Name: proteolytically degraded alginate hydrogels and hydrophobic microbioreactors for porcine oocyte encapsulation
Uploaded: 2020-07-30T13:00:00
Description: Watch this Scientific Journal Video about Proteolytically Degraded Alginate Hydrogels and Hydrophobic Microbioreactors for Porcine Oocyte Encapsulation at JoVE.com

The authors are very grateful to: dr Waclaw Tworzydlo (Department of Developmental Biology and Invertebrate Morphology, Institute of Zoology and Biomedical Research, Jagiellonian University) for technical facilities in TEM; to Ms. Beata Snakowska (Department of Endocrinology, Institute of Zoology and Biomedical Research, Jagiellonian University) for technical assistance; to the Department of Cell Biology and Imaging, Institute of Zoology and Biomedical Research, Jagiellonian University, JEOL JEM 2100HT (JEOL, Tokyo, Japan). This work was supported by grant 2018/29/N/NZ9/00983 from National Science Centre Poland.

The following procedures were approved by the Animal Welfare Committee at the Institute of Zoology and Biomedical Research at Jagiellonian University.
1. Isolation of porcine cumulus-oocyte complexes
<ol>
	<li>To collect material for the isolation of ovarian follicles, excise porcine ovaries from prepubertal gilts (approximately 6-7 months of age, weighing 70 to 80 kg) at a local slaughterhouse. Choose approximately 20 pig ovaries from 10 animals for COCs isolation in each experiment. 
...

The ability to maintain in vitro growth not only of the oocyte but also of cumulus cells surrounding it and simultaneously supporting its maturation is exceedingly essential for the successful assisted reproductive technologies and for furthering the understanding of somatic cell/oocyte interactions especially in species undergoing prolonged follicular growth such as human beings or pigs. Continuously improved IVM techniques are becoming useful tool to preserve reproductive options in cases of polycystic ovarian syndrome...

