Conversion hip arthroplasty via the direct anterior approach: pearls, pitfalls and personal experience.

OBJECTIVE: Conversion total hip arthroplasty (CTHA) through a direct anterior approach (DAA) in supine position. INDICATIONS: Failed osteosynthesis of proximal femoral fractures or failed conservative hip surgery, with hardware in situ. CONTRAINDICATIONS: Decayed general conditions, infection (peri-implant or systemic infection), need for greater trochanter reconstruction, severe proximal femur deformity. SURGICAL TECHNIQUE: Supine position. Mark DAA and expected limited incisions for hardware removal (HR) with the help of a C-arm. Use guidewire and extraction devices for HR. Perform a DAA with particular attention to a wide release of the femur. POSTOPERATIVE MANAGEMENT: Full progressive weight-bearing starting on day 1, depending on bone quality. Discharge with crutches following patient walking capability. Precautions for 6 weeks. RESULTS: In all, 27 conversion THAs through a DAA. Mean age at the time of surgery 59.8 (range 18-81) years. Mean body mass index was 23.5 (range 17-31.6). Reasons of previous surgery failures were avascular necrosis of the femoral head, posttraumatic arthritis and nonunion with or without hardware migration. Mean surgical time was 125.8 min (range 58-190 min, standard deviation [SD] 38.2 min). Mean follow-up time was 6.9 years (range 2-15, SD 5.03 years). Mean pre-Harris Hip Score (mHHs) was 24.4 (range 19-36, SD 5.4), while the mean post-mHHS was 90.3 (range 89-91, SD 0.95). Two patients required postoperative osteosynthesis for periprosthetic fractures due to falls. Overall complication rate was 10%.

Protein manipulation using single copies of short peptide tags in cultured cells and in Drosophila melanogaster.

Cellular development and function rely on highly dynamic molecular interactions among proteins distributed in all cell compartments. Analysis of these interactions has been one of the main topics in cellular and developmental research, and has been mostly achieved by the manipulation of proteins of interest (POIs) at the genetic level. Although genetic strategies have significantly contributed to our current understanding, targeting specific interactions of POIs in a time- and space-controlled manner or analysing the role of POIs in dynamic cellular processes, such as cell migration or cell division, would benefit from more-direct approaches. The recent development of specific protein binders, which can be expressed and function intracellularly, along with advancement in synthetic biology, have contributed to the creation of a new toolbox for direct protein manipulations. Here, we have selected a number of short-tag epitopes for which protein binders from different scaffolds have been generated and showed that single copies of these tags allowed efficient POI binding and manipulation in living cells. Using Drosophila, we also find that single short tags can be used for POI manipulation in vivo.

Synthesis, structure-activity relationship and trypanocidal activity of pyrazole-imidazoline and new pyrazole-tetrahydropyrimidine hybrids as promising chemotherapeutic agents for Chagas disease.

Drug therapy for Chagas disease remains a major challenge as potential candidate drugs have failed clinical trials. Currently available drugs have limited efficacy and induce serious side effects. Thus, the discovery of new drugs is urgently needed in the fight against Chagas' disease. Here, we synthesized and evaluated the biological effect of pyrazole-imidazoline (1a-i) and pyrazole-tetrahydropyrimidine (2a-i) derivatives against relevant clinical forms of Trypanosoma cruzi. The structure-activity relationship (SAR), drug-target search, physicochemical and ADMET properties of the major active compounds in vitro were also assessed in silico. Pyrazole derivatives showed no toxicity in Vero cells and also no cardiotoxicity. Phenotypic screening revealed two dichlorinated pyrazole-imidazoline derivatives (1c and 1d) with trypanocidal activity higher than that of benznidazole (Bz) against trypomastigotes; these were also the most potent compounds against intracellular amastigotes. Replacement of imidazoline with tetrahydropyrimidine in the pyrazole compounds completely abolished the trypanocidal activity of series 2(a-i) derivatives. The physicochemical and ADMET properties of the compounds predicted good permeability, good oral bioavailability, no toxicity and mutagenicity of 1c and 1d. Pyrazole nucleus had high frequency hits for cruzipain in drug-target search and structure activity relationship (SAR) analysis of pyrazole-imidazoline derivatives revealed enhanced activity when chlorine atom was inserted in meta-positions of the benzene ring. Additionally, we found evidence that both compounds (1c and 1d) have the potential to interact non-covalently with the active site of cruzipain and also inhibit the cysteine proteinase activity of T. cruzi. Collectively, the data presented here reveal pyrazole derivatives with promise for further optimization in the therapy of Chagas disease.

