Transplantation of Autologous Chondrocytes Seeded on a Fibrin/Hyaluronan Composite Gel Into Tracheal Cartilage Defects in Rabbits: Preliminary Results

Reconstruction of tracheal defects is one of the most difficult procedures in head and neck surgery. To date, various reconstructing techniques have been used with no consensus on the best approach. This study investigated the feasibility of using a fibrin/hyaluronic acid (HA) composite gel with autologous chondrocytes for tracheal reconstruction. Chondrocytes from autologous rabbit auricular cartilages were expanded and seeded into a culture dish at high density to form stable tracheal cartilages mechanically using a fibrin/HA composite gel. A 1‐cm long by 0.5‐cm wide defect was created by a scalpel on the cervical tracheae of six rabbits. Tissue‐engineered cartilages using fibrin/HA composite were trimmed and fixed to the defect boundaries with tissuecol. Postoperatively, the site was evaluated endoscopically, histologically, radiologically, and functionally. None of the six rabbits showed signs of respiratory distress. Postoperatively, in all cases, rigid telescopic examination showed that the implanted scaffolds were completely covered with regenerated mucosa without granulation or stenosis. Histologically, the grafts showed no signs of inflammatory reaction and were covered with ciliated epithelium. Even when grafts were broken and migrated from their original insertion site, the implanted cartilages were well preserved. However, the grafts did show signs of mechanical failure at the implantation site. The beat frequency of ciliated epithelium on implants was very similar to that of normal respiratory mucosa. In conclusion, implants with autologous chondrocytes cultured with fibrin/HA showed good tracheal luminal contour, functional epithelial regeneration, and preservation of neocartilage without inflammation but lacked adequate mechanical stability.     

Tissue engineering of trachea-like cartilage grafts by using chondrocyte macroaggregate: experimental study in rabbits

Abstract:  Treatment and management of tracheal defects remain challenges in head and neck surgery. The purposes of this study were to explore a novel strategy to fabricate tissue-engineered trachea by using chondrocyte macroaggregate, and evaluate the feasibility of creating tracheal cartilage equivalents grown in the shape of cylindrical structure without scaffold. Chondrocytes from rabbit cartilage were expanded and seeded into a culture dish at high density to form mechanically stable chondrocyte macroaggregate. Once the chondrocyte macroaggregate was harvested by scrapping technique, it was wrapped around a silicon tube and implanted subcutaneously into the cell donor rabbit. Eight weeks later, specimens were harvested and analyzed for gross appearance, and histological, biochemical, and biomechanical properties. These values were compared with native rabbit cartilage. It was found that expanded chondrocytes could be harvested as a coherent cellular macroaggregate and could be fabricated into a tubelike graft. After in vivo implantation, cartilage-like tissue with cylindrical structure was regenerated successfully. Histological analysis showed engineered trachea cartilage consisted of evenly spaced lacunae embedded in a matrix rich in proteoglycans; type II collagen was also highly expressed in this engineered trachea cartilage. In a conclusion, based on the chondrocyte macroaggregate strategy, tracheal cartilage equivalents with cylindrical shape could be successfully reconstructed. This construct has advantages of high cell-seeding efficiency, good nutritional perfusion, and minimal inflammatory reaction, which provided a highly effective cartilage graft substitute and could be useful in many situations of trachea–cartilage loss encountered in clinical practice.     

PLGA–PTMC–Cultured Bone Mesenchymal Stem Cell Scaffold Enhances Cartilage Regeneration in Tissue‐Engineered Tracheal Transplantation

