Delivery Of FTY720 Research Articles

FTY720 in immuno-regenerative and wound healing technologies for muscle, epithelial and bone regeneration.

In 2010, the FDA approved the administration of FTY720, S1P lipid mediator, as a therapy to treat relapsing forms of multiple sclerosis. FTY720 was found to sequester pro-inflammatory lymphocytes within the lymph node, preventing them from causing injury to the central nervous system due to inflammation. Studies harnessing the anti-inflammatory properties of FTY720 as a pro-regenerative strategy in wound healing of muscle, bone and mucosal injuries are currently being performed. This in-depth review discusses the current regenerative impact of FTY720 due to its anti-inflammatory effect stratified into an assessment of wound regeneration in the muscular, skeletal, and epithelial systems. The regenerative effect of FTY720 in vivo was characterized in three animal models, with differing delivery mechanisms emerging in the last 20years. In these studies, local delivery of FTY720 was found to increase pro-regenerative immune cell phenotypes (neutrophils, macrophages, monocytes), vascularization, cell proliferation and collagen deposition. Delivery of FTY720 to a localized wound environment demonstrated increased bone, muscle, and mucosal regeneration through changes in gene and cytokine production primarily by controlling the local immune cell phenotypes. These changes in gene and cytokine production reduced the inflammatory component of wound healing and increased the migration of pro-regenerative cells (neutrophils and macrophages) to the wound site. The application of FTY720 delivery using a biomaterial has demonstrated the ability of local delivery of FTY720 to promote local wound healing leveraging an immunomodulatory mechanism.

Localized delivery of FTY-720 from 3D printed cell-laden gelatin/silk fibroin composite scaffolds for enhanced vascularized bone regeneration

Three-dimensional (3D) printing can construct products with accurate complex architecture. Engineered bone tissues that can promote vascularization and regulate directed differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) are considered as an ideal substitute the healing of bone for bone defects treatment. Herein, we fabricated a 3D printed BMSCs-laden scaffold using methacrylated gelatin and methacrylated silk fibroin (GelMA/SFMA) based bioinks along with localized sustained release of a small molecule drug fingolimod (FTY-720) for the synergistic interactions of vascularization and osteogenesis during bone repair. The GelMA/SFMA bioink showed significant advantages due to their tunable rheology, rapid thermal crosslinking, and improved shape fidelity following bioprinting. The in vitro experiments demonstrated that high cell viability of cells-laden constructs, while FTY-720-containing scaffolds significantly promoted migration and induced tube-like structure formation of human umbilical vein endothelial cells (HUVECs) as well as expressed high osteogenic-related genes expression of BMSCs. The implantation in a critical-size rat cranial defect model further revealed that FTY-720-loaded scaffolds significantly promoted vascularization and bone regeneration. Furthermore, scaffolds carrying BMSCs and FTY-720 were more osteogenic in vivo than scaffolds carrying BMSCs alone. Therefore, the constructed BMSCs-laden and FTY-720-loaded GelMA/SFMA scaffolds would be an ideal candidate with required structure and desired function for vascularization of bone regeneration.

Local delivery of FTY720 induces neutrophil activation through chemokine signaling in an oronasal fistula model

