The intestinal epithelial-macrophage-crypt stem cell axis plays a crucial role in regulating and maintaining intestinal homeostasis

The intestinal tract plays a vital role in both digestion and immunity, making its equilibrium crucial for overall health. This equilibrium relies on the dynamic interplay among intestinal epithelial cells, macrophages, and crypt stem cells. Intestinal epithelial cells play a pivotal role in protecting and regulating the gut. They form vital barriers, modulate immune responses, and engage in pathogen defense and cytokine secretion. Moreover, they supervise the regulation of intestinal stem cells. Macrophages, serving as immune cells, actively influence the immune response through the phagocytosis of pathogens and the release of cytokines. They also contribute to regulating intestinal stem cells. Stem cells, known for their self-renewal and differentiation abilities, play a vital role in repairing damaged intestinal epithelium and maintaining homeostasis. Although research has primarily concentrated on the connections between epithelial and stem cells, interactions with macrophages have been less explored. This review aims to fill this gap by exploring the roles of the intestinal epithelial-macrophage-crypt stem cell axis in maintaining intestinal balance. It seeks to unravel the intricate dynamics and regulatory mechanisms among these essential players. A comprehensive understanding of these cell types' functions and interactions promises insights into intestinal homeostasis regulation. Moreover, it holds potential for innovative approaches to manage conditions like radiation-induced intestinal injury, inflammatory bowel disease, and related diseases.

Stress stimulation promotes the injury repair process of airway epithelial cells through the [Cl-]i-FAK signaling axis

The airway epithelium serves as a critical interface with the external environment, making it vulnerable to various external stimuli. Airway epithelial stress acts as a catalyst for the onset of numerous pulmonary and systemic diseases. Our previous studies have highlighted the impact of acute stress stimuli, especially bacterial lipopolysaccharide (LPS) and hydrogen peroxide (H2O2), on the continuous elevation of intracellular chloride concentration ([Cl-]i). However, the precise mechanism behind this [Cl-]i elevation and the consequential effects of such stress on the injury repair function of airway epithelial cells remain unclear. Our findings indicate that H2O2 induces an elevation in [Cl-]i by modulating the expression of CF transmembrane conductance regulator (CFTR) and Ca-activated transmembrane protein 16 A (TMEM16A) in airway epithelial cells (BEAS-2B), whereas LPS achieves this solely through CFTR. Subsequently, the elevated [Cl-]i level facilitated the injury repair process of airway epithelial cells by activating focal adhesion kinase (FAK). In summary, the [Cl-]i-FAK axis appears to play a promoting effect on the injury repair process triggered by stress stimulation. Furthermore, our findings suggest that abnormalities in the [Cl-]i-FAK signaling axis may play a crucial role in the pathogenesis of chronic airway diseases. Therefore, controlling the structure and function of airway epithelial barriers through the modulation of [Cl-]i holds promising prospects for future applications in managing and treating such conditions.

Endothelial progenitor cells in the host defense response

Extensive injury of endothelial cells in blood vasculature, especially in the microcirculatory system, frequently occurs in hosts suffering from sepsis and the accompanied systemic inflammation. Pathological factors, including toxic components derived from invading microbes, oxidative stress associated with tissue ischemia/reperfusion, and vessel active mediators generated during the inflammatory response, are known to play important roles in mediating endothelial injury. Collapse of microcirculation and tissue edema developed from the failure of endothelial barrier function in vital organ systems, including the lung, brain, and kidney, are detrimental, which often predict fatal outcomes. The host body possesses a substantial capacity for maintaining vascular homeostasis and repairing endothelial damage. Bone marrow and vascular wall niches house endothelial progenitor cells (EPCs). In response to septic challenges, EPCs in their niche environment are rapidly activated for proliferation and angiogenic differentiation. In the meantime, release of EPCs from their niches into the blood stream and homing of these vascular precursors to tissue sites of injury are markedly increased. The recruited EPCs actively participate in host defense against endothelial injury and repair of damage in blood vasculature via direct differentiation into endothelial cells for re-endothelialization as well as production of vessel active mediators to exert paracrine and autocrine effects on angiogenesis/vasculogenesis. In recent years, investigations on significance of EPCs in host defense and molecular signaling mechanisms underlying regulation of the EPC response have achieved substantial progress, which promotes exploration of vascular precursor cell-based approaches for effective prevention and treatment of sepsis-induced vascular injury as well as vital organ system failure.

