Postural Stability and Pedobarography After Reconstruction of Peroneus Brevis Tendon Split Lesion.

PURPOSE: Lesions of the peroneal tendons are frequently overseen after ankle sprain. The symptoms consist of stress-dependent pain that extends from the inframalleolar to the proximal part along the course of the peroneal tendons as well as ankle instability and soft-tissue swelling. In case of unsuccessful conservative treatment, surgical therapy is recommended. The aim of the study was to evaluate the clinical and functional outcome after open reconstruction of the peroneus brevis tendon. METHODS: 13 patients were included in this retrospective study. All of them received a single reconstruction of the peroneus brevis tendon in open technique. Postoperative results were evaluated with the AOFAS score, a functional and perdobargraphic analysis as well as measuring postural stability with the Biodex balance system. The participants were matched with a healthy control group according to age, sex and BMI. RESULTS: The results of the AOFAS score showed significantly convincing results in all subscores postoperatively. A bilateral comparison of the postural stability showed that the affected side had become functionally similar to the healthy side. No statistical significant difference was detected concerning both one-legged and two-legged standing with the control group. Pedobarographic results revealed no difference between the affected and contralateral side, as well as between the patients and the healthy control group. CONCLUSION: Open reconstruction of the peroneus brevis tendon leads to significant better postoperative results and can be recommended after unsuccessful conservative treatment as promising option.

Pros and cons of navigated versus conventional total knee arthroplasty-a retrospective analysis of over 2400 patients.

INTRODUCTION: Because of the ongoing discussion of imageless navigation in total knee arthroplasty (TKA), its advantages and disadvantages were evaluated in a large patient cohort. METHODS: This retrospective analysis included 2464 patients who had undergone TKA at a high-volume university arthroplasty center between 2012 and 2017. Navigated and conventional TKA were compared regarding postoperative mechanical axis, surgery duration, complication rates, one-year postoperative patient-reported outcome measures (PROMs) (WOMAC and EQ-5D indices), and responder rates as defined by the criteria of the Outcome Measures in Rheumatology and Osteoarthritis Research Society International consensus (OMERACT-OARSI). RESULTS: Both navigated (1.8 ± 1.6°) and conventional TKA (2.1 ± 1.6°, p = 0.002) enabled the exact reconstruction of mechanical axis. Surgery duration was six minutes longer for navigated TKA than for conventional TKA (p < 0.001). Complication rates were low in both groups with comparable frequencies: neurological deficits (p = 0.39), joint infection (p = 0.42 and thromboembolic events (p = 0.03). Periprosthetic fractures occurred more frequently during conventional TKA (p = 0.001). One-year PROMs showed excellent improvement in both groups. The WOMAC index was statistically higher for navigated TKA than for conventional TKA (74.7 ± 19.0 vs. 71.7 ± 20.7, p = 0.014), but the increase was not clinically relevant. Both groups had a similarly high EQ-5D index (0.23 ± 0.24 vs. 0.26 ± 0.25, p = 0.11) and responder rate (86.5% [256/296] vs. 85.9% [981/1142], p = 0.92). CONCLUSION: Both methods enable accurate postoperative leg alignment with low complication rates and equally successful PROMs and responder rates one year postoperatively. LEVEL OF EVIDENCE: III. Retrospective cohort study.

[Intraoperative assessment of pelvic tilt and cup position in total hip arthroplasty: the relevance of navigation and robotics]. / Intraoperative Bestimmung der Beckenkippung und Pfannenposition in der Hüftendoprothetik ­ Relevanz der Navigation und Robotik.

The optimal 3D positioning of the prosthesis components is of great importance for the stability and function of a total hip endoprosthesis. Pelvic tilt has a particular influence on the position of the implant. In order to use intraoperatively the knowledge on pelvic kinematics gained through preoperative imaging procedures and movement analyses, "image-based" and "image-free" robotic and navigation procedures are available. With the "image-based" procedures, a 3D CT scan serves as the surgeon's basis for operative planning. The "image-free" procedures are based on the principles of stereotaxy. In the future, information about static and dynamic pelvic tilt will be conntected with navigation and robotic systems for total hip arthroplasty. Along with intraoperative data a patientindividual optimized implant position can be achieved.

