Celecoxib inhibits early cutaneous wound healing.

BACKGROUND: Cyclooxygenase-2 (COX-2) is an inducible enzyme that is rapidly upregulated in response to injury, resulting in the production of prostaglandin E2 (PGE2), a primary mediator of inflammation and wound healing. The selective COX-2 inhibitor, celecoxib, is was used to treat pain and inflammation. When used to treat injuries, we postulated that loss of PGE2 activity by COX-2 inhibition would have detrimental effects on wound healing. Our objective was to study the effect of selective COX-2 inhibition with celecoxib on cutaneous wound healing. MATERIALS AND METHODS: C57BL/6J mice with uniform full-thickness wounds (1 cm(2)) to their dorsum were fed diet with or without celecoxib (1500 ppm). Wound closure analysis measured wound contraction, reepithelialization, and open wound as a percentage of the initial wound area, and was quantified by planimetry. Wounds were excised en bloc at day 7 to examine cellular proliferation, angiogenesis, cytokine production, and extracellular matrix (ECM) formation. RESULTS: Celecoxib-induced reduction in wound PGE2 levels was documented by enzyme-linked immunosorbent assay on day 7 after wounding. Wound contraction and reepithelialization were significantly reduced by celecoxib treatment, resulting in a 20% greater open wound area at day 7 (P < 0.05). In response to celecoxib treatment, immunohistochemistry analysis showed epithelial cell proliferation, angiogenesis, and ECM components including collagen and myofibroblasts were significantly decreased. CONCLUSIONS: Wound healing is significantly delayed by celecoxib treatment. These data indicate that COX-2 and its downstream product PGE2 modulate the activity of multiple essential functions of the inflammatory stroma, including epithelial proliferation, angiogenesis, and ECM production. As a result, reepithelialization and wound closure are delayed by celecoxib treatment. These findings have potential clinical implications in postoperative wound management.

Early kinetics of integration of collagen-glycosaminoglycan regenerative scaffolds in a diabetic mouse model.

BACKGROUND: Collagen-glycosaminoglycan scaffolds, originally designed to treat severe burns, are now commonly used in patients with complex wounds associated with diabetes mellitus. In this study, the authors investigated how the thickness of the scaffold would affect cellular integration with the diabetic host and whether this can be accelerated using subatmospheric pressure wound therapy devices. METHODS: Collagen-glycosaminoglycan scaffolds, 500 to 2000-µm thick, were applied to dorsal wounds in genetically diabetic mice. In addition, 1000-µm collagen-glycosaminoglycan scaffolds with and without silicone were treated with a subatmospheric pressure device (-125 mmHg). On days 5 and 10, cellular and vascular integration of tissues was studied by histology, immunohistochemistry, corrosion casting, and qRT-polymerase chain reaction. RESULTS: Cells and vessels from the wound surface populated the scaffold to form layers with varying cellular density. Areas of high cell density and proliferation were noted at the bottom of the scaffold. Increasing the thickness of the scaffold did not affect the extent of cellular ingrowth, so that thicker scaffolds had a thicker residual acellular layer on the surface. The thickness of cellular ingrowth was stable between days 5 and 10, whereas vessels seen in the scaffolds on day 10 were not yet present on day 5. Subatmospheric pressure devices applied to silicone-covered collagen-glycosaminoglycan scaffolds minimized the granulation tissue formation beneath the scaffold, which enhanced vessel ingrowth. CONCLUSIONS: The early kinetics of cellular integration into collagen-glycosaminoglycan scaffolds is independent of scaffold thickness in a diabetic wound model. Scaffold adherence to the wound and integration can be improved using a subatmospheric pressure device.

Foam pore size is a critical interface parameter of suction-based wound healing devices.

BACKGROUND: Suction-based wound healing devices with open-pore foam interfaces are widely used to treat complex tissue defects. The impact of changes in physicochemical parameters of the wound interfaces has not been investigated. METHODS: Full-thickness wounds in diabetic mice were treated with occlusive dressing or a suction device with a polyurethane foam interface varying in mean pore size diameter. Wound surface deformation on day 2 was measured on fixed tissues. Histologic cross-sections were analyzed for granulation tissue thickness (hematoxylin and eosin), myofibroblast density (α-smooth muscle actin), blood vessel density (platelet endothelial cell adhesion molecule-1), and cell proliferation (Ki67) on day 7. RESULTS: Polyurethane foam-induced wound surface deformation increased with polyurethane foam pore diameter: 15 percent (small pore size), 60 percent (medium pore size), and 150 percent (large pore size). The extent of wound strain correlated with granulation tissue thickness that increased 1.7-fold in small pore size foam-treated wounds, 2.5-fold in medium pore size foam-treated wounds, and 4.9-fold in large pore size foam-treated wounds (p < 0.05) compared with wounds treated with an occlusive dressing. All polyurethane foams increased the number of myofibroblasts over occlusive dressing, with maximal presence in large pore size foam-treated wounds compared with all other groups (p < 0.05). CONCLUSIONS: The pore size of the interface material of suction devices has a significant impact on the wound healing response. Larger pores increased wound surface strain, tissue growth, and transformation of contractile cells. Modification of the pore size is a powerful approach for meeting biological needs of specific wounds.