PurposeCleft palate repair surgeries lack a regenerative reconstructive option and, in many cases, develop complications including oronasal fistula (ONF). Our group has developed a novel murine phenocopy of ONF to study the oral cavity wound healing program. Using this model, our team previously identified that delivery of FTY720 on a nanofiber scaffold had a unique immunomodulatory effect directing macrophages and monocytes into a pro-regenerative state during ONF healing. Here, the objective of this study was to determine the effects of local biomaterial-based FTY720 delivery in the ONF model on the early bulk gene expression and neutrophil phenotypic response within the regenerating tissue.MethodsUsing a mouse model of ONF formation, a palate defect was created and was treated with FTY720 nanofiber scaffolds or (blank) vehicle control nanofibers. At 1 and 3 days post-implantation, ONF oral mucosal tissue from the defect region was collected for RNA sequencing analysis or flow cytometry. For the RNA-seq expression profiling, intracellular pathways were assessed using the KEGG Pathway database and Gene Ontology (GO) Terms enrichment interactive graph. To assess the effects of FTY720 on different neutrophil subpopulations, flow cytometry data was analyzed using pseudotime analysis based on Spanning-tree Progression Analysis of Density-normalized Events (SPADE).ResultsRNA sequencing analysis of palate mucosa injured tissue identified 669 genes that were differentially expressed (DE) during the first 3 days of ONF wound healing after local delivery of FTY720, including multiple genes in the sphingolipid signaling pathway. Evaluation of the DE genes at the KEGG Pathway database also identified the inflammatory immune response pathways (chemokine signaling, cytokine-cytokine receptor interaction, and leukocyte transendothelial migration), and the Gene Ontology enrichment analysis identified neutrophil chemotaxis and migration terms. SPADE dendrograms of CD11b+Ly6G+ neutrophils at both day 1 and day 3 post-injury showed significantly distinct subpopulations of neutrophils in oral mucosal defect tissue from the FTY720 scaffold treatment group compared to the vehicle control group (blank). Increased expression of CD88 and Vav1, among other genes, were found and staining of the ONF area demonstrated increased VAV1 staining in FTY720‐treated healing oral mucosa.ConclusionTreatment of oral mucosal defects using FTY720 scaffolds is a promising new immunotherapy to improve healing outcomes and reducing ONF formation during cleft palate surgical repair. Local delivery of FTY720 nanofiber scaffolds during ONF healing significantly shifted early gene transcription associated with immune cell recruitment and modulation of the immune microenvironment results in distinct neutrophil subpopulations in the oral mucosal defect tissue that provides a critical shift toward pro-regenerative immune signaling.

Local delivery of FTY720 in mesoporous bioactive glass improves bone regeneration by synergistically immunomodulating osteogenesis and osteoclastogenesis.

The addition of osteoimmunology drugs to bone repair materials is beneficial to bone regeneration by regulating the local immune microenvironment. Fingolimod (FTY720) has been reported to be an osteoimmunology drug that promotes osteogenesis. However, there is no ideal biomaterial for the sustained release of FTY720 in the bone defect areas. In the present work, FTY720 loaded mesoporous bioactive glass (FTY720@MBGs) was successfully prepared based on the mesoporous properties of MBGs and electrostatic attraction. FTY720 achieved a sustained release for 7 days. The in vitro study found that FTY720@MBGs could synergistically promote osteogenesis and inhibit osteoclastogenesis due to their ability to promote macrophages toward the M2 phenotype. The in vivo study confirmed that FTY720@MBGs could significantly improve bone regeneration. This study provides new strategies for designing smart cell-instructive biomaterials that can play a role in all bone healing processes from early inflammation to bone reconstruction.

Improving hard palate wound healing using immune modulatory autotherapies

Oral cavity wound healing occurs in an environment that sustains ongoing physical trauma and is rich in bacteria. Despite this, injuries to the mucosal surface often heal faster than cutaneous wounds and leave less noticeable scars. Patients undergoing cleft palate repair have a high degree of wound healing complications with up to 60% experiencing oronasal fistula (ONF) formation. In this study, we developed a mouse model of hard palate mucosal injury, to study the endogenous injury response during oral cavity wound healing and ONF formation. Immunophenotyping of the inflammatory infiltrate following hard palate injury showed delayed recruitment of non-classical LY6Clo monocytes and failure to resolve inflammation. To induce a pro-regenerative inflammatory response, delivery of FTY720 nanofiber scaffolds following hard palate mucosal injury promoted complete ONF healing and was associated with increased LY6Clo monocytes and pro-regenerative M2 macrophages. Alteration in gene expression with FTY720 delivery included increased Sox2 expression, reduction in pro-inflammatory IL-1, IL-4 and IL-6 and increased pro-regenerative IL-10 expression. Increased keratinocyte proliferation during ONF healing was observed at day 5 following FTY720 delivery. Our results show that local delivery of FTY720 from nanofiber scaffolds in the oral cavity enhances healing of ONF, occurring through multiple immunomodulatory mechanisms. Statement of SignificanceWound healing complications occur in up to 60% of patients undergoing cleft palate repair where an oronasal fistula (ONF) develops, allowing food and air to escape from the nose. Using a mouse model of palate mucosal injury, we explored the role of immune cell infiltration during ONF formation. Delivery of FTY720, an immunomodulatory drug, using a nanofiber scaffold into the ONF was able to attract anti-inflammatory immune cells following injury that enhanced the reepithelization process. ONF healing at day 5 following FTY720 delivery was associated with altered inflammatory and epithelial transcriptional gene expression, increased anti-inflammatory immune cell infiltration, and increased proliferation. These findings demonstrate the potential efficacy of immunoregenerative therapies to improve oral cavity wound healing.

