Using Becaplermin Gel with Collagen Products to Potentiate Healing in Chronic Leg Wounds

Disclosures: This study was unsupported and unsolicited. Dr. Carson is an occasional speaker for Healthpoint, Ltd., Fort Worth, Texas. This work was presented at The Wound Healing Society’s 13th Annual Educational Symposium and Exhibition, May 5, 2003, Seattle, Washington. Introduction Becaplermin gel (Regranex®, Johnson & Johnson Wound Management, Somerville, New Jersey) a genetically engineered, platelet-derived growth factor (PDGF) that mimics human PDGF, has been approved for use in diabetic lower-extremity ulcers since 1997.[1] Becaplermin also appears to be effective in nondiabetic patients with chronic wounds, and it is frequently used in these patients.[2–4] Becaplermin gel’s effect on chronic wounds is often less than stunning, often taking months to show a progression to healing in many series.[1] The cost for a 15-ounce tube varies from $350.00 to $500.00 in the authors’ area (Southern California). Early in the use of becaplermin gel on chronic wounds of the legs, the authors were thwarted by the original instructions to change the dressing every 12 hours. In this outpatient setting, many patients were unable or unwilling to cooperate with this plan. As a result, the authors noted that many wounds would dry out or become contaminated before the next visit. Consequently, the authors began to try alternate methods for application of becaplermin. The original concept in the authors’ use of collagen with becaplermin was to provide a longer-lasting, moist dressing that would protect the becaplermin gel and the wound. Extraneous collagen often derived from bovine or swine sources has been used for decades as an adjunct for wound healing.[5] Exact mechanisms of collagen’s assistance in wound healing remain to be precisely defined, but its useful effects are well known.[5] The authors felt that collagen might also potentiate the duration of effect of becaplermin by providing a slower release of becaplermin and by slowing the destruction of the becaplermin. All formulations of collagen did not appear equally effective when used in this manner, and the authors chose to use two collagen products with becaplermin gel based on preliminary trial and error. These preparations were Fibracol Plus® (collagen-alginate, Johnson & Johnson Wound Management, Somerville, New Jersey) and Oasis® (small intestinal submucosa [SIS], Healthpoint, Ltd., Fort Worth, Texas). The collagen-alginate product is a combination of 10-percent alginate and 90-percent collagen, and SIS is derived from submucosa of porcine small intestine.[6,7] As this treatment appeared efficacious in diabetic patients, the authors expanded the treatment to include nondiabetic patients as well. This was done with the provision that the patients had not responded to collagen or becaplermin gel alone and had other known factors that interfered with wound healing (e.g., ischemia, poor nutrition, pressure, and infection) corrected as much as possible. All of the patients had wound care involving maintenance debridement and moist dressings and failed to show signs of healing. In some instances, ultrasound, electrical stimulation, hyperbaric oxygen, and vacuum-assisted closure had also been used without a significant healing response. Criteria of a significant healing response were decrease in wound size, proliferation of granulation tissue, absence of heavy or foul discharge, and absence of progressive or recurring necrosis. Materials and Methods Thirty-six consecutive patients over a three-year period with wounds that failed to heal by other wound care techniques were treated simultaneously with becaplermin gel and a collagen product (18 collagen-alginate and 18 SIS). Initially, patients were treated with collagen-alginate, but as its availability diminished, SIS was used as it became more readily available. All patients gave informed consent for their specific procedures and their treatments. The use of collagen and becaplermin gel was not begun until other wound care modalities had failed to produce healing results. These included maintenance debridement and moist dressings performed on all patients, electrical stimulation performed on 10 patients, ultrasound performed on 12 patients, and vacuum-assisted closure (V.A.C.® Kinetic Concepts, Inc., San Antonio, Texas) performed on three patients. All patients had also been treated with becaplermin gel and the same collagen product used separately for at least three weeks (21–50 days, average 36 days), before combination therapy using both was tried. It was noted that in each instance the use of the collagen product separately produced little response in the wounds, but in all instances there was a slight improvement based on wound size and appearance when becaplermin gel was used. Patients were aged 40 to 78 years old with an average of 62 years. There were 16 men and 20 women. All wounds were on the hips and lower extremities including 18 foot and ankle neuropathic wounds. There were also five arterial wounds that had not healed even after corrective arterial procedures (Table 1). Also included were seven traumatic wounds, three burn wounds, and three pressure wounds. Wounds varied in size between 3cm x 2.5cm x 2.2cm (width x length x depth) to 12cm x 19cm