Nanoparticle-based thymulin gene therapy therapeutically reverses key pathology of experimental allergic asthma.

Despite long-standing efforts to enhance care for chronic asthma, symptomatic treatments remain the only option to manage this highly prevalent and debilitating disease. We demonstrate that key pathology of allergic asthma can be almost completely resolved in a therapeutic manner by inhaled gene therapy. After the disease was fully and stably established, we treated mice intratracheally with a single dose of thymulin-expressing plasmids delivered via nanoparticles engineered to have a unique ability to penetrate the airway mucus barrier. Twenty days after the treatment, we found that all key pathologic features found in the asthmatic lung, including chronic inflammation, pulmonary fibrosis, and mechanical dysregulation, were normalized. We conducted tissue- and cell-based analyses to confirm that the therapeutic intervention was mediated comprehensively by anti-inflammatory and antifibrotic effects of the therapy. We believe that our findings open a new avenue for clinical development of therapeutically effective gene therapy for chronic asthma.

A new adenovector system for implementing thymulin gene therapy for inflammatory disorders.

Thymulin is a thymic peptide possessing anti-inflammatory effects. In order to manipulate thymulin expression in gene therapy studies, we built a bidirectional regulatable two-vector Tet-Off system and the corresponding control system. The experimental two-vector system, ETV, consists of a recombinant adenovector (RAd) harboring an expression cassette centered on a Tet-Off bidirectional promoter flanked by a synthetic gene for thymulin and the gene for humanized Green Fluorescent Protein (hGFP). The second adenovector of this system, RAd-tTA, constitutively expresses the regulatory protein tTA. When cells are co-transduced by the two adenovector components, tTA activates the bidirectional promoter and both transgenes are expressed. In the presence of the antibiotic doxycycline (DOX) transgene expression is deactivated. The control two-vector system, termed CTV, is similar to ETV but only expresses hGFP. In CHO-K1, BHK, and C2C12 cells, ETV and CTV induced a dose-dependent hGFP expression. In CHO-K1 cells, transgene expression was almost completely inhibited by DOX (1mg/ml). After intracerebroventricular injection of ETV in rats, thymulin levels increased significantly in the cerebrospinal fluid and there was high hGFP expression in the ependymal cell layer. When injected intramuscularly the ETV system induced a progressive increase in serum thymulin levels, which were inhibited when DOX was added to the drinking water. We conclude that our regulatable two-adenovector system is an effective molecular tool for implementing short and long-term anti-inflammatory thymulin gene therapy in animal models of acute or chronic inflammation.

[THYMIC HORMONES, ANTIOXIDANT ENZYMES AND NEUROGENESIS OF BULBUS OLFACTORIUS IN RATS WITH PARKINSONISM: THE EFFECT OF MELATONIN].

The adult rats received both neurotoxin 6-hidroxidophamine and neurotoxin and melatonin. It was investigated a link between the disturbances of the brain antioxidant enzymes activity and thymic endocrine function, as possible pathogenic factors of parkinsonism, with changes in the number of neural stem cells (NSC) in the bulbus olfactorius. Rats with motor asymmetry in the apomorphine test and significant damage of the dopaminergic neurons in the-substantia nigra have decreased levels of superoxide dismutase, catalase and glutathione peroxidase activities in striatum (1.3-1.4 times) and blood thymulin content (8 times) compared to control group. On the contrary, examined indices were not changed in rats without motor asymmetry and correspondingly partly damaged neurons. The number of nestin(+)-cells in the bulbus olfactorius of rats without motor asymmetry increased from 91.2% to 99.3% and remained unchanged after melatonin administration course (10 mg/kg during 18 days). Melatonin administration resulted in the decrease in the number of nestin(+)-cells along with significant elevation of the decreased antioxidant enzymes activity and blood thymulin content in rats with circulatory movements. Possibilities of the enhancement of NSC differentiation in bulbus olfactorius into neuronal direction in such animals has been discussed. The conclusion about the potential use of melatonin as a neuroprotector in parkinsonism therapy has been made.

