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Jeffrey M Davidson

Publications and source records attributed to Jeffrey M Davidson.

27 records · Page 2Linked to original sources
PubMed2002

Maximizing the in vivo efficiency of gene transfer by means of nonviral polymeric gene delivery vehicles.

We have screened many synthetic and natural polymers for their ability to facilitate gene delivery in vivo into subcutaneous tissue. We postulated that gene delivery polymeric vehicles could control the chemical and biological stability of plasmid as well as their colloidal and surface properties, and this may lead to enhanced gene delivery in vivo. The screening was based on reporter gene (luciferase) expression using a plasmid containing the cytomegalovirus promoter. The control of charge density of resulting particles was achieved by selecting different ratios of polymer to plasmid mass as well as polymer chemistry. As opposed to in vitro observations, only polymers that lead to negatively charged particles exhibited an in vivo activity, in opposite to in vitro case. Such polymers exhibited relatively low positive charge chemistry (or neutral charge). The most potent polymeric vehicles were members of a Tetronic polymer series (synthetic polyethylene-polypropylene block copolymers; BASF, Mount Olive, NJ) or from a noncharged polyvinylpyrrolidine formulation. Plasmid dose response and time relationships were established for some polymers. Results were applied to the redesign of particles for biolistic (gene gun) plasmid gene delivery.

Animals↗
PubMed2002

Real-time visualization of MMP-13 promoter activity in transgenic mice.

Cutaneous wound repair involves extracellular matrix degradation, cell migration, matrix resynthesis and tissue remodeling. In the rodent, transcriptional regulation of collagenase-3 (MMP-13) most likely plays a role in these processes. Therefore, we isolated and characterized a 1.76-kb 5'-flanking region of the mouse MMP-13 gene. Assay of promoter activity by transient transfection of HT1080 cells and primary mouse skin fibroblasts allowed identification of several functional regions of the 5'-flanking DNA. Expression of luciferase reporter constructs in these cells was induced by phorbol myristate acetate (PMA), but not by transforming growth factor-beta(2) (TGF-beta(2)). To study the regulation of MMP-13 in cutaneous wound healing, we generated transgenic mouse lines harboring the firefly luciferase reporter gene under control of a 660-bp mouse MMP-13 promoter which showed maximal response. MMP-13 mRNA levels in transgenic lung fibroblasts increased 1.5-2.6-fold after PMA challenge. MMP-13 promoter activity in wounds was visualized and quantified in vivo as luciferase bioluminescence. MMP-13 expression was present at day 1 and maximal at day 18 post-wounding. Luciferase activity progressed from the wound margin towards the center of the wound. In situ hybridization showed the same spatial and temporal patterns for the luciferase and endogenous MMP-13 mRNA. Both signals localized predominantly to dermal fibroblasts at the wound periphery but not to granulation tissue or to keratinocytes. These results suggested that MMP-13 participated in the wound healing of acute wounds, and it was a significant factor in long-term remodeling of wound connective tissue in rodent skin.

Animals↗
PubMed2002

A 28-day study of the effect of Coated VICRYL* Plus Antibacterial Suture (coated polyglactin 910 suture with triclosan) on wound healing in guinea pig linear incisional skin wounds.

BACKGROUND: This study evaluated the effect of coated polyglactin 910 suture with triclosan on tissue response and wound healing over a 28-day period on full-thickness linear wounds in the hairless guinea pig model. METHODS: In situ wound strength was assessed, and histopathologic effects on tissue response and wound healing were evaluated. Four (1.9 cm) full-thickness incisional wounds were created on the dorsolateral region (two left and two right, approximately 3 cm apart) in 40 Hartley male hairless guinea pigs (400-500 g). A 1.9-cm segment of suture material was implanted "length-wise" into the incision and the sites closed with simple interrupted closure with 3-0 nylon sutures. The test material was 2-0 coated polyglactin 910 suture with triclosan and the control material was 2-0 Coated VICRYL* Suture (coated polyglactin 910 suture). On days 3, 7, 14, and 28 postimplantation (n = 10/time interval), body weights were recorded, tissue specimens harvested, and bursting strength testing performed. RESULTS: There was no significant difference (P > 0.05) in bursting strength between the study groups for any of the time intervals studied. The bursting strengths (mm Hg) for the sutures with triclosan were 95.8 (day 3), 268.8 (day 7), 542.6 (day 14), and 633.8 (day 28). Both materials demonstrated comparable tissue response to implantation, and there were no significant differences (P > 0.05) observed in wound healing based on cellular response and collagen formation and orientation. CONCLUSION: Based on the in vivo biomechanical testing and histological results, no evidence of impedance to wound healing was detected.

