Excess collagen deposition occurs in pulmonary fibrosis. A new study suggests that collagen overproduction may originate from cells derived from bone marrow precursors rather than parenchymal lung fibroblasts .
Origin of fibroblastic foci. Fibroblastic foci, sites of active collagen synthesis, are the pathologic hallmark of pulmonary fibrosis. The traditional view is that cytokine secretion by epithelial and inflammatory cells induces parenchymal lung fibroblasts to overproduce collagen and to differentiate into myofibroblasts. Several recent studies indicate that bone marrow–derived cells can engraft into lung tissue and produce collagen. Bone marrow–derived cells may be recruited to the lung by chemokines generated by macrophages.