Regenerative medicine applications in combat casualty care

Manipulating adrenergic stress receptor signalling to enhance immunosuppression and prolong survival of vascularized composite tissue transplants

BACKGROUND

Vascularized composite tissue allotransplantation (VCA) to replace limbs or faces damaged beyond repair is now possible. The resulting clear benefit to quality of life is a compelling reason to attempt this complex procedure. Unfortunately, the high doses of immunosuppressive drugs required to protect this type of allograft result in significant morbidity and mortality giving rise to ethical concerns about performing this surgery in patients with non-life-threatening conditions. Here we tested whether we could suppress anti-graft immune activity by using a safe β2 -adrenergic receptor (AR) agonist, terbutaline, to mimic the natural immune suppression generated by nervous system-induced signalling through AR.

METHODS

A heterotopic hind limb transplantation model was used with C57BL/6 (H-2b) as recipients and BALB/c (H-2d) mice as donors. To test the modulation of the immune response, graft survival was investigated after daily intraperitoneal injection of β2 -AR agonist with and without tacrolimus. Analyses of immune compositions and quantification of pro-inflammatory cytokines were performed to gauge functional immunomodulation. The contributions to allograft survival of β2 -AR signalling in donor and recipient tissue were investigated with β2 -AR-/- strains.

RESULTS

Treatment with the β2 -AR agonist delayed VCA rejection, even with a subtherapeutic dose of tacrolimus. β2 -AR agonist decreased T-cell infiltration into the transplanted grafts and decreased memory T-cell populations in recipient's circulation. In addition, decreased levels of inflammatory cytokines (IFN-γ, IL-6, TNF-α, CXCL-1/10 and CCL3/4/5/7) were detected following β2 -AR agonist treatment, and there was a decreased expression of ICAM-1 and vascular cell adhesion molecule-1 in donor stromal cells.

CONCLUSIONS

β2 -AR agonist can be used safely to mimic the natural suppression of immune responses, which occurs during adrenergic stress-signalling and thereby can be used in combination regimens to reduce the dose needed of toxic immunosuppressive drugs such as tacrolimus. This strategy can be further evaluated for feasibility in the clinic.

Clinical Effect of Microneedle Injection Combined with Blood Transfusion in the Treatment of Severe Anemia Complicated with Vitiligo under Regenerative Medical Technology

To explore the clinical efficacy of microneedle injection combined with blood transfusion in the treatment of severe anemia complicated with vitiligo based on regenerative medical technology and provide the theoretical basis for the adoption of microneedle technology, 60 patients with severe anemia complicated with vitiligo were selected as research objects. With 15 patients in each group, they were randomly assigned to the control group (calcipotriol ointment external application), observation group A (external application of moist exposed burn ointment (MEBO), observation group B (external application of MEBO combined with blood transfusion), and observation group C (microneedle injection of MEBO combined with blood transfusion). Blood indexes and plaque recovery of patients in different periods were detected. The total protein (TP) content in group C (62.3 ± 3.3 g/L and 64.3 ± 2.88 g/L) was remarkably higher than that in the control group (51.3 ± 3.17 g/L and 52.4 ± 3.17 g/L) and group A (52.6 ± 2.91 g/L and 51.8 ± 2.98 g/L)) at the 5th and 7th weeks after the treatment (P < 0.05). The albumin (ALB) content in group C (42.9 ± 3.28 g/L and 45.3 ± 3.1 g/L) was signally higher than that in the control group (41.8 ± 3.44 g/L and 41.9 ± 3.23 g/L) and group A (41.3 ± 2.91 g/L and 42.1 ± 3.02 g/L) at the 5th and 7th weeks after the treatment, and the content was markedly higher than that in group B at 5th week (P < 0.05). The wound healing rates of group C at the 3rd, 5th, and 7th weeks after the treatment (38.44%, 56.6%, and 90.23%) were greatly higher than those of the control group, group A, and group B (P < 0.05). Besides, the wound healing rate of group B was higher than that of the control group and group A (40.3% and 75.8%) at the 5th and 7th weeks after the treatment (P < 0.05). To sum up, based on regenerative medical technology, microneedle injection (microneedling is a derma roller process that pricks the skin with minuscule needles. The goal of the treatment is to develop new collagen and skin tissue, resulting in skin that is smoother, firmer, and more toned) combined with blood transfusion had a good therapeutic effect on patients with severe anemia complicated with vitiligo, which could manifestly improve the blood indexes and skin plaques of patients, with a good clinical adoption effect.

