A novel nano-structured porous polycaprolactone scaffold improves hyaline cartilage repair in a rabbit model compared to a collagen type I/III scaffold: in vitro and in vivo studies

Purpose

To develop a nano-structured porous polycaprolactone (NSP-PCL) scaffold and compare the articular cartilage repair potential with that of a commercially available collagen type I/III (Chondro-Gide^®) scaffold.

Methods

By combining rapid prototyping and thermally induced phase separation, the NSP-PCL scaffold was produced for matrix-assisted autologous chondrocyte implantation. Lyophilizing a water–dioxane–PCL solution created micro and nano-pores. In vitro: The scaffolds were seeded with rabbit chondrocytes and cultured in hypoxia for 6 days. qRT–PCR was performed using primers for sox9, aggrecan, collagen type 1 and 2. In vivo: 15 New Zealand White Rabbits received bilateral osteochondral defects in the femoral intercondylar grooves. Autologous chondrocytes were harvested 4 weeks prior to surgery. There were 3 treatment groups: (1) NSP-PCL scaffold without cells. (2) The Chondro-Gide^® scaffold with autologous chondrocytes and (3) NSP-PCL scaffold with autologous chondrocytes. Observation period was 13 weeks. Histological evaluation was made using the O’Driscoll score.

Results

In vitro: The expressions of sox9 and aggrecan were higher in the NSP-PCL scaffold, while expression of collagen 1 was lower compared to the Chondro-Gide^® scaffold. In vivo: Both NSP-PCL scaffolds with and without cells scored significantly higher than the Chondro-Gide^® scaffold when looking at the structural integrity and the surface regularity of the repair tissue. No differences were found between the NSP-PCL scaffold with and without cells.

Conclusion

The NSP-PCL scaffold demonstrated higher in vitro expression of chondrogenic markers and had higher in vivo histological scores compared to the Chondro-Gide^® scaffold. The improved chondrocytic differentiation can potentially produce more hyaline cartilage during clinical cartilage repair. It appears to be a suitable cell-free implant for hyaline cartilage repair and could provide a less costly and more effective treatment option than the Chondro-Gide^® scaffold with cells.     

兔外周血MSC复合同种异体脱钙皮质骨修复软骨缺损的研究

目的:比较外周血(peripheral blood,PB)与骨髓(bone marrow,BM)来源MSC复合脱钙皮质骨基质(demineralized cortical bone matrix,DCBM)修复兔膝关节软骨缺损的效果,为其进一步的临床应用提供实验参考。方法:获取分离培养的第三代兔PB-MSC和BM-MSC,以2×107/ml的细胞密度接种于DCBM上。20只成年新西兰兔,构建股骨远端滑车关节面中心部大面积全层软骨缺损模型,随机分为4组:I组:PB-MSC/DCBM复合物;II组:BM-MSC/DCBM复合物;III组:单纯DCBM支架组;IV组:空白缺损组。分别于术后24周、48周取材,通过大体观察、组织学评分、组织化学和免疫组织化学染色评价其在体内修复软骨的效果。结果:移植后24周PB-MSC/DCBM组:修复区由半透明组织填充,局部有小的浅的凹陷,表面光整,稍低于周围正常软骨,与周围组织连接连续。BM-MSC/DCBM组的大体观察类似I组。单纯DCBM组:表面光整,与周围组织连续性不如I、II组。空白缺损组:仍有一大的缺损。48周PB-MSC/DCBM组和BM-MSC/DCBM组,缺损区基本不可见,充填好,表面光滑,基本和周围正常组织无界限,与周围软骨连续性好,软骨细胞外基质表达较多。组织学评分显示:在24周和48周两个时间点,PB-MSC/DCBM组和BM-MSC/DCBM组比较组间无差异,均显著高于单纯DCBM组和空白缺损组。结论:PB-MSC具备与BM-MSC相似的修复兔关节软骨缺损的能力。     

