CCL25 chemokine-guided stem cell attraction: an assessment of possible benefits and risks

Mesenchymal stromal cells ameliorate chronic GVHD by boosting thymic regeneration in a CCR9-dependent manner in mice

Chronic graft-versus-host disease (cGVHD) is a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Mature donor T cells within the graft contribute to severe damage of thymic epithelial cells (TECs), which are known as key mediators in the continuum of acute GVHD (aGVHD) and cGVHD pathology. Mesenchymal stromal cells (MSCs) are reportedly effective in the prevention and treatment of cGVHD. In our previous pilot clinical trial in patients with refractory aGVHD, the incidence and severity of cGVHD were decreased, along with an increase in levels of blood signal joint T-cell receptor excision DNA circles after MSCs treatment, which indicated an improvement in thymus function of patients with GVHD, but the mechanisms leading to these effects remain unknown. Here, we show in a murine GVHD model that MSCs promoted the quantity and maturity of TECs as well as elevated the proportion of Aire-positive medullary TECs, improving both CD4+CD8+ double-positive thymocytes and thymic regulatory T cells, balancing the CD4:CD8 ratio in the blood. In addition, CCL25-CCR9 signaling axis was found to play an important role in guiding MSC homing to the thymus. These studies reveal mechanisms through which MSCs ameliorate cGVHD by boosting thymic regeneration and offer innovative strategies for improving thymus function in patients with GVHD.

Therapies with CCL25 require controlled release via microparticles to avoid strong inflammatory reactions

Background

Chemokine therapy with C–C motif chemokine ligand 25 (CCL25) is currently under investigation as a promising approach to treat articular cartilage degeneration. We developed a delayed release mechanism based on Poly (lactic-co-glycolic acid) (PLGA) microparticle encapsulation for intraarticular injections to ensure prolonged release of therapeutic dosages. However, CCL25 plays an important role in immune cell regulation and inflammatory processes like T-cell homing and chronic tissue inflammation. Therefore, the potential of CCL25 to activate immune cells must be assessed more thoroughly before further translation into clinical practice. The aim of this study was to evaluate the reaction of different immune cell subsets upon stimulation with different dosages of CCL25 in comparison to CCL25 released from PLGA particles.

Results

Immune cell subsets were treated for up to 5 days with CCL25 and subsequently analyzed regarding their cytokine secretion, surface marker expression, polarization, and migratory behavior. The CCL25 receptor C–C chemokine receptor type 9 (CCR9) was expressed to a different extent on all immune cell subsets. Direct stimulation of peripheral blood mononuclear cells (PBMCs) with high dosages of CCL25 resulted in strong increases in the secretion of monocyte chemoattractant protein-1 (MCP-1), interleukin-8 (IL-8), interleukin-1β (IL-1β), tumor-necrosis-factor-α (TNF-α) and interferon-γ (IFN-γ), upregulation of human leukocyte antigen-DR (HLA-DR) on monocytes and CD4⁺ T-cells, as well as immune cell migration along a CCL25 gradient. Immune cell stimulation with the supernatants from CCL25 loaded PLGA microparticles caused moderate increases in MCP-1, IL-8, and IL-1β levels, but no changes in surface marker expression or migration. Both CCL25-loaded and unloaded PLGA microparticles induced an increase in IL-8 and MCP-1 release in PBMCs and macrophages, and a slight shift of the surface marker profile towards the direction of M2-macrophage polarization.

Conclusions

While supernatants of CCL25 loaded PLGA microparticles did not provoke strong inflammatory reactions, direct stimulation with CCL25 shows the critical potential to induce global inflammatory activation of human leukocytes at certain concentrations. These findings underline the importance of a safe and reliable release system in a therapeutic setup. Failure of the delivery system could result in strong local and systemic inflammatory reactions that could potentially negate the benefits of chemokine therapy.

