Human circulating CD14+ monocytes as a source of progenitors that exhibit mesenchymal cell differentiation

Body Fluid-Derived Stem Cells: Powering Innovative, Less-Invasive Cell Therapies

Stem cell therapy offers significant promise for tissue regeneration and repair. Traditionally, bone marrow- and adipose-derived stem cells have served as primary sources, but their clinical use is limited by invasiveness and low cell yield. This review focuses on body fluid-derived stem cells as an emerging, non-invasive, and readily accessible alternative. We examine stem cells isolated from amniotic fluid, peripheral blood, cord blood, menstrual fluid, urine, synovial fluid, breast milk, and cerebrospinal fluid, highlighting their unique biological properties and therapeutic potential. By comparing their characteristics and barriers to clinical translation, we propose body fluid-derived stem cells as a promising source for regenerative applications, with continued research needed to fully achieve their clinical utility.

Mesangiogenic progenitor cells: a mesengenic and vasculogenic branch of hemopoiesis? A story of neglected plasticity

Mesangiogenic progenitor cells (MPCs) are mesengenic and vasculogenic cells isolated from human bone marrow mononuclear cell cultures. Although MPCs were first described over two decades ago and have demonstrated promising differentiation capabilities, these cells did not attract sufficient attention from experts in the field of tissue regeneration. Several reports from the first decade of the 2000s showed MPC-like cells co-isolated in primary mesenchymal stromal cell (MSC) cultures, applying human serum. However, in most cases, these rounded and firmly attached cells were described as "contaminating" cells of hemopoietic origin. Indeed, MPC morphology, phenotype, and functional features evoke but do not completely overlap with those of cultured peripheral macrophages, and their hemopoietic origin should not be excluded. The plasticity of cells from the monocyte lineage is surprising but not completely unprecedented. Underestimated data demonstrated that circulating monocyte/macrophages could acquire broader plasticity under specific and different culture conditions, and this plasticity could be a consequence of in vitro de-differentiation. The evidence discussed here suggests that MPCs could represent the cell identity toward which the de-differentiation process reprograms the circulating mature phagocytic compartment.

Role of Circulating Monocytes and Periodontopathic Bacteria in Pathophysiology of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is characterized by chronic inflammation in the synovial membrane, leading to matrix destruction of cartilage and bone. While various types of immune cell are found in inflamed synovium in RA, macrophages and osteoclasts also play important roles in joint destruction. Peripheral blood monocytes migrate to synovial tissue and differentiate into macrophages and osteoclasts in RA. Synovial macrophages are classified into two subsets: M1 (proinflammatory macrophages) or M2 (anti-proinflammatory macrophages). Human circulating monocytes have also been divided into three subsets according expression level of CD14 and CD16: CD14+CD16- (classical); CD14brightCD16+ (intermediate); or CD14dimCD16+ (non-classical). Many recent studies have investigated the involvement of each subset of synovial macrophages and circulating monocytes in the pathophysiology of RA. On the other hand, several distinct human cell populations originating in circulating monocytes have the capacity to differentiate into non-phagocytic cells, including endothelial cells and adipocytes. This review summarizes the role of circulating monocytes in the pathophysiology of RA as precursor cells of not only phagocytes, such as macrophages and osteoclasts, but also non-phagocytes, such as endothelial cells and adipocytes. Furthermore, there is a growing body of evidence showing a significantly positive association between periodontopathic bacterial infection and the pathophysiology of RA. Therefore, the role of periodontopathic bacteria in the development of RA is also discussed.

Tumor microenvironment restricts IL-10 induced multipotent progenitors to myeloid-lymphatic phenotype

Lymphangiogenesis is induced by local pro-lymphatic growth factors and bone marrow (BM)-derived myeloid-lymphatic endothelial cell progenitors (M-LECP). We previously showed that M-LECP play a significant role in lymphangiogenesis and lymph node metastasis in clinical breast cancer (BC) and experimental BC models. We also showed that differentiation of mouse and human M-LECP can be induced through sequential activation of colony stimulating factor-1 (CSF-1) and Toll-like receptor-4 (TLR4) pathways. This treatment activates the autocrine interleukin-10 (IL-10) pathway that, in turn, induces myeloid immunosuppressive M2 phenotype along with lymphatic-specific proteins. Because IL-10 is implicated in differentiation of numerous lineages, we sought to determine whether this pathway specifically promotes the lymphatic phenotype or multipotent progenitors that can give rise to M-LECP among other lineages. Analyses of BM cells activated either by CSF-1/TLR4 ligands in vitro or orthotopic breast tumors in vivo showed expansion of stem/progenitor population and coincident upregulation of markers for at least four lineages including M2-macrophage, lymphatic endothelial, erythroid, and T-cells. Induction of cell plasticity and multipotency was IL-10 dependent as indicated by significant reduction of stem cell markers and those for multiple lineages in differentiated cells treated with anti-IL-10 receptor (IL-10R) antibody or derived from IL-10R knockout mice. However, multipotent CD11b+/Lyve-1+/Ter-119+/CD3e+ progenitors detected in BM appeared to split into a predominant myeloid-lymphatic fraction and minor subsets expressing erythroid and T-cell markers upon establishing tumor residence. Each sub-population was detected at a distinct intratumoral site. This study provides direct evidence for differences in maturation status between the BM progenitors and those reaching tumor destination. The study results suggest preferential tumor bias towards expansion of myeloid-lymphatic cells while underscoring the role of IL-10 in early BM production of multipotent progenitors that give rise to both hematopoietic and endothelial lineages.

Comparing stem cells, transdifferentiation and brain organoids as tools for psychiatric research

The inaccessibility of neurons coming directly from patients has hindered our understanding of mental illnesses at the cellular level. To overcome this obstacle, six different cellular approaches that carry the genetic vulnerability to psychiatric disorders are currently available: Olfactory Neuroepithelial Cells, Mesenchymal Stem Cells, Pluripotent Monocytes, Induced Pluripotent Stem Cells, Induced Neuronal cells and more recently Brain Organoids. Here we contrast advantages and disadvantages of each of these six cell-based methodologies. Neuronal-like cells derived from pluripotent monocytes are presented in more detail as this technique was recently used in psychiatry for the first time. Among the parameters used for comparison are; accessibility, need for reprograming, time to deliver differentiated cells, differentiation efficiency, reproducibility of results and cost. We provide a timeline on the discovery of these cell-based methodologies, but, our main goal is to assist researchers selecting which cellular approach is best suited for any given project. This manuscript also aims to help readers better interpret results from the published literature. With this goal in mind, we end our work with a discussion about the differences and similarities between cell-based techniques and postmortem research, the only currently available tools that allow the study of mental illness in neurons or neuronal-like cells coming directly from patients.

Osteoinduction and osteoimmunology: Emerging concepts

The recognition and importance of immune cells during bone regeneration, including around bone biomaterials, has led to the development of an entire field termed "osteoimmunology," which focuses on the connection and interplay between the skeletal system and immune cells. Most studies have focused on the "osteogenic" capacity of various types of bone biomaterials, and much less focus has been placed on immune cells despite being the first cell type in contact with implantable devices. Thus, the amount of literature generated to date on this topic makes it challenging to extract needed information. This review article serves as a guide highlighting advancements made in the field of osteoimmunology emphasizing the role of the osteoimmunomodulatory properties of biomaterials and their impact on osteoinduction. First, the various immune cell types involved in bone biomaterial integration are discussed, including the prominent role of osteal macrophages (OsteoMacs) during bone regeneration. Thereafter, key biomaterial properties, including topography, wettability, surface charge, and adsorption of cytokines, growth factors, ions, and other bioactive molecules, are discussed in terms of their impact on immune responses. These findings highlight and recognize the importance of the immune system and osteoimmunology, leading to a shift in the traditional models used to understand and evaluate biomaterials for bone regeneration.