[Conservative and surgical treatment of idiopathic scoliosis]. / Konservative und operative Therapie der idiopathischen Skoliose.

Idiopathic scoliosis is the largest group of all forms of scoliosis in the growth phase accounting for 80-90%. A distinction is made between idiopathic infantile (0-3 years), juvenile (4-10 years) and adolescent scoliosis (>10 years), depending on the age when scoliosis appears. The treatment depends on the skeletal age, the Cobb angle and the progression behavior of scoliosis. Mild cases are treated conservatively using physiotherapy, exercises and bracing but in advanced stages scoliosis should be surgically treated. With existing growth potential various techniques, such as traditional growing rods, magnetically controlled growth rods and vertebral body tethering are available. After the end of the growth phase a fusion should be recommended for scoliosis >50°.

The effects of soft tissue lateral release on the stability of the ligament complex of the knee.

PURPOSE: Valgus deformity presents a particular challenge in total knee arthroplasty. This condition regularly leads to contractures of the lateral capsular ligament complex and to overstretching of the medial ligamentous complex. Reconstruction of the knee joint kinematics and anatomy often requires lateral release. However, data on how such release weakens the stability of the knee are missing in the literature. This study investigated the effects of sequential lateral release on the collateral stability of the ligament complex of the knee in vitro. METHODS: Ten knee prostheses were implanted in 10 healthy cadaveric knee joints using a navigation device. Soft tissue lateral release consisted of five release steps, and stiffness and stability were determined at 0, 30, 60 and 90° flexion after each step. RESULTS: Soft tissue lateral release increasingly weakened the ligament complex of the lateral compartment. Because of the large muscular parts, the release of the iliotibial band and the M. popliteus had little effect on the stability of the lateral and medial compartment, but release of the lateral ligament significantly decreased the stability in the lateral compartment over the entire range of motion. Stability in the medial compartment was hardly affected. Conversely, further release of the posterolateral capsule and the posterior cruciate ligament led to the loss of stability in the lateral compartment only in deep flexion, whereas stability decreased significantly in the medial compartment. CONCLUSION: Our study shows for the first time the association between sequential lateral release and stability of the ligamentous complex of the knee. To maintain the stability, knee surgeons should avoid releasing the entire lateral collateral ligament, which would significantly decrease stability in the lateral compartment.

Weakening of the knee ligament complex due to sequential medial release in total knee arthroplasty.

PURPOSE: The purpose of this study was to investigate the effects of sequential medial release on the stiffness and collateral stability of the ligament complex of the knee. Irrespective of the implantation technique used, varus deformity frequently requires release of the capsular ligament complex. Yet, no data are available on how stiffness and stability of the knee ligament complex are weakened by such release. METHODS: After total knee arthroplasty, ten healthy Thiel-fixed knee joints were subjected to sequential medial release consisting of six release steps. After each step, stiffness and stability were determined at 0°, 30°, 60°, and 90°. RESULTS: Sequential medial release increasingly weakened the ligament complex. In extension, release of the anteromedial tibial sleeve 4 cm below the joint line already weakened the ligament complex by approximately 13%. Release 6 cm below the joint line reduced stiffness and stability by 15-20% over the entire range of motion. After detachment of the medial collateral ligament, stability was only about 60% of its initial value. CONCLUSION: Our study showed for the first time the association between medial release and stiffness and stability of the knee ligament complex. To maintain stability, vigorous detachment of the knee ligament complex should be avoided. Release of the anteromedial tibial sleeve already initiates loss of stability. The main stabiliser is the medial ligament, which should never be completely detached. LEVEL OF EVIDENCE: IV.

A simple method for determining ligament stiffness during total knee arthroplasty in vivo.

