Psoriasiform skin disease in transgenic pigs with high-copy ectopic expression of human integrins α2 and β1

Psoriasis is a complex human-specific disease characterized by perturbed keratinocyte proliferation and a pro-inflammatory environment in the skin. Porcine skin architecture and immunity are very similar to that in humans, rendering the pig a suitable animal model for studying the biology and treatment of psoriasis. Expression of integrins, which is normally confined to the basal layer of the epidermis, is maintained in suprabasal keratinocytes in psoriatic skin, modulating proliferation and differentiation as well as leukocyte infiltration. Here, we generated minipigs co-expressing integrins α2 and β1 in suprabasal epidermal layers. Integrin-transgenic minipigs born into the project displayed skin phenotypes that correlated with the number of inserted transgenes. Molecular analyses were in good concordance with histological observations of psoriatic hallmarks, including hypogranulosis and T-lymphocyte infiltration. These findings mark the first creation of minipigs with a psoriasiform phenotype resembling human psoriasis and demonstrate that integrin signaling plays a key role in psoriasis pathology.

Summary: A cloned porcine disease model to advance topical treatment in the debilitating skin disorder psoriasis.

Langerhans cell markers CD1a and CD207 are the most rapidly responding genes in lesional psoriatic skin following adalimumab treatment

TNFα-, IL-23- and IL-17-targeting drugs are highly effective in the treatment of psoriasis. However, the precise molecular mechanism remains unknown. In psoriatic skin, the presence of Langerhans cells (LCs) is reduced, but the role of LC is poorly understood. The purpose of this study was to investigate the impact of TNFα and IL-23/IL-17 on the presence of LC in the skin during treatment. Therefore, psoriatic skin was investigated before and after 4 days of adalimumab or ustekinumab treatment. Furthermore, TNFα and IL-17A stimulation was investigated in an ex vivo model of epidermis and dermis from healthy normal skin kept in cultures at an air-liquid interphase for 4 days. In a gene array analysis, we found that the two LC markers, CD1a and CD207, were among the most up- or downregulated genes in psoriatic skin after anti-TNFα therapy. Validation showed that both mRNA expression and protein level followed the same pattern and became significantly upregulated after 4 days of treatment. No changes were seen after ustekinumab treatment. In the ex vivo skin model, a decrease in the CD1a level was seen after TNFα stimulation and it was caused by LC migration from epidermis. No response in LC migration was seen after IL-17A stimulation. Taken together, we demonstrated that changes in the LC level in epidermis precede the histological and clinical changes during adalimumab treatment in psoriatic skin. Furthermore, TNFα plays a prominent role in orchestrating LC migration in the skin. This seems not to be the true for the IL-23/IL-17A pathway.

Leptin deficiency in mice counteracts imiquimod (IMQ)-induced psoriasis-like skin inflammation while leptin stimulation induces inflammation in human keratinocytes

Leptin is an adipocyte-derived cytokine secreted mostly by adipose tissue. Serum leptin levels are elevated in obese individuals and correlate positively with body mass index (BMI). Interestingly, serum leptin levels are also elevated in patients with psoriasis and correlate positively with disease severity. Psoriasis is associated with obesity; patients with psoriasis have a higher incidence of obesity, and obese individuals have a higher risk of developing psoriasis. Additionally, obese patients with psoriasis experience a more severe degree of psoriasis. In this study, we hypothesised that leptin may link psoriasis and obesity and plays an aggravating role in psoriasis. To investigate leptin's role in psoriasis, we applied the widely accepted imiquimod (IMQ)-induced psoriasis-like skin inflammation mouse model on leptin-deficient (ob/ob) mice and evaluated psoriasis severity. Moreover, we stimulated human keratinocytes with leptin and investigated the effect on proliferation and expression of pro-inflammatory proteins. In ob/ob mice, clinical signs of erythema, infiltration and scales in dorsal skin and inflammation in ear skin, as measured by ear thickness, were attenuated and compared with wt mice. Moreover, IL-17A and IL-22 mRNA expression levels, as well as increased epidermal thickness, were significantly less induced. In vitro, the effect of leptin stimulation on human keratinocytes demonstrated increased proliferation and induced secretion of several pro-inflammatory proteins; two hallmarks of psoriasis. In conclusion, leptin deficiency attenuated IMQ-induced psoriasis-like skin inflammation in a mouse model, and leptin stimulation induced a pro-inflammatory phenotype in human keratinocytes, thus, supporting an aggravating role of leptin in psoriasis.

