Airway transplantation: a challenge for regenerative medicine

Long-Term Survival and Regeneration Following Transplantation of 3D-Printed Biodegradable PCL Tracheal Grafts in Large-Scale Porcine Models

Polycaprolactone (PCL) implants in large animals show great promise for tracheal transplantation. However, the longest survival time achieved to date is only about three weeks. To meet clinical application standards, it is essential to extend the survival time and ensure the complete integration and functionality of the implant. Our study investigates the use of three-dimensional (3D)-printed, biodegradable, PCL-based tracheal grafts for large-scale porcine tracheal transplantation, assessing the feasibility and early structural integrity crucial for long-term survival experiments. A biodegradable PCL tracheal graft was fabricated using a BIOX bioprinter and transplanted into large-scale porcine models. The grafts, measuring 20 × 20 × 1.5 mm, were implanted following a 2 cm circumferential resection of the porcine trachea. The experiment design was traditionally implanted in eight porcines to replace four-ring tracheal segments, only two of which survived more than three months. Data were collected on the graft construction and clinical outcomes. The 3D-printed biosynthetic grafts replicated the native organ with high fidelity. The implantations were successful, without immediate complications. At two weeks, bronchoscopy revealed significant granulation tissue around the anastomosis, which was managed with laser ablation. The presence of neocartilage, neoglands, and partial epithelialization near the anastomosis was verified in the final pathology findings. Our study demonstrates in situ regenerative tissue growth with intact cartilage following transplantation, marked by neotissue formation on the graft's exterior. The 90-day survival milestone was achieved due to innovative surgical strategies, reinforced with strap muscle attached to the distal trachea. Further improvements in graft design and granulation tissue management are essential to optimize outcomes.

Alginate Improves the Chondrogenic Capacity of 3D PCL Scaffolds In Vitro: A Histological Approach

Polycaprolactone (PCL) scaffolds have demonstrated an effectiveness in articular cartilage regeneration due to their biomechanical properties. On the other hand, alginate hydrogels generate a 3D environment with great chondrogenic potential. Our aim is to generate a mixed PCL/alginate scaffold that combines the chondrogenic properties of the two biomaterials. Porous PCL scaffolds were manufactured using a modified salt-leaching method and embedded in a culture medium or alginate in the presence or absence of chondrocytes. The chondrogenic capacity was studied in vitro. Type II collagen and aggrecan were measured by immunofluorescence, cell morphology by F-actin fluorescence staining and gene expression of COL1A1, COL2A1, ACAN, COL10A1, VEGF, RUNX1 and SOX6 by reverse transcription polymerase chain reaction (RT-PCR). The biocompatibility of the scaffolds was determined in vivo using athymic nude mice and assessed by histopathological and morphometric analysis. Alginate improved the chondrogenic potential of PCL in vitro by increasing the expression of type II collagen and aggrecan, as well as other markers related to chondrogenesis. All scaffolds showed good biocompatibility in the in vivo model. The presence of cells in the scaffolds induced an increase in vascularization of the PCL/alginate scaffolds. The results presented here reinforce the benefits of the combined use of PCL and alginate for the regeneration of articular cartilage.

Airway replacement using stented aortic matrices: Long-term follow-up and results of the TRITON-01 study in 35 adult patients

Over the past 25 years, we have demonstrated the feasibility of airway bioengineering using stented aortic matrices experimentally then in a first-in-human trial (n = 13). The present TRITON-01 study analyzed all the patients who had airway replacement at our center to confirm that this innovative approach can be now used as usual care. For each patient, the following data were prospectively collected: postoperative mortality and morbidity, late airway complications, stent removal and status at last follow-up on November 2, 2021. From October 2009 to October 2021, 35 patients had airway replacement for malignant (n = 29) or benign (n = 6) lesions. The 30-day postoperative mortality and morbidity rates were 2.9% (n = 1/35) and 22.9% (n = 8/35) respectively. At a median follow-up of 29.5 months (range 1-133 months), 27 patients were alive. There have been no deaths directly related to the implanted bioprosthesis. Eighteen patients (52.9%) had stent-related granulomas requiring a bronchoscopic treatment. Ten among 35 patients (28.6%) achieved a stent free survival. The actuarial 2- and 5-year survival rates (Kaplan-Meier estimates) were respectively 88% and 75%. The TRITON-01 study confirmed that airway replacement using stented aortic matrices can be proposed as usual care at our center. Clinicaltrials.gov Identifier: NCT04263129.