关节软骨修复细胞基因治疗中软骨细胞支架载体特点

目的 探讨四种不同类型三维支架中培养的关节软骨细胞活性状况及其转基因特性.方法 原代培养兔膝关节软骨细胞,并且以表达绿色荧光蛋白(GFP)和萤火虫荧光素酶(GL3)的腺病毒载体AdGFP和AdGL3进行感染.在I型胶原海绵、纤维蛋白胶、透明质酸和聚乳酸四种类型的支架材料中,以荧光显微镜和荧光素酶分析法检测细胞的活性状况及其转基因特性;以阿辛蓝染色评价软骨基质的产生.结果 表达绿色荧光蛋白的腺病毒(AdGFP)成功感染兔关节软骨细胞,并且持续表达绿色荧光蛋白.被感染的软骨细胞在所有被测试的细胞支架上均能存活,并能表达GFP和荧光素酶报告基因.与其余三种支架比较,聚乳酸支架中转基凶表达率最高(P<0.01).而且聚乳酸培养体系中,4周时可以检测到阿辛蓝染色阳性的基质材料.结论 在关节软骨修复的细胞基因治疗领域,聚乳酸可能是一种合适的支架材料.     

一氧化氮抑制兔关节软骨细胞II型胶原的合成

一氧化氮（NO）在骨关节炎和关节软骨代谢中具有重要的病理生理作用。为研究NO与关节软骨II型胶原的关系,我们在培养的兔关节软骨细胞中以药物刺激产生NO后,分别用ELISA及RT-PCR法测定II型胶原及前II型胶原α1链（COL2A1）mRNA表达量的变化。结果表明,0.2mM的硝普钠（SNP）可释放出大量NO,使软骨细胞II型胶原的含量减低,同时,RT-PCR法证实前II型胶原mRNA表达量也减少。100u/ml白细胞介素-1（IL-1）可刺激软骨细胞释放NO并使II型胶原量降低,其COL2A1mRNA表达量也减少。加用1mg/ml精氨酸甲酯（NAME,NO合酶抑制剂）后,则抑制了IL-1的作用,使NO产量下降,II型胶原含量部分恢复,COL2A1完全恢复。本试验证实了NO作为IL-1的下游分子抑制II型胶原的合成;其抑制作用是通过减少前II型胶原α1链mRNA表达量完成的。这在软骨细胞反分化过程中具有重要意义。     

One-step osteochondral repair with cartilage fragments in a composite scaffold

Purpose

This study proposes a single-step therapeutic approach for osteochondral defects using autologous cartilage fragments loaded onto a scaffold composed of a hyaluronic acid (HA) derivative, human fibrin glue (FG) and autologous platelet-rich-plasma (PRP), in a rabbit model. The aim is to demonstrate the in vitro outgrowth of chondrocytes from cartilage fragments and the in vivo formation of a functional repair tissue.

Methods

In vitro: minced articular cartilage was loaded onto two different types of scaffold (paste or membrane) according to two different HA preparations (injectable HA-derivative or HA-derivative felt). In vivo: trochlear osteochondral defects were created in 50 adult rabbits, which were then assigned to 5 different treatment groups: cartilage fragments loaded onto membrane scaffolds with FG (Group 1) or without FG (Group 2); membrane scaffolds alone with FG (Group 3) or without FG (Group 4); empty defects (Group 5). Membrane scaffolds were used “in vivo” for simpler preparation and better adhesive properties. Repair processes were evaluated histologically and by immunohistochemistry at 1, 3, and 6 months.

Results

An in vitro time-dependent cell outgrowth from cartilage fragments was observed with both types of scaffolds. At 6 months, in vivo, cartilage fragment-loaded scaffolds induced significantly better repair tissue than the scaffold alone using histological scoring. Repair in Group 2 was superior to that in any of the control groups (p < 0.05).

Conclusion

Autologous cartilage fragments loaded onto an HA felt/FG/PRP-scaffold provided an efficient cell source, and allowed for an improvement of the repair process of ostechondral defects in a rabbit model. Human FG, however, hampered the rabbit healing process. These results may have clinical relevance as they show the potential of a novel one-stage repair technique for osteochondral defects.     

Platelet-rich plasma activation in combination with biphasic osteochondral scaffolds–conditions for maximal growth factor production

Purpose  

The combination of scaffolds and biological factors may enhance articular cartilage repair. Little is known regarding the activation and subsequent growth factor release of platelet-rich plasma (PRP) in contact with biosynthetic scaffolds. The purpose of this study was i) to identify whether the addition of thrombin was required to activate PRP in the presence of a collagen osteochondral scaffold and ii) to compare the activity of PRP when applied to both collagen- and polylactide-based osteochondral scaffolds.     

