Proteomic Analysis of Exosomes Secreted from Human Alpha-1 Antitrypsin Overexpressing Mesenchymal Stromal Cells

Extracellular vesicles (EVs) mediate many therapeutic effects of stem cells during cellular therapies. Bone marrow-derived mesenchymal stromal cells (BM-MSCs) were manufactured to overexpress the human antiprotease alpha-1 antitrypsin (hAAT) and studied to compare the EV production compared to lentivirus treated control MSCs. The goal of this study was to compare protein profiles in the EVs/exosomes of control and hAAT-MSCs using unbiased, high resolution liquid chromatography and mass spectrometry to explore differences. Nanoparticle tracking analysis (NTA) showed that the particle size of the EVs from control MSCs or hAAT-MSCs ranged from 30 to 200 nm. Both MSCs and hAAT-MSCs expressed exosome-associated proteins, including CD63, CD81, and CD9. hAAT-MSCs also expressed high levels of hAAT. We next performed proteomic analysis of EVs from three healthy donor cell lines. Exosomes collected from cell supernatant were classified by GO analysis which showed proteins important to cell adhesion and extracellular matrix organization. However, there were differences between exosomes from control MSCs and hAAT-MSCs in cytokine signaling of the immune system, stem cell differentiation, and carbohydrate metabolism (p < 0.05). These results show that hAAT-MSC exosomes contain a different profile of paracrine effectors with altered immune function, impacts on MSC stemness, differentiation, and prevention of cell apoptosis and survival that could contribute to improved therapeutic functions.

Method Categorization of Stem Cell Therapy for Degenerative Osteoarthritis of the Knee: A Review

Current clinical applications of mesenchymal stem cell therapy for osteoarthritis lack consistency because there are no established criteria for clinical processes. We aimed to systematically organize stem cell treatment methods by reviewing the literature. The treatment methods used in 27 clinical trials were examined and reviewed. The clinical processes were separated into seven categories: cell donor, cell source, cell preparation, delivery methods, lesion preparation, concomitant procedures, and evaluation. Stem cell donors were sub-classified as autologous and allogeneic, and stem cell sources included bone marrow, adipose tissue, peripheral blood, synovium, placenta, and umbilical cord. Mesenchymal stem cells can be prepared by the expansion or isolation process and attached directly to cartilage defects using matrices or injected into joints under arthroscopic observation. The lesion preparation category can be divided into three subcategories: chondroplasty, microfracture, and subchondral drilling. The concomitant procedure category describes adjuvant surgery, such as high tibial osteotomy. Classification codes were assigned for each subcategory to provide a useful and convenient method for organizing documents associated with stem cell treatment. This classification system will help researchers choose more unified treatment methods, which will facilitate the efficient comparison and verification of future clinical outcomes of stem cell therapy for osteoarthritis.

Selfish, promiscuous, and sometimes useful: how mobile genetic elements drive horizontal gene transfer in microbial populations

Horizontal gene transfer (HGT) drives microbial adaptation but is often under the control of mobile genetic elements (MGEs) whose interests are not necessarily aligned with those of their hosts. In general, transfer is costly to the donor cell while potentially beneficial to the recipients. The diversity and plasticity of cell-MGEs interactions, and those among MGEs, results in complex evolutionary processes where the source, or even the existence of selection for maintaining a function in the genome is often unclear. For example, MGE-driven HGT depends on cell envelope structures and defense systems, but many of these are transferred by MGEs themselves. MGEs can spur periods of intense gene transfer by increasing their own rates of horizontal transmission upon communicating, eavesdropping, or sensing the environment and the host physiology. This may result on high-frequency transfer of host genes unrelated with the MGE. Here, we review how MGEs drive HGT and how their transfer mechanisms, selective pressures, and genomic traits affect gene flow, and therefore adaptation, in microbial populations. The encoding of many adaptive niche-defining microbial traits in MGEs means that intragenomic conflicts and alliances between cells and their MGEs are key to microbial functional diversification.