Current Strategies for Tracheal Replacement: A Review

Airway cancers have been increasing in recent years. Tracheal resection is commonly performed during surgery and is burdened from post-operative complications severely affecting quality of life. Tracheal resection is usually carried out in primary tracheal tumors or other neoplasms of the neck region. Regenerative medicine for tracheal replacement using bio-prosthesis is under current research. In recent years, attempts were made to replace and transplant human cadaver trachea. An effective vascular supply is fundamental for a successful tracheal transplantation. The use of biological scaffolds derived from decellularized tissues has the advantage of a three-dimensional structure based on the native extracellular matrix promoting the perfusion, vascularization, and differentiation of the seeded cell typologies. By appropriately modulating some experimental parameters, it is possible to change the characteristics of the surface. The obtained membranes could theoretically be affixed to a decellularized tissue, but, in practice, it needs to ensure adhesion to the biological substrate and/or glue adhesion with biocompatible glues. It is also known that many of the biocompatible glues can be toxic or poorly tolerated and induce inflammatory phenomena or rejection. In tissue and organ transplants, decellularized tissues must not produce adverse immunological reactions and lead to rejection phenomena; at the same time, the transplant tissue must retain the mechanical properties of the original tissue. This review describes the attempts so far developed and the current lines of research in the field of tracheal replacement.

Feasibility of in situ chondrogenesis for the entire umbilical cord in preliminary preparation for tracheal graft

BACKGROUND

There remains a scarcity of both autografts and allografts for tracheal transplantation after long-segmental resection. Subsequently, tissue engineering has become a promising alternative for tracheal transplantation, which requires successful in vitro chondrogenesis.

METHODS

To optimize the protocol for in situ chondrogenesis using the pig-derived whole Umbilical Cord (UC) as the starting material, it must be performed without using the UC-multipotent stromal cell (MSCs) isolation procedure. Nevertheless, chondrogenic induction is performed under a variety of conditions; with or without TGF-β1 at different concentrations, and also in combination with either a rotatory or hollow organ bioreactor. The engineered explant sections were analyzed using various histochemical and immunohistochemical stains to assess the expression of chondrocyte markers. Cell viability was determined through use of the APO-BrdU TUNEL assay kit.

RESULTS

The results showed that culture conditions induced heterogeneous chondrogenesis in various compartments of the UC. Moreover, explants cultured with 10 ng/ml TGF-β1 under hypoxic (1% O₂) in combination with a bioreactor, significantly enhanced the expression of aggrecan and type II collagen, but were lacking in the production of Glycosaminoglycans (GAGs), as evidenced by alcian blue staining. We speculated that whole segment UCs allowed for the differentiation into premature chondrocytes in our tissue-engineered environments.

CONCLUSION

This study has provided exciting preliminary evidence showing that a stem cell-rich UC wrapped around an anatomical tracheal scaffold and implanted in vivo can induce nodes of new cartilage growth into a structurally functional tissue for the repairing of long-segmental tracheal stenosis.

Bioengineered carina reconstruction using In-Vivo Bioreactor technique in human: proof of concept study

Backgrounds

Long-segment airway defect reconstruction, especially when carina is invaded, remains a challenge in clinical setting. Previous attempts at bioengineered carina reconstruction failed within 90 days due to delayed revascularization and recurrent infection.