Robust Lentiviral Gene Delivery But Limited Transduction Capacity of Commonly Used Adeno-Associated Viral Serotypes in Xenotransplanted Human Skin

Skin is an easily accessible organ, and therapeutic gene transfer to skin remains an attractive alternative for the treatment of skin diseases. Although we have previously documented potent lentiviral gene delivery to human skin, vectors based on adeno-associated virus (AAV) rank among the most promising gene delivery tools for in vivo purposes. Thus, we compared the potential usefulness of various serotypes of recombinant AAV vectors and lentiviral vectors for gene transfer to human skin in a xenotransplanted mouse model. Vector constructs encoding firefly luciferase were packaged in AAV capsids of serotype 1, 2, 5, 6, 8, and 9 and separately administered by intradermal injection in human skin transplants. For all serotypes, live bioimaging demonstrated low levels of transgene expression in the human skin graft, and firefly luciferase expression was observed primarily in neighboring tissue outside of the graft. In contrast, gene delivery by intradermally injected lentiviral vectors was efficient and led to extensive and persistent firefly luciferase expression within the human skin graft only. The study demonstrates the limited capacity of single-stranded AAV vectors of six commonly used serotypes for gene delivery to human skin in vivo.

Exploring Valrubicin's Effect on Propionibacterium Acnes-Induced Skin Inflammation in Vitro and in Vivo

Acne is a common skin disease involving colonization with Propionibacterium acnes (P. acnes), hyperproliferation of the follicular epithelium and inflammatory events. Valrubicin is a second-generation anthracycline, non-toxic upon contact, and available in a topical formulation. Valrubicin’s predecessor doxorubicin possesses antibacterial effects and previously we demonstrated that valrubicin inhibits keratinocyte proliferation and skin inflammation suggesting beneficial topical treatment of acne with valrubicin. This study aims to investigate valrubicin’s possible use in acne treatment by testing valrubicin’s antibacterial effects against P. acnes and P. acnes-induced skin inflammation in vitro and in vivo. Valrubicin was demonstrated not to possess antibacterial effects against P. acnes. Additionally, valrubicin was demonstrated not to reduce mRNA and protein expression levels of the inflammatory markers interleukin (IL)-1β, IL-8, and tumor necrosis factor (TNF)-α in vitro in human keratinocytes co-cultured with P. acnes. Moreover, in vivo, valrubicin, applied both topically and intra-dermally, was not able to reduce signs of inflammation in mouse ears intra-dermally injected with P. acnes. Taken together, this study does not support beneficial antibacterial and anti inflammatory effects of topical valrubicin treatment of acne.

Debio 0932, a new oral Hsp90 inhibitor, alleviates psoriasis in a xenograft transplantation model

Debio 0932 is a novel oral heat shock protein 90 (Hsp90) inhibitor developed for anti-cancer therapy. Surprising-ly, during the first clinical trial, one psoriasis patient experienced complete remission of his skin manifestation. However, a possible therapeutic utility of Hsp90 in psoriasis has not previously been reported. The objective of the present study was to explore the ability of Debio 0932 to alleviate psoriasis in a preclinical model. A psoriasis xenograft transplantation model was employed where skin from 5 psoriasis patients was transplanted onto immunodeficient mice (8 xenografts per donor). Debio 0932 was administered perorally daily for 3 weeks and resulted in significant clinical alleviation of psoriasis by day 11 and reduced epidermal thickness evaluated post-treatment. Alleviation of psoriasis in the psoriasis xenograft transplantation model, which may be due to Hsp90's involvement in signalling pathways that are up-regulated in psoriasis, substantiates a potential role of Debio 0932 in psoriasis treatment.

