A cytokinin response maximum induces and activates bifacial stem cells for radial growth.

Norway spruce is one of the most economically important coniferous species in Europe, but it has faced high mortality rates in the last few decades due to the increasing frequency of extreme weather events. Primary and secondary growth development may be affected by these non-optimal conditions. In this study, we aimed to analyze the timing, possible asynchrony and time-lag between the growth processes of Norway spruce. We used a novel methodological approach of primary (based on phenocamera picture evaluation) and secondary (dendrometers) growth detection. The combination of these novel approaches allowed us to compare these growth process in high temporal resolution. Measurements were performed in two experimental plots with contrasting climatic conditions (middle and higher elevations) in the years 2016–2019, during the presence of extreme climatic conditions. We demonstrated a significant elongation of the growing season, with a more pronounced effect at higher elevation. Compared to the long-term mean, we observed an additional 50 days with a temperature above 15 °C at the higher elevation plot. There were no found patterns in the time-shift of both growth processes between plots. On the other hand we observed asynchrony of radial growth and meristems growth. Radial growth began earlier than the phenology of apical meristems growth. The onset, end and duration of meristem growth differed between studied plots and years as well. The onset of radial growth did not follow the gradient of microclimatic parameters; however, the differences in climatic conditions between plots did cause a shift in the onset of meristem growth. The process of the radial growth was twice as long as for apical meristem development. On average, radial growth requires 71 days more than meristem phenology to reach full process completion. Our data confirmed that these growth processes are strongly affected by external weather conditions and the duration of the growing season. More advanced and detailed monitoring of these processes can provide more accurate data of the health status of trees in the forest.

Are transplantable stem cells required for adult hematopoiesis?

Arabidopsis root with its simple, consistent and well-defined pattern of cell division and growth is a highly tractable system for studying cellular development. The root apical meristem (RAM) of Arabidopsis, established post-embryonically is the main source of root cells. Complex bidirectional signaling between stem cells and mature root cells is required to maintain RAM activity. The Arabidopsis RAM comprises of a quiescent center (QC) and a niche of self-renewing stem cells that perform asymmetric (formative) cell divisions to generate daughter cells. These daughter cells subsequently divide symmetrically within delineated longitudinal cell files. The cells in the QC coordinate with neighboring stem cells to establish the balance between proliferation and differentiation in the meristem niche. The Arabidopsis primary root is composed of concentric rings of tissues (namely, the epidermis, the cortex, the endodermis and the pericycle, from the outside inwards) arranged in a radial axis that surrounds a central cylinder of vascular and procambial cells. Overlaid upon the radial organization of the root are three longitudinal zones viz, the meristem, the elongation zone and the differentiation zone, that describe cellular behavior. The boundaries of these domains are plastic and are largely regulated by antagonistic interactions between different phyto-hormones, which regulate the expression of key TFs. In this paper, we review the process of radial patterning in Arabidopsis thaliana post-embryonic root with an emphasis on genetic and molecular networks that determine the fate of each domain in the root.

Targeted Gene Modification of Hematopoietic Progenitor Cells in Mice Following Systemic Administration of a PNA-peptide Conjugate

Embryonic stem (ES) cell lines constitute a special class of cell lines derived from the inner cell masses of preimplantation embryos. They are special owing to their unique capability of self renewal and differentiation and propagation in culture for indefinite periods of time. Unlike cancerous cells, they main t ain stable chromosomal content and have potential to diffe r entiate into any of the 200 cell type, under appropriate culture conditions. Embryonic stem cell research has gained a tremendous momentum owing to their promises and hopes in regenerative medicine, stem cell therapy, biopharming, and usefulness as in vitro models for studying embryonic develop m ent and differen t iation. ES cell research in farm animals provides strong incentives for precise genetic mani p ulation for better health, increased disease resistance, increased milk production and desired composition, increased growth rate with improved carcass composition, enhanced reproductive perfor m ance and prolificacy. The potential benefits of using ES cells as donor cells in somatic cell nuclear transfer would boost transgenic animal production. However, with all the promises and hopes, need for more rigorous research and evidence-based therapy is the need of the time, before we could successfully embark on exploitation of ES cells in regenerative medicine. In the current review, establishment, charac t erization, applications and future challenges of farm animal ES cells are discussed in detail with a special focus on bubaline ES cell lines.

