Role of Ucp1 enhancer methylation and chromatin remodelling in the control of Ucp1 expression in murine adipose tissue

AIMS/HYPOTHESIS

Increasing the expression of the brown adipose tissue-specific gene uncoupling protein-1 (Ucp1) is a potential target for treating obesity. We investigated the role of DNA methylation and histone modification in Ucp1 expression in adipose cell lines and ex vivo murine adipose tissues.

METHODS

Methylation state of the Ucp1 enhancer was studied using bisulphite mapping in murine adipose cell lines, and tissue taken from cold-stressed mice, coupled with functional assays of the effects of methylation and demethylation of the Ucp1 promoter on gene expression and nuclear protein binding.

RESULTS

We show that demethylation of the Ucp1 promoter by 5-aza-deoxycytidine increases Ucp1 expression while methylation of Ucp1 promoter-reporter constructs decreases expression. Brown adipose tissue-specific Ucp1 expression is associated with decreased CpG dinucleotide methylation of the Ucp1 enhancer. The lowest CpG dinucleotide methylation state was found in two cyclic AMP response elements (CRE3, CRE2) in the Ucp1 promoter and methylation of the CpG in CRE2, but not CRE3 decreased nuclear protein binding. Chromatin immunoprecipitation assays revealed the presence of the silencing DiMethH3K9 modification on the Ucp1 enhancer in white adipose tissue and the appearance of the active TriMethH3K4 mark at the Ucp1 promoter in brown adipose tissue in response to a cold environment.

CONCLUSIONS/INTERPRETATION

The results demonstrate that CpG dinucleotide methylation of the Ucp1 enhancer exhibits tissue-specific patterns in murine tissue and cell lines and suggest that adipose tissue-specific Ucp1 expression involves demethylation of CpG dinucleotides found in regulatory CREs in the Ucp1 enhancer, as well as modification of histone tails.

Hair follicle neogenesis induced by cultured human scalp dermal papilla cells

AIM

To develop a method by which human hair follicle dermal papilla (DP) cells can be expanded in vitro while preserving their hair-inductive potential for use in follicular cell implantation, a cellular therapy for the treatment of hair loss.

MATERIALS & METHODS

DP cells were isolated from scalp hair follicles in biopsies from human donors. DP cell cultures were established under conditions that preserved their hair-inductive potential and allowed for significant expansion. The hair-inductive potential of cells cultured for approximately 36 doublings was tested in an in vivo flap-graft model. In some experiments, DiI was used to label cells prior to grafting.

RESULTS

Under the culture conditions developed, cultures established from numerous donors reproducibly resulted in an expansion that averaged approximately five population doublings per passage. Furthermore, the cells consistently induced hair formation in an in vivo graft assay. Grafted DP cells appeared in DP structures of newly formed hairs, as well as in the dermal sheath and in the dermis surrounding follicles. Induced hair follicles persisted and regrew after being plucked 11 months after grafting.

CONCLUSION

A process for the propagation of human DP cells has been developed that provides significant expansion of cells and maintenance of their hair-inductive capability, overcoming a major technical obstacle in the development of follicular cell implantation as a treatment for hair loss.

Integration and persistence of an investigational human living skin equivalent (ICX-SKN) in human surgical wounds

AIM

To present the first human clinical data on an investigational living skin graft replacement that is being designed for application where tissue has been lost through surgery, disease or trauma.

MATERIALS & METHODS

The ICX-SKN skin graft replacement is composed of an autosynthesized human collagen-based extracellular matrix and human dermal fibroblasts. In a first study to examine integration and persistence, full-thickness excisional wounds were made in six healthy human female volunteers and the ICX-SKN skin graft replacement applied and dressed. The surgical wounds were examined for up to 28 days post-application and the graft excised from each volunteer.

RESULTS

Pre-excision gross examination revealed that the ICX-SKN skin graft replacement had integrated well in each of the six wounds and that re-epithelialization had occurred in each case. Histological analysis revealed that the ICX-SKN skin graft replacement remained in place and had become vascularized and provided a continuous wound closure. No serious adverse events were reported and no gross scarring or wound contracture was evident in the healed wounds.

CONCLUSION

This is the first report of preliminary evidence indicating the persistence of an autosynthesized, tissue-engineered, living human skin substitute in healed acute wounds in humans.