Valrubicin activates PKCa in keratinocytes: a conceivable mode of action in treating hyper-proliferative skin diseases

BACKGROUND

Valrubicin is a semisynthetic anthracycline developed as an anti-cancer drug able to ameliorate psoriasis and non-melanoma skin cancer (NMSC) by topical application in animal models. Valrubicin decreases cell proliferation, and induces apoptosis; however its mode of action is still unknown. Valrubicin localizes in the cytoplasm and its valerate moiety resembles diacylglycerol, an activator of protein kinase C (PKC) α, which belongs to the PKC family of cytoplasmic serine/threonine protein kinases. PKCα is observed in the suprabasal layers of normal skin and is associated to keratinocyte growth arrest and differentiation processes. In hyper-proliferative skin diseases the presence of PKCα is altered.

OBJECTIVE

The aim of the present study was to investigate valrubicin's mode of action in keratinocytes by studying its possible effect on PKCα activation.

METHODS

PKCα's characteristic to translocate from the cytoplasm to the cellular membrane when activated was assessed by measuring the amount of PKCα in the soluble and membrane-bound protein fractions isolated from valrubicin stimulated keratinocytes and by visualizing PKCα in stimulated cells over time. Downstream signaling was investigated by measuring the amount of phosphorylated Myristoylated Alanine-rich C-kinase substrate (MARCKS) and extracellular signal-regulated kinases (ERK) 1/2 of valrubicin-stimulated keratinocytes. To investigate whether there was a direct interaction between valrubicin and PKCα, an activity assay employing purified PKCα protein was used.

RESULTS

Valrubicin activates PKCα in vitro as shown by PKCα's translocation and phosphorylation of downstream signaling molecules.

CONCLUSION

Valrubicin stimulates PKCα activity and downstream signaling which may contribute to its beneficial effect in psoriasis and NMSC.

Topical valrubicin application reduces skin inflammation in murine models

BACKGROUND

Valrubicin is a cytostatic anthracycline analogue, lacking toxicity by skin and tissue contact, and represents a new drug with potential for topical treatment of psoriasis and nonmelanoma skin cancer (NMSC); the beneficial effects have been partly explained by its antiproliferative and proapoptotic characteristics.

OBJECTIVES

To assess the effect of valrubicin on skin inflammation as inflammation also plays a key role in psoriasis and NMSC.

METHODS

The effect of topical valrubicin treatment on skin inflammation in vivo was addressed in skin inflammation mouse models, where 12-O-tetradecanoylphorbol 13-acetate was used to induce irritant contact dermatitis. An acute and a chronic model were included, to investigate the effect of valrubicin in short-term inflammation and in more persistent inflammation. Inflammation-associated ear oedema was evaluated by measuring ear thickness, infiltration of neutrophil cells, and expression of inflammatory cytokines, interleukin (IL)-1β and IL-6.

RESULTS

Topical valrubicin treatment effectively reduced the inflammatory response in the acute and the chronic models.

CONCLUSIONS

The present data document an anti-inflammatory effect of valrubicin, and may suggest an interesting new role for valrubicin in other debilitating skin diseases in which inflammation is a significant factor.

Stereological estimation of epidermal volumes and dermo-epidermal surface area in normal skin

Quantitative morphological studies of the healthy epidermis are essential in providing a range of parameter estimates that can be considered within the range of normality. Stereology is a set of statistical tools that provides potentially unbiased and precise estimates of 3-dimensional tissue characteristics from 2-dimensional sections. We set out to establish reference values for the volume of the viable epidermis contained within a four-millimetre punch biopsy (V(epi)), the volume of the stratum corneum (V(SC)) and the surface area of the dermo-epidermal junction(A(DEJ)) in 4 predetermined body regions by use of stereology. Four-millimetre punch biopsies were taken from 20 freshly diseased corpses, fixed in formalin and embedded in paraffin. V(epi), V(SC) and A(DEJ) were established stereologically for all 4 body locations followed by pairwise comparison of means after Bonferroni correction. V(epi) was significantly larger in the sole compared to all other body locations (p < 0.01). Furthermore, linear regression analysis showed a strong linear relationship between V(epi) and V(SC) in the sole (r = 0.70). Our results suggest that the viable layers of the epidermis might also serve a mechanical function, either directly or by providing the stratum corneum with keratinocytes to support the hyperkeratosis in the weight-bearing parts of the skin.