Quiescence regulators for hematopoietic stem cell

Plants exhibit opportunistic developmental patterns, alternating between growth and dormancy in response to external cues. Moreover, quiescence plays a critical role in proper plant growth and development, particularly within the root apical meristem and the shoot apical meristem. In these meristematic tissues, cells with relatively slower mitotic activity are present in the quiescent center and the central zone, respectively. These centers form long-term reservoirs of stem cells maintaining the meristematic stem cell niche, and thus sustaining continuous plant development and adaptation to changing environments. This review explores early observations, structural characteristics, functions, and gene regulatory networks of the root and shoot apical meristems. It also highlights the intricate mechanism of dormancy within the shoot apical meristem. The aim is to contribute to a holistic understanding of quiescence in plants, which is fundamental for the proper growth and environmental response of plants.

The post-embryonic growth of plants requires the activities of apical meristems and lateral meristems. In the meristems, self-proliferation and differentiation of stem cells is tightly modulated by plant hormone signaling networks and specific transcription factors. Despite extensive studies on stem cell maintenance in plants, the mechanism by which stem cells are initially established is largely unknown. Vascular stem cells consisting of procambial/cambial cells give rise to xylem and phloem cells. In this study, we analyzed the establishment of procambial cells using the invitro culture system VISUAL, in which mesophyll cells rapidly differentiate into xylem tracheary elements and phloem sieve elements via procambial cells. We found that procambial cell formation in VISUAL is initiated by light, which can be replaced by application of gibberellin (GA). Gibberellin was able to promote procambial cell formation through degradation of DELLA, whereas light did not elevate the endogenous GA content. Indeed, light in combination with bikinin reduced the accumulation of DELLA protein in VISUAL. Consistently, overexpression of a constitutively active DELLA protein repressed vascular cell differentiation even under light. These combined results suggest that DELLA signaling suppresses procambial cell formation during vascular development in VISUAL.

Treatment of extensive bone defects requires autologous bone grafting or implantation of bone substitute materials. An attractive alternative has been to engineer fully viable, biological bone grafts in vitro by culturing osteogenic cells within three-dimensional scaffolds, under conditions supporting bone formation. Such grafts could be used for implantation, but also as physiologically relevant models in basic and translational studies of bone development, disease and drug discovery. A source of human cells that can be derived in large numbers from a small initial harvest and predictably differentiated into bone forming cells is critically important for engineering human bone grafts. We discuss the characteristics and limitations of various types of human embryonic and adult stem cells, and their utility for bone tissue engineering.

Challenging environment of space causes several pivotal alterations in living systems, especially due to microgravity. The possibility of simulating microgravity by ground-based systems provides research opportunities that may lead to the understanding of in vitro biological effects of microgravity by eliminating the challenges inherent to spaceflight experiments. Stem cells are one of the most prominent cell types, due to their self-renewal and differentiation capabilities. Research on stem cells under simulated microgravity has generated many important findings, enlightening the impact of microgravity on molecular and cellular processes of stem cells with varying potencies. Simulation techniques including clinostat, random positioning machine, rotating wall vessel and magnetic levitation-based systems have improved our knowledge on the effects of microgravity on morphology, migration, proliferation and differentiation of stem cells. Clarification of the mechanisms underlying such changes offers exciting potential for various applications such as identification of putative therapeutic targets to modulate stem cell function and stem cell based regenerative medicine.

Epithelial and Mesenchymal Contribution to the Niche: A Safeguard for Intestinal Stem Cell Homeostasis

SUMMARYPlant stem cells in the shoot apical meristem (SAM) and root apical meristem (RAM) provide for postembryonic development of above-ground tissues and roots, respectively, while secondary vascular stem cells sustain vascular development1–4. WUSCHEL (WUS), a homeodomain transcription factor expressed in the rib meristem of the SAM, is a key regulatory factor controlling stem cell populations in the Arabidopsis SAM5–6 and is thought to establish the shoot stem cell niche via a feedback circuit with the CLAVATA3 (CLV3) peptide signaling pathway7. WUSCHEL-RELATED HOMEOBOX5 (WOX5), specifically expressed in root quiescent center (QC), defines QC identity and functions interchangeably with WUS in control of shoot and root stem cell niches8. WOX4, expressed in Arabidopsis procambial cells, defines the vascular stem cell niche9–11. WUS/WOX family proteins are evolutionarily and functionally conserved throughout the plant kingdom12 and emerge as key actors in the specification and maintenance of stem cells within all meristems13. However, the nature of the genetic regime in stem cell niches that centers on WOX gene function has been elusive, and molecular links underlying conserved WUS/WOX function in stem cell niches remain unknown. Here we demonstrate that the Arabidopsis HAIRY MERISTEM (HAM)family transcription regulators act as conserved interacting co-factors with WUS/WOX proteins. HAM and WUS share common targets in vivo and their physical interaction is important in driving downstream transcriptional programs and in promoting shoot stem cell proliferation. Differences in the overlapping expression patterns of WOX and HAM family members underlie the formation of diverse stem cell niche locations, and the HAM family is essential for all of these stem cell niches. These findings establish a new framework for the control of stem cell production during plant development.

