The Use of an Autologous Cell Harvesting and Processing Device to Decrease Surgical Procedures and Expedite Healing in Two Pediatric Burn Patients

Introduction. Autologous cell harvesting and processing devices are designed to facilitate the harvesting of cells using enzymatic and physical disruption techniques to immediately apply non-cultured autologous cell suspension (ACS) to the wound area. Objective. This case report evaluates clinical outcomes following application of cellular suspension with split-thickness skin grafts (STSGs) as an adjunct for definitive closure of burn injuries and donor sites in 2 pediatric patients. Materials and Methods. The cases were performed under a humanitarian use protocol following institutional review board approval at St. Christopher’s Hospital for Children (Philadelphia, PA). Results. The first patient was a 4-year-old girl with partial- and full-thickness (32% total body surface area) burn injuries of her head, trunk, flank, arms, thighs, and feet. The patient was discharged 19 days following ACS treatment. The second patient was an 18-month-old girl with partial- and full-thickness (21% total body surface area) burns involving the bilateral lower extremities. She was discharged 22 days after ACS treatment with widely meshed autograft. Neither patient required additional surgical interventions. All treatment and donor areas for both patients remained uninfected and neither patient experienced any unexpected treatment-related adverse events. Conclusions. These cases are the first of their kind reported in the pediatric population and suggest ACS in conjunction with STSGs can help decrease surgical procedures and expedite healing in pediatric patients with large surface burns.

Unintentional burn- and fire-related injuries are the third leading cause of death in children 5 to 9 years old, and the fifth leading cause of death by injury for children aged 1 to 4 years.¹ Further, children under 5 years old are 2.4 times more likely to require emergency medical treatment than other members of the general population following a burn injury.² Many burn survivors experience scarring and have life-long disabilities.³ Skin grafts can be challenging procedures to perform on pediatric patients.⁴ Skin grafting requires an additional procedure and general anesthesia as well as harvesting skin from non-injured donor sites. Donor site morbidity and other complications of pediatric skin grafts bring their own set of challenges.⁵ 

Autologous cell harvesting and processing devices are designed to facilitate the harvesting of cells using enzymatic and physical disruption techniques to immediately apply non-cultured epidermal cell suspension to the wound area. In the United States, RECELL (AVITA Medical, Valencia, CA) was approved by the US Food and Drug Administration (FDA) in September 2018 for patients 18 years of age and older. Permission was granted on the basis of compassionate use under the FDA by AVITA Medical. To be granted compassionate use, local Institutional Review Board (IRB) approval must be obtained and the device may only be used at the discretion of the investigator if the burn is subjectively felt to be potentially life-threatening. In adult patients, autologous cell suspension (ACS) has been shown to have comparable, non-inferior healing rates and significantly decreased donor site area, pain, and scarring compared with autologous meshed split-thickness skin grafts (STSGs).⁶ 

Wood et al⁷ conducted a randomized, controlled, pilot study examining differences in treatment by comparing standard of care, biosynthetic dressing, and biosynthetic dressing plus ACS treatment methods. Specifically, their study⁷ sought to determine the impact of treatment group on the number of surgeries performed, healing, pain, and scar outcomes. Results revealed patients in the biosynthetic dressing and biosynthetic dressing plus ACS treatment groups had fewer surgeries, shorter mean healing times, reduced maximum pain scores, and less scarring compared with the standard of care burn injury treatment.⁷ Researchers identified patients treated with biosynthetic dressing plus ACS were also less likely to require pressure garments,⁷ which ultimately decreased costs associated with treatment.⁸ 

Further, Wallace et al⁹ conducted a prospective case-controlled study to examine clinical factors impacting the development of a raised scar following the use of ACS on mid-dermal, deep-dermal, and full-thickness wounds. The researchers identified that a greater total body surface area (TBSA), wound healing that exceeded 14 days, and increased procedures predicted raised scars in children following surgical intervention.⁹ Lastly, Dunne and Rawlins¹⁰ reported a series of pediatric patients with scald burns who received early treatment (within 24–48 hours post injury) with ACS in combination with a biosynthetic dressing for mid to deep partial-thickness injuries. The researchers noted expedited wound closure, decreased donor site morbidity, and improved scar outcome.¹⁰ This report also documented 29% cost savings compared with conventional expectant management with delayed surgery for nonhealing burns.¹⁰ Given the findings from these studies, results suggest ACS may help to decrease the number of surgical interventions performed, pain, and scarring by expediting healing and minimizing donor site areas in pediatric burn patients.^7-10