Establishment Genes Present on pLS20 Family of Conjugative Plasmids Are Regulated in Two Different Ways

During conjugation, a conjugative DNA element is transferred from a donor to a recipient cell via a connecting channel. Conjugation has clinical relevance because it is the major route for spreading antibiotic resistance and virulence genes. The conjugation process can be divided into different steps. The initial steps carried out in the donor cell culminate in the transfer of a single DNA strand (ssDNA) of the conjugative element into the recipient cell. However, stable settlement of the conjugative element in the new host requires at least two additional events: conversion of the transferred ssDNA into double-stranded DNA and inhibition of the hosts’ defence mechanisms to prevent degradation of the transferred DNA. The genes involved in this late step are historically referred to as establishment genes. The defence mechanisms of the host must be inactivated rapidly and—importantly—transiently, because prolonged inactivation would make the cell vulnerable to the attack of other foreign DNA, such as those of phages. Therefore, expression of the establishment genes in the recipient cell has to be rapid but transient. Here, we studied regulation of the establishment genes present on the four clades of the pLS20 family of conjugative plasmids harboured by different Bacillus species. Evidence is presented that two fundamentally different mechanisms regulate the establishment genes present on these plasmids. Identification of the regulatory sequences were critical in revealing the establishment regulons. Remarkably, whereas the conjugation genes involved in the early steps of the conjugation process are conserved and are located in a single large operon, the establishment genes are highly variable and organised in multiple operons. We propose that the mosaical distribution of establishment genes in multiple operons is directly related to the variability of defence genes encoded by the host bacterial chromosomes.

Clinical and preclinical tolerance protocols for vascularized composite allograft transplantation

The field of vascularized composite allografts (VCAs) has undergone significant advancement in recent decades, and VCAs are increasingly common and accepted in the clinical setting, bringing hope of functional recovery to patients with debilitating injuries. A major obstacle facing the widespread application of VCAs is the side effect profile associated with the current immunosuppressive regimen, which can cause a wide array of complications such as infection, malignancy, and even death. Significant concerns remain regarding whether the treatment outweighs the risk. The potential solution to this dilemma would be achieving VCA tolerance, which would allow recipients to receive allografts without significant immunosuppression and its sequelae. Promising tolerance protocols are being studied in kidney transplantation; four major trials have attempted to withdraw immunosuppressive treatment with various successes. The common theme in all four trials is the use of radiation treatment and donor cell transplantation. The knowledge gained from these trials can provide valuable insight into the development of a VCA tolerance protocol. Despite similarities, VCAs present additional barriers compared to kidney allografts regarding tolerance induction. VCA donors are likely to be deceased, which limits the time for significant pre-conditioning. VCA donors are also more likely to be human leukocyte antigen–mismatched, which means that tolerance must be induced across major immunological barriers. This review also explores adjunct therapies studied in large animal models that could be the missing element in establishing a safe and stable tolerance induction method.

Donor Bone Marrow Derived Macrophage Engraftment into the Central Nervous System of Allogeneic Transplant Patients