x 1.3cm in size. Twenty-five patients were diabetic, and five had renal failure (four of these were also diabetic patients). Eight patients had been on higher doses of steroids (over 20mg prednisone a day) secondary to arthritis or respiratory problems, and six patients were on chemotherapy for cancer (no active tumor at or near the site of treatment), with one additional patient on antirejection drugs for a kidney transplant. The authors were unable to stop the prednisone altogether in any of these patients but were able to reduce all patients on steroids to 10mg/day before starting collagen and becaplermin gel combined therapy. All wounds had been present for at least 24 weeks (24–65 weeks) and had been in a wound care program for at least 14 weeks before beginning combination collagen and becaplermin gel therapy. All underlying adverse circumstances had been corrected as much as possible for at least nine weeks prior to beginning combination therapy. All pressure and neuropathic wounds were offloaded, and patients and family instructed on use of any offloading devices and footwear used. Wound care consisted of moist wound healing techniques and avoidance of prolonged cytotoxic product exposure. Maintenance debridement was used at all dressing changes when necessary while patients were in the wound care program. Collagen-alginate, SIS, and becaplermin gel were purchased commercially. Initially, becaplermin gel was applied directly to the wound based on amounts recommended by the manufacturer. SIS or collagen-alginate were then applied directly over the gel either slightly premoistened with normal saline or similarly moistened after application. A thin, nonadherent dressing (Kendall Curity®, Tyco Healthcare, Mansfield, Massachusetts) was applied when SIS was used, followed by a tape-bordered gauze dressing (Cover-Site®, Smith & Nephew, Inc., Largo, Florida). The tape-bordered gauze dressing alone was applied over the collagen-alginate. Dressings were changed every three days. At each dressing change, becaplermin was reapplied to the wound. When using collagen-alginates, the moistened fresh collagen-alginate was applied to the wound at each dressing change. SIS was replaced when it appeared not to be present in at least half the wound, and on the average, this was about every nine days. Because SIS was left in the wound for nine days, becaplermin was reapplied after the initial application and before nine days to the wound bed including what remained of the SIS. Wounds were photographed and measured at least once a week. Wounds were considered to be healed when totally epithelized. Results Twenty-four of the patients healed without further intervention over the next 29 to 90 days, and 10 more healed to the point of being able to be closed with surgical intervention (skin grafts that were successful). Two patients remained unhealed, and both were patients with renal failure and diabetes. One of these patients (using SIS) later underwent amputation of the affected limb with an occasion of severe cellulitis. This patient died four months later. The other patient (using collagen-alginate) died from complications of his renal and atherosclerotic vascular disease. Neither patient showed any significant response to the collagen product-becaplermin gel regimen at any time in the study (over 90 days). Examples of wounds are shown in Figures 1 and 2. Excluding patients receiving skin grafts for final closure, the time to heal in the two groups varied slightly between whether collagen-alginate or SIS was used as the collagen source. Patients using collagen-alginate (12 patients) healed to the point of total epithelization at an average of 50 days (range 31 to 90 days), and those using SIS (12 patients) healed at an average of 60 days (range 30–84 days). In the remaining patients (10) receiving skin grafts, five patients having used collagen-alginate and five patients having used SIS, wounds were healed to a satisfactory point at an average of 45 and 48 days before grafting, respectively. Patients going to skin graft were the larger of the wounds in this group of patients. Criteria for grafting included a healthy granular base, absence of clinical infection, filling of the defect to approximate normal skin surface, and persistence of a nonepithelized defect of at least 50 percent of original area. Discussion This group of patients is a select group who had not healed well by various modern methods of wound care. All of the patients had extensive wound bed preparation before the combined use of collagen product and becaplermin gel.[8,9] With the use of the collagen products combined with becaplermin gel, all except for two of this select group of patients with chronic wounds progressed to healing or skin graft. In the authors’ geographical area, collagen is generally purchased by the patient at a cost of $12.00 to over $100.00 per application, depending on the product used. Becaplermin gel is sold from $350.00 to over $500.00 per tube and is paid for by a surprising number of third-party payers and occasionally is covered by third-party payers in hard-to-heal, nondiabetic wounds. Becaplermin is indicated, in association with other good wound care practices, to promote granulation and the healing of full-thickness, neuropathic, chronic, diabetic ulcers.