The treatment of long‐segment tracheal defect requires the transplantation of effective tracheal substitute, and the tissue‐engineered trachea (TET) has been proposed as an ideal tracheal substitute. The major cause of the failure of segmental tracheal defect reconstruction by TET is airway collapse caused by the chondromalacia of TET cartilage. The key to maintain the TET structure is the regeneration of chondrocytes in cartilage, which can secrete plenty of cartilage matrices. To address the problem of the chondromalacia of TET cartilage, this study proposed an improved strategy. We designed a new cell sheet scaffold using the poly(lactic‐co‐glycolic acid) (PLGA) and poly(trimethylene carbonate) (PTMC) to make a porous membrane for seeding cells, and used the PLGA–PTMC cell‐scaffold to pack the decellularized allogeneic trachea to construct a new type of TET. The TET was then implanted in the subcutaneous tissue for vascularization for 2 weeks. Orthotopic transplantation was then performed after implantation. The efficiency of the TET we designed was analyzed by histological examination and biomechanical analyses 4 weeks after surgery. Four weeks after surgery, both the number of chondrocytes and the amount of cartilage matrix were significantly higher than those contained in the traditional stem‐cell–based TET. Besides, the coefficient of stiffness of TET was significantly larger than the traditional TET. This study provided a promising approach for the long‐term functional reconstruction of long‐segment tracheal defect, and the TET we designed had potential application prospects in the field of TET reconstruction.     

An animal model study for tissue-engineered trachea fabricated from a biodegradable scaffold using chondrocytes to augment repair of tracheal stenosis

Introduction

We have designed an engineered graft fabricated from a biodegradable scaffold using chondrocytes and applied this construct to augment repair of tracheal stenosis. This study investigated the feasibility of using such tissue-engineered airways with autologous chondrocytes in a rabbit model.

Material and Methods

Chondrocytes were isolated and expanded from the auricular cartilage of New Zealand white rabbits, then seeded onto composite 3-layer scaffolds consisting of a collagen sheet, a polyglycolic acid mesh, and a copolymer (l-lactide/?-caprolactone) coarse mesh. The engineered grafts were implanted into a 0.5 × 0.8-cm defect created in the midventral portion of the cervical trachea. Gelatin sponges that slowly released basic fibroblast growth factor (b-FGF) were then placed on the constructs, which were retrieved 1 or 3 months after implantation.

Results

The biodegradable scaffold seeded with chondrocytes could maintain airway structure up to 3 months after implantation. Tracheal epithelial regeneration occurred in the internal lumen of this composite scaffold. Three months after implantation, staining of the sections showed cartilage accumulation in the engineered tracheal wall.

Conclusion

This composite biodegradable scaffold may be useful for developing engineered trachea. A gelatin sponge slowly releasing b-FGF might enhance chondrogenesis.     

Tracheal reconstruction with autogenous jejunal microsurgical transfer

Tracheal defects due to stricture formation, tracheomalacia, and neoplasms can present difficult reconstructive problems. Tracheal defects were surgically created in 6 dogs and primarily reconstructed with microsurgical free tissue transfer of autogenous jejunal segments. Primary healing was accomplished in all dogs without severe air leakage or infection. Bronchoscopy demonstrated no substantial secretions or tracheal narrowing. Gross pathological examination of the trachea revealed no evidence of tracheal disruption or infection. Direct measurements revealed no major tracheal narrowing. Microscopic examination demonstrated normal jejunal mucosa with a minimal amount of inflammatory change at the margins of the reconstruction at 6 weeks. Microvascular free tissue transfer of jejunal segments to correct cervical tracheal defects can readily be accomplished with excellent healing and maintenance of the tracheal lumen in dogs.     

Role of autologous rabbit adipose‐derived stem cells in the early phases of the repairing process of critical bone defects

