The 3D patellar tendon moment arm: Quantified in vivo during volitional activity

Effects of cyclic stress on the mechanical properties of collagen fascicles were studied by in vitro tissue culture experiments. Collagen fascicles (approximately 300 μm in diameter) obtained from the rabbit patellar tendon were applied cyclic load at 4 Hz for one hour per day during culture period for one or two weeks, and then their mechanical properties were determined using a micro-tensile tester. There was a statistically significant correlation between tensile strength and applied peak stress in the range of 0 to 5 MPa, and the relation was expressed by a quadratic function. The maximum strength (19.4 MPa) was obtained at the applied peak stress of 1.8 MPa. The tensile strength of fascicles were within a range of control values, if they were cultured under peak stresses between 1.1 and 2.6 MPa. Similar results were also observed in the tangent modulus, which was maintained at control level under applied peak stresses between 0.9 and 2.8 MPa. The stress of 0.9 to 1.1 MPa is equivalent to approximately 40% of the in vivo peak stress which is developed in the intact rabbit patellar tendon by running, whereas that of 2.6 to 2.8 MPa corresponds to approximately 120% of the in vivo peak stress. Therefore, the fascicles cultured under applied peak stresses of lower than 40% and higher than 120% of the in vivo peak stress do not keep the original strength and modulus. These results indicate that the mechanical properties of cultured collagen fascicles strongly depend upon the magnitude of the stress applied during culture, which are similar to our previous results observed in stress-shielded and overstressed patellar tendons in vivo.

Download Full-text

Changes in the tibialis anterior tendon moment arm from rest to maximum isometric dorsiflexion: in vivo observations in man

Clinical Biomechanics ◽

10.1016/s0268-0033(99)00018-2 ◽

1999 ◽

Vol 14 (9) ◽

pp. 661-666 ◽

Cited By ~ 46

Author(s):

Constantinos N. Maganaris ◽

Vasilios Baltzopoulos ◽

Anthony J. Sargeant

Keyword(s):

Tibialis Anterior ◽

Moment Arm ◽

Tibialis Anterior Tendon

Download Full-text

Hypoxia promotes tenocyte differentiation of mesenchymal stem cells

10.21203/rs.2.23515/v1 ◽

2020 ◽

Author(s):

Guanyin Chen ◽

wangqian zhang ◽

Jintao Gu ◽

Yuan Gao ◽

Lei He ◽

...

Keyword(s):

Stem Cells ◽

Mesenchymal Stem Cells ◽

Patellar Tendon ◽

Tendon Repair ◽

Clinical Results ◽

Tendon Injury ◽

Tenogenic Differentiation ◽

Tgf Β1

Abstract Background: Tendon injury is a common but tough medical problem. Unsatisfactory clinical results have been reported in tendon repair using mesenchymal stem cells (MSCs) therapy, creating a need for a better strategy to induce MSCs to tenogenic differentiation. This study was designed to investigate the role of hypoxia in the tenogenic differentiation of MSCs in vitro and in vivo and to compare the tenogenic differentiation capacities of different MSCs under hypoxia condition in vitro. Methods: Adipose tissue-derived MSCs (AMSCs) and bone marrow-derived MSCs (BMSCs) were isolated and characterized by the expression of MSC-specific markers and tri-lineage differentiation. The expression of hypoxia induced factor-1 alpha (Hif-1α) and the proliferation of AMSCs and BMSCs were examined in order to confirm the establishment of hypoxia condition. qRT-PCR, western blot, and immunofluorescence staining were used to evaluate the expression of tendon-associated marker Col-1a1, Col-3a1, Dcn, and Tnmd in AMSCs and BMSCs under hypoxia and/or Tgf-β1 condition. In vivo, a patellar tendon injury model was established. Normoxic and hypoxic BMSCs were cultured and implanted. Histological, biomechanical and transmission electron microscopy analyses were performed to assess the improved healing effect of hypoxic BMSCs on tendon injury. Results: Hypoxia remarkably increased the expression of Hif-1α and the proliferation of AMSCs and BMSCs. Our in vitro results detected that hypoxia not only promoted a significant increase in tenogenic markers in both AMSCs and BMSCs compared with the normoxia group, but also showed higher inductility compared with Tgf-β1. In addition, hypoxic BMSCs exhibited higher potential of tenogenic differentiation than hypoxic AMSCs. Our in vivo results demonstrated that hypoxic BMSCs possessed better histological and biomechanical properties than those of normoxic BMSCs, as evidenced by histological scores, quantitative analysis of immunohistochemical staining for Col-1a1 and Tnmd, the range and average of collagen fibril diameters and patellar tendon biomechanical tests. Conclusions: These findings suggested that hypoxia may be a practical and reliable strategy to induce tenogenic differentiation of BMSCs for tendon repair and could enhance the effectiveness of MSCs therapy in treating tendon injury.