Targeting of human interleukin-12B by small hairpin RNAs in xenografted psoriatic skin

BACKGROUND

Psoriasis is a chronic inflammatory skin disorder that shows as erythematous and scaly lesions. The pathogenesis of psoriasis is driven by a dysregulation of the immune system which leads to an altered cytokine production. Proinflammatory cytokines that are up-regulated in psoriasis include tumor necrosis factor alpha (TNFα), interleukin-12 (IL-12), and IL-23 for which monoclonal antibodies have already been approved for clinical use. We have previously documented the therapeutic applicability of targeting TNFα mRNA for RNA interference-mediated down-regulation by anti-TNFα small hairpin RNAs (shRNAs) delivered by lentiviral vectors to xenografted psoriatic skin. The present report aims at targeting mRNA encoding the shared p40 subunit (IL-12B) of IL-12 and IL-23 by cellular transduction with lentiviral vectors encoding anti-IL12B shRNAs.

METHODS

Effective anti-IL12B shRNAs are identified among a panel of shRNAs by potency measurements in cultured cells. The efficiency and persistency of lentiviral gene delivery to xenografted human skin are investigated by bioluminescence analysis of skin treated with lentiviral vectors encoding the luciferase gene. shRNA-expressing lentiviral vectors are intradermally injected in xenografted psoriatic skin and the effects of the treatment evaluated by clinical psoriasis scoring, by measurements of epidermal thickness, and IL-12B mRNA levels.

RESULTS

Potent and persistent transgene expression following a single intradermal injection of lentiviral vectors in xenografted human skin is reported. Stable IL-12B mRNA knockdown and reduced epidermal thickness are achieved three weeks after treatment of xenografted psoriatic skin with lentivirus-encoded anti-IL12B shRNAs. These findings mimic the results obtained with anti-TNFα shRNAs but, in contrast to anti-TNFα treatment, anti-IL12B shRNAs do not ameliorate the psoriatic phenotype as evaluated by semi-quantitative clinical scoring and by immunohistological examination.

CONCLUSIONS

Our studies consolidate the properties of lentiviral vectors as a tool for potent gene delivery and for evaluation of mRNA targets for anti-inflammatory therapy. However, in contrast to local anti-TNFα treatment, the therapeutic potential of targeting IL-12B at the RNA level in psoriasis is questioned.

Topical application of valrubicin has a beneficial effect on developing skin tumors

Valrubicin is a second generation anthracycline characterized by an excellent safety profile presenting no skin toxicity or necrosis upon contact. In its current liquid formulation (Valstar; Indevus Pharmaceuticals, Lexington, MA), it is approved solely for the treatment of bladder cancer. Recently, valrubicin was incorporated in a cream formulation rendering this drug available for topical application. The cytostatic property of valrubicin can, thus, be employed for treating hyperproliferative skin diseases as was recently described for psoriasis. In the present study, the effect of topical application of valrubicin was investigated in skin tumor development; we hypothesized that valrubicin may be employed in treating actinic keratosis, a hyperproliferative skin condition that may transform into malignancy. A two-stage chemical mouse skin carcinogenesis model that represents the multistage etiology of human skin cancer-from developing papillomas to squamous cell carcinoma (SCC) was used. Moreover, two human skin SCC cell lines: DJM-1 and HSC-1 were cultured, to further investigate the effect of valrubicin in vitro. Cell viability was assessed by adenosine triphosphate presence, proliferation as proliferative cell nuclear antigen expression and apoptosis as cytokeratin 18 cleavage, caspase activation, poly-adenosine diphosphate-ribose-polymerase cleavage and bax and bcl-2 regulation. Valrubicin significantly inhibited tumor formation in the mouse skin carcinogenesis model and significantly decreased cell viability of the cultured human skin SCC cells. In both mouse skin and SCC cells, proliferation was significantly decreased. Apoptosis was significantly increased in SCC cells but unchanged in the treated mouse skin at study completion. This study demonstrated that topical application of valrubicin has a beneficial effect in treating developing skin tumors.