Hair morphogenesis in vitro: formation of hair structures suitable for implantation

AIM

To develop a construct through which implanted follicular cells will efficiently cause hair regeneration for the treatment of androgenetic alopecia.

MATERIALS & METHODS

Follicular dermal and epidermal cells isolated from embryonic mouse skin were formed into aggregates. The aggregates were incubated in culture for 5-7 days and then implanted intradermally into athymic mice.

RESULTS

During culture, mixed cell aggregates developed into hair-like structures, termed 'proto-hairs'. Proto-hairs contained structures that resembled normal hair components, such as dermal papillae, hair matrix and rudimentary hair shafts. When implanted into mouse skin, they developed further into mature hair follicles capable of prolonged growth.

CONCLUSION

Mixed aggregates of murine follicular cells have the ability to develop in culture into proto-hairs that retain the ability to fully develop into hair follicles after implantation. Proto-hairs from human cells could provide a convenient and practical means by which follicular cells could be implanted for efficient hair regeneration to treat hair loss.

Development and manufacture of an investigational human living dermal equivalent (ICX-SKN)

AIM

To design and manufacture an investigational living skin graft replacement (ICX-SKN) that is able to incorporate into the host, providing healing by primary intent without the need for a second intervention.

MATERIALS & METHODS

The ICX-SKN skin graft replacement has been designed as an allogeneic dermal substitute comprising an extracellular matrix composed largely of human collagen and human dermal fibroblast cells (HDFs). ICX-SKN is first formed by casting a provisional matrix of fibrin, into which HDFs are seeded. Through a process of maturation, HDFs are induced to lay down collagen and other extracellular matrix materials and, as the construct matures, the original fibrin is largely replaced by collagen, which provides tensile strength and flexibility to the construct. In order to design a product and manufacturing system that lends itself to large-scale production the process was developed as a discontinuous process consisting of four stages: 1. batch casting and maturation of the initial construct (pSKN), 2. freeze-drying of pSKN to produce a second intermediate (dSKN), 3. sterilization by gamma-irradiation of dSKN to produce a third intermediate (sSKN), and finally, 4. repopulation of sSKN by fresh HDFs to produce the final product, ICX-SKN skin graft replacement. Preliminary characterization of ICX-SKN and its application in a preclinical model are described.

RESULTS

The 7-week maturation period resulted in a construct (pSKN) with robust handling properties, which was composed mainly of human collagen I. Following development of a process for freeze-drying and subsequent sterilization, the matrix was successfully repopulated with fresh HDFs. In addition, it was demonstrated that human keratinocytes attached and differentiated on the matrix. Application of human keratinocytes to the repopulated constructs (ICX-SKN) resulted in expression of markers of basement membranes that was largely dependent on the presence of living HDFs on the constructs. ICX-SKN graft replacements applied to excision wounds in mice healed and were rapidly re-epithelialized.

CONCLUSIONS

ICX-SKN has been developed as a platform product that can be used as a skin graft replacement and the process by which it is manufactured has been designed for the product to be available to the end-user off-the-shelf and for ease-of-use in practice.

A dual detector capillary waveguide biosensor for detection and quantification of hybridized target

We describe a novel technique for improving the sensitivity of analytical instruments based on the measurement of fluorescent intensity. Independent measurement of the Rayleigh scattered intensity component by means of a second photodetector leads to normalized data, which are independent of various experimental parameters. Incorporation of this technique into a fully automated capillary waveguide biosensor improved the instrument sensitivity by a factor of three. The technique enables quantification, as well as detection, of the hybridized target molecules.

History of regenerative medicine: looking backwards to move forwards

If the song by the international popstar Sting is to be relied upon, 'History will teach us nothing'. At the risk of contradicting a one-time schoolteacher, I believe the reverse is true for regenerative medicine. In fact, I think we dismiss the past at our peril. In this review, I aim to trace the history of regenerative medicine to date. I will examine parallels with other areas of medicine and show how commercial, technical and socio/economic factors have influenced the pace and direction of the sector's evolution. I will discuss how, by learning from the past, those involved in regenerative medicine are reinventing their sector for the better. In conclusion, I will evaluate the current state of the industry, suggest what the future may hold and explain why I believe regenerative medicine is about to 'come of age'.

