In vivo clonal tracking of hematopoietic stem and progenitor cells marked by five fluorescent proteins using confocal and multiphoton microscopy

The site of breast cancer metastases dictates their clonal composition and reversible transcriptomic profile

Intratumoral heterogeneity is a driver of breast cancer progression, but the nature of the clonal interactive network involved in this process remains unclear. Here, we optimized the use of optical barcoding to visualize and characterize 31 cancer subclones in vivo. By mapping the clonal composition of thousands of metastases in two clinically relevant sites, the lungs and liver, we found that metastases were highly polyclonal in lungs but not in the liver. Furthermore, the transcriptome of the subclones varied according to their metastatic niche. We also identified a reversible niche-driven signature that was conserved in lung and liver metastases collected during patient autopsies. Among this signature, we found that the tumor necrosis factor-α pathway was up-regulated in lung compared to liver metastases, and inhibition of this pathway affected metastasis diversity. These results highlight that the cellular and molecular heterogeneity observed in metastases is largely dictated by the tumor microenvironment.

Tissue-Resident PDGFRα+ Progenitor Cells Contribute to Fibrosis versus Healing in a Context- and Spatiotemporally Dependent Manner

PDGFRα⁺ mesenchymal progenitor cells are associated with pathological fibro-adipogenic processes. Conversely, a beneficial role for these cells during homeostasis or in response to revascularization and regeneration stimuli is suggested, but remains to be defined. We studied the molecular profile and function of PDGFRα⁺ cells in order to understand the mechanisms underlying their role in fibrosis versus regeneration. We show that PDGFRα⁺ cells are essential for tissue revascularization and restructuring through injury-stimulated remodeling of stromal and vascular components, context-dependent clonal expansion, and ultimate removal of pro-fibrotic PDGFRα⁺-derived cells. Tissue ischemia modulates the PDGFRα⁺ phenotype toward cells capable of remodeling the extracellular matrix and inducing cell-cell and cell-matrix adhesion, likely favoring tissue repair. Conversely, pathological healing occurs if PDGFRα⁺-derived cells persist as terminally differentiated mesenchymal cells. These studies support a context-dependent "yin-yang" biology of tissue-resident mesenchymal progenitor cells, which possess an innate ability to limit injury expansion while also promoting fibrosis in an unfavorable environment.

Definitive hematopoietic stem/progenitor cells from human embryonic stem cells through serum/feeder-free organoid-induced differentiation

Background

Ex vivo production of hematopoietic stem/precursor cells (HSPCs) represents a promising versatile approach for blood disorders.

Methods

To derive definitive HSPCs from human embryonic stem cells (ESCs), we differentiated mesodermally specified embryoid bodies (EBs) on gelatin-coated plates in serum/feeder-free conditions.

Results

Seven-day EB maturation followed by an 8-day differentiation period on OP9 cells provided the highest number of definitive (CD34+ CD235a−, 69%, p < 0.01) and lowest number of primitive (CD34− CD235a+, 1.55%, p < 0.01) precursor cells along with the highest colony-forming units (149.8 ± 11.6, p < 0.01) in feeder-free conditions. Maximal HSPC fraction (CD34+ CD38− CD45RA− CD49f+ CD90+) was 7.6–8.9% after 10 days of hematopoietic differentiation with 14.5% adult β-globin expression following RBC differentiation. Myeloid and erythroid colonies were restricted strictly to the CD34+ CD43+ fraction (370.5 ± 65.7, p < 0.001), while the CD34− CD43+ fraction produced only a small number of colonies (21.6 ± 11.9). In addition, we differentiated the CD34+ CD43+ cells towards T-lymphocytes using the OP9/DLL1 co-culture system demonstrating double-positive T cells (CD4+ CD8+) with CD3+ expression displaying a broad T cell receptor (TCR) repertoire. Confocal imaging of organoid-like structures revealed a close association of CD31+ cells with CD34+ and CD43+ cells, suggesting a potential emergence of HSPCs through endothelial to hematopoietic transition. Furthermore, fluorescently labeled organoids exhibited the emergence of spherical non-attached cells from rare progenitors at the border of the organoid center.