A key requirement in both native knee joints and total knee arthroplasty is a stable capsular ligament complex. However, knee stability is highly individual and ranges from clinically loose to tight. So far, hardly any in vivo data on the intrinsic mechanical of the knee are available. This study investigated if stiffness of the native ligament complex may be determined in vivo using a standard knee balancer. Measurements were obtained with a commercially available knee balancer, which was initially calibrated in vitro. 5 patients underwent reconstruction of the force-displacement curves of the ligament complex. Stiffness of the medial and lateral compartments were calculated to measure the stability of the capsular ligament complex. All force-displacement curves consisted of a non-linear section at the beginning and of a linear section from about 80 N onwards. The medial compartment showed values of 28.4 ± 1.2 N/mm for minimum stiffness and of 39.9 ± 1.1 N/mm for maximum stiffness; the respective values for the lateral compartment were 19.9 ± 0.9 N/mm and 46.6 ± 0.8 N/mm. A commercially available knee balancer may be calibrated for measuring stiffness of knee ligament complex in vivo, which may contribute to a better understanding of the intrinsic mechanical behaviour of knee joints.

Accuracy of Leg Length and Offset Restoration in Femoral Pinless Navigation Compared to Navigation Using a Fixed Pin during Total Hip Arthroplasty.

Equalization of biomechanical differences is a major goal in total hip arthroplasty (THA). In the current study we compared the accuracy of restoring leg length and offset using imageless navigation with an osseous fixed pin to a femoral pinless device in 97 minimally invasive THAs through an anterolateral approach in the lateral decubitus position. Leg length and offset differences were evaluated on magnification-corrected radiographs by a blinded observer. A postoperative mean difference of -0.9 mm (95% CI -2.8 mm to 1.1 mm, p = 0.38) between pinless navigation and navigation with a fixed pin was observed for leg length and that of -2.4 mm (95% CI -3.9 mm to -0.9 mm, p = 0.002) was observed for offset, respectively. The number of patients with a residual difference below 5 mm after THA was higher if using a fixed pin than in pinless navigation for both leg length (98.2%, 54/55 to 50.0%, 21/42, p < 0.001) and offset (100.0%, 55/55 to 71.4%, 30/42, p < 0.001). Imageless navigation is a feasible method in intraoperative control of leg length and offset in minimally invasive THA. The use of pins fixed to the bone has a higher precision than pinless devices. This trial is registered with DRKS00000739.

Stability of knee ligament complex of Thiel-embalmed cadaver compared to in vivo knee.

BACKGROUND: The first biomechanical evaluation of new implants is usually carried out with cadavers. Fixation of Thiel-embalmed cadavers is supposed to preserve the histological structure, colour and consistency of the tissue and has a low risk of infection and toxicity. However, the biomechanical properties of Thiel-fixated tissue are still unknown. The aim of this study was to quantify the effect of the Thiel-embalming method on the elastic properties of the ligament complex of the knee compared to in vivo knees during total knee arthroplasty. METHODS: The results of biomechanical tensile tests with 10 Thiel-embalmed knees were compared with the findings of 10 patients who underwent total knee arthroplasty with a standardised knee balancer at our department. We reconstructed the force-elongation curves of the medial and lateral ligament complex and calculated the stiffness in direct correlation with overall soft tissue stability in full extension and in 90° of flexion. RESULTS: All curves consisted of a non-linear part at the beginning and a linear part from about 80N onwards. In full extension, median stiffness in the cadavers was 26.6N/mm for the medial compartment and 31.6N/mm for the lateral compartment. The values for in vivo were 25.7N/mm for the medial compartment and 25.3N/mm for the lateral compartment (p=0.684 for the medial compartment and p=0.247 for the lateral compartment). In 90° of flexion, median stiffness in the cadaver group was 24.7N/mm for the medial compartment and 22.2N/mm for the lateral compartment. In vivo, median stiffness was 30.3N/mm for the medial compartment and 29.2N/mm for the lateral compartment (p=0.009 for the medial compartment and p=0.143 for the lateral compartment). CONCLUSION: Stiffness of the medial and lateral ligament complex in the knee was comparable between Thiel-embalmed cadavers and in vivo patients during total knee arthroplasty. Thiel fixation seems to preserve the soft tissue properties similar to those in vivo.