Utility of a Continuous External Tissue Expander in Complex Pediatric Wound Reconstruction

BACKGROUND

Soft tissue reconstruction following traumatic injury can be devastating. Reconstructive treatment modalities can prove to be complex. DermaClose (Synovis Micro Companies Alliance, Inc) is a relatively novel wound closure device that has gained popularity for continuous external tissue expansion (CETE).

METHODS

A single-institution case series of 3 traumatic pediatric soft tissue injuries in which DermaClose was used for soft tissue reconstruction as an alternative to free tissue transfer was presented. A review of the literature to identify similar reported cases was also conducted.

RESULTS

The authors report their success with the use of this continuous external tissue expander in the management of pediatric soft tissue injuries. Open tibial fractures were sustained by 2 patients, and 1 patient suffered an avulsion injury to the scalp; sequential DermaClose application was successfully utilized to achieve wound closure in all cases.

CONCLUSIONS

The minimal amount of data currently available in the literature that document the use of this continuous external tissue expander in pediatric patients suggest that its safety and efficacy are inadequately investigated in this population. The cases included in this report suggest DermaClose may be an alternative to traditional methods for complex soft tissue closure in pediatric patients. For larger wounds, repeat applications with sequential closure should be expected and is described in an algorithm within this report.

Lower extremity reconstruction for limb salvage and functional restoration - The Combat experience

Evolution in extremity injury treatment often occurs during major conflicts, with lessons learned applied and translated among military and civilian settings. In recent periods of war, improvements in protective equipment, in-theater damage control resuscitation/surgery, delivery of antibiotics locally/systemically, and rapid evacuation to higher levels of medical care capabilities have greatly improved combat casualty survivability rates. Additionally, widespread application of lower extremity tourniquets also has prevented casualties from exsanguination, thus reducing hemorrhagic-related deaths. Secondary to these, a high number of combat casualties suffering lower extremity traumatic injuries have presented for functional limb reconstruction and restoration as well as residual limb care.

Bench-to-Bedside Lessons Learned: Commercialization of an Acellular Nerve Graft

Peripheral nerve injury can result in debilitating outcomes including loss of function and neuropathic pain. Although nerve repair research and therapeutic development are widely studied, translation of these ideas into clinical interventions has not occurred at the same rate. At the turn of this century, approaches to peripheral nerve repair have included microsurgical techniques, hollow conduits, and autologous nerve grafts. These methods provide satisfactory results; however, they possess numerous limitations that can prevent effective surgical treatment. Commercialization of Avance, a processed nerve allograft, sought to address limitations of earlier approaches by providing an off-the-shelf alternative to hollow conduits while maintaining many proregenerative properties of autologous grafts. Since its launch in 2007, Avance has changed the landscape of the nerve repair market and is used to treat tens of thousands of patients. Although Avance has become an important addition to surgeon and patient clinical options, the product's journey from bench to bedside took over 20 years with many research and commercialization challenges. This article reviews the events that have brought a processed nerve allograft from the laboratory bench to the patient bedside. Additionally, this review provides a perspective on lessons and considerations that can assist in translation of future medical products.

Peripheral nerve repair throughout the body with processed nerve allografts: Results from a large multicenter study

BACKGROUND

Peripheral nerve damage resulting in pain, loss of sensation, or motor function may necessitate a reconstruction with a bridging material. The RANGER® Registry was designed to evaluate outcomes following nerve repair with processed nerve allograft (Avance® Nerve Graft; Axogen; Alachua, FL). Here we report on the results from the largest peripheral nerve registry to-date.