DNA nanoparticle-mediated thymulin gene therapy prevents airway remodeling in experimental allergic asthma.

Thymulin has been shown to present anti-inflammatory and anti-fibrotic properties in experimental lung diseases. We hypothesized that a biologically active thymulin analog gene, methionine serum thymus factor, delivered by highly compacted DNA nanoparticles may prevent lung inflammation and remodeling in a mouse model of allergic asthma. The DNA nanoparticles are composed of a single molecule of plasmid DNA compacted with block copolymers of poly-L-lysine and polyethylene glycol (CK30PEG), which have been found safe in a human phase I/II clinical trial. Thymulin plasmids were detected in the lungs of ovalbumin-challenged asthmatic mice up to 27days after administration of DNA nanoparticles carrying thymulin plasmids. A single dose of DNA nanoparticles carrying thymulin plasmids prevented lung inflammation, collagen deposition and smooth muscle hypertrophy in the lungs of a murine model of ovalbumin-challenged allergic asthma, leading to improved lung mechanics. In the present model of chronic allergic asthma, highly compacted DNA nanoparticles using thymulin analog gene modulated the inflammatory and remodeling processes improving lung mechanics.

The thymulin-lactotropic axis in rodents: thymectomy, immunoneutralization and gene transfer studies.

OBJECTIVES: There is clear evidence on the existence of a thymus-pituitary axis which seems to be particularly important during perinatal life. In particular, the thymic peptide thymulin has been shown to be a relevant player in thymus-pituitary communication. Our goal was to explore the effect of thymulin on circulating prolactin (PRL) levels in different animal models. To this end we undertook a series of experiments in rats and mice, implementing adult thymectomy, thymulin immunoneutralization in normal C57BL/6 mice and neonatal thymulin gene therapy in nude mice. METHODS: We assessed the impact of the above manipulations on PRL secretion and lactotrope morphology by measuring serum PRL by radioimmunoassay and by performing morphometric analysis of the lactotropic cell population in the anterior pituitary gland. RESULTS: Adult thymectomy in female rats slightly increased serum PRL, an effect that was partially reversed by thymulin gene therapy. In mice, thymulin immunoneutralization from birth to age 32 days reduced serum PRL both in males and females. Thymulin immunoneutralization induced a significant (p < 0.01) decrease in lactotrope cell density (CD) and volume density (VD) without changes in cell size (CS). Neonatal thymulin gene therapy markedly increased serum thymulin (p < 0.01) and lactotrope CD, CS and VD in nude mice of both sexes. CONCLUSIONS: Our findings suggest a modulatory effect of thymulin on the lactotrope cell population and on serum PRL, particularly during early life.

Role of thymulin on the somatotropic axis in vivo.

AIMS: There is clear evidence for the existence of a bi-directional thymus-somatotropic axis and several studies suggest that the thymic peptide thymulin may be involved in this communication. We undertook to assess the impact of serum thymulin immunoneutralization in C57BL/6 mice and that of neonatal thymulin gene therapy (NTGT) in nude mice on body weight (BW) gain and on the histomorphometric profile of the somatotrope population. MAIN METHODS: Immunoneutralization of thymulin was done from postnatal day 1 to 35 by i.p. injections of rabbit anti-thymulin serum (α-FTS) and normal rabbit serum (NRS) in controls. NTGT was implemented in nudes using an adenoviral vector expressing a synthetic gene for thymulin (RAd-FTS). On postnatal day 1, heterozygous (nu/+) and homozygous (nu/nu) pups received a single bilateral i.m. injection either RAd-FTS or RAd-GFP (a control vector expressing green fluorescent protein). BW gain was recorded and at the end of the study the pituitaries were immunostained for growth hormone (GH). Serum GH and thymulin were determined by radioimmunoassay and bioassay, respectively. KEY FINDINGS: Thymulin immunoneutralization induced a significant decrease in BW gain, serum GH and somatotrope cell density as well as an increase in somatotrope cell size. NTGT markedly increased BW gain, serum thymulin (P<0.01) and somatotrope cell and volume density in nu/nu mice. SIGNIFICANCE: Our results suggest that thymulin plays a relevant physiological role on the thymus-somatotropic axis in mice.