Local delivery of FTY720 and NSCs on electrospun PLGA scaffolds improves functional recovery after spinal cord injury.

Spinal cord injury (SCI) is a common issue in the clinic that causes severe motor and sensory dysfunction below the lesion level. FTY720, also known as fingolimod, has recently been reported to exert a positive effect on the recovery from a spinal cord injury. Through local delivery to the lesion site, FTY720 effectively integrates with biomaterials, and the systemic adverse effects are alleviated. However, the effects of the proper mass ratio of FTY720 in biomaterials on neural stem cell (NSC) proliferation and differentiation, as well as functional recovery after SCI, have not been thoroughly investigated. In our study, we fabricated electrospun poly (lactide-co-glycolide) (PLGA)/FTY720 scaffolds at different mass ratios (0.1%, 1%, and 10%) and characterized these scaffolds. The effects of electrospun PLGA/FTY720 scaffolds on NSC proliferation and differentiation were measured. Then, a rat model of spinal transection was established to investigate the effects of PLGA/FTY720 scaffolds loaded with NSCs. Notably, 1% PLGA/FTY720 scaffolds exerted the best effects on the proliferation and differentiation of NSCs and 10% PLGA/FTY720 was cytotoxic to NSCs. Based on the Basso, Beattie, and Bresnahan (BBB) score, HE staining and immunofluorescence staining, the PLGA/FTY720 scaffold loaded with NSCs effectively promoted the recovery of spinal cord function. Thus, FTY720 properly integrated with electrospun PLGA scaffolds, and electrospun PLGA/FTY720 scaffolds loaded with NSCs may have potential applications for SCI as a nerve implant.

Delivery of Immunomodulatory Microparticles in a Murine Model of Rotator Cuff Tear

ABSTRACTFull thickness rotator cuff tears (RCT) and the associated muscle degeneration that results due to this injury presents a significant clinical burden. The prevention or recovery from this degeneration requires the synchronized behavior of many cells that participate in regeneration. Strategies that tune the inflammatory cascade that is initiated after injury serves as a powerful way to influence tissue repair. Here, we use the local, sustained delivery of the immunomodulatory small molecule FTY720 to examine whether the recruitment of pro-regenerative myeloid cells affects the healing outcome. We find that PLGA microparticles have an atrophic effect on the muscle that is ameliorated with the release of FTY720. However, the inability of FTY720 delivery to induce pro-regenerative monocyte and macrophage recruitment and our findings demonstrating enrichment of CD4+ T cells suggest that effects of this small molecule are context dependent and that the underlying mechanisms behind this RCT associated muscle degeneration require further studies.

Delivery of Immunomodulatory Microparticles in a Murine Model of Rotator Cuff Tear.

Full thickness rotator cuff tears (RCT) and the associated muscle degeneration that results due to this injury presents a significant clinical burden. The prevention or recovery from this degeneration requires the synchronized behavior of many cells that participate in regeneration. Strategies that tune the inflammatory cascade that is initiated after injury serves as a powerful way to influence tissue repair. Here, we use the local, sustained delivery of the immunomodulatory small molecule FTY720 to examine whether the recruitment of pro-regenerative myeloid cells affects the healing outcome. We find that PLGA microparticles have an atrophic effect on the muscle that is ameliorated with the release of FTY720. However, the inability of FTY720 delivery to induce pro-regenerative monocyte and macrophage recruitment and our findings demonstrating enrichment of CD4+ T cells suggest that effects of this small molecule are context dependent and that the underlying mechanisms behind this RCT associated muscle degeneration require further studies.

Targeting the S1P/S1PR1 axis mitigates cancer-induced bone pain and neuroinflammation.