METHODS

This multicenter IRB-approved registry study collected data from patients repaired with processed nerve allograft (PNA). Sites followed their own standard of care for patient treatment and follow-up. Data were assessed for meaningful recovery, defined as ≥S3/M3 to remain consistent with previously published results, and comparisons were made to reference literature.

RESULTS

The study included 385 subjects and 624 nerve repairs. Overall, 82% meaningful recovery (MR) was achieved across sensory, mixed, and motor nerve repairs up to gaps of 70 mm. No related adverse events were reported. There were no significant differences in MR across the nerve type, age, time-to-repair, and smoking status subgroups in the upper extremity (p > .05). Significant differences were noted by the mechanism of injury subgroups between complex injures (74%) as compared to lacerations (85%) or neuroma resections (94%) (p = .03) and by gap length between the <15 mm and 50-70 mm gap subgroups, 91 and 69% MR, respectively (p = .01). Results were comparable to historical literature for nerve autograft and exceed that of conduit.

CONCLUSIONS

These findings provide clinical evidence to support the continued use of PNA up to 70 mm in sensory, mixed and motor nerve repair throughout the body and across a broad patient population.

Recovery of Motor Function after Mixed and Motor Nerve Repair with Processed Nerve Allograft

Supplemental Digital Content is available in the text.

Background:

Severe trauma often results in the transection of major peripheral nerves. The RANGER Registry is an ongoing observational study on the use and outcomes of processed nerve allografts (PNAs; Avance Nerve Graft, AxoGen, Inc., Alachua, Fla.). Here, we report on motor recovery outcomes for nerve injuries repaired acutely or in a delayed fashion with PNA and comparisons to historical controls in the literature.

Methods:

The RANGER database was queried for mixed and motor nerve injuries in the upper extremities, head, and neck area having completed greater than 1 year of follow-up. All subjects with sufficient assessments to evaluate functional outcomes were included. Meaningful recovery was defined as ≥M3 on the Medical Research Council scale. Demographics, outcomes, and covariate analysis were performed to further characterize this subgroup.

Results:

The subgroup included 20 subjects with 22 nerve repairs. The mean ± SD (minimum–maximum) age was 38 ± 19 (16–77) years. The median repair time was 9 (0–133) days. The mean graft length was 33 ± 17 (10–70) mm with a mean follow-up of 779 ± 480 (371–2,423) days. Meaningful motor recovery was observed in 73%. Subgroup analysis showed no differences between gap lengths or mechanism of injury. There were no related adverse events.

Conclusions:

PNAs were safe and provided functional motor recovery in mixed and motor nerve repairs. Outcomes compare favorably to historical controls for nerve autograft and exceed those for hollow tube conduit. PNA may be considered as an option when reconstructing major peripheral nerve injuries.

Advances in addressing full-thickness skin defects: a review of dermal and epidermal substitutes

full-thickness skin defects remain a reconstructive challenge. Novel regenerative modalities can aid in addressing these defects. A literature review of currently available dermal and epidermal regenerates was performed. The mechanism and application for each skin substitute was analyzed to provide a guide for these modalities. Available epidermal substitutes include autografts and allografts and may be cultured or noncultured. Dermal regenerate templates exist in biologic and synthetic varieties that differ in the source animal and processing. Epidermal and dermal skin substitutes are promising adjunctive tools for addressing certain soft tissue defects and have improved outcomes in reconstructive procedures. The following article provides a comprehensive review of the biologic materials available and the types of complex wounds amenable to their use.