Neonatal thymulin gene therapy prevents ovarian dysgenesis and attenuates reproductive derangements in nude female mice.

Congenitally athymic (nude) female mice show severe ovarian dysgenesis after puberty, which seems to be consequential to a number of neuroendocrine derangements described in these mutants. Thus, considerable evidence suggests that thymulin, a thymic peptide, may be involved in thymus-pituitary communication. In order to clarify the relevance of thymulin for the maturation of the female reproductive system, we assessed at hypothalamic, pituitary, ovarian, and uterine level the preventive action of neonatal thymulin gene therapy (NTGT) on the changes that typically occur after puberty in congenitally athymic female mice. We injected (im) an adenoviral vector harboring a synthetic DNA sequence encoding a biologically active analog of thymulin, methionine-serum thymic factor, in newborn nude mice (which are thymulin deficient) and killed the animals at 70-71 d of age. NTGT in the athymic mice restored the serum thymulin levels. Morphometric analysis revealed that athymic nudes have reduced numbers of brain GnRH neurons and pituitary gonadotropic cells as compared with heterozygous controls. NTGT prevented these changes and also rescued the premature ovarian failure phenotype typically observed in athymic nude mice (marked reduction in the number of antral follicles and corpora lutea, increase in atretic follicles). Serum estrogen, but not progesterone, levels were low in athymic nudes, a reduction that was partially prevented by NTGT. Little to no morphological changes were observed in the endometrium of female nudes. The delay in the age of vaginal opening that occurs in athymic nudes was significantly prevented by NTGT. Our results suggest that thymulin plays a relevant physiologic role in the thymus-hypothalamo-pituitary-gonadal axis.

Thymulin-based gene therapy and pituitary function in animal models of aging.

Thymulin is a thymic hormone exclusively produced by the thymic epithelial cells. After its discovery and initial characterization in the 1970s, it was demonstrated that thymulin production and secretion is strongly influenced by the neuroendocrine system. Conversely, a growing core of information, to be reviewed here, points to thymulin as a hypophysiotropic peptide. Additionally, thymulin was shown to possess anti-inflammatory and analgesic properties in the brain. In recent years, a synthetic DNA sequence coding for a biologically active analog of thymulin, metFTS, was constructed and cloned in different adenoviral vectors. These include bidirectional regulatable Tet-Off vector systems that simultaneously express metFTS and green fluorescent protein and that can be downregulated reversibly by the addition of the antibiotic doxycycline. A number of recent studies suggest that thymulin gene therapy may be a suitable therapeutic strategy to prevent some of the endocrine and reproductive alterations that typically appear in congenitally athymic (nude) mice, taken as a suitable model of neuroendocrine and reproductive aging. The present article briefly reviews the literature on the physiology of the thymulin-pituitary axis as well as on the new molecular tools available to exploit the therapeutic potential of thymulin.

Neonatal thymulin gene therapy in nude mice: Effects on the morphology of the pituitary corticotrope population.

