Improving the preservation of isolated rat skeletal muscles stored for 16 hours at 4 degrees C

Long-Term Cultivation of Human Atrial Myocardium

Organotypic culture of human ventricular myocardium is emerging in basic and translational cardiac research. However, few institutions have access to human ventricular tissue, whereas atrial tissue is more commonly available and important for studying atrial physiology. This study presents a method for long-term cultivation of beating human atrial myocardium. After written informed consent, tissues from the right-atrial appendage were obtained from patients with sinus rhythm undergoing open heart surgery with cardiopulmonary bypass. Trabeculae (pectinate muscles) prepared from the samples were installed into cultivation chambers at 37°C with a diastolic preload of 500 μN. After 2 days with 0.5 Hz pacing, stimulation frequency was set to 1 Hz. Contractile force was monitored continuously. Beta-adrenergic response, refractory period (RP) and maximum captured frequency (f_max) were assessed periodically. After cultivation, viability and electromechanical function were investigated, as well as the expression of several genes important for intracellular Ca²⁺ cycling and electrophysiology. Tissue microstructure was analyzed by confocal microscopy. We cultivated 19 constantly beating trabeculae from 8 patient samples for 12 days and 4 trabeculae from 3 specimen for 21 days. Functional parameters were compared directly after installation (0 d) with those after 12 d in culture. Contraction force was 384 ± 69 μN at 0 d and 255 ± 90 μN at 12 d (p = 0.8, n = 22), RP 480 ± 97 ms and 408 ± 78 ms (p = 0.3, n = 9), f_max 3.0 ± 0.5 Hz and 3.8 ± 0.5 Hz (p = 0.18, n = 9), respectively. Application of 100 nM isoprenaline to 11 trabeculae at 7 d increased contraction force from 168 ± 35 μN to 361 ± 60 μN (p < 0.01), f_max from 6.4 ± 0.6 Hz to 8.5 ± 0.4 Hz (p < 0.01) and lowered RP from 319 ± 22 ms to 223 ± 15 ms. CACNA1c (L-type Ca²⁺ channel subunit) and GJA1 (connexin-43) mRNA expressions were not significantly altered at 12 d vs 0 d, while ATP2A (SERCA) and KCNJ4 (Kir2.3) were downregulated, and KCNJ2 (Kir2.1) was upregulated. Simultaneous Ca²⁺ imaging and force recording showed preserved excitation-contraction coupling in cultivated trabeculae. Confocal microscopy indicated preserved cardiomyocyte structure, unaltered amounts of extracellular matrix and gap junctions. MTT assays confirmed viability at 12 d. We established a workflow that allows for stable cultivation and functional analysis of beating human atrial myocardium for up to 3 weeks. This method may lead to novel insights into the physiology and pathophysiology of human atrial myocardium.

Muscle is a target for preservation in a rat limb replantation model

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Background:

Ischemia exceeding 6 hours makes clinical limb replantation difficult and places the patient at risk of functional deficit or limb loss. We investigated the preservation of muscle function and morphology with solutions in rat hindlimb in vivo and in vitro.

Methods:

Quadriceps femoris muscles from luciferase transgenic rats were preserved for 24 hours at 4°C in extracellular-type trehalose containing Kyoto (ETK), University of Wisconsin (UW), or lactated Ringer’s (LR) solution (control). Muscle luminescence was measured with a bioimaging system. Amputated limbs of Lewis rats preserved with ETK, UW, or LR for 6 or 24 hours at 4°C were transplanted orthotopically. At week 8, terminal latency and amplitude were measured in the tibialis anterior muscle. The muscles were also analyzed histologically.

Results:

Isolated muscles preserved in ETK or UW had significantly higher luminescence than did muscles immersed in LR (P < 0.05). In the 6-hour-preserved limb transplantation model, although the 3 groups had almost the same terminal latency, electrical amplitude was significantly lower in the LR group. Histologically, muscles preserved with LR showed the most atrophic changes. In the 24-hour-preserved model, the survival rate of the LR group was 37.5% in contrast to 80% in the ETK and UW groups. Electrical signals were not detected in the LR group owing to severe muscle atrophy and fibrosis. The ETK and UW groups showed good muscle function electrophysiologically.

Conclusions:

Preservation solutions can protect muscle function and morphology in ischemia–reperfusion limbs and improve recipient survival rates after transplantation of long-term-preserved limbs.