<i>In vitro</i> production of myeloid-derived suppressor cells from peripheral blood monocytes

Myeloid-derived suppressor cells (MDSCs) are of interest as key regulators of the immune response for the development and improvement of cellular technologies in biomedicine. Enhancing the suppressive activity of these cells is important for developing therapies for autoimmune diseases and miscarriages, and their suppression may be useful in the treatment of cancer, since MDSCs are known to suppress antitumor immunity. However, there is a problem that prevents the active study of MDSCs, i.e., the difficulty in obtaining sufficient numbers of this cell population. Isolation of MDSCs in cancer patients poses an ethical challenge. Moreover, these MDSC may differ in subpopulation composition and suppressive activity due to individual factors. Researchers who generate human MDSC from bone marrow cells may also face similar problems. Therefore, finding a reliable and affordable source of these cells to facilitate the study of their functions is extremely important. Attempts to obtain human MDSCs in vitro have been ongoing for a long time. GM- CSF, IL-6, IL- 1β, IL-4, PGE2, LPS, M-CSF, IFNγ are described as factors that induce the ex vivo MDSC differentiation. However, despite multiple factors used, not all protocols are clearly reproducible, leading to generation of a sufficient number of cells in the target population. Previously, we had also developed a scheme for MDSC differentiation from CD11b+ cells derived from human peripheral blood, which made it possible to obtain a tangible but still insufficient percentage of cells to study functional activity. To increase the number of MDSCs in cultures, we developed a protocol aimed for differentiation of these cells from peripheral blood monocytes (CD14+ cells) previously transformed into PCMO (programmed cells of monocytic origin). The monocytes isolated by immunomagnetic separation were cultured in a de-differentiating medium (complete culture medium supplemented with M-CSF, IL-3 and β-mercaptoethanol) for one week. Later on, the medium was replaced by the addition of GM-CSF, being cultured for three days, followed by addition of LPS and IL-1β in order to induce suppressive activity. We have found that culturing CD14+ cells on a two-week schedule with prior creation of dedifferentiation conditions resulted in a slightly decreased percentage of viable cells in culture. However, there was a trend towards an increased ratio of MDSCs in culture (from an average of 34 to 40%) and an increase in their suppressive activity (arginase and IDO expression). The percentage of Arg+ cells increased by average of 10%, and IDO+ cells, by 16%. Moreover, the percentage of mature M-MDSCs was significantly (several-fold) higher when compared with differentiation protocol using CD11b+ cells. Hence, this method of MDSCs production enables us to increase the number of cells belonging to the conditionally “mature” monocyte subpopulation of MDSCs, as well as the percentage of functional suppressor cells in the population. The described scheme may be used to improve the quality of studies aimed at modulating MDSC functions in order to develop new therapeutic approaches.

Reconditioned monocytes are immunomodulatory and regulate inflammatory environment in sepsis

Sepsis is caused by dysregulated immune response to severe infection and hyper inflammation plays a central role in worsening the disease. The immunomodulatory properties of mesenchymal stem cells (MSCs) have been evaluated as a therapeutic candidate for sepsis. Reconditioned monocytes (RM), generated from healthy human peripheral blood mononuclear cells (PBMCs) exhibit both macrophage and MSCs-like properties. RM were administered at different stages of sepsis in a mouse model. It reduced serum levels of IL6, MCP-1, IL-10, improved hypothermia, increased survival, and recovery from 0 to 66% when combined with antibiotics in the mouse model. The reduced human leucocyte antigen DR molecules expression on RM enables their co-culture with PBMCs of sepsis patients which resulted in reduced ROS production, and up-regulated TGF-β while down-regulating IL6, IL8, and IL-10 in-vitro. RM are potentially immunomodulatory, enhance survival in sepsis mouse model and modulate inflammatory behaviour of sepsis patient's PBMCs.

Progress in Regenerative Medicine: Exploring Autologous Platelet Concentrates and Their Clinical Applications

The goal of regenerative medicine is to achieve tissue regeneration. In the past, commonly used techniques included autologous or allogeneic transplantation and stem cell therapy, which have limitations, such as a lack of donor sites in the case of autologous transplantation and the invasiveness of stem cell harvesting. In recent years, research has, therefore, focused on new and less invasive strategies to achieve tissue regeneration. A step forward in this direction has been made with the development of autologous platelet concentrates (APCs), which are derived from the patient's own blood. They can be classified into three generations: platelet-rich plasma (PRP), platelet-rich fibrin (PRF), and concentrated growth factors (CGFs). These APCs have different structural characteristics, depending on the distinctive preparation method, and contain platelets, leukocytes, and multiple growth factors, including those most involved in regenerative processes. The purpose of this review is to clarify the most used techniques in the field of regenerative medicine in recent years, comparing the different types of APCs and analyzing the preparation protocols, the composition of the growth factors, the level of characterization achieved, and their clinical applications to date.

The Yin and Yang of Mesenchymal Cells in the Corneal Stromal Fibrosis Response to Injury: The Cornea as a Model of Fibrosis in Other Organs

Mesenchymal cells (keratocytes, corneal fibroblasts, and myofibroblasts), as well as mesenchymal progenitor bone marrow-derived fibrocytes, are the major cellular contributors to stromal fibrosis after injury to the cornea. Corneal fibroblasts, in addition to being major progenitors to myofibroblasts, also have anti-fibrotic functions in (1) the production of non-basement membrane collagen type IV that binds activated transforming growth factor (TGF) beta-1 and TGF beta-2 to downregulate TGF beta effects on cells in the injured stroma, (2) the production of chemokines that modulate the entry of bone marrow-derived cells into the stroma, (3) the production of hepatocyte growth factor and keratinocyte growth factor to regulate corneal epithelial healing, (4) the cooperation with the epithelium or corneal endothelium in the regeneration of the epithelial basement membrane and Descemet's membrane, and other functions. Fibrocytes also serve as major progenitors to myofibroblasts in the corneal stroma. Thus, mesenchymal cells and mesenchymal cell progenitors serve Yin and Yang functions to inhibit and promote tissue fibrosis depending on the overall regulatory milieu within the injured stroma.

Pulmonary Fibrosis as a Result of Acute Lung Inflammation: Molecular Mechanisms, Relevant In Vivo Models, Prognostic and Therapeutic Approaches

Pulmonary fibrosis is a chronic progressive lung disease that steadily leads to lung architecture disruption and respiratory failure. The development of pulmonary fibrosis is mostly the result of previous acute lung inflammation, caused by a wide variety of etiological factors, not resolved over time and causing the deposition of fibrotic tissue in the lungs. Despite a long history of study and good coverage of the problem in the scientific literature, the effective therapeutic approaches for pulmonary fibrosis treatment are currently lacking. Thus, the study of the molecular mechanisms underlying the transition from acute lung inflammation to pulmonary fibrosis, and the search for new molecular markers and promising therapeutic targets to prevent pulmonary fibrosis development, remain highly relevant tasks. This review focuses on the etiology, pathogenesis, morphological characteristics and outcomes of acute lung inflammation as a precursor of pulmonary fibrosis; the pathomorphological changes in the lungs during fibrosis development; the known molecular mechanisms and key players of the signaling pathways mediating acute lung inflammation and pulmonary fibrosis, as well as the characteristics of the most common in vivo models of these processes. Moreover, the prognostic markers of acute lung injury severity and pulmonary fibrosis development as well as approved and potential therapeutic approaches suppressing the transition from acute lung inflammation to fibrosis are discussed.

Monocyte Recruitment for Vascular Tissue Regeneration

A strategy to recruit monocytes (MCs) from blood to regenerate vascular tissue from unseeded (cell-free) tissue engineered vascular grafts is presented. When immobilized on the surface of vascular grafts, the fusion protein, H2R5 can capture blood-derived MC under static or flow conditions in a shear stress dependent manner. The bound MC turns into macrophages (Mϕ) expressing both M1 and M2 phenotype specific genes. When H2R5 functionalized acellular-tissue engineered vessels (A-TEVs) are implanted into the mouse aorta, they remain patent and form a continuous endothelium expressing both endothelial cell (EC) and MC specific proteins. Underneath the EC layer, multiple cells layers are formed coexpressing both smooth muscle cell (SMC) and MC specific markers. Lineage tracing analysis using a novel CX3CR1-confetti mouse model demonstrates that fluorescently labeled MC populates the graft lumen by two and four weeks postimplantation, providing direct evidence in support of MC/Mϕ recruitment to the graft lumen. Given their abundance in the blood, circulating MCs may be a great source of cells that contribute directly to the endothelialization and vascular wall formation of acellular vascular grafts under the right chemical and biomechanical cues.