The integrity of the thymus during early life is necessary for a proper maturation of the neuroendocrine system, including the adrenal axis. The thymic metallopeptide thymulin seems to be a central physiologic mediator of thymus-pituitary communication. Furthermore, neonatal thymulin gene therapy has been shown to prevent the typical alterations of gonadotrophic cell number and morphology and serum gonadotropin levels in nude female mice. In the present study we assessed the impact of athymia and the effect of neonatal thymulin gene therapy on the corticotropic cell population in nude mice. The effect of thymulin administration to adult nudes on their hypothalamic content of corticotropin-releasing hormone (CRH) and the adrenal content of corticosterone was also determined. We used an adenoviral vector expressing a synthetic gene for the thymic peptide thymulin (metFTS) termed RAd-FTS. On postnatal day 1 or 2, heterozygous (nu/+) and homozygous (nu/nu) pups of both sexes received a single bilateral i.m. injection of RAd-FTS or RAd-GFP, a control vector. On postnatal day 71, mice were bled and sacrificed, and their pituitaries were immediately dissected, fixed and immunostained for corticotropin. Morphometry was performed by means of an image-analysis system. The following parameters were calculated: volume density (VD: Σ cell area/reference area), cell density (CD: number of cells/reference area), and cell surface (CS: expressed in µm²). Serum thymulin levels were measured by a bioassay, and CRH as well as corticosterone were determined by IRMA and RIA, respectively. Neonatal thymulin gene therapy in the athymic mice restored their serum thymulin levels and increased corticotrope CD, VD and CS in both control and athymic mice. Athymic mice showed only a marginal reduction in corticotrope CD, VD and CS. In these mutants hypothalamic CRH content was slightly increased, whereas adrenal corticosterone tended to be lower. Thymulin administration to adult mice tended to reverse these changes. Our results suggest a possible modulating effect of thymulin on the corticotrope population and the adrenal gland, confirming the existence of a bidirectional thymus-pituitary-adrenal axis.

Thymulin gene therapy prevents the histomorphometric changes induced by thymulin deficiency in the thyrotrope population of mice.

There is evidence of the existence of a bidirectional relationship between the thymus gland and the thyroid axis. Since the thymic peptide thymulin possesses hypophysiotropic activity, we undertook the task of assessing the histomorphometric changes induced by thymulin deficiency on the thyrotrope population of normal mice and the action of neonatal thymulin gene therapy on the thyrotropin (TSH)-cells of nude mice. C57BL/6 mice were subjected to immunoneutralization of circulating thymulin from postnatal day 1 to the end of the study (postnatal day 32) by intraperitoneal injections of rabbit anti-factor thymulin serum (α-FTS) and normal rabbit serum in controls. Also, neonatal thymulin gene therapy was implemented in athymic nude mice using an adenoviral vector expressing a gene for thymulin (RAd-FTS). On postnatal day 1, heterozygous (nu/+) and homozygous (nu/nu) pups received a single bilateral intramuscular (i.m.) injection of either RAd-FTS or RAd-GFP (the latter being the control vector). The pituitaries were immunostained for TSH. Thymulin immunoneutralization severely reduced serum thymulin (p < 0.01). We detected a significant (p < 0.05) decrease in cell size (CS) and volume density (VD) with a nonsignificant decrease in cell density (CD) in C57BL/6 in both males and females. A single neonatal i.m. injection of RAd-FTS markedly increased the circulating levels of serum thymulin in the athymic mice and increased the CD (p < 0.05), CS (p < 0.01) and VD (p < 0.01) of the thyrotrope population in nu/nu mice. Thyroid histology was not affected. Our results suggest a possible modulating effect of thymulin on the thyrotrope population.

Morphological restoration of gonadotrope population by thymulin gene therapy in nude mice.