Positive medium-term influence of multimodal pain management on socioeconomic factors and health care utilization in patients with lumbar radiculopathy: a prospective study.

BACKGROUND: Multimodal pain management (MPM) represents a central approach to avoiding surgery in patients with lumbar radiculopathy. Independent of the type of health system, cost effectiveness and socioeconomic factors are becoming increasingly important. This study investigated the medium-term influence of conservative MPM on health care utilization and socioeconomic factors. METHODS: This study compared subjective, objective, and socioeconomic factors of 60 patients after inpatient MPM because of lumbar radiculopathy, before and 1 year ± 2 weeks after treatment. RESULTS: Over the course of the 1-year follow-up, one-third of the patients had not required any conservative treatment in comparison to 100% of patients before MPM therapy. The number of patients requiring analgesics could be significantly reduced from 26 to 12, and the number of patients who did not require any analgesics had increased from 14 to 32. After 1 year, the number of patients who had to regularly contact a physician because of low back pain (once per month for 6 months) had been reduced from 58 to 27. CONCLUSION: MPM is an effective approach to treating lumbar radiculopathy and reducing its negative influence on socioeconomic factors. Therapeutic benefits also include a decrease in health care utilization. Therefore, health care providers should place the mid-term success for patients and socioeconomic factors before the short-term costs of therapy.

Comparison of Lumbar Lordosis in Lateral Radiographs in Standing Position with supine MR Imaging in consideration of the Sacral Slope.

Purpose To investigate the influence of sacral slope on the correlation between measurements of lumbar lordosis obtained by standing radiographs and magnetic resonance images in supine position (MRI). Little information is available on the correlation between measurements of lumbar lordosis obtained by radiographic and MR images. Most relevant studies have shown correlations for the thoracic spine, but detailed analyses on the lumbar spine are lacking. Methods MR images and standing lateral radiographs of 63 patients without actual low back pain or radiographic pathologies of the lumbar spine were analyzed. Standing radiographic measurements included the sagittal parameters pelvic incidence (PI) pelvic tilt (PT), and sacral slope (SS); MR images were used to additionally measure lumbar L1-S1 lordosis and single level lordosis. Differences between radiographic and MRI measurements were analyzed and divided into 4 subgroups of different sacral slope according to Roussouly's classification. Results Global lumbar lordosis (L1-S1) was 44.99° (±â€Š10 754) on radiographs and 47.91° (±â€Š9.170) on MRI, yielding a clinically relevant correlation (r = 0.61, p < 0.01). Measurements of single level lordosis only showed minor differences. At all levels except for L5 / S1, lordosis measured by means of standing radiographs was higher than that measured by MRI. The difference in global lumbar L1-S1 lordosis was -2.9°. Analysis of the Roussouly groups showed the largest difference for L1-S1 (-8.3°) in group 2. In group 4, when measured on MRI, L5 / S1 lordosis (25.71°) was lower than L4 / L5 lordosis (27.63°) compared to the other groups. Conclusions Although measurements of global lumbar lordosis significantly differed between the two scanning technologies, the mean difference was just 2.9°. MRI in supine position may be used for estimating global lumbar lordosis, but single level lordosis should be determined by means of standing radiographs. Key Points · Large difference between radiographic and MRI measurements of level L5 / S1.. · MRI can be used for estimating global lumbar lordosis.. · Analysis of single level lordosis necessitates measurement in standing radiographs.. Citation Format · Benditz A, Boluki D, Weber M et al. Comparison of Lumbar Lordosis in Lateral Radiographs in Standing Position with supine MR Imaging in consideration of the Sacral Slope. Fortschr Röntgenstr 2017; 189: 233 - 239.

Native femoral anteversion should not be used as reference in cementless total hip arthroplasty with a straight, tapered stem: a retrospective clinical study.