Osteochondritis dissecans (OCD), an endoplasmic reticulum storage disease?: a morphological and molecular study of OCD fragments

Osteochondritis dissecans (OCD) fragments, cartilage and blood from four patients were used for morphological and molecular analysis. Controls included articular cartilage and blood samples from healthy individuals. Light microscopy and transmission electron microscopy (TEM) showed abnormalities in chondrocytes and extracellular matrix of cartilage from OCD patients. Abnormal type II collagen heterofibrils in “bundles” and chondrocytes with abnormal accumulation of matrix proteins in distended rough endoplasmic reticulum were typical findings. Further, Von Kossa staining and TEM showed empty lacunae close to mineralized “islands” in the cartilage and hypertrophic chondrocytes containing accumulated matrix proteins. Immunostaining revealed: (1) that types I, II, VI and X collagens and aggrecans were deposited intracellulary and (2) co‐localization within the islands of types I, II, X collagens and aggrecan indicating that hypertrophic chondrocytes express a phenotype of bone cells during endochondral ossification. Types I, VI and X collagens were also present across the entire dissecates suggesting that chondrocytes were dedifferentiated. DNA sequencings were non‐conclusive, only single nucleotide polymorphism was found within the COL2A1 gene for one patient. We suggest that OCD lesions are caused by an alteration in chondrocyte matrix synthesis causing an endoplasmic reticulum storage disease phenotype, which disturbs or abrupts endochondral ossification.     

Anterior cruciate ligament regeneration using mesenchymal stem cells and collagen type I scaffold in a rabbit model

Purpose

The objective of this study was to determine whether using mesenchymal stem cells (MSC) seeded in a collagen type I scaffold would be sufficient to regenerate the torn anterior cruciate ligament (ACL).

Methods

Anterior cruciate ligament transection was performed on both knees in 10 New Zealand rabbits and then repaired with as follows: suture alone (suture-treated group, n = 6), suture associated with collagen type I scaffold (collagen type I scaffold-treated group, n = 8) or suture associated with autologous MSC seeded on collagen type I scaffold (MSC/collagen type I scaffold-treated group, n = 6). At 12-week post-intervention, the animals were killed and the ACLs were characterised macroscopically and histologically. Data of the 3 groups were against normal ACL (normal group, n = 10).

Results

Macroscopic observation found that in MSC/collagen type I scaffold group, 33 % of specimens showed a complete ACL regeneration, with a tissue similar to the normal ACL. Regeneration was not observed in the group treated with suture alone or associated with collagen type I scaffold without cells. In the latter, only a reparative attempt at the ends was observed. Histological analysis of the regenerated ACL showed a tissue with organised collagen and peripheric vessels.

Conclusions

These results provide evidence that the use of MSC seeded in a collagen type I scaffold in the treatment of ACL injuries is associated with an enhancement of ligament regeneration. This MSC-based technique is a potentially attractive tool for improving the treatment of ACL ruptures.     

Adhesion and collagen production of human tenocytes seeded on degradable poly(urethane urea)

Purpose

The aim of this study was to investigate whether human tenocytes taken from ruptured quadriceps tendon could be seeded on a biodegradable polycaprolactone-based polyurethanes (PU) urea scaffold. Scaffold colonization and collagen production after different culture periods were analyzed to understand whether tenocytes from ruptured tendons are able to colonize these biodegradable scaffolds.

Methods

Human primary tenocyte cultures of ruptured quadriceps tendons were seeded on PU scaffolds. After 3, 10 and 15 days of incubation, the samples were stained with haematoxylin and eosin and were examined under white light microscopy. After 15 and 30 days of incubation, samples were examined under transmission electron microscope. Total collagen accumulation was also evaluated after 15, 30 and 45 days of culture.

Results

After 15 and 30 days of culture, tenocyte-seeded scaffolds showed cell colonization and cell accumulation around interconnecting micropores. Tenocyte phenotype was variable. Collagen accumulation in seeded scaffolds demonstrated a progressive increase after 15, 30 and 45 days of culture, while control non-seeded scaffolds show no collagen accumulation.