Applications of tetrahedral DNA nanostructures in wound repair and tissue regeneration

Tetrahedral DNA nanostructures (TDNs) are molecules with a pyramidal structure formed by folding four single strands of DNA based on the principle of base pairing. Although DNA has polyanionic properties, the special spatial structure of TDNs allows them to penetrate the cell membrane without the aid of transfection agents in a caveolin-dependent manner and enables them to participate in the regulation of cellular processes without obvious toxic side effects. Because of their stable spatial structure, TDNs resist the limitations imposed by nuclease activity and innate immune responses to DNA. In addition, TDNs have good editability and biocompatibility, giving them great advantages for biomedical applications. Previous studies have found that TDNs have a variety of biological properties, including promoting cell migration, proliferation and differentiation, as well as having anti-inflammatory, antioxidant, anti-infective and immune regulation capabilities. Moreover, we confirmed that TDNs can promote the regeneration and repair of skin, blood vessels, muscles and bone tissues. Based on these findings, we believe that TDNs have broad prospects for application in wound repair and regeneration. This article reviews recent progress in TDN research and its applications.

Gli1+ Mesenchymal Stem Cells in Bone and Teeth

Mesenchymal stem cells (MSCs) are remarkable and noteworthy. Identification of markers for MSCs enables the study of their niche in vivo. It has been identified that glioma-associated oncogene 1 positive (Gli1+) cells are mesenchymal stem cells supporting homeostasis and injury repair, especially in the skeletal system and teeth. This review outlines the role of Gli1+ cells as an MSC subpopulation in both bones and teeth, suggesting the prospects of Gli1+ cells in stem cell-based tissue engineering.

Enhanced BMP signalling causes growth plate cartilage dysrepair in rats

Growth plate cartilage injuries often result in bony repair at the injury site and premature mineralisation at the uninjured region causing bone growth defects, for which underlying mechanisms are unclear. With the prior microarray study showing upregulated bone morphogenetic protein (BMP) signalling during the injury site bony repair and with the known roles of BMP signalling in bone healing and growth plate endochondral ossification, this study used a rat tibial growth plate drill-hole injury model with or without systemic infusion of BMP antagonist noggin to investigate roles of BMP signalling in injury repair responses within the injury site and in the adjacent "uninjured" cartilage. At days 8, 14 and 35 post-injury, increased expression of BMP members and receptors and enhanced BMP signalling (increased levels of phosphorylated (p)-Smad1/5/8) were found during injury site bony repair. After noggin treatment, injury site bony repair at days 8 and 14 was reduced as shown by micro-CT and histological analyses and lower mRNA expression of osteogenesis-related genes Runx2 and osteocalcin (by RT-PCR). At the adjacent uninjured cartilage, the injury caused increases in the hypertrophic zone/proliferative zone height ratio and in mRNA expression of hypertrophy marker collagen-10, but a decrease in chondrogenesis marker Sox9 at days 14 and/or 35, which were accompanied by increased BMP signalling (increased levels of pSmad1/5/8 protein and BMP7, BMPR1a and target gene Dlx5 mRNA). Noggin treatment reduced the hypertrophic zone/proliferative zone height ratio and collagen-10 mRNA expression, but increased collagen-2 mRNA levels at the adjacent growth plate. This study has identified critical roles of BMP signalling in the injury site bony repair and in the hypertrophic degeneration of the adjacent growth plate in a growth plate drill-hole repair model. Moreover, suppressing BMP signalling can potentially attenuate the undesirable bony repair at injury site and suppress the premature hypertrophy but potentially rescue chondrogenesis at the adjacent growth plate.

Macrophage function in the elderly and impact on injury repair and cancer

Older age is associated with deteriorating health, including escalating risk of diseases such as cancer, and a diminished ability to repair following injury. This rise in age-related diseases/co-morbidities is associated with changes to immune function, including in myeloid cells, and is related to immunosenescence. Immunosenescence reflects age-related changes associated with immune dysfunction and is accompanied by low-grade chronic inflammation or inflammageing. This is characterised by increased levels of circulating pro-inflammatory cytokines such as tumor necrosis factor (TNF), interleukin (IL)-1β and IL-6. However, in healthy ageing, there is a concomitant age-related escalation in anti-inflammatory cytokines such as transforming growth factor-β1 (TGF-β1) and IL-10, which may overcompensate to regulate the pro-inflammatory state. Key inflammatory cells, macrophages, play a role in cancer development and injury repair in young hosts, and we propose that their role in ageing in these scenarios may be more profound. Imbalanced pro- and anti-inflammatory factors during ageing may also have a significant influence on macrophage function and further impact the severity of age-related diseases in which macrophages are known to play a key role. In this brief review we summarise studies describing changes to inflammatory function of macrophages (from various tissues and across sexes) during healthy ageing. We also describe age-related diseases/co-morbidities where macrophages are known to play a key role, focussed on injury repair processes and cancer, plus comment briefly on strategies to correct for these age-related changes.