Biomimetic Architectures for Peripheral Nerve Repair: A Review of Biofabrication Strategies

Biofabrication techniques have endeavored to improve the regeneration of the peripheral nervous system (PNS), but nothing has surpassed the performance of current clinical practices. However, these current approaches have intrinsic limitations that compromise patient care. The "gold standard" autograft provides the best outcomes but requires suitable donor material, while implantable hollow nerve guide conduits (NGCs) can only repair small nerve defects. This review places emphasis on approaches that create structural cues within a hollow NGC lumen in order to match or exceed the regenerative performance of the autograft. An overview of the PNS and nerve regeneration is provided. This is followed by an assessment of reported devices, divided into three major categories: isotropic hydrogel fillers, acting as unstructured interluminal support for regenerating nerves; fibrous interluminal fillers, presenting neurites with topographical guidance within the lumen; and patterned interluminal scaffolds, providing 3D support for nerve growth via structures that mimic native PNS tissue. Also presented is a critical framework to evaluate the impact of reported outcomes. While a universal and versatile nerve repair strategy remains elusive, outlined here is a roadmap of past, present, and emerging fabrication techniques to inform and motivate new developments in the field of peripheral nerve regeneration.

Management of Mangled Extremities and Orthopaedic War Injuries

In 16 years of conflict, primarily in Iraq and Afghanistan, wounded warriors have primarily been subjected to blast type of injuries. Evacuation strategies have led to unprecedented survival rates in blast-injured soldiers, resulting in large numbers of wounded warriors with complex limb trauma. Bone and soft tissue defects have resulted in increased use of complex reconstructive algorithms to restore limbs and function. In addition, in failed salvage attempts, advances in amputation options are being developed. In this review, we summarize state-of-the-art limb-salvage methods for both soft tissue and bone. In addition, we discuss advances in diagnostic methods with development of personalized clinical decision support tools designed to optimize outcomes after severe blast injuries. Finally, we present new advances in osteointegrated prostheses for above-knee amputations.

Towards rebuilding vaginal support utilizing an extracellular matrix bioscaffold

As an alternative to polypropylene mesh, we explored an extracellular matrix (ECM) bioscaffold derived from urinary bladder matrix (MatriStem™) in the repair of vaginal prolapse. We aimed to restore disrupted vaginal support simulating application via transvaginal and transabdominal approaches in a macaque model focusing on the impact on vaginal structure, function, and the host immune response. In 16 macaques, after laparotomy, the uterosacral ligaments and paravaginal attachments to pelvic side wall were completely transected (IACUC# 13081928). 6-ply MatriStem was cut into posterior and anterior templates with a portion covering the vagina and arms simulating uterosacral ligaments and paravaginal attachments, respectively. After surgically exposing the correct anatomical sites, in 8 animals, a vaginal incision was made on the anterior and posterior vagina and the respective scaffolds were passed into the vagina via these incisions (transvaginal insertion) prior to placement. The remaining 8 animals underwent the same surgery without vaginal incisions (transabdominal insertion). Three months post implantation, firm tissue bands extending from vagina to pelvic side wall appeared in both MatriStem groups. Experimental endpoints examining impact of MatriStem on the vagina demonstrated that vaginal biochemical and biomechanical parameters, smooth muscle thickness and contractility, and immune responses were similar in the MatriStem no incision group and sham-operated controls. In the MatriStem incision group, a 41% decrease in vaginal stiffness (P=0.042), a 22% decrease in collagen content (P=0.008) and a 25% increase in collagen subtypes III/I was observed vs. Sham. Active MMP2 was increased in both Matristem groups vs. Sham (both P=0.002). This study presents a novel application of ECM bioscaffolds as a first step towards the rebuilding of vaginal support.

STATEMENT OF SIGNIFICANCE

Pelvic organ prolapse is a common condition related to failure of the supportive soft tissues of the vagina; particularly at the apex and mid-vagina. Few studies have investigated methods to regenerate these failed structures. The overall goal of the study was to determine the feasibility of utilizing a regenerative bioscaffold in prolapse applications to restore apical (level I) and lateral (level II) support to the vagina without negatively impacting vaginal structure and function. The significance of our findings is two fold: 1. Implantation of properly constructed extracellular matrix grafts promoted rebuilding of level I and level II support to the vagina and did not negatively impact the overall functional, morphological and biochemical properties of the vagina. 2. The presence of vaginal incisions in the transvaginal insertion of bioscaffolds may compromise vaginal structural integrity in the short term.

