I suppose theoretically it is possible, but not in the practice. The sperm of different species differ from each other by lots of physiological and physical characteristics, such as energy metabolism, concentrations, sperm shape and building, osmotic stress resistance etc. Even in domestic birds there are huge differences among different species. For example, the sperm of chickens can be recovered much easier than the sperm of turkeys.      

ya,there is possibility to recover sperm cells in a minimum injury cryo storage.why because there are lots of morphological,physiological, shape and size changes in the sperm cells of all species.For example rat,mice,rabbit,bull and pigs have specific differences, From all the species have minimum differences. All the species sperm cells are not identical.

Yes, it would be possible; however, one must know the optimal storage medium (semen extender) and freezing conditions (cooling, freezing procedures) as well as thawing conditions for each species. Every species is different.

Thanks  dear Makhsoud, Kanchana and Jack.

To be more clear, I'd like to know, in your opinion, which critical step would the most important for cryosurvival of the sperm cells of any species provided that the best/optimum cryopreservation technique(s) available is/are used.

In animals, for example, the routine freeze-thawing procedures, originally used for the bull (keeping the routinely the semen -extended / glycerolised / equilibrated / packaged-  for 4 cm above the LN2 for 7 min, then plunging into and storing therein for at least one month, within the LN2;  and subsequently thawing at 37+/- 2 degrees C for 1 min) are used for almost all other animal species.

But, we all know that virtually a half of the frozen-thawed sperm cells inevitably die because of the handling procedures (in a broader sense, from the initial collection to the insemination). Some researchers have suggested that it is the osmotic changes that are mostly occurring during and/or after thawing procedures, to blame.

What do you think?

Regards..

I think the current procedures are optimized for industrial-scale production of semen for storage and distribution, not for maximizing the number of spermatozoa that survive the process. One could probably improve survivability by using osmotic gradients during dilution and freezing, but this might not be very practical on on an industrial scale. This is a good question and could be tested on a micro-scale in the laboratory.

Dear Jack, Thanks for your prompt reply on osmotically-based cryoinjury.

Actually, It is a question of the last 20 years (since I started cryosurvival experiments mainly in dogs during my PhD (2000, Bristol-UK; under the supervision of Prof. T.J. Parkinson). Hope that, near future  (with further pinpointed experiments) would bring some answers..

Regards..

In theory, yes, however each organism will require optimized media for cryopreservation and recovery. Even the step by step procedure will have to be fine-tuned to your species of interest. However at this stage we are not there yet.

Just to let you all (interested in SPERM-cryosurvival and acrosome reaction) know of my previously published review (dated 2004) by using almost 100 references (in TURKISH, with English Abstract). Yet, I do NOT have a *clear* answer for almost 50% of dying cells following cryopreservation…

By the way, MANY thanks for all of you out there, replying kindly for the *tough* question of conventional (suboptimal) cryosurvival concerned.

Regards.

As to "which critical step would the most important for cryosurvival of the sperm cells of any species provided that the best/optimum cryopreservation technique(s) available is/are used." my opinion is that the most important step (or factor) which injure the cells during freezing/thawing is formation of ice crystals in the cells, which damage the cell membrane and internal organels. Cryoprotectant toxicity, osmotic shock usually may affect the cells only up to 5-15% but they can be overcome by selecting the appropriate  cryoprotector and its gradient entering,  But the most difficult thing in any technique is to get rid of the formation of ice crystals.    

Dear Makhsud, Thanks for your valuable reply. I agree with that.

In this respect, I personally keep saying that freezing and thawing may be summarized in two words: "Freezing = Dehydration", while "Thawing = Rehydration".

To give some further detail, on what you briefly said above, the two most critical "injuring" factors are the ice formation / nucleation, as especially occurring during the release of the latent heat below the zero degrees C (between -5 to -45 degrees C, or more precisely between -15 and -25 degrees C) and critical osmotic gradient, as occurring particularly across the outer (plasma) membrane (PM) or the inner membranes (of inner&outer acrosomal, nuclear and mitochondrial ones).

Further, semen packed are usually frozen at a freezing rate of 100 (for ampoules and pellets) to -170 (for straws)  degrees C/min(-1), while thawing occurs at  much faster rates: 1000-2000 degrees C/min(-1) C during thawing by conventional method, i.e. at body temperature (around 37 degrees C). For semen, optimal freezing rate varies  between -10 and -80 degrees C/min for the critical temperature zone, between -5 and -45 degrees C. On the other hand, for thawing, a rate of 1000 degrees C/min occurs between -70 to zero degrees C. This basically means that keeping the freezing rate (being rather slow, bearing resultant smaller-sized ice)  in mind, a 10-20 times higher rate of change in the mass formation of cells occurs (during the thawing). A much faster availability of free extracellular water osmotically enforces the membranes to get in at a greater (bulky) sizes. Surely, this kind of great gradient changes in osmotic pressure disrupts the membranes since they cannot easily/readily conduct the movement (conductivity) of water in and out at all occasions.