The development of various culture systems, including three-dimensional (3D) ones, aims to provide optimal conditions for the growth and maturation of oocytes isolated from the follicles even at earliest stages of development. This is of great importance for assisted reproductive techniques (ART), especially in view of the increasing number of women who are struggling with infertility after cancer treatment1. Maturation of oocytes in in vitro conditions (IVM) is already a well-established technique mainly used for in vitro embryo generation for the purpose of livestock reproduction2. However, in most mammalian species, even if high rates of maturation of cumulus-oocyte complexes (COCs) can be achieved (range 60 to 90&#160;%)3, their developmental competence is still inadequate to the needs. This is because the development of the zygotes obtained in such a way even up to the blastocyst stage is low and after the transfer into surrogate animals their viability to term is reduced. Consequently, there is a need to increase the developmental competence of embryos obtained from oocytes that were subjected to the IVM procedure4. Therefore, new maturation media5 are being devised and various periods of in vitro culture are tested6,7 along with supplementation of culture media with various growth factors and molecules8,9.
The first step of any complete IVM system is to create optimal conditions for sustainable growth of oocytes during in vitro culture. The oocyte growth is one of the specific indicators of the oocyte&#39;s ability to resume meiosis10,11. In addition, an appropriate oocyte in vitro culture system must be capable of supporting its nuclear maturation and cytoplasmic differentiation12. The morphology of the cumulus-oocyte complex is another important indicator used in ART clinics to select the best oocyte for subsequent steps of in vitro fertilization (IVF) procedure in humans and livestock12,13. Among morphological characteristics of COCs considered are: the oocyte diameter, its cytoplasm granulation and the first polar body integrity14,15. Besides, the oocyte developmental potential is correlated to the appearance and compaction of cumulus cells and number of their layers surrounding the oocyte. Very important for the appropriate oocyte in vitro culture system is also the maintenance of oocyte&#8211;cumulus cells proper interactions and cytoskeleton stability16,17,18,19. So far, in vitro oocyte growth within human COCs has been demonstrated20. The use of cow COCs also resulted with live births. These were isolated from immature ovarian follicles and then cultured for 14 days until the oocyte was sufficiently large to undergo the IVF procedure21. Similarly, COCs isolated from baboon antral follicles, subjected to IVM after in vitro culture yielded oocytes capable of reinitiating meiosis to the metaphase II stage with a normal appearing spindle structure22. However, in this study the authors did not try to fertilize them. Nevertheless such results indicate that a similar procedure could be applied not only to these particular mammalian species but also to human cumulus-oocyte complexes obtained from follicles what should allow to obtain oocytes of good quality suitable for a successful IVF technique.
The above described results were obtained with the application of conventional IVM protocols during which oocytes were cultured in two-dimensional (2D) systems. The routine procedure in 2D culture systems is covering oocytes, immersed in a drop of an appropriate culture media, with mineral oil23,24. It is assumed that an oil overlay during in vitro oocyte culture serves to prevent liquid evaporation, thus ensuring the maintenance of proper pH and osmotic pressure in the culture. Although such a 2D culture system allows to obtain, even up to 87% of mature pig oocytes25, it has been proven that the mineral oil overlay causes substantial diffusion of lipid soluble materials which are necessary for proper oocytes development26. Additionally, because of steroids (progesterone and estrogens) diffusion into the mineral oil during oocyte culture, a delay of nuclear maturation and reduction in developmental competence achievement of pig oocytes was observed. This may result in obtaining a small number of zygotes, which additionally are characterized by low developmental capacity to the stage of the blastocyst and by poor viability after transfer into recipient animals27. Therefore, attempts are being made to increase the developmental competence of embryos derived from oocytes received after IVM procedure, by creating optimal conditions for achieving both cytoplasmic and nuclear maturity of oocytes cultured together with CCs as complexes, especially using three-dimensional (3D) systems. Various innovative 3D in vitro culture systems have been developed in the last two decades28,29. These were designed to maintain the natural spatial organization of cells and to avoid their flattening in culture dishes what cannot be achieved in the traditional 2D cultures. The structural and functional activity of cultured COCs can be ensured by the maintenance of their proper architecture and undisturbed communication through gap-junctions between various compartments30. The suitability of bio-scaffolds for 3D in vitro culture of cumulus&#8211;oocyte complexes has been evaluated using natural biomaterials such as various components of the extra-cellular matrix (ECM; collagen and hyaluronic acid)31 or inert polymers (alginate)32. These attempts tested in several species brought promising results in terms of oocyte meiosis resumption and achievement of their full competence33,34,35. However so far, no 3D system suitable for COCs maturation isolated from large domestic animals, including pigs, has been developed.
This work describes two protocols that can be used for the 3D culture of porcine COCs. The first protocol describes encapsulation in fibrin-alginate beads (FAB). FAB can be formed by simultaneous mixing an alginate and fibrin solution, which undergo a synchronous gelation process. This combination provides a dynamic mechanical environment because both components contribute to matrix rigidity. A similar solution has been used previously for mouse ovarian follicle culture and maturation36. In the case of the presented protocol, to avoid premature degradation of the alginate-fibrin network, appropriately higher concentrations of calcium chloride solution are used, ensuring a fast and stable gelation process. The dynamic mechanical environment creates conditions similar to these in the natural intra-follicular environment in which COCs reside and increase in size. Additionally, the work shows representative results of COCs 3D culture systems, in which these are suspended in a drop of medium and encapsulated with fluorinated ethylene propylene (FEP; a copolymer of hexafluoropropylene and tetrafluoroethylene) powder particles, to form microbioreactors (Liquid Marbles, LM). LM are a form of 3D bioreactor that have been previously shown to support, among others, growth of living microorganisms37, tumor spheroids38 and embryonic stem cells39. LMs have been also successfully used for sheep oocyte culture40. In most experiments using LMs, bioreactors were prepared using polytetrafluoroethylene (PTFE) powder bed with particle size of 1 &#956;m41. The presented protocol uses FEP, which is very similar in composition and properties to the fluoropolymers PTFE. But FEP is more easily formable and softer than PTFE and what is especially important, it is highly transparent.
Both 3D systems maintain the gaseous in vitro culture environment. They also maintain COCs 3D organization by preventing their flattening and consequent disruption of gap junctions, preserving their functional relationship between the oocyte and surrounding follicular cells.

