Pseudomonas aeruginosa is a difficult-to-treat pathogen that is frequently involved with chronic wound infections. Here, we conducted a literature search of world-wide studies published between 2005 and 2022 that described the microbiological profiles of chronic wound infections. For each continent, a hierarchy of pathogens was created to define the organisms that were most frequently isolated in each region. Except for South America, P. aeruginosa was the second most common organism in each major continent, with Staphylococcus aureus being the most abundant pathogen overall. When individual countries were evaluated, P. aeruginosa was the most frequently isolated organism in several Southeast Asia nations including India and Malaysia. P. aeruginosa was less commonly isolated from diabetic foot infections in North America, Europe, and Africa in comparison to other types of chronic wound infections. Additionally, the Levine wound swab technique may be a quick and painless way to isolate P. aeruginosa from wound infections, but the isolation of P. aeruginosa does not seem to be an informative predictor of the patient’s clinical course. A multivariate risk assessment that accounts for the regional frequency of P. aeruginosa isolation may be an appropriate way to guide empiric management of chronic wound infections.

Fibroblast plays an important role in keeping heart shape and elasticity as well as maintaining normal cardiac function. The differentiation of fibroblast to myofibroblast is generally considered as an irreversible conversion which represents a critical step in pathogenesis of fibrosis. Transforming growth factor (TGF)‐β1 is a major cytokine that mediates the conversion of fibroblast to myofibroblast, defined by the overly expression of α‐smooth muscle actin (α‐SMA)‐ a biomarker of myofibroblast with little to no appearance of fibroblast specific protein 1 (FSP‐1) – a biomarker of fibroblast. The cellular and molecular mechanisms of myofibroblast differentiation from fibroblasts have been studied extensively. Reversal of myofibroblast differentiation to fibroblasts remains unclear and incompletely understood. Phorbol 12‐myristate 13 acetate (PMA) is involved in multiple cellular functions such as cell growth, differentiation, programmed cell death via protein kinase C (PKC) signaling pathways. To investigate whether PMA dedifferentiates the formed myofibroblasts, NIH 3T3 fibroblasts and human cardiac fibroblast (HCF), cultured in DMEM and fibroblast medium (FM)‐2 respectively, were induced to convert into myofibroblasts in the presence of 2 ng/ml of TGF‐β1 for 24‐ or 48‐hour incubations. Expression of α‐SMA and FSP‐1 in both cell lines was detected by using western blotting and immunofluorescence. Collagen gel contraction induced by cardiac fibroblasts was determined as well. After incubation with TGF‐β1, morphology changes in the shape and the size of NIH 3T3 and HCF cells were observed by the presence of large nuclei and cytoplasm. The levels of expression of α‐SMA were significantly increased whereas expression of FSP‐1 was reduced after 48‐hour incubation with TGF‐β1. NIH 3T3 and HCF cells were then treated with 50 ng/ml of DMSO which used as control groups and with various PMA concentrations (10 ng/ml, 50 ng/ml and 100 ng/ml) for additional 24‐ and 48‐ hour incubations. Chemiluminescence detection of Western blot confirmed the reduction in expression of α‐SMA. The shape and the size of the both cell lines were recovered under the presence of PMA. The results indicated that the reduction in expression of α‐SMA was directly proportional to the concentration of PMA. As PMA concentration increased, the expression of α‐SMA remarkably decreased. PMA also reduced TGF‐β1‐induced collagen gel contraction. These data unambiguously elucidate the reversal of myofibroblast differentiation induced by PMA. Under basic condition, TGF‐β1 induces myofibroblast conversion from fibroblast, and myofibroblast de‐differentiates back into fibroblast in the presence of PMA. Although the mechanism remains to be identified, the novel findings of this study shed light on future development of novel agents to treat fibrotic diseases. Support or Funding Information This project was supported by the Seed Grant from California Northstate University, College of Pharmacy.

Cardiac fibrosis plays an essential role in cardiac pathogenic processes that occur as a result of myocardial infarction or hypertrophic cardiomyopathy. The differentiation of cardiac fibroblasts to myofibroblasts is considered to be a critical step in the activation and progression of cardiac fibrosis. TGFβ is one of the essential molecules that promote transition of fibroblasts to myofibroblasts. Reversal of formed myofibroblasts to fibroblasts remains incompletely understood. Phorbol 12-Myristate 13-Acetate (PMA) regulates metabolism and functions of multiple cells via PKC activation mostly. To study effects of PMA on differentiation of de novo formed cardiac myofibroblasts, human cardiac fibroblasts were utilized. Human cardiac fibroblasts (HCF) cultured in fibroblast medium (FM)-2 were converted into myofibroblasts in the presence of 2 ng/mL of TGF-β1 for 48 hours. Expression of α-SMA, the biomarker of myofibroblasts, and FSP1, the biomarker of fibroblasts, was detected using Western blot and immunofluorescence. Collagen gel contraction induced by fibroblasts was determined as well. TGF-β1 increased the expression of α-SMA and reduced the expression of FSP1. Distinct cellular morphology changes in the shape and size of HCF were observed after incubation with TGF-β1 for 48 hours. To investigate effect of PMA on dedifferentiation of formed myofibroblasts, these TGF-β1-pretreated cells were divided into four groups for additional 48 hours incubation: PMA groups (10, 50, and 100 ng/mL) or DMSO (vehicle control). Both 50 and 100 ng/mL of PMA reduced the expression of α-SMA but only 100 ng/mL of PMA increased the expression of FSP1. The shape and size of cells changed after treatment with PMA. PMA also reduced TGF-β1-induced collagen gel contraction (P<0.05, compared to DMSO group). These data indicated that PMA can reverse the differentiation of de novo formed human cardiac myofibroblasts induced by TGF-β1 to fibroblasts and other unidentified type of cells. Although the mechanism of dedifferentiation remains to be identified, the novel finding of this study shed light on future development of agents to treat fibrotic diseases.

The differentiation of cardiac fibroblasts to myofibroblasts is considered to be a critical step in activation and progression of cardiac fibrosis in heart disease. TGF-β is one of the key cytokines that promotes transition of fibroblasts to myofibroblasts. Dedifferentiation of formed myofibroblasts or reversal of formed myofibroblasts to fibroblasts remains incompletely understood. Prostaglandin E2 (PGE2) has been shown to dedifferentiate human lung myofibroblasts. The role of activation of the COX-2/PGE2 pathway in dedifferentiation of cardiac myofibroblasts remains unknown. Here, we show that phorbol 12-myristate 13-acetate (PMA) but not PGE2 induces dedifferentiation of de novo adult human cardiac myofibroblasts stimulated by TGF-β1 from human cardiac fibroblasts as evidenced by reduced expression of α-smooth muscle actin (α-SMA). PMA remarkably increased endogenous levels of PGE2 in human cardiac myofibroblasts. Pretreatment of myofibroblasts with NS-398, a selective COX-2 inhibitor, and PF-04418948, a selective PGE2 receptor type 2 (EP2) antagonist, had no effect on expression of α-SMA nor abolished the dedifferentiation induced by PMA. Our results indicated that endogenous and exogenous PGE2 has no effects on dedifferentiation of cardiac myofibroblasts. PMA-induced dedifferentiation of cardiac myofibroblast is independent of activation of COX-2 and PGE2 pathway. The mechanism in PMA-induced reversal of cardiac myofibroblasts needs to be explored further.