View Abstract

A2357 - Differential Regulation of Fibrocyte Accumulation by Discrete Components of the SSc-ILD Matrisome
Author Block: J. Winkler1, M. Minasyan1, H. Pan2, O. Desai1, X. Peng2, J. Meng3, E. Herzog4, H. Sun5; 1Pulmonary, Critical Care and Sleep Medicine, Yale University, New Haven, CT, United States, 2Yale University, New Haven, CT, United States, 3Xiangya Hospital Central South University, Changsha, China, 4Pulmonary Medicine, Yale University School of Medicine, New Haven, CT, United States, 5Pulmonary Medicine, Yale University, New Haven, CT, United States.
Rationale:
Scleroderma is an idiopathic autoimmune disease charactered by dermal fibrosis and, often, the development of interstitial lung disease (SSc-ILD). Fibrocytes are a population of collagen producing leukocytes that accumulate in the blood and lungs of patients with SSc-ILD via unknown mechanisms. Our prior work showed that fibrocytes accumulate in an ex vivo mimetic of the SSc-ILD lung generated by the decellularization of explanted human lungs. However, the biochemical factors accounting for this observation remain unclear. Because proteomics reveals an anomalous matrisome of the SSc-ILD lung, we sought to determine how this composition affects fibrocytes in SSc-ILD.
Materials and methods:
Peripheral blood mononuclear cells (PBMCs) obtained from subjects with SSc-ILD or demographically matched controls were treated with ECM solution derived from decellularized control and SSc-ILD lungs (CLS and SLS) at increasing concentrations. Cells were also stimulated with escalating doses of proteins that were most significantly increased (Microfibril-Associated Glycoprotein 4 (MFAP4), Periostin and Dermatopontin) levels in the SSc-ILD lung. PBMCs were cultured for up to 14 days and fibrocyte-like cells, were quantified.
Results:
Stimulation with 1 μg/ml SLS augments fibrocyte outgrowth relative to both control and SSc-ILD unstimulated PBMCs. Interestingly, at doses exceeding 2 μg/ml, both CLS and SLS appeared to suppress fibrocyte detection in a dose dependent fashion with the most intense suppression seen at 10 ug/ml. This effect on fibrocyte development was phenocopied in control and SSc-ILD PBMCs treated with MFAP4 and Dermatopontin. Treatment with Periostin at all doses permitted fibrocyte outgrowth, and treatment with 10 μg/ml of this protein increased fibrocyte detection suggesting that Periostin is a positive regulator of fibrocyte accumulation. This prediction was confirmed by studies in which control and SSc-ILD PBMCs seeded into CLS and SLS were subject to additional stimulation with 10ug/ml Periostin. Periostin treatment was sufficient to increase fibrocytes in the CLS while the higher increase was observed in the PBMCs in the SSc-ILD
ECM. No differences were observed between PBMCs from control or SSc, suggesting that the presence of periostin in the local milieu might account for the appearance in fibrocytes in this setting.
Conclusion:
Exposure to Periostin is sufficient to induce the accumulation of fibrocytes in experimental contexts and this effect might be opposed by with Dermatopontin or MFAP4. Further investigation of these findings could allow better understanding behind the mechanisms of regulation regarding the role of the matrisome in regulating fibrocytes and innate immune cell activation in the SSc-ILD lung.