Biomolecular evaluation of cryopreserved amniotic membranes for ophthalmological use by ELISA and RT-PCR at one and eighteen months.

PURPOSE: To study the presence of certain proteins - EGF (epidermal growth factor), KGF (keratinocyte growth factor), IL-10 (interleukin 10), HGF (hepatocyte growth factor), Alpha2-macroglobulin and IL-1RA (interleukin 1 receptor antagonist) in cryopreserved amniotic membranes at 1 and 18 months and, as a secondary objective, to detect mRNA corresponding to KGF, IL-1Ra, Alpha2-macroglobulin, Fas Ligand, TGF beta (transforming growth factor beta) and Lumican by RT-PCR in membranes preserved at 1 and 18 months. MATERIAL AND METHODS: Four samples of amniotic membrane were divided into 2 groups: the first group (N=2) cryopreserved for 1 month and the second group (N=2) cryopreserved for 18 months, in order to be studied by RT-PCR and ELISA. RESULTS: RT-PCR detected KGF, IL-1Ra, Alpha2-macroglobulin, Fas Ligand, and Lumican. Of these, FAS Ligand mRNA was found in samples preserved for 1and 18 months. KGF, Lumican, and alpha2-microglobulin mRNA were found only at 1 month, and IL-1Ra mRNA was absent in both sample groups. RT-PCR for TGF-beta was inconclusive. ELISA was performed for detection and quantification of 6 proteins (EGF, KGF, IL-10, HGF, Alpha2-macroglobulin and IL-1Ra) in both amniotic membrane groups. All 6 proteins were found in all samples, with a lower concentration at 18 months compared to 1 month of preservation. CONCLUSION: This study shows that membranes cryopreserved in 50% glycerol for 18 months do retain the proteins necessary for regeneration of the corneal surface, giving these membranes their biochemical properties.

The dlt operon of Bacillus cereus is required for resistance to cationic antimicrobial peptides and for virulence in insects.

The dlt operon encodes proteins that alanylate teichoic acids, the major components of cell walls of gram-positive bacteria. This generates a net positive charge on bacterial cell walls, repulsing positively charged molecules and conferring resistance to animal and human cationic antimicrobial peptides (AMPs) in gram-positive pathogenic bacteria. AMPs damage the bacterial membrane and are the most effective components of the humoral immune response against bacteria. We investigated the role of the dlt operon in insect virulence by inactivating this operon in Bacillus cereus, which is both an opportunistic human pathogen and an insect pathogen. The Delta dlt(Bc) mutant displayed several morphological alterations but grew at a rate similar to that for the wild-type strain. This mutant was less resistant to protamine and several bacterial cationic AMPs, such as nisin, polymyxin B, and colistin, in vitro. It was also less resistant to molecules from the insect humoral immune system, lysozyme, and cationic AMP cecropin B from Spodoptera frugiperda. Delta dlt(Bc) was as pathogenic as the wild-type strain in oral infections of Galleria mellonella but much less virulent when injected into the hemocoels of G. mellonella and Spodoptera littoralis. We detected the dlt operon in three gram-negative genera: Erwinia (Erwinia carotovora), Bordetella (Bordetella pertussis, Bordetella parapertussis, and Bordetella bronchiseptica), and Photorhabdus (the entomopathogenic bacterium Photorhabdus luminescens TT01, the dlt operon of which did not restore cationic AMP resistance in Delta dlt(Bc)). We suggest that the dlt operon protects B. cereus against insect humoral immune mediators, including hemolymph cationic AMPs, and may be critical for the establishment of lethal septicemia in insects and in nosocomial infections in humans.

Overexpression of the human homologue of Drosophila patched (PTCH) in skin tumours: specificity for basal cell carcinoma.

