1. Cell Death Dr. Raid Jastania

2. Case

3. During your clinical year rotation, you work with the transplant team. You see this lady who had kidney transplant 3 months ago. She is 38 year old, with renal failure on dialysis for few years due to end stage renal disease due to SLE. She comes with poor renal function, and increasing levels of urea and creatinine. A kidney biopsy is done. The biopsy shows necrosis of the kidney.

4. What are the possible causes of this finding? Keep in mind –Patient has SLE (immune disease) –She is on immunosuppressive medicine (drugs and susceptible for infections) –She has recent surgery (techniqual issues, vascular anastomosis) –Transplant rejection

5. Possible causes of necrosis: –Infections: CMV, Herpes, Candida, Aspergillous, Histoplasma, Strep, Staph –Physical: surgery related complication eg. anastomosis leak –Chemical: immuno suppression medications –Ischemic: vascular stenosis, thrombosis –Immune: Rejection, recurrence of SLE

6. Necrosis Apoptosis

8. Targeted structures in cell injury: 1.Cell membrane 2.ATP generation in mitochondria 3.Protein and protein synthesis 4.Genetic material

9. Necrosis Necrosis is defined as: the morphological changes in cell death in living tissue, as a result of enzymatic digestion and denaturation of proteins. The process is accompanied by inflammatory response.

10. “the point of no return” Studies indicated 2 processes: 1.Inability to reverse mitochondrial dysfunction 2.Inability to reverse membrane damage.

11. How does membrane damage occur? 1.Through loss of phospholipid (by increased degradation or decreased production) 2.Damage in cytoskeleton proteins 3.Oxygen free radicals resulting in lipid peroxidation

13. Morphology: Reversible Injury (EM) 1.Membrane bleb 2.Mitochondrial swelling 3.Swelling of ER and detachment of the ribosomes 4.Nuclear changes: chromatin condensation

14. Morphology: Reversible Injury (LM) 1.Cell swelling: hydropic, vacuoles 2.Fatty change

17. Morphology: Irreversible Injury (LM) Nuclear changes 1.Karyolysis: pale nuclei 2.Pyknosis: nuclear shrinkage and basophilia 3.Karyorrhexis: fragmentation of pyknotic nuclei

19. Patterns of Necrosis: 1.Coagulative Necrosis: Morphology: preservation of the basic structure of the tissue. 2.Gangrenous Necrosis: “wet gangrene” 3.Liquefactive Necrosis: Morphology: digestion of all the cell component resulting in amorphous cellular debris. 4.Caseous Necrosis: with TB. Morphology: granuloma with central necrosis. 5.Fat Necrosis: in pancreatitis after the release of lipase from pancreatic acini.

21. Apoptosis

23. Apoptosis is a distinctive mode of cell death. It happens physiologically or pathologically during: 1.Organogenesis and involution of structures 2.Hormone-dependent involution eg. Endometrium, Breast 3.Deletion of autoreactive T-cells 4.Following mild injury eg. heat, radiation, drugs.

24. Morphology: Single cells or clusters of cells Eosinophilic cytoplasm, shrunken cells Chromatin condensation, and fragmentation Apoptotic bodies Phagocytosis No inflammation

26. Mechanism of Apoptosis: 1.Signalling: Tumor Necrosis Factor Receptor (TNFR) and FAS. 2.Control and Integration: by 2 different pathways: a.Direct transmission of death signal by adapter protein b.Regulation of mitochondrial permeability by BCL-2. The end result is release of cytochorm C which activates Apaf-1 and the rest of the apoptotic process

27. Mechanism of Apoptosis: 3.Execution phase by activation of catabolic enzymes resulting in a.Protein cleavage (by Caspases) b.Protein cross-linking (by transglutaminases) c.DNA fragmentation into 180-200 base-pair (resulting in laddering pattern) 4. Removal of apoptotic bodies by adjacent cells or phagocytosis (No inflammation)