Banff 2022 pancreas transplantation multidisciplinary report: Refinement of guidelines for T cell-mediated rejection, antibody-mediated rejection and islet pathology. Assessment of duodenal cuff biopsies and noninvasive diagnostic methods.

The Banff pancreas working schema for diagnosis and grading of rejection is widely used for treatment guidance and risk stratification in centers that perform pancreas allograft biopsies. Since the last update, various studies have provided additional insight regarding the application of the schema and enhanced our understanding of additional clinicopathologic entities. This update aims to clarify terminology and lesion description for T cell-mediated and antibody-mediated allograft rejections, in both active and chronic forms. In addition, morphologic and immunohistochemical tools are described to help distinguish rejection from nonrejection pathologies. For the first time, a clinicopathologic approach to islet pathology in the early and late posttransplant periods is discussed. This update also includes a discussion and recommendations on the utilization of endoscopic duodenal donor cuff biopsies as surrogates for pancreas biopsies in various clinical settings. Finally, an analysis and recommendations on the use of donor-derived cell-free DNA for monitoring pancreas graft recipients are provided. This multidisciplinary effort assesses the current role of pancreas allograft biopsies and offers practical guidelines that can be helpful to pancreas transplant practitioners as well as experienced pathologists and pathologists in training.

C4d-expressing glomerulopathy and proteinuria post transplantation of a too-big-for-size mismatched kidney allograft: An unusual case with good outcome
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A 5-year-old severely growth-retarded child with tubulointerstitial, oliguric end-stage renal disease received an adult-size kidney transplant. Three years post grafting under standard triple immunosuppression (mycophenolate mofetil, tacrolimus, and prednisone) de novo nephrotic range proteinuria without the nephrotic syndrome developed. Graft function was normal (serum creatinine: 0.2 - 0.3 mg/dL), there were no donor-specific HLA antibodies (DSA), and the urine sediment was inactive. Two biopsies collected 3 and 4 years post-transplantation showed severe glomerular capillary wall remodeling and associated pseudolinear C4d staining as morphologic correlates for the proteinuria. Changes resembled those seen in so-called "size-mismatch transplant glomerulopathies". There was no evidence of a glomerulonephritis, acute or chronic rejection including transplant glomerulopathy, interstitial fibrosis, peritubular capillary C4d deposits, or multilamination of peritubular capillary basement membranes. The glomerular changes were not detected in the implantation zero-hour biopsy or the recipient's native renal biopsy. At the end of follow-up 64 months post transplantation, proteinuria persisted at subnephrotic levels in the setting of stable graft function and undetectable DSAs. This unique case adds to the list of causes of nonrejection-associated post-transplant proteinuria. It demonstrates for the first time that a too-large-for-body-size mismatched graft is associated with a presumably sheer stress-induced C4d expressing glomerulopathy, severe proteinuria, and favorable outcome.
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Calmodulin-dependent protein kinase II activation promotes kidney mesangial expansion in streptozotocin-induced diabetic mice.

Calcium-calmodulin-dependent protein kinase II (CaMKII) is upregulated in diabetes mellitus (DM), leading to the overproduction of collagen in the myocardium. We hypothesized that CaMKII plays a role in the development of diabetic nephropathy (DN). Streptozotocin (STZ) injection into FVB wild-type mice led to mild mesangial matrix expansion, reproducing an essential feature of early human DN. Mesangial matrix measurements were performed on trichrome-stained paraffin sections using a trainable segmentation method based on WEKA (Waikato Environment for Knowledge Analysis) Image J-Fiji plugin (TWS plugin), and the electron micrographs of the whole glomeruli stitched from individual 4800x partial glomerular images. Both methods demonstrated that the statistically significant mesangial matrix expansion seen in the diabetic mice was prevented by chronic pretreatment with KN-93, a small molecule CaMKII inhibitor. This study indicates a role for CaMKII in the development of mesangial alterations in diabetes and suggests a possible new therapeutic target.

Extracellular signal-regulated kinase 1/2 activity is not required in mammalian cells during late G2 for timely entry into or exit from mitosis.

Extracellular signal-regulated kinase (ERK)1/2 activity is reported to be required in mammalian cells for timely entry into and exit from mitosis (i.e., the G2-mitosis [G2/M] and metaphase-anaphase [M/A] transitions). However, it is unclear whether this involvement reflects a direct requirement for ERK1/2 activity during these transitions or for activating gene transcription programs at earlier stages of the cell cycle. To examine these possibilities, we followed live cells in which ERK1/2 activity was inhibited through late G2 and mitosis. We find that acute inhibition of ERK1/2 during late G2 and through mitosis does not affect the timing of the G2/M or M/A transitions in normal or transformed human cells, nor does it impede spindle assembly, inactivate the p38 stress-activated checkpoint during late G2 or the spindle assembly checkpoint during mitosis. Using CENP-F as a marker for progress through G2, we also show that sustained inhibition of ERK1/2 transiently delays the cell cycle in early/mid-G2 via a p53-dependent mechanism. Together, our data reveal that ERK1/2 activity is required in early G2 for a timely entry into mitosis but that it does not directly regulate cell cycle progression from late G2 through mitosis in normal or transformed mammalian cells.