Lena Thiman

Fibroblast phenotypes and their activity are changed in the wound healing process after lung transplantation.

BACKGROUND Lung transplantation (LTx) is established as a life-saving treatment in end-stage lung disease. However, long-term survival is hampered by the development of chronic rejection, almost synonymous with bronchiolitis obliterans syndrome (BOS). The rejection is characterized by deposition of extracellular matrix in small airways. Fibroblasts/myofibroblasts are the main producers of extracellular matrix molecules such as proteoglycans. This study compared fibroblast phenotype and activity in the wound healing process at different points after LTx in patients who later did, or did not, develop BOS. METHODS Distally derived fibroblasts from patients 6 and 12 months after LTx and from healthy controls were analyzed for production of the proteoglycans versican, perlecan, biglycan, and decorin, with and without transforming growth factor (TGF)-β(1). Fibroblast migration and proliferation were also studied. RESULTS At 6 and 12 months after LTx, versican production was higher in fibroblasts from LTx patients (p < 0.01 p < 0.01) than from controls. Fibroblasts from patients who later developed BOS were more responsive to TGF-β(1)-induced synthesis of versican and biglycan than patients without signs of rejection (p < 0.05). Production of perlecan and decorin was negatively correlated with fibroblast proliferation in fibroblasts at 6 months after LTx. In a more detailed case study of 2 patients, one with and one without BOS, the altered proteoglycan profile was associated with impaired lung function. CONCLUSIONS LTx changes the phenotype of fibroblasts to a non-proliferative but extracellular matrix-producing cell due to wound healing involving TGF-β(1). If not controlled, this may lead to development of BOS.

Defective alterations in the collagen network to prostacyclin in COPD lung fibroblasts

BackgroundProstacyclin analogs are potent vasodilators and possess anti-inflammatory properties. However, the effect of prostacyclin on extracellular matrix (ECM) in COPD is not well known. Collagen fibrils and proteoglycans are essential ECM components in the lung and fibroblasts are key players in regulating the homeostasis of ECM proteins. The aim was to study the synthesis of prostacyclin and its effect on fibroblast activity and ECM production, and in particular collagen I and the collagen-associated proteoglycans biglycan and decorin.MethodsParenchymal lung fibroblasts were isolated from lungs from COPD patients (GOLD stage IV) and from lungs and transbronchial biopsies from control subjects. The prostacyclin analog iloprost was used to study the effect of prostacyclin on ECM protein synthesis, migration, proliferation and contractile capacity of fibroblasts.ResultsTGF-β1 stimulation significantly increased prostacyclin synthesis in fibroblasts from COPD patients (p < 0.01), but showed no effect on fibroblasts from control subjects. Collagen I synthesis was decreased by iloprost in both control and COPD fibroblasts (p < 0.05). Conversely, iloprost significantly altered biglycan and decorin synthesis in control fibroblasts, but iloprost displayed no effect on these proteoglycans in COPD fibroblasts. Proliferation rate was reduced (p < 0.05) and contractile capacity was increased in COPD fibroblasts (p < 0.05) compared to control fibroblasts. Iloprost decreased proliferative rate in control fibroblasts (p < 0.05), whereas iloprost attenuated contraction capacity in both COPD (p < 0.01) and control fibroblasts (p < 0.05).ConclusionsIloprost reduced collagen I synthesis and fibroblast contractility but did not affect the collagen-associated proteoglycans or proliferation rate in fibroblasts from COPD patients. Enhanced prostacyclin production could lead to improper collagen network fibrillogenesis and a more emphysematous lung structure in severe COPD patients.

5-HT2B receptor antagonists attenuate myofibroblast differentiation and subsequent fibrotic responses in vitro and in vivo

Pulmonary fibrosis is characterized by excessive accumulation of connective tissue, along with activated extracellular matrix (ECM)‐producing cells, myofibroblasts. The pathological mechanisms are not well known, however serotonin (5‐HT) and 5‐HT class 2 (5‐HT2) receptors have been associated with fibrosis. The aim of the present study was to investigate the role of 5‐HT2B receptors in fibrosis, using small molecular 5‐HT2B receptor antagonists EXT5 and EXT9, with slightly different receptor affinity. Myofibroblast differentiation [production of alpha‐smooth muscle actin (α‐SMA)] and ECM synthesis were quantified in vitro, and the effects of the receptor antagonists were evaluated. Pulmonary fibrosis was also modeled in mice by subcutaneous bleomycin administrations (under light isoflurane anesthesia), and the effects of receptor antagonists on tissue density, collagen‐producing cells, myofibroblasts and decorin expression were investigated. In addition, cytokine expression was analyzed in serum. Lung fibroblasts displayed an increased α‐SMA (P < 0.05) and total proteoglycan production (P < 0.01) when cultured with TGF‐β1 together with 5‐HT, which were significantly reduced with both receptor antagonists. Following treatment with EXT5 or EXT9, tissue density, expression of decorin, number of collagen‐producing cells, and myofibroblasts were significantly decreased in vivo compared to bleomycin‐treated mice. Receptor antagonization also significantly reduced systemic levels of TNF‐α and IL‐1β, indicating a role in systemic inflammation. In conclusion, 5‐HT2B receptor antagonists have potential to prevent myofibroblast differentiation, in vitro and in vivo, with subsequent effect on matrix deposition. The attenuating effects of 5‐HT2B receptor antagonists on fibrotic tissue remodeling suggest these receptors as novel targets for the treatment of pulmonary fibrosis.

VEGF synthesis is induced by prostacyclin and TGF-β in distal lung fibroblasts from COPD patients and control subjects: Implications for pulmonary vascular remodelling

Involvement of pulmonary vascular remodelling is a characteristic sign in COPD. Vascular mediators such as vascular endothelial growth factor (VEGF) and prostacyclin may regulate fibroblast activity. The objective was to study the synthesis of VEGF and interactions with prostacyclin and transforming growth factor (TGF)‐β1 in lung fibroblasts from patients with COPD and healthy control subjects. To further explore the autocrine role of synthesized VEGF on fibroblast activity, studies were performed in human lung fibroblasts (HFL‐1).

Sequence elements essential for the rapid turnover of Crithidia fasciculata ornithine decarboxylase

Summary.Ornithine decarboxylase (ODC) has a very fast turnover in mammalian cells, but is a stable enzyme in T. brucei and other trypanosmatid parasites like Leishmania donovani. However, Crithidia fasciculata, which is a phylogenetically closely related trypanosomatid to L. donovani, has an ODC with a rapid turnover. Interestingly, C. fasciculata ODC, but not L. donovani ODC, is rapidly degraded also in mammalian systems. In order to obtain information on what sequences are important for the rapid degradation of C. fasciculata ODC, we produced a variety of C. fasciculata/L. donovani ODC hybrid proteins and characterized their turnover using two different mammalian expression systems. The results obtained indicate that C. fasciculata ODC contains several sequence elements essential for the rapid turnover of the protein and that these regions are mainly located in the central part of the enzyme.