The pathogenesis of asthma likely involves chronic injury and repair processes, which can alter, or """"""""remodel"""""""", the basic structures of the airways. One of these structures is the subbasement membrane (SBM). Preliminary data suggest that the SBM is variably increased in truly severe refractory asthma, with the degree of thickening associated with: 1) type of inflammation (eosinophils present or not), 2) physiologic indices (FEV1 and airway collapse) and 3) clinical outcomes (near-fatal asthma). Additionally, increases in transforming growth factor(TGF)-beta in the airway (most noticeable in severe asthma) correlate with SBM thickness. The hypothesis for this proposal is that the balance of matrix active compounds, such as TGF betas, matrix metalloproteinases (MMP) and their inhibitors, tissue inhibitors of MMPs (TIMPs), modulates chronic tissue breakdown and repair, controlling the thickness of this SBM. Glucocorticoids (GC), commonly used asthma treatments, may further alter the balance and hence the """"""""remodeling"""""""". This proposal will determine the chronic balance of TGFbeta1,2,3, and MMPs/TIMPs in the airways of severe asthmatics, milder asthmatics and normal controls. This balance will be evaluated in relation to structure (collagen deposition at the SBM) and function (physiologic differences) (Specific Aim number 1). As we also hypothesize that GCs further inhibit the wound repair process, all studies will be done before and after high dose oral GCs. To put these abnormalities into the perspective of the """"""""normal"""""""" wound healing process, we will determine the wound repair process in the airways of mild asthmatics, atopic nonasthmatics and normal controls, again, evaluating TGF-betas, MMPs, TIMPs and collagen deposition. (Specific Aim number 2). This will be done by evaluating changes in these parameters after """"""""specific"""""""" wounding (allergen) and """"""""nonspecific"""""""" wounding (abrasion) over time. Similarly, these """"""""normal"""""""" repair processes will be evaluated after high dose/potency inhaled GCs. Finally, we will model some of these in vivo changes in an in vitro system, utilizing fibroblasts obtained from the airways of asthmatics of different severities and at different times in the repair process. We will determine fibroblast responses in proliferation, MMPs/TIMPs, collagen production and metabolism after stimulation with TGF-betas and/or GCs (Specific Aim number 3). These studies should greatly improve the understanding of the repair process in asthma, particularly in severe asthma, with the implication that modulation of the altered balance of tissue breakdown and deposition could lead to improvements in physiologic and clinical outcomes.
