Retroviral-Mediated Gene Transfer and Expression of Human Lipoprotein Lipase in Somatic Cells

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Abstract
Lipoprotein lipase (LPL) is an enzyme responsible for the hydrolysis of triglyceride-rich circulating lipoproteins. Humans with complete defects in LPL activity present from infancy with failure to thrive, eruptive xanthomas, pancreatitis, and lactescent plasma. In addition, heterozygous carriers for this disorder may be at increased risk for the development of coronary artery disease. In view of a potential strategy for correcting complete or partial LPL deficiency, a 1.56-kb human LPL cDNA was inserted into a series of recombinant myeloproliferative sarcoma virus (MPSV)-based retroviral vectors under transcriptional control of the constitutive MPSV long terminal repeat (LTR). Stable gene transfer and enhanced expression of human LPL was observed at both the RNA and protein level in a variety of somatic cell types in vitro. Genetically modified cell populations included mouse NIH-3T3 fibroblasts and C2C12 myoblasts, primary human fibroblasts, and established human hematopoietic cell lines of erythroid (K562), myelocytic (HL60), and monocytic (U937,THP-1) type. The achieved levels of bioactive human LPL were found to vary widely between the different transduced cell lines, which may be critical to an approach to gene therapy. Transduced primary human fibroblasts yielded maximal elevation of LPL immunoreactive mass and activity of at least 24- and 50-fold, respectively, above constitutively expressed levels for this cell type. Human fibroblasts, therefore, appear to accommodate in vitro the complex processes readily leading to the maturation and secretion of bioactive human LPL and may serve as an effective cellular vehicle for LPL gene delivery and expression in human LPL deficiency. LPL deficiency is a serious autosomal recessive disorder causing severe hypertriglyceridemia. A series of MPSV-based vectors were constructed bearing a human LPL cDNA. Retroviral transduction by these vectors produced stable secretion of bioactive human LPL from a variety of recipient cell types. Skin cell fibroblasts yielded maximal retroviral-mediated production of bioactive human LPL in vitro and may be a suitable target for the in vivo delivery, expression, and secretion of LPL in complete or partial human LPL deficiency.

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