Clinical features and outcomes of hepatocellular carcinoma in Caucasian cirrhotic patients on long-term analogue therapy for hepatitis B.

BACKGROUND: Long-term oral nucleos(t)ide analogue (NUC) therapy in hepatitis B virus (HBV)-related compensated cirrhotics prevents clinical decompensation but not hepatocellular carcinoma (HCC) development. AIMS: To define the clinical features and outcomes of HCC in long-term NUC-treated HBV patients. METHODS: All HCCs developing between 2005 and 2016 in NUC-treated HBV patients under surveillance were studied, excluding those that occurred within the first 6 months of therapy. Clinical features of HCC, alpha faetoprotein (AFP) patterns and patients' outcome were studied. RESULTS: Seventy-six HCC patients were included. Median age was 67 (40-83) years, 84% males, 96% Caucasian, 95% HBeAg-negative, 96% with undetectable HBV DNA, 83% with normal ALT levels, and 92% with compensated cirrhosis. Median serum AFP levels were 4 (1-3615) ng/mL (>7 ng/mL in 36%). HCC was monofocal in 78%, had a median diameter of 20 (6-57) mm and was in its early stage in 92% which allowed potentially curative treatments in 78% (39% ablation, 28% surgical resection, 11% liver transplantation). Overall, a complete response was obtained in 61 (80%) patients: in 40 after a first-line treatment, in 3 after the second-line treatment, in 2 after the third-line treatment, while 16 underwent liver transplantation (8 as second line). During 45 (7-144) months after HCC diagnosis, 19 patients died, 84% from HCC progression. The median time to recurrence was 20.2 (3-53) months, and the cumulative 5-year liver-related survival was 74%. CONCLUSIONS: HCCs developing in patients under long-term NUC treatment were single, small tumours, amenable to curative therapies able to confer excellent 5-year survival rates.

In vitro functional response of human tendon cells to different dosages of low-frequency pulsed electromagnetic field.

PURPOSE: Chronic tendinopathy is a degenerative process causing pain and disability. Current treatments include biophysical therapies, such as pulsed electromagnetic fields (PEMF). The aim of this study was to compare, for the first time, the functional in vitro response of human tendon cells to different dosages of PEMF, varying in field intensity and duration and number of exposures. METHODS: Tendon cells, isolated from human semitendinosus and gracilis tendons (hTCs; n = 6), were exposed to different PEMF treatments (1.5 or 3 mT for 8 or 12 h, single or repeated treatments). Scleraxis (SCX), COL1A1, COL3A1 and vascular endothelial growth factor-A (VEGF-A) expression and cytokine production were assessed. RESULTS: None of the different dosages provoked apoptotic events. Proliferation of hTCs was enhanced by all treatments, whereas only 3 mT-PEMF treatment increased cell viability. However, the single 1.5 mT-PEMF treatment elicited the highest up-regulation of SCX, VEGF-A and COL1A1 expression, and it significantly reduced COL3A1 expression with respect to untreated cells. The treated hTCs showed a significantly higher release of IL-1ß, IL-6, IL-10 and TGF-ß. Interestingly, the repeated 1.5 mT-PEMF significantly further increased IL-10 production. CONCLUSIONS: 1.5 mT-PEMF treatment was able to give the best results in in vitro healthy human tendon cell culture. Although the clinical relevance is not direct, this investigation should be considered an attempt to clarify the effect of different PEMF protocols on tendon cells, in particular focusing on the potential applicability of this cell source for regenerative medicine purpose, both in surgical and in conservative treatment for tendon disorders.