Dopamine-induced pruning in monocyte-derived-neuronal-like cells (MDNCs) from patients with schizophrenia

The long lapse between the presumptive origin of schizophrenia (SCZ) during early development and its diagnosis in late adolescence has hindered the study of crucial neurodevelopmental processes directly in living patients. Dopamine, a neurotransmitter consistently associated with the pathophysiology of SCZ, participates in several aspects of brain development including pruning of neuronal extensions. Excessive pruning is considered the cause of the most consistent finding in SCZ, namely decreased brain volume. It is therefore possible that patients with SCZ carry an increased susceptibility to dopamine's pruning effects and that this susceptibility would be more obvious in the early stages of neuronal development when dopamine pruning effects appear to be more prominent. Obtaining developing neurons from living patients is not feasible. Instead, we used Monocyte-Derived-Neuronal-like Cells (MDNCs) as these cells can be generated in only 20 days and deliver reproducible results. In this study, we expanded the number of individuals in whom we tested the reproducibility of MDNCs. We also deepened the characterization of MDNCs by comparing its neurostructure to that of human developing neurons. Moreover, we studied MDNCs from 12 controls and 13 patients with SCZ. Patients' cells differentiate more efficiently, extend longer secondary neurites and grow more primary neurites. In addition, MDNCs from medicated patients expresses less D1R and prune more primary neurites when exposed to dopamine. Haloperidol did not influence our results but the role of other antipsychotics was not examined and thus, needs to be considered as a confounder.

Relation of Monocyte Number to Progression of Aortic Stenosis

Rapid progression of aortic stenosis (AS) is associated with poor prognosis. However, the relation between monocyte number and AS progression is unknown. Here, we detected the relation between monocyte number and AS progression. We retrospectively analyzed 220 patients with AS with at least 2 echocardiograms with the maximal interval ≥180 days from January 2016 to June 2021. AS severity was categorized by aortic jet velocity (V_max) and mean pressure gradient. Rapid progression of AS was defined when V_max increased ≥0.3 m/s/year. Patients were divided into low and high monocyte groups according to the cut-off value of the receiver-operating characteristic curve. AS progression was compared between the 2 groups. Various models of binary logistic regression were used to reveal the association between monocyte number and rapid progression. During a median of 601 days of echocardiographic follow-up (interquartile range 353 to 909), 52.7% of the population was in rapid progression. Patients in the high monocyte group had more rapid progression in both V_max and mean pressure gradient (p = 0.020 and p = 0.030, respectively). The percentage of patients with severe AS was increased by 5.4% in the low monocyte group and 16.9% in the high monocyte group. Different models of binary logistic regression showed that the monocyte number was positively associated with the rapid progression. In conclusion, a higher monocyte number was associated with the rapid progression of AS.

Association of CD90 Expression by CD14+ Dendritic-Shaped Cells in Rheumatoid Arthritis Synovial Tissue With Chronic Inflammation

Objective

CD14⁺ dendritic‐shaped cells show a dendritic morphology under the electron microscopy and engage in a pseudoemperipolesis phenomenon with lymphocytes. CD90 has been used as a marker of a major subset of fibroblast‐like synoviocytes in rheumatoid arthritis (RA). In this study, we investigated the significance of CD90 expression in CD14⁺ dendritic‐shaped cells and its correlation with RA chronic inflammation.

Methods

Double immunofluorescence staining for CD14 and CD90 was performed in the collected tissues, including 12 active RA synovial tissues. The localization of CD14⁺CD90⁺ cells, the percentages of CD14⁺CD90⁺ cells and vascular areas, the degree of synovitis, and clinical data were investigated. Furthermore, CD14⁺CD90⁺ cells analyzed by flow cytometry (CD14^highCD90^{intermediate (int)} cells) were sorted from RA synovial cells, and we examined their potential to differentiate into dendritic cells.

Results

Double immunofluorescence staining showed that CD14⁺CD90⁺ cells were abundant in RA synovial tissues. The percentages of CD14⁺CD90⁺ cells and vascular areas correlated with some of the Krenn synovitis scores, but neither showed a strong correlation with RA disease activity parameters. Flow cytometry analysis indicated that CD14^highCD90^int cells were more abundant in both peripheral blood samples and synovial tissues in patients with active RA. CD14^highCD90^int cells were more likely to differentiate into dendritic cells in vitro.

Conclusion

CD14⁺ dendritic‐shaped cells expressed CD90 in the perivascular areas of RA synovial tissues. These findings suggest that CD14⁺CD90⁺ dendritic‐shaped cells migrate from the peripheral blood to the synovial tissue, the site of inflammation, and may contribute to the chronic inflammation of RA as dendritic progenitor cells.

Continuous and intermittent parathyroid hormone administration promotes osteogenic differentiation and activity of programmable cells of monocytic origin

Bone healing deficiencies are challenging for orthopedic practice. The use of stem cells with scaffolds to treat bone tissue losses currently is popular for promoting regeneration of tissue. Programmable cells of monocytic origin (PCMO) may differentiate into three germ layers and may be a promising alternative treatment due to their stem cell-like properties. Parathyroid hormone (PTH) participates in bone metabolism. Intermittent administration of PTH promotes osteogenic activity of mesenchymal stem cdells (MSC). We investigated the osteogenic effects of continuous and intermittent administration of PTH on PCMO. Mononuclear cells were harvested from the peripheral blood of healthy donors. Isolated cells were cultured for six days in a de-differentiation medium. Indirect immunocytochemistry using anti-CD14, anti-CD45 and anti-CD90 primary antibodies, as well as electron microscopy were used to detect PCMO. PCMO then were cultured in an osteogenic differentiation medium supplemented with continuous or intermittent 50 ng/ml PTH. The PTH-free control group (CG), intermittent PTH treated group (IPG) and continuous PTH treated group (CPG) were cultured and assessed for their differentiation into osteogenic lineage cells by indirect immunocytochemistry using anti-collagen I, anti-osteonectin and anti-osteocalcin primary antibodies. Osteoblast-like cells obtained by continuous or intermittent PTH administration exhibited increased levels of collagen I, osteonectin and osteocalcin immunoreactivity. We found that continuous and intermittent PTH administration to PCMO enhanced their differentiation to osteogenic lineage cells and increased osteoblastic activity.

Endothelial Dysfunction in Systemic Lupus Erythematosus and Systemic Sclerosis: A Common Trigger for Different Microvascular Diseases

This review describes the complex interplay between inflammation, vasculopathy and fibrosis that involve the heart and peripheral small vessels, leading to endothelial stiffness, vascular damage, and early aging in patients with systemic lupus erythematosus and systemic sclerosis, which represents two different models of vascular dysfunction among systemic autoimmune diseases. In fact, despite the fact that diagnostic methods and therapies have been significantly improved in the last years, affected patients show an excess of cardiovascular mortality if compared with the general population. In addition, we provide a complete overview on the new techniques which are used for the evaluation of endothelial dysfunction in a preclinical phase, which could represent a new approach in the assessment of cardiovascular risk in these patients.

Feline hypertrophic cardiomyopathy: reduced microvascular density and involvement of CD34+ interstitial cells

The sequence of pathological events in feline hypertrophic cardiomyopathy (fHCM) is still largely unknown, although we know that fHCM is characterized by interstitial remodeling in a macrophage-driven pro-inflammatory environment and that myocardial ischemia might contribute to its progression. This study aimed to gain further insights into the structural changes associated with interstitial remodeling in fHCM with special focus on the myocardial microvasculature and the phenotype of the interstitial cells. Twenty-eight hearts (16 hearts with fHCM and 12 without cardiac disease) were evaluated in the current study, with immunohistochemistry, RNA-in situ hybridization, and transmission electron microscopy. Morphometrical evaluations revealed a statistically significant lower microvascular density in fHCM. This was associated with structural alterations in capillaries that go along with a widening of the interstitium due to the accumulation of edema fluid, collagen fibers, and mononuclear cells that also proliferated locally. The interstitial cells were mainly of fibroblastic or vascular phenotype, with a substantial contribution of predominantly resident macrophages. A large proportion expressed CD34 mRNA, which suggests a progenitor cell potential. Our results indicate that microvascular alterations are key events in the pathogenesis of fHCM and that myocardial interstitial cell populations with CD34+ phenotype play a role in the pathogenesis of the disease.