Download Full-text

In vivo evaluation of human patellar tendon microstructure and microcirculation with diffusion MRI

Journal of Magnetic Resonance Imaging ◽

10.1002/jmri.26898 ◽

2019 ◽

Vol 51 (3) ◽

pp. 780-790

Author(s):

Kenneth Wengler ◽

Takeshi Fukuda ◽

Dharmesh Tank ◽

David E. Komatsu ◽

Megan Paulus ◽

...

Keyword(s):

Patellar Tendon ◽

Diffusion Mri ◽

In Vivo Evaluation

Download Full-text

Hypoxia-Induced Mesenchymal Stem Cells Exhibit Stronger Tenogenic Differentiation Capacities and Promote Patellar Tendon Repair in Rabbits

Stem Cells International ◽

10.1155/2020/8822609 ◽

2020 ◽

Vol 2020 ◽

pp. 1-16

Author(s):

Guanyin Chen ◽

Wangqian Zhang ◽

Kuo Zhang ◽

Shuning Wang ◽

Yuan Gao ◽

...

Keyword(s):

Patellar Tendon ◽

Tendon Repair ◽

Biomechanical Properties ◽

Clinical Results ◽

Medical Problem ◽

Tendon Injury ◽

Tenogenic Differentiation ◽

Tgf Β1

Tendon injury is a common but tough medical problem. Unsatisfactory clinical results have been reported in tendon repair using mesenchymal stem cell (MSC) therapy, creating a need for a better strategy to induce MSCs to tenogenic differentiation. This study was designed to examine the effect of hypoxia on the tenogenic differentiation of different MSCs and their tenogenic differentiation capacities under hypoxia condition in vitro and to investigate the in vivo inductility of hypoxia in tenogenesis. Adipose tissue-derived MSCs (AMSCs) and bone marrow-derived MSCs (BMSCs) were isolated and characterized. The expression of hypoxia-induced factor-1 alpha (Hif-1α) was examined to confirm the establishment of hypoxia condition. qRT-PCR, western blot, and immunofluorescence staining were used to evaluate the expression of tendon-associated marker Col-1a1, Col-3a1, Dcn, and Tnmd in AMSCs and BMSCs under hypoxia condition, compared with Tgf-β1 induction. In vivo, a patellar tendon injury model was established. Normoxic and hypoxic BMSCs were cultured and implanted. Histological, biomechanical, and transmission electron microscopy analyses were performed to assess the improved healing effect of hypoxic BMSCs on tendon injury. Our in vitro results showed that hypoxia remarkably increased the expression of Hif-1α and that hypoxia not only promoted a significant increase in tenogenic markers in both AMSCs and BMSCs compared with the normoxia group but also showed higher inductility compared with Tgf-β1. In addition, hypoxic BMSCs exhibited higher potential of tenogenic differentiation than hypoxic AMSCs. Our in vivo results demonstrated that hypoxic BMSCs possessed better histological and biomechanical properties than normoxic BMSCs, as evidenced by histological scores, patellar tendon biomechanical parameters, and the range and average of collagen fibril diameters. These findings suggested that hypoxia may be a practical and reliable strategy to induce tenogenic differentiation of BMSCs for tendon repair and could enhance the effectiveness of MSCs therapy in treating tendon injury.

Download Full-text

pO2 Measurement in an Experimental Model of Patellar Tendon Autograft Pro-Anterior Cruciate Ligament

The International Journal of Artificial Organs ◽

10.1177/039139889802100309 ◽

1998 ◽

Vol 21 (3) ◽

pp. 174-178 ◽

Cited By ~ 5

Author(s):

M. Rocca ◽

G. Giavaresi ◽

N. Nicoli Aldini ◽

M. Fini ◽

M. Marcacci ◽

...

Keyword(s):

Anterior Cruciate Ligament ◽

Patellar Tendon ◽

Microvessel Density ◽

Cruciate Ligament ◽

Microvessel Count ◽

Experimental Tool ◽

Anterior Cruciate ◽

Tendon Autograft ◽

Po2 Measurement

Thirty-four sheep were submitted to surgery substituting the native ACL with the central third of the patellar tendon, ten enter this study. The purpose was to find a possible relationship between tissue pO2 and healing processes considering also the biomechanical and histomorphological aspects of the grafts. Four of them were sacrificed under general anaesthesia after 6 months, and six after 1 year in order to perform tissue pO2 measurement and an analysis of microvessel density on specimens of the normal ACL and the graft. Our data showed higher pO2 values of the autografts after 6 months. After 1 year the data was comparable to those of native ACL. This was confirmed by a microvessel count of the histological specimens and the data was in relationship to biomechanical and histomorphological analysis. Tissue pO2 can be observed and recorded in “in vivo” ACL, and patellar tendon used as graft, with no injury to their integrity. The monitoring system might be considered as an experimental tool for indirect controls of the anterior cruciate substitutes.

Download Full-text