Performance of Enhanced Liver Fibrosis test and comparison with transient elastography in the identification of liver fibrosis in patients with chronic hepatitis B infection.

Assessment of liver fibrosis is important in determining prognosis, disease progression and need for treatment in patients with chronic hepatitis B (CHB). Limitations to the use of liver biopsy in assessing fibrosis are well recognized, and noninvasive tests are being increasingly evaluated including transient elastography (TE) and serum markers such as the Enhanced Liver Fibrosis (ELF) test. We assessed performance of ELF and TE in detecting liver fibrosis with reference to liver histology in a cohort of patients with CHB (n = 182), and compared the performance of these modalities. Median age was 46 and mean AST 70 IU/L. Cirrhosis was reported in 20% of liver biopsies. Both modalities performed well in assessing fibrosis at all stages. Area under receiver operator characteristic (AUROC) curves for detecting METAVIR fibrosis stages F ≥ 1, F ≥ 2, F ≥ 3 and F4 were 0.77, 0.82, 0.80 and 0.83 for ELF and 0.86, 0.86, 0.90 and 0.95 for TE. TE performed significantly better in the assessment of severe fibrosis (AUROC 0.80 for ELF and 0.90 for TE, P < 0.01) and cirrhosis (0.83 for ELF and 0.95 for TE, P < 0.01). This study demonstrates that ELF has good performance in detection of liver fibrosis in patients with CHB, and when compared, TE performs better in detection of severe fibrosis/cirrhosis.

Polymethylmethacrylate membrane and serum free light chain removal: enhancing adsorption properties.

INTRODUCTION: Polymethylmethacrylate (PMMA) membranes can adsorb a wide variety of uremic toxins including serum free light chains (sFLC). However, limited data are available regarding the clinical use of PMMA in multiple myeloma patients and its maximum adsorption capacity in this setting. AIM: This study aimed to measure the capacity of PMMA to adsorb sFLC and identify strategies to improve its efficiency in clinical practice. METHODS: Ten patients with dialysis-dependent renal failure and high levels of sFLC were included in the study. Five patients received standard PMMA hemodialysis (HD; n = 18), while in the other 5 patients a new technique called enhanced adsorption dialysis (EAD) was used, which involves PMMA dialyzer replacement after 2 h (n = 19). In all patients, sFLC were measured at the beginning and at the end of each dialysis session to calculate the difference between start and end of treatment and the percentage removal. RESULTS: PMMA membranes reduced sFLC in both the PMMA HD and EAD groups. PMMA HD showed similar efficiency on κ and λ percentage removal (22.3 and 21.0%, respectively, n.s.) but, in contrast, had a significantly greater effect on the delta of sFLC in κ [1,555 mg/l (-511 to +6,027)] versus λ [390 mg/l (120-650)] treatments (p = 0.007). EAD treatments only partially increased percentage removal of κ sFLC (22.3-31.0%, p = 0.38), while they had a significantly great effect on λ (21.0-53.1%, p = 0.003). A positive linear correlation was found between delta sFLC and pre-HD sFLC concentrations in PMMA HD κ treatments (r = 0.68, p < 0.02) but not for λ treatments (r = 0.54, p = 0.21), while the analysis of patients receiving EAD demonstrated a strong positive correlation for both κ and λ subtypes (r = 0.81 and r = 0.85, respectively, p < 0.008). In EAD sessions, a positive linear correlation was shown between blood flow during treatment and percentage removal of sFLC (r = 0.58, p = 0.02); however, with PMMA HD such a correlation was not observed (r = 0.28, p = 0.25). CONCLUSIONS: PMMA membranes can efficiently adsorb sFLC, but the process is limited by membrane saturation and is different between κ and λ sFLC. The new EAD technique can greatly improve λ removal but only partially act on κ sFLC. Therefore, EAD should be considered a valid economic treatment option without side effects in particular subsets of patients for the removal of sFLC.

A time bomb in the thorax: the giant ascending aortic aneurysm: case report.

