Interactions of human mesenchymal stromal cells with peripheral blood mononuclear cells in a Mitogenic proliferation assay

BACKGROUND

Immunomodulation by mesenchymal stromal cells (MSCs) is a potentially important therapeutic modality. MSCs suppress peripheral blood mononuclear cell (PBMC) proliferation in vitro, suggesting a mechanism for suppressing inflammatory responses in vivo. This study details the interactions of PBMCs and MSCs.

METHODS

Pooled human PBMCs and MSCs were co-cultured at different MSC:PBMC ratios and harvested from 0 to 120 h, with and without phytohaemagglutin A (PHA) stimulation. Proliferation of adherent MSCs and non-adherent PBMCs was assessed by quantitation of ATP levels. PBMC surface marker expression was analyzed by flow cytometry. Indoleamine 2,3-dioxygenase (IDO) activity was determined by kynurenine assay and IDO mRNA by RT-PCR. Cytokine release was measured by ELISA. Immunofluorescent microscopy detected MSC, PBMC, monocyte (CD14+) and apoptotic events.

RESULTS

PBMC proliferation in response to PHA gave a robust ATP signal by 72 h, which was suppressed by co-culture with densely plated MSCs. Very low level MSC seeding densities relative to PBMC number reproducibly stimulated PBMC proliferation. The CD4+/CD3+ population significantly decreased over time while the CD8+/CD3+ population significantly increased. No change in CD4+/CD8+ ratio is seen with high density MSC co-culture; very low density MSCs augment the changes seen in PHA stimulated PBMCs alone. IDO activity in MSCs co-cultured with PBMCs correlated with PBMC suppression. MSCs increased the secretion of IL-10 and IL-6 from stimulated co-cultures and decreased TNF-α secretion. In stimulated co-culture, low density MSCs decreased in number; fluorescence immunomicroscopy detected association of PBMC with MSC and phosphatidyl serine externalization in both cell populations.

CONCLUSIONS

A bidirectional interaction between MSCs and PBMCs occurs during co-culture. High numbers of MSCs inhibit PHA-stimulated PBMC proliferation and the PBMC response to stimulation; low numbers of MSCs augment these responses. Low density MSCs are susceptible to attrition, apparently by PBMC-induced apoptosis. These results may have direct application when considering therapeutic dosing of patients; low MSC doses may have unintended detrimental consequences.

Mesenchymal stromal cell delivery via an ex vivo bioreactor preclinical test system attenuates clot formation for intravascular application

While mesenchymal stromal cells are an appealing therapeutic option for a range of clinical applications, their potential to induce clotting when used systemically remains a safety concern, particularly in hypercoagulable conditions, such as in patients with severe COVID‐19, trauma, or cancers. Here, we tested a novel preclinical approach aimed at improving the safety of mesenchymal stromal cell (MSC) systemic administration by use of a bioreactor. In this system, MSCs are seeded on the exterior of a hollow‐fiber filter, sequestering them behind a hemocompatible semipermeable membrane with defined pore‐size and permeability to allow for a molecularly defined cross talk between the therapeutic cells and the whole blood environment, including blood cells and signaling molecules. The potential for these bioreactor MSCs to induce clots in coagulable plasma was compared against directly injected “free” MSCs, a model of systemic administration. Our results showed that restricting MSCs exposure to plasma via a bioreactor extends the time necessary for clot formation to occur when compared with “free” MSCs. Measurement of cell surface data indicates the presence of known clot inducing factors, namely tissue factor and phosphatidylserine. Results also showed that recovering cells and flushing the bioreactor prior to use further prolonged clot formation time. Furthermore, application of this technology in two in vivo models did not require additional heparin in fully anticoagulated experimental animals to maintain target activated clotting time levels relative to heparin anticoagulated controls. Taken together the clinical use of bioreactor housed MSCs could offer a novel method to control systemic MSC exposure and prolong clot formation time.

