Fabrication of a nanofibrous scaffold with improved bioactivity for culture of human dermal fibroblasts for skin regeneration

Engineering dermal substitutes with electrospun nanofibres have lately been of prime importance for skin tissue regeneration. Simple electrospinning technology served to produce nanofibrous scaffolds morphologically and structurally similar to the extracellular matrix of native tissues. The nanofibrous scaffolds of poly(L-lactic acid)-co-poly(ε-caprolactone) (PLACL) and PLACL/gelatin complexes were fabricated by the electrospinning process. These nanofibres were characterized for fibre morphology, membrane porosity, wettability and chemical properties by FTIR analysis to culture human foreskin fibroblasts for skin tissue engineering. The nanofibre diameter was obtained between 282 and 761 nm for PLACL and PLACL/gelatin scaffolds; expressions of amino and carboxyl groups and porosity up to 87% were obtained for these fibres, while they also exhibited improved hydrophilic properties after plasma treatment. The results showed that fibroblasts proliferation, morphology, CMFDA dye expression and secretion of collagen were significantly increased in plasma-treated PLACL/gelatin scaffolds compared to PLACL nanofibrous scaffolds. The obtained results prove that the plasma-treated PLACL/gelatin nanofibrous scaffold is a potential biocomposite material for skin tissue regeneration.

A novel bacteriophage Tail-Associated Muralytic Enzyme (TAME) from Phage K and its development into a potent antistaphylococcal protein

BACKGROUND

Staphylococcus aureus is a major cause of nosocomial and community-acquired infections. However, the rapid emergence of antibiotic resistance limits the choice of therapeutic options for treating infections caused by this organism. Muralytic enzymes from bacteriophages have recently gained attention for their potential as antibacterial agents against antibiotic-resistant gram-positive organisms. Phage K is a polyvalent virulent phage of the Myoviridae family that is active against many Staphylococcus species.

RESULTS

We identified a phage K gene, designated orf56, as encoding the phage tail-associated muralytic enzyme (TAME). The gene product (ORF56) contains a C-terminal domain corresponding to cysteine, histidine-dependent amidohydrolase/peptidase (CHAP), which demonstrated muralytic activity on a staphylococcal cell wall substrate and was lethal to S. aureus cells. We constructed N-terminal truncated forms of ORF56 and arrived at a 16-kDa protein (Lys16) that retained antistaphylococcal activity. We then generated a chimeric gene construct encoding Lys16 and a staphylococcal cell wall-binding SH3b domain. This chimeric protein (P128) showed potent antistaphylococcal activity on global clinical isolates of S. aureus including methicillin-resistant strains. In addition, P128 was effective in decolonizing rat nares of S. aureus USA300 in an experimental model.

CONCLUSIONS

We identified a phage K gene that encodes a protein associated with the phage tail structure. The muralytic activity of the phage K TAME was localized to the C-terminal CHAP domain. This potent antistaphylococcal TAME was combined with an efficient Staphylococcus-specific cell-wall targeting domain SH3b, resulting in the chimeric protein P128. This protein shows bactericidal activity against globally prevalent antibiotic resistant clinical isolates of S. aureus and against the genus Staphylococcus in general. In vivo, P128 was efficacious against methicillin-resistant S. aureus in a rat nasal colonization model.

Lysis-deficient phages as novel therapeutic agents for controlling bacterial infection

BACKGROUND

Interest in phage therapy has grown over the past decade due to the rapid emergence of antibiotic resistance in bacterial pathogens. However, the use of bacteriophages for therapeutic purposes has raised concerns over the potential for immune response, rapid toxin release by the lytic action of phages, and difficulty in dose determination in clinical situations. A phage that kills the target cell but is incapable of host cell lysis would alleviate these concerns without compromising efficacy.