Introduction: Hematopoietic stem cell transplantation (HSCT) has had a major impact on the treatment of hematologic malignancies. Recent studies have shown the role HSCT can have in gene therapy by providing long-lived genetically modified cells to treat a variety of human diseases. It is well known that HSC and bone marrow-derived cells can differentiate into long-lived tissue macrophages and populate a wide spectrum of tissues including the brain. These cells are termed bone marrow derived macrophages and are akin to microglial cells in both morphology and function. There is an expanding literature of preclinical animal studies focused on the potential benefits of bone marrow derived-macrophage engraftment into the central nervous system (CNS). In this study we report the detection and characterization of donor bone marrow-derived macrophages in the cerebral cortex of allogeneic transplant patients. Methods: To determine the frequency of donor cell engraftment in post-transplant patients, we selected a cohort of 20 patients who had undergone a sex-mismatched transplant. Formalin fixed paraffin embedded cerebral cortex samples were obtained from the Fred Hutch tissue repository. Samples from male and female autologous transplants were used as controls. Tissue sections were stained by XY fluorescent in situ hybridization (FISH) to identify male and female cells. The XY FISH-stained slides were imaged at 40X magnification on a TissueFAX system. Scanned images were analyzed in blinded fashion using TissueQuest software. Male donor cells were defined by the presence of the Y chromosome within DAPI stained nuclei. Parameters were established using a small area and then applied to a larger area covering 10,000-15,000 cells. Identified donors were confirmed by manual inspection. Adjacent sections were used in Iba1 immunohistochemistry (IHC) studies to quantify the microglia/macrophage population. Select cases were used in double fluorescent Iba1 IHC (tyramide signal amplification)/XY-FISH studies to identify the donor cell type. Results: Intraparenchymal donor bone marrow derived cells were identified in all cerebral cortex sex mismatched samples. To determine the identity of donor cells, select cases were stained with fluorescent tyramide based Iba1 IHC, imaged, stained with XY FISH and re-imaged. The majority of donor cells (&gt;80%) showed strong expression of Iba1, confirming them to be bone marrow-derived macrophages. In parallel Iba1 IHC studies we showed that microglial cells constitute ~12% of the scanned cell population. Thus, when computed as a percentage of the macrophage/microglial population, donor cells from myeloablative transplants range from 4.2-25%. The bone marrow derived cells are stable over time since length of the post-transplant period did not have a major impact on the number of donor cells. Prior animal studies have demonstrated the importance of conditioning (total body irradiation (TBI) or Busulfan) in providing access to the CNS and stimulating engraftment. Consistently, we found that the strength of the conditioning regimen had a significant impact on donor cell engraftment into the CNS. Donor cells in myeloablative cases (&gt;1,000cGy) averaged 8.0% (4.2-14.9%) of microglial cells, while those in non-myeloablative cases (&lt;300cGy) averaged 1.3% (1.2-1.3%). In agreement with preclinical studies, we also noted that myeloablative cases from Busulfan or Treosulfan based conditioning had similar levels of donor-derived cells as cases with TBI myeloablative conditioning, averaging 6.6% (4.4-8.3%) of microglial cells. Although only a limited number of samples were available for analysis, the highest level of donor engraftment was observed in patients who had received 2 separate transplants; on average they comprised 16.3% (12.2-25.1%) of microglial cells. Conclusion: This, the largest study of bone marrow-derived macrophages in post-transplant patients, shows that donor derived cells from myeloablative transplants account for 4.1-25.1% of microglial cells. Donor engraftment is highest following myeloablative conditioning or in patients receiving multiple transplants, and lowest in non-myeloablative cases. Our studies document the magnitude of donor-derived macrophages in the CNS following a bone marrow transplant and serve as a basis for future gene therapy studies targeting neurodegenerative disorders. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Single-cell RNA-seq of out-of-thaw mesenchymal stromal cells shows tissue-of-origin differences and inter-donor cell-cycle variations

Background Human Mesenchymal stromal cells (hMSCs) from various tissue sources are widely investigated in clinical trials. These MSCs are often administered to patients immediately after thawing the cryopreserved product (out-of-thaw), yet little is known about the single-cell transcriptomic landscape and tissue-specific differences of out-of-thaw human MSCs. Methods 13 hMSC samples derived from 10 “healthy” donors were used to assess donor variability and tissue-of-origin differences in single-cell gene expression profiles. hMSCs derived and expanded from the bone marrow (BM) or cord tissue (CT) underwent controlled-rate freezing for 24 h. Cells were then transferred to the vapor phase of liquid nitrogen for cryopreservation. hMSCs cryopreserved for at least one week, were characterized immediately after thawing using a droplet-based single-cell RNA sequencing method. Data analysis was performed with SC3 and SEURAT pipelines followed by gene ontology analysis. Results scRNA-seq analysis of the hMSCs revealed two major clusters of donor profiles, which differ in immune-signaling, cell surface properties, abundance of cell-cycle related transcripts, and metabolic pathways of interest. Within-sample transcriptomic heterogeneity is low. We identified numerous differentially expressed genes (DEGs) that are associated with various cellular functions, such as cytokine signaling, cell proliferation, cell adhesion, cholesterol/steroid biosynthesis, and regulation of apoptosis. Gene-set enrichment analyses indicated different functional pathways in BM vs. CT hMSCs. In addition, MSC-batches showed significant variations in cell cycle status, suggesting different proliferative vs. immunomodulatory potential. Several potential transcript-markers for tissue source differences were identified for further investigation in future studies. In functional assays, both BM and CT MSCs suppressed macrophage TNFα secretion upon interferon stimulation. However, differences between donors, tissue-of-origin, and cell cycle are evident in both TNF suppression and cytokine secretion. Conclusions This study shows that donor differences in hMSC transcriptome are minor relative to the intrinsic differences in tissue-of-origin. hMSCs with different transcriptomic profiles showed potential differences in functional characteristics. These findings contribute to our understanding of tissue origin-based differences in out-of-thaw therapeutic hMSC products and assist in the identification of cells with immune-regulatory or survival potential from a heterogeneous MSC population. Our results form the basis of future studies in correlating single-cell transcriptomic markers with immunomodulatory functions.