Conclusions

In summary, definitive HSPCs can be derived from ESCs through a dynamic cellular process from an organoid-like structure, where erythroid progeny are capable of producing adult hemoglobin and lymphoid progeny shows a diverse TCR repertoire.

Advances in Pluripotent Stem Cells: History, Mechanisms, Technologies, and Applications

Over the past 20 years, and particularly in the last decade, significant developmental milestones have driven basic, translational, and clinical advances in the field of stem cell and regenerative medicine. In this article, we provide a systemic overview of the major recent discoveries in this exciting and rapidly developing field. We begin by discussing experimental advances in the generation and differentiation of pluripotent stem cells (PSCs), next moving to the maintenance of stem cells in different culture types, and finishing with a discussion of three-dimensional (3D) cell technology and future stem cell applications. Specifically, we highlight the following crucial domains: 1) sources of pluripotent cells; 2) next-generation in vivo direct reprogramming technology; 3) cell types derived from PSCs and the influence of genetic memory; 4) induction of pluripotency with genomic modifications; 5) construction of vectors with reprogramming factor combinations; 6) enhancing pluripotency with small molecules and genetic signaling pathways; 7) induction of cell reprogramming by RNA signaling; 8) induction and enhancement of pluripotency with chemicals; 9) maintenance of pluripotency and genomic stability in induced pluripotent stem cells (iPSCs); 10) feeder-free and xenon-free culture environments; 11) biomaterial applications in stem cell biology; 12) three-dimensional (3D) cell technology; 13) 3D bioprinting; 14) downstream stem cell applications; and 15) current ethical issues in stem cell and regenerative medicine. This review, encompassing the fundamental concepts of regenerative medicine, is intended to provide a comprehensive portrait of important progress in stem cell research and development. Innovative technologies and real-world applications are emphasized for readers interested in the exciting, promising, and challenging field of stem cells and those seeking guidance in planning future research direction.

Advances, challenges and future directions for stem cell therapy in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive neurodegenerative condition where loss of motor neurons within the brain and spinal cord leads to muscle atrophy, weakness, paralysis and ultimately death within 3–5 years from onset of symptoms. The specific molecular mechanisms underlying the disease pathology are not fully understood and neuroprotective treatment options are minimally effective.

In recent years, stem cell transplantation as a new therapy for ALS patients has been extensively investigated, becoming an intense and debated field of study. In several preclinical studies using the SOD1^G93A mouse model of ALS, stem cells were demonstrated to be neuroprotective, effectively delayed disease onset and extended survival. Despite substantial improvements in stem cell technology and promising results in preclinical studies, several questions still remain unanswered, such as the identification of the most suitable and beneficial cell source, cell dose, route of delivery and therapeutic mechanisms. This review will cover publications in this field and comprehensively discuss advances, challenges and future direction regarding the therapeutic potential of stem cells in ALS, with a focus on mesenchymal stem cells. In summary, given their high proliferation activity, immunomodulation, multi-differentiation potential, and the capacity to secrete neuroprotective factors, adult mesenchymal stem cells represent a promising candidate for clinical translation. However, technical hurdles such as optimal dose, differentiation state, route of administration, and the underlying potential therapeutic mechanisms still need to be assessed.

Intravital longitudinal wide-area imaging of dynamic bone marrow engraftment and multilineage differentiation through nuclear-cytoplasmic labeling

Bone marrow is a vital tissue that produces the majority of erythrocytes, thrombocytes, and immune cells. Bone marrow transplantation (BMT) has been widely performed in patients with blood disorders and cancers. However, the cellular-level behaviors of the transplanted bone marrow cells over wide-areas of the host bone marrow after the BMT are not fully understood yet. In this work, we performed a longitudinal wide-area cellular-level observation of the calvarial bone marrow after the BMT in vivo. Using a H2B-GFP/β-actin-DsRed double-transgenic mouse model as a donor, a subcellular-level nuclear-cytoplasmic visualization of the transplanted bone marrow cells was achieved, which enabled a direct in vivo dynamic monitoring of the distribution and proliferation of the transplanted bone marrow cells. The same spots in the wide-area of the calvarial bone marrow were repeatedly identified using fluorescently labeled vasculature as a distinct landmark. It revealed various dynamic cellular-level behaviors of the transplanted BM cells in early stage such as cluster formation, migration, and active proliferation in vivo.