Adipose‐derived stem cells (ASCs) may represent a novel and efficient tool to promote bone regeneration. In this study, rabbit ASCs were expanded in culture and used for the regeneration of full‐thickness bone defects in the proximal epiphysis of tibia of 12 New Zealand rabbits. Defects were implanted with graft material as follows: untreated (control), empty hydroxyapatite (HA) disk, ASCs alone, and HA disk seeded with ASCs. Each isolated ASCs population was tested in vitro: they all showed a high proliferation rate, a marked clonogenic ability, and osteogenic differentiation potential. Eight weeks after implantation, macroscopic analyses of all the samples showed satisfactory filling of the lesions without any significant differences in term of stiffness between groups treated with or without cells (p > 0.05). In both the scaffold‐treated groups, a good osteointegration was radiographically observed. Even if HA was not completely reabsorbed, ASCs‐loaded HA displayed a higher scaffold resorption than the unloaded ones. Histological analyses showed that the osteogenic abilities of the scaffold‐treated defects was greater than those of scaffold‐free samples, and in particular new formed bone was more mature and more similar to native bone in presence of ASCs. These results demonstrated that autologous ASCs–HA constructs is a potential treatment for the regeneration of bone defects. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:100–108, 2011     

重组人骨形态发生蛋白2/脱细胞骨基质材料复合移植修复兔骨缺损的研究

目的观察重组人骨形态发生蛋白2/脱细胞骨基质材料(rhBMP2/ACBM)对体外培养的骨髓基质细胞(MSCs)增殖和分化的影响及兔桡骨骨缺损的修复作用。方法在制备rhBMP2/ACBM复合缓释载体的基础上,取培养第3代MSCs种植到材料上,体外培养4～7d,观察MSCs的增殖及碱性磷酸酶(AKP)、骨钙素的表达;将自体MSCs材料复合培养后24h回植到骨缺损局部,同期观察复合材料及空白对照组,分别于4、8、12周,通过X线、单光子放射计算机断层显象术(SPECT)、及组织学方法评价其对骨缺损的修复效果。结果与单纯体外培养组比较,复合载体在体外对MSCs具有成骨细胞诱导作用,而对细胞增殖无影响。与复合载体植入组比较,细胞材料复合植入组,4周时成骨量明显增多(P<0.05),且12周新骨塑型好。结论复合载体具有良好的体内外诱导成骨作用,细胞载体复合植入对骨缺损修复效果良好。     

镍钛记忆合金气管腔内支架的实验研究

报告采用记忆合金支架治疗气管软化的实验研究，７条犬造成气管软化模型后，将支架置入软化部位。气道阻力测定结果表明，该支架能有效地克服气道软化，观察２～６个月，支架全部发生移位。向近端移位的３条犬，最终全部出现肉芽组织增生，阻塞管腔，向远端移位的４条犬中有３条出现理想的结果，即正常气管上皮爬过重建光滑的气管腔，支架的合金丝逐渐被纤维包膜所包绕，作者认为：对于临床上没有理想治疗方法的远端气管软化，该方法     

Repair of Critical‐Sized Long Bone Defects Using Dipyridamole‐Augmented 3D‐Printed Bioactive Ceramic Scaffolds

There are over two million long bone defects treated in the United States annually, of which ~5% will not heal without significant surgical intervention. While autogenous grafting is the standard of care in simple defects, a customized scaffold for large defects in unlimited quantities is not available. Recently, a three‐dimensionally (3D)‐printed bioactive ceramic (3DPBC) scaffold has been successfully utilized in the of repair critical‐sized (CSD) long bone defects in vivo. In this study, 3DPBC scaffolds were augmented with dipyridamole (DIPY), an adenosine A2A receptor (A_2AR) indirect agonist, because of its known effect to enhance bone formation. CSD full thickness segmental defects (~11 mm × full thickness) defects were created in the radial diaphysis in New Zealand white rabbits (n = 24). A customized 3DPBC scaffold composed of β‐tricalcium phosphate was placed into the defect site. Groups included scaffolds that were collagen‐coated (COLL), or immersed in 10, 100, or 1,000 μM DIPY solution. Animals were euthanized 8 weeks post‐operatively and the radii/ulna‐scaffold complex retrieved en bloc, for micro‐CT, histological, and mechanical analysis. Bone growth was assessed exclusively within scaffold pores and evaluated by microCT and advanced reconstruction software. Biomechanical properties were evaluated utilizing nanoindentation to assess the newly regenerated bone for elastic modulus (E) and hardness (H). MicroCT reconstructions illustrated bone in‐growth throughout the scaffold, with an increase in bone volume dependent on the DIPY dosage. The histological evaluation did not indicate any adverse immune response while revealing progressive remodeling of bone. These customized biologic 3DPBC scaffolds have the potential of repairing and regenerating bone. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2499–2507, 2019     

Tracheal wall for the reconstruction of extended hemilaryngectomy in the rabbit model.