Metastatic bone pain is the single most common form of cancer pain and persists as a result of peripheral and central inflammatory, as well as neuropathic mechanisms. Here, we provide the first characterization of sphingolipid metabolism alterations in the spinal cord occurring during cancer-induced bone pain (CIBP). Following femoral arthrotomy and syngenic tumor implantation in mice, ceramides decreased with corresponding increases in sphingosine and the bioactive sphingolipid metabolite, sphingosine 1-phosphate (S1P). Intriguingly, de novo sphingolipid biosynthesis was increased as shown by the elevations of dihydro-ceramides and dihydro-S1P. We next identified the S1P receptor subtype 1 (S1PR1) as a novel target for therapeutic intervention. Intrathecal or systemic administration of the competitive and functional S1PR1 antagonists, TASP0277308 and FTY720/Fingolimod, respectively, attenuated cancer-induced spontaneous flinching and guarding. Inhibiting CIBP by systemic delivery of FTY720 did not result in antinociceptive tolerance over 7 days. FTY720 administration enhanced IL-10 in the lumbar ipsilateral spinal cord of CIBP animals and intrathecal injection of an IL-10 neutralizing antibody mitigated the ability of systemic FTY720 to reverse CIBP. FTY720 treatment was not associated with alterations in bone metabolism in vivo. Studies here identify a novel mechanism to inhibit bone cancer pain by blocking the actions of the bioactive metabolites S1P and dihydro-S1P in lumbar spinal cord induced by bone cancer and support potential fast-track clinical application of the FDA-approved drug, FTY720, as a therapeutic avenue for CIBP.

FTY720 promotes pulmonary fibrosis when administered during the remodelling phase following a bleomycin-induced lung injury

Fibrosis complicates numerous pathologies including interstitial lung diseases. Sphingosine analogs such as FTY720 can alleviate lung injury-induced fibrosis in murine models. Contradictorily, FTY720 also promotes in vitro processes normally leading to fibrosis and high doses in vivo foster lung fibrosis by enhancing vascular leakage into the lung. The goal of this study was to determine the effect of low doses of FTY720 on lung fibrosis triggered by an acute injury in mice. We first defined the time-boundaries delimiting the inflammatory and remodelling phases of an injury elicited by bleomycin based on neutrophil counts, total lung capacity and lung stiffness. Thereafter, FTY720 (0.1 mg/kg) was delivered during either the inflammatory or the remodelling phases of bleomycin-induced injury. While FTY720 decreased fibrosis by 60% and lung stiffness by 28% when administered during the inflammatory phase, it increased fibrosis (2.1-fold) and lung stiffness (1.7-fold) when administered during the remodelling phase. FTY720-induced worsening of fibrosis was associated with an increased expression of connective tissue growth factor, but not with vascular leakage into the lung. Thus, the timing of FTY720 delivery following a bleomycin-induced lung injury determines pro-vs anti-fibrotic outcomes.

Dual Affinity Heparin-Based Hydrogels Achieve Pro-Regenerative Immunomodulation and Microvascular Remodeling.

The immune response to biomaterial implants critically regulates functional outcomes such as vascularization, transplant integration/survival, and fibrosis. To create "immunologically smart" materials, the host-material response may be engineered to optimize the recruitment of pro-regenerative leukocyte subsets which mature into corresponding wound-healing macrophages. We have recently identified a unique feature of pro-regenerative Ly6Clow monocytes that is a higher expression of both the bioactive lipid receptor sphingosine-1-phosphate receptor 3 (S1PR3) and the stromal derived factor-1α (SDF-1α) receptor CXCR4. Therefore, we designed a bifunctional hydrogel to harnesses a mechanistic synergy between these signaling axes to enhance the recruitment of endogenous pro-regenerative monocytes. To overcome the challenge of codelivering two physiochemically distinct molecules-a large hydrophilic protein and hydrophobic small molecule-we engineered a dual affinity hydrogel that exploits the growth factor affinity of a heparin derivative (Hep-N) and lipid chaperone activity of albumin. The sphingosine analog FTY720 and SDF-1α are successfully loaded and coreleased from the Hep-N-functionalized PEG-DA hydrogels while maintaining bioactivity. Placement of these hydrogels into a murine partial thickness skin wound demonstrates that corelease of FTY720 and SDF-1α yields superior recruitment of myeloid cells to the implant interface compared to either factor alone. Although in vivo delivery of FTY720 or SDF-1α individually promotes the enhanced recruitment of Ly-6Clow anti-inflammatory monocytes, codelivery enhances the early accumulation and persistence of the differentiated wound healing CD206+ macrophages in the tissue surrounding the gel. Co-delivery similarly promoted the synergistic expansion of vasculature adjacent to the implant, a key step in tissue healing. Taken together, these findings suggest that the combination of chemotactic molecules may provide additional maturation signals to the infiltrating leukocytes to facilitate macrophage transition and vascular network expansion, thus, ultimately, potentiating tissue repair. The coupling of multiple pro-regenerative biological cues provides a foundation for more fine-tuned immunoregenerative modulation to facilitate tissue repair.