[10] Experimentally, becaplermin gel has similar effects to native PDGF. Native PDGF induces proliferation of fibroblasts, microglia, and smooth muscle.[11,12] PDGF may also serve as a chemotactic agent for inflammatory cells.[3] PDGF is also produced by a number of cell types besides platelets and is a mitogen for vascular smooth muscle cells, bone cells, cartilage cells, connective tissue cells, and some blood cells.[13] Use of the becaplermin gel intermittently as originally recommended by the manufacturer has been felt by some to be more efficacious in healing wounds as judged by its effect on cell migration and proliferation.[1,14–16] Becaplermin gel has been extensively studied in several clinical series. Becaplermin 0.01-percent gel healed about 10-percent more ulcers, after 20 weeks of treatment, than vehicle gel in a combined meta-analysis of four studies, although over 50 percent of ulcers remained unhealed.1 Adverse events reported were similar across treatment groups and included infection, skin ulceration, erythema, and pain. Becaplermin gel has also been studied with respect to its effects on healing acute wounds and chronic nondiabetic wounds.[17–19] It appears to be anywhere from slightly effective to very effective in many series.[17,18,20] These same series also show a lack of universal response to the gel and often require several months to obtain some success in healing. In the authors’ geographic area, largely because of its cost, its use has been limited to areas where other products have failed. This is understandable when reviewing papers that show only a modest improvement in wound healing, because these same papers demonstrate that the wounds may also heal when treated longer with standard, less costly methods.[1,21] In the group of patients reported here, becaplermin gel and collagen were not used as an alternate to other successful but perhaps more time-consuming methods to get these wounds to heal. These wounds were not healing with other means, and therapy was initiated to forestall the usual outcomes of nonhealing, lower-extremity wounds.[22] A variety of papers address the usefulness of collagen in healing wounds, and most reports demonstrate its effectiveness.[5,22–24] The collagen-alginate product and SIS product used in this case series have already been reported to be effective in supporting and inducing wound healing.[6,7] Classic mechanisms for collagen effectiveness are reported and presumed to be by providing a scaffold or matrix for regeneration of the host tissues, inducing host-tissue proliferation and cellular migration without provoking an immune response, providing critical components of the extracellular matrix, and, as it is broken down by the host tissues, providing structural components to drive tissue synthesis.[6,7,22–26] Recently, the provision of some cytokines by the SIS material has been postulated to contribute to the wound healing process by this form of collagen.[7] Many of these presumed effects are assumptions based upon observation and, although reasonable, have not been proven with strict scientific evidence.[5] A newer collagen product consisting of collagen-oxidized regenerated cellulose has been purported to reduce the matrix metalloprotease activity in chronic wounds and chronic wound fluid, but its efficacy for this reason has been difficult to clinically establish.[27,28] Blocking proteases, which are generally useful in wound healing but which in excessive amounts as seen in some chronic wounds appears to delay healing, would potentiate the effect of becaplermin by slowing down its inevitable destruction in the host tissue.[29,30] However, it is likely that the issue is not entirely this simple, as it is obvious that some protease activity is necessary for the induction of further endogenous cytokine production and subsequent healing in some cases.[31] It is noted that others have used living skin equivalent and becaplermin gel in a multimodal therapy to promote healing in difficult wounds and have mentioned synergism between the components, not unlike what was observed here.[32] If this is simply a use of collagen to protect against proteases, it would seem likely that most collagen products suitable to use as dressings could have similar effects. If the collagen product is also useful by providing a scaffold or matrix that provides a structural pathway as well as a chemical matrix for healing, a collagen product with a more defined matrix, such as SIS, may prove more useful.[7] It is also possible that the collagen may also induce additional receptors for growth factor activity. The addition of becaplermin gel may then provide the additional growth factor needed to attach to these receptors. The extra collagen provided and its breakdown by the proteases in these chronic wounds may have also induced an increase in the native tissue inhibitors of collagenase or an increase in other cytokines and growth factors in the wounds that would benefit healing.[27,29,30] Speculation aside, it would appear that this report provides an alternative way to use becaplermin gel with some collagen products that exert a positive effect on wound healing. This was done within the context of a wound management program and has proved useful in some of the authors’ more difficult-to-heal wounds.