Plant stem cell cultures have so far been established in only a few plant species using cambial meristematic cells. The presence of stem cells or stem cell-like cells in other organs and tissues of the plant body, as well as the possibility of de novo generation of meristematic cells from differentiated cells, allow to consider the establishment of stem cell cultures in a broader range of species. This study aimed to establish a stem cell culture of the medicinal plant Calendula officinalis L. Callus tissues were induced from leaf and root explants, and already at this stage, stem and dedifferentiated cells could be identified. The cell suspension cultures established both from the root- and leaf-derived calli contained a high proportion of stem cells (92–93% and 72–73%, respectively). The most effective combination of growth regulators for the development of stem cells in calli as well as cell cultures was 1.0 mg/L 2,4-D and 0.5 mg/L BAP. The highest amount of stem cells (5.60–5.72 × 105) was in cell suspension derived from the roots. An effective protocol for the establishment of marigold stem cell suspension culture was developed. The ratio of root-derived stem cells against dedifferentiated cells exceeded 90%.

Background Mesenchymal stem cells (MSCs) are multipotent cells with self-renewal and differentiation capabilities, making them promising candidates for regenerative medicine. Iliac crest stem cells are a widely used source of MSCs valued for their accessibility, estrogenic potential, and established role in bone regeneration and repair studies. The human mandibular bone marrow (hMBM) is a readily accessible and potentially rich source of MSCs, particularly valuable in orofacial and craniofacial reconstruction. Purpose This study aimed to isolate and characterize MSCs from hMBM. The isolation of hMBM-derived MSCs serves multiple purposes, including fundamental research in craniofacial biology and pathology, regenerative medicine, disease modeling, and personalized cell-based therapies. Methods While bone marrow-derived stem cells from the iliac crest are widely used for autologous transplantation and bone repair, MSCs from the human mandible have not been extensively explored for regenerative applications. Given the availability of mandibular bone marrow (MBM) during oral and maxillofacial procedures, this study investigated the osteogenic and chondrogenic potential of human mandibular mesenchymal stem cells (hMMSCs) in vitro. Results The isolated hMMSCs expressed characteristic MSC surface markers (CD90, CD105, and CD73), exhibited colony-forming ability, and demonstrated tri-lineage differentiation potential. Notably, hMMSCs showed a strong capacity to differentiate into osteoblasts, which surpassed their chondrogenic potential. Conclusion hMBM is a viable source of MSCs with significant osteogenic potential. These findings support the potential application of hMMSCs in bone regeneration and mandibular repair strategies. Our data thus exhibits for the first time that hMMSCs are a reliable cell source for mandibular tissue engineering.

Stem cells self-renew and produce precursor cells that differentiate to become specialized cell types. Land plants generate several types of stem cells that give rise to most organs of the plant body and whose characters determine the body organization. The moss Physcomitrella patens forms eight types of stem cells throughout its life cycle. Under gametangium-inducing conditions, multiple antheridium apical stem cells are formed at the tip of the gametophore and each antheridium apical stem cell divides to form an antheridium. We found that the gametophore apical stem cell, which typically forms leaf and stem tissues, changes to become a new type of stem cell, which we term the antheridium initial stem cell. This antheridium initial stem cell produces multiple antheridium apical stem cells, resulting in a cluster of antheridia at the tip of gametophore. This is the first report of a land plant stem cell directly producing another type of stem cell during normal development. Notably, the antheridium apical stem cells are distally produced from the antheridium initial stem cell, similar to the root cap stem cells of vascular plants, suggesting the use of similar molecular mechanisms and a possible evolutionary relationship.This article is part of a discussion meeting issue 'The Rhynie cherts: our earliest terrestrial ecosystem revisited'.