We report the case of a 82-year-old woman, asymptomatic, subject to chest computed tomography for trauma. Then the patient underwent surgery. Before sternotomy, femoro-femoral bypass was starter in order to decompress the aneurysm; using deep hypothermia and circulatory arrest, ascending aorta and hemiarch replacement were performed with a Dacron graft. Post-operative course was uneventful.

Combined treatment of non-small cell lung cancer with synchronous brain metastases: a single center experience.

AIM: The aim of this study was to analyze our experience with combined treatment of non-small cell lung cancer with synchronous brain metastases. METHODS: Between 1992 and 2008, 31 patients were treated by performing neurosurgery (or stereotactic radiosurgery) and lung surgery. Patients were divided into two groups according to their preoperative mediastinal work-up: group A (CT scan) and group B (FDG-PET scan). RESULTS: Twenty-six patients had one brain metastasis and five had two. Neurosurgery was performed in 10 patients, stereotactic radiosurgery in 20 and both approaches in 1. Seven patients underwent chemotherapy after cerebral procedure. Pulmonary resection was complete in 27 cases and incomplete in 4. Histological findings showed: adenocarcinoma in 19 cases, squamous cell carcinoma in 8 and large cell carcinoma in 4. All patients underwent adjuvant chemotherapy. Overall 1, 2 and 5-year survival rates were 83%, 47% and 21%, respectively. The median survival was 22 months. Univariate analysis showed a better prognosis for complete resection (P=0.008), adenocarcinomas (P=0.015), N0 disease (P=0.038), and Group B (P=0.045). Multivariate analysis showed that only the radicality of the resection (P=0.027) and Group B (P=0.047) were independent prognostic factors. CONCLUSION: Our experience confirms that selected patients with non-small cell lung cancer and synchronous brain metastases may be effectively treated by combined therapy. Complete resection, adenocarcinoma histology and N0 disease were prognostic factors. The incorporation of FDG-PET scan into the preoperative work-up may translate into a survival benefit.

Dual cut-off transient elastography to assess liver fibrosis in chronic hepatitis B: a cohort study with internal validation.

BACKGROUND: Transient elastography has gained popularity to stage liver fibrosis in chronic viral hepatitis, however, diagnostic cut-offs for severe fibrosis in chronic hepatitis B are poorly defined. AIM: To evaluate an algorithm with two distinct cut-offs for positive and negative prediction of significant fibrosis and cirrhosis in chronic hepatitis B patients. METHODS: Two cohorts of treatment-naïve patients with chronic hepatitis B (125 training and 92 validations) were consecutively and concurrently examined by percutaneous liver biopsy and transient elastography. Fibrosis was staged by Metavir (significant fibrosis = F ≥ 2; cirrhosis = F4) in ≥ 2 cm long liver tissue cores. RESULTS: A >13.1 kPa positive and a ≤ 9.4 kPa negative cut-off for cirrhosis had a >90% sensitivity and specificity, with an accuracy of 94%. The corresponding cut-offs for F ≥ 2 were >9.4 and ≤ 6.2 kPa, thus classifying 56% of patients with an overall accuracy of 90%. In the validation cohort, F4 and F ≥ 2 were predicted by the above transient elastography cut-offs with an overall accuracy >90%. In 165 patients with higher than upper limit of normal transaminase activity the dual cut-off algorithm of transient elastography was as accurate as in the 52 patients with normal alanine aminotransferase values in the prediction and exclusion of cirrhosis, only. CONCLUSIONS: A dual cut-off algorithm allowed for correctly classifying both significant fibrosis and cirrhosis in the majority of the patients with chronic hepatitis B, independent of alanine aminotransferase values, thus reducing the need for liver biopsy investigations.

Incidence of neoplastic disease following lung transplantation: a 17-year single-center experience.