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	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">General</td>
			<td style="width:139px;"></td>
			<td style="width:162px;"></td>
			<td style="width:204px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:256px;">Antibiotic Antimycotic (100x) 100ml</td>
			<td style="width:139px;">Thermo Fisher</td>
			<td>15240062</td>
			<td style="width:204px;">2.5% final concentration for Handling Medium. 1% in PBS (step 1.2)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:256px;">DMEM/F12 (500ml)</td>
			<td style="width:139px;">Sigma-Aldrich</td>
			<td>D8062</td>
			<td style="width:204px;">Handling and Maturation Medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">DPBS (w/o Ca, Mg), 1x, 500ml</td>
			<td style="width:139px;">Thermo Fisher</td>
			<td>14190144</td>
			<td style="width:204px;"></td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:256px;">FCS (100 ml)</td>
			<td style="width:139px;">Thermo Fisher</td>
			<td>16140063</td>
			<td style="width:204px;">10% final concentration for both Handling Medium and Maturation Medium. (steps: 1.5. 2.6.)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">PBS (1x, pH 7.4) 500ml</td>
			<td style="width:139px;">Thermo Fisher</td>
			<td>10010023</td>
			<td style="width:204px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">TBS Stock Solution (10x, pH 7.4) 500 ml</td>
			<td>Cayman Chemicals</td>
			<td>600232</td>
			<td style="width:204px;">1x final concentration. Other brand can be use</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Maturation Medium</td>
			<td style="width:139px;"></td>
			<td style="width:162px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">hCG (1 VIAL of 10 000 U)</td>
			<td style="width:139px;">Sigma-Aldrich</td>
			<td style="width:162px;">CG10</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">PMSG</td>
			<td style="width:139px;">BioVendor</td>
			<td>RP1782721000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Fibrin-alginate beads</td>
			<td style="width:139px;"></td>
			<td style="width:162px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Alginate Lyase</td>
			<td style="width:139px;">Sigma-Aldrich</td>
			<td style="width:162px;">A1603</td>
			<td>(Step 2.11.1)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Thrombin</td>
			<td style="width:139px;">Sigma-Aldrich</td>
			<td>T9326-150UN</td>
			<td>(Step 2.1)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Calcium Chloride</td>
			<td style="width:139px;">Sigma-Aldrich</td>
			<td style="width:162px;">C5670</td>
			<td>(Step 2.1)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Fibrinogen (250mg)</td>
			<td style="width:139px;">Sigma-Aldrich</td>
			<td style="width:162px;">F3879</td>
			<td>(Step 2.2)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:256px;">Sodium Alginate</td>
			<td style="width:139px;">Sigma-Aldrich</td>
			<td>W201502</td>
			<td style="width:204px;">(Step 2.3) use for alginate solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Liquid Marble</td>
			<td style="width:139px;"></td>
			<td style="width:162px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:256px;">FEP</td>
			<td style="width:139px;">Dyneon GmbH 3M AdMD</td>
			<td style="width:162px;">A-66670</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Morphological examination</td>
			<td style="width:139px;"></td>
			<td style="width:162px;"></td>
			<td></td>
		</tr>
		<tr height="105">
			<td height="105" style="height:104px;width:256px;">LIVE/DEAD Viability/Cytotoxicity Kit, for mammalian cells</td>
			<td style="width:139px;">Thermo Fisher</td>
			<td>L3224</td>
			<td style="width:204px;">(Step 4.1.) Emitted fluorescence: 494 nm for calcein, 528 nm for EthD-1; measure: 517 nm for calcein, 617 nm - EthD-1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">VECTASHIELD Antifade Mounting Medium</td>
			<td style="width:139px;">Vector Laboratories</td>
			<td>H-1000</td>
			<td>mounting medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Ultrastructure examination</td>
			<td style="width:139px;"></td>
			<td style="width:162px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:256px;">Glutaraldehyde solution</td>
			<td style="width:139px;">Sigma-Aldrich</td>
			<td style="width:162px;">G5882</td>
			<td style="width:204px;">2.5% final concentraion (Step 4.2.1.)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">LR White resin</td>
			<td style="width:139px;">Sigma-Aldrich</td>
			<td style="width:162px;">L9774</td>
			<td>(Step 4.2.4.)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Methylene blue</td>
			<td style="width:139px;">Sigma-Aldrich</td>
			<td style="width:162px;">M9140</td>
			<td>(Step 4.2.5.)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Osmium Tetroxide</td>
			<td style="width:139px;">Sigma-Aldrich</td>
			<td style="width:162px;">O5500</td>
			<td>(Step 4.2.3.)</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;">Sodium cacodylate trihydrate</td>
			<td style="width:139px;">Sigma-Aldrich</td>
			<td style="width:162px;">C0250</td>
			<td style="width:204px;">Use for preparing 0.1M sodium cacodylate buffer (pH 7.2)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Uranyl Acetate</td>
			<td style="width:139px;">POCH</td>
			<td>868540111</td>
			<td>(Step 4.2.4.)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Specific instruments, tools</td>
			<td style="width:139px;"></td>
			<td style="width:162px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">30 mm Pteri dish</td>
			<td style="width:139px;">TPP</td>
			<td>93040</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">60 mm IVF Petri dish</td>
			<td style="width:139px;">Falcon</td>
			<td>353653</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:256px;">Ez-Grid Premium Cell Handling Pipettor</td>
			<td style="width:139px;">RI Life Sciences</td>
			<td style="width:162px;">8-72-288</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Ez-Tip</td>
			<td style="width:139px;">RI Life Sciences</td>
			<td style="width:162px;">8-72-4155/20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Heating Table</td>
			<td style="width:139px;">SEMIC</td>
			<td style="width:162px;"></td>
			<td>Other brands can be used</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Incubator</td>
			<td style="width:139px;">Panasonic</td>
			<td style="width:162px;">MCO-170AIC-PE</td>
			<td>Other brands can be used</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Sterile petri dish (10 cm)</td>
			<td>NEST Biotechnology</td>
			<td>704002</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:256px;">Sterile syringe filters with 0.2 &#181;m</td>
			<td style="width:139px;">GOOGLAB SCIENTIFIC</td>
			<td>GB-30-022PES</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Thermos</td>
			<td style="width:139px;">Quechua</td>
			<td>5602589</td>
			<td>Other brands can be used</td>
		</tr>
	</tbody>
</table>