Evaluation of functional and structural alterations in muscle tissue after short-term cold storage in a new tissue preservation solution

Storage of muscle preparations in vitro is required for the diagnosis of neuromuscular disorders and for electrophysiological tests. The current standard protocols for muscle storage or transport, i.e. placement on 0.9% NaCl-moistened gauze, lead to impaired function and structural alterations. For other tissues, however, improved preservation methods and solutions have recently been described. In this study, functional and structural alterations in the murine diaphragm were compared after storage on 0.9% NaCl-moistened gauze and after storage in different modifications of the new vascular preservation solution TiProtec®. Muscle force generation after nerve stimulation, histological parameters and ATP levels were investigated after 2.5 h of cold storage at 4°C in the different media and 0.5 h of rewarming at 25°C in Tyrode buffer. Murine diaphragms were injured during cold storage and rewarming, with the degree of the alteration being dependent on the type of solution used. There were no histological alterations and no caspase 3 activation in all groups. In contrast, diaphragms stored in the modified TiProtec solution showed markedly better performance concerning force generation after nerve stimulation (7.1 ± 1.1 cN · s) as well as higher ATP content (2.4 ± 0.7 μmol/g) and were superior to storage on 0.9% NaCl-moistened gauze (1.4 ± 0.4 cN · s; 0.3 ± 0.1 μmol/g). In conclusion, the modified TiProtec preservation solution showed promising results for short-term cold storage of murine diaphragms. For further evaluation, the transferability of these positive findings to storage conditions for muscles of other species, especially human muscle tissue, needs to be investigated.

Contractile and morphological properties of hamster retractor muscle following 16 h of cold preservation

INTRODUCTION

Cold hypoxia is a common factor in cold tissue preservation and mammalian hibernation. The purpose of this study was to determine the effects of cold preservation on the function of the retractor (RET) muscle of the hamster in the non-hibernating state and compare these with previously published data (van der Heijden et al., 2000) on the rat cutaneus trunci (CT) muscle.

MATERIALS AND METHODS

After cold storage (16 h at 4 degrees C), muscles were stimulated electrically to measure maximum tetanus tension (P(0)) and histologically analyzed. The protective effects of addition of the antioxidants trolox and deferiprone and the calcium release inhibitor BDM to the storage fluid were determined.

RESULTS

After storage, the twitch threshold current was increased (from 60 to 500 microA) and P(0) was decreased to 27% of control. RET morphology remained unaffected. RET muscle function was protected by trolox and deferiprone (P(0), resp., 43% and 59% of control). Addition of BDM had no effect on the RET.

CONCLUSIONS

The observed effects of cold preservation and of trolox and deferiprone on the RET were comparable to those on CT muscle function, as reported in a previously published study (van der Heijden et al., 2000). Both hamster RET and rat CT muscles show considerable functional damage due to actions of reactive oxygen species. In contrast to the CT, in the RET cold preservation-induced functional injury could not be prevented by BDM and was not accompanied by morphological damage such as necrosis and edema. This suggests that the RET myocytes possess a specific adaptation to withstand the Ca(2+) overload induced by cold ischemia.

Vascular anatomy of the hamster retractor muscle with regard to its microvascular transfer

BACKGROUND

The hamster retractor muscle (RET) is used as an in vivo model in studies of skeletal muscle ischemia-reperfusion injury. The RET is unique in that the muscle can be isolated while preserving the primary vascular supply so that its contractile function can be measured simultaneously with local microvascular responses to experimental interventions. The goal of this study was to understand the anatomical origin of the vascular supply to the RET and determine whether the RET can be used as a free flap after surgical isolation of the thoracodorsal vessels.

METHODS

Microdissection was performed to determine the anatomy of the vasculature that supplies and drains the RET.

RESULTS

Distinct numbers and patterns of feed arteries (2-4) and collecting veins (1-3) were identified (n = 26 animals). Dye injection (n = 8) of the thoracodorsal artery demonstrated that the RET remains perfused following its isolation on the thoracodorsal pedicle. Heterotopic allograft transplantation of the RET (n = 2) was performed by anastomosing the thoracodorsal vessels to the femoral vessels using the end-to-side technique.

CONCLUSIONS

The anatomical relationships indicate that the RET can be used as a free flap model for evaluating the effect of preservation strategies and transplantation on skeletal muscle microcirculation and contractile function.