BACKROUND: Improper femoral and acetabular component positioning can be associated with instability, impingement, component wear and finally patient dissatisfaction in total hip arthroplasty (THA). The concept of "femur first"/"combined anteversion", incorporates various aspects of performing a functional optimization of the prosthetic stem and cup position of the stem relative to the cup intraoperatively. In the present study we asked two questions: (1) Do native femoral anteversion and anteversion of the implant correlate? (2) Do anteversion of the final broach and implant anteversion correlate? METHODS: In a secondary analysis of a prospective controlled trial, a subgroup of 55 patients, who underwent computer-assisted, cementless THA with a straight, tapered stem through an anterolateral, minimally invasive (MIS) approach in a lateral decubitus position were examined retrospectivly. Intraoperative fluoroscopy was used to verify a "best-fit" position of the final broach. An image-free navigation system was used for measurement of the native femoral version, version of the final broach and the final implant. Femoral neck resection height was measured in postoperative CT-scans. This investigation was approved by the local Ethics Commission (No.10-121-0263) and is a secondary analysis of a larger project (DRKS00000739, German Clinical Trials Register May-02-2011). RESULTS: The mean difference between native femoral version and final implant was 1.9° (+/- 9.5), with a range from -20.7° to 21.5° and a Spearman's correlation coefficient of 0.39 (p < 0.003). In contrast, we observed a mean difference between final broach and implant version of -1.9° (+/- 3.5), with a range from -12.7° to 8.7° and a Spearman's correlation coefficient of 0.89 (p < 0.001). In 83.6 % (46/55) final stem version was outside the normal range as defined by Tönnis (15-20°). The mean femoral neck resection height was 7.3 mm (+/- 5.6). There was no correlation between resection height and version of the implant (Spearman's correlation coefficient 0.14). CONCLUSION: Native femoral version significantly differs from the final anteversion of a cementless, straight, tapered stem and therefore is not a reliable reference in cementless THA. Measuring anteversion of the final "fit and fill" broach is a feasible assistance in order to predict final stem anteversion intraoperatively. There is no correlation between femoral neck resection height and version of the implant.

Even the Intraoperative Knowledge of Femoral Stem Anteversion Cannot Prevent Impingement in Total Hip Arthroplasty.

BACKGROUND: In this prospective study of 66 patients undergoing cementless total hip arthroplasty through a minimally invasive anterolateral approach, we evaluated the impact of an intraoperative hybrid combined anteversion technique on postoperative range of motion (ROM). METHODS: After navigation of femoral stem anteversion, trial acetabular components were positioned manually, and their position recorded with navigation. Then, final components were implanted with navigation at the goals prescribed by the femur-first impingement detection algorithm. Postoperatively, three-dimensional computed tomographies were performed to determine achieved component position and model impingement-free ROM by virtual hip movement, which was compared with published values necessary for activities of daily living. This model was run a second time with the implants in the position selected by the surgeon rather than the navigation program. In addition, we researched into risk factors for ROM differences between the freehand and navigated cup position. RESULTS: We found a lower flexion of 8.3° (8.8°, P < .001) and lower internal rotation of 9.2° (9.5°, P < .001) for the freehand implanted cups in contrast to a higher extension of 9.8° (11.8°, P < .001) compared with the navigation-guided technique. For activities of daily living, 58.9% (33/56) in the freehand group compared with 85.7% (48/56) in the navigation group showed free flexion (P < .001) and similarly 50.0% (28/56) compared with 76.8% (43/56) free internal rotation (P < .001). Body mass index, incision length, and cup size were identified as independent risk factors for reduced flexion and internal rotation in the freehand group. CONCLUSION: For implementation of a combined anteversion algorithm, intraoperative alignment guides for accurate cup positioning are required using a minimally invasive anterolateral approach. Obese patients are especially at risk of cup malpositioning.

Soft matrix supports osteogenic differentiation of human dental follicle cells.

