The effect of intravitreal bevacizumab and ranibizumab on cutaneous tensile strength during wound healing

Association of Systemic or Intravitreal Antivascular Endothelial Growth Factor (Anti-VEGF) and Impaired Wound Healing in Pediatric Patients: Collagen to the Rescue

BACKGROUND

Bevacizumab is a humanized monoclonal antibody to vascular endothelial growth factor (VEGF) that has been used as a systemic chemotherapy treatment of various malignancies in adults since 2000. It has been used for pediatric patients over the last decade. In addition, bevacizumab is used for neonatal intravitreal administration for retinopathy of prematurity, a major complication of preterm birth, characterized by incomplete and abnormal vascularization of the retina that can lead to retinal detachment and blindness without treatment.

CASES

The objective of this multiple case series is to report impaired wound healing seen in 3 adolescents and 1 premature neonate receiving bevacizumab and to propose collagen-based dermal template as a choice for the management of such wounds. The 3 adolescents were undergoing treatment of malignancies and developed wound healing complication within weeks of receiving anti-VEGF. The premature neonate experienced an extravasation and had a slow wound healing trajectory after receiving intravitreal administration of bevacizumab for retinopathy of prematurity. All wounds achieved closure following topical treatment with a collagen dermal template.

CONCLUSION

Use of bevacizumab is increasing in the pediatric population. Clinicians should be aware of compromised wound healing and higher likelihood of wound dehiscence after bevacizumab administration. We recommend waiting for at least 4 to 6 weeks between anti-VEGF administration (either systemic or vitreous) and elective surgical procedures, consistent with adult literature recommendations. If patient has an existing wound, we assert that bevacizumab should not be administered until that wound is healed. If wound healing is stalled, we recommend dermal template as a safe and effective accelerator of wound healing.

Vascular Endothelial Growth Factor and Cutaneous Scarring

Significance: The proangiogenic mediator vascular endothelial growth factor (VEGF) plays an important role in cutaneous wound repair. Most of the work on VEGF and wound healing has focused on its role in mediating angiogenesis and how this affects wound closure rates. Less is known about how VEGF affects other phases of wound healing, including scar formation. Recent Advances: Over the last 10 years, mounting evidence suggests that VEGF plays an important role in regulating scar tissue production. Multiple studies have linked high VEGF levels with scar formation in normal, hypertrophic, and keloid scars. In addition, there is experimental evidence that VEGF inhibition can reduce scar tissue deposition. Critical Issues: While there is evidence that VEGF can promote scar formation in the skin, there are several unanswered questions that remain. First, the mechanisms by which VEGF promotes scar formation have not been completely characterized. While both indirect and direct mechanisms could be involved, clear evidence for a specific mechanism is lacking. In addition, despite the availability of anti-VEGF drugs, the potential value in targeting VEGF to attenuate scar formation clinically is not yet known. Future Directions: While there are a significant number of studies examining the effects of VEGF on angiogenesis and wound closure, much less attention has been paid to the contribution of VEGF to scar tissue production. Additional studies are required to learn more about how VEGF regulates scar formation and whether VEGF inhibition could be used clinically to manage scars.

Impaired wound healing secondary to bevacizumab

Bevacizumab is a monoclonal antibody that exerts its antitumor activity by inhibiting vascular endothelial growth factor. Consequently, it suppresses endothelial cell proliferation, vascular permeability, and angiogenesis. This inhibitory effect contributes to tumour size reduction but causes wound-healing delay, specifically during the proliferative phase, in patients receiving bevacizumab. Although surgical wound-healing complications (WHC) associated with bevacizumab have been extensively reported, there is limited literature on peripheral WHC. More importantly, the histopathology of bevacizumab-associated WHC has not been described. We present the histopathology findings of a non-healing ulcer in a patient receiving bevacizumab, providing insight into the possible aetiology of this drug's adverse reaction. Furthermore, our patient's positive response to hyperbaric oxygen suggests its possible use for treatment of bevacizumab-associated non-healing wounds.