Blood Product Administration During Transport Throughout the US Africa Command Theater of Operation

BACKGROUND

United States Africa Command (US AFRICOM) is one of six US Defense Department's geographic combatant commands and is responsible to the Secretary of Defense for military relations with African nations, the African Union, and African regional security organizations. A full-spectrum combatant command, US AFRICOM is responsible for all US Department of Defense operations, exercises, and security cooperation on the African continent, its island nations, and surrounding waters. We seek to characterize blood product administration within AFRICOM using the in-transit visibility tracking tool known as TRAC2ES (TRANSCOM Regulating and Command & Control Evacuation System).

METHODS

We performed a retrospective review of TRAC2ES medical evacuations from the AFRICOM theater of operations conducted between 1 January 2008 and 31 December 2018.

RESULTS

During this time, there were 963 cases recorded in TRAC2ES originating within AFRICOM, of which 10 (1%) cases received blood products. All patients were males. One was a Department of State employee, one was a military working dog, and the remainder were military personnel. Of the ten humans, seven were the result of trauma, most by way of gunshot wound, and three were due to medical causes. Among human subjects receiving blood products for traumatic injuries, a total of 5 units of type O negative whole blood, 29 units of packed red blood cells (pRBCs), and 9 units of fresh frozen plasma (FFP) were transfused. No subjects underwent massive transfusion of blood products, and only one subject received pRBCs and FFP in 1:1 fashion. All subjects survived until evacuation.

CONCLUSIONS

Within the TRAC2ES database, blood product administration within AFRICOM was infrequent, with some cases highlighting lack of access to adequate blood products. Furthermore, the limitations within this database highlight the need for systems designed to capture medical care performance improvement, as this database is not designed to support such analyses. A mandate for performance improvement within AFRICOM that is similar to that of the US Central Command would be beneficial if major improvements are to occur.

Cold storage of platelets in platelet additive solution maintains mitochondrial integrity by limiting initiation of apoptosis-mediated pathways

BACKGROUND

Cold storage of platelets in plasma maintains hemostatic function and is an attractive alternative to room temperature platelets (RTPs). We have recently shown that functional differences between cold-stored platelets (CSPs) and RTPs after 5-day storage are associated with mitochondrial respiration and that CSPs in platelet (PLT) additive solution (PAS) can maintain hemostatic function for at least 15 days.

STUDY DESIGN AND METHODS

This study tested the hypothesis that cold storage in PAS preserves mitochondrial integrity by reducing PLT apoptosis. CSPs and RTPs in plasma or PAS were stored and assayed for up to 15 days for mitochondrial function and integrity, mitochondrial-associated mRNA transcript expression, apoptotic proteins, and apoptotic flow cytometry metrics.

RESULTS

CSP preserved mitochondria-associated mRNA comparable to baseline levels, improved mitochondrial respiration, and minimized depolarization to Day 15. Additionally, CSPs had minimal induction of caspases, preservation of plasma membrane integrity, and low expression of pro-apoptotic Bax. Storage in PAS appeared to be protective for RTPs in some parameters and enhanced the effects of CSPs.

CONCLUSION

Mitochondrial function and molecular analyses defined CSP priming as distinctly different from the well-documented RTP storage lesion. While current blood bank storage at room temperature is limited to 5 to 7 days, refrigeration and storage in PAS for up to 15 days may represent an opportunity to enhance inventories and access to PLT hemostatic support for bleeding patients.

Similar hemostatic responses to hypovolemia induced by hemorrhage and lower body negative pressure reveal a hyperfibrinolytic subset of non-human primates

BACKGROUND

To study central hypovolemia in humans, lower body negative pressure (LBNP) is a recognized alternative to blood removal (HEM). While LBNP mimics the cardiovascular responses of HEM in baboons, similarities in hemostatic responses to LBNP and HEM remain unknown in this species.

METHODS

Thirteen anesthetized baboons were exposed to progressive hypovolemia by HEM and, four weeks later, by LBNP. Hemostatic activity was evaluated by plasma markers, thromboelastography (TEG), flow cytometry, and platelet aggregometry at baseline (BL), during and after hypovolemia.