OBJECTIVE: To evaluate reconstruction of the surgical wound of extended hemilaryngectomy using the tracheal wall. STUDY DESIGN AND SETTING: Prospective, nonrandomized experimental study in a rabbit model in which cricothyroid hemilaryngectomy was performed in 10 rabbits. The proximal trachea was tailored to cover the surgical wound and sutured to it. The ipsilateral lobe of the thyroid gland and the medial thyroid vascular pedicle were conserved so as to assure vascular supply to the tracheal flap. After 4 weeks the animals were sacrificed and pathology analysis conducted. RESULTS: Eight of the 10 rabbits survived without respiratory or deglutitory alterations. Pathologic analysis showed well-healed suture lines together with normal mucosa and cartilage rings in the tracheal flap. CONCLUSIONS: The tracheal wall appears to be the ideal donor tissue for repair of the larynx. SIGNIFICANCE: This simple, 1-session surgical procedure demonstrates an effective reconstruction of an extended hemilaryngectomy wound.     

Tissue‐Engineered Tracheal Replacement in a Child: A 4‐Year Follow‐Up Study

In 2010, a tissue‐engineered trachea was transplanted into a 10‐year‐old child using a decellularized deceased donor trachea repopulated with the recipient's respiratory epithelium and mesenchymal stromal cells. We report the child's clinical progress, tracheal epithelialization and costs over the 4 years. A chronology of events was derived from clinical notes and costs determined using reference costs per procedure. Serial tracheoscopy images, lung function tests and anti‐HLA blood samples were compared. Epithelial morphology and T cell, Ki67 and cleaved caspase 3 activity were examined. Computational fluid dynamic simulations determined flow, velocity and airway pressure drops. After the first year following transplantation, the number of interventions fell and the child is currently clinically well and continues in education. Endoscopy demonstrated a complete mucosal lining at 15 months, despite retention of a stent. Histocytology indicates a differentiated respiratory layer and no abnormal immune activity. Computational fluid dynamic analysis demonstrated increased velocity and pressure drops around a distal tracheal narrowing. Cross‐sectional area analysis showed restriction of growth within an area of in‐stent stenosis. This report demonstrates the long‐term viability of a decellularized tissue‐engineered trachea within a child. Further research is needed to develop bioengineered pediatric tracheal replacements with lower morbidity, better biomechanics and lower costs.     

Learning Curve in Tracheal Allotransplantation

The first vascularized tracheal allotransplantation was performed in 2008. Immunosuppression was stopped after forearm implantation and grafting of the recipient mucosa to the internal site of the transplant. Nine months after forearm implantation, the allograft was transplanted to the tracheal defect on the radial blood vessels. Since then, four additional patients have undergone tracheal allotransplantation, three (patients 2–4) for long‐segment stenosis and one (patient 5) for a low‐grade chondrosarcoma. Our goal was to reduce the time between forearm implantation and orthotopic transplantation and to determine a protocol for safe withdrawal of immunosuppressive therapy. Following forearm implantation, all transplants became fully revascularized over 2 months. Withdrawal of immunosuppression began 4 months after graft implantation and was completed within 6 weeks in cases 2–4. Repopulation of the mucosal lining by recipient cells, to compensate for the necrosis of the donor mucosa, was not complete. This resulted in partial loss of the allotransplant in patients 2–4. In patient 5, additional measures promoting recipient cell repopulation were made. The trachea may be used as a composite tissue allotransplant after heterotopic revascularization in the forearm. Measures to maximize recipient cell repopulation may be important in maintaining the viability of the transplant after cessation of immunosuppression.     