The mechanical fingerprint of murine excisional wounds

A multiscale mechanics approach to the characterization of murine excisional wounds subjected to uniaxial tensile loading is presented. Local strain analysis at a physiological level of tension uncovers the presence of two distinct regions within the wound: i) a very compliant peripheral cushion and ii) a core area undergoing modest deformation. Microstructural visualizations of stretched wound specimens show negligible engagement of the collagen located in the center of a 7-day old wound; fibers remain coiled despite the applied tension, confirming the existence of a mechanically isolated wound core. The compliant cushion located at the wound periphery appears to protect the newly-formed tissue from excessive deformation during the phase of new tissue formation. The early remodeling phase (day 14) is characterized by a restored mechanical connection between far field and wound center. The latter remains less deformable, a characteristic possibly required for cell activities during tissue remodeling. The distribution of fibrillary collagens at these two time points corresponds well to the identified heterogeneity of mechanical properties of the wound region. This novel approach provides new insight into the mechanical properties of wounded skin and will be applicable to the analysis of compound-treated wounds or wounds in genetically modified tissue.

STATEMENT OF SIGNIFICANCE

Biophysical characterization of healing wounds is crucial to assess the recovery of the skin barrier function and the associated mechanobiological processes. For the first time, we performed highly resolved local deformation analysis to identify mechanical characteristics of the wound and its periphery. Our results reveal the presence of a compliant cushion surrounding a stiffer wound core; we refer to this heterogeneous mechanical behavior as "mechanical fingerprint" of the wound. The mechanical response is shown to progress towards that of the intact skin as healing takes place. Histology and multiphoton microscopy suggest that wounded skin recovers its mechanical function via progressive reconnection of the newly-deposited collagen fibers with the surrounding intact matrix.

Keratoacanthoma of the Nasal Septum Secondary to Ranibizumab Use

Keratoacanthoma (KA) is a benign epithelial tumor that typically presents as a firm, cone-shaped, flesh-colored nodule with a central horn-filled crater. KA is considered to be a low-grade variant of squamous cell carcinoma (SCC). We report a rare case of a 72-year-old male who presented with a KA involving the nasal septum, possibly related to ranibizumab use. A flesh-colored lesion on the right anterior nasal septum lesion was visualized on examination. Histologic examination revealed a well-circumscribed, dome-shaped central crater filled with keratin, well-differentiated squamous epithelium with ground-glass cytoplasm with pushing margins, and intraepithelial microabscesses establishing the diagnosis of KA. KA of the nasal septum has only been reported once in the literature. This case is unusual because it normally presents on sun-exposed areas. Additionally, this patient was taking ranibizumab, a vascular endothelial growth factor (VEGF) inhibitor for macular degeneration. Despite ranibizumab not being directly linked to precancerous and cancerous skin lesions, agents in this medication class have been. Although it is difficult to prove associations in this isolated case, the role of ranibizumab causing cutaneous lesions should be further investigated.

Effects of intravitreal ranibizumab on the untreated eye and systemic gene expression profile in age-related macular degeneration

The purpose of this study was to evaluate the systemic effects of intravitreal ranibizumab (Lucentis) treatment in patients with neovascular age-related macular degeneration (AMD). The impact of intravitreal ranibizumab injections on central retinal thickness (CRT) of treated and contralateral untreated eyes, and differences in gene expression patterns in the peripheral blood mononuclear cells were analyzed. The study included 29 patients aged 50 years old and over with diagnosed neovascular AMD. The treatment was defined as 0.5 mg of ranibizumab injected intravitreally in the form of one injection every month during the period of 3 months. CRT was measured by optical coherence tomography. The gene expression profile was assigned using oligonucleotide microarrays of Affymetrix HG-U133A. Studies have shown that there was a change of CRT between treated and untreated eyes, and there were differences in CRT at baseline and after 1, 2, and 3 months of ranibizumab treatment. Three months after intravitreal injection, mean CRT was reduced in the treated eyes from 331.97±123.62 to 254.31±58.75 μm, while mean CRT in the untreated fellow eyes reduced from 251.07±40.29 to 235.45±36.21 μm at the same time. Furthermore, the research has shown that among all transcripts, 3,097 expresses change after the ranibizumab treatment in relation to controls. Among these transcripts, 1,339 were up-regulated, whereas 1,758 were down-regulated. Our results show the potential systemic effects of anti-VEGF therapy for AMD. Moreover, our study indicated different gene expression in peripheral blood mononuclear cells before and after intravitreal ranibizumab treatment.