OBJECTIVE: Chronic immunosuppressive therapy following solid organ transplantation has been correlated with an increased risk of posttransplantation neoplastic disease (PTND). In this study we evaluated PTND incidence and outcome at our institution over a 17-year period among patients receiving lung transplantation. MATERIALS AND METHODS: Between February 1992 and December 2008, we performed 290 lung transplantations in 280 patients, including 139 single (48% with 5 retransplantations), and 151 double lung transplantations (52% with 5 retransplantations). Among the 280 patients, 2 had undergone previous double lung transplantation in other hospitals. Follow-up of transplant recipients was performed up to December 2009. RESULTS: Forty-two patients died in the hospital, producing a cumulative early (30-day) mortality rate of 15%. Among the 238 patients discharged from the hospital who entered our follow-up program, 36 (15%) experienced PTND. The mean time between transplantation and diagnosis was 47 ± 42 months, and patients' mean age at time of diagnosis was 55 ± 14 years. Overall freedom from PTND was 97%, 84%, and 73% at 1, 5, and 10 years, respectively. PTND was considered to be the direct cause of death in 11 patients (30%). Overall survival of patients with PTND at five years (45%) did not differ from the remainder of the transplanted population (46%). However, PTND became a relevant cause of death in the long-term (>5 years) follow-up. CONCLUSION: Our experience confirms that PTND was frequently diagnosed following lung transplantation. Even if PTND did not seem to significantly affect the survival of patients undergoing lung transplantation, it may become a significant cause of death among those surviving beyond 5 years.

Mutant p53 subverts p63 control over KLF4 expression in keratinocytes.

Genetic experiments established that p63 is crucial for the development and maintenance of pluri-stratified epithelia and KLF4 for the barrier function of the skin. KLF4 is one of the factors that reprogram differentiated cells to iPS. We investigated the relationship between p63 and KLF4 using RNA interference, overexpression, chromatin immunoprecipitation and transient transfections with reporter constructs. We find that p63 directly represses KLF4 in normal keratinocytes (KCs) by binding to upstream promoter sites. Unlike p63, KLF4 levels are high in the upper layers of human skin and increase upon differentiation of KCs in vitro. In HaCaT KCs, which harbor two mutant alleles of p53, inactivation of p63 and of mutant p53 leads to KLF4 repression. p63 and p53 mutants are bound to sites in the KLF4 core promoter. Importantly, expression of the H179Y and R282Q p53 mutants in primary KCs is sufficient to activate endogenous KLF4. Finally, immunohistochemical analysis of tissue arrays confirms increased coexpression of KLF4 and mutant p53 in squamous cell carcinomas. Our data indicate that suppression of KLF4 is part of the growth-promoting strategy of p63 in the lower layers of normal epidermis, and that tumor-predisposing p53 mutations hijack p63 to a different location on the promoter, turning it into an activator of this reprogramming factor.

Risk of hepatitis B surface antigen seroreversion after allogeneic hematopoietic SCT.

Allogeneic hematopoietic SCT (HSCT) increases the risk of hepatitis B virus (HBV) reactivation in hepatitis B surface antigen (HBsAg) carriers but the incidence, risk factors and course of HBV reactivation after HSCT in HBsAg-negative/anti-hepatitis B core antigen (anti-HBc)-positive recipients are not well known. A total of 50 HBsAg-negative/anti-HBc-positive HSCT recipients with onco-hematological diseases, underwent sequential clinical and laboratory examinations, including serum HBsAg, during follow-up. Serum HBV DNA collected at HSCT was retrospectively amplified by a sensitive PCR assay. During 17 months of follow-up, six (12%) patients had seroreverted to HBsAg, 7-32 months after HSCT, with 1- and 5-year cumulative rates of 13 and 22%. HBsAg seroreversion was associated with serum HBeAg higher than 8 log10 copies per ml HBV DNA and a 1.5 to 36 fold increase of serum alanine aminotransferase leading to HBeAg-positive chronic hepatitis B in all patients. Patients with chronic onco-hematological disease and long-lasting immunosuppression following HSCT had a higher risk of HBsAg seroreversion independently of serum HBV DNA levels at HSCT. HBsAg-negative/anti-HBc-positive HSCT recipients with chronic onco-hematological disease carry a significant risk of HBsAg seroreversion and HBeAg-positive chronic hepatitis B, independently of serum levels of HBV DNA at transplantation.

C/EBPδ gene targets in human keratinocytes.