Hematopoietic stem cells produce intermediate lineage adipocyte progenitors that simultaneously express both myeloid and mesenchymal lineage markers in adipose tissue

Some adipocytes are produced from bone marrow hematopoietic stem cells. In vitro studies previously indicated that these bone marrow-derived adipocytes (BMDAs) were generated from adipose tissue macrophage (ATM) that lose their hematopoietic markers and acquire mesenchymal markers prior to terminal adipogenic differentiation. Here we interrogated whether this hematopoietic-to-mesenchymal transition drives BMDA production In vitro. We generated transgenic mice in which the lysozyme gene promoter (LysM) indelibly labeled ATM with green fluorescent protein (GFP). We discovered that adipose stroma contained a population of LysM-positive myeloid cells that simultaneously expressed hematopoietic/myeloid markers (CD45 and CD11b), and mesenchymal markers (CD29, PDGFRa and Sca-1) typically found on conventional adipocyte progenitors. These cells were capable of adipogenic differentiation In vitro and In vitro, while other stromal populations deficient in PDGFRa and Sca-1 were non-adipogenic. BMDAs and conventional adipocytes expressed common fat cell markers but exhibited little or no expression of hematopoietic and mesenchymal progenitor cell markers. The data indicate that BMDAs are produced from ATM simultaneously expressing hematopoietic and mesenchymal markers rather than via a stepwise hematopoietic-to-mesenchymal transition. Because BMDA production is stimulated by high fat feeding, their production from hematopoietic progenitors may maintain adipocyte production when conventional adipocyte precursors are diminished.

Higher Levels of Circulating Osteoprogenitor Cells Are Associated With Higher Bone Mineral Density and Lean Mass in Older Adults: A Cross-Sectional Study

Circulating osteo progenitor (COP) cells are a heterogeneous population of cells that circulate within the peripheral blood with characteristics of the bone marrow mesenchymal stem and progenitor pool. Little is known about the behavior of this cell population in humans. The aim of this study was to identify whether a relationship exists between COP cells (as a percentage of the peripheral blood monocytic cells) and musculoskeletal morphometry and to identify if COP have potential clinical utility as a biomarker for osteoporosis. We recruited 57 older adults (median age: 69 years; IQR: 65, 75 years) living independently in the community and performed cross‐sectional analysis to identify associations between the percentage of COP cells and body composition parameters, and through receiver operating characteristic analysis, we evaluated their ability to act as a biomarker of osteoporosis. COP cells were moderately associated with whole‐body bone mineral density (BMD) (r = 0.323, p = 0.014) and bone mineral content (BMC) (r = 0.387, p = 0.003), neck of femur BMD (r = 0.473, p < 0.001), and BMC (r = 0.461, p < 0.001) as well as appendicular lean mass (ALM) (p = 0.038) and male sex (p = 0.044) in univariable analysis. In multivariable analysis controlling for age, gender, height, and weight, COP cells remained strongly associated with neck of femur BMD (p = 0.001) and content (p = 0.003). COP cells were also a good predictor of osteoporosis (dual‐energy X‐ray absorptiometry [DXA] T‐score < −2.5) at the neck of femur (cutoff: 0.4%; sensitivity: 100%; specificity 79%) and total body (cutoff: 0.35%; sensitivity: 80%; specificity: 81%). This study shows strong relationships between bone parameters and COP cell number and male sex. They also have potential as a biomarker of osteoporosis, which may provide a new tool for advanced detection and screening in clinical settings. Future larger evaluation studies should verify the cutoffs for biomarker use, and further explore the relationship between COP cells and muscle. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Mobilized Peripheral Blood Stem Cells are Pluripotent and Can Be Safely Harvested and Stored for Cartilage Repair

PURPOSE

The primary objective of this study was to reproduce and validate the harvest, processing and storage of peripheral blood stem cells for a subsequent cartilage repair trial, evaluating safety, reliability, and potential to produce viable, sterile stem cells.

METHODS

Ten healthy subjects (aged 19-44 years) received 3 consecutive daily doses of filgrastim followed by an apheresis harvest of mononuclear cells on a fourth day. In a clean room, the apheresis product was prepared for cryopreservation and processed into 4 mL aliquots. Sterility and qualification testing were performed pre-processing and post-processing at multiple time points out to 2 years. Eight samples were shipped internationally to validate cell transport potential. One sample from all participants was cultured to test proliferative potential with colony forming unit (CFU) assay. Five samples, from 5 participants were tested for differentiation potential, including chondrogenic, adipogenic, osteogenic, endoderm, and ectoderm assays.

RESULTS

Fresh aliquots contained an average of 532.9 ± 166. × 10⁶ total viable cells/4 mL vial and 2.1 ± 1.0 × 10⁶ CD34+ cells/4 mL vial. After processing for cryopreservation, the average cell count decreased to 331.3 ± 79. × 10⁶ total viable cells /4 mL vial and 1.5 ± 0.7 × 10⁶ CD34+ cells/4 mL vial CD34+ cells. Preprocessing viability averaged 99% and postprocessing 88%. Viability remained constant after cryopreservation at all subsequent time points. All sterility testing was negative. All samples showed proliferative potential, with average CFU count 301.4 ± 63.9. All samples were pluripotent.

CONCLUSIONS

Peripheral blood stem cells are pluripotent and can be safely harvested/stored with filgrastim, apheresis, clean-room processing, and cryopreservation. These cells can be stored for 2 years and shipped without loss of viability.

CLINICAL RELEVANCE

This method represents an accessible stem cell therapy in development to augment cartilage repair.

Analysis of CGF Biomolecules, Structure and Cell Population: Characterization of the Stemness Features of CGF Cells and Osteogenic Potential

Concentrated Growth Factors (CGF) represent new autologous (blood-derived biomaterial), attracting growing interest in the field of regenerative medicine. In this study, the chemical, structural, and biological characterization of CGF was carried out. CGF molecular characterization was performed by GC/MS to quantify small metabolites and by ELISA to measure growth factors and matrix metalloproteinases (MMPs) release; structural CGF characterization was carried out by SEM analysis and immunohistochemistry; CGF has been cultured, and its primary cells were isolated for the identification of their surface markers by flow cytometry, Western blot, and real-time PCR; finally, the osteogenic differentiation of CGF primary cells was evaluated through matrix mineralization by alizarin red staining and through mRNA quantification of osteogenic differentiation markers by real-time PCR. We found that CGF has a complex inner structure capable of influencing the release of growth factors, metabolites, and cells. These cells, which could regulate the production and release of the CGF growth factors, show stem features and are able to differentiate into osteoblasts producing a mineralized matrix. These data, taken together, highlight interesting new perspectives for the use of CGF in regenerative medicine.

Downregulated IRF8 in Monocytes and Macrophages of Patients with Systemic Sclerosis May Aggravate the Fibrotic Phenotype

Monocytes and macrophages may be involved in the pathogenesis of systemic sclerosis (SSc); however, the etiology and regulation of monocyte and macrophage function in SSc remain unknown. IRF8 is a transcriptional regulator that is essential for the differentiation and function of monocytes and macrophages and thus may be involved in the regulation of macrophage phenotypes in SSc fibrosis. In this study, we measured IRF8 levels in circulating monocytes of 26 patients with SSc (diffuse cutaneous SSc, n = 11; limited cutaneous SSc, n = 15) and 14 healthy controls. IRF8 levels were significantly suppressed in monocytes of patients with diffuse cutaneous SSc and correlated negatively with the modified Rodnan total skin thickness score. Next, we assessed expression levels of cell surface markers, cytokine profiles, and components of extracellular matrix in IRF8-silenced monocyte-derived macrophages. IRF8-silenced monocyte-derived macrophages displayed an M2 phenotype and significantly upregulated mRNA and protein levels of profibrotic factors and extracellular matrix components. Finally, we assessed skin fibrosis in myeloid cell-specific IRF8 conditional knockout (Irf8flox/flox; Lyz2Cre/+) mice and found upregulated mRNA levels of extracellular matrix components and increased bleomycin-induced skin fibrosis. In conclusion, altered IRF8 regulation in monocytes and macrophages may be involved in SSc pathogenesis.

Development and validation of a new method to isolate, expand, and differentiate circulating osteogenic precursor (COP) cells

Circulating osteogenic precursor (COP) cells are a population of progenitor cells in the peripheral blood with the capacity to form bone in vitro and in vivo. They have characteristics of the mesenchymal stem and progenitor pool found in the bone marrow; however, more recently, a population of COP cells has been identified with markers of the hematopoietic lineage such as CD45 and CD34. While this population has been associated with several bone pathologies, a lack of cell culture models and inconsistent characterization has limited mechanistic research into their behavior and physiology. In this study, we describe a method for the isolation of CD45+/CD34+/alkaline phosphatase (ALP) + COP cells via fluorescence-activated cell sorting, as well as their expansion and differentiation in culture. Hematopoietic COP cells are a discreet population within the monocyte fraction of the peripheral blood mononuclear cells, which form proliferative, fibroblastoid colonies in culture. Their expression of hematopoietic markers decreases with time in culture, but they express markers of osteogenesis and deposit calcium with differentiation. It is hoped that this will provide a standard for their isolation, for consistency in future research efforts, to allow for the translation of COP cells into clinical settings.

