Compounds, compositions and methods for improving the viability and/or function of cells or for the in vitro, ex vivo or in vivo protection of cells, tissue, graft or organs from various damages are described. The reagents and composition are based on activation of the heat shock response and/or the antioxidant response and include for example, HSP90 co-factor inhibitor such as Celastrol or Celastrol analogs used alone or in combination with an adjunct agent (e.g., a NRF-2 activator, antioxidant, etc.). Therapeutic enhancement may also include increase in paracrine effector production and signaling. Methods for improving the resistance of cells, tissue, grafts or organs to damages or stress, such as hypoxic or oxidative stress-induced cell death, and/or for improving the viability and retention of transplanted or transfused cells are also described. Therapeutic treatment or prevention of ischemic injury (e.g. myocardial infarct, ischemia/reperfusion injury) and related stressors (hypoxia, oxidative stress, inflammation, sepsis/shock, etc) are also provided.
