Project Grant F30HL189253

IMMUNO-MECHANICAL EFFECTS OF AGING ON PULMONARY VERSUS SYSTEMIC FACTORS IN PNEUMONIA PROGRESSION - PROJECT SUMMARY / ABSTRACT PNEUMONIA IS A LEADING CAUSE OF HOSPITALIZATION AND DEATH IN OLDER ADULTS AND A MAJOR PRECIPITANT OF ACUTE LUNG INJURY AND ACUTE RESPIRATORY DISTRESS SYNDROME. OLDER PATIENTS EXHIBIT EXAGGERATED INFLAMMATION, IMPAIRED BACTERIAL CLEARANCE, AND DELAYED RECOVERY, YET MAJOR KNOWLEDGE GAPS REMAIN ABOUT WHETHER THESE VULNERABILITIES ARISE FROM AGING OF THE LUNG ITSELF (RESIDENT FACTORS) OR FROM AGING OF THE CIRCULATING IMMUNE ENVIRONMENT (SYSTEMIC FACTORS). THESE KNOWLEDGE GAPS PERSIST BECAUSE AGING AFFECTS BOTH RESIDENT AND SYSTEMIC COMPARTMENTS SIMULTANEOUSLY, MAKING IT CHALLENGING FOR CONVENTIONAL IN VIVO MODELS TO ISOLATE THEIR INDIVIDUAL CONTRIBUTIONS. MOREOVER, EXISTING TECHNOLOGIES ARE UNABLE TO RESOLVE DYNAMIC, CELLULAR-LEVEL HOST-PATHOGEN INTERACTIONS IN AN INTACT, FUNCTIONING LUNG. CLINICAL IMAGING LACKS THE REQUISITE SPATIAL-TEMPORAL RESOLUTION, WHILE HISTOLOGY ONLY PROVIDES STATIC SNAPSHOTS LACKING TEMPORAL RESOLUTION. TOGETHER, THESE LIMITATIONS PRECLUDE A MECHANISTIC UNDERSTANDING OF HOW AGING ACROSS RESIDENT VS SYSTEMIC FACTORS SHAPE PNEUMONIA SEVERITY. TO OVERCOME THESE LIMITATIONS, WE WILL COMBINE TWO COMPLEMENTARY PLATFORMS DEVELOPED IN OUR LAB: THE TRANSPARENT CRYSTAL RIBCAGE AND PARACORPOREAL CROSS-CIRCULATION. THE CRYSTAL RIBCAGE (NATURE METHODS 2023) HOUSES AN INTACT, VENTILATED, AND PERFUSED EX VIVO MOUSE LUNG UNDER NEAR-PHYSIOLOGIC CONDITIONS AND ENABLES CELLULAR-RESOLUTION OPTICAL IMAGING OF IMMUNE RECRUITMENT, VASCULAR INTEGRITY, AND TISSUE MICROMECHANICS. PARACORPOREAL CROSS-CIRCULATION CONTINUOUSLY ROUTES BLOOD FROM A FREELY-BEHAVING DONOR MOUSE TO THE CIRCULATION OF A RECIPIENT LUNG, HOUSED IN THE CRYSTAL RIBCAGE, ENABLING LONG-TERM, CONTROLLED EXCHANGE OF CIRCULATING CELLS AND SOLUBLE FACTORS. THIS APPROACH ALLOWS AGE-MISMATCHED PAIRINGS, E.G., AN AGED DONOR SUPPLYING BLOOD TO A YOUNG RECIPIENT LUNG HOUSED IN THE CRYSTAL RIBCAGE, OR VICE VERSA, UNIQUELY ENABLING UNCOUPLING OF RESIDENT VERSUS SYSTEMIC AGING EFFECTS. OUR CENTRAL HYPOTHESIS IS THAT AGING INDEPENDENTLY IMPAIRS PULMONARY DEFENSE THROUGH MECHANISTICALLY DISTINCT RESIDENT AND SYSTEMIC PATHWAYS. SPECIFICALLY, WE WILL INFECT AGED VS YOUNG MOUSE LUNGS WITH STREPTOCOCCUS PNEUMONIAE AND PERFUSE THEM WITH WHOLE BLOOD FROM AGED VS YOUNG DONORS. IN AIM 1, WE WILL DETERMINE HOW LUNG-INTRINSIC AGING ALTERS ALVEOLAR-CAPILLARY MICROMECHANICS AND RESIDENT IMMUNE RESPONSES BY PERFUSING AGED VS YOUNG EX VIVO LUNGS IN THE CRYSTAL RIBCAGE WITH BLOOD FROM YOUNG DONOR MICE. IN AIM 2, WE WILL EVALUATE HOW SYSTEMIC AGING IMPAIRS LEUKOCYTE RECRUITMENT BY PERFUSING YOUNG EX VIVO LUNGS WITH BLOOD FROM AGED VS YOUNG DONORS. THESE STUDIES WILL DEFINE HOW COMPARTMENT-SPECIFIC AGING DISTINCTLY DETERMINES PNEUMONIA SEVERITY AND ESTABLISH MECHANISTIC TARGETS FOR RESTORING IMMUNE-MECHANICAL HOMEOSTASIS. IN ADDITION TO DEFINING COMPARTMENT-SPECIFIC EFFECTS OF AGING ON PNEUMONIA PROGRESSION, THIS PROPOSAL WILL TRAIN ME IN PULMONARY MECHANOBIOLOGY AND IMMUNOLOGY AND PREPARE ME FOR A CAREER AS AN INDEPENDENT PHYSICIAN-SCIENTIST.