The emerging role of FTY720 (Fingolimod) in cancer treatment.

FTY720 (Fingolimod) is a clinically approved immunomodulating therapy for multiple sclerosis that sequesters T-cells to lymph nodes through functional antagonism of sphingosine-1-phosphate 1 receptor. FTY720 also demonstrates a proven efficacy in multiple in vitro and in vivo cancer models, suggesting a potential therapeutic role in cancer patients. A potential anticancer mechanism of FTY720 is through the inhibition of sphingosine kinase 1, a proto-oncogene with in vitro and clinical cancer association. In addition, FTY720's anticancer properties may be attributable to actions on several other molecular targets. This study focuses on reviewing the emerging evidence regarding the anticancer properties and molecular targets of FTY720. While the clinical transition of FTY720 is currently limited by its immune suppression effects, studies aiming at FTY720 delivery and release together with identifying its key synergetic combinations and relevant patient subsets may lead to its rapid introduction into the clinic.

Fingolimod (FTY720) enhances hippocampal synaptic plasticity and memory in Huntington's disease by preventing p75NTR up-regulation and astrocyte-mediated inflammation.

Huntington's disease (HD) is a hereditary neurodegenerative disorder characterized by motor and cognitive impairments, involving striatum, cortex and hippocampus. Synaptic and memory dysfunction in HD mouse models have been related to low levels of brain-derived neurotrophic factor (BDNF) and imbalance between TrkB and p75(NTR) receptors. In addition, astrocyte over-activation has also been suggested to contribute to HD cognitive deficits. Fingolimod (FTY720), a modulator of sphingosine-1 phosphate (S1P) receptors, has been shown to increase BDNF levels and to reduce astrogliosis, proving its potential to regulate trophic support and inflammatory response. In this view, we have investigated whether FTY720 improves synaptic plasticity and memory in the R6/1 mouse model of HD, through regulation of BDNF signaling and astroglial reactivity. Chronic administration of FTY720 from pre-symptomatic stages ameliorated long-term memory deficits and dendritic spine loss in CA1 hippocampal neurons from R6/1 mice. Furthermore, FTY720 delivery prevented astrogliosis and over-activation of nuclear factor kappa beta (NF-κB) signaling in the R6/1 hippocampus, reducing tumor necrosis factor alpha (TNFα) and induced nitric oxide synthase (iNOS) levels. TNFα decrease correlated with the normalization of p75(NTR) expression in the hippocampus of FTY720-treated R6/1 mice, thus preventing p75(NTR)/TrkB imbalance. In addition, FTY720 increased cAMP levels and promoted phosphorylation of CREB and RhoA in the hippocampus of R6/1 mice, further supporting its role in the enhancement of synaptic plasticity. Our findings provide new insights into the mechanism of action of FTY720 and reveal a novel therapeutic strategy to treat memory deficits in HD.

Local delivery of FTY720 in PCL membrane improves SCI functional recovery by reducing reactive astrogliosis

FTY720 has recently been approved as an oral drug for treating relapsing forms of multiple sclerosis, and exerts its therapeutic effect by acting as an immunological inhibitor targeting the sphingosine-1-phosphate (S1P) receptor subtype (S1P1) of T cells. Recently studies demonstrated positive efficacy of this drug on spinal cord injury (SCI) in animal models after systemic administration, albeit with significant adverse side effects. We hereby hypothesize that localized delivery of FTY720 can promote SCI recovery by reducing pathological astrogliosis. The mechanistic functions of FTY720 were investigated in vitro and in vivo utilizing immunofluorescence, histology, MRI and behavioral analysis. The in vitro study showed that FTY720 can reduce astrocyte migration and proliferation activated by S1P. FTY720 can prolong internalization of S1P1 and exert antagonistic effects on S1P1. In vivo study of SCI animal models demonstrated that local delivery of FTY720 with polycaprolactone (PCL) membrane significantly decreased S1P1 expression and glial scarring compared with the control group. Furthermore, FTY720-treated groups exhibited less cavitation volume and neuron loss, which significantly improved recovery of motor function. These findings demonstrated that localized delivery of FTY720 can promote SCI recovery by targeting the S1P1 receptor of astrocytes, provide a new therapeutic strategy for SCI treatment.