RESULTS

BL values were indistinguishable for most parameters although platelet count, maximal clot strength (MA), protein C, thrombin anti-thrombin complex (TAT), thrombin activatable fibrinolysis inhibitor (TAFI) activity significantly differed between HEM and LBNP. Central hypovolemia induced by either method activated coagulation; TEG R-time decreased and MA increased during and after hypovolemia compared to BL. Platelets displayed activation by flow cytometry; platelet count and functional aggregometry were unchanged. TAFI activity and protein, Factors V and VIII, vWF, Proteins C and S all demonstrated hemodilution during HEM and hemoconcentration during LBNP, whereas tissue plasminogen activator (tPA), plasmin/anti-plasmin complex, and plasminogen activator inhibitor-1 did not. Fibrinolysis (TEG LY30) was unchanged by either method; however, at BL, fibrinolysis varied greatly. Post-hoc analysis separated baboons into low-lysis (LY30 <2%) or high-lysis (LY30 >2%) whose fibrinolytic state matched at both HEM and LBNP BL. In high-lysis, BL tPA and LY30 correlated strongly (r = 0.95; P<0.001), but this was absent in low-lysis. In low-lysis, BL TAFI activity and tPA correlated (r = 0.88; P<0.050), but this was absent in high-lysis.

CONCLUSIONS

Central hypovolemia induced by either LBNP or HEM resulted in activation of coagulation; thus, LBNP is an adjunct to study hemorrhage-induced pro-coagulation in baboons. Furthermore, this study revealed a subset of baboons with baseline hyperfibrinolysis, which was strongly coupled to tPA and uncoupled from TAFI activity.

Blood component separation of pathogen-reduced whole blood by the PRP method produces acceptable red cells but platelet yields and function are diminished

BACKGROUND

This study evaluated blood components processed by the platelet rich plasma (PRP) method from fresh whole blood (FWB) treated with a pathogen reduction technology (PRT). The effects of storage temperature on PRT treated platelet concentrates (PCs) were also examined.

STUDY DESIGN AND METHODS

PRT was performed using riboflavin and ultraviolet light on FWB in citrate phosphate dextrose anticoagulant. Following PRT, red blood cells (RBCs), PCs, and plasma for fresh frozen plasma (FFP), were isolated by sequential centrifugation. RBCs were stored at 4°C, FFP at -80°C, and PC at 22°C or at 4°C. Components were assayed throughout their storage times for blood gases, chemistry and CBC, hemostatic function as well as platelet (PLT) and RBC integrity.

RESULTS

Component processing following PRT resulted in a significant drop in platelet recovery. Most PRT-PC bags fell below AABB guidelines for platelet count. PRT-PC also showed a decrease in clot strength and decreased aggregometry response. Platelet caspases were activated by PRT. Storage at 4°C improved platelet function. In PRT-FFP, prothrombin time and partial thromboplastin time (PT and aPTT) were prolonged; factors V, VII, VIII, and XI, protein C, and fibrinogen were significantly decreased. Free hemoglobin was elevated two-fold in PRT-RBC.

CONCLUSION

Blood components isolated by the PRP method from PRT-treated WB result in a high percentage of PC that fail to meet AABB guidelines. FFP also shows diminished coagulation capacity. However, PRT-RBC are comparable to control-RBC. PRT-WB retains acceptable hemostatic function but alternatives to the PRP method of component separation may be more suitable.

Use of Specialized Pro-Resolving Mediators to Alleviate Cold Platelet Storage Lesion

BACKGROUND

Cold-stored platelets are an attractive option for treatment of actively bleeding patients due to a reduced risk of septic complications and preserved hemostatic function compared to conventional room temperature-stored platelets. However, refrigeration causes increased platelet activation and aggregate formation. Specialized pro-resolving mediators (SPMs), cell signaling mediators biosynthesized from essential fatty acids, have been shown to modulate platelet function and activation. In this study, we sought to determine if SPMs could be used to inhibit cold-stored platelet activation.

