, a phenomenon which points to the presence of nonspecific inflammatory memory in the cornea.

S100A6 Protein-Expression and Function in Norm and Pathology

S100A6, also known as calcyclin, is a calcium-binding protein belonging to the S100 protein family. It was first identified and purified more than 30 years ago. Initial structural studies, focused mostly on the mode and affinity of Ca²⁺ binding and resolution of the resultant conformational changes, were soon complemented by research on its expression, localization and identification of binding partners. With time, the use of biophysical methods helped to resolve the structure and versatility of S100A6 complexes with some of its ligands. Meanwhile, it became clear that S100A6 expression was altered in various pathological states and correlated with the stage/progression of many diseases, including cancers, indicative of its important, and possibly causative, role in some of these diseases. This, in turn, prompted researchers to look for the mechanism of S100A6 action and to identify the intermediary signaling pathways and effectors. After all these years, our knowledge on various aspects of S100A6 biology is robust but still incomplete. The list of S100A6 ligands is growing all the time, as is our understanding of the physiological importance of these interactions. The present review summarizes available data concerning S100A6 expression/localization, interaction with intracellular and extracellular targets, involvement in Ca²⁺-dependent cellular processes and association with various pathologies.

Promises and Challenges of Cell-Based Therapies to Promote Lung Regeneration in Idiopathic Pulmonary Fibrosis

The lung epithelium is constantly exposed to harmful agents present in the air that we breathe making it highly susceptible to damage. However, in instances of injury to the lung, it exhibits a remarkable capacity to regenerate injured tissue thanks to the presence of distinct stem and progenitor cell populations along the airway and alveolar epithelium. Mechanisms of repair are affected in chronic lung diseases such as idiopathic pulmonary fibrosis (IPF), a progressive life-threatening disorder characterized by the loss of alveolar structures, wherein excessive deposition of extracellular matrix components cause the distortion of tissue architecture that limits lung function and impairs tissue repair. Here, we review the most recent findings of a study of epithelial cells with progenitor behavior that contribute to tissue repair as well as the mechanisms involved in mouse and human lung regeneration. In addition, we describe therapeutic strategies to promote or induce lung regeneration and the cell-based strategies tested in clinical trials for the treatment of IPF. Finally, we discuss the challenges, concerns and limitations of applying these therapies of cell transplantation in IPF patients. Further research is still required to develop successful strategies focused on cell-based therapies to promote lung regeneration to restore lung architecture and function.

Pathogenesis of Human Adenomyosis: Current Understanding and Its Association with Infertility

The aim of this review article was to summarize our current understanding on the etiologies and pathogenesis of human adenomyosis and to clarify the relative association between adenomyosis and infertility. The exact pathogenesis of adenomyosis is still elusive. Among different reported concepts, direction invagination of gland cells from the basalis endometrium deep into myometrium is the most widely accepted opinion on the development of adenomyosis. According to this concept, endometrial epithelial cells and changed fibroblasts, abnormally found in the myometrium in response to repeated tissue injury and/or disruption at the endometrium-myometrium interface (EMI), elicit hyperplasia and hypertrophy of the surrounding smooth muscle cells. In this review, a comprehensive review was performed with a literature search using PubMed for all publications in English and Japanese (abstract in English), related to adenomyosis and infertility, from inception to April 2021. As an estrogen-regulated factor, hepatocyte growth factor (HGF) exhibits multiple functions in endometriosis, a disease commonly believed to arise from the functionalis endometrium. As a mechanistic basis of gland invagination, we investigated the role of HGF, either alone or in combination with estrogen, in the occurrence of epithelial-mesenchymal transition (EMT) in adenomyosis. Aside from microtrauma at the EMI, metaplasia of displaced Müllerian remnants, differentiation of endometrial stem/progenitor cells within the myometrium and somatic mutation of some target genes have been put forward to explain how adenomyosis develops. In addition, the possible role of microRNAs in adenomyosis is also discussed. Besides our knowledge on the conventional classification (focal and diffuse), two recently proposed classifications (intrinsic and extrinsic) of adenomyosis and the biological differences between them have been described. Although the mechanistic basis is unclear, the influence of adenomyosis on fertility outcome is important, especially considering the recent tendency to delay pregnancy among women. Besides other proposed mechanisms, a recent transmission election microscopic (TEM) study indicated that microvilli damage and an axonemal alteration in the apical endometria of human adenomyosis, in response to endometrial inflammation, may be involved in negative fertility outcomes. We present a critical analysis of the literature data concerning the mechanistic basis of infertility in women with adenomyosis and its impact on fertility outcome.

Human Peripheral Blood Mononucleocyte Derived Myeloid Committed Progenitor Cells Mitigate H-ARS by Exosomal Paracrine Signal

Radiation-induced loss of the hematopoietic stem cell progenitor population compromises bone marrow regeneration and development of mature blood cells. Failure to rescue bone marrow functions results in fatal consequences from hematopoietic injury, systemic infections, and sepsis. So far, bone marrow transplant is the only effective option, which partially minimizes radiation-induced hematopoietic toxicities. However, a bone marrow transplant will require HLA matching, which will not be feasible in large casualty settings such as a nuclear accident or an act of terrorism. In this study we demonstrated that human peripheral blood mononuclear cell-derived myeloid committed progenitor cells can mitigate radiation-induced bone marrow toxicity and improve survival in mice. These cells can rescue the recipient's hematopoietic stem cells from radiation toxicity even when administered up to 24 h after radiation exposure and can be subjected to allogenic transplant without GVHD development. Transplanted cells deliver sEVs enriched with regenerative and immune-modulatory paracrine signals to mitigate radiation-induced hematopoietic toxicity. This provides a natural polypharmacy solution against a complex injury process. In summary, myeloid committed progenitor cells can be prepared from blood cells as an off-the-shelf alternative to invasive bone marrow harvesting and can be administered in an allogenic setting to mitigate hematopoietic acute radiation syndrome.

Sovateltide Mediated Endothelin B Receptors Agonism and Curbing Neurological Disorders

Neurological/neurovascular disorders constitute the leading cause of disability and the second leading cause of death globally. Major neurological/neurovascular disorders or diseases include cerebral stroke, Alzheimer’s disease, spinal cord injury, neonatal hypoxic-ischemic encephalopathy, and others. Their pathophysiology is considered highly complex and is the main obstacle in developing any drugs for these diseases. In this review, we have described the endothelin system, its involvement in neurovascular disorders, the importance of endothelin B receptors (ETBRs) as a novel potential drug target, and its agonism by IRL-1620 (INN—sovateltide), which we are developing as a drug candidate for treating the above-mentioned neurological disorders/diseases. In addition, we have highlighted the results of our preclinical and clinical studies related to these diseases. The phase I safety and tolerability study of sovateltide has shown it as a safe and tolerable compound at therapeutic dosages. Furthermore, preclinical and clinical phase II studies have demonstrated the efficacy of sovateltide in treating acute ischemic stroke. It is under development as a first-in-class drug. In addition, efficacy studies in Alzheimer’s disease (AD), acute spinal cord injury, and neonatal hypoxic-ischemic encephalopathy (HIE) are ongoing. Successful completion of these studies will validate that ETBRs signaling can be an important target in developing drugs to treat neurological/neurovascular diseases.