Methods

To establish the feasibility of carina bioengineering use In-Vivo Bioreactor technique. Uncontrolled single-center cohort study including three patients with long-segment airway lesions invading carina. Radical resection of the lesions was performed using standard surgical techniques. After resection, In-Vivo Bioreactor airway reconstruction was performed using a nitinol stent wrapped in two layers of acellularized dermis matrix (ADM). Two Port-a-Cath catheters connected to two portable peristaltic pumps were inserted between the ADM layers. The implanted bioengineered airway was continuously perfused with an antibiotic solution via the pump system. Peripheral total nucleated cells (TNCs) were harvested and seeded into the airway substitute via a Port-a-Cath twice a week for 1 month. The patients were treated as a bioreactor for in situ regeneration of their own bioengineered airway substitute.

Results

Three patients were included in the study (mean age, 54.7 years). The first patient underwent 8 cm long trachea and carina reconstruction, the second patient 6 cm long trachea, carina and main bronchus reconstruction. The third patient right main bronchus and carina reconstruction. Major morbidity included gastric retention and pneumonia. All three patients survived till last follow-up and bronchoscopy follow-up showed well-vascularized regenerated tissue without leakage.

Conclusions

In this uncontrolled study, In-Vivo Bioreactor technique demonstrated potential to be applied for long-segment trachea, carina and bronchi reconstruction. Further research is needed to assess efficacy and safety.

Airway regeneration using iPS cell-derived airway epithelial cells with Cl- channel function

induced pluripotent stem (iPS) cells can be differentiated into various cell types, including airway epithelial cells, since they have the capacity for self-renewal and pluripotency. Thus, airway epithelial cells generated from iPS cells are expected to be potent candidates for use in airway regeneration and the treatment of airway diseases such as cystic fibrosis (CF). Recently, it was reported that iPS cells can be differentiated into airway epithelial cells according to the airway developmental process. These studies demonstrate that airway epithelial cells generated from iPS cells are equivalent to their in vivo counterparts. However, it has not been evaluated in detail whether these cells exhibit physiological functions and are fully mature. Airway epithelial cells adequately control water volume on the airway surface via the function of Cl⁻ channels. Reasonable environments on the airway surface cause ciliary movement with a constant rhythm and maintain airway clearance. Therefore, the generation of functional airway epithelial cells/tissues with Cl⁻ channel function from iPS cells will be indispensable for cell/tissue replacement therapy, the development of a reliable airway disease model, and the treatment of airway disease. This review highlights the generation of functional airway epithelial cells from iPS cells and discusses the remaining challenges to the generation of functional airway epithelial cells for airway regeneration and the treatment of airway disease.

Functional characterization of various channel-expressing central airway epithelial cells from mouse induced pluripotent stem cells

Functional central airway epithelial cells (CAECs) from induced pluripotent stem cells (iPSCs) are an attractive potential cell source for central airway regeneration. The central airway epithelium, such as the tracheal epithelium, is composed of ciliated cells, goblet cells, and basal cells and has physiologically important functions such as the regulation of water volume on the airway surface by Cl^- and water channels and the elimination of particles inhaled from the external environment by ciliary movement. Previous work from our group and from other research groups has reported the generation of airway epithelial cells from iPSCs. However, it remains unclear whether iPSC-derived CAECs express the various channels that are required for the regulation of water volume on the airway surface and whether these channels function properly. In this study, we generated CAECs from iPSCs supplemented with activin and bFGF using air-liquid interface culture. We then evaluated the physiological functioning of the iPSC-derived CAECs by examining the gene expression and transport functions of Cl ^- channels using a halide ion-sensitive yellow fluorescent protein and ciliary movement. Reverse-transcription polymerase chain reaction and immunohistochemistry indicated that various channel markers such as cystic fibrosis transmembrane conductance regulator (CFTR) and aquaporin (AQP) were present in iPSC-derived CAECs. Furthermore, the transport functions of Cl ^- channels and CFTR were successfully confirmed. Finally, ciliary movement was measured, and a ciliary beating frequency (CBF) of approximately 10 Hz was observed. These results demonstrate that CAECs generated by our method have physiological functions similar to those of native CAECs.

