Changes in the levels of eicosanoids in cats naturally and experimentally infected with Dirofilaria immitis

Human and feline adipose-derived mesenchymal stem cells have comparable phenotype, immunomodulatory functions, and transcriptome

Background

Adipose-derived mesenchymal stem cells (ASCs) are a promising cell therapy to treat inflammatory and immune-mediated diseases. Development of appropriate pre-clinical animal models is critical to determine safety and attain early efficacy data for the most promising therapeutic candidates. Naturally occurring diseases in cats already serve as valuable models to inform human clinical trials in oncologic, cardiovascular, and genetic diseases. The objective of this study was to complete a comprehensive side-by-side comparison of human and feline ASCs, with an emphasis on their immunomodulatory capacity and transcriptome.

Methods

Human and feline ASCs were evaluated for phenotype, immunomodulatory profile, and transcriptome. Additionally, transwells were used to determine the role of cell-cell contact in ASC-mediated inhibition of lymphocyte proliferation in both humans and cats.

Results

Similar to human ASCs, feline ASCs were highly proliferative at low passages and fit the minimal criteria of multipotent stem cells including a compatible surface protein phenotype, osteogenic capacity, and normal karyotype. Like ASCs from all species, feline ASCs inhibited mitogen-activated lymphocyte proliferation in vitro, with or without direct ASC-lymphocyte contact. Feline ASCs mimic human ASCs in their mediator secretion pattern, including prostaglandin E2, indoleamine 2,3 dioxygenase, transforming growth factor beta, and interleukin-6, all augmented by interferon gamma secretion by lymphocytes. The transcriptome of three unactivated feline ASC lines were highly similar. Functional analysis of the most highly expressed genes highlighted processes including: 1) the regulation of apoptosis; 2) cell adhesion; 3) response to oxidative stress; and 4) regulation of cell differentiation. Finally, feline ASCs had a similar gene expression profile to noninduced human ASCs.

Conclusions

Findings suggest that feline ASCs modulate lymphocyte proliferation using soluble mediators that mirror the human ASC secretion pattern. Uninduced feline ASCs have similar gene expression profiles to uninduced human ASCs, as revealed by transcriptome analysis. These data will help inform clinical trials using cats with naturally occurring diseases as surrogate models for human clinical trials in the regenerative medicine arena.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0528-z) contains supplementary material, which is available to authorized users.

Human and animal dirofilariasis: the emergence of a zoonotic mosaic

Dirofilariasis represents a zoonotic mosaic, which includes two main filarial species (Dirofilaria immitis and D. repens) that have adapted to canine, feline, and human hosts with distinct biological and clinical implications. At the same time, both D. immitis and D. repens are themselves hosts to symbiotic bacteria of the genus Wolbachia, the study of which has resulted in a profound shift in the understanding of filarial biology, the mechanisms of the pathologies that they produce in their hosts, and issues related to dirofilariasis treatment. Moreover, because dirofilariasis is a vector-borne transmitted disease, their distribution and infection rates have undergone significant modifications influenced by global climate change. Despite advances in our knowledge of D. immitis and D. repens and the pathologies that they inflict on different hosts, there are still many unknown aspects of dirofilariasis. This review is focused on human and animal dirofilariasis, including the basic morphology, biology, protein composition, and metabolism of Dirofilaria species; the climate and human behavioral factors that influence distribution dynamics; the disease pathology; the host-parasite relationship; the mechanisms involved in parasite survival; the immune response and pathogenesis; and the clinical management of human and animal infections.

Adult Dirofilaria immitis excretory/secretory antigens upregulate the production of prostaglandin E2 and downregulate monocyte transmigration in an "in vitro" model of vascular endothelial cell cultures

Canine and feline cardiopulmonary dirofilariosis caused by Dirofilaria immitis is a chronic and potentially fatal disease. Adult worms live in the pulmonary arteries of infected immunocompetent hosts for years. The aim of the present study is the identification of the influence of the metabolic products (excretory/secretory antigens, DiE/S) of D. immitis on the vascular endothelial cells, because the vascular endothelium interplays in a direct manner with the parasite and their products. For this purpose, HAAE-1 vascular endothelial cells were treated with DiE/S, using non-treated cultures as negative controls. Significant increases in the COX-2, 5-LO expression and PGE(2) level were detected in the treated cells compared with the control cells. Moreover, DiE/S decreases monocyte transmigrations across vascular endothelial cell monolayers. Treatment with DiE/S does not have a cytotoxic effect and do not alter apoptosis, necrosis or cell cycle of vascular endothelial cells. These results suggest that the DiE/S stimulates the production of mediators and mechanisms that favor the survival of the parasite, in vascular endothelial cells, contributing to restrict vascular and lung damages in the infected host, without altering the basic physiologic processes of endothelial cells.