Fabrication and characterization of osteogenic function of progenitor cell-laden gelatin microcarriers

Biomaterial-based bone regeneration strategies often include a cellular component to accelerate healing. Modular approaches have the potential for minimally-invasive delivery and the ability to conformally fill complex defects. In this study, spherical gelatin microparticles were fabricated via water-in-oil emulsification and were subsequently crosslinked with genipin. Microparticle diameter depended on impeller geometry, and increased stirring rates consistently produced smaller particles with narrower size distributions. Increasing the concentration of gelatin resulted in larger particles with a broader size distribution. Viscoelastic characterization showed that increased gelatin concentration produced stiffer matrices, though the mechanical properties at lower gelatin concentration were more stable across strain rate. Microparticles of 6.0% wt/vol gelatin were then applied as microcarriers for packed-bed culture of human mesenchymal stromal cells (MSC) at seeding densities of 5.0 × 10³ , 2.5 × 10⁴ , or 5.0 × 10⁴ cells/cm² of surface area, in either control or osteogenic medium. Cell viability was uniformly high (>90%) across seeding densities over 22 days in culture. MSC number stayed approximately constant in the 5.0 × 10³ and 2.5 × 10⁴  cells/cm² samples, while it dropped over time at 5.0 × 10⁴ cells/cm² . Alkaline phosphatase activity was significantly upregulated in osteogenic conditions relative to controls at day 15, and absolute calcium deposition was strongly induced by days 15 and 22. However, calcium deposition per cell was highest in the lowest cell density, suggesting an inhibitory effect of high cell numbers. These results show that genipin-crosslinked gelatin microcarriers can be reproducibly fabricated and used as microcarriers for progenitor cells, which may have utility in treating large and complex bone defects.

Cell autonomous TGFβ signaling is essential for stem/progenitor cell recruitment into degenerative tendons

Understanding cell recruitment in damaged tendons is critical for improvements in regenerative therapy. We recently reported that targeted disruption of transforming growth factor beta (TGFβ) type II receptor in the tendon cell lineage (Tgfbr2^ScxCre) resulted in resident tenocyte dedifferentiation and tendon deterioration in postnatal stages. Here we extend the analysis and identify direct recruitment of stem/progenitor cells into the degenerative mutant tendons. Cre-mediated lineage tracing indicates that these cells are not derived from tendon-ensheathing tissues or from a Scleraxis-expressing lineage, and they turned on tendon markers only upon entering the mutant tendons. Through immunohistochemistry and inducible gene deletion, we further find that the recruited cells originated from a Sox9-expressing lineage and their recruitment was dependent on cell autonomous TGFβ signaling. The cells identified in this study thus differ from previous reports of cell recruitment into injured tendons and suggest a critical role for TGFβ signaling in cell recruitment, providing insights that may support improvements in tendon repair.

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Targeted deletion of TGFβ signaling led to degenerative changes in mouse tendons

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Stem/progenitor cells were recruited into the degenerative mutant tendons

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The recruited cells are different from the ones so far reported in tendon injury

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Recruitment was dependent on cell autonomous TGFβ signaling in the recruited cells

Transitions in lineage specification and gene regulatory networks in hematopoietic stem/progenitor cells over human development

Human hematopoiesis is a dynamic process that starts in utero 18-21 days post-conception. Understanding the site- and stage-specific variation in hematopoiesis is important if we are to understand the origin of hematological disorders, many of which occur at specific points in the human lifespan. To unravel how the hematopoietic stem/progenitor cell (HSPC) compartment changes during human ontogeny and the underlying gene regulatory mechanisms, we compare 57,489 HSPCs from 5 different tissues spanning 4 developmental stages through the human lifetime. Single-cell transcriptomic analysis identifies significant site- and developmental stage-specific transitions in cellular architecture and gene regulatory networks. Hematopoietic stem cells show progression from cycling to quiescence and increased inflammatory signaling during ontogeny. We demonstrate the utility of this dataset for understanding aberrant hematopoiesis through comparison to two cancers that present at distinct time points in postnatal life-juvenile myelomonocytic leukemia, a childhood cancer, and myelofibrosis, which classically presents in older adults.

Menstrual fluid endometrial stem/progenitor cell and supernatant protein content: cyclical variation and indicative range

STUDY QUESTION

Does natural variation exist in the endometrial stem/progenitor cell and protein composition of menstrual fluid across menstrual cycles in women?

SUMMARY ANSWER

Limited variation exists in the percentage of some endometrial stem/progenitor cell types and abundance of selected proteins in menstrual fluid within and between a cohort of women.

WHAT IS KNOWN ALREADY

Menstrual fluid is a readily available biofluid that can represent the endometrial environment, containing endometrial stem/progenitor cells and protein factors. It is unknown whether there is natural variation in the cellular and protein content across menstrual cycles of individual women, which has significant implications for the use of menstrual fluid in research and clinical applications.

STUDY DESIGN, SIZE, DURATION

Menstrual fluid was collected from 11 non-pregnant females with regular menstrual cycles. Participants had not used hormonal medications in the previous 3 months. Participants collected menstrual fluid samples from up to five cycles using a silicone menstrual cup worn on Day 2 of menstrual bleeding.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Menstrual fluid samples were centrifuged to separate soluble proteins and cells. Cells were depleted of red blood cells and CD45+ leucocytes. Menstrual fluid-derived endometrial stem/progenitor cells were characterized using multicolour flow cytometry including markers for endometrial stem/progenitor cells N-cadherin (NCAD) and stage-specific embryonic antigen-1 (SSEA-1) (for endometrial epithelial progenitor cells; eEPC), and sushi domain containing-2 (SUSD2) (for endometrial mesenchymal stem cells; eMSC). The clonogenicity of menstrual fluid-derived endometrial cells was assessed using colony forming unit assays. Menstrual fluid supernatant was analyzed using a custom magnetic Luminex assay.

MAIN RESULTS AND THE ROLE OF CHANCE

Endometrial stem/progenitor cells are shed in menstrual fluid and demonstrate clonogenic properties. The intraparticipant agreement for SUSD2+ menstrual fluid-derived eMSC (MF-eMSC), SSEA-1+ and NCAD+SSEA-1+ MF-eEPC, and stromal clonogenicity were moderate-good (intraclass correlation; ICC: 0.75, 0.56, 0.54 and 0.52, respectively), indicating limited variability across menstrual cycles. Endometrial inflammatory and repair proteins were detectable in menstrual fluid supernatant, with five of eight (63%) factors demonstrating moderate intraparticipant agreement (secretory leukocyte protein inhibitor (SLPI), lipocalin-2 (NGAL), lactoferrin, follistatin-like 1 (FSTL1), human epididymis protein-4 (HE4); ICC ranges: 0.57-0.69). Interparticipant variation was limited for healthy participants, with the exception of key outliers of which some had self-reported menstrual pathologies.

LARGE SCALE DATA

N/A. There are no OMICS or other data sets relevant to this study.

LIMITATIONS, REASONS FOR CAUTION

The main limitations to this research relate to the difficulty of obtaining menstrual fluid samples across multiple menstrual cycles in a consistent manner. Several participants could only donate across <3 cycles and the duration of wearing the menstrual cup varied between 4 and 6 h within and between women. Due to the limited sample size used in this study, wider studies involving multiple consecutive menstrual cycles and a larger cohort of women will be required to fully determine the normal range of endometrial stem/progenitor cell and supernatant protein content of menstrual fluid. Possibility for selection bias and true representation of the population of women should also be considered.

WIDER IMPLICATIONS OF THE FINDINGS

Menstrual fluid is a reliable source of endometrial stem/progenitor cells and related endometrial proteins with diagnostic potential. The present study indicates that a single menstrual sample may be sufficient in characterizing a variety of cellular and protein parameters across women's menstrual cycles. The results also demonstrate the potential of menstrual fluid for identifying endometrial and menstrual abnormalities in both research and clinical settings as a non-invasive method for assessing endometrial health.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by grants from the Australian National Health and Medical Research Council to C.E.G. (Senior Research Fellowship 1024298 and Investigator Fellowship 1173882) and to J.E. (project grant 1047756), the Monash IVF Research Foundation to C.E.G. and the Victorian Government's Operational Infrastructure Support Program. K.A.W., M.L.D.-T., S.G.S. and J.E. declare no conflicts of interest. C.E.G. reports grants from NHMRC, during the conduct of the study; grants from EndoFound USA, grants from Ferring Research Innovation, grants from United States Department of Defence, grants from Clue-Utopia Research Foundation, outside the submitted work. CEF reports grants from EndoFound USA, grants from Clue-Utopia Research Foundation, outside the submitted work.