Multifunctional role of microRNAs in mesenchymal stem cell-derived exosomes in treatment of diseases

Mesenchymal stem cells can be replaced by exosomes for the treatment of inflammatory diseases, injury repair, degenerative diseases, and tumors. Exosomes are small vesicles rich in a variety of nucleic acids [including messenger RNA, Long non-coding RNA, microRNA (miRNA), and circular RNA], proteins, and lipids. Exosomes can be secreted by most cells in the human body and are known to play a key role in the communication of information and material transport between cells. Like exosomes, miRNAs were neglected before their role in various activities of organisms was discovered. Several studies have confirmed that miRNAs play a vital role within exosomes. This review focuses on the specific role of miRNAs in MSC-derived exosomes (MSC-exosomes) and the methods commonly used by researchers to study miRNAs in exosomes. Taken together, miRNAs from MSC-exosomes display immense potential and practical value, both in basic medicine and future clinical applications, in treating several diseases.

Regeneration of sciatic nerves by transplanted microvesicles of human neural stem cells derived from embryonic stem cells

Injured nerves cannot regenerate on their own, and a lack of engraftable human nerves has been a major obstacle in cell-based therapies for regenerating damaged nerves. A monolayer culture approach to obtain adherent neural stem cells from human embryonic stem cells (hESC-NSCs) was established, and the greatest number of stemness characteristics were achieved by the eighth generation of hESC-NSCs (P8 hESC-NSCs). To overcome deficits in cell therapy, we used microvesicles secreted from P8 hESC-NSCs (hESC-NSC-MVs) instead of entire hESC-NSCs. To investigate the therapeutic efficacy of hESC-NSC-MVs in vitro, hESC-NSC-MVs were cocultured with dorsal root ganglia to determine the length of axons. In vivo, we transected the sciatic nerve in SD rats and created a 5-mm gap. A sciatic nerve defect was bridged using a silicone tube filled with hESC-NSC-MVs (45 μg) in the MVs group, P8 hESC-NSCs (1 × 106 single cells) in the cell group and PBS in the control group. The hESC-NSC-MVs group showed better morphological recovery and a significantly greater number of regenerated axons than the hESC-NSCs group 12 weeks after nerve injury. These results indicated that the hESC-NSC-MVs group had the greatest ability to repair and reconstruct nerve structure and function. As a result, hESC-NSC-MVs may have potential for applications in the field of nerve regenerative repair.

Molecular and cellular mechanisms of tooth development, homeostasis and repair

The tooth provides an excellent system for deciphering the molecular mechanisms of organogenesis, and has thus been of longstanding interest to developmental and stem cell biologists studying embryonic morphogenesis and adult tissue renewal. In recent years, analyses of molecular signaling networks, together with new insights into cellular heterogeneity, have greatly improved our knowledge of the dynamic epithelial-mesenchymal interactions that take place during tooth development and homeostasis. Here, we review recent progress in the field of mammalian tooth morphogenesis and also discuss the mechanisms regulating stem cell-based dental tissue homeostasis, regeneration and repair. These exciting findings help to lay a foundation that will ultimately enable the application of fundamental research discoveries toward therapies to improve oral health.

The role of pulmonary mesenchymal cells in airway epithelium regeneration during injury repair

Background

The airways of mammalian lung are lined with highly specialized cell types that are the target of airborne toxicants and injury. Several epithelial cell types and bone marrow-derived mesenchymal stem cells have been identified to serve as stem cells during injury repair. However, the contributions of endogenous mesenchymal cells to recruitment, expansion or differentiation of stem cells, and repair and reestablishment of the normal composition of airway epithelium following injury have not been addressed.