Sensitivity and specificity of dopamine transporter imaging with 123I-FP-CIT SPECT in dementia with Lewy bodies: a phase III, multicentre study

BACKGROUND

Dementia with Lewy bodies (DLB) needs to be distinguished from other types of dementia because of important differences in patient management and outcome. Current clinically based diagnostic criteria for DLB have limited accuracy. Severe nigrostriatal dopaminergic degeneration occurs in DLB, but not in Alzheimer's disease or most other dementia subtypes, offering a potential system for a biological diagnostic marker. The primary aim of this study was to investigate the sensitivity and specificity, in the ante-mortem differentiation of probable DLB from other causes of dementia, of single photon emission computed tomography (SPECT) brain imaging with the ligand (123)I-2beta-carbometoxy-3beta-(4-iodophenyl)-N-(3-fluoropropyl) nortropane ((123)I-FP-CIT), which binds to the dopamine transporter (DAT) reuptake site. Diagnostic accuracy, positive and negative predictive values, and inter-reader agreement were the secondary endpoints and a subgroup of possible DLB patients was also included.

METHODS

We did a phase III study in which we used a (123)I-FP-CIT SPECT scan to assess 326 patients with clinical diagnoses of probable (n=94) or possible (n=57) DLB or non-DLB dementia (n=147) established by a consensus panel (in 28 patients no diagnosis could be made). Three readers, unaware of the clinical diagnosis, classified the images as normal or abnormal by visual inspection. The study had 90% power to detect the differences between our anticipated sensitivity (0.80) and specificity (0.85) targets and prespecified lower thresholds (sensitivity 0.65, specificity 0.73) using one-sided binomial tests with a significance level of alpha=0.025.

FINDINGS

Abnormal scans had a mean sensitivity of 77.7% for detecting clinical probable DLB, with specificity of 90.4% for excluding non-DLB dementia, which was predominantly due to Alzheimer's disease. A mean value of 85.7% was achieved for overall diagnostic accuracy, 82.4% for positive predictive value, and 87.5% for negative predictive value. Inter-reader agreement for rating scans as normal or abnormal was high (Cohen's kappa=0.87). The procedure was well tolerated with few adverse events.

INTERPRETATION

A revision of the International Consensus Criteria for DLB has recommended that low DAT uptake in the basal ganglia, as shown by SPECT or PET imaging, be a suggestive feature for diagnosis. Our findings confirm the high correlation between abnormal (low binding) DAT activity measured with (123)I-FP-CIT SPECT and a clinical diagnosis of probable DLB. The diagnostic accuracy is sufficiently high for this technique to be clinically useful in distinguishing DLB from Alzheimer's disease.

Survey of pigs' kidneys with lesions consistent with PMWS and PDNS and ochratoxicosis. Part 1: concentrations and prevalence of ochratoxin A

One thousand condemned pigs' kidneys were collected in February 2002 from two pig abattoirs in England to assess the possible contribution of ochratoxicosis to postweaning multisystemic wasting syndrome (PMWS) and porcine dermatitis and nephropathy syndrome (PDNS); 250 of the kidneys with macroscopic lesions consistent with nephrosis/nephritis (pale or white cortical lesions) were selected, and the concentration of ochratoxin A was measured in samples of renal cortex by high-performance liquid chromatography (HPLC). Low concentrations were detected in 230 (92 per cent) of the kidneys tested, and in 41 (16.4 per cent) of them the concentration was below the limit of quantification of 0.2 microg/kg. In 187 (74.8 per cent) of the kidneys, the concentration was more than 0.2 microg/kg, and the highest concentration detected was 2.3 microg/kg. The mean (sd) concentration was 0.31 (0.33) microg/kg. The identification of ochratoxin A was confirmed by mass spectrometry. The concentrations of ochratoxin A did not exceed the threshold assessed by the Food Standards Agency to be safe for human food.