Cell Sources for Cultivated Meat: Applications and Considerations throughout the Production Workflow

Cellular agriculture is an emerging scientific discipline that leverages the existing principles behind stem cell biology, tissue engineering, and animal sciences to create agricultural products from cells in vitro. Cultivated meat, also known as clean meat or cultured meat, is a prominent subfield of cellular agriculture that possesses promising potential to alleviate the negative externalities associated with conventional meat production by producing meat in vitro instead of from slaughter. A core consideration when producing cultivated meat is cell sourcing. Specifically, developing livestock cell sources that possess the necessary proliferative capacity and differentiation potential for cultivated meat production is a key technical component that must be optimized to enable scale-up for commercial production of cultivated meat. There are several possible approaches to develop cell sources for cultivated meat production, each possessing certain advantages and disadvantages. This review will discuss the current cell sources used for cultivated meat production and remaining challenges that need to be overcome to achieve scale-up of cultivated meat for commercial production. We will also discuss cell-focused considerations in other components of the cultivated meat production workflow, namely, culture medium composition, bioreactor expansion, and biomaterial tissue scaffolding.

Human Uterine Rudiments: Histological and Immunohistochemical Study

Extensive studies of the rudimental tissues taken from patients with aplasia of the uterus and vagina are aimed at elucidation of the mechanisms of the genesis of these malformations and at the search of the ways of their correction. We performed a histological examination of human uterine rudiments and immunohistochemical analysis of the expression of estrogen and progesterone receptors, VEGF, and stem/progenitor cell markers in these tissues. We found that the rudimental tissues show signs of disorganized histogenesis, but retain activity and contain cells expressing estrogen and progesterone receptors and VEGF as well as poorly differentiated precursor cells or stem cells. The presented data contribute to the in-depth studies of the mechanisms of formation of uterine rudiments and development of methods of their correction.

[Research progress of endogenous repair strategy in intervertebral disc]

Objective

To review the research progress of endogenous repair strategy (ERS) in intervertebral disc (IVD).

Methods

The domestic and foreign literature related to ERS in IVD in recent years was reviewed, and its characteristics, status, and prospect in the future were summarized.

Results

The key of ERS in IVD is to improve the vitality of stem/progenitor cells in IVD or promote its migration from stem cell Niche to the tissue that need to repair. These stem/progenitor cells in IVD are derived from nucleus pulposus, annulus fibrosus, and cartilaginous endplate, showing similar biological characteristics to mesenchymal stem cells including the expression of the specific stem/progenitor cell surface markers and gene, and also the capacity of multiple differentiations potential. However, the development, senescence, and degeneration of IVD have consumed these stem/progenitor cells, and the harsh internal microenvironment further impair their biological characteristics, which leads to the failure of endogenous repair in IVD. At present, relevant research mainly focuses on improving the biological characteristics of endogenous stem/progenitor cells, directly supplementing endogenous stem/progenitor cells, biomaterials and small molecule compounds to stimulate the endogenous repair in IVD, so as to improve the effect of endogenous repair.

Conclusion

At present, ERS has gotten some achievements in the treatment of IVD degeneration, but its related studies are still in the pre-clinical stage. So further studies regarding ERS should be carried out in the future, especially in vivo experiments and clinical transformation.

Regeneration Potential of Jellyfish: Cellular Mechanisms and Molecular Insights

Medusozoans, the Cnidarian subphylum, have multiple life stages including sessile polyps and free-swimming medusae or jellyfish, which are typically bell-shaped gelatinous zooplanktons that exhibit diverse morphologies. Despite having a relatively complex body structure with well-developed muscles and nervous systems, the adult medusa stage maintains a high regenerative ability that enables organ regeneration as well as whole body reconstitution from the part of the body. This remarkable regeneration potential of jellyfish has long been acknowledged in different species; however, recent studies have begun dissecting the exact processes underpinning regeneration events. In this article, we introduce the current understanding of regeneration mechanisms in medusae, particularly focusing on cellular behaviors during regeneration such as wound healing, blastema formation by stem/progenitor cells or cell fate plasticity, and the organism-level patterning that restores radial symmetry. We also discuss putative molecular mechanisms involved in regeneration processes and introduce a variety of novel model jellyfish species in the effort to understand common principles and diverse mechanisms underlying the regeneration of complex organs and the entire body.

Combined hepatocellular-cholangiocarcinoma: An update

Combined hepatocellular-cholangiocarcinoma (cHCC-CCA) is a tumour that exhibits both hepatocytic and biliary differentiation. Classical risk factors for hepatocellular carcinoma (HCC) seem to also predispose patients to the development of cHCC-CCA. The pathological definition of cHCC-CCA has significantly evolved over time. The last 2019 WHO classification highlighted that the diagnosis of cHCC-CCA should be primarily based on morphology using routine stainings, with additional immunostaining used to refine the identification of subtypes. Among them, "intermediate cell carcinoma" is recognised as a specific subtype, while "cholangiolocellular carcinoma" is now considered a subtype of iCCA. Increasing molecular evidence supports the clonal nature of cHCC-CCA and parallels its biphenotypic histological appearance, with genetic alterations that are classically observed in HCC and/or iCCA. That said, the morphological diagnosis of cHCC-CCA is still challenging for radiologists and pathologists, especially on biopsy specimens. Identification of cHCC-CCA's cell of origin remains an area of active research. Its prognosis is generally worse than that of HCC, and similar to that of iCCA. Resection with lymph node dissection is unfortunately the only curative option for patients with cHCC-CCA. Thus, there remains an urgent need to develop specific therapeutic strategies for this unique clinical entity.

Arid1a-Plagl1-Hh signaling is indispensable for differentiation-associated cell cycle arrest of tooth root progenitors

Chromatin remodelers often show broad expression patterns in multiple cell types yet can elicit cell-specific effects in development and diseases. Arid1a binds DNA and regulates gene expression during tissue development and homeostasis. However, it is unclear how Arid1a achieves its functional specificity in regulating progenitor cells. Using the tooth root as a model, we show that loss of Arid1a impairs the differentiation-associated cell cycle arrest of tooth root progenitors through Hedgehog (Hh) signaling regulation, leading to shortened roots. Our data suggest that Plagl1, as a co-factor, endows Arid1a with its cell-type/spatial functional specificity. Furthermore, we show that loss of Arid1a leads to increased expression of Arid1b, which is also indispensable for odontoblast differentiation but is not involved in regulation of Hh signaling. This study expands our knowledge of the intricate interactions among chromatin remodelers, transcription factors, and signaling molecules during progenitor cell fate determination and lineage commitment.

Epithelial Stem and Progenitor Cells in Lung Repair and Regeneration

The mammalian lung epithelium is composed of a wide array of specialized cells that have adapted to survive environmental exposure and perform the tasks necessary for respiration. Although the majority of these cells are remarkably quiescent during adult lung homeostasis, a growing body of literature has demonstrated the capacity of these epithelial lineages to proliferate in response to injury and regenerate lost or damaged cells. In this review, we focus on the regionally distinct lung epithelial cell types that contribute to repair after injury, and we address current controversies regarding whether elite stem cells or frequent facultative progenitors are the predominant participants. We also shed light on the newly emerging approaches for exogenously generating similar lung epithelial lineages from pluripotent stem cells.