Valrubicin in a topical formulation treats psoriasis in a xenograft transplantation model

Valrubicin is a cytostatic drug currently approved by the American Federal Drug Administration as a trademarked Valstar sterile solution for the treatment of bladder cancer. Valrubicin has shown an excellent therapeutic potential with minimal toxicity. This study investigated the effect in vivo of treating psoriasis with a daily topical application of valrubicin cream in a psoriasis xenograft transplantation model. Psoriasis is characterized by an accelerated keratinocyte proliferation, resulting in increased epidermal thickness. We thus studied the cytostatic potential of valrubicin on epidermal keratinocytes. In vivo, valrubicin treatment resulted in a normalization of epidermal morphology and a reduction in epidermal thickness after 12 days. In addition, the dermal vessel pattern was reduced and the stratum granulosum was regained. Staining for a regenerative proliferation marker showed a decrease in keratinocyte proliferation, and scattered epidermal cells showed apoptosis. In vitro, valrubicin was shown to localize solely to the cell cytoplasm in cultured keratinocytes and to reduce keratinocyte proliferation as well as increase apoptosis by activation of caspases 3, 7, and 9. Our results indicated that valrubicin successfully treats psoriasis in a xenograft transplantation model, suggesting that topical valrubicin may become an upcoming treatment for psoriasis.

Amelioration of psoriasis by anti-TNF-alpha RNAi in the xenograft transplantation model

Tumor necrosis factor-alpha (TNF-alpha) is upregulated in psoriatic skin and represents a prominent target in psoriasis treatment. The level of TNF-alpha-encoding mRNA, however, is not increased in psoriatic skin, and it remains unclear whether intervention strategies based on RNA interference (RNAi) are therapeutically relevant. To test this hypothesis the present study describes first the in vitro functional screening of a panel of short hairpin RNAs (shRNAs) targeting human TNF-alpha mRNA and, next, the transfer of the most potent TNF-alpha shRNA variant, as assessed in vitro, to human skin in the psoriasis xenograft transplantation model by the use of lentiviral vectors. TNF-alpha shRNA treatment leads to amelioration of the psoriasis phentotype in the model, as documented by reduced epidermal thickness, normalization of the skin morphology, and reduced levels of TNF-alpha mRNA as detected in skin biopsies 3 weeks after a single vector injection of lentiviral vectors encoding TNF-alpha shRNA. Our data show efficient lentiviral gene delivery to psoriatic skin and therapeutic applicability of anti-TNF-alpha shRNAs in human skin. These findings validate TNF-alpha mRNA as a target molecule for a potential persistent RNA-based treatment of psoriasis and establish the use of small RNA effectors as a novel platform for target validation in psoriasis and other skin disorders.

Interleukin-20 plays a critical role in maintenance and development of psoriasis in the human xenograft transplantation model

BACKGROUND

Interleukin (IL)-20 is a recently discovered cytokine displaying increased levels in psoriatic lesions. Interestingly, IL-20 levels decrease with antipsoriatic treatment, correlating with clinical improvement. However, the role of IL-20 in the aetiology of psoriasis is unknown.

OBJECTIVES

In this study, we investigate the effects both of blocking IL-20 signalling in psoriatic plaques and of adding IL-20 to nonlesional psoriasis skin.

