Influence of the extracellular matrix on fibroblast responsiveness to phenytoin using in vitro wound healing models

Dynamic Tuning of Viscoelastic Hydrogels with Carbonyl Iron Microparticles Reveals the Rapid Response of Cells to Three-Dimensional Substrate Mechanics

Current methods to dynamically tune three-dimensional hydrogel mechanics require specific chemistries and substrates that make modest, slow, and often irreversible changes in their mechanical properties, exclude the use of protein-based scaffolds, or alter the hydrogel microstructure and pore size. Here, we rapidly and reversibly alter the mechanical properties of hydrogels consisting of extracellular matrix proteins and proteoglycans by adding carbonyl iron microparticles (MPs) and applying external magnetic fields. This approach drastically alters hydrogel mechanics: rheology reveals that application of a 4000 Oe magnetic field to a 5 mg/mL collagen hydrogel containing 10 wt % MPs increases the storage modulus from approximately 1.5 to 30 kPa. Cell morphology experiments show that cells embedded within these hydrogels rapidly sense the magnetically induced changes in ECM stiffness. Ca²⁺ transients are altered within seconds of stiffening or subsequent softening, and slower but still dynamic changes occur in YAP nuclear translocation in response to time-dependent application of a magnetic field. The near instantaneous change in hydrogel mechanics provides new insight into the effect of changing extracellular stiffness on both acute and chronic changes in diverse cell types embedded in protein-based scaffolds. Due to its flexibility, this method is broadly applicable to future studies interrogating cell mechanotransduction in three-dimensional substrates.

Topical Phenytoin Application in Grade I and II Diabetic Foot Ulcers: A Prospective Study

BACKGROUND

India is fast becoming world diabetes capital. Diabetic foot infections are major problems among innumerable complications associated with diabetes.

MATERIAL AND METHODS

A randomized control study was conducted to evaluate the effect of topical phenytoin on healing in diabetic foot ulcers. One hundred patients with grade I/ II diabetic foot ulcers were randomly divided into two equal groups. Patients subjected to topical phenytoin dressing were classified under study and those who underwent normal salinewound dressings were classified as control. Both the groups were compared in terms of discharge, slough, wound area reduction and duration of hospital stay.

RESULTS

Discharge and slough from wound reduced significantly by day 14 in phenytoin group and within 21 days in control group. Mean duration of hospital stay in phenytoin group was 20 days, whereas in control group, it was 26 days. This difference was statistically significant (p value <0.005,df 1).

CONCLUSION

Hence, Phenytoin proved to be useful as a topical agent in promoting healing and in controlling infections in diabetic foot ulcers.

Functional consequences of mitochondrial DNA deletions in human skin fibroblasts: increased contractile strength in collagen lattices is due to oxidative stress-induced lysyl oxidase activity

Deletions within the mitochondrial DNA (mtDNA) are thought to contribute to extrinsic skin aging. To study the translation of mtDNA deletions into functional and structural changes in the skin, we seeded human skin fibroblasts into collagen gels to generate dermal equivalents. These cells were either derived from Kearns-Sayre syndrome (KSS) patients, who constitutively carry large amounts of the UV-inducible mitochondrial common deletion, or normal human volunteers. We found that KSS fibroblasts, in comparison with normal human fibroblasts, contracted the gels faster and more strongly, an effect that was dependent on reactive oxygen species. Gene expression and Western blot analysis revealed significant upregulation of lysyl oxidase (LOX) in KSS fibroblasts. Treatment with the specific LOX inhibitor beta-aminopropionitrile decreased the contraction difference between KSS and normal human fibroblast equivalents. Also, addition of the antioxidant N-tert-butyl-alpha-phenylnitrone reduced the contraction difference by inhibiting collagen gel contraction in KSS fibroblasts, and both beta-aminopropionitrile and N-tert-butyl-alpha-phenylnitrone diminished LOX activity. These data suggest a causal relationship between mtDNA deletions, reactive oxygen species production, and increased LOX activity that leads to increased contraction of collagen gels. Accordingly, increased LOX expression was also observed in vivo in photoaged human and mouse skin. Therefore, mtDNA deletions in human fibroblasts may lead to functional and structural alterations of the skin.