Extracellular matrix regenerative graft attenuates the negative impact of polypropylene prolapse mesh on vagina in rhesus macaque

BACKGROUND

The use of wide pore lightweight polypropylene mesh to improve anatomical outcomes in the surgical repair of prolapse has been hampered by mesh complications. One of the prototype prolapse meshes has been found to negatively impact the vagina by inducing a decrease in smooth muscle volume and contractility and the degradation of key structural proteins (collagen and elastin), resulting in vaginal degeneration. Recently, bioscaffolds derived from extracellular matrix have been used to mediate tissue regeneration and have been widely adopted in tissue engineering applications.

OBJECTIVE

Here we aimed to: (1) define whether augmentation of a polypropylene prolapse mesh with an extracellular matrix regenerative graft in a primate sacrocolpopexy model could mitigate the degenerative changes; and (2) determine the impact of the extracellular matrix graft on vagina when implanted alone.

STUDY DESIGN

A polypropylene-extracellular matrix composite graft (n = 9) and a 6-layered extracellular matrix graft alone (n = 8) were implanted in 17 middle-aged parous rhesus macaques via sacrocolpopexy and compared to historical data obtained from sham (n = 12) and the polypropylene mesh (n = 12) implanted by the same method. Vaginal function was measured in passive (ball-burst test) and active (smooth muscle contractility) mechanical tests. Vaginal histomorphologic/biochemical assessments included hematoxylin-eosin and trichrome staining, immunofluorescent labeling of α-smooth muscle actin and apoptotic cells, measurement of total collagen, collagen subtypes (ratio III/I), mature elastin, and sulfated glycosaminoglycans. Statistical analyses included 1-way analysis of variance, Kruskal-Wallis, and appropriate post-hoc tests.

RESULTS

The host inflammatory response in the composite mesh-implanted vagina was reduced compared to that following implantation with the polypropylene mesh alone. The increase in apoptotic cells observed with the polypropylene mesh was blunted in the composite (overall P < .001). Passive mechanical testing showed inferior parameters for both polypropylene mesh alone and the composite compared to sham whereas the contractility and thickness of smooth muscle layer in the composite were improved with a value similar to sham, which was distinct from the decreases observed with polypropylene mesh alone. Biochemically, the composite had similar mature elastin content, sulfated glycosaminoglycan content, and collagen subtype III/I ratio but lower total collagen content when compared to sham (P = .011). Multilayered extracellular matrix graft alone showed overall comparable values to sham in aspects of the biomechanical, histomorphologic, or biochemical endpoints of the vagina. The increased collagen subtype ratio III/I with the extracellular matrix graft alone (P = .033 compared to sham) is consistent with an ongoing active remodeling response.

CONCLUSION

Mesh augmentation with a regenerative extracellular matrix graft attenuated the negative impact of polypropylene mesh on the vagina. Application of the extracellular matrix graft alone had no measurable negative effects suggesting that the benefits of this extracellular matrix graft occur when used without a permanent material. Future studies will focus on understanding mechanisms.

A Case Report of the First Nonburn-related Military Trauma Victim Treated with Spray Skin Regenerative Therapy in Combination with a Dermal Regenerate Template