The differentiation of stem cells can be directed by the grade of stiffness of the developed tissue cells. For example a rigid extracellular matrix supports the osteogenic differentiation in bone marrow derived mesenchymal stem cells (MSCs). However, less is known about the relation of extracellular matrix stiffness and cell differentiation of ectomesenchymal dental precursor cells. Our study examined for the first time the influence of the surface stiffness on the proliferation and osteogenic differentiation of human dental follicle cells (DFCs). Cell proliferation of DFCs was only slightly decreased on cell culture surfaces with a bone-like stiffness. The osteogenic differentiation in DFCs could only be initiated with a dexamethasone based differentiation medium after using varying stiffness. Here, the softest surface improved the induction of osteogenic differentiation in comparison to that with the highest stiffness. In conclusion, different to bone marrow derived MSCs, soft ECMs have a superior capacity to support the osteogenic differentiation of DFCs.

Comparison of human dental follicle cells (DFCs) and stem cells from human exfoliated deciduous teeth (SHED) after neural differentiation in vitro.

Dental stem cells from human exfoliated deciduous teeth (SHED) and dental follicle cells (DFCs) are neural crest-derived stem cells from human dental tissues. Interestingly, SHED and DFCs can successfully differentiate into neuron-like cells. We hypothesized that SHED and DFCs have the same neural cell differentiation potentials. To evaluate neural cell differentiation, we cultivated SHED and DFCs in four different serum-replacement media (SRMs) and analyzed cell morphology, cell proliferation, and gene expression patterns before and after differentiation. In a standard cell culture medium, SHED and DFCs have not only similar cell morphologies, but they also have similar gene expression patterns for known stem cell markers. However, only SHED expressed the neural stem cell marker Pax6. After cultivation in SRMs, cell proliferations of DFCs and SHED were reduced and the cell morphology was spindle-like with long processes. However, differentiated DFCs and SHED had different neural cell marker expression patterns. For example, gene expression of the late neural cell marker microtubule-associated protein 2 was upregulated in DFCs and downregulated in SHED in SRM with the B27 supplement. In contrast, SHED formed neurosphere-like cell clusters in SRM with the B27 supplement, epidermal growth factor, and fibroblast growth factor-2. Moreover, SHED differentially expressed the glial cell marker glial fibrillary acidic protein, which in contrast was weakly or not expressed in DFCs. In conclusion, SHED and DFCs have different neural differentiation potentials under the same cell culture conditions.

A two-step strategy for neuronal differentiation in vitro of human dental follicle cells.

Human dental follicle cells (DFCs) derived from wisdom teeth are precursor cells for cementoblasts. In this study, we recognized that naïve DFCs express constitutively the early neural cell marker beta-III-tubulin. Interestingly, DFCs formed beta-III-tubulin-positive neurosphere-like cell clusters (NLCCs) on low-attachment cell culture dishes in serum-replacement medium (SRM). For a detailed examination of the neural differentiation potential, DFCs were cultivated in different compositions of SRM containing supplements such as N2, B27, G5 and the neural stem cell supplement. Moreover, these cell culture media were combined with different cell culture substrates such as gelatin, laminin, poly-L-ornithine or poly-L-lysine. After cultivation in SRM, DFCs differentiated into cells with small cell bodies and long cellular extrusions. The expression of nestin, beta-III-tubulin, neuron-specific enolase (NSE) and neurofilament was up-regulated in SRM supplemented with G5, a cell culture supplement for glial cells, and the neural stem cell supplement. DFCs formed NLCCs and demonstrated an increased gene expression of neural cell markers beta-III-tubulin, NSE, nestin and for small neuron markers such as neuropeptides galanin (GAL) and tachykinin (TAC1) after cultivation on poly-L-lysine. For a further neural differentiation NLCC-derived cells were sub-cultivated on laminin and poly-L-ornithine cell culture substrate. After 2 weeks of differentiation, DFCs exposed neural-like cell morphology with small neurite-like cell extrusions. These cells differentially express neurofilament and NSE, but only low levels of beta-III-tubulin and nestin. In conclusion, we demonstrated the differentiation of human DFCs into neuron-like cells after a two-step strategy for neuronal differentiation.