METHODS

We employed the human skin xenograft transplantation model in which psoriatic plaques and nonlesional keratome skin biopsies obtained from donors with moderate to severe plaque psoriasis were transplanted on to immuno-deficient mice. The transplanted mice were treated with anti-IL-20 antibodies or recombinant human IL-20.

RESULTS

We demonstrate that blocking IL-20 signalling with anti-IL-20 antibodies induces psoriasis resolution and inhibits psoriasis induction. We also demonstrate that continuous IL-20 infusion, together with injection of additional nonactivated leucocytes, promotes induction of psoriasis in nonlesional skin from patients with psoriasis.

CONCLUSIONS

The results suggest that IL-20 plays a critical role in the induction and maintenance of psoriasis, and IL-20 is suggested as a new possible specific target in psoriasis treatment.

[Interleukin-20--a new target in psoriasis treatment]

Interleukin-20 (IL-20) is suggested as a new target in psoriasis treatment. It was first described in 2001, and the potential role of this cytokine in psoriasis was suggested because mice which were over-expressing IL-20 developed a psoriasis-like phenotype of the skin. Subsequently, IL-20 expression levels were found to be increased in psoriasis skin, and it was observed that these levels normalized upon psoriasis treatment. In the psoriasis xenograft transplantation model, administration of IL-20 to non-lesional psoriasis skin transplanted onto immune-deficient mice demonstrated that IL-20 was involved in the psoriasis induction. More interestingly, improvement of psoriasis was induced by blocking IL-20 signaling.

Interleukin-20 as a target in psoriasis treatment

Interleukin-20 (IL-20) is a new member of the IL-10 cytokine family discovered by a structural algorithm. IL-20 transgenic mice displayed skin abnormalities reminiscent of psoriasis, a finding that has prompted the investigation of this new interleukin in relation to this disease. This article reviews the role of IL-20 and its implication in psoriasis. It is shown that IL-20 and its receptors are found in human skin and that IL-20 is involved in proliferation, angiogenesis, and chemotaxis, all characteristics of psoriasis. We demonstrated that IL-20 induced the thickening of human epidermis in vivo; however, this thickening does not seem to be related to a direct effect of IL-20 on hyperproliferation since the growth of normal human epidermal keratinocytes (NHEKs) cultured in vitro was not affected by IL-20. On the other hand, in vitro, IL-20 stimulated human peripheral blood mononuclear cells (PBMCs) to produce proinflammatory cytokines and, in vivo, IL-20 in combination with PBMCs induced psoriasis. This may suggest that IL-20 indirectly exerts its proliferative effects on keratinocytes via immune cells present in the skin. Finally, we found that blocking IL-20 signaling in psoriasis improves psoriasis, suggesting that IL-20 is a potential target in psoriasis treatment.

Aged Human Bone Marrow Stromal Cells Maintaining Bone Forming Capacity in vivo Evaluated Using an Improved Method of Visualization

Age-related decreased osteoblast function is a well-known but poorly understood phenomenon. Previous studies that examined the effects of donor age on osteoblast functions employed in vitro assays that may not reflect the true osteoblast capacity for bone formation. Thus, we have developed an in vivo assay for quantifying the bone forming capacity (BFC) and we compared the BFC of osteoblastic cells obtained from young and old donors. Osteoblasts were obtained from human bone marrow stromal cell cultures and implanted subcutaneously in immuno-deficient mice (NOD/LtSz- Prkdc(scid)). After 8 weeks, the implants were removed and embedded un-decalcified in methyl methacrylate (MMA). Sections were stained histochemically with Goldner's Trichrome stain and immuno-histochemically using human-specific antibodies against known osteogenic markers. Implanted human marrow stromal cells (hMSC) were able to form bone in vivo. The donor origin of bone was verified using several human-specific antibodies. Dose-response experiments demonstrated that 5 x 10(5) hMSC per implant gave the maximal bone formation after 8 weeks. No difference in BFC was observed between cells obtained from young (24-30 years old; mean age 27 +/- 2 years, n = 5) and old (71-81 years old; mean age 75 +/- 4 years, n = 5) donors. Our study demonstrates that the capacity of hMSC to form bone in vivo is maintained with age and suggests that the observed senescence-associated decrease in bone formation is due to a defect in the bone microenvironment, the nature of which remains to be determined.