Tracheal Replacement Therapy with a Stem Cell-Seeded Graft: Lessons from Compassionate Use Application of a GMP-Compliant Tissue-Engineered Medicine

Tracheal replacement for the treatment of end‐stage airway disease remains an elusive goal. The use of tissue‐engineered tracheae in compassionate use cases suggests that such an approach is a viable option. Here, a stem cell‐seeded, decellularized tissue‐engineered tracheal graft was used on a compassionate basis for a girl with critical tracheal stenosis after conventional reconstructive techniques failed. The graft represents the first cell‐seeded tracheal graft manufactured to full good manufacturing practice (GMP) standards. We report important preclinical and clinical data from the case, which ended in the death of the recipient. Early results were encouraging, but an acute event, hypothesized to be an intrathoracic bleed, caused sudden airway obstruction 3 weeks post‐transplantation, resulting in her death. We detail the clinical events and identify areas of priority to improve future grafts. In particular, we advocate the use of stents during the first few months post‐implantation. The negative outcome of this case highlights the inherent difficulties in clinical translation where preclinical in vivo models cannot replicate complex clinical scenarios that are encountered. The practical difficulties in delivering GMP grafts underscore the need to refine protocols for phase I clinical trials. Stem Cells Translational Medicine2017;6:1458–1464

Porous decellularized trachea scaffold prepared by a laser micropore technique

Rapid development of tissue engineering technology provides new methods for tracheal cartilage regeneration. However, the current lack of an ideal scaffold makes engineering of trachea cartilage tissue into a three-dimensional (3-D) tubular structure a great challenge. Although a decellularized trachea matrix (DTM) has become a recognized scaffold for trachea cartilage regeneration, it is difficult for cells to detach from or penetrate the matrix because of its non-porous structure. To tackle these problems, a laser micropore technique (LMT) was applied in the current study to enhance trachea sample porosity, and facilitate decellularizing treatment and cell ingrowth. Furthermore, after optimizing LMT and decellularizing treatment parameters, LMT-treated DTM (LDTM) retained its natural tubular structure with only minor extracellular matrix damage. Moreover, compared with DTM, the current study showed that LDTM significantly improved the adherence rate of cells with perfect cell biocompatibility. Moreover, the optimal implantation cell density for chondrogenesis with LDTM was determined to be 1 × 10⁸ cells/ml. Collectively, the results suggest that the novel LDTM is an ideal scaffold for trachea tissue engineering.

Aortic allografts: final destination?-a summary of clinical tracheal substitutes

The patient population in desperate need for an airway substitute are individuals with long segment tracheal defects that are considered, technically, inoperable. Regardless of the underlying etiology, benign or malignant growing processes, this patient category enters a palliative setting or require tracheal transplantation. Different airway substitutes have been categorized by Grillo as follows; tracheal transplantation, autogenous tissue, non-viable tissue, tissue-engineering and foreign materials. These fields have been explored in the past in animal models and in clinical patients. Research on airway replacement has been exposed to a level of controversies in the past years. The field has been turbulent and apocryphal. In particular, the area of tissue-engineering using stem cells has suffered from a major set-back leaving scientists, clinicians and ethical committees skeptical. Recently, a hopeful study emerged using aortic allografts as tracheal substitutes in patients with airway defects. The initial results seem promising and reliable. The developments of the field at this point seem striking and hopeful. The focus of this review is to shed light on developments in the field of aortic allografts as substitute for tracheal replacement.

Feasibility of Bioengineered Tracheal and Bronchial Reconstruction Using Stented Aortic Matrices

IMPORTANCE

Airway transplantation could be an option for patients with proximal lung tumor or with end-stage tracheobronchial disease. New methods for airway transplantation remain highly controversial.

OBJECTIVE

To establish the feasibility of airway bioengineering using a technique based on the implantation of stented aortic matrices.