Low‐dose BMP‐2 and MSC dual delivery onto coral scaffold for critical‐size bone defect regeneration in sheep

Tissue‐engineered constructs (TECs) combining resorbable calcium‐based scaffolds and mesenchymal stem cells (MSCs) have the capability to regenerate large bone defects. Inconsistent results have, however, been observed, with a lack of osteoinductivity as a possible cause of failure. This study aimed to evaluate the impact of the addition of low‐dose bone morphogenetic protein‐2 (BMP‐2) to MSC‐coral‐TECs on the healing of clinically relevant segmental bone defects in sheep. Coral granules were either seeded with autologous MSCs (bone marrow‐derived) or loaded with BMP‐2. A 25‐mm‐long metatarsal bone defect was created and stabilized with a plate in 18 sheep. Defects were filled with one of the following TECs: (i) BMP (n = 5); (ii) MSC (n = 7); or (iii) MSC‐BMP (n = 6). Radiographic follow‐up was performed until animal sacrifice at 4 months. Bone formation and scaffold resorption were assessed by micro‐CT and histological analysis. Bone union with nearly complete scaffold resorption was observed in 1/5, 2/7, and 3/6 animals, when BMP‐, MSC‐, and MSC‐BMP‐TECs were implanted, respectively. The amount of newly formed bone was not statistically different between groups: 1074 mm³ [970–2478 mm³], 1155 mm³ [970–2595 mm³], and 2343 mm³ [931–3276 mm³] for BMP‐, MSC‐, and MSC‐BMP‐TECs, respectively. Increased scaffold resorption rate using BMP‐TECs was the only potential side effect observed. In conclusion, although the dual delivery of MSCs and BMP‐2 onto a coral scaffold further increased bone formation and bone union when compared to single treatment, results were non‐significant. Only 50% of the defects healed, demonstrating the need for further refinement of this strategy before clinical use. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2637–2645, 2017.

     

Enhancement of posterolateral lumbar spine fusion using low‐dose rhBMP‐2 and cultured marrow stromal cells

We tested the hypothesis that the dose of recombinant human bone morphogenetic protein‐2 (rhBMP‐2) required to induce spine fusion can be reduced by combination with mesenchymal stem cells (MSCs). Twenty‐four adult rabbits underwent posterolateral intertransverse fusion at the L4–L5 level. The animals were divided into four groups based on the implant material: autologous iliac graft, Alginate‐MSCs composite, Alginate‐BMP‐2‐MSCs composite, and Alginate‐BMP‐2 composite. After 16 weeks, the rabbits were euthanized for radiographic examination, manual palpation, biomechanical testing, and histology. Radiographic union of 12 intertransverse fusion areas for the autogenous iliac graft, Alginate‐MSCs, Alginate‐BMP‐2‐MSCs, and Alginate‐BMP‐2 groups was 11, 8, 11, and 0, respectively. Moreover, manual palpation of six fusion segments in each subgroup found solid union to be 6, 1, 5, and 0, respectively. The average torques at failure of the first three groups were 2278 ± 135, 1943 ± 140, and 2334 ± 187 N‐mm, respectively. The failure torque did not differ significantly between the autograft and Alginate‐BMP‐2‐MSCs groups; both groups were significantly higher than the Alginate‐MSCs group. The results indicate that MSCs delivered with in vitro cellular doses of rhBMP‐2 are more osteoinductive than MSCs without rhBMP‐2. In combination with MSCs, a low dose (2.5 µg) of rh‐BMP‐2 could enhance bone formation and posterolateral spine fusion success in the rabbit model. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:380–384, 2009     

