Abstract 16615: Reconstitution of CD4 T Cells Causes Cardiac Fibrosis and Myocardial Dysfunction in T Cell Specific S1P Receptor 1 Deficient Diabetic Mice

Abstract

Involvement of T cells in fibrosis has been reported but modulation of their role in context of diabetic fibrogenesis has yet to be determined. Our previous studies indicated that T cell S1P receptor 1 (S1P1) genetic depletion ensues sustained lymphopenia in circulation and reduced fibrosis in streptozotocin-induced type 1 murine diabetic model. We hypothesized that adoptive transfer of T cells to T-cell S1P1 receptor knock-out (TS1P1KO) mice would abolish cardioprotection and antifibrotic effect as observed earlier. TS1P1KO and littermate wild-type (WT) mice were divided into vehicle and streptozotocin (STZ) (50 mg/kg body weight for five days, i.p.) groups. Naïve CD4 T cells were isolated by positive selection through MS column from CD4 magnetic microbeads-labeled WT mice splenocytes. Isolated CD4 T cells (purity >95%) were adoptively transferred (i.v.) into the mice of above groups at dose of one million cells. Body weight (g) and blood glucose level (mg/dl) were monitored. CD4 and CD8 T cells in blood were counted by flow cytometry. Heart histology was studied in H&E stained sections and pathological grading was given. Masson Trichrome stained heart sections were digitally imaged at 16x magnification and percent of fibrotic area was quantified by using NIH ImageJ. Cardiac contractility was measured in ex-vivo Langendorff’s heart perfusion system at the end of 11 weeks. TS1P1KO mice had ~90% reduced T cells (CD4 cells: 1.15±0.30% vs 25.06±0.64%, CD8 cells: 2.09±0.42% vs 14.72±0.38% in WT, **P<0.01, n=4-5) in blood. KO diabetic mice without adoptive transfer of CD4 T cells exhibited about 70% less fibrotic area (11.86±4.34% vs 46.48±8.06% in WT STZ, *P<0.05, n=7-9) and improved cardiac structure and function. Adoptively CD4 T cells recipient KO diabetic mice presented cardiac structural disorganization (histological score: 9.25±0.95 vs. 1.29±0.52 in KO STZ without transfer, *P<0.05, n=4-7) and increased myocardial fibrosis (37.11±3.22% vs. 11.86±4.34% in KO STZ without transfer, *P<0.05, n=4-7) with reduced cardiac contractile force compared with KO diabetic mice without CD4 T cells transfer. In conclusion, reconstitution of CD4 T cells increases cardiac fibrosis and attenuates cardiac function in lymphopenic T cell S1P1 knock-out diabetic mice.