Long-term stimulation of the anteromedial thalamus increases hippocampal neurogenesis and spatial reference memory in adult rats

Deep brain stimulation (DBS) has shown positive clinical results in neurodegenerative diseases. Previous work from our group showed that a single session of DBS to the anteromedial thalamic nucleus (AMN) in awake rats, increased proliferation of stem/progenitor cells in the dentate gyrus (DG) of the hippocampus. We thought to examine the effect of single versus multiple sessions of DBS to the AMN in modulating adult hippocampal neurogenesis. Rats received unilateral single session, multiple sessions or no electrical stimulation (sham) in the right AMN. Rats received 5'-bromo-2'-deoxyuridine (BrdU) injections and were followed over a period of 1 week or 4 weeks. Single session of electrical stimulation induced a 1.9-fold increase in the number of proliferating BrdU positive cells after one week from stimulation and a 1.8-fold increase at four weeks post stimulation, both in the ipsilateral DG. As for multiple sessions of stimulation, they induced a 3- fold increase that extended to the contralateral DG after 4 weeks from stimulation. Spatial reference memory was tested in the Y-maze test by examining novel arm exploration. Both single and multiple sessions of stimulation prompted an increase in novel arm exploration at week 4, while only the multiple sessions of stimulation had this effect starting from week 1. This study demonstrates that sustained activation of the AMN boosts neurogenesis and improves spatial reference memory.

Current and Future Perspectives of the Use of Organoids in Radiobiology

The majority of cancer patients will be treated with radiotherapy, either alone or together with chemotherapy and/or surgery. Optimising the balance between tumour control and the probability of normal tissue side effects is the primary goal of radiation treatment. Therefore, it is imperative to understand the effects that irradiation will have on both normal and cancer tissue. The more classical lab models of immortal cell lines and in vivo animal models have been fundamental to radiobiological studies to date. However, each of these comes with their own limitations and new complementary models are required to fill the gaps left by these traditional models. In this review, we discuss how organoids, three-dimensional tissue-resembling structures derived from tissue-resident, embryonic or induced pluripotent stem cells, overcome the limitations of these models and thus have a growing importance in the field of radiation biology research. The roles of organoids in understanding radiation-induced tissue responses and in moving towards precision medicine are examined. Finally, the limitations of organoids in radiobiology and the steps being made to overcome these limitations are considered.

Development of Male External Urethral Sphincter and Tissue-Resident Stem/Progenitor Cells in Rats

Stress urinary incontinence (SUI) after prostate surgery is primarily caused by urethral sphincter damage. There are few effective therapeutic approaches for male SUI due to both insufficient study of the structure of the external urethral sphincter (EUS) and incomplete understanding of the resident EUS stem/progenitor cells. The goals of this study were to localize and to determine the distribution of tissue-resident stem/progenitor cells in the male EUS throughout EUS development and to understand the anatomic temporal patterns of the EUS. Newborn Sprague Dawley rats were intraperitoneally injected with the thymidine analogue, 5-ethynyl-2-deoxyuridine (EdU), and the EUS was harvested at five time points (1, 2, 3, 4, and 8 weeks postinjection). The tissue was then processed for EdU staining and immunofluorescence staining for stem cell markers Ki67 and proliferating cell nuclear antigen. We counted the EdU+ label-retaining cells (LRCs) at each time point and colocalized with each stem cell marker, also we isolated and cultured the cells in vitro. The results revealed that the number of EdU+ LRCs in each EUS cross-section decreased over time and that the LRCs were located immediately under the basal membrane of laminin, densely adherent to the muscle fibers. In addition, the thickness of the striated muscle layer developed much faster than the smooth muscle layer during EUS development. By 4 weeks, the structure of the EUS layers was well differentiated. The EUS resident stem/progenitor cells were isolated with MACS® MicroBeads system, and myogenesis was confirmed. In this study, we defined both the time-course development of the EUS and the distribution of resident stem/progenitor cells. This information is crucial for forthcoming studies regarding male micturition and for development of novel therapeutic approaches for postoperative male SUI.

The Effect of Intracoronary Infusion of Autologous Bone Marrow-Derived Lineage-Negative Stem/Progenitor Cells on Remodeling of Post-Infarcted Heart in Patient with Acute Myocardial Infarction

Introduction: Regenerative capacity of the heart is limited, and the post-infarct left ventricle (LV) dysfunction is associated with poor prognosis. Administration of stem/progenitor cells (SPCs) is a promising approach for cardiac regeneration. Objectives: In the study, we assessed LV function and post-infarcted remodeling in patients with ST-elevated myocardial infarct (STEMI) who received autologous lineage-negative (LIN^-) SPCs. Patients and methods: Patients with STEMI and one-vessel coronary artery disease treated with percutaneous revascularisation were divided into study group (LIN^- group, 15 patients) that received standard therapy and autologous BM-derived LIN^- SPCs and control group (standard therapy group, 19 patients). The cells were administered intracoronary 24 hours after STEMI. The follow-up was 12 months with subsequent non-invasive tests and laboratory parameter evaluation on days 1^st, 3^rd, and 7^th as well as at 1^st, 3^rd, 6^th and 12^th month after STEMI. Results: All procedures related to SPCs administration were well tolerated by the patients. In 12-month follow-up, there were no major adverse cardiac events connected with LIN^- SPCs administration. During 12-month follow-up, 9 patients from LIN^- group (Responders) achieved an improvement in LV ejection fraction (>10% after 12 months) with no signs of unfavorable LV remodeling. Laboratory parameters analysis showed that Troponin T levels were significantly lower until day 7^th in the Responders group, while brain natriuretic peptide (BNP) level remained significantly lower from day 3^rd to 12^th month respectively. Conclusions: Intracoronary infusion of autologous BM-derived LIN^- stem/progenitor cells is feasible and safe for patient. Improvement in LV function and prevention of unfavorable remodeling in the 60% of study group seems relatively promising. Stem cell-based therapy for cardiac regeneration still needs more accurate and extensive investigations to estimate and improve their efficacy.

Putative human myometrial and fibroid stem-like cells have mesenchymal stem cell and endometrial stromal cell properties

STUDY QUESTION

Can endometrial stromal stem/progenitor cell markers, SUSD2 and CD146/CD140b, enrich for human myometrial and fibroid stem/progenitor cells?

SUMMARY ANSWER

SUSD2 enriches for myometrial and fibroid cells that have mesenchymal stem cell (MSC) characteristics and can also be induced to decidualise.

WHAT IS KNOWN ALREADY

Mesenchymal stem-like cells have been separately characterised in the endometrial stroma and myometrium and may contribute to diseases in their respective tissues.

STUDY DESIGN, SIZE, DURATION

Normal myometrium, fibroids and endometrium were collected from hysterectomies with informed consent. Primary cells or tissues were used from at least three patient samples for each experiment.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Flow cytometry, immunohistochemistry and immunofluorescence were used to characterise tissues. In vitro colony formation in normoxic and hypoxic conditions, MSC lineage differentiation (osteogenic and adipogenic) and decidualisation were used to assess stem cell activity. Xenotransplantation into immunocompromised mice was used to determine in vivo stem-like activity. Endpoint measures included quantitative PCR, colony formation, trichrome, Oil Red O and alkaline phosphatase activity staining.

MAIN RESULTS AND THE ROLE OF CHANCE

CD146+CD140b+ and/or SUSD2+ myometrial and fibroid cells were located in the perivascular region and formed more colonies in vitro compared to control cells and differentiated down adipogenic and osteogenic mesenchymal lineages in vitro. SUSD2+ myometrial cells had greater in vitro decidualisation potential, and SUSD2+ fibroid cells formed larger tumours in vivo compared to control cells.

LARGE-SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Markers used in this study enrich for cells with stem/progenitor cell activity; however, they do not distinguish stem from progenitor cells. SUSD2+ myometrial cells express markers of decidualisation when treated in vitro, but in vivo assays are needed to fully demonstration their ability to decidualise.

