We have analyzed molecular basis of CD36 deficiency and identified three mutations responsible for CD36 deficiency: 1) a ⁴⁷⁸C→T substitution in codon 90 (proline90→serine), 2) a dinucleotide deletion in colon 110, and 3) a single nucleotide insertion in codon 317. The ⁴⁷⁸C→T (proline90→serine) substitution seemed to be the most common mutation. We have demonstrated that the ⁴⁷⁸C→T substitution directly leads to CD36 deficiency via defects in posttranslational modification of the 81-kD precursor form of CD36. In addition to these three mutations, we have suggested that an allele having platelet-specific mRNA expression defects may be involved in type II CD36 deficient phenotype by the comparison between platelet and monocyte CD36 mRNA.

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Angiogenesis, the formation of new capillaries, facilitates pathological processes including tumor growth, metastases, proliferative diabetic retinopathy and pannus formation in rheumatoid arthritis. It has been described that the angiogenesis is occurred through the series of events include endothelial cell protease production, migration and proliferation, tubule formation, and basement membrane incorporation. Within the last two decades, with in vivo assay systems, various kinds of growth factors were identified as angiogenic factors that promotes endothelial cell proliferation and migration. While, in vitro model for angiogenseis indicated that extra cellular matrix (ECM) proteins stimulated endothelial cells to roganize into capillary-like tubular network and suggested that the ECM proteins are involved in the tubule formation process of antiogenesis. Recent papers reported the identification of the specific receptors on endothelial cells involved in the ECM-induced capillary tube formation. This article will focus on papers describing the in vitro analyses for tube formation of endothelial cells.

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For culturing hepatocytes, we generally use a matrix, collagen on which the cells proliferate and become confluent monolayer. Recently, a modified proteoglycan, chondroitin sulfatephosphatidylethanolamine (CS-PE), in stead of collagen, has been developed, and made possible a novel culture forming a multicellular assembling, spheroid. The spheroid is found to be highly differentiated, since it produces plasminogen and fibrinogen as well as albumin much more than the monolayer does, and it has an ability of being induced tyrosine aminotransferase by hormones. The mechanism with which hepatocytes form spheroid is unknown. Especially, it is not yet known how plasminogen activator (PA) plays in the spheroid or in the process of its formation. Our present study on the fibrinolytic factors revealed that the spheroid was in fairly hypofibrinolytic; t-PA activity in the conditioned media was one-tenth of that of monolayer (11U/10⁶ cells versus 116U/10⁶ cells), and the specific activity of t-PA was around one-fifth of monolayer. In addition, during the culture the mRNA for t-PA decreased in the spheroid, while it increased in monolayer. On the other hand, the mRNA for the PA inhibitor type 1 (PAI-1) was expressed higher in the spheroid. To form spheroid, addition of an anti-t-PA antibody to the media were not hampering although other protease inhibitors, including trypsin and plasmin inhibitors were of quite hampering and the cells remained monolayer. Thus, in the spheroid formation of hepatocytes, the cells would be in fibrinolytically inactive, however, they would require some proteolytic enzyme including plasmin.

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All-trans retinoic acid (ATRA) is an epoch-making agent for the treatment of acute promyelocytic leukemia (APL), because the mechanism of remission induction is due to induce the differentiation of APL cells, but not to kill the cells. Noticeably, it rapidly improves complicating disseminated intravascular coagulation (DIC). This implies that ATRA may specifically affect the expression of procoagulant activity of APL cells.
We studied the changes of tissue factor (TF) activity, TF mRNA, thrombomodulin (TM) antigen, TM cofactor activity and plasminogen activator (PA) activity in leukemic cells of an ATRA-treated APL patient accompanied by DIC.
TF activity of the APL cells decreased by half and the TM cofactor activity showed twofold increase within 2 days after the ATRA treatment, as compared with pretreatment cells. The abnormalities of plasma coagulation-fibrinolytic parameters began to improve in accordance with these changes, and DIC was subsided by day 5. TF mRNA which was detected by RT-PCR in pretreatment leukemic cells, was undetectable on 4 days after ATRA treatment. Morphological changes of APL cells examined by light microscopy were not apparent until day 8.
These results demonstrate that DIC improvement is due to the synergistic effects of decrease of TF and increase of TM in the APL cells induced by ATRA. These phenomena were observed in very early phase, and thus it is suggested that ATRA modulates directly the production of TF and TM in the leukemic cells, apart from the effect on cell differentiation.

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