Amplification of Mitochondrial Activity in the Healing Response Following Rotator Cuff Tendon Injury

Abstract

Mitochondrial function following rotator cuff tendon injury (RCI) influences the tendon healing. We examined the mitochondrial morphology and function under hypoxia in the shoulder tendon tissue from surgically-induced tenotomy-RCI rat model and cultured swine tenocytes. The tendon tissue was collected post-injury on 3–5 (Group-A), 10–12 (Group-B), and 22–24 (Group-C), days and the corresponding contralateral tendons were used as control for each group. There was higher protein expression of citrate synthase (P < 0.0001) [10.22 MFI (mean fluorescent intensity)] and complex-1 (P = 0.0008) (7.86 MFI) in Group-A and Group-B that decreased in Group-C [(P = 0.0201) (5.78 MFI and (P = 0.7915) (2.32 MFI), respectively] compared to control tendons. The ratio of BAX:Bcl2 (Bcl2 associated x protein:B cell lymphoma 2) in RCI tendons increased by 50.5% (Group-A) and 68.4% (Group-B) and decreased by 25.8% (Group-C) compared to normoxic controls. Hypoxia increased β-tubulin expression (P = 0067) and reduced PGC1-α (P = 0412) expression in the isolated swine tenocytes with no effect on the protein expression of Complex-1 (P = 7409) and citrate synthase (P = 0.3290). Also, the hypoxic tenocytes exhibited about 4-fold increase in mitochondrial superoxide (P < 0.0001), altered morphology and mitochondrial pore integrity, and increase in mitochondrial density compared to normoxic controls. These findings suggest the critical role of mitochondria in the RCI healing response.

Mitochondrial dysfunction and potential mitochondrial protectant treatments in tendinopathy

“…21 Another study, by Thankam et al, demonstrated that the expression of two mitochondrial biomarkers, citrate synthase and complex-1, were increased significantly at 3-5 days and 10-12 days after injury in a rat rotator cuff tendon injury surgical model but decreased in the later phase of healing. 31 They also found that the hypoxic tenocytes exhibited an increase in mitochondrial superoxide, altered morphology and mitochondrial pore integrity, and increased mitochondrial density compared with the control group. These findings also support the notion that mitochondrial function may be critical in not only the development of tendinopathic disorders but also the tendon healing response.…”

“…The pathological impact of hypoxia-induced mitochondrial dysfunction and pro-oxidant responses has been reported to play a critical role in the initiation of rotator cuff tendinopathy. 31 Among the alarmins, HIF1α senses oxygen and is regulated by oxygen availability. 69 Hypoxia induces the translocation of HIF1α into the nucleus in isolated macrophages, 70 indicating that HIF1α activation induces mitochondrial dysfunction, which is reflected by increased ROS, mitochondrial membrane potential, and mitochondrial mass.…”

“…Immunohistochemical analyses also identified upregulated gene expression and protein levels of HMGB1, HIF1α, and IL‐33 in human degenerative tendons compared with normal tendons. The pathological impact of hypoxia‐induced mitochondrial dysfunction and pro‐oxidant responses has been reported to play a critical role in the initiation of rotator cuff tendinopathy 31 . Among the alarmins, HIF1α senses oxygen and is regulated by oxygen availability 69 .…”

Hybrid interpenetrating hydrogel network favoring the bidirectional migration of tenocytes for rotator cuff tendon regeneration

“…Infraspinatus tendon tissue was aseptically harvested from the shoulder of Yucatan microswine (Sinclair Research) (female, 6–8 months old) from an ongoing study approved by the Institutional Animal Care and Use Committee (IACUC) of Creighton University, Omaha, NE. The tenocytes were isolated following the partial collagenase digestion explant culture standardized in our laboratory 16 . The isolated tenocytes were maintained in DMEM containing 20% FBS and antibiotics at 37°C and 5% CO 2 in a humidified incubator, the media was changed twice a week, passaged at 70–80% confluency, and the cells in passage 2–4 were used for the studies.…”

Involvement of Ischemia-driven 5LPOX-RvE1-ChemR23 axis in the resolution of post-CABG inflammation in Coronary Arteries

“…The CASMCs were maintained as mentioned above (Control, ISC, and ISC/R) in chamber slides, xed with 10% formalin for 20 min and immuno uorescence of 5LPOX, 12LPOX, 15LPOX, COX2, ChemR23, GPCR18, and GPCR120 were performed [17]. The primary antibodies and uorochrome-conjugated secondary antibodies were diluted 1:400 and 1:500, respectively.…”