Topical phenytoin suspension and normal saline in the treatment of leprosy trophic ulcers: a randomized, double‐blind, comparative study

OBJECTIVE

To evaluate and compare two strengths of topical phenytoin sodium suspension (2% and 4%) with normal saline in the healing of acute trophic ulcers in leprosy patients.

METHODS

A prospective, parallel, double-blind, randomized study was conducted in 45 leprosy inpatients with acute trophic ulcers. Patients were randomized to receive 2%, 4% or normal saline dressing on their ulcers once daily for 4 weeks. Efficacy parameters such as a reduction in the surface area of the ulcer, bacterial culture of the ulcer swab, appearance of healthy granulation tissue, cessation of ulcer discharge and overall gradation of clinical healing and safety were assessed at weekly intervals.

RESULTS

The ulcer area reduction was greater in the 2% and 4% phenytoin groups compared with the normal saline group (p<0.001). Appearance of healthy granulation tissue and cessation of ulcer discharge was also observed earlier in the two phenytoin groups. At the end of 4 weeks, 11 ulcers each had healed completely in both the 2% and 4% phenytoin groups compared with none in the control group. There were no statistical differences between the 2% and 4% phenytoin groups. No side effects were reported by any patient.

CONCLUSION

Topical phenytoin appears to be an effective, safe and cheap therapeutic option for the healing of trophic ulcers in leprosy patients.

The impact of topical phenytoin on recalcitrant neuropathic diabetic foot ulceration

OBJECTIVE

To study the impact of topical phenytoin on the healing of recalcitrant neuropathic diabetic foot ulcers in patients with no clinical evidence of ischaemia or infection, and to evaluate its antibacterial effect.

METHOD

Thirty-two patients were enrolled into the study. Topical phenytoin in the form of 2% aerosol powder was applied once daily in addition to the patient's usual treatment (weekly sharp debridement, offloading and use of a gauze dressing) for eight weeks. The primary outcome was change in ulcer area over time, measured by grid tracing. Secondary outcomes were the ability of topical phenytoin to eradicate bacterial isolates, and the occurrence of adverse events.

RESULTS

Topical phenytoin significantly improved healing of recalcitrant neuropathic diabetic foot ulcers. Baseline wound area was 319.3 + 340.4 mm2, reducing to 286.1 + 341.1 mm2 and 269.1 + 341.2 mm2 after four and eight weeks respectively. However, the overall reduction in ulcer size was only 18.3% + 27.5% and 25.7% + 38.6 % respectively. Topical phenytoin therapy over eight weeks did not eradicate any of the bacterial wound isolates (Staphylococcus spp., Proteus spp. or Pseudomonas spp.). Of the 32 patients evaluated, only eight (25%) achieved more than 50% reduction in ulcer size after eight weeks of treatment.

CONCLUSION

Topical phenytoin can enhance wound healing in recalcitrant neuropathic diabetic foot ulcers, although only one-quarter of patients achieved more than 50% reduction in ulcer size after eight weeks of therapy. Further research is needed to characterise those patients who will satisfactorily respond to such therapy.

Topical diphenylhydantoin sodium can improve healing in a diabetic incisional animal wound model

OBJECTIVE

Anecdotally, topical application of diphenylhydantoin sodium (DpH) (phenytoin) has been shown to aid wound healing. We previously reported improved healing following topical infiltration of DpH in a healthy animal wound model. This study evaluates its effect on an incisional wound model in diabetic animals.