A Novel Type of Stem Cells Double-Positive for SSEA-3 and CD45 in Human Peripheral Blood

Peripheral blood (PB) contains several types of stem/progenitor cells, including hematopoietic stem and endothelial progenitor cells. We identified a population positive for both the pluripotent surface marker SSEA-3 and leukocyte common antigen CD45 that comprises 0.04% ± 0.003% of the mononuclear cells in human PB. The average size of the SSEA-3(+)/CD45(+) cells was 10.1 ± 0.3 µm and ∼22% were positive for CD105, a mesenchymal marker; ∼85% were positive for CD19, a B cell marker; and ∼94% were positive for HLA-DR, a major histocompatibility complex class II molecule relevant to antigen presentation. These SSEA-3(+)/CD45(+) cells expressed the pluripotency markers Nanog, Oct3/4, and Sox2, as well as sphingosine-1-phosphate (S1P) receptor 2, and migrated toward S1P, although their adherence and proliferative activities in vitro were low. They expressed NeuN at 7 d, Pax7 and desmin at 7 d, and alpha-fetoprotein and cytokeratin-19 at 3 d when supplied to mouse damaged tissues of the brain, skeletal muscle and liver, respectively, suggesting the ability to spontaneously differentiate into triploblastic lineages compatible to the tissue microenvironment. Multilineage-differentiating stress enduring (Muse) cells, identified as SSEA-3(+) in tissues such as the bone marrow and organ connective tissues, express pluripotency markers, migrate to sites of damage via the S1P-S1P receptor 2 system, and differentiate spontaneously into tissue-compatible cells after homing to the damaged tissue where they participate in tissue repair. After the onset of acute myocardial infarction and stroke, patients are reported to have an increase in the number of SSEA-3(+) cells in the PB. The SSEA-3(+)/CD45(+) cells in the PB showed similarity to tissue-Muse cells, although with difference in surface marker expression and cellular properties. Thus, these findings suggest that human PB contains a subset of cells that are distinct from known stem/progenitor cells, and that CD45(+)-mononuclear cells in the PB comprise a novel subpopulation of cells that express pluripotency markers.

Monocyte and macrophage derived myofibroblasts: Is it fate? A review of the current evidence

Since the discovery of the myofibroblast over 50 years ago, much has been learned about its role in wound healing and fibrosis. Its origin, however, remains controversial, with a number of progenitor cells being proposed. Macrophage-myofibroblast transition (MMT) is a recent term coined in 2014 that describes the mechanism through which macrophages, derived from circulating monocytes originating in the bone marrow, transformed into myofibroblasts and contributed to kidney fibrosis. Over the past years, several studies have confirmed the existence of MMT in various systems, suggesting that MMT could potentially occur in all fibrotic conditions and constitute a reasonable therapeutic target to prevent progressive fibrotic disease. In this perspective, we examined recent evidence supporting the notion of MMT in both human disease and experimental models across organ systems. Mechanistic insight from these studies and information from in vitro studies is provided. The findings substantiating plausible MMT showcased the co-expression of macrophage and myofibroblast markers, including CD68 or F4/80 (macrophage) and α-SMA (myofibroblast), in fibroblast-like cells. Furthermore, fate-mapping experiments in murine models exhibiting myeloid-derived myofibroblasts in the tissue further provide direct evidence for MMT. Additionally, we provide some evidence from single cell RNA sequencing experiments confirmed by fluorescent in situ hybridisation studies, showing monocyte/macrophage and myofibroblast markers co-expressed in lung tissue from patients with fibrotic lung disease. In conclusion, MMT is likely a significant contributor to myofibroblast formation in wound healing and fibrotic disease across organ systems. Circulating precursors including monocytes and the molecular mechanisms governing MMT could constitute valid targets and provide insight for the development of novel antifibrotic therapies; however, further understanding of these processes is warranted.

Osteoporosis Entwined with Cardiovascular Disease: The Implication of Osteoprotegerin and the Example of Statins

Beyond being epiphenomenon of shared epidemiological factors, the integration of Osteoporosis (OP) with Cardiovascular Disease (CVD) - termed "calcification paradox" - reflects a continuum of aberrant cardiometabolic status. The present review provides background knowledge on "calcification paradox", focusing on the endocrine aspect of vasculature orchestrated by the osteoblastic molecular fingerprint of vascular cells, acquired via imbalance among established modulators of mineralization. Osteoprotegerin (OPG), the well-established osteoprotective cytokine, has recently been shown to exert a vessel-modifying role. Prompted by this notion, the present review interrogates OPG as the potential missing link between OP and CVD. However, so far, the confirmation of this hypothesis is hindered by the equivocal role of OPG in CVD, being both proatherosclerotic and antiatherosclerotic. Further research is needed to illuminate whether OPG could be a biomarker of the "calcification paradox". Moreover, the present review brings into prominence the dual role of statins - cardioprotective and osteoprotective - as a potential illustration of the integration of CVD with OP. Considering that the statins-induced modulation of OPG is central to the statins-driven osteoprotective signalling, statins could be suggested as an illustration of the role of OPG in the bone/vessels crosstalk, if further studies consolidate the contribution of OPG to the cardioprotective role of statins. Another outstanding issue that merits further evaluation is the inconsistency of the osteoprotective role of statins. Further understanding of the varying bone-modifying role of statins, likely attributed to the unique profile of different classes of statins defined by distinct physicochemical characteristics, may yield tangible benefits for treating simultaneously OP and CVD.

Biologics in the Treatment of Achilles Tendon

The treatment of Achilles tendinitis from conservative to minimally invasive to surgery gives patients a wide range of treatment options for this common pathology. The use and role of biologics to augment this treatment is emerging. The use of biologics may enhance the healing potential of the Achilles tendon when conservative treatment fails. There are a handful of biologics being investigated to obtain if improved outcomes can be maximized.

Bone From Blood: Characteristics and Clinical Implications of Circulating Osteogenic Progenitor (COP) Cells

Circulating osteogenic progenitor (COP) cells are a population of cells in the peripheral blood with the capacity for bone formation, as well as broader differentiation into mesoderm-like cells in vitro. Although some of their biological characteristics are documented in vitro, their role in diseases of the musculoskeletal system remains yet to be fully evaluated. In this review, we provide an overview of the role of COP cells in a number of physiological and pathological conditions, as well as identify areas for future research. In addition, we suggest possible areas for clinical utilization in the management of musculoskeletal diseases. © 2020 American Society for Bone and Mineral Research (ASBMR).

Fibrocyte localisation to the ASM bundle in asthma: bidirectional effects on cell phenotype and behaviour

Objectives

Airway hyper‐responsiveness and persistent airflow obstruction contribute to asthma pathogenesis and symptoms, due in part to airway smooth muscle (ASM) hypercontractility and increased ASM mass. Fibrocytes have been shown to localise to the ASM in asthma however it is not known whether fibrocytes localise to the ASM in nonasthmatic eosinophilic bronchitis (NAEB) and chronic obstructive pulmonary disease (COPD). In addition, the potential consequences of fibrocyte localisation to ASM as regards asthma pathophysiology has not been widely studied.

Methods

Fibrocytes and proliferating cells were enumerated in ASM in bronchial tissue using immunohistochemistry. The effects of primary ASM and fibrocytes upon each other in terms of phenotype and behaviour following co‐culture were investigated by assessing cell number, size, apoptotic status, phenotype and contractility in in vitro cell‐based assays.

Results

Increased fibrocyte number in the ASM was observed in asthma versus NAEB, but not NAEB and COPD versus controls, and confirmed in asthma versus controls. ASM proliferation was not detectably different in asthmatics versus healthy controls in vivo. No difference in proliferation, apoptotic status or size of ASM was seen following culture with/without fibrocytes. Following co‐culture with ASM from asthmatics versus nonasthmatics, fibrocyte smooth muscle marker expression and collagen gel contraction were greater. Following co‐culture, fibrocyte CD14 expression was restored with the potential to contribute to asthma pathogenesis via monocyte‐mediated processes dependent on the inflammatory milieu.

Conclusion

Further understanding of mechanisms of fibrocyte recruitment to and/or differentiation within the ASM may identify novel therapeutic targets to modulate ASM dysfunction in asthma.

Quantification and Qualification of Stem Cells From Blood After Mobilization With Filgrastim, and Concentration Using a Platelet-Rich Plasma System

PURPOSE

To determine the cellular composition of a product created with peripheral blood harvested after systemic mobilization with filgrastim and processed with one point-of-care blood concentrating system, i.e., a platelet-rich plasma (PRP) system. The second purpose was to compare mobilized platelet-rich plasma (M-PRP) with a concentrated bone marrow aspirate (cBMA) and a PRP created from the same subjects with the same PRP system.