The human umbilical cord blood: a potential source for osteoblast progenitor cells

The presence of non-hematopoietic stem cells in the human umbilical cord blood (hUCB) is debated. In this study, we report the isolation of a population of fibroblast-like cells with osteogenic and adipogenic potential that resembles the stromal stem cells found in the bone marrow. Low-density mononuclear cells isolated from hUCB formed few adherent colonies with fibroblast-like morphology after a few days in culture. At confluence, the polyclonal cell populations were characterized. Using FACS analysis and immunocytochemistry, the cells were found to express HLA-ABC, CD9, vimentin, the b subunit of prolyl-4-hydroxylase, integrins a1(CD49a), integrin a3 (CD49c), integrin a5(CD49e), and cytokeratin 18. Furthermore, the cells expressed constitutively transcripts of osteoblast-specific markers: Cbfa1/Runx2, alkaline phosphatase (AP), and collagen type I, and formed a mineralized matrix in vitro visualized by Alizarin red staining. In the presence of normal horse serum and dexamethasone (10(-7) M), the cells formed foci of adipocytes. When the cells were implanted mixed with hydroxyapatite/tricalcium phosphate powder in the subcutis of immunocompromised mice for 8 weeks, they formed osteogenic tissue and a myelosupportive microenviroment that enclosed hematopoietic cells and adipocytes. Our results demonstrate the presence of circulating stem cells with osteogenic and adipogenic differentiation potential in hUCB and may encourage the use of hUCB as a potential source for stem cells to be utilized in cell therapy protocols for various diseases.

Telomerase expression extends the proliferative life-span and maintains the osteogenic potential of human bone marrow stromal cells

Human bone marrow stromal cells (hMSCs) were stably transduced by a retroviral vector containing the gene for the catalytic subunit of human telomerase (hTERT). Transduced cells (hMSC-TERTs) had telomerase activity, and the mean telomere length was increased as compared with that of control cells. The transduced cells have now undergone more than 260 population doublings (PD) and continue to proliferate, whereas control cells underwent senescence-associated proliferation arrest after 26 PD. The cells maintained production of osteoblastic markers and differentiation potential during continuous subculturing, did not form tumors, and had a normal karyotype. When implanted subcutaneously in immunodeficient mice, the transduced cells formed more bone than did normal cells. These results suggest that ectopic expression of telomerase in hMSCs prevents senescence-associated impairment of osteoblast functions.

The interferon alpha induced protein ISG12 is localized to the nuclear membrane

Interferons exert their biological function mainly through the activation of interferon-stimulated genes (ISGs). ISG12 (originally designated p27) belongs to a family of small, interferon alpha inducible genes of unknown function. We have determined the 5' end sequence of ISG12 cDNA from the human cell lines HeLa and AMA by RACE. Comparing this sequence to ISG12 sequences in the expressed sequence tag (EST) database revealed the presence of two alternative splice variants of ISG12 in human cells exhibiting the same open reading frame. We have sequenced the promoter region of the ISG12 gene and found ISRE, IRF1/IRF2, and STAT elements correlating to the interferon alpha inducibility of the gene. Subsequently, we have expressed human ISG12, a 12-kDa hydrophobic protein in the baculovirus expression system and with a C-terminal FLAG-tag in the human cell line 293. Recombinant ISG12 sediments in the nuclear envelope in both cell types. Finally, we have been able to demonstrate the prevalence of the ISG12 gene product in the nuclear envelope of HeLa cells treated with interferon alpha by immunocytochemical analyses. ISG12 is the first interferon induced protein found localizing to the nuclear envelope.