No other case reports have appeared in the literature related to the use of ACS in conjunction with STSGsin pediatric patients. The cases presented herein describe the treatment and healing course of 2 pediatric patients treated with ACS in conjunction with STSGs to achieve closure of treatment areas while minimizing areas of donor sites.

Ethics and approval

Physicians at St. Christopher’s Hospital for Children (Philadelphia, PA), a pediatric burn center verified by the American Burn Association, applied for compassionate use under protocol NCT02992249 and were granted permission to use ACS on 2 pediatric patients with life-threatening burn injuries. These procedures were approved by the IRB as cases for compassionate use. Informed consent was obtained. 

Eligibility criteria

The patients had to be hemodynamically stable, require skin grafting for a life-threatening wound, and have inadequate skin for conventional graft harvesting to be included. These criteria were determined at the discretion of the investigators subjectively. Patients who were unable to follow the protocol, had an active infection at the treatment site, or had a known sensitivity to trypsin or compound sodium lactate were not eligible to participate. 

Methodology

For preparation of ACS in both patients, a thin donor skin sample was harvested so that donor skin measuring 1 cm² could be used for a treatment area up to 80 cm² in area. The skin sample acquired for ACS was incubated for 15 minutes in a warmed proprietary enzyme solution to break down adhesions between cells and the extracellular matrix in the dermo-epidermal junction. Following enzyme incubation, the skin samples were rinsed and mechanically disaggregated by scraping the dermal and epidermal layers. These disaggregated skin cells then were resuspended in buffer solution, filtered, and drawn up into a syringe with a nozzle attachment. The cell suspension consisted of a mixed population of live keratinocytes, melanocytes, and fibroblasts. The meshing ratio of the STSG for each patient was determined by the investigators based on the amount of healthy donor skin available and the location of the burned areas being treated. The compassionate use protocol required the meshing ratio to be at least 3:1. 

Prior to application of ACS, wounds were debrided and nonadherent, nonabsorbent, small-pore primary dressings were secured to the wound areas. The syringe of ACS was inverted multiple times to ensure homogeneous suspension of cells. The ACS was applied from the most elevated to the least elevated part over meshed STSGs and harvested donor sites evenly across the surface of the wound for both patients. The primary dressings were secured over the treated area followed by adherent, low-absorbent, small-pore dressings, petroleum gauze, and dry gauze. The patients were placed on no shearing precautions, and the primary dressings were not disturbed for at least 1 week following ACS treatment. Outer secondary dressings were changed as needed. After the first postoperative dressing change at 7 days, secondary dressings were changed every 1 to 2 days, leaving the primary dressing layer in place until it autodetached with reepithelialization. The dressing schedule was based on clinical assessment of the wounds and the judgement and preference of the attending burn surgeon.

After ACS application, patients were evaluated on days 7, 14, and 28. If wounds were not healed by day 28, then patients followed-up monthly until their wounds were closed prior to long-term follow-ups at 1 month following wound closure and 1-year posttreatment. Neither the patient nor the investigators were blinded to the treatment. 