Exogenous S1P Exposure Potentiates Ischemic Stroke Damage That Is Reduced Possibly by Inhibiting S1P Receptor Signaling.

Initial and recurrent stroke produces central nervous system (CNS) damage, involving neuroinflammation. Receptor-mediated S1P signaling can influence neuroinflammation and has been implicated in cerebral ischemia through effects on the immune system. However, S1P-mediated events also occur within the brain itself where its roles during stroke have been less well studied. Here we investigated the involvement of S1P signaling in initial and recurrent stroke by using a transient middle cerebral artery occlusion/reperfusion (M/R) model combined with analyses of S1P signaling. Gene expression for S1P receptors and involved enzymes was altered during M/R, supporting changes in S1P signaling. Direct S1P microinjection into the normal CNS induced neuroglial activation, implicating S1P-initiated neuroinflammatory responses that resembled CNS changes seen during initial M/R challenge. Moreover, S1P microinjection combined with M/R potentiated brain damage, approximating a model for recurrent stroke dependent on S1P and suggesting that reduction in S1P signaling could ameliorate stroke damage. Delivery of FTY720 that removes S1P signaling with chronic exposure reduced damage in both initial and S1P-potentiated M/R-challenged brain, while reducing stroke markers like TNF-α. These results implicate direct S1P CNS signaling in the etiology of initial and recurrent stroke that can be therapeutically accessed by S1P modulators acting within the brain.

M15 Fingolimod (FTY720) Enhances Hippocampal Synaptic Plasticity and Memory in Huntington's Disease by Preventing P75NTR/TRKB Imbalance

Huntington’s disease (HD) is a hereditary neurodegenerative disorder characterised by motor disturbances and cognitive impairment, the latter being increasingly associated to hippocampal dysfunction. Brain derived neurotrophic factor (BDNF) is a potent neurotrophin that modulates hippocampal synaptic plasticity through its receptors TrkB and p75NTR. Fingolimod (FTY720), an agonist of sphingosine-1 phosphate receptors currently used to treat Multiple Sclerosis, has recently been shown to increase BDNF levels. We have investigated the potential beneficial effects of FTY720 in treating synaptic and memory impairments in a R6/1 HD mouse model. FTY720 delivery promoted BDNF synthesis, but not pro-BDNF cleavage, in the R6/1 hippocampus. Chronic administration of FTY720 rescued long-term memory deficits in R6/1 mice and increased the number of dendritic spines in the CA1 area of the hippocampus. R6/1 mice displayed an imbalance of p75NTR/TrkB in the hippocampus, which was prevented by FTY720 treatment through negative modulation of p75NTR. As a result, R6/1 mice showed reduced RhoA activity and higher activation of TrkB and CREB, supporting the role of FTY720 in the enhancement of synaptic plasticity. Our findings define a new mechanism for the action of FTY720 in neurodegenerative diseases, and propose this drug as a suitable candidate for treating cognitive dysfunction in HD.

Delivery of bioactive lipids from composite microgel-microsphere injectable scaffolds enhances stem cell recruitment and skeletal repair.

In this study, a microgel composed of chitosan and inorganic phosphates was used to deliver poly(lactic-co-glycolic acid) (PLAGA) microspheres loaded with sphingolipid growth factor FTY720 to critical size cranial defects in Sprague Dawley rats. We show that sustained release of FTY720 from injected microspheres used alone or in combination with recombinant human bone morphogenic protein-2 (rhBMP2) improves defect vascularization and bone formation in the presence and absence of rhBMP2 as evaluated by quantitative microCT and histological measurements. Moreover, sustained delivery of FTY720 from PLAGA and local targeting of sphingosine 1-phosphate (S1P) receptors reduces CD45+ inflammatory cell infiltration, promotes endogenous recruitment of CD29+CD90+ bone progenitor cells and enhances the efficacy of rhBMP2 from chitosan microgels. Companion in vitro studies suggest that selective activation of sphingosine receptor subtype-3 (S1P3) via FTY720 treatment induces smad-1 phosphorylation in bone-marrow stromal cells. Additionally, FTY720 enhances stromal cell-derived factor-1 (SDF-1) mediated chemotaxis of CD90+CD11B-CD45- bone progenitor cells in vitro after stimulation with rhBMP2. We believe that use of such small molecule delivery formulations to recruit endogenous bone progenitors may be an attractive alternative to exogenous cell-based therapy.