METHOD

Twenty-five male Sprague-Dawley rats were rendered diabetic by a single intraperitoneal injection of streptozotocin. Two caudal and two cephalad wounds were made on the dorsal surface. A polyvinyl alcohol sponge was placed in a subcutaneous pocket created proximal to both cephalad wounds. Each wound was either treated topically with 10mg DpH in a 200microl carrier or an equal volume of the saline vehicle (control) on the day of wounding and days 3 and 6 post-incision. The animals were sacrificed on day 10. The breaking strength of fresh and fixed wounds was determined by tensiometry, and the hydroxyproline content was determined spectrophotometrically.

RESULTS

There was a significant overall increase in both fresh (24%) and fixed (18%) wound-breaking strength of the DpH-treated wounds when compared with the controls (p<0.05). This was associated with an increase in collagen synthesis as indicated by the increased hydroxyproline content in the DpH-infiltrated sponges when compared with the controls.

CONCLUSION

Our data suggest that topical DpH improves healing in a diabetic wound model. Topical administration of DpH has the potential to accelerate diabetic wound healing and should be evaluated in human diabetic wounds.

[Tissue engineering: a tool to understand the physiological mechanisms]

Tissue engineering is a new domain, which allows some very unique studies of many human physiological mechanisms. This technology, based on cell capacity to reproduce a three-dimensional tissue with or without the help of biomaterials, is an interesting approach to study cells in an environment quite similar to the in vivo context. This article summarizes the LOEX's (laboratory of experimental organogenesis) scientific endeavor in tissue engineering in order to better understand some physiological or pathological mechanisms. Thus wound healing, stem cells, graft vascularization and cell interactions are domains where tissue engineering has already made a significant impact.

Topical phenytoin treatment of stage II decubitus ulcers in the elderly

OBJECTIVE

To compare the healing of stage II decubitus ulcers with topically applied phenytoin sodium with two other standard topical treatment procedures in a long-term care setting; and to assess the extent of systemic absorption after topical application in the phenytoin group.

METHODS

Forty-seven nursing home patients with stage II decubitus ulcers were chosen for this study. The patients were matched for age, gender, and size and severity of wounds, and randomly assigned to each treatment group. Clinical assessment of decubitus ulcers was performed at the beginning of treatment and at each dressing change. Ulcers were examined for the presence of healthy granulation tissue, reduction in surface dimensions, and time to healing. Two phenytoin sodium plasma concentrations were to be obtained on all patients in the phenytoin group.

RESULTS

Topical phenytoin therapy resulted in a shorter time to complete healing and formation of granulation tissue when compared with DuoDerm dressings or triple antibiotic ointment applications (p < or = 0.05). The mean +/- SD time to healing in the phenytoin group was 35.3 +/- 14.3 days compared with 51.8 +/- 19.6 and 53.8 +/- 8.5 days for the DuoDerm and triple antibiotic ointment groups, respectively. Healthy granulation tissue in the phenytoin group appeared within two to seven days in all subjects. Patients in the standard treatment groups required six to 21 days to produce new granulation tissue. Serum phenytoin sodium concentrations were nondetectable. No patient withdrew from the study secondary to adverse treatment effects.

CONCLUSIONS

Both the phenytoin and standard treatment groups showed progress over the study period. However, the phenytoin group demonstrated more rapid results in all aspects of ulcer healing.

Models for use in wound healing research: a survey focusing on in vitro and in vivo adult soft tissue

Many different factors must be considered before selecting a wound healing model to use for a specific study. A wide variety of models have been developed that examine different aspects of the repair response, both in vitro and in vivo. In this review article, we focus on those systems that are most widely used for studies on adult soft tissue healing. Advantages and disadvantages of each are discussed, along with relevant background information to help guide decision-making.