Burn Scar Biomechanics after Pressure Garment Therapy

BACKGROUND

The current standard of care for the prevention and treatment of scarring after burn injury is pressure garment therapy. Although this therapy has been used clinically for many years, controversy remains regarding its efficacy. The authors evaluated the efficacy of pressure garment therapy in a female red Duroc pig burn model in which wound depth could be tightly controlled.

METHODS

Full-thickness burn wounds were generated on female red Duroc pigs. At day 28 after burn, pressure garment therapy was applied to half the wounds (10 mmHg), with control wounds covered with garments that exerted no compression. Scar area, perfusion, hardness, and elasticity were quantified at days 0, 28, 42, 56, and 72 using computerized planimetry, laser Doppler, and torsional ballistometry. Scar morphology was assessed at days 28, 56, and 76 using histology, immunohistochemistry, and transmission electron microscopy.

RESULTS

Pressure garment therapy significantly hindered scar contraction, with control scars contracting to 64.6 percent + 13.9 percent original area at day 72, whereas pressure garment therapy scars contracted to 82.7 percent + 17.9 percent original area. Pressure garments significantly reduced skin hardness and increased skin strength by 1.3 times. No difference in perfusion or blood vessel density was observed. The average collagen fiber diameter was greater in control burns than in pressure garment therapy.

CONCLUSIONS

Pressure garment therapy was effective at reducing scar contraction and improving biomechanics compared with control scars. These results confirm the efficacy of pressure garments and highlight the need to further investigate the role of pressure magnitude and the time of therapy application to enhance efficacy for optimal biomechanics and patient mobility.

Complications of intravitreal injections in patients with diabetes

Intravitreal injections for the treatment of retinal disorders and intraocular infection have become a common ophthalmic procedure, and injections of anti-vascular endothelial growth factor agents or steroids are frequently performed for the treatment of diabetic macular edema or other diabetic vascular pathology. Diabetic patients may be at higher risk of adverse events than non-diabetic individuals given frequent systemic co-morbidities, such as cardiovascular and renal disease, susceptibility to infection, and unique ocular pathology that includes fibrovascular proliferation. Fortunately, many associated complications, including endophthalmitis, are related to the injection procedure and can therefore be circumvented by careful attention to injection techniques. This review highlights the safety profile of intravitreal injections in patients with diabetes. Although diabetic patients may theoretically be at higher risk than non-diabetic patients for complications, a comprehensive review of the literature does not demonstrate substantial increased risk of intravitreal injections in patients with diabetes.

High-resolution harmonics ultrasound imaging for non-invasive characterization of wound healing in a pre-clinical swine model

This work represents the first study employing non-invasive high-resolution harmonic ultrasound imaging to longitudinally characterize skin wound healing. Burn wounds (day 0-42), on the dorsum of a domestic Yorkshire white pig were studied non-invasively using tandem digital planimetry, laser speckle imaging and dual mode (B and Doppler) ultrasound imaging. Wound depth, as measured by B-mode imaging, progressively increased until day 21 and decreased thereafter. Initially, blood flow at the wound edge increased up to day 14 and subsequently regressed to baseline levels by day 21, when the wound was more than 90% closed. Coinciding with regression of blood flow at the wound edge, there was an increase in blood flow in the wound bed. This was observed to regress by day 42. Such changes in wound angiogenesis were corroborated histologically. Gated Doppler imaging quantitated the pulse pressure of the primary feeder artery supplying the wound site. This pulse pressure markedly increased with a bimodal pattern following wounding connecting it to the induction of wound angiogenesis. Finally, ultrasound elastography measured tissue stiffness and visualized growth of new tissue over time. These studies have elegantly captured the physiological sequence of events during the process of wound healing, much of which is anticipated based on certain dynamics in play, to provide the framework for future studies on molecular mechanisms driving these processes. We conclude that the tandem use of non-invasive imaging technologies has the power to provide unprecedented insight into the dynamics of the healing skin tissue.