C/EBPs are a family of B-Zip transcription factors--TFs--involved in the regulation of differentiation in several tissues. The two most studied members--C/EBPα and C/EBPß--play important roles in skin homeostasis and their ablation reveals cells with stem cells signatures. Much less is known about C/EBPδ which is highly expressed in the granular layer of interfollicular epidermis and is a direct target of p63, the master regular of multilayered epithelia. We identified C/EBPδ target genes in human primary keratinocytes by ChIP on chip and profiling of cells functionally inactivated with siRNA. Categorization suggests a role in differentiation and control of cell-cycle, particularly of G2/M genes. Among positively controlled targets are numerous genes involved in barrier function. Functional inactivation of C/EBPδ as well as overexpressions of two TF targets--MafB and SOX2--affect expression of markers of keratinocyte differentiation. We performed IHC on skin tumor tissue arrays: expression of C/EBPδ is lost in Basal Cell Carcinomas, but a majority of Squamous Cell Carcinomas showed elevated levels of the protein. Our data indicate that C/EBPδ plays a role in late stages of keratinocyte differentiation.

Domino heart transplantation: long-term outcome of recipients and their living donors: single center experience.

BACKGROUND: "Domino" cardiac procedure is an effective option to increase the donor pool when heart-lung transplantation (HLT) is the only treatment for patients with terminal cardiopneumopathy. We reviewed the long-term outcomes of domino cardiac donors and recipients at our institution. METHODS: Ten of 35 patients who underwent HLT from 1991 onward served as domino cardiac donors. They included eight female and two male subjects of overall mean age of 33 years and mean weight of 55 kg. Their diagnoses were primary pulmonary hypertension (n = 6) as well as cystic fibrosis, bronchiectasis, Eisenmenger's syndrome, and bronchiolitis obliterans (n = 1 each). The domino cardiac recipients included six males and four females of overall mean age of 47 years and mean weight of 61 kg. They were affected by ischemic heart disease (n = 5), cardiomyopathy (n = 4), and valvular heart disease (n = 1). Mean pulmonary vascular resistance was 3 Wood units. The heart was used either in the orthotopic (n = 8) or in the heterotopic position (n = 2). RESULTS: The 1-, 5-, and 10-year survivals for the domino cardiac donors versus their recipients were 60%, 40%, 30% versus 90%, 70%, 60%, respectively. Five domino donors developed bronchiolitis obliterans syndrome. Among the domino recipients group, cardiac allograft vasculopathy was rare (n = 1). Common causes of late death were in the domino recipients infections in the domino donors (n = 2) and malignancies. CONCLUSIONS: Our experience suggested good long-term results of the domino procedure.

Acute respiratory distress following fine needle aspiration of thyroid nodule: case report and review of the literature.

BACKGROUND: Fine needle aspiration (FNA) is a widely used practice to assess thyroid lesions, with a low morbidity rate. Although neck hematomas following this procedure are quite common, only three cases of massive hemorrhage causing acute airways obstruction have been previously described. CASE REPORT: We report the case of a 74 years old female with acute respiratory distress following ultrasound-guided FNA for a right paraisthmic thyroid nodule. The patient was admitted to the Emergency Room (ER) 6 hours after the procedure with a large neck hematoma compressing the cervical trachea and requiring surgical decompression. Patient underwent endotracheal intubation followed by isthmectomy and evacuation of the hematoma. Extubation was made 24 hours later in the Intensive Care Unit and the patient was discharged after 48 hours uneventfully. CONCLUSIONS: Acute thyroid hemorrhage following FNA is very rare but still possible. Prompt intervention is mandatory for patients with rapidly evolving symptoms.

Management of anaplastic thyroid carcinoma spread over the trachea with mediastinal extension.