自体骨髓基质细胞复合支架材料修复兔尺骨干节段骨缺损的实验研究

目的探讨组织工程骨的体内血管化情况和修复大节段骨缺损的能力。方法采用骨髓穿刺、密度梯度离心的方法获取兔骨髓基质细胞，经体外诱导分化，接种到聚磷酸钙纤维／L-聚乳酸／胶原(CPPF／PLLA／Collagen)支架材料上，植入自体尺骨中下段1．5cm长的骨膜骨缺损区，对照组为缺损区单纯植入CPPF／PLLA／Collagen，术后观察12周。结果术后4周缺损区为新生骨样组织充填，血循环丰富，12周时形态结构已接近正常骨组织；随修复时间延长，修复组织的力学性能逐渐增强。结论骨髓基质细胞与CPPF/PLLA／Collagen复合物具有较强的成骨能力，有望成为修复骨缺损的治疗方法。     

Stromal cell‐derived factor‐1 and monocyte chemotactic protein‐3 improve recruitment of osteogenic cells into sites of musculoskeletal repair

Homing of osteogenic cells through the systemic circulation represents an alternative to traditional orthopedic tissue engineering approaches that focus on local cell populations. We hypothesize that expression of the chemokine, stromal cell‐derived factor‐1 (SDF‐1) or monocyte chemotactic protein‐3 (MCP‐3) may enhance homing of osteogenic cells into sites of fracture repair, as both have demonstrated promise in recruitment of marrow stromal cells (MSCs). This hypothesis was tested by transplantation of culture expanded MSCs expressing these factors adjacent to a fracture site on a collagen scaffold. One green fluorescent protein positive (GFP⁺) and one wild‐type mouse were surgically conjoined as parabiots at 7–8 weeks of age. Fibular osteotomy was performed 4 weeks after parabiosis on the hind limb of the wild‐type mouse. Mice were randomly allocated to receive one of the following five treatments: control (no scaffold), empty scaffold (no cells), or scaffold containing MSCs, scaffold containing MSCs expressing SDF‐1, or scaffold containing MSCs expressing MCP‐3. Fracture callus was harvested 2 weeks after injury, and analyzed with confocal microscopy and cell‐counting software. When compared to fracture callus treated with nontransfected MSCs, the fracture callus of mice treated with both SDF‐1 and MCP‐3 secreting MSCs demonstrated a significant increase in the number of both GFP⁺ cells (p = 0.0003, p = 0.02) and GFP⁺/AP⁺ cells (p = 0.0005, p = 0.01). These data suggest that homing of osteogenic cells from systemic circulation participate in fracture repair and that homing pathways might be modulated to enhance the contribution of circulating progenitors at the site of skeletal injury. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29: 1064–1069, 2011     

高分子聚合物材料人工气管移植的实验研究

目的：通过材料筛选和编织成型工艺制备一种新型的人工气管假体,构建犬颈段气管缺损与重建的实验动物模型。方法：模拟气管解剖结构和几何形状,用聚丙烯和聚乙丙交酯纤维整体编织成网状直形管作为基本支架,根据涂层材料和涂层方法的不同制成3种类型人工气管,(1)Ⅰ型人工气管：网管内壁依次涂聚氨酯和胶原蛋白溶液封闭网管内壁网孔,外壁覆盖胶原蛋白-羟基磷灰石微孔状海绵层;(2)Ⅱ型人工气管：网管内外壁均涂聚氨酯;(3)Ⅲ型人工气管：网管内外壁仅涂胶原蛋白溶液。采用Ⅰ、Ⅱ、Ⅲ型人工气管分别对8、4、4只犬行人工气管移植术,于术后30、90、180d行纤维支气管镜、X线摄片及CT扫描检查,术后180d处死全部动物,组织标本行病理及电镜观察。结果：(1)移植Ⅰ型人工气管犬,5只存活至180d处死,3只犬分别因切口感染与吻合口瘘、假体滑脱及实验原因于术后45、96、90d死亡。处死犬假体与宿主气管及周围组织融为一体,纤维支气管镜检查示气管黏膜上皮不同程度地越过上、下吻合口向假体内腔中央汇合,新生的上皮为假复层纤毛柱状上皮,有纤毛超微结构。x线摄片和CT扫描示人工气管显影清晰,无移位、通畅良好,假体周围组织中散在分布大小不等的新骨。(2)移植Ⅱ型人工气管犬,术后均出现不同程度的假体移位、吻合口肉芽肿增生和管腔狭窄等并发症。(3)移植Ⅲ型人工气管犬,生存时间均未超过30d,主要死因为假体本身的网管裸露、感染、漏气和塌陷。结论：Ⅰ型人工气管兼具无孔型和有孔型人工气管的优点,基本具备了置换和替代长段气管缺损的重要条件。     

Tracheal replacement with an aortic autograft.