Methods

The role of mouse pulmonary mesenchymal cells was investigated by lineage tracing using Dermo1-Cre; ROSA^mTmG mice. In experimental models of lung injury by lipopolysaccharide and naphthalene, GFP-labeled Dermo1⁺ mesenchymal cells were traced during injury repair. In vitro lung explant culture treated with or without lipopolysaccharide was also used to verify in vivo data.

Results

During injury repair, a subgroup of GFP-labeled Dermo1⁺ mesenchymal cells were found to contribute to normal repair of the airway epithelium and differentiated into Club cells, ciliated cells, and goblet cells. In Club cell-specific naphthalene injury model, the process of Dermo1⁺ stem cell regenerating epithelial cells was dissected. The Dermo1⁺ stem cells was migrated into the airway epithelium layer sooner after injury, and sequentially differentiated transitionally to epithelial stem cells, such as neuroendocrine cells, and finally to newly differentiated Club cells, ciliated cells, and goblet cells in injury repair.

Conclusion

In this study, a population of Dermo1⁺ mesenchymal stem cell was identified to serve as stem cells in airway epithelial cell regeneration during injury repair. The Dermo1⁺ mesenchymal stem cell differentiated into epithelial stem cells before reestablishing various epithelial cells. These findings have implications for understanding the regulation of lung repair and the potential for usage of mesenchymal stem cells in therapeutic strategies for lung diseases.

In Vivo MR Imaging of Dual MRI Reporter Genes and Deltex-1 Gene-modified Human Mesenchymal Stem Cells in the Treatment of Closed Penile Fracture

PURPOSE

The purpose of this study was to investigate the feasibility of dual magnetic resonance imaging (MRI) reporter genes, including ferritin heavy subunit (Fth) and transferrin receptor (TfR), which provide sufficient MRI contrast for in vivo MRI tracking, and the Deltex-1 (DTX1) gene, which promotes human mesenchymal stem cell (hMSC) differentiation to smooth muscle cells (SMCs), to treat closed penile fracture (CPF).

METHODS

Multi-gene co-expressing hMSCs were generated. The expression of mRNA and proteins was assessed, and the original biological properties of hMSCs were determined and compared. The intracellular uptake of iron was evaluated, and the ability to differentiate into SMCs was detected. Fifty rabbits with CPF were randomly transplanted with PBS, hMSCs, Fth-TfR-hMSCs, DTX1-hMSCs, and Fth-TfR-DTX1-hMSCs. In vivo MRI was performed to detect the distribution and migration of the grafted cells and healing progress of CPF, and the results were correlated with histology.

RESULTS

The mRNA and proteins of the multi-gene were highly expressed. The transgenes could not influence the original biological properties of hMSCs. The dual MRI reporter genes increased the iron accumulation capacity, and the DTX1 gene promoted hMSC differentiation into SMCs. The distribution and migration of the dual MRI reporter gene-modified hMSCs, and the healing state of CPF could be obviously detected by MRI and confirmed by histology.

CONCLUSION

The dual MRI reporter genes could provide sufficient MRI contrast, and the distribution and migration of MSCs could be detected in vivo. The DTX1 gene can promote MSC differentiation into SMCs for the treatment of CPF and effectively inhibit granulation tissue formation.

The Use of Low Level Laser Therapy (LLLT) For Musculoskeletal Pain

Pain is the most common reason for physician consultation in the United States. One out of three Americans is affected by chronic pain annually. The number one reason for missed work or school days is musculoskeletal pain. Currently accepted therapies consist of non-steroidal anti-inflammatory drugs, steroid injections, opiate pain medications and surgery, each of which carries their own specific risk profiles. What is needed are effective treatments for pain which have an acceptably low risk-profile. For over forty years, low level laser (light) therapy (LLLT) and LED (light emitting diode) therapy (also known as photobiomodulation) has been shown to reduce inflammation and edema, induce analgesia, and promote healing in a range of musculoskeletal pathologies. The purpose of this paper is to review the use of LLLT for pain, the biochemical mechanisms of action, the dose response curves, and how LLLT may be employed by orthopedic surgeons to improve outcomes and reduce adverse events. With the predicted epidemic of chronic pain in developed countries, it is imperative to validate cost-effective and safe techniques for managing painful conditions which would allow people to live active and productive lives. Moreover the acceptance of LLLT (which is currently being used by many specialties around the world) into the armamentarium of the American health care provider would allow for additional treatment options for patients. A new cost-effective therapy for pain could elevate quality of life while reducing financial strains.