Survey of pigs' kidneys with lesions consistent with PMWS and PDNS and ochratoxicosis. Part 2: pathological and histological findings

One thousand condemned pigs' kidneys were collected in February 2002 from two pig abattoirs in England to assess the lesions due to postweaning multisystemic wasting syndrome (pmws) and porcine dermatitis and nephropathy syndrome (pdns) and the possible contribution of ochratoxicosis; 174 of the kidneys were pale, 295 were swollen and 81 were abnormally firm with the gross appearance of fibrosis. The main macroscopic finding was the presence of multifocal pale cortical lesions, observed in 446 of the kidneys, and there were large cysts in 266 of them. Histopathological lesions of non-suppurative tubulointerstitial nephritis, with degeneration and fibrosis of renal tubules, were identified in 213 of 250 (85.2 per cent) of the kidneys examined. These lesions were consistent with those reported in cases of pmws and pdns. The tubular degeneration and fibrosis were also consistent with ochratoxicosis. A higher mean concentration of ochratoxin A was significantly (P=0.020) associated with the presence of multifocal pale cortical lesions consistent with ochratoxicosis, but a causal relationship was not confirmed because histochemistry was not used to detect ochratoxin in the lesions directly. There was no significant correlation between the microscopic lesions and the concentration of ochratoxin. The degenerative lesions may have been caused by previous exposure to ochratoxin that had subsequently been excreted, but the microscopic lesions also included non-suppurative interstitial nephritis, which was unlikely to have been caused by ochratoxicosis.

Cell therapy – back on the up-curve

Intercytex is an emerging healthcare company developing cell therapy products for the woundcare and aesthetic medicine markets. The company, based in Cambridge, UK, commenced operations in 2000 and has raised over £31 million in four private equity funding rounds. It is using its proprietary expertise in cell therapy to develop products that harness the innate ability of human cells to regenerate and repair the body.

Here, founder and Chief Scientific Officer of Intercytex, Dr Paul Kemp, reflects on current status and future prospects for cell therapy with Regenerative Medicine's Elisa Manzotti. Dr Kemp was formerly Vice President of Research at Organogenesis, Inc. and has more than 17 years' experience in the commercial development of cell therapy. In this interview, Dr Kemp draws attention to a cycle that so often characterizes novel medical research: initial hype, a subsequent trough of disappointment and final emergence of viable technology. He explains how cell therapy is now emerging from the trough to become a rational, real and successful component of modern medicine.

Regulated Tissue-specific Alternative Splicing of Enhanced Green Fluorescent Protein Transgenes Conferred by α-Tropomyosin Regulatory Elements in Transgenic Mice

The mutually exclusive exons 2 and 3 of alpha-tropomyosin (alphaTM) have been used as a model system for strictly regulated alternative splicing. Exon 2 inclusion is only observed at high levels in smooth muscle (SM) tissues, whereas striated muscle and non-muscle cells use predominantly exon 3. Experiments in cell culture have shown that exon 2 selection results from repression of exon 3 and that this repression is mediated by regulatory elements flanking exon 3. We have now tested the cell culture-derived model in transgenic mice. We show that by harnessing the intronic splicing regulatory elements, expression of an enhanced green fluorescent protein transgene with a constitutively active promoter can be restricted to SM cells. Splicing of both endogenous alphaTM and a series of transgenes carrying regulatory element mutations was analyzed by reverse transcriptasePCR. These studies indicated that although SM-rich tissues are equipped to regulate splicing of high levels of endogenous or transgene alphaTM RNA, other non-SM tissues such as spleen, which express lower amounts of alphaTM, also splice significant proportions of exon 2, and this splicing pattern can be recapitulated by transgenes expressed at low levels. We confirm the importance in vivo of the negatively acting regulatory elements for regulated skipping of exon 3. Moreover, we provide evidence that some of the regulatory factors responsible for exon 3 skipping appear to be titratable, with loss of regulated splicing sometimes being associated with high transgene expression levels.