WIDER IMPLICATIONS OF THE FINDINGS

These results suggest a possible common MSC for the endometrial stroma and myometrium, which could be the tumour-initiating cell for uterine fibroids.

STUDY FUNDING/COMPETING INTEREST(S)

These studies were supported by NIH grants to JMT (R01OD012206) and to ALP (F32HD081856). The authors certify that we have no conflicts of interest to disclose.

Characterization of a prevascularized biomimetic tissue engineered scaffold for bone regeneration

Significant bone loss due to disease or severe injury can result in the need for a bone graft, with over 500,000 procedures occurring each year in the United States. However, the current standards for grafting, autografts and allografts, can result in increased patient morbidity or a high rate of failure respectively. An ideal alternative would be a biodegradable tissue engineered graft that fulfills the function of bone while promoting the growth of new bone tissue. We developed a prevascularized tissue engineered scaffold of electrospun biodegradable polymers PLLA and PDLA reinforced with hydroxyapatite, a mineral similar to that found in bone. A composite design was utilized to mimic the structure and function of human trabecular and cortical bone. These scaffolds were characterized mechanically and in vitro to determine osteoinductive and angioinductive properties. It was observed that further reinforcement is necessary for the scaffolds to mechanically match bone, but the scaffolds are successful at inducing the differentiation of mesenchymal stem cells into mature bone cells and vascular endothelial cells. Prevascularization was seen to have a positive effect on angiogenesis and cellular metabolic activity, critical factors for the integration of a graft.

Dynamic Assembly of Human Salivary Stem/Progenitor Microstructures Requires Coordinated α1β1 Integrin-Mediated Motility

A tissue engineering approach can provide replacement salivary gland structures to patients with hyposalivation disorders and xerostomia. Salivary human stem/progenitor cells (hS/PCs) were isolated from healthy regions of parotid glands of head and neck surgery patients, expanded, then encapsulated in biocompatible hyaluronate (HA)-based hydrogels. These bioactive hydrogels provide a surrogate territorial matrix suitable for the dynamic assembly, growth and reorganization of salivary gland components. This study examined the dynamics of salivary microstructure formation, growth, and reorganization using time-lapse imaging over 15 h. Immunofluorescence detection monitored production of individual basement membrane components forming around developing microstructures, and Ki67 assessed proliferation. Dynamic movements in hydrogels were quantified by measuring angular velocity (ω) of rotating salivary microstructures and changes in basement membrane architecture during microstructure growth. Integrin involvement in the dynamic reassembly was assessed using knockdown and inhibitor approaches. Single hS/PCs expanded over 5 days into spherical microstructures typically containing 3–10 cells. In larger macrostructures, proliferation occurred near the peripheral basement membrane that underwent growth-associated cycles of thinning and collapse. De novo secretion of laminin/collagen IV from reorganizing hS/PCs preceded that of perlecan/HSPG2. Microstructures routinely expressed β₁ integrin-containing complexes at basement membrane-associated regions and exhibited spontaneous and coordinated rotation during basement membrane maturation. β₁ integrin siRNA knockdown at the single-cell state prevented hS/PC microstructure growth. After microstructure formation, β₁ integrin knockdown reduced rotation and mean ω by 84%. Blockade of the α₁ integrin subunit (CD49a) that associates with β₁ reduced mean ω by 66%. Studies presented here show that initial hS/PC structure growth and basement membrane maturation depends on α₁β₁-integrin mediated signaling. Coordinated cellular motility during neotissue reorganization reminiscent of salivary gland acini was critically dependent both on hS/PC-secretion of laminin,collagen type-IV, and perlecan/HSPG2 and the force-driven interactions of α₁β₁-integrin activation. We conclude that α₁β₁-integrin plays a critical role in establishing human salivary gland coordinated structure and function, and that its activation in tissue engineered systems is essential to tissue assembly.

Three Dimensional Culture of Potential Epithelial Progenitor Cells in Human Lacrimal Gland

Purpose

We investigate human lacrimal gland tissue to determine the presence of progenitor cells in this adult human tissue.

Methods

Six human lacrimal gland tissues from donors were collected and stored immediately in the culture medium at 4°C until the next procedure. One part of the lacrimal gland tissue was prepared for immunofluorescence staining and the other part was prepared for primary cell culture. Immunofluorescence analysis was conducted to evaluate cultured lacrimal epithelial phenotype and progenitor cell markers for five passages. Real-time polymerase chain reaction (PCR) was performed to assess proliferation markers in the different passages. Three-dimensional culture and PCR were conducted to determine the differentiation potential of cultured human lacrimal gland cells.

Results

Human lacrimal gland tissue expressed a number of epithelial progenitor cell markers. Precursor cell markers C-Kit, K15, Nestin, and P63 were observed in lacrimal gland tissues. Lacrimal gland epithelial cells were cultured successfully and passaged to P5. The cultured lacrimal gland epithelial cells were positive for pan-cytokeratin (PCK), AQP5, Rab3D, ABCB5, C-kit, K15, Ki67, and P63. Human lacrimal gland cells could form spheroids in vitro and then grow into mini-gland-like structures. PCR results showed proliferation and differentiation capability of those cultured cells.

Conclusions

Human lacrimal gland tissues contain precursor marker-positive cells and marker expression also was detected in ex vivo cultured cells, which showed differentiation capability.

Translational Relevance

Future studies of differentiation in human lacrimal gland tissue may aid in developing stem cell-based therapies for dry eye disease.

STAT5a/b Deficiency Delays, but does not Prevent, Prolactin-Driven Prostate Tumorigenesis in Mice

The canonical prolactin (PRL) Signal Transducer and Activator of Transcription (STAT) 5 pathway has been suggested to contribute to human prostate tumorigenesis via an autocrine/paracrine mechanism. The probasin (Pb)-PRL transgenic mouse models this mechanism by overexpressing PRL specifically in the prostate epithelium leading to strong STAT5 activation in luminal cells. These mice exhibit hypertrophic prostates harboring various pre-neoplastic lesions that aggravate with age and accumulation of castration-resistant stem/progenitor cells. As STAT5 signaling is largely predominant over other classical PRL-triggered pathways in Pb-PRL prostates, we reasoned that Pb-Cre recombinase-driven genetic deletion of a floxed Stat5a/b locus should prevent prostate tumorigenesis in so-called Pb-PRL^ΔSTAT5 mice. Anterior and dorsal prostate lobes displayed the highest Stat5a/b deletion efficiency with no overt compensatory activation of other PRLR signaling cascade at 6 months of age; hence the development of tumor hallmarks was markedly reduced. Stat5a/b deletion also reversed the accumulation of stem/progenitor cells, indicating that STAT5 signaling regulates prostate epithelial cell hierarchy. Interestingly, ERK1/2 and AKT, but not STAT3 and androgen signaling, emerged as escape mechanisms leading to delayed tumor development in aged Pb-PRL^ΔSTAT5 mice. Unexpectedly, we found that Pb-PRL prostates spontaneously exhibited age-dependent decline of STAT5 signaling, also to the benefit of AKT and ERK1/2 signaling. As a consequence, both Pb-PRL and Pb-PRL^ΔSTAT5 mice ultimately displayed similar pathological prostate phenotypes at 18 months of age. This preclinical study provides insight on STAT5-dependent mechanisms of PRL-induced prostate tumorigenesis and alternative pathways bypassing STAT5 signaling down-regulation upon prostate neoplasia progression.