The integrity of the thymus during the first week of life is necessary for a proper maturation of the pituitary-gonadal axis as revealed by the significantly reduced levels of circulating gonadotropins in congenitally athymic (nude) mice. In the present work we studied the impact of athymia and the effect of neonatal thymulin gene therapy on the pituitaries of adult nude mice. Also circulating thymulin and gonadotropin levels were evaluated. We used an adenoviral vector expressing a synthetic gene for the thymic peptide thymulin (metFTS) termed RAd-FTS. On postnatal day 1, each experimental heterozygous (nu/+) and homozygous (nu/nu) pup of both sexes received a single bilateral i.m. injection of RAd-FTS or RAd-GFP/TK, a control vector expressing green fluorescent protein. On postnatal days 51-52, mice were bled and sacrificed, their pituitaries were immediately dissected, fixed and immunostained. Morphometry was performed by means of an image analysis system. The following parameters were calculated: volume density (VD: cell area/reference area), cell density (CD: number of cells/reference area), and cell size (expressed in microm(2)). Serum thymulin levels were measured by a bioassay and gonadotropin levels were assayed by RIA. It was observed that neonatal thymulin gene therapy in the athymic mice restored their serum thymulin levels and prevented the reduction in circulating gonadotropin levels. The histometrical analysis revealed that the treatment prevented the reduction in gonadotrope CD and the VD in athymic mice. Our data suggest that thymulin gene therapy may be an effective strategy to approach reproductive deficits associated with endocrine thymus dysfunction.

The thymus-neuroendocrine axis: physiology, molecular biology, and therapeutic potential of the thymic peptide thymulin.

Thymulin is a thymic hormone exclusively produced by the thymic epithelial cells. It consists of a nonapeptide component coupled to the ion zinc, which confers biological activity to the molecule. After its discovery in the early 1970s, thymulin was characterized as a thymic hormone involved in several aspects of intrathymic and extrathymic T cell differentiation. Subsequently, it was demonstrated that thymulin production and secretion is strongly influenced by the neuroendocrine system. Conversely, a growing core of information, to be reviewed here, points to thymulin as a hypophysotropic peptide. In recent years, interest has arisen in the potential use of thymulin as a therapeutic agent. Thymulin was shown to possess anti-inflammatory and analgesic properties in the brain. Furthermore, an adenoviral vector harboring a synthetic gene for thymulin, stereotaxically injected in the rat brain, achieved a much longer expression than the adenovirally mediated expression in the brain of other genes, thus suggesting that an anti-inflammatory activity of thymulin prevents the immune system from destroying virus-transduced brain cells. Other studies suggest that thymulin gene therapy may also be a suitable therapeutic strategy to prevent some of the endocrine and metabolic alterations that typically appear in thymus-deficient animal models. The present article briefly reviews the literature on the physiology, molecular biology, and therapeutic potential of thymulin.

Potential of gene therapy for restoration of endocrine thymic function in thymus-deficient animal models.

The aim of the present article is to discuss the potential of gene therapy for thymic hormones as a novel therapeutic strategy to treat dyshomeostatic conditions associated with congenital athymia or hypofunction of the endocrine thymus. Recent studies using an adenoviral vector harboring a synthetic gene for the thymic peptide thymulin are reviewed. This adenoviral vector was injected intramuscularly in thymectomized and nude mice as well as in thymectomized rats. Transduced myocytes acted as an ectopic source of thymulin thus restoring circulating thymulin levels to normal values. This restorative effect was long lasting (several months) even though an adenoviral vector was used. In the rat brain, adenovirally-mediated delivery of the synthetic gene for thymulin achieved longer expression than in the case of adenovirally-delivered reporter genes, which is consistent with the reported antiinflammatory activity of thymulin in the brain. Furthermore, neonatal thymulin gene therapy in nude female mice was able to prevent the pituitary and ovarian alterations that typically occur in this mutant after puberty. Neonatal thymulin gene therapy in nude mice was able to prevent some of the alterations in lipid metabolism that develop during adult life in congenitally athymic mice. We conclude that the availability of the above biotechnological tools should boost basic studies on the molecular biology of thymulin and should also allow an assessment of the potential of gene therapy to restore circulating thymulin levels in thymodeficient animal models and eventually, in humans.

Thymulin gene therapy prevents the reduction in circulating gonadotropins induced by thymulin deficiency in mice.