Conclusion

These results showed that human tenocytes from ruptured quadriceps tendon can be seeded on polycaprolactone-based PU urea scaffolds and cultured for a long time period (45 days). This study also showed that human tenocytes from ruptured tendons seeded on PU scaffolds are able to penetrate the scaffold showing a progressively higher collagen accumulation after 15, 30 and 45 days of incubation. This study provides the basis to use this PU biodegradable scaffold in vivo as an augmentation for chronic tendon ruptures and in vitro as a scaffold for tissue engineering construct.     

Biologic injections for osteoarthritis and articular cartilage damage: can we modify disease?

Objective: The purpose of the present investigation is to conduct a systematic review of the literature to review the clinical results of platelet rich plasma (PRP) and mesenchymal stem cell treatments (MSC) (biologics) for articular cartilage lesions and osteoarthritis of the knee.

Methods: A search of the PubMed, EMBASE, and Cochrane databases was performed to identify studies involving biologic therapy for osteoarthritis or osteochondral defects. Only Level I-III clinical trials with at least 3-month follow-up were included. Outcome data was gathered on any patient-completed surveys, 2nd look arthroscopy, follow-up imaging, biopsy/histology results, and any adverse effects of treatment.

Results: Thirty-three articles met our inclusion criteria. There was a total of 21 PRP studies in the study. All PRP studies showed clinical improvement with PRP therapies in outcomes surveys measuring patient satisfaction, pain, and function. Two studies reported no significant difference in improvement compared to hyaluronic acid (HA). Similarly, the 7/9 MSC studies showed improvement. One study found BM-MSC implantation was not significantly superior to matrix assisted chondrocyte implantation (MACI), while one reported peripheral blood stem cells (PBSC) did not significantly improve outcomes over HA. Of the three studies looking at a combination of MSC/PRP, two found MSC/PRP combination did not improve outcomes compared to MSC or PRP therapy alone. The one PRP study that had a 2nd look arthroscopy reported increases cartilage regeneration with PRP. All 8 MSC studies with follow-up MRI and all 7 MSC studies with 2nd look arthroscopy showed improvement in cartilage regeneration in terms of coverage, fill of the defect, and/or firmness of the new cartilage.

Conclusion: Current data suggests that, of the two treatments, MSC provides more significant disease modifying effect; however, further research needs to be done to compare these two treatments and determine if there is a synergetic effect when combined.     

雌激素对软骨细胞胶原表型表达的影响

目的 :观察雌激素对体外培养兔关节软骨细胞胶原表型表达的影响。方法 :体外培养雌兔关节软骨细胞 ,随机分为A、B两组 ,A组中加入 1 7β -雌二醇 0mol/L、1 0 - 6 mol/L、1 0 - 7mol/L、1 0 - 8mol/L、1 0 - 9mol/L、1 0 - 10 mol/L、1 0 - 11mol/L、1 0 - 12 mol/L干预 72小时 ;B组先用 1 0ng/mlIL - 1 β干预 2 4小时 ,随后分别加入 0mol/L、1 0 - 6 mol/L～ 1 0 - 12 mol/L 1 7β -雌二醇作用 72小时。采用RT-PCR方法观察软骨细胞Ⅰ、Ⅱ、Ⅲ型胶原表达。结果 :1 0 - 6 mol/L雌二醇或单用IL - 1 β均抑制正常软骨细胞Ⅱ型胶原mRNA表达 ,低浓度雌二醇 (1 0 - 11、1 0 - 12 mol/L)能够对抗IL - 1 β的抑制作用 ;所有软骨细胞均未表达Ⅲ型胶原mRNA ;几乎所有浓度雌二醇 (1 0 - 12 mol/L除外 )均诱导软骨细胞表达Ⅰ型胶原。结论 :雌激素对关节软骨细胞胶原表型表达的调控作用随其浓度变化而不同。对变性软骨细胞而言 ,低于生理浓度的雌激素 (1 0 - 12 mol/L)对维持其胶原表型最适宜。     

Osteochondral regeneration using a novel aragonite-hyaluronate bi-phasic scaffold in a goat model

Purpose

The objective of this study was to examine whether different mechanical modifications and/or impregnation of hyaluronic acid (HA) might enhance aragonite-based scaffold properties for the regeneration of cartilage and bone in an animal model.