DESIGN, SETTING, AND PARTICIPANTS

Uncontrolled single-center cohort study including 20 patients with end-stage tracheal lesions or with proximal lung tumors requiring a pneumonectomy. The study was conducted in Paris, France, from October 2009 through February 2017; final follow-up for all patients occurred on November 2, 2017.

EXPOSURES

Radical resection of the lesions was performed using standard surgical techniques. After resection, airway reconstruction was performed using a human cryopreserved (-80°C) aortic allograft, which was not matched by the ABO and leukocyte antigen systems. To prevent airway collapse, a custom-made stent was inserted into the allograft. In patients with proximal lung tumors, the lung-sparing intervention of bronchial transplantation was used.

MAIN OUTCOMES AND MEASURES

The primary outcome was 90-day mortality. The secondary outcome was 90-day morbidity.

RESULTS

Twenty patients were included in the study (mean age, 54.9 years; age range, 24-79 years; 13 men [65%]). Thirteen patients underwent tracheal (n = 5), bronchial (n = 7), or carinal (n = 1) transplantation. Airway transplantation was not performed in 7 patients for the following reasons: medical contraindication (n = 1), unavoidable pneumonectomy (n = 1), exploratory thoracotomy only (n = 2), and a lobectomy or bilobectomy was possible (n = 3). Among the 20 patients initially included, the overall 90-day mortality rate was 5% (1 patient underwent a carinal transplantation and died). No mortality at 90 days was observed among patients who underwent tracheal or bronchial reconstruction. Among the 13 patients who underwent airway transplantation, major 90-day morbidity events occurred in 4 (30.8%) and included laryngeal edema, acute lung edema, acute respiratory distress syndrome, and atrial fibrillation. There was no adverse event directly related to the surgical technique. Stent removal was performed at a postoperative mean of 18.2 months. At a median follow-up of 3 years 11 months, 10 of the 13 patients (76.9%) were alive. Of these 10 patients, 8 (80%) breathed normally through newly formed airways after stent removal. Regeneration of epithelium and de novo generation of cartilage were observed within aortic matrices from recipient cells.

CONCLUSIONS AND RELEVANCE

In this uncontrolled study, airway bioengineering using stented aortic matrices demonstrated feasibility for complex tracheal and bronchial reconstruction. Further research is needed to assess efficacy and safety.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01331863.

Tracheal Replacement Therapy with a Stem Cell-Seeded Graft: Lessons from Compassionate Use Application of a GMP-Compliant Tissue-Engineered Medicine

Tracheal replacement for the treatment of end-stage airway disease remains an elusive goal. The use of tissue-engineered tracheae in compassionate use cases suggests that such an approach is a viable option. Here, a stem cell-seeded, decellularized tissue-engineered tracheal graft was used on a compassionate basis for a girl with critical tracheal stenosis after conventional reconstructive techniques failed. The graft represents the first cell-seeded tracheal graft manufactured to full good manufacturing practice (GMP) standards. We report important preclinical and clinical data from the case, which ended in the death of the recipient. Early results were encouraging, but an acute event, hypothesized to be an intrathoracic bleed, caused sudden airway obstruction 3 weeks post-transplantation, resulting in her death. We detail the clinical events and identify areas of priority to improve future grafts. In particular, we advocate the use of stents during the first few months post-implantation. The negative outcome of this case highlights the inherent difficulties in clinical translation where preclinical in vivo models cannot replicate complex clinical scenarios that are encountered. The practical difficulties in delivering GMP grafts underscore the need to refine protocols for phase I clinical trials. Stem Cells Translational Medicine 2017;6:1458-1464.

In Vivo Tissue Engineering of Human Airways

BACKGROUND

Airway transplantation remains a major challenge in thoracic surgery. Based on our previous laboratory work, we developed the techniques required to bioengineer a tracheal substitute in vivo using cryopreserved aortic allografts as biological matrices (Replacement of the Airways and/or the Pulmonary Vessels Using a Cryopreserved Arterial Allograft [TRACHEOBRONCART] Study, NCT01331863). We present here 2 patients who had a definitive tracheostomy for complex laryngotracheal stenoses refractory to conventional therapy.

