Syndecan-4 proteoliposomes enhance revascularization in a rabbit hind limb ischemia model of peripheral ischemia.

Regenerative therapeutics for treating peripheral arterial disease are an appealing strategy for creating more durable solutions for limb ischemia. In this work, we performed preclinical testing of an injectable formulation of syndecan-4 proteoliposomes combined with growth factors as treatment for peripheral ischemia delivered in an alginate hydrogel. We tested this therapy in an advanced model of hindlimb ischemia in rabbits with diabetes and hyperlipidemia. Our studies demonstrate enhancement in vascularity and new blood vessel growth with treatment with syndecan-4 proteoliposomes in combination with FGF-2 or FGF-2/PDGF-BB. The effects of the treatments were particularly effective in enhancing vascularity in the lower limb with a 2-4 increase in blood vessels in the treatment group in comparison to the control group. In addition, we demonstrate that the syndecan-4 proteoliposomes have stability for at least 28 days when stored at 4°C to allow transport and use in the hospital environment. In addition, we performed toxicity studies in the mice and found no toxic effects even when injected at high concentration. Overall, our studies support that syndecan-4 proteoliposomes markedly enhance the therapeutic potential of growth factors in the context of disease and may be promising therapeutics for inducing vascular regeneration in peripheral ischemia. STATEMENT OF SIGNIFICANCE: Peripheral ischemia is a common condition in which there is a lack of blood flow to the lower limbs. This condition can lead to pain while walking and, in severe cases, critical limb ischemia and limb loss. In this study, we demonstrate the safety and efficacy of a novel injectable therapy for enhancing revascularization in peripheral ischemia using an advanced large animal model of peripheral vascular disease using rabbits with hyperlipidemia and diabetes.

Secreted phospholipase A2 XIIA triggers a mitochondrial damage-induced senescence in chronic obstructive pulmonary disease fibroblasts.

RATIONALE: Lung fibroblast senescence is involved in the pathophysiology of chronic obstructive pulmonary disease (COPD). However, the mechanisms underlining this phenomenon are still poorly understood. Secreted phospholipases (sPLA2, a subclass of phospholipases) are secreted by senescent cells and can in turn induce senescence. However, their role in fibroblasts senescence in COPD is unknown. OBJECTIVES: The aim of this study was to analyze the role of sPLA2 in pulmonary fibroblast senescence. METHODS: Fibroblasts were isolated from patients with COPD and control subjects, and senescence markers and inflammatory profile was analyzed. sPLA2 levels were quantified in serum of COPD and controls. MAIN RESULTS: In comparison with non-smokers and smoker controls, senescent lung COPD fibroblasts exhibited a higher mRNA and protein expression of the sPLA2 isoform XIIA and of syndecan 4 (one of its receptors). sPLA2 XIIA induced in turn senescence of non-senescent pulmonary fibroblasts via a pathway involving consecutively syndecan 4, activation of MAPK and p-serine 727 STAT-3, increased mitochondrial ROS production, and activation of AMPK/p53. This pathway was associated with a specific inflammatory secretome (IL-10, IL-12 and TNFα), globally suggesting occurrence of a mitochondrial damage-induced senescence. COPD fibroblasts were more susceptible to this sPLA2 XIIA effect than cells from controls subjects. sPLA2 XIIA levels were significantly higher in serum from COPD patients as compared to controls. CONCLUSION: sPLA2 XIIA is involved in senescence in COPD and could be a potential target to dampen this process.

Suppressive effect of syndecan ectodomains and N-desulfated heparins on osteoclastogenesis via direct binding to macrophage-colony stimulating factor.