Upon follow-up, reepithelization, appearance, and presence of infection were evaluated visually for each wound utilizing the grading systems, mentioned in the following sentences, were required for reporting per the compassionate use protocol. Reepithelization was operationalized as 100%, 95% to 99%, __% (to be filled in by the investigator), and no change since prior visit. Appearance was broken down into color match, pigment match, and texture match. All 3 appearance categories were scored on the basis of being matched, mildly mismatched, grossly mismatched, or not done. Infection was judged visually and indicated as being uninfected, mild, moderate, or severe. Wounds were considered to be uninfected if they were free from purulence or any manifestations of inflammation. Adverse events were recorded at each visit. Adverse events could be classified as mild, moderate, or severe, as well as anticipated or unanticipated. Further, investigators were asked to make determinations about whether adverse events were definitely, likely, unlikely, unrelated, or unknown (if related to the treatment). Serious adverse events were classified as being life-threatening, resulting in or contributing to death; resulting in permanent disability or incapacity; inpatient hospitalization; prolonged hospitalization; necessitating medical or surgical intervention to prevent a permanent disability or incapacity; and/or congenital abnormality or birth defect.

Case 1

The first patient was a 4-year-old girl with 32% TBSA burn injury. The patient sustained partial-thickness and full-thickness burn injuries when a crockpot of hot grease spilled on her face, trunk, flank, arms, thighs, and feet (Figure 1A). Cadaver skin was used to temporarily cover the open burns after tangential excision. Ultimately, based on the size and location of the burns as well as the heightened risk of infection, it was decided treatment with ACS was appropriate. Written, informed consent was obtained, and treatment was initiated about 2 weeks post-injury. 

Using a powered dermatome, about 500 cm² of split-thickness skin was harvested from the patient’s back at 0.009 in to 0.010 in for STSG (Figure 1B). About 140 cm² of split-thickness skin was harvested from the left posterior thigh at 0.006 in to 0.008 in for ACS processing. Skin from the patient’s left posterior thigh, measuring 36 cm², was prepared using the device in the operating room (OR) at the same time debridement and grafting were performed. Donor skin from the back was applied to areas sustaining full-thickness burns in a meshed 4:1 ratio on the trunk, flank, left inner arm, right distal inner arm, and anterior thighs and then treated with ACS. The 4:1 ratio was determined at the discretion of the investigator (W.J.D.) and was chosen to further reduce the amount of donor skin harvested. The patient’s feet, which sustained partial-thickness burns, and donor sites were only treated with the cell suspension. Overall, the patient was treated with about 1868 cm² of ACS coverage.

At day 7 post-ACS treatment, the patient’s treatment sites had reached 30% to 100% epithelization, and donor sites had reached 60% to 100% epithelization. At day 14 post-ACS treatment, all treatment sites had reached 95% to 100% epithelization, and all donor sites had reached 100% epithelization. The patient did not need any additional surgical interventions and was discharged 19 days post-ACS treatment. At day 28 post-ACS treatment, all treatment and donor sites had reached 100% epithelization. Donor sites remained healed with mild mismatch in color and pigment and were matched in texture. 

All treatment areas remained uninfected during the course of healing. At 8-month follow-up, the appearance of the treatment areas grafted using STSGs was mildly mismatched in color and pigment and grossly mismatched in texture on the patient’s trunk and bilateral arms and thighs (Figure 1C). The lower extremity sites treated with ACS were only mildly mismatched in color, pigment, and texture. The back donor sites were mildly mismatched in color, pigment, and texture (Figure 1D). One scar on the patient’s left wrist developed a hypertrophic scar that is being managed with pressure garments.

Case 2

The second patient was an 18-month-old girl with 21% TBSA burn injuries. The patient was injured when a caretaker submerged her in hot bathwater. The patient sustained partial- and full-thickness burn injuries to her bilateral lower extremities (Figure 2A). The burns were completely circumferential from the ankles to mid thighs, and the dorsal feet and toes also were burned. As the burn depth was mixed and the burned skin remained elastic without tight circumferential bands of eschar, she did not require escharotomies or fasciotomies and maintained normal distal perfusion. Cadaver allograft and dehydrated human amnion/chorion membrane (dHACM) initially were used to treat and stabilize the burn injury. The lower extremities had deep partial- and full-thickness burns that required autografting. The allograft was placed to prepare the wound beds after tangential excision. The thighs and dorsal feet appeared mid dermal after excision, so dHACM was placed on these areas to allow for further healing. Due to the patient’s potential for donor site morbidity, large surface area of the burn injury, and risk of infection with prolonged healing, the decision was made to use ACS. Written, informed consent was obtained, and the treatment was initiated about 3 weeks post-injury. 