METHODS

According to our protocol, a stented gender-mismatched -80°C cryopreserved aortic allograft was used for airway reconstruction. Follow-up assessments were done at regular intervals using clinical, imaging, and endoscopic evaluations. Immunohistochemical and XX/XY chimerism studies were performed at time of stent removal using graft biopsy specimens. Chemotactic and angiogenic properties of implanted matrices were also investigated.

RESULTS

At a maximal follow-up of 5 years and 7 months, the patients were breathing and speaking normally, without tracheostomy or stent. Regeneration of cartilage within the aortic grafts was demonstrated by positive immunodetection of type II collagen and markers specific for Sox9. Chimerism study from samples of neotissues demonstrated that regenerated cartilage came from recipient cells. The remaining viable matrix cells released a functionally relevant amount of proangiogenic, chemoattractant, proinflammatory/immunomodulatory cytokines, and growth factors.

CONCLUSIONS

This report documents the feasibility of in vivo tissue engineering for long-term functional airway transplantation in humans.

Small bowel in vivo bioengineering using an aortic matrix in a porcine model

OBJECTIVE

To evaluate the feasibility of an in vivo small bowel bioengineering model using allogeneic aortic grafts in pigs.

BACKGROUND

The best treatment for short bowel syndrome is still unclear. Intestinal transplantation, as well as lifelong parenteral nutrition is associated with a 5-year survival rate of less than 50 %. We have already used allogeneic arterial segments to replace the upper airway in sheep. The results were encouraging with an induced transformation of the aortic wall into tracheo-bronchial bronchial-type tissue.

METHODS

Seven young mini-pigs were used. A 10-cm-diameter, allogeneic, aortic graft was interposed in an excluded small bowel segment and wrapped by the neighboring omentum. Animals were autopsied at 1 (n = 2), 3 (n = 3), and 6 months (n = 2), respectively. Specimens were examined macroscopically and microscopically.

RESULTS

The overall survival rate of the animals was 71.4 %. No anastomotic leak occurred. Histologic analysis revealed intestinal-like wall transformation of the aortic graft in the surviving animals.

CONCLUSION

Aortic-enteric anastomosis is feasible in a porcine model. Moreover, in vivo, bioengineered, intestinal-like transformation of the vascular wall was identified.

Is Tracheal Transplantation Possible With Cryopreserved Tracheal Allograft and Hyperbaric Oxygen Therapy? An Experimental Study

BACKGROUND

Allografts have achieved prominence for tracheal reconstruction because of their natural physiologic and anatomic structure, which preserves respiratory tract flexibility and lumen patency. The immunomodulatory effects of cryopreservation prevent tracheal allograft rejection. In addition, hyperbaric oxygen therapy (HBOT) accelerates wound healing by promoting epithelization and neovascularization. This experimental study investigated the early and late effects of HBOT on cryopreserved tracheal allografts (CTAs).

METHODS

The study used 33 outbred Wistar rats weighing 300 to 350 g as allograft transplantation donors and recipients. Among these, 22 recipient rats were randomly assigned to the HBOT (n = 11) and control (n = 11) groups. Rats in the HBOT group were treated with 100% oxygen for 60 minutes at 2.5 atmospheres of absolute pressure for 7 days. Recipient rats in both groups were euthanized at 1 week (n = 5) and 4 weeks (n = 6) after transplantation, defined as the early and late periods, respectively.

RESULTS

In the early period, no significant histopathologic differences were observed between groups (p > 0.05). However, microscopic evaluation of the control group during the late period showed low epithelization of the CTA. In contrast, microscopic evaluation of the HBOT group during this same period revealed epithelium covering the transplanted CTA lumen. Significant epithelization and vascularization and significantly reduced inflammation and fibrosis were found in the HBOT group compared with the control group (p < 0.05).

