Idiopathic pulmonary fibrosis remains a relevant problem in the field of healthcare with an unfavorable prognosis for patients due to progressive fibrous remodeling of the pulmonary parenchyma. Starting with the reactions damaging the epithelial lining of alveoli, pulmonary fibrosis is implemented through a cascade of complex mechanisms, the crucial of which is the TGF-β/SMAD mediated pathway, involving various cell populations. Considering that a number of the available drugs (pirfenidone and Nintedanib) have only limited effectiveness in slowing the progression of fibrosis, the search and justification of application of other approaches aimed at regulating the immune response, cellular aging processes, programmed cell death and transdifferentiation of cell populations remains relevant. This literature review presents the key modern concepts concerning molecular genetics and cellular mechanisms of lung fibrosis development, based mainly on in vitro and in vivo studies in experimental models of bleomycin-induced pulmonary fibrosis, as well as the latest data on metabolic features, potential application points and effects of vitamin D and its metabolites.