The effect of temperature elevation on cryopreserved mesenchymal stem cells.

BACKGROUND: Cryopreservation is of particular importance in stem cell research and regenerative medicine as it permits long term stabilisation of biological cells. Cells retain their regenerative capacity after years of storage at cryogenic temperatures. However, elevation of temperature may occur due to variety of reasons, for example in the event of equipment malfunction or during delays in transportation. To date, a limited amount research has been carried out to examine the effects of temperature elevation on stem cell survival during cryopreservation. METHODS: Mesenchymal Stem Cells (MSCs) obtained from 8-12 week Sprague Dawley male rats were cryopreserved according to the standard procedures. Under experimental conditions, cryopreserved specimens were exposed to elevated temperatures ranging from -20 C to 37 C and cellular membrane integrity assessed via trypan-blue exclusion at various time points. RESULTS: An approximating model of multiple regression was fitted to the experimental data and optimisation of model parameters was carried out. This model provides an approximation of cell viability in response to elevated temperature conditions. DISCUSSION: The results demonstrate that elevation of temperature has a dramatic effect, even over short periods of time, on the viability of cryopreserved specimens. The model presented here could be used to predict the damage suffered by a specimen due to exposure to elevated temperature over a defined period of time.

Donor, recipient and nerve grafts in brachial plexus reconstruction: anatomical and technical features for facilitating the exposure.

Forty three cadavers of adult and five patients were included in our study. Accessory, suprascapular, musculocutaneous and sural nerves were dissected. These widely used nerves in brachial plexus reconstruction have varying anatomy and still have no standard approach for surgery. Dissection of the accessory nerve in the upper part of the posterior neck triangle was quite complicated took a relatively long time and the nerve could easily be injured. It was found that these shortcomings could be diminished starting dissection of this nerve in the lower part of the posterior neck triangle near the anterior border of trapezius muscle 2 cm (0-3.5) above the clavicle. Accessory nerve entered inner surface of this muscle 3 cm (1-4) from this edge. The proximal portion of the suprascapular nerve was not difficult to identify if post-traumatic scarring is absent. Alternative approach was starting dissection from the junction of C5 and C6 into superior trunk. The suprascapular nerve diverged distally from this junction at 2 cm (0-2.5). The proximal portion of the musculocutaneous nerve was identified by cutting clavicle or tendon of major pectoral muscle. Quicker and less traumatic exposure of this nerve was starting dissection in the bed between biceps and coracobrachialis muscles. The first branches of the musculocutaneous nerve to the biceps brachii muscle took onset 4 cm (3.5-6) distally from the lower margin of the tendon of major pectoral muscle. First branch to the brachial muscle originated from the musculocutaneous nerve distally from the same tendon at 9.4 cm (6.1-10.5). Two main but controversial principles exist in sural nerve graft dissection: time saving and less traumatic approach. Long nerve graft is necessary during brachial plexus reconstruction when many interposition grafts are needed. Technique of multiple (4-7) transverse skin incisions let us to get sural nerve with both branches as long as 66 cm (average 47 cm). Total length of this nerve mainly depended on branching level, which was found to be 27.5 cm (9-35) measuring proximally from the lateral ankle.