Preservation of Rat Cremaster Muscle Microcirculation after Prolonged Cold Storage and Transplantation

BACKGROUND

Microvascular surgery for the reconstruction of complex defects involves an ischemic period, which may cause flap failure as the result of ischemia/reperfusion injury. We assessed the microvascular consequences of rat cremaster muscle transplantation after prolonged periods of cold storage in HTK-Bretschneider solution (HTK).

MATERIALS AND METHODS

Cremaster muscle transplantations were performed immediately or after 8 or 24 h of cold storage (4 degrees C) in HTK or saline. Intravital microscopy was used to quantify capillary perfusion and venular leukocyte-endothelium interactions following transplantation.

RESULTS

The transplantation procedure itself resulted in 50-65 min of ischemia. After direct transplantation, capillary perfusion was 90% of control. Transplantation after 8 h of cold storage in either HTK or saline did not deteriorate capillary perfusion. When the tissue was stored for 24 h, HTK was superior to saline in preserving capillary perfusion (HTK: 76-83% of control, saline: 30%). Immediate transplantation induced a small increase in leukocyte adhesion. Prolonged cold storage in either fluid resulted in reduced flow velocities (qualitative observations) and edema formation, which hampered quantification of leukocyte-endothelium interactions.

CONCLUSIONS

Even after 8 or 24 h of cold storage in HTK, transplantation of rat cremaster muscle was successful with good capillary perfusion. Capillary perfusion was better preserved in HTK than in saline.

Effect of hypothermia and HTK on the microcirculation in the rat cremaster muscle after ischaemia

Hypothermia is an important preservation method for tissues and solid organs. The aim of the present study was to assess in rat cremaster muscle the effect of hypothermia, without or with pre-ischaemic HTK (histidine-tryptophan-ketoglutarate–Bretschneider solution) perfusion, on microvascular consequences of 4 or 6 h ischaemia and 2 h of reperfusion. Intravital microscopy was applied to examine capillary perfusion and leucocyte–endothelium interactions. The cremaster muscle was subjected to 4 or 6 h of cold (4 °C) or warm (33–34 °C) ischaemia and 2 h of reperfusion. Measurements were performed at baseline, prior to HTK perfusion and ischaemia, and at 0, 1 and 2 h after blood flow restoration. Hypothermia completely prevented the 50% reduction in capillary perfusion that was observed previously at start of reperfusion after 4 h warm ischaemia. After 6 h of warm ischaemia, perfusion resumed in only 45% of capillaries and remained at this low level during reperfusion. In contrast, only a slight decrease (<10%) in capillary perfusion was observed after 6 h of cold ischaemia. Pre-ischaemic HTK perfusion had no beneficial effect on tissue perfusion. Both hypothermia and HTK attenuated the significant increase in venular leucocyte–vessel wall interactions, which was observed after 4 h of warm ischaemia in a previous study. Combined application of both interventions had no additional effects. After 6 h of warm ischaemia, no increase in leucocyte–vessel wall interactions was observed, possibly due to venular flow reduction. In conclusion, hypothermia preserves capillary perfusion and prevents an increase in leucocyte–vessel wall interactions during reperfusion after muscle tissue ischaemia. Preischaemic perfusion of the vasculature with HTK does not improve the effects of cold storage on tissue perfusion, but attenuates the inflammatory response independently of temperature effect.

Effect of HTK on the microcirculation in the rat cremaster muscle during warm ischemia and reperfusion

Histidine-tryptophan-ketoglutarate (HTK) preserves rat muscle function during cold storage. We examined the effect of HTK perfusion on preservation of microvascular function during 4 h of warm ischemia and subsequent reperfusion (I/R) in the rat cremaster muscle. Leukocyte-endothelium interactions, capillary perfusion, and arteriole diameters were quantified prior to HTK-perfusion and/or ischemia, and at 0, 1, and 2 h after restoration of blood flow. In all groups, the number of rolling leukocytes increased with time, whereas I/R induced a slight increase in leukocyte adhesion. After ischemia, capillary perfusion rapidly recovered to about 50% and returned to near normal (90%) after 2 h. HTK at 22 degrees C did not affect the assessed microcirculation variables, whereas HTK at 4 degrees C reduced leukocyte rolling, but not adhesion. Therefore, microvascular function of HTK-perfused muscles was not better preserved during warm I/R than that of nonperfused muscles. Contrary to other preservation solutions, HTK perfusion in itself was not detrimental to the microcirculation.