Delivery of S1P receptor‐targeted drugs via biodegradable polymer scaffolds enhances bone regeneration in a critical size cranial defect

Biodegradable polymer scaffolds can be used to deliver soluble factors to enhance osseous remodeling in bone defects. To this end, we designed a poly(lactic-co-glycolic acid) (PLAGA) microsphere scaffold to sustain the release of FTY720, a selective agonist for sphingosine 1-phosphate (S1P) receptors. The microsphere scaffolds were created from fast degrading 50:50 PLAGA and/or from slow-degrading 85:15 PLAGA. Temporal and spatial regulation of bone remodeling depended on the use of appropriate scaffolds for drug delivery. The release profiles from the scaffolds were used to design an optimal delivery system to treat critical size cranial defects in a rodent model. The ability of local FTY720 delivery to maximize bone regeneration was evaluated with micro-computed tomography (microCT) and histology. Following 4 weeks of defect healing, FTY720 delivery from 85:15 PLAGA scaffolds resulted in a significant increase in bone volumes in the defect region compared to the controls. A 85:15 microsphere scaffolds maintain their structural integrity over a longer period of time, and cause an initial burst release of FTY720 due to surface localization of the drug. This encourages cellular in-growth and an increase in new bone formation.

The promotion of mandibular defect healing by the targeting of S1P receptors and the recruitment of alternatively activated macrophages

Endogenous signals originating at the site of injury are involved in the paracrine recruitment, proliferation, and differentiation of circulating progenitor and diverse inflammatory cell types. Here, we investigate a strategy to exploit endogenous cell recruitment mechanisms to regenerate injured bone by local targeting and activation of sphingosine-1-phosphate (S1P) receptors. A mandibular defect model was selected for evaluating regeneration of bone following trauma or congenital disease. The particular challenges of mandibular reconstruction are inherent in the complex anatomy and function of the bone given that the area is highly vascularized and in close proximity to muscle. Nanofibers composed of poly(dl-lactide-co-glycolide) (PLAGA) and polycaprolactone (PCL) were used to delivery FTY720, a targeted agonist of S1P receptors 1 and 3. In vitro culture of bone progenitor cells on drug-loaded constructs significantly enhanced SDF1α mediated chemotaxis of bone marrow mononuclear cells. In vivo results show that local delivery of FTY720 from composite nanofibers enhanced blood vessel ingrowth and increased recruitment of M2 alternatively activated macrophages, leading to significant osseous tissue ingrowth into critical sized defects after 12 weeks of treatment. These results demonstrate that local activation of S1P receptors is a regenerative cue resulting in recruitment of wound healing or anti-inflammatory macrophages and bone healing. Use of such small molecule therapy can provide an alternative to biological factors for the clinical treatment of critical size craniofacial defects.

A novel liposomal formulation of FTY720 (Fingolimod) for promising enhanced targeted delivery

We describe here the development and characterization of the physicochemical and pharmacokinetic properties of a novel liposomal formulation for FTY720 delivery, LP-FTY720. The mean diameter of LP-FTY720 was ~157nm, and the FTY720 entrapment efficiency was ~85%. The liposomal formulation protected FTY720 from degradation in aqueous buffer and showed toxicity in CLL patient B cells comparable to that of free FTY720. Following intravenous injection in ICR mice, LP-FTY720 had an increased elimination phase half-life (~28 vs. ~19hr) and decreased clearance (235 vs. 778mL/h/kg) compared to the free drug. Antibodies against CD19, CD20 and CD37 were incorporated into LP-FTY720, which provided targeted delivery to CLL patient B cells and thus achieved higher killing efficacy. The novel liposomal carrier of FTY720 demonstrated improved pharmacokinetic properties, comparable activity, and a potential platform for targeted delivery to CLL by overcoming the limited application of free FTY720 to B malignancy treatment. From the Clinical EditorThis team reports on a novel liposomal formulation for FTY720 delivery, demonstrating improved pharmacokinetic properties, comparable activity, and a potential platform for targeted delivery to CLL using antibodies incorporated in the liposomes. The method expected to overcome the limited application of free FTY720 to B malignancy treatment.