CONCLUSIONS

HBOT may be effective in tracheal reconstruction by increasing epithelization and neovascularization after extended tracheal resection. HBOT, therefore, should be considered in CTA transplantation.

Seeding of recipient-originated epithelial cells attenuates epithelial to mesenchymal transition in rat tracheal allotransplantation

OBJECTIVE

The specific role and mechanism of epithelium in the progression of obliterative airway disease (OAD) after tracheal allotransplantation remain poorly understood. In this study, we used rat heterotopic tracheal transplantation to investigate the mechanism of epithelial cell seeding during the process of OAD.

STUDY DESIGN

Prospective, basic science.

SETTING

Research laboratory.

SUBJECTS AND METHODS

In total, 120 Sprague Dawley (SD) rats and 90 Wistar rats were used. Tracheas from SD rats were implanted into SD rats (syngeneic, n = 30) or Wistar rats (allogeneic, n = 30), and SD rat tracheas (seeded with Wistar rat-derived epithelial cells 6 days after transplantation) were transplanted into Wistar rats (seeded allogeneic, n = 30). Grafts were harvested at 7, 14, or 30 days after transplantation for histologic, quantitative reverse transcriptional polymerase chain reaction or Western blot analyses.

RESULTS

Syngrafts retained normal histologic structures, while the corresponding allografts demonstrated less ciliated epithelia and more lumenal occlusion. Seeding of epithelial cells ameliorated the histologic changes, reduced the expression of epithelial to mesenchymal transition (EMT)-related transcriptional factors and mesenchymal markers, and dampened the expression of transforming growth factor β1 (TGF-β1) and phosphorylation of smad3.

CONCLUSION

Seeding of recipient epithelial cells inhibits the progression of OAD by attenuating EMT via TGF-β-Smad signaling in rat heterotopic tracheal allografts. Clinically, the injection of recipient-originated epithelial cells might provide new insights into the treatment for OAD after tracheal allotransplantation.

Coupled cellular therapy and magnetic targeting for airway regeneration

Airway diseases including COPD (chronic obstructive pulmonary disease), cystic fibrosis and lung cancer are leading causes of worldwide morbidity and mortality, with annual healthcare costs of billions of pounds. True regeneration of damaged airways offers the possibility of restoring lung function and protecting against airway transformation. Recently, advances in tissue engineering have allowed the development of cadaveric and biosynthetic airway grafts. Although these have produced encouraging results, the ability to achieve long-term functional airway regeneration remains a major challenge. To promote regeneration, exogenously delivered stem and progenitor cells are being trialled as cellular therapies. Unfortunately, current evidence suggests that only small numbers of exogenously delivered stem cells engraft within lungs, thereby limiting their utility for airway repair. In other organ systems, magnetic targeting has shown promise for improving long-term robust cell engraftment. This technique involves in vitro cell expansion, magnetic actuation and magnetically guided cell engraftment to sites of tissue damage. In the present paper, we discuss the utility of coupling stem cell-mediated cellular therapy with magnetic targeting for improving airway regeneration.

Tracheal bioengineering: the next steps. Proceeds of an International Society of Cell Therapy Pulmonary Cellular Therapy Signature Series Workshop, Paris, France, April 22, 2014

There has been significant and exciting recent progress in the development of bioengineering approaches for generating tracheal tissue that can be used for congenital and acquired tracheal diseases. This includes a growing clinical experience in both pediatric and adult patients with life-threatening tracheal diseases. However, not all of these attempts have been successful, and there is ongoing discussion and debate about the optimal approaches to be used. These include considerations of optimal materials, particularly use of synthetic versus biologic scaffolds, appropriate cellularization of the scaffolds, optimal surgical approaches and optimal measure of both clinical and biologic outcomes. To address these issues, the International Society of Cell Therapy convened a first-ever meeting of the leading clinicians and tracheal biologists, along with experts in regulatory and ethical affairs, to discuss and debate the issues. A series of recommendations are presented for how to best move the field ahead.