METHODS

Ten healthy volunteer subjects were recruited for collection and analysis of 3 tissue sources: non-treated peripheral blood, bone marrow aspirate, and filgrastim-mobilized peripheral blood, involving 4 doses of weight-based filgrastim. One point-of-care blood and bone marrow concentrating system was used to create 3 products: PRP, cBMA, and M-PRP. Automated hematologic analysis was performed on all products to quantify total red blood cells, white blood cells (WBCs), monocyte, platelet, and hematopoietic progenitor cell (HPC) concentrations. Flow cytometry was used to determine hematopoietic and mesenchymal progenitor cell populations. Lastly, concentrates were cultured and fibroblast colony-forming units (CFU-F) and morphology of adherent cells were evaluated.

RESULTS

M-PRP contained a greater concentration of WBC (mean difference = 53.2 k/μL; P < .0001), monocytes (mean difference = 8.3 k/μL; P = .002), and a trend toward a greater concentration of HPC (mean difference = 200.5 /μL; P = .060) when compared with PRP. M-PRP contained a greater concentration of monocytes (mean difference = 5.5 k/μL; P = .017) and a trend toward a greater concentration of platelets (mean difference = 348 k/μL; P = .051) and HPC (mean difference = 193.4 /μL; P = .068) when compared with cBMA. M-PRP had a similar concentration of platelets to PRP (mean difference = 110 k/μL; P = .051) and PRP had a greater concentration than cBMA (mean difference = 458 k/μL; P = .003). cBMA remained the only product capable of producing CFU-Fs (446 ± 247 /mL) as neither the M-PRP nor PRP produced CFU-Fs. M-PRP produced colonies consistent with WBC.

CONCLUSIONS

M-PRP, produced with filgrastim mobilized blood and a proprietary PRP system, contained more total WBCs, monocytes, platelets, and HPCs than cBMA and more WBCs, monocytes, and HPCs than PRP.

CLINICAL RELEVANCE

Filgrastim mobilized PRP may be an alternative to cBMA for use as a point-of-care product for orthopaedic treatments.

Osteogenic differentiation potential of porcine bone marrow mesenchymal stem cell subpopulations selected in different basal media

Multipotent porcine mesenchymal stem cells (pMSC) are invaluable for research and therapeutic use in regenerative medicine. Media used for derivation and expansion of pMSC may play an important role for the selection of MSC subpopulation at an early stage and thereby, the specific basal medium may also affect differentiation potential of these cells. The present study was undertaken to evaluate the effects of αMEM, aDMEM, M199, αMEM/M199, aDMEM/M199 and αMEM/aDMEM media on (1) porcine bone marrow MSC derivation; (2) expression of number of osteogenic markers (ALP, COL1A1, SPP1 and BGLAP) at 5th and 10th passage in pMSC before differentiation; and (3) differentiation of pMSC (at 5th passage) to osteogenic lineage. Morphological changes and matrix formation in osteogenic cells were evaluated by microscopic examination. Calcium deposits in osteocytes were confirmed by Alizarin Red S staining. Based on expression of different markers, it was evident that selection of bone marrow pMSC subpopulations was independent of basal media used. However, the differentiation of those pMSCs, specifically to osteogenic lineage, was dependent on the medium used for expansion of pMSC at the pre-differentiation stage. We demonstrated here that the pMSC grown in combined αMEM/aDMEM (1:1) medium expressed number of osteogenic markers and these pMSC underwent osteogenic differentiation most efficiently, in comparison to porcine mesenchymal stem cells grown in other media. In conclusion, osteogenic differentiation potential of pMSC maintained in αMEM/aDMEM medium was observed significantly higher compared to cells cultivated in other media and therefore, the combined medium αMEM/aDMEM (1:1) may preferentially be used for expansion of pMSC, if needed for osteogenic differentiation.

How Fat Grafting Works

Fat grafting has been shown to improve diseased soft issue. Although the mechanism behind fat grafting’s regenerative properties is currently debated, published studies agree that there is an associated vasculogenic effect. A systematic literature review was conducted to elucidate the biochemical pathways responsible for establishing neo-vasculature to grafted fat.

Monocyte-derived multipotent cell delivered programmed therapeutics to reverse idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a highly heterogeneous and fatal disease. However, IPF treatment has been limited by the low drug delivery efficiency to lungs and dysfunctional "injured" type II alveolar epithelial cell (AEC II). Here, we present surface-engineered nanoparticles (PER NPs) loading astaxanthin (AST) and trametinib (TRA) adhered to monocyte-derived multipotent cell (MOMC) forming programmed therapeutics (MOMC/PER). Specifically, the cell surface is designed to backpack plenty of PER NPs that reach directly to the lungs due to the homing characteristic of the MOMC and released PER NPs retarget injured AEC II after responding to the matrix metalloproteinase-2 (MMP-2) in IPF tissues. Then, released AST can enhance synergetic effect of TRA for inhibiting myofibroblast activation, and MOMC can also repair injured AEC II to promote damaged lung regeneration. Our findings provide proof of concept for developing a strategy for cell-mediated lung-targeted delivery platform carrying dual combined therapies to reverse IPF.

Nanoengineered immunosuppressive therapeutics modulating M1/M2 macrophages into the balanced status for enhanced idiopathic pulmonary fibrosis therapy

Effective treatment in clinic for idiopathic pulmonary fibrosis (IPF) remains a challenge due to low drug accumulation in lungs and imbalanced polarization of pro/anti-inflammatory macrophages (M1/M2 macrophages). Herein, a novel endogenous cell-targeting nanoplatform (PNCE) is developed for enhanced IPF treatment efficacy through modulating M1/M2 macrophages into the balanced status to suppress fibroblast over-activation. Notably, PNCE loaded with nintedanib (NIN) and colchicine (COL) can firstly target endogenous monocyte-derived multipotent cells (MOMCs) and then be effectively delivered into IPF lungs due to the homing ability of MOMCs, and detached sensitively from MOMCs by matrix metalloproteinases-2 (MMP-2) over-expressed in IPF lungs. After PNCE selectively accumulated within fibrosis foci, COL can mildly modulate the polarization of M1 macrophages into M2 macrophages to balance innate immune responses, which can enhance the suppressing effect of NIN on fibroblast activation, further improving the IPF therapy. Altogether, PNCE has two collaborative steps including the inhibition of innate immune responses accompanied by the decrease of fibroblast populations in IPF lungs, achieving a stronger and excellent anti-fibrotic efficacy both in vitro and in vivo. This endogenous cell-based engineered liposomal nanoplatform not only allows therapeutic drugs to take effect selectively in vivo, but also provides an alternative strategy for an enhanced curative effect by modulating innate immune responses in IPF therapy.

Endothelial cells and endothelial progenitor cells in the pathogenesis of systemic sclerosis

Systemic sclerosis (SSc) is a connective tissue disease characterized by excessive fibrosis, microvasculopathy, and autoimmunity. Endothelial cell (EC) injury and subsequent endothelial cell dysfunction is believed to be an initial event that eventually leads to a vicious pathogenic cycle. This process is further enhanced by defective angiogenesis and vasculogenesis, as the vascular repair machinery does not work properly. Endothelial progenitor cells (EPCs) are functionally and quantitatively insufficient to recover the endothelium in SSc patients. The dysfunctional ECs and EPCs not only trigger the formation of typical vascular lesions, such as progressive intimal fibrosis in small arteries and the loss of capillaries, but also promote a series of inflammatory and profibrotic processes, such as endothelial-mesenchymal transition and recruitment and accumulation of monocytic EPCs with profibrotic properties. These processes together contribute to the accumulation of extracellular matrix in the affected tissue. This review features current insights into the roles of ECs and EPCs in the pathogenesis of SSc.

Inflammation in Fibrodysplasia Ossificans Progressiva and Other Forms of Heterotopic Ossification

PURPOSE OF REVIEW

Heterotopic ossification (HO) is associated with inflammation. The goal of this review is to examine recent findings on the roles of inflammation and the immune system in HO. We examine how inflammation changes in fibrodysplasia ossificans progressiva, in traumatic HO, and in other clinical conditions of HO. We also discuss how inflammation may be a target for treating HO.