Methods

Bi-phasic osteochondral scaffolds were prepared using coralline aragonite with different modifications, including 1- to 2-mm-deep drilled channels in the cartilage phase (Group 1, n = 7) or in the bone phase (Group 2, n = 8), and compared with unmodified coral cylinders (Group 3, n = 8) as well as empty control defects (Group 4, n = 4). In each group, four of the implants were impregnated with HA to the cartilage phase. Osteochondral defects (6 mm diameter, 8 mm depth) were made in medial and lateral femoral condyles of 14 goats, and the scaffolds were implanted according to a randomization chart. After 6 months, cartilage and bone regeneration were evaluated macroscopically and histologically by an external laboratory.

Results

Group 1 implants were replaced by newly formed hyaline cartilage and subchondral bone (combined histological evaluation according to the ICRS II-2010 and O’Driscoll et al. 34 ± 4 n = 7). In this group, the cartilaginous repair tissue showed a smooth contour and was well integrated into the adjacent native cartilage, with morphological evidence of hyaline cartilage as confirmed by the marked presence of proteoglycans, a marked grade of collagen type II and the absence of collagen type I. The average scores in other groups were significantly lower (Group 2 (n = 8) 28.8 ± 11, Group 3 (n = 8) 23 ± 9 and Group 4 (empty control, n = 4) 19.7 ± 15).

Conclusions

The implants with the mechanical modification and HA impregnation in the cartilage phase outperformed all other types of implant. Although native coral is an excellent material for bone repair, as a stand-alone material implant, it does not regenerate hyaline cartilage. Mechanical modification with drilled channels and impregnation of HA within the coral pores enhanced the scaffold’s cartilage regenerative potential. The modified implant shows young hyaline cartilage regeneration. This implant might be useful for the treatment of both chondral and osteochondral defects in humans.     

Effect of in vitro culture on a chondrocyte-fibrin glue hydrogel for cartilage repair

Research in tissue engineering has been focused on articular cartilage repair for more than a decade. Some pioneristic studies involved the use of hydrogels such as alginate and fibrin glue which still possess valuable potential for cartilage regeneration. One of the main issues in cartilage tissue engineering is represented by the ideal maturation of the construct, before in vivo implantation, in order to optimize matrix quality and integration. The present study was focused on the effect of in vitro culture on a fibrin glue hydrogel embedding swine chondrocytes. We performed an evaluation of the immunohistochemical and biochemical composition and of the biomechanical properties of the construct after 1 and 5 weeks of culture. We noticed that chondrocytes survived in the fibrin glue gel and enhanced their synthetic activity. In fact, DNA content remained stable, while all indices of cartilage matrix production increased (GAGs content, immunohistochemistry for collagen II and safranin-o staining). On the other hand, the biomechanical properties remained steady, indicating a gradual substitution of the hydrogel scaffold by cartilaginous matrix. This demonstrates that an optimal preculture could provide the surgeon with a better engineered cartilage for implantation. However, whether this more mature tissue will result in a more efficient regeneration of the articular surface still has to be evaluated in future investigations.     

关节软骨表层组织的免疫防护作用

文中的实验采用免疫荧光组织学方法观察到正常的关节软骨表层组织可阻止抗Ⅱ型胶原抗体侵入软骨深部组织,防止抗体与软骨细胞结合,具有免疫防护作用。     

血管组织工程基质材料及管形支架的制备

目的：几种血管基质材料的制作及比较。方法：采用EDC交联胶原和粘多糖材料；采用戊二醛和热交联得到明胶加壳聚糖材料；应用去垢剂，渗透压改变和核酸酶消化的方法，对猪主动脉进行去细胞处理，得到完整的去细胞纤维支架。采用直接模具成型，形成多种管形支架。结果：得到明胶加壳聚糖、完整的猪主动脉去细胞纤维支架等几种基质材料；管形支架外径1cm，内径0．6～0．8cm，放置培养液中10d，可保持管腔形状，不塌陷，不变形。结论：明胶加壳聚糖三维结构好，主动脉脱细胞基质仍显致密，采用模具直接成型、冷冻干燥技术相结合，可以得到多种管状的可降解基质支架。     