Proteomic analysis of osteogenic differentiation of dental follicle precursor cells.

Recently, there has been an increased interest in unravelling the molecular mechanisms and cellular pathways controlling the differentiation and proliferation of human stem cell lines. Proteome analysis has proven to be an effective approach to comprehensive analysis of the regulatory network of differentiation. In the present study we applied 2-DE combined with capillary-LC-MS/MS analysis to profile differentially regulated proteins upon differentiation of dental follicle precursor cells (DFPCs). Out of 115 differentially regulated proteins, glutamine synthetase, lysosomal proteinase cathepsin B proteins, plastin 3 T-isoform, beta-actin, superoxide dismutases, and transgelin were found to be highly up-regulated, whereas cofilin-1, pro-alpha 1 collagen, destrin, prolyl 4-hydrolase and dihydrolipoamide dehydrogenase were found to be highly down-regulated. The group of up-regulated proteins is associated with actin-bundling and defence against oxidative cellular stress, whereas down-regulated proteins were associated with collagen biosynthesis. Bioinformatic analyses of the entire data set confirmed these findings that represent significant steps towards the understanding of DFPC differentiation. The bioinformatic analyses suggest that proteins associated with cell cycle progression and protein metabolism were down-regulated and proteins involved in catabolism, cell motility and biological quality were up-regulated. These results display the general physiological state of DFPCs before and after osteogenic differentiation. We also identified regulatory proteins, such as the transcription factors TP53 and Sp-1, associated with the differentiation process. Further studies will investigate the impact of identified regulatory proteins for cell proliferation and osteogenic differentiation in DFPCs.

Gene expression profiles of dental follicle cells before and after osteogenic differentiation in vitro.

Recently, osteogenic precursor cells were isolated from human dental follicles, which differentiate into cementoblast- or osteoblast-like cells under in vitro conditions after the induction with dexamethasone or insulin. However, mechanisms for osteogenic differentiation are not understood in detail. In a previous study, real-time RT-PCR results demonstrated molecular mechanisms in dental follicle cells (DFCs) during osteogenic differentiation that are different from those in bone-marrow-derived mesenchymal stem cells. We analysed gene expression profiles in DFCs before and after osteogenic differentiation with the Affymetrix GeneChip(R) Human Gene 1.0 ST Array. Transcripts of 98 genes were up-regulated after differentiation. These genes could be clustered into subcategories such as cell differentiation, cell morphogenesis, and skeletal development. Osteoblast-specific transcription factors like osterix and runx2 were constitutively expressed in differentiated DFCs. In contrast, the transcription factor ZBTB16, which promotes the osteoblastic differentiation of mesenchymal stem cells as an up-stream regulator of runx2, was differentially expressed after differentiation. Transcription factors NR4A3, KLF9 and TSC22D3, involved in the regulation of cellular development, were up-regulated as well. In conclusion, we present the first transcriptome of human DFCs before and after osteogenic differentiation. This study sheds new light on the complex mechanism of osteogenic differentiation in DFCs.

Somatic stem cells for regenerative dentistry.

Complex human tissues harbour stem cells and/or precursor cells, which are responsible for tissue development or repair. Recently, dental tissues such as periodontal ligament (PDL), dental papilla or dental follicle have been identified as easily accessible sources of undifferentiated cells. The dental stem cell biology might provide meaningful insights into the development of dental tissues and cellular differentiation processes. Dental stem cells could also be feasible tools for dental tissue engineering. Constructing complex structures like a periodontium, which provides the functional connection between a tooth or an implant and the surrounding jaw, could effectively improve modern dentistry. Dental precursor cells are attractive for novel approaches to treat diseases like periodontitis, dental caries or to improve dental pulp healing and the regeneration of craniofacial bone and teeth. These cells are easily accessible and, in contrast to bone-marrow-derived mesenchymal stem cells, are more closely related to dental tissues. This review gives a short overview of stem cells of dental origin.