Masahiro Mohri

Tumor necrosis factor-alpha is expressed by monocytes/macrophages following cardiac microembolization and is antagonized by cyclosporine.

Abstract The time course of expression of TNF-α in myocardial wound healing following ischemic injury was investigated in the porcine heart. Microembolization was used to induce focal ischemia and necrosis in hearts of 39 adult pigs. The animals were sacrified after 3, 6, 12, 24 h, 3 and 7 days, and after 4 weeks, and the myocardial tissue was studied by immunofluorescence using specific antibodies. TNF-α containing cells were identified as monocytes/macrophages by double staining with a muramidase antibody. Monocytes/macrophages were the only source of TNF-α. Microembolization caused multiple necrotic foci with loss of myocytes in the left ventricular myocardium. These foci contained numerous monocytes/macrophages and showed an inflammatory reaction typical of wound healing followed by replacement with scar tissue. The number of TNF-α positive cells increased after 24 h, peaked between 3–7 days and slowly decreased thereafter. Expression of TNF-α in monocytes/macrophages was significantly reduced after pretreatment of pigs with cyclosporine or dexamethasone. It is concluded that 1.) in myocardial tissue monocytes/macrophages are the only cell type expressing TNF-α, 2.) TNF-α is involved in wound healing after ischemia, and 3.) synthesis of TNF-α and inflammatory angiogenesis can be inhibited be treatment with either cyclosporine or dexamethasone.

Insulin-like growth factor I is involved in inflammation linked angiogenic processes after microembolisation in porcine heart

OBJECTIVEnAngiogenesis in the porcine heart can be induced by myocardial ischaemia following vascular occlusions. This process is characterised by increased numbers of monocytes/macrophages, known to be potent producers of various mitogens such as insulin-like growth factors (IGF) and interleukins (IL). The aim of the study was to examine gene expression of these factors by means of northern blot hybridisation, slot blot analysis, and in situ hybridisation in a porcine model of coronary angiogenesis.nnnMETHODSnExperimental ischaemia and subsequent focal necroses were induced by selective injection of 25 microns microspheres into the left circumflex artery. The hearts were excised after 3-168 h of microembolisation, and tissue was collected from a non-ischaemic control area and the circumflex region of the same heart for further analysis.nnnRESULTSnIGF-I was constitutively transcribed in normal porcine myocardium mainly by myocytes. Following microembolisation, IGF-I mRNA expression was significantly increased in the experimental region (1.8-fold) after 72 h and to a lesser extent after 168 h. In the ischaemic region, characterised by capillary sprouting, numerous mononuclear cells contained IGF-I mRNA. In contrast, IGF-II mRNA levels, constitutively produced by porcine myocytes, were not altered by microembolisation. IL-1 alpha, IL-1 beta, and IL-4 mRNA expression was undetectable in our animal model, whereas IL-6 was constitutively transcribed in normal and ischaemic heart and remained insensitive to microembolisation and focal necrosis.nnnCONCLUSIONnAfter microembolisation, increased IGF-I mRNA expression occurred by infiltrating monocytes in areas of microsphere induced focal necrosis, where capillary sprouting can be detected, suggesting that IGF-I is involved in inflammation linked angiogenic processes.

Coordinate expression of the insulin-like growth factor system after microembolisation in porcine heart

OBJECTIVESnCoronary microembolisation in the pig heart induces angiogenesis in a model of sterile inflammation due to focal necrosis. We have recently shown in this model that insulin-like growth factor I (IGF-I) is involved in inflammation-linked angiogenic processes due to its enhanced transcription after 72 h of ischaemia by infiltrating monocytes in areas of microsphere-induced focal necrosis where capillary sprouting could be detected. To obtain further insights into this process we studied by means of Northern blot analysis and in situ hybridisation the gene expression of other members of the IGF family, i.e. the six IGF binding proteins (IGFBPs), the insulin receptor, and the type I IGF receptor.nnnMETHODSnMyocardial injury was induced by injection of 25 microns non-radioactive microspheres into the left circumflex artery (LCx) in pigs that were killed after 3-24, 72, or 168 h of microembolisation. Tissue was collected from a non-ischaemic control area and the LCx region of the same heart for further analysis.nnnRESULTSnWe found decreased IGFBP-5 (2.7-fold; P < 0.02) mRNA concentrations after 72 h of microembolisation in ischaemic tissue versus control tissue from the same heart, preceded by a 1.9-fold elevated level of IGFBP-3 mRNA at 3-24 h (P < 0.05). IGFBP-6 was increased in ischaemic tissue at all time points studied. In situ hybridisation identified myocytes as the main producers of IGFBP-3 and IGFBP-6 mRNA. The mRNA levels of IGFBP-2, IGFBP-4, the insulin receptor, and the type I IGF receptor were constitutively expressed but did not change after microembolisation. Neither in heart nor in other organs studied transcripts of IGFBP-1 could be detected. Furthermore, we demonstrated that mRNA of the other components of the IGF system was expressed in almost all porcine organs except liver.nnnCONCLUSIONnThese results indicate a coordinate gene expression of the IGF system in microembolised porcine myocardium, compatible with a role of IGF-I, IGFBP-3, IGFBP-5, and IGFBP-6 in inflammation-linked angiogenesis and/or repair processes.