Relationship between CD44 expression and cell proliferation in epithelium and stroma of colorectal neoplasms

The cell surface glycoprotein CD44 is expressed primarily in the region of cell replication in the lower crypt epithelium of colorectal mucosa, and its expression is markedly increased in colorectal neoplasms, suggesting that expression is linked to proliferation. The association between CD44 expression and replication in individual cells was therefore analyzed by double-label immunohistochemistry for CD44 and the cell-cycle-dependent protein proliferating cell nuclear antigen (PCNA). Enhanced expression of CD44 in colorectal neoplasms occurred not only in epithelial cells but also in stromal cells, including lymphocytes and macrophages. On a topographical basis, the cellular localization of CD44 and PCNA were commonly different. Quantitatively, in all cell types studied (epithelial cells and stroma of colorectal mucosa, adenomas, and carcinomas) PCNA was present most frequently in cells lacking CD44. Statistical analysis by logistic regression models indicated that cells negative for CD44 had a higher probability of being positive for PCNA than did cells positive for CD44 (P < 0.001). These data suggest that the enhanced level of CD44 in colorectal neoplasms is asynchronous with cell replication and reflects mechanisms that act on nonproliferative stromal lymphocytes and other mononuclear cells as well as the epithelial cells.

CD44 expression in colorectal adenomas is an early event occurring prior to K-ras and p53 gene mutation

Neoplastic progression of colorectal epithelial cells from benign adenomas to malignant carcinomas appears to result from a series of genetic alterations involving both oncogenes and tumor suppressor genes. This progression was recently found to be associated with expression of splice variant isoforms of CD44, a cell surface hyaluronate receptor implicated in carcinogenesis. In this study we examined the relationship of CD44 expression to somatic genetic events in the adenoma-carcinoma sequence: point mutation of K-ras in codons 12 and 13 and overexpression of p53 protein as a marker of gene mutation. Among 22 small adenomas, CD44 was present in 9 (41%), of which only 1 contained a K-ras mutation. CD44 was absent in the other 2 small adenomas positive for K-ras mutation or p53 overexpression. In contrast to the early expression of CD44 in small adenomas, mutations of K-ras and p53 were detected preferentially in large adenomas and late-stage adenomas containing carcinoma. The frequent expression of CD44 prior to K-ras and p53 gene alterations in colorectal neoplasia suggests that activation of CD44 gene expression is related to earlier events in the adenoma-carcinoma sequence, possibly cell activation and proliferation following APC gene mutation or alteration of DNA methylation.

Expression of CD44 in human lung tumors

CD44 is an integral membrane glycoprotein that functions as a receptor for the extracellular matrix glycan, hyaluronan. Here we report that CD44 is a novel biomarker for non-small cell lung tumors, squamous metaplasia of the lung, and activated type II pneumocytes. We have examined the expression of CD44 in 12 human lung tumor cell lines and 23 fixed, paraffin-embedded lung cancers. CD44 transcription and translation is consistently high among non-small cell tumors (5 of 5 cell lines, 10 of 14 tumors) but rare in small cell tumors (1 of 6 cell lines, 0 of 9 tumors). In normal lung, CD44 was confined to the surface of bronchial basal cells and alveolar macrophages. Squamous metaplasia of the lung showed strong CD44 immunoreactivity. Resting type II pneumocytes were largely CD44 negative but rows of active, surfactant-secreting type II cells had significant amounts of CD44 located on lateral surfaces of adjacent cells. The correlation between CD44 and the non-small cell phenotype was further demonstrated in studies of a cultured small cell lung cancer line induced to exhibit characteristics of a non-small lung cancer by infection with v-Ha-ras. Following ras gen insertion, these cells showed a 40-fold increase in CD44 expression. The CD44 detected in lung cancer cells throughout these studies was predominantly the "standard" rather than the "variant" species. Taken together, these results suggest that CD44 is a protein expressed on non-small cell lung tumors, squamous metaplasia, and activated type II cells. In addition, CD44 in cultured small cell lung cancer cells is transcriptionally activated following differentiation by the ras oncogene. The fact that immunohistochemistry can be used to discriminate among the cell types makes CD44 a valuable new marker for lung neoplasia.