METHODS

Platelets were collected from healthy donors (n = 4-7) and treated with SPMs (resolvin E1 [RvE1], maresin 1 [MaR1], and resolvin D2 [RvD2]) or vehicle (VEH; 0.1% EtOH). Platelets were stored without agitation in the cold and assayed on Days 0 and 7 of storage for platelet activation levels using flow cytometry, platelet count, aggregation response using impedance aggregometry, and nucleotide content using mass spectrometry.

RESULTS

Compared to VEH, SPM treatment inhibited GPIb shedding (all compounds), significantly reduced both PS exposure and activation of GPIIb/IIIa receptor (RvD2, MaR1), and preserved aggregation response to TRAP (RvD2, MaR1) after 7 days of storage. Similar to untreated cold-stored platelets, SPM-treated samples did not preserve platelet counts or block the release of P-Selectin. Nucleotide content was unaffected by SPM treatment in cold-stored platelets.

CONCLUSIONS

SPM treatment, particularly Mar1 and RvD2, led to reduced platelet activation and preserved platelet function after 7 days of storage in the cold. Future work is warranted to better elucidate the mechanism of action of SPMs on cold platelet function and activation.

Optimizing whole blood storage: hemostatic function of 35-day stored product in CPD, CP2D, and CPDA-1 anticoagulants

BACKGROUND

Transitioning from whole blood (WB) to components developed from efforts to maximize donor yield. Components are advantageous for specific derangements, but treating hemorrhage with components requires significantly more volume to provide similar effects to WB. Because storage lesion and waste remain problematic, this study examined hemostatic function of refrigerated WB stored for 35 days in anticoagulants citrate-phosphate-dextrose-adenosine (CPDA-1), citrate-phosphate-dextrose (CPD), or citrate-phosphate-double dextrose (CP2D).

METHODS

Refrigerated WB units from healthy donors were sampled over 35 days. Global hemostatic parameters were measured by thromboelastometry, thrombogram, platelet aggregometry, and platelet adhesion to collagen under shear conditions. The effects of transfusion filtration and mixing 35-day stored product with fresh WB were evaluated.

RESULTS

Countable platelets declined as aggregation clusters appeared in microscopy. While gross platelet agonist-induced aggregation declined over time, normalization revealed aggregation responses in remaining platelets. Peak thrombin generation increased over time. Clot strength diminished over storage in tissue factor-activated samples (normalized by filtration of aggregates). Functional fibrinogen responses remained consistent throughout. Filtration was necessary to maintain consistent platelet adhesion to collagen beyond collection day. Few differences were observed between anticoagulants, and stored/fresh mixing studies normalized coagulation parameters.

CONCLUSIONS

WB is easier to collect, store, and transfuse. WB provides platelets, an oft-neglected, critical resuscitation component, but their individual numbers decline as aggregates appear, resulting in diminished coagulation response. WB has better performance in these assays when examined at earlier time points, but expirations designated to specific anticoagulants appear arbitrary for hemostatic functionality, as little changes beyond 21 days regardless of anticoagulant.

Evaluation of a lyophilized platelet-derived hemostatic product

BACKGROUND

Current limitations of platelet shelf life to 5 days have led to an increasingly greater demand for hemostatic agents with greater longevity. The objective of this study was to evaluate the function of a lyophilized platelet-derived hemostatic product (thrombosome [TS]) as a potential alternative to fresh platelets.

METHODS

Platelets were collected from whole blood from healthy donors. TSs were reconstituted with water and added to various configurations of reassembled whole blood (platelets, plasma, and RBCs); measures included rotational thromboelastometry (ROTEM), optical aggregometry, mitochondrial function, calibrated automated thrombogram, collagen adhesion under flow (shear flow assay), and flow cytometry.

RESULTS

In ROTEM, no differences were observed between maximum clot formation values for contact pathway activation thromboelastometry tests with TSs or platelet samples. Significantly decreased aggregation was observed in the TSs versus platelets (p < 0.001 for all agonists). Flow cytometry measures demonstrated significant decreases in glycoprotein Ib expression and increases in phosphatidylserine expression in the TS group (p < 0.01). The calibrated automated thrombogram assay was suggestive (lag time and peak thrombin) that the TSs might have some thrombogenic properties. Measurements of mitochondrial function revealed that TSs had no functional mitochondria.