proteolytically degraded alginate hydrogels and hydrophobic microbioreactors for porcine oocyte encapsulation

In reproductive biology, the biotechnology revolution that began with artificial insemination and embryo transfer technology led to the development of assisted reproduction techniques such as oocyte in vitro maturation (IVM), in vitro fertilization (IVF) and cloning of domestic animals by nuclear transfer from somatic cell. IVM is the method particularly of significance. It is the platform technology for the supply of mature, good quality oocytes for applications such as reduction of the generation interval in commercially important or endangered species, research concerning in vitro human reproduction, and production of transgenic animals for cell therapies. The term oocyte quality includes its competence to complete maturation, be fertilized, thereby resulting in healthy offspring. This means that oocytes of good quality are paramount for successful fertilization including IVF procedures. This poses many difficulties to develop a reliable culture method that would support growth not only of human oocytes but also of other large mammalian species. The first step in IVM is the in vitro culture of oocytes. This work describes two protocols for the 3D culture of porcine oocytes. In the first, 3D model cumulus-oocyte complexes (COCs) are encapsulated in a fibrin-alginate bead interpenetrating network, in which a mixture of fibrin and alginate are gelled simultaneously. In the second one, COCs are suspended in a drop of medium and encapsulated with fluorinated ethylene propylene (FEP; a copolymer of hexafluoropropylene and tetrafluoroethylene) powder particles to form microbioreactors defined as Liquid Marbles (LM). Both 3D systems maintain the gaseous in vitro culture environment. They also maintain COCs 3D organization by preventing their flattening and consequent disruption of gap junctions, thereby preserving the functional relationship between the oocyte, and surrounding follicular cells.