RESULTS

We developed a recombinant lysis-deficient Staphylococcus aureus phage P954, in which the endolysin gene was rendered nonfunctional by insertional inactivation. P954, a temperate phage, was lysogenized in S. aureus strain RN4220. The native endolysin gene on the prophage was replaced with an endolysin gene disrupted by the chloramphenicol acetyl transferase (cat) gene through homologous recombination using a plasmid construct. Lysogens carrying the recombinant phage were detected by growth in presence of chloramphenicol. Induction of the recombinant prophage did not result in host cell lysis, and the phage progeny were released by cell lysis with glass beads. The recombinant phage retained the endolysin-deficient genotype and formed plaques only when endolysin was supplemented. The host range of the recombinant phage was the same as that of the parent phage. To test the in vivo efficacy of the recombinant endolysin-deficient phage, immunocompromised mice were challenged with pathogenic S. aureus at a dose that results in 80% mortality (LD80). Treatment with the endolysin-deficient phage rescued mice from the fatal S. aureus infection.

CONCLUSIONS

A recombinant endolysin-deficient staphylococcal phage has been developed that is lethal to methicillin-resistant S. aureus without causing bacterial cell lysis. The phage was able to multiply in lytic mode utilizing a heterologous endolysin expressed from a plasmid in the propagation host. The recombinant phage effectively rescued mice from fatal S. aureus infection. To our knowledge this is the first report of a lysis-deficient staphylococcal phage.

Polysaccharide nanofibrous scaffolds as a model for in vitro skin tissue regeneration

Tissue engineering and nanotechnology have advanced a general strategy combining the cellular elements of living tissue with sophisticated functional biocomposites to produce living structures of sufficient size and function at a low cost for clinical relevance. Xylan, a natural polysaccharide was electrospun along with polyvinyl alcohol (PVA) to produce Xylan/PVA nanofibers for skin tissue engineering. The Xylan/PVA glutaraldehyde (Glu) vapor cross-linked nanofibers were characterized by SEM, FT-IR, tensile testing and water contact angle measurements to analyze the morphology, functional groups, mechanical properties and wettability of the fibers for skin tissue regeneration. The cell-biomaterial interactions were studied by culturing human foreskin fibroblasts on Xylan/PVA Glu vapor cross-linked and Xylan/PVA/Glu blend nanofibrous scaffolds. The observed results showed that the mechanical properties (72 %) and fibroblast proliferation significantly increased up to 23 % (P < 0.05) in 48 h Glu vapor cross-linked nanofibers compared to 24 h Glu vapor cross-linked Xylan/PVA nanofibers. The present study may prove that the natural biodegradable Xylan/PVA nanofibrous scaffolds have good potential for fibroblast adhesion, proliferation and cell matrix interactions relevant for skin tissue regeneration.

Bacteriophage-derived CHAP domain protein, P128, kills Staphylococcus cells by cleaving interpeptide cross-bridge of peptidoglycan

P128 is an anti-staphylococcal protein consisting of the Staphylococcus aureus phage-K-derived tail-associated muralytic enzyme (TAME) catalytic domain (Lys16) fused with the cell-wall-binding SH3b domain of lysostaphin. In order to understand the mechanism of action and emergence of resistance to P128, we isolated mutants of Staphylococcus spp., including meticillin-resistant Staphylococcus aureus (MRSA), resistant to P128. In addition to P128, the mutants also showed resistance to Lys16, the catalytic domain of P128. The mutants showed loss of fitness as shown by reduced rate of growth in vitro. One of the mutants tested was found to show reduced virulence in animal models of S. aureus septicaemia suggesting loss of fitness in vivo as well. Analysis of the antibiotic sensitivity pattern showed that the mutants derived from MRSA strains had become sensitive to meticillin and other β-lactams. Interestingly, the mutant cells were resistant to the lytic action of phage K, although the phage was able to adsorb to these cells. Sequencing of the femA gene of three P128-resistant mutants showed either a truncation or deletion in femA, suggesting that improper cross-bridge formation in S. aureus could be causing resistance to P128. Using glutathione S-transferase (GST) fusion peptides as substrates it was found that both P128 and Lys16 were capable of cleaving a pentaglycine sequence, suggesting that P128 might be killing S. aureus by cleaving the pentaglycine cross-bridge of peptidoglycan. Moreover, peptides corresponding to the reported cross-bridge of Staphylococcus haemolyticus (GGSGG, AGSGG), which were not cleaved by lysostaphin, were cleaved efficiently by P128. This was also reflected in high sensitivity of S. haemolyticus to P128. This showed that in spite of sharing a common mechanism of action with lysostaphin, P128 has unique properties, which allow it to act on certain lysostaphin-resistant Staphylococcus strains.