An overview of the topical management of wounds

Wounds in animals are a common and frequent reason for seeking veterinary attention. The way in which wounds are managed affect the rate of healing, the time to return to normal function, the final cosmetic appearance, and hence the satisfaction of customers. The management of wounds depends on the stage of wound healing and can include irrigation, mechanical and chemical debridement, the use of antiseptics and antimicrobials, adherent and nonadherent dressings, and miscellaneous topical applications such as aloe vera, honey and live yeast cell derivative. The advantages, disadvantages and indications for initial wound management, topical applicants and dressings are discussed.

Phenytoin reduces the contraction of recessive dystrophic epidermolysis bullosa fibroblast populated collagen gels

Recessive dystrophic epidermolysis bullosa (RDEB) is a group of genetic disorders in which blistering occurs below the basement membrane, in many cases resulting in extensive scar formation, contractures and mitten deformities. Our aim was to compare quantitatively the contraction forces generated by normal and RDEB fibroblats and to investigate the effect of Phenytoin (5,5-diphenyl-2,4-imidazolidinedione, sodium salt; PHT). PHT is an anticonvulsant agent, that causes fibrosis as a side effect. This study utilised conventional untethered fibroblast populated collagen lattice contraction and a quantitative force measurement instrument, the culture force monitor (CFM). The RDEB cell lines were hypercontractile, generating 2.5 times the force of normal fibroblasts, though they appeared morphologically normal. In untethered collagen gels PHT (20 micrograms/ml) significantly reduced contraction of both normal and RDEB fibroblasts over 7 days. Pre-treatment of RDEB cells for 5 days also produced a 40% reduction in contraction as measured in the CFM. One suggested mechanism of PHT action is through inhibition of matrix metalloproteinase activity, but the similar effects of PHT and Colchicine (an inhibitor of microtubule polymerisation) in the CFM, indicate that it may act on contraction through disruption of microfilaments and changes to cell shape. These findings show that isolated RDEB fibroblasts retain the hypercontractile features of many of the patient's lesion sites and imply that local application of PHT may have a therapeutic effect in controlling contraction.

Osteogenic actions of phenytoin in human bone cells are mediated in part by TGF-beta 1

We have recently demonstrated that phenytoin, a widely used therapeutic agent for seizure disorders, has osteogenic effects in rats and in humans in vivo, and in human bone cells in vitro. The goal of the present study was to determine the mechanism of the osteogenic action of phenytoin in normal human mandible-derived bone cells. Because many osteogenic agents increased bone cell proliferation through mediation by growth factors, we tested the hypothesis that the osteogenic effects of phenytoin involved the release of a growth factor by measuring the mRNA level of several bone cell growth factors and insulin-like growth factor (IGF) binding proteins with Northern blots using specific cDNA probes. Treatment with 5-50 microM phenytoin reproducibly and markedly increased (up to 6-fold, p < 0.001) the mRNA of transforming growth factor (TGF)-beta 1, but not that of other growth factors (i.e., IGF-II, platelet-derived growth factor-A [PDGF-A], PDGF-B, and TGF-beta 2) and IGF binding proteins (i.e., IGFBP-3, -4, and -5). The stimulation was dose dependent, with an optimal dose of 10-50 microM. Maximal increase was seen after 1 h of phenytoin treatment. The release of biologically active TGF-beta activity in conditioned media was measured with the mink lung cell proliferation inhibition assay. Twenty-four hours of phenytoin treatment significantly increased the production of biologically active TGF-beta (2-fold, p < 0.05) with the optimal dose between 5-50 microM. Comparisons between the in vitro osteogenic effects of phenytoin and those of TGF-beta 1 reveal that these two agents at their respective optimal doses had similar maximal stimulatory effects on [3H]thymidine incorporation, alkaline phosphatase (ALP)-specific activity, and type I alpha-2 collagen mRNA expression in human bone cells. The stimulatory effects of phenytoin on [3H]thymidine incorporation and ALP-specific activity were completely blocked by a neutralizing anti-TGF-beta antibody. In conclusion, these findings demonstrate for the first time that at least some of the osteogenic actions of phenytoin in human bone cells could be in part mediated by TGF-beta 1.