Genomic Analysis of Bacteriophages SP6 and K1-5, an Estranged Subgroup of the T7 Supergroup

We have determined the genome sequences of two closely related lytic bacteriophages, SP6 and K1-5, which infect Salmonella typhimurium LT2 and Escherichia coli serotypes K1 and K5, respectively. The genome organization of these phages is almost identical with the notable exception of the tail fiber genes that confer the different host specificities. The two phages have diverged extensively at the nucleotide level but they are still more closely related to each other than either is to any other phage currently characterized. The SP6 and K1-5 genomes contain, respectively, 43,769 bp and 44,385 bp, with 174 bp and 234 bp direct terminal repeats. About half of the 105 putative open reading frames in the two genomes combined show no significant similarity to database proteins with a known or predicted function that is obviously beneficial for growth of a bacteriophage. The overall genome organization of SP6 and K1-5 is comparable to that of the T7 group of phages, although the specific order of genes coding for DNA metabolism functions has not been conserved. Low levels of nucleotide similarity between genomes in the T7 and SP6 groups suggest that they diverged a long time ago but, on the basis of this conservation of genome organization, they are expected to have retained similar developmental strategies.

A novel polypyrimidine tract-binding protein paralog expressed in smooth muscle cells

Polypyrimidine tract-binding protein (PTB) is an abundant widespread RNA-binding protein with roles in regulation of pre-mRNA alternative splicing and 3'-end processing, internal ribosomal entry site-driven translation, and mRNA localization. Tissue-restricted paralogs of PTB have previously been reported in neuronal and hematopoietic cells. These proteins are thought to replace many general functions of PTB, but to have some distinct activities, e.g. in the tissue-specific regulation of some alternative splicing events. We report the identification and characterization of a fourth rodent PTB paralog (smPTB) that is expressed at high levels in a number of smooth muscle tissues. Recombinant smPTB localized to the nucleus, bound to RNA, and was able to regulate alternative splicing. We suggest that replacement of PTB by smPTB might be important in controlling some pre-mRNA alternative splicing events.

Effects of water deficit on Mediterranean and temperate cultivars of tall fescue

Two glasshouse experiments were carried out to evaluate the morphological and physiological responses to water deficit of Mediterranean and temperate tall fescue (Festuca arundinacea Schreb.) cultivars. In Expt 1, 3 cultivars were studied: 2 temperate cultivars, Grasslands Advance (GA) and El Palenque (EP); and a Mediterranean cultivar, Maris Kasba (MK). Water deficit was induced in containers of 4 plants of a single cultivar by withholding water. In Expt 2, plants of EP and MK were grown together in the same container and received water daily with gradation in intensity of water deficit achieved by varying the daily water ration per container. All cultivars in each experiment exhibited commonly reported responses to water deficit, characterised by diminished evaporative surface area and increased root : shoot ratio. The response of MK was primarily morphological and MK plants had smaller plant size, higher root : shoot ratio, and a lower growth rate compared with temperate cultivars. By contrast, response of temperate cultivars was primarily physiological; stomatal conductance of temperate cultivars was lower and these cultivars had a greater tendency for leaf lamina osmotic adjustment than MK under the most stressful water deficit conditions studied. The morphological adaptations of MK were very effective in delaying the onset of water deficit in Expt 1 when plants were grown with others of the same cultivar, but rendered MK plants uncompetitive and more susceptible to water deficit in Expt 2 where plants of MK where interspersed with plants of a temperate cultivar.

Stretch-induced alternative splicing of serum response factor promotes bronchial myogenesis and is defective in lung hypoplasia

Smooth muscle (SM) develops only in organs and sites that sustain mechanical tensions. Therefore, we determined the role of stretch in mouse and human bronchial myogenesis. Sustained stretch induced expression of SM proteins in undifferentiated mesenchymal cells and accelerated the differentiation of cells undergoing myogenesis. Moreover, bronchial myogenesis was entirely controlled in lung organ cultures by the airway intraluminal pressure. Serum response factor (SRF) is a transcription factor critical for the induction of muscle-specific gene expression. Recently, a SRF-truncated isoform produced by alternative splicing of exon 5 has been identified (SRFDelta5). Here we show that undifferentiated mesenchymal cells synthesize both SRF and SRFDelta5 but that SRFDelta5 synthesis is suppressed during bronchial myogenesis in favor of increased SRF production. Stretch induces the same change in SRF alternative splicing, and its myogenic effect is abrogated by overexpressing SRFDelta5. Furthermore, human hypoplastic lungs related to conditions that hinder cell stretching continue to synthesize SRFDelta5 and show a marked decrease in bronchial and interstitial SM cells and their ECM product, tropoelastin. Taken together, our findings indicate that stretch plays a critical role in SM myogenesis and suggest that its decrease precludes normal bronchial muscle development.