RECENT FINDINGS

Both genetic and acquired forms of HO show similarities in their inflammatory cell types and signaling pathways. These include macrophages, mast cells, and adaptive immune cells, along with hypoxia signaling pathways, mesenchymal stem cell differentiation signaling pathways, vascular signaling pathways, and inflammatory cytokines. Because there are common inflammatory mediators across various types of HO, these mediators may serve as common targets for blocking HO. Future research may focus on identifying new inflammatory targets and testing combinatorial therapies based on these results.

Biologics in the Treatment of Achilles Tendon Pathologies

Regenerative medicine is gaining more and more space for the treatment of Achilles pathologic conditions. Biologics could play a role in the management of midportion Achilles tendinopathy as a step between conservative and surgical treatment or as an augmentation. Higher-level studies are needed before determining a level of treatment recommendation for biologic strategies for insertional Achilles tendinopathy. Combining imaging with patient's functional requests could be the way to reach a protocol for the use of biologics for the treatment of midportion Achilles tendinopathy and, for this perspective, the authors describe the Foot and Ankle Reconstruction Group algorithm of treatment.

CD14 is a unique membrane marker of porcine spermatogonial stem cells, regulating their differentiation

Molecular markers of spermatogonia are necessary for studies on spermatogonial stem cells (SSCs) and improving our understanding of molecular and cellular biology of spermatogenesis. Although studies of germ cell surface marker have been extensively conducted in the testes of rodents, these markers have not been well studied in domestic animals. We aimed to determine the expression pattern of cluster of differentiation 14 (CD14) in developing porcine testes and cultured porcine SSCs (pSSCs), as well as its role in pSSC colony formation. Interestingly, expression of CD14 was observed in porcine testes with PGP9.5-positive undifferentiated spermatogonia at all developmental stages. In addition, in vitro cultured pSSCs expressed CD14 and showed successful colony formation, as determined by fluorescence-activated cell sorting and flow cytometry. PKH26 dye-stained CD14-positive cells transplants were performed into the testes of recipient mice, which were depleted of both testicular germ and somatic cells from immunodeficiency mice and were shown to colonise the recipient testes. Moreover, a colony-forming assay showed that the development of pSSC colonies was disrupted by a high concentration of lipopolysaccharide. These studies indicated that CD14 is surface marker of early spermatogonia in developing porcine testes and in pSSCs, suggesting a role for CD14 in porcine spermatogenesis.

The Epithelial-Myeloid-Transition (EMyeT) of cancer cells as a wrongly perceived primary inflammatory process eventually progressing to a bone remodeling malignancy: the alternative pathway for Epithelial- Mesenchymal-Transition hypothesis (EMT)?

Cancer cells express multiple markers expressed by mesenchymal as well as myeloid cells in common and in addition specific markers of the myeloid lineages, especially those of dendritic cells, macrophages and preosteoclasts. It has also been possible to identify monocyte-macrophage gene clusters in cancer cell specimens as well as in cancer cell lines.

Accordingly, like myeloid cells cancer cells often express pro-inflammatory cytokines, and consequently the carcinoma may be perceived by the organism as a primary inflammatory process comparable to the immune inflammatory reactions in the eye or in the case of arthritis. This would explain why a carcinoma may induce a certain alarm state in the organism by increasing a fatal sympathetic tone in the patient, supplying the carcinomas with nutrients at the cost of other requirements, inducing tolerance against the cancer cells mistaken as myeloid cells, provoking fibrosis and neoangiogenesis, and increasing inflammatory cells at the carcinoma site.

This seemingly inflammatory process of Epithelial-Myeloid-Transition (EMyeT) is superimposed by the progression of part of the myeloid cancer cells to stages comparable to preosteoclasts and osteoclasts, and their development to metastasizing carcinomas often at the site of bone.

This concept of carcinogenesis and malignant progression described here challenges the widely accepted EMT-hypotheses and could deliver the rationale for the various peculiar aspects of cancer and the variety of therapeutic antitumoral measures.

Fos-related antigen-1 transgenic mouse as a model for systemic sclerosis: A potential role of M2 polarization

Objectives:

To investigate the systemic sclerosis–related phenotype in fos-related antigen-1 transgenic mice and its underlying mechanisms.

Methods:

Lung and skin sections of constitutive fos-related antigen-1 transgenic mice and wild-type mice were examined by tissue staining and immunohistochemistry. The tricuspid regurgitation pressure gradient was measured by transthoracic echocardiography with a Doppler technique. To assess the impact of fos-related antigen-1 expression on macrophage function, bone marrow–derived mononuclear cells were derived from mice that expressed fos-related antigen-1 under the control of doxycycline and wild-type littermates. These bone marrow–derived mononuclear cells were induced to differentiate into macrophages with or without doxycycline, and analyzed for gene and protein expression. Finally, lung explants obtained from systemic sclerosis patients and control donors were subjected to immunohistochemistry.

Results:

The lungs of fos-related antigen-1 transgenic mice showed excessive fibrosis of the interstitium and thickening of vessel walls, with narrowing lumen, in an age-dependent manner. The tricuspid regurgitation pressure gradient was significantly elevated in fos-related antigen-1 transgenic versus control mice. Increased dermal thickness and the loss of subdermal adipose tissue were also observed in the fos-related antigen-1 transgenic mice. These changes were preceded by a perivascular infiltration of mononuclear cells, predominantly consisting of alternatively activated or M2 macrophages. Overexpressing fos-related antigen-1 in bone marrow–derived mononuclear cell cultures increased the expression of M2-related genes, such as Il10, Alox15, and Arg1. Finally, fos-related antigen-1-expressing M2 macrophages were increased in the lung tissues of systemic sclerosis patients.

Conclusions:

The fos-related antigen-1 transgenic mouse serves as a genetic model of systemic sclerosis that recapitulates the major vascular and fibrotic manifestations of the lungs and skin in systemic sclerosis patients. M2 polarization mediated by the up-regulation of fos-related antigen-1 may play a critical role in the development of systemic sclerosis.

Differentiation Capacity of Monocyte-Derived Multipotential Cells on Nanocomposite Poly(e-caprolactone)-Based Thin Films

Background

Μonocyte-derived multipotential cells (MOMCs) include progenitors capable of differentiation into multiple cell lineages and thus represent an ideal autologous transplantable cell source for regenerative medicine. In this study, we cultured MOMCs, generated from mononuclear cells of peripheral blood, on the surface of nanocomposite thin films.

Methods

For this purpose, nanocomposite Poly(e-caprolactone) (PCL)-based thin films containing either 2.5 wt% silica nanotubes (SiO2ntbs) or strontium hydroxyapatite nanorods (SrHAnrds), were prepared using the spin-coating method. The induced differentiation capacity of MOMCs, towards bone and endothelium, was estimated using flow cytometry, real-time polymerase chain reaction, scanning electron microscopy and fluorescence microscopy after cells' genetic modification using the Sleeping Beauty Transposon System aiming their observation onto the scaffolds. Moreover, Wharton's Jelly Mesenchymal Stromal Cells were cultivated as a control cell line, while Human Umbilical Vein Endothelial Cells were used to strengthen and accelerate the differentiation procedure in semi-permeable culture systems. Finally, the cytotoxicity of the studied materials was checked with MTT assay.

Results

The highest differentiation capacity of MOMCs was observed on PCL/SiO2ntbs 2.5 wt% nanocomposite film, as they progressively lost their native markers and gained endothelial lineage, in both protein and transcriptional level. In addition, the presence of SrHAnrds in the PCL matrix triggered processes related to osteoblast bone formation.

Conclusion

To conclude, the differentiation of MOMCs was selectively guided by incorporating SiO2ntbs or SrHAnrds into a polymeric matrix, for the first time.

