Case Report: Treatment of a Lower Leg Defect in the Course of Sarcoma With Microvascular Tissue

Nonhealing wounds affect up to 6 million people in the United States, resulting in health care expenditures exceeding $3 billion per year.^1-3 During normal wound healing, angiogenesis leads to revascularization of tissue and establishment of a functioning microcirculation to deliver oxygen and nutrients required for proper tissue repair, along with removal of waste metabolites and combating microbial burden.⁴ In chronic or delayed-healing wounds, however, this process can be severely compromised. Such problematic wounds can develop for an array of reasons, such as venous stasis, ischemia, unrelieved pressure, chemotherapy, and radiation treatment. When conventional treatments such as sharp debridement and offloading have failed, additional therapies—such as NPWT or hyperbaric oxygen chambers—have been utilized and are frequently augmented by surgical revascularization procedures.⁵ Effective chronic wound therapy can be challenging for patients with severe illnesses (eg, poorly controlled diabetes, critical limb ischemia, morbid obesity, Crohn’s disease, or cancer) or who are receiving ongoing therapies that preclude invasive interventions, due to underlying systemic disease and compromised tissue surrounding the wound.

Patient history and presentation

A 29-year-old male with poorly differentiated angiosarcoma and spindle cell sarcoma presented with a complicated left leg wound and exposure of the left tibia. The tumor had been noted for approximately 10 years prior to presentation. Seven months before presentation, the first course of aggressive chemotherapy and neoadjuvant radiotherapy was initiated, after which his malignancy was removed with appropriate margin. No evidence of osteomyelitis was present, and no prophylactic antibiotic treatment was utilized. Bone integrity was not in question; there were no indications for inflammatory marker or radiographic imaging diagnostic bone studies.^6,7 Two weeks after tumor removal (2 months prior to presentation), split-thickness skin graft reconstruction protected by NPWT was attempted; however, the graft did not take, and the thin layer of soft tissue desiccated, exposing periosteum-denuded bone. Due to the patient’s ongoing radiotherapy and immunotherapy schedule and compromised immune system, previously planned invasive flap surgery was delayed. To stabilize the enlarging wound with progressively desiccating edges, an advanced biologic (dehydrated human amnion/chorion membrane) was applied, but the wound condition did not improve. The patient’s nutritional status was monitored by oncologists with comprehensive metabolic panels reviewed every 3 to 4 weeks. The only abnormality observed was a low cortisol level on 3 different occasions, attributed to mild immunotherapy-induced adrenal insufficiency. Patient consent for the publication of case images and results was obtained.

Treatment rationale

PMVT (mVASC; MicroVascular Tissues, Inc.) is a sterile, off-the-shelf human microvascular structural tissue graft derived from a single human cadaver and consisting of arteriole, capillary, and venule extracellular matrix.^8-10 PMVT is packaged as a 19.5-mm lyophilized disk in a sealed glass vial for single-patient use, with microvessel and extracellular matrix structural elements retained in the final product (Figure 1). It is intended to facilitate the healing of full-thickness skin wounds and can be topically applied in a dry form to the surface of the wound, injected locally after reconstitution with USP sterile water at the edges of the wound, or both.

PMVT has been shown to improve blood flow in ischemic tissues (Figure 2).¹¹ PMVT’s microvascular structure may also serve as an extracellular matrix scaffold for revascularization, positioning it as a viable angioconductive option to address conditions of compromised vascularity. Considering the author’s positive prior experience with PMVT when used to repair or replace damaged or deficient microvascular tissue,¹² it was selected as a treatment in this case to repair the microvascular tissue, improve microvascular blood flow around this poorly vascularized and senescent environment, and help remodel irradiated tissue. The initial clinical objective was to arrest further deterioration and stabilize the wound while the patient continued chemotherapy and bridge the time until flap surgery could be performed.

While another noninvasive treatment option (such as local administration of insulin) could have been considered, PMVT seemed a more appropriate choice because the objective was to develop vascularized tissue versus stimulating growth of already existing granulation tissue.^13,14 NPWT was also considered for use in conjunction with PMVT but was not selected because it was imperative to seal the wound after PMVT application, so the negative pressure would not have been exerted on the deficient tissue itself. In addition, NPWT has been generally observed to accelerate healing and is thought to promote angiogenesis,¹⁵ but in this case, progressive tissue desiccation leading to enlargement of the wound and the size of bone exposure was previously observed with NPWT.