Syndecans, a family of cell surface heparan sulfate proteoglycans, regulate cell differentiation via binding of their heparan sulfate chains to growth factors and cytokines and play a role in tumor growth and progression, wound repair, and intestinal mucosal damage. However, the functional and mechanistic roles of syndecans in osteoclast differentiation and bone metabolism are yet unclear. Here, we demonstrated that post-translationally glycosylated ectodomains of syndecan-1 to 4 obtained from mammalian cells efficiently suppressed osteoclast differentiation compared to those obtained from Escherichia coli with no systems for glycosylation. A concomitant decrease in the expression of osteoclast markers such as nuclear factor of activated T cells 1 (NFATc1), c-Fos, and ATP6V0D2 was observed. In addition, heparan sulfate and selectively N-desulfated heparin derivatives with 2-O- and 6-O-sulfate groups and no anticoagulant activity in blood inhibited osteoclast differentiation. The inhibitory effects of syndecan ectodomains, heparan sulfate, and N-desulfated heparin derivatives on osteoclast differentiation were attributed to their direct binding to the macrophage-colony stimulating factor (M-CSF), resulting in the blocking of M-CSF-mediated downstream signals such as extracellular signal-regulated kinase (ERK), c-JUN N-terminal kinase (JNK), p38, and Akt. Furthermore, mice injected with syndecan ectodomains, heparan sulfate, and N-desulfated heparin derivatives into periosteal regions of calvaria showed reduction in the formation of tartrate-resistant acid phosphatase (TRAP)-positive mature osteoclasts on the calvarial bone surface, thereby exhibiting decreased bone resorption. Together, these results revealed a novel role of heparan sulfate chains of syndecan ectodomains in the regulation of osteoclast differentiation.

Syndecan-4 enhances PDGF-BB activity in diabetic wound healing.

UNLABELLED: Non-healing ulcers are a common consequence of long-term diabetes and severe peripheral vascular disease. These non-healing wounds are a major source of morbidity in patients with diabetes and place a heavy financial burden on the healthcare system. Growth factor therapies are an attractive strategy for enhancing wound closure in non-healing wounds but have only achieved mixed results in clinical trials. Platelet derived growth factor-BB (PDGF-BB) is the only currently approved growth factor therapy for non-healing wounds. However, PDGF-BB therapy is not effective in many patients and requires high doses that increase the potential for side effects. In this work, we demonstrate that syndecan-4 delivered in a proteoliposomal formulation enhances PDGF-BB activity in diabetic wound healing. In particular, syndecan-4 proteoliposomes enhance the migration of keratinocytes derived from patients with diabetes. In addition, syndecan-4 proteoliposomes sensitize keratinocytes to PDGF-BB stimulation, enhancing the intracellular signaling response to PDGF-BB. We further demonstrated that co-therapy with syndecan-4 proteoliposomes enhanced wound closure in diabetic, hyperlipidemic ob/ob mice. Wounds treated with both syndecan-4 proteoliposomes and PDGF-BB had increased re-epithelization and angiogenesis in comparison to wounds treated with PDGF-BB alone. Moreover, the wounds treated with syndecan-4 proteoliposomes and PDGF-BB also had increased M2 macrophages and reduced M1 macrophages, suggesting syndecan-4 delivery induces immunomodulation within the healing wounds. Together our findings support that syndecan-4 proteoliposomes markedly improve PDGF-BB efficacy for wound healing and may be useful in enhancing treatments for non-healing wounds. STATEMENT OF SIGNIFICANCE: Non-healing wounds are major healthcare issue for patients with diabetes and peripheral vascular disease. Growth factor therapies have potential for healing chronic wounds but have not been effective for many patients. PDGF-BB is currently the only approved growth factor for enhancing wound healing. However, it has not seen widespread adoption due to limited efficacy and high cost. In this work, we have developed an enhancing agent that improves the activity of PDGF-BB in promoting wound healing in animals with diabetes. This co-therapy may be useful in improving the efficacy of PDGFBB and enhance its safety through lowering the dose of growth factor needed to improve wound healing.

Syndecan-4 Enhances Therapeutic Angiogenesis after Hind Limb Ischemia in Mice with Type 2 Diabetes.

Delivering syndecan-4 with FGF-2 improves the effectiveness of FGF-2 therapy for ischemia in the diabetic disease state. The syndecan-4 proteoliposomes significantly enhance in vitro tubule formation as well as blood perfusion and vessel density in the ischemic hind limbs of diseased ob/ob mice. Syndecan-4 therapy also induces a marked immunomodulation in the tissues, increasing the polarization of macrophages toward the M2 phenotype.