Growth factors: the promise and the problems

Concomitants of Diabetic Foot Ulcer - A Review

BACKGROUND

Diabetes mellitus leading to foot ulcer is a serious complication, and it is considered a global epidemic. Neuropathyand high blood glucose levels are the primary causes of foot ulcers. Fifteen percent of people with diabetes develop foot ulcers, and these foot disorders are the main cause of lower extremity amputation among such patients.

INTRODUCTION

Complications of diabetic foot, affecting the lower extremities are common and quite complex and life-threatening. This review focuses on the life-threatening factors associated with diabetic foot ulcers and also the diagnosing and preventive measures. Neuropathy assessment and the range of foot ulcers were accurately examined.

CONCLUSION

Novel therapies focusing on the vascularity of the lower limbs, infection control, and ischemic control are being developed to mainly treat nonhealing ulcers.

Fibroblasts in three dimensional matrices: cell migration and matrix remodeling

Fibroblast-collagen matrix culture has facilitated the analysis of cell physiology under conditions that more closely resemble an in vivo-like environment compared to conventional 2-dimensional (2D) cell culture. Furthermore, it has led to significant progress in understanding reciprocal and adaptive interactions between fibroblasts and the collagen matrix, which occur in tissue. Recent studies on fibroblasts in 3-dimensional (3D) collagen matrices have revealed the importance of biomechanical conditions in addition to biochemical cues for cell signaling and migration. Depending on the surrounding mechanical conditions, cells utilize specific cytoskeletal proteins to adapt to their environment. More specifically, cells utilize microtubule dependent dendritic extensions to provide mechanical structure for matrix contraction under a low cell-matrix tension state, whereas cells in a high cell-matrix tension state utilize conventional acto-myosin activity for matrix remodeling. Results of collagen matrix contraction and cell migration in a 3D collagen matrix revealed that the use of appropriate growth factors led to promigratory and procontractile activity for cultured fibroblasts. Finally, the relationship between cell migration and tractional force for matrix remodeling was discussed.

The noninvasive, quantitative, in vivo assessment of adenoviral-mediated gene delivery in skin wound biomaterials

Because there are few reports using gene delivery in clinically-approved synthetic matrices, we examined the feasibility of using a noninvasive imaging system to study the kinetics of luciferase gene expression when delivered in an adenoviral vector. Using a mouse model of full thickness injury, we quantified the kinetics of gene expression, determined the optimal dose of particle delivery, and established the temporal importance of drug delivery in obtaining optimal gene expression. Specifically, we found that the ideal time to deliver adenovirus to a graft is during the early phase of graft wound closure (days 0-3 post-operatively) for a peak of gene expression to occur 7 days after delivery. Under these conditions, there is a saturating dose of 6 x 10(8) adenoviral particles per graft. In light of these findings, we examined whether the efficacy of delivery could be increased by modulating the composition of the grafts. When a collagen gene-activated matrix (GAM) containing basic fibroblast growth factor (FGF2) was compared to matrix alone, a significant increase in gene expression is observed when identical amounts of vector are delivered (p<0.05). Taken together, these results show how a noninvasive and quantitative assessment of gene expression can be used to optimize gene delivery and that the composition of matrices can dramatically influence gene expression in the wound bed.

Arginine metabolites in wound fluids from pressure ulcers: a pilot study

Compelling evidence suggests that nitric oxide (NO*), a metabolite of arginine, plays an important role in wound healing. Arginine is a semi-essential amino acid that is metabolized by nitric oxide synthase and arginase. One model for wound-healing regulation suggests the importance of strict reciprocal control of these enzymes in wounds. The purpose of this pilot study was to investigate arginine metabolism in wound fluids from patients with Stage III or IV pressure ulcers receiving negative pressure wound therapy (NPWT). Wound fluids were collected from 8 patients, aged 31-79 years, before and after initiation of NPWT on Days 1, 3, and 7. Wound fluids were analyzed for nitrates/nitrites (NOx), arginine, citrulline, proline, and ornithine. There were no significant differences between NOx, arginine, citrulline, proline, and ornithine concentrations before and after initiation of NPWT among the various timepoints. However, we observed a downward trend of NO* levels from baseline to Day 7 of NPWT treatment. Furthermore, we detected a decrease in arginine levels over the study period, suggesting that the iNOS/citrulline pathway predominated during the first 72 hr of treatment, and the arginase/ ornithine pathway dominated thereafter. Arginine and its metabolites are detectable in wound fluids from patients with Stage III or IV pressure ulcers on NPWT. Further studies on chronic wounds are warranted to correlate wound-healing outcomes with arginine metabolites at the cellular and molecular level over a longer period of time.

Distinguishing fibroblast promigratory and procontractile growth factor environments in 3-D collagen matrices

Understanding growth factor function during wound repair is necessary for the development of therapeutic interventions to improve healing outcomes. In the current study, we compare the effects of serum and purified growth factors on human fibroblast function in three different collagen matrix models: cell migration in nested matrices, floating matrix contraction, and stressed-released matrix contraction. The results of these studies indicate that platelet-derived growth factor (PDGF) is unique in its capacity to promote cell migration. Serum, lysophosphatidic acid, sphingosine-1-phophate (S1P), and endothelin-1 promote stressed-released matrix contraction but not cell migration. In addition, we found that S1P inhibits fibroblast migration and treatment of serum to remove lipid growth factors or treatment of cells to interfere with S1P(2) receptor function increases serum promigratory activity. Our findings suggest that different sets of growth factors generate promigratory and procontractile tissue environments for fibroblasts and that the balance between PDGF and S1P is a key determinant of fibroblast promigratory activity.