To add, for glycerolisation (glycerol, as being the most common cryoprotectant), surely, lower concentrations less than 5% would be less toxic (e.g. for acrosome reaction-AR, a concentration of 2 % (v/v, final) was non-toxic for dog sperm).  But, lesser concentrations need lower (slower) freezing rate, especially during the initial stages of the freezing curve (earlier than to reach -5 or -15 degrees C).

Moreover, the PM of sperm cells of many species (e.g. dog, stallion, boar, fox, ram, etc.) have high ratios of unsaturated/saturated fatty acids (making the cells vulnerable to oxidative stress, usually occurs during the membrane damage and/or especially freeze-thawing) and low cholesterol content (related with the elasticity/lipid phase transition of membranes). Considering the "instinctive" high sensitivity of membranes against the oxidative stress (especially following high rates of dilution and improper freeze-thawing steps) and low elasticity of membranes against the osmotic gradient that inevitably occur during freezing, it would be quite hard for the cells to survive afterwards (following cryopreservation).

Above all, minimizing or avoiding the ice nucleation (with smaller-sized crystals) or avoiding the release of the latent heat (the sigmoid part of the freezing curve that usually occur during the initial freezing) would be one of the best approaches to reach a high cryosurvival.

So, what I presume for optimal cryo-survival (and ultimately the highest fertility outcome possible) is that if we; i) choose "good freezer" individuals if possible, ii) practise efficient & fast initial evaluation, iii) extend the semen in optimal diluent at a favourable rate of dilution, iv) use glycerol (or other cryoprotectants, from an organic origin) at low concentrations and to be added in increments at +4 degrees C, v) slow down the initial freezing (or more precisely along with cooling to and equilibrating at 4 degrees C, that would avoid the cold shock, starting at + 17 Degrees C, more efficiently) and thawing rate (much slower than minus 1000-2000 degrees C per min) somehow, we would gain pretty much higher survival (and ultimate fertility) rates, as suggested in the literature.

Surely, effective oestrus detection, promptly-timed insemination by an expert inseminator and proper management (feeding-housing) of mother animals are other pre-requisites for much brighter results.

Any further comments?

Do not forget that, apart from ice or osmotic shock, spermatozoa undergo important changes during the extension/cooling/freezing/thawing/redilution processes. Free radicals, reorganization of the plasmalemma, loss of cholesterol and phospholipids, increased plasmalemma permeability, ionic changes... some authors have combine part of these changes in a term: cryocapacitation. You can obtain viable spermatozoa with compromised functionality, already "capacitated", with DNA damage, etc.

About choosing "good freezers", it might be feasible in some cases, but it might not be a good strategy. Good freezing might be associate to traits other than you are looking for in the offspring. Or you might select good freezer males only to realize, generations later, that you also were losing genetic variability or alleles that could be desirable at the present. In some cases, bad freezer males are genetically important in your program, and you just cannot afford to discard them. That is why an important line of research nowadays is to distinguish good and bad freezers when optimizing protocols.

If you standardized suitable Extender, Cryoprotectant, Co-cryoprotectant, dilution ratio, equilibration time, Freezing protocol and thawing temperature for specific species it is possible. 

Every species, breed and individuals within a breed the sperm vary in their susceptibility to cryopreservation. You have to standardize for better quality post thaw quality for optimum conception or in vitro fertilisation with post thaw sperm. 

Each challenge faced by sperm in the  process of freezing - thawing, always produces the declining quality of sperm population considered as a whole. In this case it should be understood that all processes that must undergo sperm population will not have the same response as the model from which the working protocol is made, but must be adapted to each species. Even relatives, often have differences between them in response to the freeze - thaw (even among individuals of the same species). However, considering the progress that has been made to date in the knowledge of membrane processes and sperm physiology, it may be possible to develop specific protocols for all species. In my personal experience, having worked with sperm from different species, including several wild species, to a greater or lesser extent had always got an answer, at least, encouraging for the conservation of these animals.

No, I don't thing so, because of morphological differences of spermatozoa in different species , they have different cryotolerance potential.

The interest in semen cryopreservation has been since 1776.  Semen cryopreservation has been achieved in wide variety of animal species and human.  Cryopreservation technology has evolved successfully over the past many decades.  With the advent of intracytoplasmic sperm injection, a single sperm is needed for fertilization of the egg.  This technique is very useful in saving many endangered species. Therefore, depending on the species we are talking about I have the confidence to say that sperm can be frozen effectively for further generation for any species. The duration is storage does not affect the frozen sperm quality. Cryopreserved sperm have been used effective after storage of many decades.