Stem cell recruitment based on scaffold features for bone tissue engineering

Stem-cell based therapy strategies are promising approaches for the treatment of bone defects. However, extensive cell expansion steps, the low rate of cell survival and uncontrolled differentiation of stem cells transplanted into the body currently remain key challenges in advancing stem cell therapeutics. An alternative strategy is to use specifically designed bone scaffolds to recruit endogenous stem cells upon implantation and to stimulate new bone formation and remodeling. Stem cell recruitment based on scaffold features for bone tissue engineering relies on the development of scaffolds that can effectively mobilize and recruit endogenous stem cells to the implantation site. This article addresses the recent advances in the recruitment of endogenous stem cells in applications of bone scaffolds, particularly focusing on chemical modification and physical characteristic modification of the scaffold for endogenous stem cell homing and recruitment. Finally, the continuing challenges and future directions of scaffold-based stem cell recruitment are discussed.

CCR9 Promotes Migration and Invasion of Lung Adenocarcinoma Cancer Stem Cells

Aim: CC chemokine receptor 9 (CCR9) interacts with its exclusive ligand CCL25, resulting in promoting tumor progression and metastasis. However, the effect and mechanisms of CCR9 on lung adenocarcinoma distant metastasis remain largely unknown. To preliminary clarify the underlying mechanisms, we investigate the correlation between CCR9 and ALDH1A1⁺cancer stem cells (CSCs), as well as the effect of CCR9 on the migration and invasion of CSCs. Methods: Immunohistochemistry was performed to detect the expression of CCR9 in lung adenocarcinoma tissues. The correlations of CCR9 with distant metastasis and overall survival were investigated. Serial paraffin-embedded tissue blocks were used to detect ALDH1A1⁺CSCs expression. The correlations between CCR9 expression and ALDH1A1⁺CSCs were evaluated. We further studied the effect of CCR9/CCL25 on the migration and invasion of CSCs using transwell assays. Results: There were positive correlations between CCR9 expression and distant metastasis, as well as poor overall survival. Patients with high CCR9 expression were more likely to develop distant metastasis and demonstrated poorer overall survival than patients with low CCR9 expression. In addition, there was positive correlation between the expression of CCR9 and ALDH1A1 in the same tumor microenvironment. ALDH^high CSCs demonstrated enhanced expression of CCR9 than ALDH^low cells. Further transwell assays demonstrated that the numbers of CSCs migrated or invaded in response to CCL25 were more than that without CCL25 stimulation. Additional application of anti-CCR9 antibody reversed the CCL25-induced migration and invasion of CSCs. Conclusions: In summary, our study demonstrated that CCR9/CCL25 promoted the migration and invasion of CSCs, which might contribute to distant metastasis and poor overall survival. Our findings provided evidence that CCR9/CCL25 could be used as novel therapeutic targets for lung adenocarcinoma.

Dose-Dependent Effect of Mesenchymal Stromal Cell Recruiting Chemokine CCL25 on Porcine Tissue-Engineered Healthy and Osteoarthritic Cartilage

Thymus-expressed chemokine (CCL25) is a potent cell attractant for mesenchymal stromal cells, and therefore it is a candidate for in situ cartilage repair approaches focusing on the recruitment of endogenous repair cells. However, the influence of CCL25 on cartilage is unknown. Accordingly, in this study, we investigated the effect of CCL25 on tissue-engineered healthy and osteoarthritic cartilage. Porcine chondrocytes were cultured in a three-dimensional (3D) micromass model that has been proven to mimic key-aspects of human cartilage and osteoarthritic alterations upon stimulation with tumor necrosis factor-α (TNF-α). Micromass cultures were stimulated with CCL25 (0, 0.05, 0.5, 5, 50, 500 nmol/L) alone or in combination with 0.6 nmol/L TNF-α for seven days. Effects were evaluated by life/dead staining, safranin O staining, histomorphometrical analysis of glycosaminoglycans (GAGs), collagen type II (COL2A1) real-time RT-PCR and Porcine Genome Array analysis. 500 nmol/L CCL25 led to a significant reduction of GAGs and COL2A1 expression and induced the expression of matrix metallopeptidases (MMP) 1, MMP3, early growth response protein 1 (EGR1), and superoxide dismutase 2 (SOD2). In concentrations lower than 500 nmol/L, CCL25 seems to be a candidate for in situ cartilage repair therapy approaches.