Tracheal replacement after extensive resection remains a challenge for the thoracic surgeon. We propose an innovative solution: the use of an aortic autograft. After an experimental work on animals with aortic autografts and allografts [Martinod E, Seguin A, Pfeuty K, Fornes P, Kambouchner M, Azorin JF, Carpentier AF. Long-term evaluation of the replacement of the trachea with an autologous aortic graft. Ann Thorac Surg 2003;75(5):1572-8; Martinod E, Seguin A, Holder-Espinasse M, Kambouchner M, Duterque-Coquillaud M, Azorin JF, Carpentier AF. Tracheal regeneration following tracheal replacement with an allogenic aorta. Ann Thorac Surg 2005;79(3):942-8], we present the first human case of long tracheal replacement with an aortic autograft. In this case we replaced 7 cm of a tumoral trachea using an aortic infra-renal autograft supported by a silicone stent. The early postoperative course was uneventful. The stent was removed at three months. The patient died at six months from an acute pulmonary infection without any sign of anastomosis leakage or graft rupture. A new field of clinical study has to be investigated.     

Tracheal reconstruction with a prefabricated deltopectoral flap combined with costal cartilage graft and palatal mucosal graft

We have created an alternative method for tracheal reconstruction. Our new surgical procedure using a deltopectoral flap combined with a costal cartilage graft and mucosal graft for tracheal reconstruction allows us to achieve reconstruction of the tracheal mucosa, the tracheal cartilage, and the covering skin with adequate subcutaneous tissue. In one case, a tracheostenosis was reconstructed with a deltopectoral flap combined with a costal cartilage graft. In the other case, a tracheal defect was reconstructed with a deltopectoral flap combined with a costal cartilage graft and palatal mucosal graft. Although the operation is a multistage procedure, our method provides satisfactory clinical results. Thus, we believe that our method is useful for the surgical treatment of large tracheal defects.     

Osteochondral regeneration using constructs of mesenchymal stem cells made by bio three‐dimensional printing in mini‐pigs

Osteoarthritis is a major joint disease that has been extensively investigated in humans and in model animals. In this study, we examined the regeneration of articular cartilage and subchondral bone using artificial scaffold‐free constructs composed of adipose tissue‐derived mesenchymal stem cells (AT‐MSCs) created using bio three‐dimensional (3D) printing with a needle‐array. Printed constructs were implanted into osteochondral defects created in the right femoral trochlear groove of six mini‐pigs, using femoral defects created in the left femurs as controls. Repair within the defects was evaluated at 3 and 6 months post‐implantation using computed tomography (CT) and magnetic resonance (MR) imaging. The radiolucent volume (RV, mm³) in the defects was calculated using multi‐planar reconstruction of CT images. MR images were evaluated based on a modified 2D‐ MOCART (magnetic resonance observation of cartilage repair tissue) grading system. Gross and microscopic pathology were scored according to the ICRS (International Cartilage Repair Society) scale at 6 months after implantation. The percentage RV at 3 months postoperation was significantly lower in the implanted defects than in the controls, whereas total scores based on the MOCART system were significantly higher in the implanted defects as compared with the controls. Although there were no statistical differences in the gross scores, the average histological scores were significantly higher in the implanted defects than in the controls. To our knowledge, this is the first report to suggest that artificial scaffold‐free 3D‐printed constructs of autologous AT‐MSCs can be aid in the osteochondral regeneration in pigs. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1398–1408, 2019.