About 416 cm² of split-thickness skin was harvested using a powered dermatome from the patient’s back and posterior scalp for the STSG and ACS treatment. Skin from the patient’s upper back was harvested at 0.006 in to 0.008 in, right mid-back at 0.009 in to 0.010 in, left mid-back at 0.011 in to 0.012 in, and posterior head at 0.009 in to 0.010 in (Figure 2B). Harvested skin from the back and posterior scalp, which are used in the authors’ practice frequently, were applied in a meshed 3:1 ratio to the bilateral lower extremities. The 3:1 ratio was determined at the discretion of the investigator (B.A.B.) and chosen to minimize the amount of donor skin harvested. Skin from the patient’s upper back, measuring 18 cm², was prepared using the autologous cell processing device and applied using the spray applicator to the bilateral lower extremities following the application of STSGs. Both treatment and donor sites were sprayed with ACS for a total area coverage of about 1216 cm². 

At day 7 post-ACS treatment, the primary dressings were evaluated and left in place until the area healed. By day 14 post-ACS treatment, the donor sites had reached 100% epithelization. Treatment areas were estimated to be healed between 70% to 85% at 14 days post-ACS treatment. The patient did not require any additional surgical interventions and was discharged 22 days after ACS treatment.

All treatment areas remained uninfected during the course of healing. By day 28 post-ACS treatment, the patient’s treatment and donor sites had reached 95% to 99% and 100% epithelization, respectively. The appearance of the treatment areas on the patient’s lower extremities were grossly mismatched in color, pigment, and texture. The patient’s back and scalp donor sites were mildly mismatched in color, grossly mismatched in pigment, and matched in texture. 

At the patient’s 3-month follow-up, the appearance of the treatment areas grafted using STSGs were grossly mismatched in color, pigment, and texture on the bilateral lower extremities (Figure 2C). The back and donor sites treated with ACS were only mildly mismatched in color and texture and grossly mismatched in pigment (Figure 2D). Scalp donor sites were matched in color, pigment, and texture. 

Autologous cell harvesting and processing devices facilitate rapid cell harvest of autologous cells through both enzymatic and physical disruption and create a non-cultured epidermal cell suspension that can be applied to the wounded area immediately in the OR. The non-cultured epidermal cell suspension consists of keratinocytes, melanocytes, fibroblasts, Langerhans cells, and cell signaling factors.¹¹ The primary benefits of ACS are immediate availability and minimization of skin donor sites. In both patients, ACS alone was used on donor sites, and it was used in conjunction with STSGs on full-thickness burn areas. The ACS also was applied to both patients’ ungrafted partial-thickness burns. Clinical evidence suggests ACS works best when used in conjunction with STSGs for full-thickness wounds in adults.¹² To the best of the authors’ knowledge, this is the first case report in the literature to highlight the use of ACS in conjunction with STSGs in pediatric patients.

Large autograft donor sites in pediatric patients can create potential morbidity by exposing additional areas to possible infection and increasing risk of scarring.⁴ Pediatric STSGs require monitoring over time for the development of scar contracture as patients grow. In patients with massive burns, achieving total definitive autologous wound coverage is immensely challenging. The issue of limited donor sites is not exclusively an issue unique to pediatrics, but presents a special challenge to physicians caring for pediatric patients who have a different distribution of body surface area.⁴ In cases where large areas of a patient’s body have been burned, physicians may decide to use biologic and synthetic skin substitutes, but ultimately autologous skin coverage may be needed.¹³