The human homologue of the Drosophila segment polarity gene patched (PTCH) has been identified as the gene for the naevoid basal cell carcinoma (BCC) syndrome and has also been shown to be mutated in sporadic BCC. In order to elucidate the specificity of the PTCH abnormality in BCC, we examined normal skin and 12 BCC and 24 other types of tumour from Japanese patients for expression of the PTCH transcript by competitive reverse transcription-polymerase chain reaction, as mutational inactivation of PTCH leads to overexpression of the mutant transcript owing to failure of a negative feedback mechanism. We found a high level of PTCH expression in all 12 BCCs, while 23 of the other tumours and four specimens of normal skin showed no or weak expression of the gene, with the exception of one specimen from a patient with Bowen's disease which had high expression. These results indicate that the PTCH abnormality plays a critical role in the pathogenesis of BCC.

Growth arrest of immortalized human keratinocytes and suppression of telomerase activity by p21WAF1 gene expression.

Because most non-melanocytic human skin cancers have p53 mutations, it is unclear whether the aberrant growth of these cancers is simply a result of the abrogation of a p53 downstream mediator, the universal cyclin-dependent kinase inhibitor p21WAF1. To investigate the role of p21WAF1 in human skin carcinogenesis, we studied its regulation in normal and p53-mutated immortalized human keratinocytes. In proliferating human normal keratinocytes (HNK), more wild-type p53 protein (wt p53) was expressed than in growth-arrested differentiating keratinocytes. However, the function of wt p53 as a transcriptional activator of the p21WAF1 gene was suppressed in proliferating keratinocytes. In response to ultraviolet B irradiation, expression of wt p53 increased in proliferating keratinocytes, but p21WAF1 transcriptional activation was not induced. Two isoforms of mdm2 (p57 and p90), which can bind to wt p53 and negatively regulate wt p53 function, were expressed in proliferating HNK, suggesting that mdm2 may play a role in the suppression of wt p53's function in proliferating HNK. Increased expression of p21WAF1 was detected in both Ca(2+)-induced growth-arrested and differentiating HNK, in which the wt p53 expression was down regulated. This reflects the complexity of the p53/p21WAF1 pathways of cell-cycle regulation and differentiation in keratinocytes. No p21WAF1 expression was detected in human immortalized keratinocytes (HaCaT) or in two ras-transformed variants, HaCaT ras I/7 and HaCaT ras II/3, which have two p53 mutations. Retrovirus-mediated expression of p21WAF1 stopped the growth of all these cell types, but expression of wt p53 did not affect the cells' growth properties. p21WAF1 also downregulated human telomerase RNA component mRNA expression in HaCaT cells. This novel function of p21WAF1 partly explains the suppression of telomerase activity by p21WAF1 expression in HaCaT. Taken together, these results are consistent with the idea that p21WAF1 successfully inhibits the growth of non-melanocytic skin cancers, even those with alterations in p53, p21ras, retinoblastoma gene product, and telomerase activity.

Patched (ptch)-associated preferential expression of smoothened (smoh) in human basal cell carcinoma of the skin.

The discovery of specific overexpression of a gatekeeper gene, ptch, in basal cell carcinoma (BCC) led to a hypothesis that the human homologue of patched (PTCH) normally functions as a negative regulator of the signaling pathway that is initiated by hedgehogs (HHs) and activated by the human homologue of smoothened (SMOH); however, no evidence for the involvement of smoh and hhs has been provided. Here, we show novel evidence that smoh is also preferentially overexpressed in BCC, together with ptch (P < 0.002), and that Sonic hh was expressed in only some BCCs. Our data, therefore, indicate that such overexpression of smoh may be associated with overexpression or mutation of PTCH and that this overexpression subsequently stimulates the PTCH/SMOH signaling pathway. In an investigation of a possible regulation of ptch and smoh, we demonstrated that expression of exogenous p21WAF1 in immortalized keratinocytes down-regulates both ptch and smoh and that the down-regulation is accompanied by growth arrest, which suggests the involvement of p21WAF1 in regulation of the PTCH/SMOH signaling pathway.