Massive soft tissue and skin loss secondary to war-related traumas are among the most frequently encountered challenges in the care of wounded warriors. This case report outlines the first military nonburn-related trauma patient treated by a combination of regenerative modalities. Our case employs spray skin technology to an established dermal regenerate matrix. Our patient, a 29-year-old active duty male, suffered a combat blast trauma in 2010 while deployed. The patient’s treatment course was complicated by a severe necrotizing fasciitis infection requiring over 100 surgical procedures for disease control and reconstruction. In secondary delayed reconstruction procedures, this triple-limb amputee underwent successful staged ventral hernia repair via a component separation technique with biologic mesh underlay although this resulted in a skin deficit of more than 600 cm². A dermal regenerate template was applied to the abdominal wound to aid in establishing a “neodermis.” Three weeks after dermal regenerate application, spray skin was applied to the defect in conjunction with a 6:1 meshed split thickness skin graft. The dermal regenerate template allowed for optimization of the wound bed for skin grafting. The use of spray skin allowed for a 6:1 mesh ratio, thus minimizing the donor-site size and morbidity. Together, this approach resulted in complete healing of a large full-thickness wound. The patient is now able to perform activities of daily living, walk without a cane, and engage in various physical activities. Overall, our case highlights the potential that combining regenerative therapies can achieve in treating severe war-related and civilian traumatic injuries.

Plastic Surgery Challenges in War Wounded II: Regenerative Medicine

Background: A large volume of service members have sustained complex injuries during Operations Iraqi Freedom (OIF) and Enduring Freedom (OEF). These injuries are complicated by contamination with particulate and foreign materials, have high rates of bacterial and/or fungal infections, are often composite-type defects with massive soft tissue wounds, and usually have multisystem involvement. While traditional treatment modalities remain a mainstay for optimal wound care, traditional reconstruction approaches alone may be inadequate to fully address the scope and magnitude of such massive complex wounds. As a result of these difficult clinical problems, the use of regenerative medicine therapies, such as autologous adipose tissue grafting, stem cell therapies, nerve allografts, and dermal regenerate templates/extracellular matrix scaffolds, is increased as adjuncts to traditional reconstructive measures. Basic and Clinical Science Advances: The beneficial applications of regenerative medicine therapies have been well characterized in both in vitro studies and in vivo animal studies. The use of these regenerative medicine techniques in the treatment of combat casualty injuries has been increasing throughout the recent war conflicts. Clinical Care Relevance: Military medicine has shown positive results when utilizing certain regenerative medicine modalities in treating complex war wounds. As a result, multi-institution clinical trials are underway to further evaluate these observations and reconstruction measures. Conclusion: Successful combat casualty wound care often requires a combination of traditional aspects of the reconstructive ladder/elevator with adoption of various regenerative medicine therapies. Due to the recent OIF/OEF conflicts, a high volume of combat casualties have benefited from adoption of regenerative medicine therapies and increased access to innovative clinical trials. Furthermore, many of these patients have had long-term follow-up to report on clinical outcomes that substantiate current treatment paradigms and concepts within regenerative medicine, reconstructive, and rehabilitation care. These results are applicable to not only combat casualty care but also to nonmilitary patients.

Autograft Substitutes: Conduits and Processed Nerve Allografts

Manufactured conduits and allografts are viable alternatives to direct suture repair and nerve autograft. Manufactured tubes should have gaps less than 10 mm, and ideally should be considered as an aid to the coaptation. Processed nerve allograft has utility as a substitute for either conduit or autograft in sensory nerve repairs. There is also a growing body of evidence supporting their utility in major peripheral nerve repairs, gap repairs up to 70 mm in length, as an alternative source of tissue to bolster the diameter of a cable graft, and for the management of neuromas in non-reconstructable injuries.

The use of urinary bladder matrix in the treatment of trauma and combat casualty wound care

Treatment of combat injuries and resulting wounds can be difficult to treat due to compromised and evolving tissue necrosis, environmental contaminants, multidrug resistant microbacterial and/or fungal infections, coupled with microvascular damage and/or hypovascularized exposed vital structures. Our group has developed surgical care algorithms with identifiable salvage techniques to achieve stable, definitive wound coverage often with the aid of certain regenerative medicine biologic scaffold materials and advanced wound care to facilitate tissue coverage and healing. This case series reports on the role of urinary bladder matrix scaffolds in the wound care and reconstruction of traumatic and combat wounds. Urinary bladder matrix was found to facilitate definitive soft tissue reconstruction by establishing a neovascularized soft tissue base acceptable for second stage wound and skin coverage options within traumatic and combat-related wounds.