Anti-Angiogenic Drugs: Involvement in Cutaneous Side Effects and Wound-Healing Complication

Significance: The uses of anti-angiogenic drugs have not only made an impact on the battle to eliminate cancer but are also responsible for a number of medical complications. The long-term use of these drugs has increased the spectrum and incidence of cutaneous side effects and wound-healing complications. It is, therefore, necessary to understand the overall impact that these drugs have on patient care. Recent Advances: This review highlights the role of vascular endothelial growth factor and fibroblast growth factor in angiogenesis and wound healing and looks at how angiogenic inhibitors promote wound-healing complications. Critical Issues: With an increased use of anti-angiogenic drugs for the treatment of various cancers and ocular diseases, there is an increased need for clinicians to define the risks and to optimize the usage of these drugs to reduce the incidence of cutaneous side effects and wound-healing complications. In addition, awareness is needed when treating patients on anti-angiogenic drugs so as not to exacerbate potential wound-healing complications when performing surgical procedures. Future Directions: Clinicians and surgeons will need to develop management guidelines to optimize patient care to reduce the risk of morbidity. When performing a surgical procedure, the impact of adverse effects from the use of anti-angiogenic drugs should be considered to ensure the welfare of the patient. In addition, the development of more specific inhibitors is necessary to reduce target effects to reduce the occurrence of adverse effects.

Vascular Endothelial Growth Factor and Angiogenesis in the Regulation of Cutaneous Wound Repair

Significance: Angiogenesis, the growth of new blood vessels from existing vessels, is an important aspect of the repair process. Restoration of blood flow to damaged tissues provides oxygen and nutrients required to support the growth and function of reparative cells. Vascular endothelial growth factor (VEGF) is one of the most potent proangiogenic growth factors in the skin, and the amount of VEGF present in a wound can significantly impact healing. Recent Advances: The activity of VEGF was once considered to be specific for endothelial cells lining the inside of blood vessels, partly because VEGF receptor (VEGFR) expression was believed to be restricted to endothelial cells. It is now known, however, that VEGFRs can be expressed by a variety of other cell types involved in wound repair. For example, keratinocytes and macrophages, which both carry out important functions during wound healing, express VEGFRs and are capable of responding directly to VEGF. Critical Issues: The mechanisms by which VEGF promotes angiogenesis are well established. Recent studies, however, indicate that VEGF can directly affect the activity of several nonendothelial cell types present in the skin. The implications of these extra-angiogenic effects of VEGF on wound repair are not yet known, but they suggest that this growth factor may play a more complex role during wound healing than previously believed. Future Directions: Despite the large number of studies focusing on VEGF and wound healing, it is clear that the current knowledge of how VEGF contributes to the repair of skin wounds is incomplete. Further research is needed to obtain a more comprehensive understanding of VEGF activities during the wound healing process.

Serum levels of intravitreal bevacizumab after vitrectomy, lensectomy and non-surgical controls

PURPOSE

To determine serum level differences of intravitreally-placed bevacizumab after vitrectomy and lensectomy-vitrectomy and to compare these with non-operated eyes in a rabbit model.

METHODS

Five Dutch-belted rabbits underwent pars plana vitrectomy (PPV), five rabbits underwent pars plana lensectomy (PPL) and five rabbits served as non-surgical controls. Twelve days following the surgical procedures, each operated eye underwent an intravitreal injection consisting of 1.25 mg/0.05 mL bevacizumab. Serum levels from each rabbit were drawn on days 2, 4, 7, 10, 14, 21, 28 and 35 and were measured with ELISA immunoassay.

RESULTS

The average peak serum concentration (Cmax) was highest for the PPL group (11.33 μg ± 3.48 mL), and was similar between the PPV (5.35 μg ± 2.69 mL) and non-surgical control groups (5.35 μg ± 0.69 mL). The average time to maximal plasma concentration (Tmax) in days was earliest for the PPL group (2.8 ± 0.47), followed by the PPV (5.6 ± 0.84) and non-surgical control groups (6.4 ± 0.71). The PPL group had higher serum levels than the other two groups until day 7 that was significant only at day 2 (p < 0.0001). After day 4, there were no significant differences or trends between any of the three groups. The half-life (T1/2) was fastest for the PPL group (1.41 ± 0.21 d) followed by the PPV (2.80 ± 3.35 d) and non-surgical control groups (6.69 ± 10.4 d).

CONCLUSIONS

Serum bevacizumab levels were initially elevated following lensectomy and vitrectomy compared to non-surgical eyes following intravitreal injection. The half-life of bevacizumab was prolonged in non-surgical eyes presumably due to a slower release from the vitreous cavity.