CONCLUSION

In this study, TSs were shown to have nonfunctional mitochondria. ROTEM measures revealed that the TSs had no impact on clot strength. Likewise, compared to platelets, the TSs displayed minimal aggregation, had significantly more phosphatidylserine (measure of activation status), but had the ability to adhere to a collagen surface under flow conditions and contribute to clot formation and induced greater thrombin generation.

Human primary fibroblasts perform similarly to MSCs in assays used to evaluate MSC safety and potency

BACKGROUND

Cellular therapeutic agents may benefit trauma patients by modulating the immune response to injury, and by reducing inflammation and vascular leakage. Administration of allogeneic mesenchymal stromal cells (MSCs) shows some benefit in preclinical and clinical trials, but less testing has been performed with other cell types. Human primary fibroblasts (FBs) were compared to MSCs in assays designed to evaluate MSCs to determine if these assays actually evaluate properties unique to MSCs or whether related cell types perform similarly.

STUDY DESIGN AND METHODS

MSC-related surface marker expression, tissue factor, and human leukocyte antigen-D related were evaluated by flow cytometry, and in vitro adipogenic and osteogenic differentiation potential were determined. Procoagulant activity was determined by thromboelastography. Two potency assays correlated with immunomodulation potential were utilized: the mixed lymphocyte reaction and indoleamine 2,3-dioxygenase enzyme activity assays.

RESULTS

Human primary FBs performed similarly to MSCs in assays designed to evaluate MSC characteristics and potency. Although similar for MSC-positive cell surface marker expression, FBs did not show robust adipose differentiation and expressed some level of markers not expected on MSCs.

CONCLUSIONS

Human primary FBs are very similar to human MSCs, at least in assays currently used to evaluate MSC potency. Preclinical and clinical testing are required to determine if FBs show similar activity to MSCs in vivo. If FBs show inferior activity in vivo, development of new MSC-specific potency assays will be necessary to evaluate properties relevant to their unique clinical benefits.

Cold storage of platelets in platelet additive solution: an in vitro comparison of two Food and Drug Administration-approved collection and storage systems

BACKGROUND

Refrigeration of platelets (PLTs) in a PLT additive solution (PAS) reduces PLT activation compared to storage in plasma and preserves function for at least 15 days. Currently only two PASs are licensed by the Food and Drug Administration, each for use with only one apheresis platform. In this study, we compared the metabolic, functional, and activation status of PLTs collected on a Trima apheresis collection system and stored refrigerated in Isoplate (ISO) PAS to PLTs collected on an Amicus collection system and stored refrigerated in Intersol (INT) PAS.

STUDY DESIGN AND METHODS

Apheresis PLTs (n = 4-7 donors) were collected on a Trima in ISO PAS or on an Amicus in INT PAS. PLTs were stored in a walk-in refrigerator (1-6°C) without agitation for long-term storage. Bags were assayed at Days 1, 5, 10, and 15 of storage. Measurements included PLT counts, pH, aggregation response, rotational thromboelastometry, and activation markers.

RESULTS

Cold-stored Trima-collected PLTs in ISO were slightly more hemostatic than Amicus-collected PLTs in INT and displayed better adhesion to collagen under flow conditions. Amicus-collected PLTs in INT showed increased microaggregate formation on Days 5 and 10 and a significant decrease in PLT count over storage. Trima-collected PLTs in ISO displayed better clot strength than Amicus-collected PLTs in INT.

CONCLUSION

Compared to cold-stored Amicus PLTs in INT, Trima PLTs in ISO display superior in vitro function and may be better suited for treatment of bleeding patients. Clinical studies are warranted to confirm these findings.