Properties and mutation studies of a bacteriophage-derived chimeric recombinant staphylolytic protein P128: Comparison to recombinant lysostaphin

P128 is a chimeric anti-staphylococcal protein having a catalytic domain from a Staphylococcus bacteriophage K tail associated structural protein and a cell wall targeting domain from the Staphylococcus bacteriocin-lysostaphin. In this study, we disclose additional properties of P128 and compared the same with lysostaphin. While lysostaphin was found to get inactivated by heat and was inactive on its parent strain S. simulans biovar staphylolyticus, P128 was thermostable and was lytic towards S. simulans biovar staphylolyticus demonstrating a difference in their mechanism of action. Selected mutation studies of the catalytic domain of P128 showed that arginine and cysteine, at 40th and 76th positions respectively, are critical for the staphylolytic activity of P128, although these amino acids are not conserved residues. In comparison to native P128, only the R40S mutant (P301) was catalytically active on zymogram gel and had a similar secondary structure, as assessed by circular dichroism analysis and in silico modeling with similar cell binding properties. Mutation of the arginine residue at 40th position of the P128 molecule caused dramatic reduction in the V_max (∆OD₆₀₀ [mg/min]) value (nearly 270 fold) and the recombinant lysostaphin also showed lesser V_max value (nearly 1.5 fold) in comparison to the unmodified P128 protein. The kinetic parameters such as apparent K_m (K_m^APP) and apparent K_cat (K_cat^APP) of the native P128 protein also showed significant differences in comparison to the values observed for P301 and lysostaphin.

Use of prophage free host for achieving homogenous population of bacteriophages: new findings

We demonstrate that the prophage status of bacteria plays a critical role in achieving homogenous population of a phage preparation. When a lytic Staphylococcus bacteriophage 44AHJD was propagated in a Staphylococcus clinical isolate, the enriched phage showed 44AHJD phage virions along with the released prophages from the baiting host. The released prophage was identified as a siphophage by transmission electron microscopy. To obtain a phage preparation free of prophages, when we carried out multiplication of the 44AHJD phage in a prophage free Staphyloccoccus aureus host namely RN4220, we were surprised not to see any phage plaques in spite of the phage exhibiting >99.9% adsorption to such cells. Since RN4220 host is devoid of restriction modification system and prophages, we hypothesized that in spite of successful infection and multiplication, the phage virions might have failed to show plaques due to its insignificant release from the cell possibly due to insufficient endolysin expressed from phage virions during phage development and assembly. Our hypothesis was confirmed when we observed plaques of 44AHJD phage in RN4220 cells where additional phage endolysin protein was supplemented via a plasmid. Endolysin protein from various types of Staphylococcus phages showed plaques of 44AHJD in RN4220 cells confirming our hypothesis. Also, we demonstrate for the first time that propagation of 44AHJD phage with endolysin supplementation in prophage free RN4220 host yields pure phage preparation.

Cloning and high-level expression of Thermus thermophilus RecA in E. coli: purification and novel use in HBV diagnostics

We studied the role of Thermus thermophilus Recombinase A (RecA) in enhancing the PCR signals of DNA viruses such as Hepatitis B virus (HBV). The RecA gene of a thermophilic eubacterial strain, T. thermophilus, was cloned and hyperexpressed in Escherichia coli. The recombinant RecA protein was purified using a single heat treatment step without the use of any chromatography steps, and the purified protein (>95%) was found to be active. The purified RecA could enhance the polymerase chain reaction (PCR) signals of HBV and improve the detection limit of the HBV diagnosis by real time PCR. The yield of recombinant RecA was ∼35mg/L, the highest yield reported for a recombinant RecA to date. RecA can be successfully employed to enhance detection sensitivity for the diagnosis of DNA viruses such as HBV, and this methodology could be particularly useful for clinical samples with HBV viral loads of less than 10IU/mL, which is interesting and novel.