Mesenchymal stromal cell mutations and wound healing contribute to the etiology of desmoid tumors.

Desmoid tumors are nonmalignant neoplasms of mesenchymal origin that mainly contain fibroblast lineage cells. These tumors often occur in patients with familial adenomatous polyposis (FAP) coli who have germ line mutations in the APC gene. Given emerging data that has implicated multipotent mesencyhmal stromal cells (MSC) in the origin of mesenchymal tumors, we hypothesized that desmoid tumors may arise in patients with FAP after MSCs acquire somatic mutations during the proliferative phase of wound healing. To test this idea, we examined 16 desmoid tumors from FAP-associated and sporadic cases, finding that all 16 of 16 tumors expressed stem cell markers, whereas matching normal stromal tissues were uniformly negative. Desmoid tumors also contained a subclass of fibrocytes linked to wound healing, angiogenesis, and fibrosis. Using an MSC cell line derived from an FAP-associated desmoid tumor, we confirmed an expected loss in the expression of adenomatous polyposis coli (APC) and the transcriptional repressor BMI-1 while documenting the coexpression of markers for chondrocytes, adipocytes, and osteocytes. Together, our findings argue that desmoid tumors result from the growth of MSCs in a wound healing setting that is associated with deregulated Wnt signaling due to APC loss. The differentiation potential of these MSCs combined with expression of BMI-1, a transcriptional repressor downstream of Hedgehog and Notch signaling, suggests that desmoid tumors may respond to therapies targeting these pathways.

External volume expansion increases subcutaneous thickness, cell proliferation, and vascular remodeling in a murine model.

BACKGROUND: Fat grafting is a powerful tool for soft-tissue reconstruction; however, the science behind recipient bed preparation has not been thoroughly explored. External volume expansion using suction before fat grafting has been used clinically to improve reliability and consistency of graft survival. The authors developed a murine model to investigate the underlying mechanism of external volume expansion. METHODS: The authors created an external volume expansion device using a soft-silicone dome connected to a vacuum source (25 mmHg) to treat the dorsum of mice, and the response was compared with treatment with an occlusive dressing. Treated areas were monitored with magnetic resonance imaging. Remodeling of microvasculature was studied with corrosion casting on day 7. Effects on tissue thickness, number of adipocytes, cell proliferation, and blood vessel density were analyzed at 28 days. RESULTS: Macroscopic analysis showed tissue swelling at sites treated with the external volume expansion device by 21 days, without skin damage. On day 28, external volume expansion increased the thickness of the subcutaneous fat layer twofold, consistent with magnetic resonance imaging observations. The proliferation rate in the subcutaneous layer of expansion-treated areas increased twofold, with a net 2.2-fold increase in number of adipocytes in columns; remodeling of the vessels network occurred, with reorientation and increase of vessel diameters shown by corrosion casting and 1.9-fold augmentation of vessels density. CONCLUSIONS: External volume expansion applied to mouse integument induces highly proliferative and vascularized subcutaneous tissue. Recipient-site preparation using external volume expansion devices may be a promising tool to enhance cell and tissue engraftment.

Mast cells are required in the proliferation and remodeling phases of microdeformational wound therapy.

BACKGROUND: Mast cells are important in numerous inflammatory processes. They are also mechanosensitive and likely play an important role in wound healing. The authors hypothesized that mechanical alteration of the wound environment with a distributed suction device could link mast cells to the healing cascade. METHODS: Controlled uniform full-thickness wound surface microdeformations were induced by suction combined with an open-pore polyurethane foam (microdeformational wound therapy) in mast cell-deficient WWv mice and their mast cell-sufficient littermates. Wound healing parameters were assessed in the inflammatory, proliferative, and remodeling phases of healing. RESULTS: Wound tissue granulation, cell proliferation, blood vessel sprouting, and collagen maturation were found to be mast cell-dependent throughout the proliferating and remodeling stages of healing. CONCLUSION: Mast cells are critical in the robust granulation tissue response seen in microdeformational wound therapy and in the modulation of the remodeling phase of wound healing.