Salispheres from Different Major Salivary Glands for Glandular Regeneration

Dysfunctional salivary glands (SGs) are a clinical challenge due to the lack of effective treatments. Cell therapy with stem/progenitor cells may improve this situation by providing promising therapeutic solutions. Therefore, exploring abundant cellular sources is important. Three major pairs of SGs are located in different anatomic regions: the parotid glands, the submandibular glands, and the sublingual glands. Although SG stem/progenitor cells can be isolated and cultivated from all major SGs as salispheres, the differences among SG origins remain unclear. In this study, salispheres were successfully isolated from all major SGs. The salispheres demonstrated unique cellular features that originated from their native tissues. The characteristic expression profiles and cellular features of SG stem cells were demonstrated in all salispheres. When they were transplanted into irradiated animals, the salispheres were all capable of improving the saliva secretion that was disrupted by irradiation. Typical histologic structures could be observed in most parts of the treated glands, and the fibrotic environments of irradiated submandibular glands were remodeled by all salispheres regardless of origins. This study characterized the cellular features and in vivo effects of salispheres that were derived from different anatomic origins. The results suggest the possibility of functional redundancy among distinct pairs of major SGs, which is useful for the design of cell therapy to treat dysfunctional glandular organs.

Core regulatory RNA molecules identified in articular cartilage stem/progenitor cells during osteoarthritis progression

Aim: To assess cartilage-derived stem/progenitor cells (CSPCs) in osteoarthritis (OA) by employing mRNA-miRNA-circRNA-lncRNA network biology approach. Methods: Differentially expressed (DE) RNAs in CSPCs from 2-/4-/8-month-old STR/Ort and CBA mice were identified to construct networks via RNA sequencing. Results: Compared with age-matched CBA mice, 4-/8-month-old STR/Ort mice had cartilage lesions and their CSPCs exhibited lower proliferative and differentiation capacity (decreased CD44 and CD90), and identified 7082 DE RNAs in STR/Ort mice were associated with strain differences or OA progression. OA-related core RNAs were identified via the networks constructed with the predominant DE RNAs, which were involved in the signaling pathways (NF-κB/MAPK/Hippo/Wnt/TGF-β/cytoskeleton organization). The core RNAs (miR-322-5p/miR-493-5p/miR-378c/CPNE1/Cdh2/PRDM16/CTGF/NCAM1) were validated in CSPCs from OA patients. Conclusion: RNA-based networks identifying core RNAs and signaling pathways contribute to CSPC-dependent OA mechanisms.

Telomerase Reverse Transcriptase Expression in Mouse Endometrium During Reepithelialization and Regeneration in a Menses-Like Model

The regenerative capacity of the endometrium has been attributed to resident stem/progenitor cells. A number of stem/progenitor markers have been reported for human endometrial stem/progenitor cells; however, the lack of convenient markers in the mouse has made experimental investigation into endometrial regeneration difficult. We recently identified endometrial epithelial, endothelial, and immune cells, which express a reporter for the stem/progenitor marker, mouse telomerase reverse transcriptase (mTert). In this study, we investigate the expression pattern of a green fluorescent protein (GFP) reporter for mTert promoter activity (mTert-GFP) in endometrial regeneration following a menses-like event. mTert-GFP expression marks subepithelial populations of T cells and mature macrophages and may play a role in immune cell regulated repair. Clusters of mTert-GFP-positive epithelial cells were identified close to areas of reepithelialization and possibly highlight a role for mTert in the repair and regeneration of the endometrial epithelium.

Expansion of airway basal epithelial cells from primary human non-small cell lung cancer tumors

Pre-clinical non-small cell lung cancer (NSCLC) models are poorly representative of the considerable inter- and intra-tumor heterogeneity of the disease in patients. Primary cell-based in vitro models of NSCLC are therefore desirable for novel therapy development and personalized cancer medicine. Methods have been described to generate rapidly proliferating epithelial cell cultures from multiple human epithelia using 3T3-J2 feeder cell culture in the presence of Y-27632, a RHO-associated protein kinase (ROCK) inhibitor, in what are known as "conditional reprograming conditions" (CRC) or 3T3 + Y. In some cancer studies, variations of this methodology have allowed primary tumor cell expansion across a number of cancer types but other studies have demonstrated the preferential expansion of normal epithelial cells from tumors in such conditions. Here, we report our experience regarding the derivation of primary NSCLC cell cultures from 12 lung adenocarcinoma patients enrolled in the Tracking Cancer Evolution through Therapy (TRACERx) clinical study and discuss these in the context of improving the success rate for in vitro cultivation of cells from NSCLC tumors.

PAF-Myc-Controlled Cell Stemness Is Required for Intestinal Regeneration and Tumorigenesis

The underlying mechanisms of how self-renewing cells are controlled in regenerating tissues and cancer remain ambiguous. PCNA-associated factor (PAF) modulates DNA repair via PCNA. Also, PAF hyperactivates Wnt/β-catenin signaling independently of PCNA interaction. We found that PAF is expressed in intestinal stem and progenitor cells (ISCs and IPCs) and markedly upregulated during intestinal regeneration and tumorigenesis. Whereas PAF is dispensable for intestinal homeostasis, upon radiation injury, genetic ablation of PAF impairs intestinal regeneration along with the severe loss of ISCs and Myc expression. Mechanistically, PAF conditionally occupies and transactivates the c-Myc promoter, which induces the expansion of ISCs/IPCs during intestinal regeneration. In mouse models, PAF knockout inhibits Apc inactivation-driven intestinal tumorigenesis with reduced tumor cell stemness and suppressed Wnt/β-catenin signaling activity, supported by transcriptome profiling. Collectively, our results unveil that the PAF-Myc signaling axis is indispensable for intestinal regeneration and tumorigenesis by positively regulating self-renewing cells.

A Pdgf-cCreERT2 knock-in mouse model for tracing PDGF-C cell lineages during development

PDGF-C, a member of the platelet-derived growth factor (PDGF) family, plays important roles in the development of craniofacial structures, the neural system, the vascular system, and tumors. PDGF-C could also be required for the regulation of certain types of stem or progenitor cells as suggested by its expression in the regions where these cells are located. To further characterize the role of PDGF-C in development, we generated a Pdgf-c^CreERT2 mouse strain, in which a tamoxifen-inducible Cre (CreERT2) cDNA was specifically targeted into the Pdgf-c genomic locus and controlled by the endogenous Pdgf-c regulatory elements. We also showed that Cre activity in this mouse strain could be specifically induced by tamoxifen, which allowed the fate of PDGF-C-expressing cells to be traced at various stages of development. Using this model system, we demonstrated for the first time that PDGF-C-expressing cells could be multipotent, generating multiple cell lineages required for the formation of the cerebellum. Therefore, the Pdgf-c^CreERT2 mouse strain generated in this study will be a valuable transgenic tool for exploring the function of PDGF-C in development and stem cell biology.

Osteocalcin expressing cells from tendon sheaths in mice contribute to tendon repair by activating Hedgehog signaling

Both extrinsic and intrinsic tissues contribute to tendon repair, but the origin and molecular functions of extrinsic tissues in tendon repair are not fully understood. Here we show that tendon sheath cells harbor stem/progenitor cell properties and contribute to tendon repair by activating Hedgehog signaling. We found that Osteocalcin (Bglap) can be used as an adult tendon-sheath-specific marker in mice. Lineage tracing experiments show that Bglap-expressing cells in adult sheath tissues possess clonogenic and multipotent properties comparable to those of stem/progenitor cells isolated from tendon fibers. Transplantation of sheath tissues improves tendon repair. Mechanistically, Hh signaling in sheath tissues is necessary and sufficient to promote the proliferation of Mkx-expressing cells in sheath tissues, and its action is mediated through TGFβ/Smad3 signaling. Furthermore, co-localization of GLI1⁺ and MKX⁺ cells is also found in human tendinopathy specimens. Our work reveals the molecular function of Hh signaling in extrinsic sheath tissues for tendon repair.