Integrity of the thymus during perinatal life is necessary for a proper maturation of the pituitary-gonadal axis in mice and other mammalian species. Thus congenitally athymic (nude) female mice show significantly reduced levels of circulating gonadotropins, a fact that seems to be causally related to a number of reproductive derangements described in these mutants. Interestingly, a number of in vitro studies suggest that the thymic peptide thymulin may be involved in thymus-pituitary communication. To determine the consequences of low serum thymulin in otherwise normal animals, we induced short (8 days)- and long (33 days)-term thymulin deficiency in C57BL/6 mice by neonatally injecting (intraperitoneally) an anti-thymulin serum and assessed their circulating gonadotropin levels at puberty and thereafter. Control mice received an irrelevant antiserum. Gonadotropins were measured by radioimmunoassay and thymulin by bioassay. Both long- and short-term serum thymulin immunoneutralization resulted in a significant reduction in the serum levels of gonadotropins at 33 and 45 days of age. Subsequently, we injected (intramuscularly) an adenoviral vector harboring a synthetic DNA sequence (5'-ATGCAAGCCAAATCTCAAGGTGGATCCAACTAGTAG-3') encoding a biologically active analog of thymulin, methionine-FTS, in newborn nude mice (which are thymulin deficient) and measured circulating gonadotropin levels when the animals reached 52 days of age. It was observed that neonatal thymulin gene therapy in the athymic mice restored their serum thymulin levels and prevented the reduction in circulating gonadotropin levels that typically emerges in these mutants after puberty. Our results indicate that thymulin plays a relevant physiological role in the thymus-pituitary-gonadal axis.

Partial prevention of hepatic lipid alterations in nude mice by neonatal thymulin gene therapy.

During adult life athymic (nude) male mice display not only a severe T-cell-related immunodeficiency but also endocrine imbalances and a moderate hyperglycemia. We studied the impact of congenital athymia on hepatic lipid composition and also assessed the ability of neonatal thymulin gene therapy to prevent the effects of athymia. We constructed a recombinant adenoviral vector, RAd-metFTS, expressing a synthetic DNA sequence encoding met-FTS, an analog of the thymic peptide facteur thymique sérique (FTS), whose Zn-bound biologically active form is known as thymulin. On postnatal day 1-2 homozygous (nu/nu) nude and heterozygous (nu/+) mice were injected with 10(8) pfu of RAd-metFTS or RAd-betagal (control vector) intramuscularly. The animals were processed at 52 d of age. Serum thymulin, glycemia, hepatic phospholipid FA composition and free and esterified cholesterol were determined. Adult homozygous male nudes were significantly (P < 0.01) hyperglycemic when compared with their heterozygous counterparts (2.04 vs. 1.40 g/L, respectively). The relative percentage of 16:0, 18:1 n-9, and 18:1n-7 FA was lower, whereas that of 18:0, 20:4n-6, and 22:6n-3 FA was higher, in hepatic phospholipid (PL) of nu/nu animals as compared with their nu/+ counterparts. Some of these alterations, such as that in the relative content of 22:6n-3 in liver PL and the unsaturation index, were completely or partially prevented by neonatal thymulin gene therapy. We conclude that the thymus influences lipid metabolism and that thymulin is involved in this modulatory activity.

Peripheral and mesencephalic transfer of a synthetic gene for the thymic peptide thymulin.