INTRODUCTION: We report a case of treatment of anaplastic thyroid carcinoma spread over the trachea with mediastinal extension. METHODS: Case report and review of the world literature concerning the treatment of anaplastic thyroid carcinoma are presented. DISCUSSION: The role of surgery in treatment of anaplastic carcinoma remains controversial. Our case we underlined two questions: the appropriateness of the surgery options with extra-thyroid spread and the better surgery approach to anaplastic thyroid carcinoma interesting the mediastinum controlling the great vessels of the neck. Even if curative resection cannot be achieved, surgical resection can immediately reduce the tumor bulk to facilitate the efficacy of post-operative radiotherapy and/or chemotherapy and to achieve a good local control to avoid the need of a subsequent palliative tracheostomy. Tumor upper mediastinal involvement made mandatory to open the sternum in order to allow a more complete resection of the macroscopic mass. The mini-sternotomy represents a valuable alternative that allows reduction in surgical trauma increasing patient's comfort. CONCLUSION: The complete resection of the tumor mass without scarifying vital structures can lead to some prolonged survival. Even if complete resection cannot be achieved, surgical resection can immediately reduce the tumour bulk and achieve good local control of the disease to avoid the palliative tracheotomy.

The p63 target HBP1 is required for skin differentiation and stratification.

Genetic experiments established that p63 is crucial for the development and maintenance of pluristratified epithelia. In the RNA interference (RNAi) screening for targets of p63 in keratinocytes, we identified the transcription factor, High Mobility Group (HMG) box protein 1 (HBP1). HBP1 is an HMG-containing repressor transiently induced during differentiation of several cell lineages. We investigated the relationship between the two factors: using RNAi, overexpression, chromatin immunoprecipitations and transient transfections with reporter constructs, we established that HBP1 is directly repressed by p63. This was further confirmed in vivo by evaluating expression in p63 knockout mice and in transgenics expressing p63 in basal keratinocytes. Consistent with these findings, expression of HBP1 increases upon differentiation of primary keratinocytes and HaCaT cells in culture, and it is higher in the upper layers of human skin. Inactivation of HBP1 by RNAi prevents differentiation of keratinocytes and stratification of organotypic skin cultures. Finally, we analyzed the keratinocyte transcriptomes after HBP1 RNAi; in addition to repression of growth-promoting genes, unexpected activation of differentiation genes was uncovered, coexisting with repression of other genes involved in epithelial cornification. Our data indicate that suppression of HBP1 is part of the growth-promoting strategy of p63 in the lower layers of epidermis and that HBP1 temporally coordinates expression of genes involved in stratification, leading to the formation of the skin barrier.

Transcriptional network of p63 in human keratinocytes.

p63 is a transcription factor required for the development and maintenance of ectodermal tissues in general, and skin keratinocytes in particular. The identification of its target genes is fundamental for understanding the complex network of gene regulation governing the development of epithelia. We report a list of almost 1000 targets derived from ChIP on chip analysis on two platforms; all genes analyzed changed in expression during differentiation of human keratinocytes. Functional annotation highlighted unexpected GO terms enrichments and confirmed that genes involved in transcriptional regulation are the most significant. A detailed analysis of these transcriptional regulators in condition of perturbed p63 levels confirmed the role of p63 in the regulatory network. Rather than a rigid master-slave hierarchical model, our data indicate that p63 connects different hubs involved in the multiple specific functions of the skin.

p63 regulates the caspase-8-FLIP apoptotic pathway in epidermis.

The transcription factor p63, member of the p53 family, is crucial for epithelial development. An RNAi screening identified the apoptotic gene Procaspase-8 as a target activated by p63. The caspase-8 inhibitor FLIP is also under p63 control. We analysed and detailed the direct transactivation through the use of RNAi, reporter assays, ChIPs, western blots, confocal studies in HaCat, as well as in primary human keratinocytes. The direct DeltaNp63 regulation of these targets was confirmed in vivo using transgenic DeltaNp63 mice under the K5 promoter, as compared with p63 knockout mice, and in vitro in normal human primary keratinocytes following UV irradiation. Lowering the steady state of p63 protein levels changes the relative ratio of FLIP isoforms, causing the activation of the expressed, inactive Procaspase-8, into the active isoform thus triggering the proapoptotic cascade. Therefore, p63 fine-tunes the Procaspase-8-FLIP pro- and antiapoptotic pathway in keratinocytes.