Fibrinogen Activates BMP Signaling in Oligodendrocyte Progenitor Cells and Inhibits Remyelination after Vascular Damage

Blood-brain barrier (BBB) disruption alters the composition of the brain microenvironment by allowing blood proteins into the CNS. However, whether blood-derived molecules serve as extrinsic inhibitors of remyelination is unknown. Here we show that the coagulation factor fibrinogen activates the bone morphogenetic protein (BMP) signaling pathway in oligodendrocyte progenitor cells (OPCs) and suppresses remyelination. Fibrinogen induces phosphorylation of Smad 1/5/8 and inhibits OPC differentiation into myelinating oligodendrocytes (OLs) while promoting an astrocytic fate in vitro. Fibrinogen effects are rescued by BMP type I receptor inhibition using dorsomorphin homolog 1 (DMH1) or CRISPR/Cas9 activin A receptor type I (ACVR1) knockout in OPCs. Fibrinogen and the BMP target Id2 are increased in demyelinated multiple sclerosis (MS) lesions. Therapeutic depletion of fibrinogen decreases BMP signaling and enhances remyelination in vivo. Targeting fibrinogen may be an upstream therapeutic strategy to promote the regenerative potential of CNS progenitors in diseases with remyelination failure.

S100A6 - focus on recent developments

The Ca2+-binding protein, S100A6, belongs to the S100 family. Binding of Ca2+ induces a conformational change, which causes an increase in the overall S100A6 hydrophobicity and allows it to interact with many targets. S100A6 is expressed in different normal tissues and in many tumors. Up to now it has been shown that S100A6 is involved in cell proliferation, cytoskeletal dynamics and tumorigenesis, and that it might have some extracellular functions. In this review, we summarize novel discoveries concerning S100A6 targets, its involvement in cellular signaling pathways, and presence in stem/progenitor cells, extracellular matrix and body fluids of diseased patients.

Bone-forming cells with pronounced spread into the third dimension in polymer scaffolds fabricated by two-photon polymerization

The main aim of this work was to stimulate bone‐forming cells to produce three‐dimensional networks of mineralized proteins such as those occurring in bones. This was achieved by a novel approach using a specific type of mesenchymal progenitor cells (i.e., primary fibroblast cells from human hair roots) seeded on to polymer scaffolds. We wrote polymer microstructures with one or more levels of quadratic pores on to a flexible substrate by means of two‐photon polymerization using a Ti‐sapphire femtosecond laser focused into a liquid acrylate‐based resin containing a photoinitiator. Progenitor cells, differentiated into an osteogenic lineage by the use of medium supplemented with biochemical stimuli, can be seeded on to the hydrophilic three‐dimensional scaffolds. Due to confinement to the microstructures and/or mechanical interaction with the scaffold, the cells are stimulated to produce high amounts of calcium‐binding proteins, such as collagen type I, and show an increased activation of the actin cytoskeleton. The best results were obtained for quadratic pore sizes of 35 µm: the pore volumes become almost filled with both cells in close contact with the walls of the structure and with extracellular matrix material produced by the cells. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 891–899, 2017.

Triple Staining Including FOXA2 Identifies Stem Cell Lineages Undergoing Hepatic and Biliary Differentiation in Cirrhotic Human Liver

Recent investigations have reported many markers associated with human liver stem/progenitor cells, "oval cells," and identified "niches" in diseased livers where stem cells occur. However, there has remained a need to identify entire lineages of stem cells as they differentiate into bile ducts or hepatocytes. We have used combined immunohistochemical staining for a marker of hepatic commitment and specification (FOXA2 [Forkhead box A2]), hepatocyte maturation (Albumin and HepPar1), and features of bile ducts (CK19 [cytokeratin 19]) to identify lineages of stem cells differentiating toward the hepatocytic or bile ductular compartments of end-stage cirrhotic human liver. We identified large clusters of disorganized, FOXA2 expressing, oval cells in localized liver regions surrounded by fibrotic matrix, designated as "micro-niches." Specific FOXA2-positive cells within the micro-niches organize into primitive duct structures that support both hepatocytic and bile ductular differentiation enabling identification of entire lineages of cells forming the two types of structures. We also detected expression of hsa-miR-122 in primitive ductular reactions expected for hepatocytic differentiation and hsa-miR-23b cluster expression that drives liver cell fate decisions in cells undergoing lineage commitment. Our data establish the foundation for a mechanistic hypothesis on how stem cell lineages progress in specialized micro-niches in cirrhotic end-stage liver disease.

Regulatory System for Stem/Progenitor Cell Niches in the Adult Rodent Pituitary

The anterior lobe of the pituitary gland is a master endocrine tissue composed of five types of endocrine cells. Although the turnover rate of pituitary endocrine cells is as low as about 1.6% per day, recent studies have demonstrated that Sex-determining region Y-box 2 (SOX2)⁺-cells exist as pituitary stem/progenitor cells in the adult anterior lobe and contribute to cell regeneration. Notably, SOX2⁺-pituitary stem/progenitor cells form two types of niches in this tissue: the marginal cell layer (MCL-niche) and the dense cell clusters scattering in the parenchyma (parenchymal-niche). However, little is known about the mechanisms and factors for regulating the pituitary stem/progenitor cell niches, as well as the functional differences between the two types of niches. Elucidation of the regulatory mechanisms in the niches might enable us to understand the cell regeneration system that acts in accordance with physiological demands in the adult pituitary. In this review, so as to reveal the regulatory mechanisms of the two types of niche, we summarize the regulatory factors and their roles in the adult rodent pituitary niches by focusing on three components: soluble factors, cell surface proteins and extracellular matrixes.

Identification of Different Classes of Luminal Progenitor Cells within Prostate Tumors

Primary prostate cancer almost always has a luminal phenotype. However, little is known about the stem/progenitor properties of transformed cells within tumors. Using the aggressive Pten/Tp53-null mouse model of prostate cancer, we show that two classes of luminal progenitors exist within a tumor. Not only did tumors contain previously described multipotent progenitors, but also a major population of committed luminal progenitors. Luminal cells, sorted directly from tumors or grown as organoids, initiated tumors of adenocarcinoma or multilineage histological phenotypes, which is consistent with luminal and multipotent differentiation potentials, respectively. Moreover, using organoids we show that the ability of luminal-committed progenitors to self-renew is a tumor-specific property, absent in benign luminal cells. Finally, a significant fraction of luminal progenitors survived in vivo castration. In all, these data reveal two luminal tumor populations with different stem/progenitor cell capacities, providing insight into prostate cancer cells that initiate tumors and can influence treatment response.

Point-of-care seeding of nitinol stents with blood-derived endothelial cells

Nitinol-based vascular devices, for example, peripheral and intracranial stents, are limited by thrombosis and restenosis. To ameliorate these complications, we developed a technology to promote vessel healing by rapidly seeding (QuickSeeding) autologous blood-derived endothelial cells (ECs) onto modified self-expanding nitinol stent delivery systems immediately before implantation. Several thousand micropores were laser-drilled into a delivery system sheath surrounding a commercial nitinol stent to allow for exit of an infused cell suspension. As suspension medium flowed outward through the micropores, ECs flowed through the delivery system attaching to the stent surface. The QuickSeeded ECs adhered to and spread on the stent surface following 24-h in vitro culture under static or flow conditions. Further, QuickSeeded ECs on stents that were deployed into porcine carotid arteries spread to endothelialize stent struts within 48 h (n = 4). The QuickSeeded stent struts produced significantly more nitric oxide in ex vivo flow circuits after 24 h, as compared to static conditions (n = 5). In conclusion, ECs QuickSeeded onto commercial nitinol stents within minutes of implantation spread to form a functional layer in vitro and in vivo, providing proof of concept that the novel QuickSeeding method with modified delivery systems can be used to seed functional autologous endothelium at the point of care. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1658-1665, 2016.