Thymulin is a thymic peptide with antiinflammatory activity in the brain. We constructed a recombinant adenoviral vector, RAd-FTS, expressing a synthetic DNA sequence encoding met-FTS, a biologically active analog of thymulin and used it for peripheral and central gene transfer in rats. Thymulin concentration in serum and brain tissue was determined by bioassay. Reporter gene expression in the substantia nigra (SN) was quantitated by enzymohistochemistry or fluorescence microscopy using an appropriate image analysis software. A single intramuscular injection (10(8) plaque forming units (pfu)/animal) of RAd-FTS in thymectomized rats (nondetectable serum thymulin) induced supraphysiologic serum thymulin levels for at least 110 days (123+/-22 fg/ml versus 598+/-144 fg/ml in intact and vector-injected rats, respectively). Stereotaxic intranigral injection of RAd-FTS induced steady expression levels of met-FTS for at least 90 days, whereas expression of adenovirally transferred reporter genes coding for green fluorescent protein fused to HSV thymidine kinase (GFP-TK)(fus) or E.coli beta-galactosidase (beta-gal), declined drastically within a month (% transgene expression in the SN on post-injection day 30 relative to day 2 was: 18, <1 and 125%, for beta-gal, (GFP-TK)(fus) and met-FTS, respectively). We conclude that RAd-FTS constitutes a suitable biotechnological tool for the assessment of peripheral and central thymulin gene therapy in animal models of nigral dopaminergic neurodegeneration induced by pro-inflammatory agents.

Gene therapy for long-term restoration of circulating thymulin in thymectomized mice and rats.

Thymulin is a thymic peptide possessing hypophysiotropic activity and antiinflammatory effects in the brain. We constructed a synthetic DNA sequence encoding met-FTS, a biologically active analog of thymulin, and subsequently cloned it into different expression vectors. A sequence optimized for expression of met-FTS in rodents, 5'-ATGCAGGCCAAGTCGCAGGGGGGGTCGAACTAGTAG-3', was cloned in the mammalian expression vectors pCDNA3.1(+) and phMGFP (which expresses the Monster Green Fluorescent Protein), thus obtaining pcDNA3.1-metFTS and p-metFTS-hMGFP, which express met-FTS and the fluorescent fusion protein metFTS-hMGFP, respectively. The synthetic sequence was also used to construct the adenoviral vector RAd-metFTS, which expresses met-FTS. Transfection of HEK293 and BHK cells with pcDNA3.1-metFTS (experimental groups) or pcDNA3.1 (control), led to high levels of thymulin bioactivity (>600 versus <0.1 pg/ml in experimental and control supernatants, respectively). Transfection of HEK293 and BHK cells with pmetFTS-hMGFP revealed a cytoplasmic and nuclear distribution of the fluorescent fusion protein. A single intramuscular (i.m.) injection (10(7) plaque forming units (PFU)/mouse or 10(8) PFU/rat) of RAd-metFTS in thymectomized animals (nondetectable serum thymulin) restored serum thymulin levels for at least 110 and 130 days post-injection in mice and rats, respectively. We conclude that RAd-metFTS constitutes a suitable biotechnological tool for the implementation of thymulin gene therapy in animal models of chronic brain inflammation.

Thymus and aging: potential of gene therapy for restoration of endocrine thymic function in thymus-deficient animal models.

OBJECTIVE AND BACKGROUND: The aim of the present article is to discuss the potential of gene therapy for thymic hormones as a novel therapeutic strategy to treat dyshomeostatic states associated with athymia, as Di George syndrome, or hypothymic conditions like those associated with AIDS, chronic stress or aging. First we review the advantages of the athymic (nude) mouse as an animal model to implement experimental thymic hormone gene therapy strategies to restore endocrine thymic function. The aging rat, known to be markedly hypothymic, is also considered as an alternative model. METHODS AND EXPECTED RESULTS: The possibility of constructing adenoviral vectors harboring a synthetic gene for the thymic hormone thymulin is discussed. The adenoviral vector so constructed would then be injected intramuscularly in nude mice or senile rats. Transduced myocytes should then begin to act as an ectopic source of thymulin thus restoring circulating thymulin levels to normal youthful levels. CONCLUSION: We conclude that the implementation of thymulin gene therapy should provide novel biotechnological tools that will boost basic studies on the molecular biology of thymulin and would also allow an assessment of the potential of gene therapy to restore circulating thymulin levels in thymodeficient animal models.