Animals↗
PubMed2002

Absence of angiotensin II type 1 receptor in bone marrow-derived cells is detrimental in the evolution of renal fibrosis.

We examined the in vivo function of the angiotensin II type 1 receptor (Agtr1) on macrophages in renal fibrosis. Fourteen days after the induction of unilateral ureteral obstruction (UUO), wild-type mice reconstituted with marrow lacking the Agtr1 gene (Agtr1(-/-)) developed more severe interstitial fibrosis with fewer interstitial macrophages than those in mice reconstituted with Agtr1(+/+) marrow. These differences were not observed at day 5 of UUO. The expression of profibrotic genes - including TGF-beta1, alpha1(I) collagen, and alpha1(III) collagen - was substantially higher in the obstructed kidneys of mice with Agtr1(-/-) marrow than in those with Agtr1(+/+) marrow at day 14 but not at day 5 of UUO. Mice with Agtr1(-/-) marrow were characterized by reduced numbers of peripheral-blood monocytes and macrophage progenitors in bone marrow. In vivo assays revealed a significantly impaired phagocytic capability in Agtr1(-/-) macrophages. In vivo treatment of Agtr1(+/+) mice with losartan reduced phagocytic capability of Agtr1(+/+) macrophages to a level comparable to that of Agtr1(-/-) macrophages. Thus, during urinary tract obstruction, the Agtr1 on bone marrow-derived macrophages functions to preserve the renal parenchymal architecture, and this function depends in part on its modulatory effect on phagocytosis.

Animals↗
PubMedDate not supplied

Nanoparticulate system for efficient gene transfer into refractory cell targets.

A biocompatible, nanoparticulate formulation has been designed to retain, protect, and deliver adenoviral gene constructs over an extended time course. Such devices can be administered locally or systemically with low toxicity. A multipolymeric nanoparticulate system, featuring very high stability in physiologic media, was designed to allow efficient in vitro gene transfer. The efficacy of nanoparticulate delivery is effective in cell systems that are normally refractory to gene transfer, such as pancreatic islets and antigen-presenting cells. The findings suggest a nonspecific uptake system that permits adenoviral particle release within the transfected cells. A comparison with literature data revealed that our system is efficient at much lower levels (at least three orders of magnitude) of infectious viral particles.

Animals↗
PubMedDate not supplied

Noncontact laser Doppler imaging in burn depth analysis of the extremities.

The purpose of this study was to determine the accuracy and practical utility of a noncontact laser Doppler imager (PIM-II, Lisca Development AB, Linköping, Sweden) in the estimation of burn depth in the upper and lower extremities. At 48 hours after burn injury, we performed scans of 35 burns in 22 patients and obtained histological samples for burn determination with hematoxylin and eosin and vimentin immunohistochemical staining. Additionally, sequential scans and tissue specimens were obtained on 10 burns at 24, 48, and 72 hours. A statistically significant inverse relationship was noted between burn depth and the laser Doppler perfusion index. Laser Doppler perfusion index values greater than 1.3 predicted a superficial dermal burn with 95% sensitivity and 94% specificity. Superficial dermal burns exhibited increased perfusion in the early burn period. Wounds showed a progressive decline in perfusion and a progressive increase in the depth of injury during a 72-hour period. This study demonstrates the advantage and accuracy of using a noncontact laser Doppler to differentiate deep dermal from superficial partial thickness burns in the extremities.

Adolescent↗
PubMedDate not supplied

Migration inhibitory factor-related protein (MRP)8 and MRP14 are differentially expressed in free-electron laser and scalpel incisions.