One solution to the challenge of limited donor sites in massive burns are cultured epithelial autografts (CEAs), in which very thin sheets of autologous epidermis are grown at an off-site laboratory. The primary benefit of a CEA is the small donor site — two 2 cm x 6 cm diamond-shaped, full-thickness biopsies. Disadvantages of this treatment are poor durability of the skin coverage and a 3- to 5-week waiting period for the cells to be available.^13,14 A CEA is also extremely expensive to produce.^13,14 In addition, CEAs must be placed over a neodermis, which can be created with bovine-based dermal regeneration templates or human acellular dermal matrices. All of these products are quite expensive, subject to graft loss or infection, and require substantial time and meticulous effort for success.¹³ Other alternatives include standard STSG with repeated re-harvesting of the limited donor site, which can cause increased scarring at the donor site and requires waiting for the donor site to heal prior to each re-harvest. As an alternative to CEA, ACS can be used as an adjunct to traditional skin grafts and biologic or synthetic skin substitutes, thus eliminating the wait time of growing epithelial cells at an off-site laboratory. Previous research suggests wounds treated with keratinocytes, melanocytes, fibroblasts, Langerhans cells, and cell signaling factors have improved reepithelization, scar texture, repigmentation, and decreased systemic effects, scar contracture, wound infection, and adverse reactions.^8,15-17

In the authors’ opinion, ACS is best used in cases in which donor sites are limited and the burn area is relatively large. This is especially pertinent in full-thickness wounds in which re-harvesting the same donor site is suboptimal because it is difficult to re-harvest grafts of sufficient thickness to replace full-thickness skin loss. Combining ACS with a widely meshed skin graft in these cases would be a reasonable compromise. Autologous cell suspension alone could be useful in mid to deep dermal burns where autografting might be desired to accelerate healing and minimize the risk of hypertrophic scarring; however, a large standard STSG donor site is undesirable and perhaps not justified by the potential benefits. In addition, ACS potentially could be useful in any large wound in which autografting is needed and donor sites are limited. Regardless of the type of wound, ACS could be utilized when the wound is ready for autografting. This could be for immediate autografting after excision of a large lesion, such as a giant congenital melanocytic nevus, or for delayed autografting in a traumatic wound requiring serial debridement in preparation for grafting. Due to the cost of ACS, the authors would not recommend using it for small burns or wounds in which a sufficient, good-quality donor site is available.

This case report is not without limitations. Participants were not compared with controls or evaluated against other techniques. A formal, randomized, controlled, pediatric clinical trial began in 2019 to address these limitations. Future studies should also use validated scales to measure outcomes. The sample size should be taken into account when discussing the generalizability of these findings, along with the lack of control and subjective evaluations associated with the nature of these cases; however, this is the first case report to discuss ACS in conjunction with STSGs in the pediatric population. The cost of ACS is about $6000 USD retail; the cost of the supplies to perform this treatment need to be considered against the cost of CEAs and benefit of early discharge. 

Under the compassionate use study NCT02992249, ACS was utilized for patients who have suffered from burn injuries and did not have adequate available skin to harvest for conventional grafting. Subsequently, formal FDA approval was granted for patients 18 years of age and older, and this product is now available without the need for an IRB application under compassionate use. There were no infectious complications of ACS treatment in the patients presented, although both patients developed hypertrophic scars. Neither patient experienced any unexpected treatment-related adverse events. Treatment in both cases demonstrated positive outcomes, while enhancing quality of care and patient safety. At day 14 post-ACS treatment, donor sites reached 100% epithelization for both patients. By day 28 post-ACS treatment, the first patient’s treatment areas reached 100% epithelization and the second patient’s treatment areas reached 95% to 99% epithelization. Neither patient required further surgical intervention. These cases support the existing literature that suggests ACS can help decrease surgical procedures and expedite healing and the use of ACS in children, especially in conjunction with STSGs

Authors: Autumn D. Nanassy, MA; Paul M. Glat, MD; Brooke A. Burkey, MD; Amit C. Misra, MD; Loreen K. Meyer, MSN, RN; Lisa Gates, RN, CNOR; and Wellington J. Davis, MD

Affiliation: St. Christopher’s Hospital for Children, Philadelphia, PA

Correspondence: Autumn D. Nanassy, MA, Clinical Research Coordinator, St. Christopher’s Hospital for Children, Trauma Services, 160 E. Erie Avenue, Trauma Services Department, Philadelphia, PA 19134; Autumn.Nanassy@americanacademic.com 

Disclosure: The authors disclose no financial or other conflicts of interest.