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Keywords

leukocyte infiltration, silicone, scleroderma, chickens, growing feather

Abstract

Intradermal injections of silicone-based fillers for the face and body may cause chronic inflammation and fibrotic reactions in some individuals. Chickens from the UCD 200/206 White Leghorn (WL) line spontaneously develop a fibrotic autoimmune disease known as scleroderma/systemic sclerosis (SSc). Using the SSc-prone UCD and healthy WL chickens, a longitudinal study was conducted to examine the cellular inflammatory responses to intradermal (i.d.) injections of sterile SILIKON-1000. Specifically, the pulp (a skin derivative) of growing feathers (GFs) was i.d. injected with sterile SILIKON-1000 or phosphate-buffered saline (PBS) as injection control (8 and 3 birds/line, respectively; 10 µL/GF; 20 GFs/bird). Two GFs were collected from each bird before (0 d) and at 0.25 (6 h), 1, 2, 3, and 7 d post-injection (p.i.) for leukocyte population analysis by flow cytometry. Pulp-injection of SILIKON-1000 resulted in similar, rapid (6 h) heterophil and macrophage increases (P ≤ 0.001) in GF-pulps in both lines, with greater macrophage levels (% pulp cells; P = 0.029) at 6 h p.i. in UCD-SSc than WL. In WL, SILIKON-1000 injection resulted in somewhat greater levels of pulp-infiltrating macrophages (P = 0.039) and CD4+ T cells (P = 0.024) than PBS injection; whereas in UCD-SSc chickens, γδ T cell levels were substantially greater (P = 0.008) post SILIKON-1000 than PBS injection. As γδ T cells were shown to play an important role in the fibrotic process by up-regulating collagen expression in SSc patients, the greater γδ T cell recruitment suggests that in UCD-SSc chickens, the direction of the SILIKON-1000 induced inflammatory response may be towards increased collagen production and fibrosis, rather than normal tissue restoration.

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