A Growth Factor-Free Co-Culture System of Osteoblasts and Peripheral Blood Mononuclear Cells for the Evaluation of the Osteogenesis Potential of Melt-Electrowritten Polycaprolactone Scaffolds

Scaffolds made of biodegradable biomaterials are widely used to guide bone regeneration. Commonly, in vitro assessment of scaffolds’ osteogenesis potential has been performed predominantly in monoculture settings. Hence, this study evaluated the potential of an unstimulated, growth factor-free co-culture system comprised of osteoblasts (OB) and peripheral blood mononuclear cells (PBMC) over monoculture of OB as an in vitro platform for screening of bone regeneration potential of scaffolds. Particularly, this study focuses on the osteogenic differentiation and mineralized matrix formation aspects of cells. The study was performed using scaffolds fabricated by means of a melt electrowriting (MEW) technique made of medical-grade polycaprolactone (PCL), with or without a surface coating of calcium phosphate (CaP). Qualitative results, i.e., cell morphology by fluorescence imaging and matrix mineralization by von Kossa staining, indicated the differences in cell behaviours in response to scaffolds’ biomaterial. However, no obvious differences were noted between OB and OB+PBMC groups. Hence, quantitative investigation, i.e., alkaline phosphatase (ALP), tartrate-resistant acid phosphatase (TRAP) activities, and gene expression were quantitatively evaluated by reverse transcription-polymerase chain reaction (RT-qPCR), were evaluated only of PCL/CaP scaffolds cultured with OB+PBMC, while PCL/CaP scaffolds cultured with OB or PBMC acted as a control. Although this study showed no differences in terms of osteogenic differentiation and ECM mineralization, preliminary qualitative results indicate an obvious difference in the cell/non-mineralized ECM density between scaffolds cultured with OB or OB+PBMC that could be worth further investigation. Collectively, the unstimulated, growth factor-free co-culture (OB+PBMC) system presented in this study could be beneficial for the pre-screening of scaffolds’ in vitro bone regeneration potential prior to validation in vivo.

Circulating osteogenic precursor cells: Building bone from blood

Circulating osteogenic precursor (COP) cells constitute a recently discovered population of circulating progenitor cells with the capacity to form not only bone but other mesenchymal tissues. There is a small, but growing body of literature exploring these cells, but with a great deal of disagreement and contradiction within it. This review explores the origins and biological characterization of these cells, including the identification strategies used to isolate these cells from the peripheral blood. It also examines the available knowledge on the in vitro and in vivo behaviour of these cells, in the areas of plastic adherence, differentiation capacity, proliferation, and cellular homing. We also review the implications for future use of COP cells in clinical practice, particularly in the area of regenerative medicine and the treatment and assessment of musculoskeletal disease.

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Circulating Osteogenic Precursors are circulating cells with characteristics of bone marrow mesenchymal stem cells.

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They are able to differentiate into bone, fat, cartilage and muscle, but many other characteristics remain unknown.

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They are heterogenous, with at least two specific populations present, with displaying different markers and behaviors.

Transfection of Peripheral Blood Monocytes with SOX2 Enhances Multipotency, Proliferation, and Redifferentiation into Neohepatocytes and Insulin-Producing Cells

Following a several-day incubation in medium containing IL-3 and M-CSF to generate a more plastic intermediate "reprogrammed multipotent cells of monocytic origin (RMCMO)," peripheral blood mononuclear cells (PBMCs) can be efficiently converted to hepatocyte-like cells (neohepatocytes) and insulin-producing cells. However, continuous efforts are devoted to enhancing the proliferative capacity of these multipotent cells while maintaining or further increasing their redifferentiation potential. In the present work, PBMCs were transfected with one pluripotency gene (SOX2) and the resulting RMCMO compared to standard RMCMO with respect to cell viability, proliferative activity, and redifferentiation potential. Ectopic SOX2 expression increased the number of viable RMCMO, activated cell cycle genes, and enhanced proliferation as shown by quantitative RT-PCR and Ki67 immunofluorescent staining, respectively. Redifferentiation of RMCMO derived from SOX2-transfected PBMCs to neohepatocytes was more complete in comparison to control cells as revealed by higher urea and glucose secretion, increased activity of cytochrome P450 isoforms, and a phase II enzyme, while the same was true for insulin-producing cells as assessed by the expression of INS, PDX1, and GLUT2 and glucose-stimulated insulin secretion. Our results indicate that SOX2 transfection increases both multipotency and proliferation of RMCMO, eventually allowing production of neohepatocytes and insulin-producing cells of higher quality and quantity for transplantation purposes.

Transdifferentiation of Human Circulating Monocytes Into Neuronal-Like Cells in 20 Days and Without Reprograming

Despite progress, our understanding of psychiatric and neurological illnesses remains poor, at least in part due to the inability to access neurons directly from patients. Currently, there are in vitro models available but significant work remains, including the search for a less invasive, inexpensive and rapid method to obtain neuronal-like cells with the capacity to deliver reproducible results. Here, we present a new protocol to transdifferentiate human circulating monocytes into neuronal-like cells in 20 days and without the need for viral insertion or reprograming. We have thoroughly characterized these monocyte-derived-neuronal-like cells (MDNCs) through various approaches including immunofluorescence (IF), flow cytometry, qRT-PCR, single cell mRNA sequencing, electrophysiology and pharmacological techniques. These MDNCs resembled human neurons early in development, expressed a variety of neuroprogenitor and neuronal genes as well as several neuroprogenitor and neuronal proteins and also presented electrical activity. In addition, when these neuronal-like cells were exposed to either dopamine or colchicine, they responded similarly to neurons by retracting their neuronal arborizations. More importantly, MDNCs exhibited reproducible differentiation rates, arborizations and expression of dopamine 1 receptors (DR1) on separate sequential samples from the same individual. Differentiation efficiency measured by cell morphology was on average 11.9 ± 1.4% (mean, SEM, n = 38,819 cells from 15 donors). To provide context and help researchers decide which in vitro model of neuronal development is best suited to address their scientific question,we compared our results with those of other in vitro models currently available and exposed advantages and disadvantages of each paradigm.

Vascular ossification: Pathology, mechanisms, and clinical implications

In recent years, the mechanisms and clinical significance of vascular calcification have been increasingly investigated. For over a century, however, pathologists have recognized that vascular calcification is a form of heterotopic ossification. In this review, we aim to describe the pathology and molecular processes of vascular ossification, to characterize its clinical significance and treatment options, and to elucidate areas that require further investigation. The molecular mechanisms of vascular ossification involve the activation of regulators including bone morphogenic proteins and chondrogenic transcription factors and the loss of mineralization inhibitors like fetuin-A and pyrophosphate. Although few studies have examined the gross pathology of vascular ossification, the presence of these molecular regulators and evidence of microfractures and cartilage have been demonstrated on heart valves and atherosclerotic plaques. These changes are often triggered by common inflammatory and metabolic disorders like diabetes, hyperlipidemia, and chronic kidney disease. The increasing prevalence of these diseases warrants further research into the clinical significance of vascular ossification and future treatment options.

The ratio of ADSCs to HSC-progenitors in adipose tissue derived SVF may provide the key to predict the outcome of stem-cell therapy

BACKGROUND

Stromal vascular fraction (SVF) represents an attractive source of adult stem cells and progenitors, holding great promise for numerous cell therapy approaches. In 2017, it was reported that 1524 patients received autologous SVF following the enzymatic digestion of liposuction fat. The treatment was safe and effective and patients showed significant clinical improvement. In a collaborative study, we analyzed SVF obtained from 58 patients having degenerative, inflammatory, autoimmune diseases, and advanced stage cancer.

RESULTS

Flow analysis showed that freshly isolated SVF was very heterogeneous and harbored four major subsets specific to adipose tissue; CD34high CD45- CD31- CD146- adipose-derived stromal/stem cells (ADSCs), CD34low CD45+ CD206+CD31- CD146- hematopoietic stem cell-progenitors (HSC-progenitors), CD34high CD45- CD31+CD146+ adipose tissue-endothelial cells and CD45-CD34-CD31-CD146+ pericytes. Culturing and expanding of SVF revealed a homogenous population lacking hematopoietic lineage markers CD45 and CD34, but were positive for CD90, CD73, CD105, and CD44. Flow cytometry sorting of viable individual subpopulations revealed that ADSCs had the capacity to grow in adherent culture. The identity of the expanded cells as mesenchymal stem cells (MSCs) was further confirmed based on their differentiation into adipogenic and osteogenic lineages. To identify the potential factors, which may determine the beneficial outcome of treatment, we followed 44 patients post-SVF treatment. The gender, age, clinical condition, certain SVF-dose and route of injection, did not play a role on the clinical outcome. Interestingly, SVF yield seemed to be affected by patient's characteristic to various extents. Furthermore, the therapy with adipose-derived and expanded-mesenchymal stem cells (ADE-MSCs) on a limited number of patients, did not suggest increased efficacies compared to SVF treatment. Therefore, we tested the hypothesis that a certain combination, rather than individual subset of cells may play a role in determining the treatment efficacy and found that the combination of ADSCs to HSC-progenitor cells can be correlated with overall treatment efficacy.

CONCLUSIONS

We found that a 2:1 ratio of ADSCs to HSC-progenitors seems to be the key for a successful cell therapy. These findings open the way to future rational design of new treatment regimens for individuals by adjusting the cell ratio before the treatment.