Staphylococcus bacteriophage tails with bactericidal properties: new findings

The development of lytic bacteriophages as therapeutic products is an attractive alternative to antibiotics. In this study, we evaluated the potential of phage tails for lysing Gram-positive bacteria. Phage P954, a well-characterized temperate staphylococcal phage, was found to adsorb to a large number of Staphylococcus aureus clinical isolates, although it lyses only 24% of the tested isolates. However, P954 phage tails generated by interruption of phage assembly were bactericidal against all the phage-resistant isolates. Phage tail preparations were trypsin sensitive with an apparent molecular weight of over 300 kDa. PCR analysis of the P954 phage-resistant isolates indicated the integration of P954-like prophages into the host genomes. Our study demonstrates for the first time that P954 bacteriophage tails have a much broader host range than the intact phage because phage tails are not affected by superinfection immunity or vulnerable to host restriction endonucleases.

Use of coagulation factor XIII (F13) gene as an internal control for normalization of genomic DNA's for HLA typing

Genomic DNA (gDNA) obtained from whole blood samples is a critical element for genomic research and clinical diagnosis. PCR efficiencies of the targeted genes like HLA-A, -B, -C, DPB1 and DRB1 using such isolated gDNAs were variable in spite of having similar amounts of gDNA taken for PCR. We addressed such PCR variabilities by normalizing the gDNA’s using an internal control of human coagulation factor XIII that was found to be variable with all samples and did not correlate with the observed A₂₆₀ nm readings. The PCR and Q-PCR methodologies for the human coagulation factor XIII have been optimized, and the advantages of normalizing gDNA preparations based on F13 copy numbers have been discussed. This method will serve as a suitable choice to be used in laboratories and research centres, particularly when dealing with a large number of samples for the next-generation sequencing purposes, and in forensic labs with limited sample availability.

Study of immunological and inflammatory gene response in Indian cohort of COVID- 19 patients by NanoString technology

COVID- 19, which has affected millions of people across the globe as a pandemic, is caused by the SARS-Cov- 2 virus which has a case fatality rate of 2.3%. The clinical outcome of those who had mild and severe infection exhibited different responses for the treatment due to differences in the host immune system. Predicting immune response with reliable biomarkers to monitor the severity and also identifying potential biomarkers that could help the clinician in decision-making would be important and also beneficial for the management of COVID- 19 in the hospital setup. In our study, we have used the NanoString nCounter gene expression assay to investigate the molecular signalling of host to COVID- 19 infection. The nCounter gene expression assay identified 29 genes that were differentially regulated and specific to COVID- 19 infection; out of which, 9 genes (ICAM3, PTAFR, CEACAM6, GBP1, C7, STAT1, CEACAM8, IL16, HLA-DPB1) exhibited strong predictive performance to differentiate COVID- 19 infection from healthy controls (AUC ≥ 0.9). We also observed that three genes (MAP4 K1, CTLA4, and HLA-DQB1) were able to differentiate COVID- 19 from patients with flu-like symptoms. A group of 11 genes (C2, CD14, CDKN1 A, CMKLR1, CYBB, HLA-A, IFNA2, LAG3, MARCO, TLR7, and IL15) showed a dysregulation trend with onset of COVID- 19 infection and settled to normal levels by day 14 as patient recovered. The outcome of our study may help in understanding the host immune response towards COVID- 19 infection.

Novel properties of recombinant Sso7d-Taq DNA polymerase purified using aqueous two-phase extraction: Utilities of the enzyme in viral diagnosis

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Sso7d-Taq fusion protein purified using a single step of aqueous Two-Phase Extraction (ATPE) is >95% pure and is active.

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The S-Taq protein has higher thermostability and detergent tolerance over regular Taq polymerase and can be used for PCR's from direct whole blood.

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The PCR efficiency rate of S-Taq is higher than Taq polymerase and can be used to detect DNA viruses in a clinical setting efficiently.

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S-Taq can tolerate higher concentrations of magnesium ions and can be used for in-situ PCR’s.