Treatment

Figure 3 shows the nonhealing wound at the initial visit following mechanical debridement to remove necrotic tissue and disrupt and remove biofilm.¹⁶ PMVT was topically applied in an even distribution over the surface of the wound. Two vials of PMVT were initially utilized to fully cover the large 25 cm² wound through 10 weeks of treatment; then only 1 vial was required for subsequent visits. Following PMVT application, a nonadherent semiocclusive protective dressing (Adaptic Touch; 3M) was placed over the wound and adhesive bandages (Steri-Strips; 3M) were applied and covered with a standard dry dressing. A tubular net bandage (TG Fix; Lohmann & Rauscher) that provided retention and stability to the underlying dressings was also placed around the shin. The patient was directed not to change the wound dressing or to bathe, and to return weekly for assessment of the wound and (if needed) reapplication of the PMVT product. Wound size was measured at each visit.

Treatment results

The patient tolerated the PMVT treatment well with no adverse effects. After 1 week (Figure 4A), epithelialized tissue and revascularization of the entire perimeter of the wound, as well as adjacent tissues, was observed. Islands of new vascularity were observed in the medial aspect of the wound. After 3 weeks (Figure 4B), wound area and depth had started decreasing. Newly formed epithelizing tissue was observed along the entire wound rim within a 2-mm to 3-mm radius throughout, with continued revascularization throughout the wound bed. By 4 weeks (Figure 4C), continued vascular improvement was evident; previous avascular irradiated areas exhibited bleeding, and epithelized tissue around the wound rim had thickened to 4 mm to 5 mm.

From weeks 6 to 10 of PMVT treatment, the wound significantly decreased in area and depth as strips of newly formed epithelium started to grow from the defect edges, gradually thickening the neodermis-like layer under the epithelium and the rim of granulation tissue in front of the epithelium (Figure 4D, E). By this time, significant vascularization had centralized around the bony defect and shiny epithelizing tissue was apparent, as was continued remodeling and thickening of the epidermis from the periphery of the defect. New tissue had started to take on the appearance of native tissue, and the wound was becoming less frail as remodeled tissue matured. The bony defect presented at the same level as the surrounding tissue with some appearance of an island of tissue developing through or on top of the bone. Because of the decreased wound size, only 1 vial of PMVT was required to treat the ulcer at this point and for the duration of treatment.

As previously noted, the initial clinical objective was to arrest further deterioration, stabilize the wound while the patient continued chemotherapy, and bridge the time until flap surgery could be performed. It became quickly apparent through both serial physical examinations and photography, however, that given the reduced size of the defect and the increased area of surrounding granulation tissue followed by reepithelialization, the prognosis and treatment objective was changing from “stabilization” to “possible healing.”¹⁷

By 12 weeks, there was a noticeable change in the bone color from white to brown (Figure 5A). Upon probing, the bony sequestrum loosened up when depressed, and it was apparent that it was not contiguous with the underlying bone and wound rim. Upon further inspection, spontaneous separation of the outer cortex had occurred, with a layer of new vascularized tissue underneath the cortex that covered the bone and spanned the entire defect. Following removal of the cortical bone sequestrum from the wound (Figure 5B), revascularization from both the wound rim and the previously irradiated bone was evident, and a new layer of vascularized neoepidermal tissue had formed underneath the cortex (Figure 5C). The cortical shell may have served to create a protected healing environment, leading to revascularization and ultimately the generation of the surface with healthy-looking bone and soft tissue.

From weeks 13 through 15, the ulcer continued to improve and the tissue matured as if it had never been irradiated (Figure 6A, B). The center of the wound bridged with epithelialized tissue, creating 2 smaller defects with essentially no depth. The outer rim continued remodeling and taking on the morphology of native tissue. By 17 weeks, the epidermis had nicely remodeled and the residual small defects were well vascularized, and PMVT treatment was discontinued (Figure 6C). Between 17 and 21 weeks, continued progression of vascular granulation tissue was apparent, along with concentric epithelization from the residual defect edges (Figure 6D, E).

At 22 weeks after initial PMVT treatment, the defects had closed with a thick epidermis covering the residual granulating part of the wound site (Figure 7A). A visit at 25 weeks confirmed healing, with complete epithelialization of the shin defect (Figure 7B). At a follow-up visit 30 weeks after initial treatment (3 months after closure), continued healing was observed, with continued tissue thickening, improved pliability, and decreased scarring (Figure 7C). At that point, restrictions were released, and the patient returned to normal activity. A return visit by the patient more than 8 months after closure demonstrated the durability of the healed tissue (Figure 7D). Figure 8 displays a graph of the wound size over the entire course of PMVT treatment through the final follow-up visit.