Identification of the lipid mediator prostaglandin E2 in tissue immune cells of humans infected with the filaria Onchocerca volvulus

Prostaglandins generated by multiple tissue and immune cells exhibit regulatory effects on the vascular and immune systems. Prostaglandin E(2) (PGE(2)), in particular, affects innate as well as adaptive immune mechanisms. We identified PGE(2) in host immune cells adjacent to Onchocerca volvulus in subcutaneous onchocercomas and the affected skin. Using immunohistology, PGE(2) was predominantly detected in infiltrating macrophages but also in plasma cells. Consecutive sections revealed concomitant presence of PGE(2) and transforming growth factor-beta (TGF-beta), representing a second immunoregulative mediator in macrophages and plasma cells. TGF-beta was preferentially observed in the infiltrating macrophages in patients with a generalized hyporeactive onchocerciasis and less in patients with the hyperreactive form. The presence of PGE(2) and TGF-beta in adjoining host cells infiltrating in the onchocercoma and dermis may indicate containment of inflammatory responses that could favour survival of the filarial parasite.

Dirofilaria immitis and Wolbachia-derived antigens: its effect on endothelial mammal cells

Antigens of both Dirofilaria immitis and Wolbachia symbiont bacteria are implicated in the inflammatory pathology of heartworm infection. The aim of the present study was to compare the stimulatory capacity of in vitro cultures of vascular endothelial cells by the adult somatic antigens of D. immitis (DiSA) and the recombinant form of the Wolbachia surface protein (rWSP), during the first 24h of stimulation. Our results indicate a different stimulatory activity of the two antigens. Both the DiSA and rWSP stimulate the production of the enzymes responsible of the arachidonic acid metabolism, cyclooxygenase-2, 5-lipoxygenase (5-LO), and leukotriene B4. Only DiSA stimulates the production of prostaglandin E2. Related to the adhesion molecules, the DiSA stimulates the expression of intercellular adhesion molecule-1 (ICAM-1) and platelet endothelial cell adhesion molecule-1 (PECAM-1), whereas rWSP stimulates ICAM-1, PECAM-1, and vascular cell adhesion molecule-1 (VCAM-1). Expression of E-cadherin and vascular endothelial growth factor also were stimulated by rWSP. Neither of the two antigens altered the basic physiological mechanisms of endothelial cells, such as cell proliferation, cell cycle, or apoptosis. The biological and pathological significance of these finding are discussed.

Vascular endothelial cell activation by adult Dirofilaria immitis antigens

Dirofilaria immitis is the causal agent of cardiopulmonary dirofilariosis (heartworm disease). Adult worms lodge in the pulmonary arteries and right ventricle, thus vascular endothelium is exposed to high concentrations of Dirofilaria antigenic products. Heartworm disease habitually develops as a chronic foreseeable pathology. Moreover, the simultaneous death of many adult worms, naturally or induced by a filaricide treatment, can cause acute thromboembolisms and endarteritis. To better understand the effects of the massive death of D. immitis adult worms on the blood vessel endothelium, we cultured vascular endothelial cells in the presence or absence of an antigenic extract of D. immitis adult worms (DiSA). The parasite products increased the expression of enzymes and the synthesis of eicosanoids related to inflammation, such as COX-2, 5-LO, PGE(2) and LTB(4). The expression of ICAM-1 and PECAM-1 adhesion molecules and endothelial and inducible Nitric Oxide Synthases (eNOS and iNOS) was also increased in cultures treated with DiSA. Nevertheless, DiSA decreased endothelial permeability and does not alter both proliferation and apoptosis. These results suggest that the somatic extract of D. immitis adult worms stimulate inflammatory mechanisms in endothelial cells, without altering their basic physiologic processes.