Incisions made in mouse skin by scalpel or the free-electron laser heal at different rates. To identify genes that are differentially expressed in free-electron laser or scalpel wounds, we isolated total RNA from free-electron laser- or scalpel-produced incisions and normal skin at day 7 postwounding. cDNA microarray analysis identified 89 of 15,000 genes in a mouse microarray as having significantly different expression levels. Migration inhibitory factor-related protein (MRP) 14 was almost 30 times more highly expressed in scalpel wounds than in free-electron laser wounds. This result was confirmed by Northern blot analysis, which also showed that scalpel wounds expressed higher levels of MRP8, a related S100 protein that can heterodimerize with MRP14, at days 2, 7, and 14 postwounding. Free-electron laser wounds also showed elevated expression of MRP8 and MRP14 relative to normal skin. In situ hybridization showed that the patterns of MRP14 and MRP8 expression in free-electron laser and scalpel wound tissues were similar. MRP14 and MRP8 were expressed in the dermal wound margin, while a very low level of MRP14 and MRP8 expression was seen in the migrating epidermis. Dual immunofluorescence staining for MRP14 or MRP8 and macrophage (F4/80) showed that most of the wound macrophages simultaneously expressed MRP14 and MRP8. Some expression was also found in neutrophils, while neither antigen accumulated to a significant degree in the epidermis. Relatively lower MRP8 and 14 expression in free-electron laser wounds was correlated with a higher level of matrix metalloproteinase-13 expression and a reduced rate of wound healing. While the regulation of MRP8 expression in mouse may be different from human skin, we suggest that elevated expression of MRP8 and MRP14 may have a relevant therapeutic effect against inflammation in wound healing.

Animals↗
PubMedDate not supplied

Assessing laser-tissue damage with bioluminescent imaging.

Effective medical laser procedures are achieved by selecting laser parameters that minimize undesirable tissue damage. Traditionally, human subjects, animal models, and monolayer cell cultures have been used to study wound healing, tissue damage, and cellular effects of laser radiation. Each of these models has significant limitations, and consequently, a novel skin model is needed. To this end, a highly reproducible human skin model that enables noninvasive and longitudinal studies of gene expression was sought. In this study, we present an organotypic raft model (engineered skin) used in combination with bioluminescent imaging (BLI) techniques. The efficacy of the raft model was validated and characterized by investigating the role of heat shock protein 70 (hsp70) as a sensitive marker of thermal damage. The raft model consists of human cells incorporated into an extracellular matrix. The raft cultures were transfected with an adenovirus containing a murine hsp70 promoter driving transcription of luciferase. The model enables quantitative analysis of spatiotemporal expression of proteins using BLI. Thermal stress was induced on the raft cultures by means of a constant temperature water bath or with a carbon dioxide (CO2) laser (lambda=10.6 microm, 0.679 to 2.262 Wcm2, cw, unfocused Gaussian beam, omegaL=4.5 mm, 1 min exposure). The bioluminescence was monitored noninvasively with an IVIS 100 Bioluminescent Imaging System. BLI indicated that peak hsp70 expression occurs 4 to 12 h after exposure to thermal stress. A minimum irradiance of 0.679 Wcm2 activated the hsp70 response, and a higher irradiance of 2.262 Wcm2 was associated with a severe reduction in hsp70 response due to tissue ablation. Reverse transcription polymerase chain reaction demonstrated that hsp70 mRNA levels increased with prolonged heating exposures. Enzyme-linked immunosorbent protein assays confirmed that luciferase was an accurate surrogate for hsp70 intracellular protein levels. Hematoxylin and eosin stains verified the presence of the thermally denatured tissue regions. Immunohistochemical analyses confirmed that maximal hsp70 expression occurred at a depth of 150 microm. Bioluminescent microscopy was employed to corroborate these findings. These results indicate that quantitative BLI in engineered tissue equivalents provides a powerful model that enables sequential gene expression studies. Such a model can be used as a high throughput screening platform for laser-tissue interaction studies.

Animals↗