Gamma radiation induces senescence in human adult mesenchymal stem cells from bone marrow and periodontal ligaments

Purpose: Mesenchymal stem cells isolated from bone marrow (BM-MSC) and periodontal ligament (PLSC) are cells with high proliferative potential and ability to self-renewal. Characterization of these cells under genotoxic stress conditions contributes to the assessment of their prospective usage. The aim of our study was to evaluate changes in BM-MSC and PLSC caused by ionizing radiation. Methods: Human BM-MSC and PLSC were irradiated with the doses up to 20 Gy by Co⁶⁰ and observed 13 days; viability, proliferation, apoptosis and senescence induction, and changes in expression and phosphorylation status of related proteins were studied. Results: Irradiation with the doses up to 20 Gy significantly reduces proliferation, but has no significant effect on cell viability. The activation of tumor suppressor protein 53 (p53) and its phosphorylations on serines 15 and 392 were detected from the first day after irradiation by 20 Gy and remained elevated to day 13. Expression of cyclin-dependent kinases inhibitor 1A (p21^Cip1/Waf1) increased. The cell cycle was arrested in G2 phase. Instead of apoptosis we have detected hallmarks of stress-induced premature senescence: increase in cyclin-dependent kinases inhibitor 2A (p16^INK4a) and increased activity of senescence-associated β-galactosidase. Conclusion: Mesenchymal stem cells isolated from bone marrow and periodontal ligament respond to ionizing radiation by induction of stress-induced premature senescence without apparent differences in their radiation response.     

Similar clinical outcomes following collagen or polyurethane meniscal scaffold implantation: a systematic review

Purpose

The purpose of this systematic review is to evaluate the current literature in an effort to assess specific clinical outcomes following meniscal scaffold implantation using the two available scaffolds: Collagen Meniscal Implant (CMI) and the Actifit polyurethane meniscal scaffold.

Methods

A systematic review was performed by searching PubMed, Embase, and Cochrane Library to find studies evaluating clinical outcomes of patients undergoing meniscal scaffold implantation. Search terms used were “meniscus”, “meniscal”, “scaffold”, and “implant”. Studies were evaluated based on scaffold type, treatment failure rates, patient-reported outcome scores, concomitant procedures, and radiological findings. Radiological findings were recorded using the Genovese scale to assess morphology and signal intensity and the Yulish score to assess articular cartilage.

Results

Nineteen studies (1 level I, 1 level II, 17 level IV evidence) were identified that met inclusion criteria, including a total of 658 patients (347 Actifit, 311 CMI). The overall average follow-up was 45 months. Treatment failure occurred in 9.9% of patients receiving the Actifit scaffold at a mean follow-up of 40 months and 6.7% of patients receiving CMI at a mean follow-up of 44 months (n.s.). However, the rate of failure ranged from 0 to 31.8% amongst the included studies with a variable definition of failure. Additionally, overlapping patients and presence of concomitant surgeries such as anterior cruciate ligament reconstruction (ACLR) and high tibial osteotomy (HTO) may have a significant influence on these results. Outcomes for the Visual Analog Scale (VAS) for pain, Lysholm knee score, and Tegner activity score improved from preoperatively to latest follow-up in both groups, while the Knee Injury and Osteoarthritis Outcome Score and International Knee Documentation Committee scores improved from preoperatively to latest follow-up for Actifit scaffold patients. Overall, patients receiving CMI scaffolds had higher grades for Genovese morphology and signal intensity when compared to Actifit scaffold patients.

Conclusion

Patients undergoing meniscal scaffold implantation with either CMI or Actifit scaffold can both be expected to experience improvement in clinical outcomes when used in association with concomitant procedures such as ACLR and HTO.

Level of evidence

IV, systematic review.