Endometrial side population cells: potential adult stem/progenitor cells in endometrium

Uterine endometrium is one of the most important organs for species preservation. However, the physiology of human endometrium remains poorly understood, because the human endometrium undergoes rapid and large changes during each menstrual cycle and it is very difficult to investigate human endometrium as one organ. This remarkable regenerative capacity of human endometrium strongly suggests the existence of adult stem cells, and physiology of endometrium cannot be explained without adult stem cells. Therefore, investigating endometrial stem/progenitor cells should lead to a breakthrough in understanding the normal endometrial physiology and the pathophysiology of endometrial neoplastic disorders, such as endometriosis and endometrial cancer. Several cell populations have been discovered as putative endometrial stem/progenitor cells. Emerging evidence reveals that the endometrial side population (SP) is one of the potential endometrial stem/progenitor populations. Of all the endometrial stem/progenitor cell candidates, the endometrial SP (ESP) is best investigated in vitro and in vivo, and has the largest number of references. In this review, we provide an overview of the accumulating evidence for the ESP cells, both directly from human endometria and from cultured endometrial cells. Furthermore, SP cells are compared to other potential stem/progenitor cells, and we discuss their stem cell properties. We also discuss the difficulties and unsolved issues in endometrial stem cell biology.

Salivary Glands: Stem Cells, Self-duplication, or Both?

Understanding the intrinsic potential for renewal and regeneration within a tissue is critical for the rational design of reparative strategies. Maintenance of the salivary glands is widely thought to depend on the differentiation of stem cells. However, there is also new evidence that homeostasis of the salivary glands, like that of the liver and pancreas, relies on self-renewal of differentiated cells rather than a stem cell pool. Here, we review the evidence for both modes of turnover and consider the implications for the process of regeneration. We propose that the view of salivary glands as postmitotic and dependent on stem cells for renewal be revised to reflect the proliferative activity of acinar cells and their role in salivary gland homeostasis.

Dysregulation of the Bmi-1/p16(Ink⁴a) pathway provokes an aging-associated decline of submandibular gland function

Bmi-1 prevents stem cell aging, at least partly, by blocking expression of the cyclin-dependent kinase inhibitor p16(Ink4a) . Therefore, dysregulation of the Bmi-1/p16(Ink4a) pathway is considered key to the loss of tissue homeostasis and development of associated degenerative diseases during aging. However, because Bmi-1 knockout (KO) mice die within 20 weeks after birth, it is difficult to determine exactly where and when dysregulation of the Bmi-1/p16(Ink4a) pathway occurs during aging in vivo. Using real-time in vivo imaging of p16(Ink4a) expression in Bmi-1-KO mice, we uncovered a novel function of the Bmi-1/p16(Ink4a) pathway in controlling homeostasis of the submandibular glands (SMGs), which secrete saliva into the oral cavity. This pathway is dysregulated during aging in vivo, leading to induction of p16(Ink4a) expression and subsequent declined SMG function. These findings will advance our understanding of the molecular mechanisms underlying the aging-related decline of SMG function and associated salivary gland hypofunction, which is particularly problematic among the elderly.

In vitro characterization of stem/progenitor cells from semitendinosus and gracilis tendons as a possible new tool for cell-based therapy for tendon disorders

PURPOSE

this study was conducted to characterize tendon stem/progenitor cells (TSPCs) isolated from human semitendinosus and gracilis tendons in terms of stemness properties and multi-differentiation potential.

METHODS

TSPCs were isolated from waste portions of semitendinosus and gracilis tendons from three donors who underwent anterior cruciate ligament reconstruction. TSPCs were plated in culture until passage 4, when experiments to assess cell proliferation, viability and clonogenic ability were performed. The immunophenotype of TSPCs was evaluated by cytofluorimetric analysis. The in vitro osteogenic, chondrogenic, adipogenic and tenogenic potential was evaluated using biochemical, histological and gene expression analysis to detect specific differentiation markers. Statistical analysis was performed using Student's t-test.

RESULTS

after a few passages in culture the cell populations showed a homogeneous fibroblast-like morphology typical of mesenchymal stem cells. The average doubling time of TSPCs increased from 52.4±4.8 at passage 2 to 100.8±23.4 hours at passage 4. The highest percentage of colonies was also found at passage 4 (4.7±2.3%). TSPCs showed the typical mesenchymal phenotype, with high expression of CD73, CD90 and CD105 and no expression of CD34 and CD45. Cells induced to differentiate toward osteogenic lineage showed significant upregulations of ALP activity (+189%, p<0.05) and calcified matrix deposition (+49%, p<0.05) compared with undifferentiated cells; culture in chondrogenic medium also provoked a significant increase in glycosaminoglycan levels (+108%, p<0.05). On the other hand, TSPCs were not able to respond to adipogenic stimuli. Scleraxis gene expression and decorin gene expression, considered tenogenic markers, were already very high in control cells, and culture in tenogenic medium further increased these values although not significantly.

CONCLUSIONS

our data show that it is possible to isolate TSPCs from very small fragments of tissue and that they show the typical features of MSCs and multi-differentiation potential, above all toward osteogenic and chondrogenic lineages.

CLINICAL RELEVANCE

this study can be considered one of the first attempts to clarify the biology of tendon cell populations, focusing in particular on the potential applicability of this cell source for future regenerative medicine purposes.

Distribution of slow-cycling cells in epiphyseal cartilage and requirement of β-catenin signaling for their maintenance in growth plate

Slow proliferation is one of the characteristics of stem cells. We examined the presence, distribution, and regulation of slow-cycling cells in the developing and growing skeleton using a pulse-chase method with a new nucleoside derivative, 5-ethynyl-2'-deoxyuridine (EdU). C57BL/6 mice received daily intraperitoneal injections of EdU from postnatal day 4 to day 7. One day after the last EdU injection, a large population of cells in articular cartilage and growth plate was labeled. Six weeks after the last injection, the number of EdU-labeled cells dramatically decreased, but a small number of them were dominantly present in the articular surface, and the labeling index was significantly higher in the surface than that in the rest of articular cartilage. In the growth plate, most EdU-positive cells were found in the top layer that lies immediately below the secondary ossification center. Interestingly, postnatal conditional ablation of β-catenin in cartilage caused a complete loss of the EdU-labeled cells in growth plate that displayed disorganization and dysfunction. Together, our data demonstrate that slow-cycling cells do reside in specific locations and numbers in both articular cartilage and growth plate. The β-catenin signaling pathway appears to play a previously unsuspected role in maintenance of the slow-cycling cells.

Quantitative analysis reveals dominance of gliogenesis over neurogenesis in an adult brainstem oscillator

Neural stem/progenitor cells in the neurogenic niches of the adult brain are widely assumed to give rise predominantly to neurons, rather than glia. Here, we performed a quantitative analysis of the resident neural progenitors and their progeny in the adult pacemaker nucleus (Pn) of the weakly electric fish Apteronotus leptorhynchus. Approximately 15% of all cells in this brainstem nucleus are radial glia-like neural stem/progenitor cells. They are distributed uniformly within the tissue and are characterized by the expression of Sox2 and Meis 1/2/3. Approximately 2-3% of them are mitotically active, as indicated by expression of proliferating cell nuclear antigen. Labeling of proliferating cells with a single pulse of BrdU, followed by chases of up to 100 days, revealed that new cells are generated uniformly throughout the nucleus and do not undergo substantial migration. New cells differentiate into S100+ astrocytes and Hu C/D+ small interneurons at a ratio of 4:1, reflecting the proportions of the total glia and neurons in this brain region. The continuous addition of new cells leads to a diffuse growth of the Pn, which doubles in volume and total cell number over the first 2 years following sexual maturation of the fish. However, the number of pacemaker and relay cells, which constitute the oscillatory neural network, remains constant throughout adult life. We hypothesize that the dominance of gliogenesis is an adaptation to the high-frequency firing of the oscillatory neurons in this nucleus.