Time Course Expression Analysis of 1[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole Induction of Cytoprotection in Human Endothelial Cells

1[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole (CDDO-Im), a synthetic derivative of oleanolic acid that exhibits antioxidant and anti-inflammatory activity in several animal and in vitro models, has been shown to be beneficial if given after injury. Although induction of heme oxygenase 1 appears to be a major effector of cytoprotection, the mechanism by which the overall effect is mediated is largely unknown. This study evaluated temporal gene expression profiles to better characterize the early transcriptional events and their relationship to the dynamics of the cytoprotective response in human umbilical vein endothelial cells (HUVEC) to CDDO-Im. Time-course gene expression profiling was performed on HUVEC treated with CDDO-Im for 0.5, 1, 3, 6, and 24 hours. More than 10 000 genes were statistically altered in their expression in at least 1 time point across the time course. Large alterations in immediate-early gene expression were readily detectable within 0.5 hour after administration of CDDO-Im.

Cytoprotection of human endothelial cells from oxidant stress with CDDO derivatives: network analysis of genes responsible for cytoprotection

AIM

To identify drugs that may reduce the impact of oxidant stress on cell viability.

METHODS

Human umbilical vein endothelial cells were treated with 200 nmol/l CDDO-Im (imidazole) and CDDO-Me (methyl) after exposure to menadione and compared to vehicle-treated cells. Cell viability and cytotoxicity were assessed, and gene expression profiling was performed.

RESULTS

CDDO-Im was significantly more cytoprotective and less cytotoxic (p < 0.001) than CDDO-Me. Although both provided cytoprotection by induction of gene transcription, CDDO-Im induced more genes. In addition to a higher induction of the key cytoprotective gene heme oxygenase-1 (38.9-fold increase for CDDO-Im and 26.5-fold increase for CDDO-Me), CDDO-Im also induced greater expression of heat shock proteins (5.5-fold increase compared to 2.8-fold for CDDO-Me).

CONCLUSIONS

Both compounds showed good induction of heme oxygenase, which largely accounted for their cytoprotective effect. Differences were detected in cytotoxicity at higher doses, indicating that CDDO-Me was more cytotoxic than CDDO-Im. Significant differences were detected in the ability of CDDO-Im and CDDO-Me to affect differential gene transcription. CDDO-Im induced more genes than did CDDO-Me. The source of the differences in gene expression patterns between CDDO-Im and CDDO-Me was not determined but may be important in long-term use of this class of drugs.

Cytoprotection of human endothelial cells against oxidative stress by 1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole (CDDO-Im): application of systems biology to understand the mechanism of action

Cellular damage from oxidative stress, in particular following ischemic injury, occurs during heart attack, stroke, or traumatic injury, and is potentially reducible with appropriate drug treatment. We previously reported that caffeic acid phenethyl ester (CAPE), a plant-derived polyphenolic compound, protected human umbilical vein endothelial cells (HUVEC) from menadione-induced oxidative stress and that this cytoprotective effect was correlated with the capacity to induce heme oxygenase-1 (HMOX1) and its protein product, a phase II cytoprotective enzyme. To further improve this cytoprotective effect, we studied a synthetic triterpenoid, 1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole (CDDO-Im), which is known as a potent phase II enzyme inducer with antitumor and anti-inflammatory activities, and compared it to CAPE. CDDO-Im at 200nM provided more protection to HUVEC against oxidative stress than 20μM CAPE. We explored the mechanism of CDDO-Im cytoprotection with gene expression profiling and pathway analysis and compared to that of CAPE. In addition to potent up-regulation of HMOX1, heat shock proteins (HSP) were also found to be highly induced by CDDO-Im in HUVEC. Pathway analysis results showed that transcription factor Nrf2-mediated oxidative stress response was among the top canonical pathways commonly activated by both CDDO-Im and CAPE. Compared to CAPE, CDDO-Im up-regulated more HSP and some of them to a much higher extent. In addition, CDDO-Im treatment affected Nrf2 pathway more significantly. These findings may provide an explanation why CDDO-Im is a more potent cytoprotectant than CAPE against oxidative stress in HUVEC.