FATTY ACID RECEPTOR GPR84 AND Th1/Th2 BALANCE IN THE EXPERIMENTAL SYSTEM IN VIVO

While conducting numerous studies, including researchers in our laboratory, it was found that Th1/Th2 balance plays an essential role in the regulation of reactions that determine the outcomes of immunopathological processes in both chronic and acute GVHD models. However, the question about activity of which element in the regulatory process during GVHD induction (for example, a receptor or an enzyme) affects the ratio of this balance depends remains open. It has been suggested that the degree of activation of the GPR84 receptor during GVHD induction can significantly affect the host Th1/Th2 balance. And, by assessing this parameter, the direction of development and the intensity of the pathological process can be determined. The aim of this work was to investigate the effect of ligands such as medium-chain fatty acid receptor GPR84 on the Th1/Th2 balance in an experimental model in an in vivo system.Female DBA/2 and hybrids (C57Bl/6 × DBA/2) F1 mouse strains were used in the experiments.The studied ligands of GPR84 were capric and lauric acids, as well as a synthetic ligand 6-OAU. Chronic GVHD in the semi-allogenic system was induced by injecting splenocytes from DBA/2 mice to B6D2F1 hybrid mice: 60-70 × 106 -cells iv twice with an interval of 6 days. The first administration of the GPR84 ligands was performed one hour after the donor cell transfer and then once a day for two weeks.The effect of the study drugs on the course of chronic GVHD was assessed three months after the onset of the experiment.It was shown that the administration of GPR84 ligands to to animals during the induction of chronic GVHD affects the activity of the receptor and the host Th1/Th2 ratio. In the group with the injection of 6-OAU, the number of animals which the immunopathological process developed according to the Th1-dependent variant increased by more than 1.5-fold, compared with the control group. This fact is consistent with the literature data obtained in the in vitro system. Apparently, the effect of a mixture of capric and lauric acids is mediated by some other mechanism, differed from the GPR84 activation. Therefore, further research is required to realize the promising possibility of adjusting immune responses by including certain fatty acids in the diet.

Donor clonal hematopoiesis and recipient outcomes after transplantation

Background Clonal hematopoiesis (CH) can be transmitted from donor to recipient during allogeneic hematopoietic cell transplantation. Exclusion of candidate donors with CH is controversial since its impact on recipient outcomes and graft alloimmune function is uncertain. Methods We performed targeted error-corrected sequencing on samples from 1727 donors aged 40 or older and assessed the effect of donor CH on recipient clinical outcomes. We measured long-term engraftment of 102 donor clones and cytokine levels in 256 recipients at 3 and 12 months after transplant. Results CH was present in 22.5% of donors, with DNMT3A (14.6%) and TET2 (5.2%) mutations being most common; 85% of donor clones showed long-term engraftment in recipients after transplantation, including clones with variant allele fraction (VAF)<0.01. DNMT3A-CH with VAF≥0.01, but not smaller clones, was associated with improved recipient overall (HR 0.79, P=0.042) and progression-free survival (HR 0.72, P=0.003) after adjustment for significant clinical variables. In patients who received calcineurin-based GVHD prophylaxis, donor DNMT3A-CH was associated with reduced relapse (sHR 0.59, P=0.014), increased chronic GVHD (sHR 1.36, P=0.042), and higher IL-12p70 levels in recipients. No recipient of sole DNMT3A or TET2-CH developed donor cell leukemia (DCL). In 7 of 8 cases, DCL evolved from donor CH with rare TP53 or splicing factor mutations or from donors carrying germline DDX41 mutations. Conclusion Donor CH is closely associated with clinical outcomes in transplant recipients, with differential impact on graft alloimmune function and potential for leukemic transformation related to mutated gene and somatic clonal abundance. Donor DNMT3A-CH is associated with improved recipient survival due to reduced relapse risk, and with an augmented network of inflammatory cytokines in recipients. Risk of DCL in allogeneic transplantation is driven by pre-existing somatic MDS-associated mutations or germline predisposition in donors.