Lymphangiogenesis is associated with chronic kidney disease (CKD) and occurs following kidney transplant. Here, we demonstrate that expanding lymphatic vessels (LVs) in kidneys and corresponding renal draining lymph nodes (RDLNs) play critical roles in promoting intrarenal inflammation and fibrosis following renal injury. Our studies show that lymphangiogenesis in the kidney and RDLN is driven by proliferation of preexisting lymphatic endothelium expressing the essential C-C chemokine ligand 21 (CCL21). New injury-induced LVs also express CCL21, stimulating recruitment of more CCR7+ dendritic cells (DCs) and lymphocytes into both RDLNs and spleen, resulting in a systemic lymphocyte expansion. Injury-induced intrarenal inflammation and fibrosis could be attenuated by blocking the recruitment of CCR7+ cells into RDLN and spleen or inhibiting lymphangiogenesis. Elucidating the role of lymphangiogenesis in promoting intrarenal inflammation and fibrosis provides a key insight that can facilitate the development of novel therapeutic strategies to prevent progression of CKD-associated fibrosis.

Background: Renal tubulointerstitial fibrosis is the final common stage of renal failure. CD4+ T lymphocyte recruitment and activation after injury could be the very important early event that mediates the onset of renal fibrogenesis. But the role of CD4+ T lymphocytes in renal fibrosis is controversial and its cellular mechanism needs to be further investigated. Methods: Biopsy specimens were from patients with minimal-change or IgA nephropathy. Mouse renal fibrosis was induced by unilateral ureteral obstruction (UUO). CD4+ T lymphocytes of wild BALB/c mice were depleted with anti-CD4 antibody. BALB/c Nu/Nu mice were reconstituted with polarized Th1 or Th2 cells by tail vein injection. Results: Our study demonstrated that massive CD4+ T lymphocytes infiltrated fibrotic kidneys of patients. The depletion of CD4+ T lymphocytes inhibited UUO-induced mouse renal fibrosis. In the process of UUO-induced renal fibrosis, the ratios of Th2/Th1 increased with time. Results have also shown that Th2-reconstituted mice developed renal fibrosis more easily than Th1-reconstituted mice, which manifested by interstitial expansion and collagen deposition, higher expression of α-SMA and vimentin and increased expression of fibronectin, TGF-β and collagen I. We also found that CD4+ T cells from Th1-reconstitued mice tended to secrete IL-4 and IL-13 Th2-like cytokines. Conclusion: In conclusion, our study demonstrated the importance of CD4+ T lymphocytes in renal fibrosis and gave the first direct evidence that Th2 cells play a pivotal role in UUO-induced renal fibrosis. Inhibition of CD4+ T lymphocyte differentiation to Th2 would be a potential therapeutic intervention to prevent renal fibrosis.

Background Since the Coronavirus Disease 2019 (COVID-19) outbreak, there is accumulating data on the clinical characteristics, treatment strategies and prognosis of COVID-19 in patients with concurrent renal disease. Postmortem investigations reveal renal involvement in COVID-19, and most recently, several biopsy researches reveal that acute tubular injury, as well as glomerular nephropathy such as collapsing glomerulopathy were common histological findings. However, to our best knowledge, there is limited data regarding IgA nephropathy in the setting of COVID-19. Case presentation In the present case, we report a 65-year old Chinese woman who presented with dark-colored urine, worsening proteinuria and decreased renal function after COVID-19 infection. She received a renal biopsy during COVID-19 infection. The renal biopsy revealed IgA nephropathy without any evidence for SARS-Cov-2. The findings suggest that the renal abnormalities were a consequence of exacerbation of this patient’s underlying glomerular disease after COVID-19 infection. After a regimen of 3-day course of glucocorticoid and angiotensin II receptor blocker therapy, the patient recovered and remained stable upon follow-up. Conclusions It is important to consider the underlying glomerular disease exacerbation as well as virus induced injury when dealing with renal abnormalities in patients with COVID-19. A kidney biopsy may be indicated to exclude a rapidly progressive glomerular disease.