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S-Taq can be used to carry out PCR’s of bacterial recombinants directly from the overnight culture since it is resistant to inhibition to Luria Bertani broth. This unique property of S-Taq will enable researchers to screen recombinants without the need to isolate the plasmid DNA of recombinants. This would be a huge cost savings for companies engaged in molecular biology research involving PCR’s.

Using Sso7d from Sulfolobus solfataricus as the DNA binding protein fused to Taq DNA polymerase at its amino terminus, we report the hyper-expression and a novel purification methodology of Sso7d-Taq polymerase (S-Taq) using aqueous two-phase extraction system followed by Ni-affinity chromatography. The utility of such a fusion enzyme in carrying out PCR of human genes from whole blood directly and in detecting hepatitis B virus from clinical samples is demonstrated in this article. We present data on the enhanced thermo-stability of S-Taq DNA polymerase over Taq DNA polymerase and also provide evidence of its higher stability with detergents in comparison to Taq polymerase. The purified S-Taq protein showed acceptable limits of host genomic DNA levels without the use of DNases and other DNA precipitating agents and shows promising potential for use in PCR based diagnostics, in-situ PCR’s and forensic science.

Polymeric Microneedles for Transdermal Delivery of Human Placental Tissue for the Treatment of Osteoarthritis

Biologics targeting matrix-degrading proteases, cartilage repair, and inflammation are emerging as promising approaches for osteoarthritis (OA) treatment. Recent research highlights biologic-human placental tissue (HPT) as a potential OA therapy due to its biocompatibility, abundant protein biofactors, and ability to reduce cartilage degradation by suppressing protease expression. Microneedles (MNs) are receiving growing attention for enhancing transdermal delivery of biologics as an alternative to conventional subcutaneous injections. The lyophilized human placental extract (LHP) loaded polymeric MNs are fabricated using a micromolding technique for transdermal delivery. Ex vivo release studies reveal that MNs exhibit a gradual and consistent release of LHP, indicating a sustained delivery profile. LHP-MNs are nontoxic and anti-inflammatory in nature against human skin cells and interleukin (IL-1β) induced synovial cells. Furthermore, the in vivo study shows that LHP-MNs substantially improve behavioral parameters in OA rat models and lower serum concentrations of tumor necrosis factor- α (TNF-α) and cartilage oligomeric matrix protein (COMP) biomarkers, thereby alleviating knee and ankle joint injuries. Histopathological analysis indicates that LHP-MNs significantly preserve cartilage integrity. The study results suggest that employing polymeric MNs for transdermal delivery of LHP can be a promising treatment approach for OA, with the added benefit of excellent patient compliance.

The effect of human amniotic epithelial cells on urethral stricture fibroblasts

BACKGROUND

Urethral stricture disease (USD) is effectively managed by buccal mucosa (BM) urethroplasty. Lack of adequate healthy BM has led to the use of autologous tissue-engineered BM grafts. Such grafts are costly, not easily scalable and recurrence of the stricture is still a problem. Hence, there is a requirement for cost-effective, scalable cells with innate antifibrotic properties which seem to be fulfilled by human amniotic epithelial cells (HAMECs). The effect of HAMECs on USD is unknown.

AIM

To study the effect of HAMECs-CM on human urethral stricture fibroblast (USF) cells by using in-vitro migration assay and molecular techniques.

MATERIALS AND METHODS

USF cells were derived from six patients undergoing urethroplasty. HAMECs were derived from one placenta after delivery. The effect of HAMECs-CM on USF cell migration was observed using a standard in vitro scratch assay over a period of 3 days. The effect of HAMECs-CM on the expression levels of markers alpha-smooth muscle actin (α-SMA) and tissue inhibitor of metalloproteinases (TIMP-1) in USF cells was also examined.

RESULTS

The HAMECs-CM suppressed the migration of USF cells in in vitro scratch assay. The HAMECs-CM consistently downregulated α-SMA, but not TIMP-1.

CONCLUSIONS

HAMECs have shown antifibrotic activity on USF cells in this in vitro study.

RELEVANCE FOR PATIENTS

HAMECs could serve as an alternative cell source for tissue-engineered urethroplasty.