     

Human cartilage fragments in a composite scaffold for single-stage cartilage repair: an in vitro study of the chondrocyte migration and the influence of TGF-β1 and G-CSF

Purpose

Minced chondral fragments are becoming popular as a source of cells for cartilage repair, as a growing interest is developing towards one-stage procedures to treat cartilage lesions. The purpose of this study is to (A) compare cell outgrowth from cartilage fragments of adult and young donors using two different types of scaffolds and (B) evaluate the influence of transforming-growth-factor-β1 (TGF-β1) and granulocyte colony-stimulating factor (G-CSF) on chondrocyte behaviour.

Methods

In part (A) cartilage fragments from adult and young donors were either loaded onto an HA-derivative injectable paste scaffold or onto an HA-derivative membrane scaffold. Construct sections were then examined for cell counting after 1, 2 and 3 months. In part (B) only membrane scaffolds were prepared using cartilage fragments from young donors. Constructs were cultured either in standard growth medium or in the presence of specific growth factors, such as TGF-β1 or G-CSF or TGF-β1 + G-CSF. After 1 month, construct sections were examined for cell counting. Expression of chondrocyte markers (SOX9, CD151, CD49c) and proliferative markers (β-catenin, PCNA) was assessed using immunofluorescence techniques, both in unstimulated construct sections and in cells from unstimulated and stimulated construct cultures.

Results

Part (A): histological analysis showed age-dependent and time-dependent chondrocyte migration. A significant difference (p < 0.05) was observed between young and older donors at the same time point. No difference was detected between the two types of scaffolds within the same group at the same time point. Part (B): after 1 month, the number of migrating cells/area significantly increased due to exposure to TGF-β1 and/or G-CSF (p < 0.05). Immunofluorescence revealed that outgrowing cells from unstimulated scaffold sections were positive for SOX9, CD151, CD49c and G-CSF receptor. Immunofluorescence of cells from construct cultures showed an increase in β-catenin in all stimulated groups and an increased PCNA expression in G-CSF-exposed cultures (p < 0.05).

Conclusion

Outgrowing cells may represent a subset of chondrocytes undergoing a phenotypic shift towards a proliferative state. TGF-β1, and to a greater extent G-CSF, may accelerate this outgrowth. The clinical relevance of this study may involve a potential future clinical application of scaffolds preloaded with growth factors as an additional coating for chondral fragments. Indeed, a controlled delivery of G-CSF, widely employed in various clinical settings, might improve the repair process driven by minced human cartilage fragments during one-stage cartilage repair.     

Further studies on the anisotropic distribution of collagen in articular cartilage by μMRI

To further study the anisotropic distribution of the collagen matrix in articular cartilage, microscopic magnetic resonance imaging experiments were carried out on articular cartilages from the central load‐bearing area of three canine humeral heads at 13 μm resolution across the depth of tissue. Quantitative T₂ images were acquired when the tissue blocks were rotated, relative to B₀, along two orthogonal directions, both perpendicular to the normal axis of the articular surface. The T₂ relaxation rate (R₂) was modeled, by three fibril structural configurations (solid cone, funnel, and fan), to represent the anisotropy of the collagen fibrils in cartilage from the articular surface to the cartilage/bone interface. A set of complex and depth‐dependent characteristics of collagen distribution was found in articular cartilage. In particular, there were two anisotropic components in the superficial zone and an asymmetrical component in the radial zone of cartilage. A complex model of the three‐dimensional fibril architecture in articular cartilage is proposed, which has a leaf‐like or layer‐like structure in the radial zone, arises in a radial manner from the subchondral bone, spreads and arches passing the isotropic transitional zone, and exhibits two distinct anisotropic components (vertical and transverse) in the surface portion of the tissue. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.     

关节软骨细胞体外培养时生物学性状的变化

<正> 在运动医学领域中,由于运动员的关节软骨伤病发生率远高于普通人,同时又缺乏有效的治疗方法,影响训练和运动成绩的提高,因此对关节软骨伤病的研究一直是重点科研项目之一。对关节软骨进行研究的手段近20年来有了巨大进步,其标志是关节软骨细胞在体外分离培养取得成功。它作为探索软骨细胞性状的先进手段正越来越广泛地被应用到关节软骨损伤和疾患的研究工作中。我所1982年在体外分离培养关节软骨细胞获得成功。近年来,对关节软骨细胞在体外培养过程中所