Insufficient vascularity and a resulting senescent microenvironment, which may be induced by both intrinsic and extrinsic factors, are 2 important common factors in failed healing.^4,18-21 When invasive surgery is not feasible to heal the defect, agents that can support angiogenesis and reverse tissue senescence may be appropriate to use.²² The microvasculature—consisting of the capillaries, arterioles, venules, and their corresponding matrix components—is a key structural unit for maintaining tissue viability. Microvascular tissue serves as the foundation for granulation and remodeling during healing. Optimal repair of microvascular structure and function is essential for healing capacity and to minimize tissue breakdown in a newly epithelialized wound. This is especially true when the tissue microenvironment is intrinsically compromised by advanced age, diabetes, smoking, small vessel disease, or radiation. Restoring vascularity in lower leg wounds, in particular, is notoriously challenging.²³

In this context, the results observed during the treatment of this lower leg defect with PMVT are encouraging. Initial unsuccessful efforts to heal the wound with a split-thickness skin graft and a placental tissue-derived graft, coupled with the positive outcome associated with PMVT reported here, elicit questions about the mechanistic differences between these treatment modalities. The ability of the microvascular tissue fragments in PMVT to serve as attachment sites for responding host cells, with the aim of repairing the damaged microvasculature, may have initiated a broader response within the senescent periwound area and transitioned it from a chronic inflammatory environment to an acute healing state.

The healing observed in this case is consistent with that reported in previously published clinical and preclinical results with PMVT (Figure 9). Gould et al reported on the use of PMVT in a prospective, multicenter, randomized controlled trial of 100 patients with nonhealing neuropathic Wagner 1 and 2 diabetic foot ulcers.¹¹ Compared to the control treatment, weekly application of PMVT significantly increased complete wound closure and percent wound area reduction at 12 weeks, decreased time to healing, and improved local neuropathy. In addition, exploratory results indicated that increased wound site perfusion, as measured by fluorescence angiography, accompanied the PMVT-accelerated wound resolution. The author of the current study has also documented that topical application of PMVT stimulated durable wound closure in other complex, recalcitrant, or senescent wound environments.²⁴

Preclinically, PMVT has been shown to stimulate neovascularization, leading to increased blood flow and limb preservation in a SCID mouse ischemic hindlimb model. Following ligation and transection of the femoral artery of one hindlimb, administration of PMVT demonstrated a highly significant improvement in mean perfusion ratios as measured by laser Doppler imaging at day 14 compared with the control group.²⁴ Taken together, these clinical and preclinical results support the utility of microvascular tissue to address the compromised microvasculature found in chronic wounds by increasing blood flow in the tissue in and around the wound site.

It is important to note that while PMVT may be applied topically, it is not a powder (as evidenced by the images in Figure 1 demonstrating its structure) and may be administered sequentially in either an outpatient clinic or inpatient environment. While the PMVT product was provided by the manufacturer at no cost to this patient, the expense of utilizing an advanced treatment is always a consideration that must be balanced against the clinical value. In this case, by not only preventing further deterioration of the wound while the patient completed cancer treatment but ultimately enabling the patient to avoid the cost and additional trauma of flap surgery, thus maintaining quality of life, the health-economic benefit of PMVT is evident even if commercial prices had been paid.

As with any single case report, broad and general conclusions cannot be fully supported. While the positive results observed were promising in this case of complete and sustained wound closure in a compromised environment without the need for additional surgery, further research is needed. Additional studies in comparable patient populations would lead to better understanding of the clinical potential and limitations of PMVT in addressing recalcitrant wounds during cancer or other treatments that preclude surgical intervention, and of the mechanisms by which PMVT is functioning in these environments.

This case report demonstrated the potential of PMVT to address vascular deficiencies and impaired healing in a complex senescent and recalcitrant wound environment. In this patient, PMVT treatment was started with the objective of improving vascularity in preparation for flap transfer surgery. Healing the refractory tibial wound in this immunocompromised patient undergoing active chemotherapy, thus increasing quality of life without flap surgery, was unexpected. The use of PMVT to repair and reconstruct microvascular tissue appeared to change the trajectory of healing, and the clinical outcome supports the concept that PMVT enhances the wound healing process.