In COCs using both IVM systems, the granulosa cells adhered tightly to each other, and most of the recovered COCs had intact layers of cumulus cells (Figure 1A,B). Additionally, substantial proportion of cumulus cells were retained.
The results obtained from the COCs viability analysis confirmed that both systems applied for the encapsulation of porcine oocytes in 3D in vitro conditions ensured optimal growth conditions (Figur...

Watch this Scientific Journal Video about Proteolytically Degraded Alginate Hydrogels and Hydrophobic Microbioreactors for Porcine Oocyte Encapsulation at JoVE.com

Proteolytically Degraded Alginate Hydrogels and Hydrophobic Microbioreactors for Porcine Oocyte Encapsulation

Presented here are two protocols for the encapsulation of porcine oocytes in 3D culture conditions. In the first, cumulus-oocyte complexes (COCs) are encapsulated in fibrin-alginate beads. In the second, they are enclosed with fluorinated ethylene propylene powder particles (microbioreactors). Both systems ensure optimal conditions to maintain their 3D organization.

In reproductive biology, the biotechnology revolution that began with artificial insemination and embryo transfer technology led to the development of ...

This protocol for encapsulation of porcine oocytes makes it possible to maintain spherical organization of COCs. This prevents their flattening and consequent disruption of gap junctions between the oocyte and surrounding follicular cells. The main advantages of the two described protocols are that are user-friendly and allow for effective control of both the oocyte and chemo cell survival.Both of the culture systems are valuable tools for basic research in reproductive biology, and may have clinical relevance for improved infertility treatment. They can also be applied for developing novel biotechnology methods and for livestock improvement. After rinsing the ovaries, transfer them to a beaker filled with HM medium and store them in an incubator at 38 degrees Celsius during all subsequent manipulations.Aspirate the follicular fluid from large porcine follicles and centrifuge it at 100 times G for 10 minutes at room temperature. Then, filter the supernatant using a sterile syringe attached to a 0.2-micrometer membrane pore filter, and snap freeze it at negative 80 degrees Celsius. To isolate the COCs from medium-sized follicles, transfer two to three ovaries to a sterile 10 centimeter Petri dish filled with HM.Gently cut the surface of the protruding ovarian follicles with a sterile surgical number 15 blade, which will cause the follicular fluid and the COCs to flow out into the Petri dish.Aspirate the follicular contents with a 28 gauge needle attached to a disposable syringe, and transfer it into another Petri dish. To prepare the IVF Petri dishes, add one milliliter of HM to the central wells, and place three to four drops of HM in the outer rings. Then use a polycarbonate micropipette to move the undamaged COCs to drops of HM in the outer rings, and briefly rinse them three to four times.When finished, individually transfer them into the central well. Store the IVF plates in the incubator. Prepare thrombin and fibrinogen solutions as described in the text manuscript.On the day of the procedure, slowly thaw the fibrinogen solution on ice, and bring it to room temperature right before use. Mix 0.5%alginate solution and the fibrinogen solution at a one to one ratio for a final volume of two milliliters and gently vortex the mixture. Repair incubation chambers by applying thin strips of paraffin film to glass microscope slides.Pipette 7.5 microliter drops of the FA mixture onto the paraffin film-coated glass slide with separating spacers, placing eight to 10 drops arranged in two rows. Use a micropipette to transfer three to five COCs to the center of the FA drop, along with a minimum volume of maturation medium. Add 7.5 microliters of thrombin solution on top of each FA drop to cover it.There's no need to mix them because the gel forms almost instantaneously. Cover the incubation chamber with a previously prepared glass slide, then turn the chamber upside down and place it in a 100-millimeter Petri dish lined with moist filter paper. Put the Petri dish in the 5%carbon dioxide at 38 degrees Celsius incubator for five to seven minutes.After incubation, transfer each FA capsule into a well of a 96-well plate containing 100 microliters of maturation medium. Every two days, replace half of the medium with fresh pre-equilibrated maturation medium. Image COC is using an inverted light microscope at 10x magnification.After culturing the COCs for four days, remove the maturation medium from the wells and add 100 microliters of 10 international units per milliliter algenate lysate in DMEM. Leave the culture plate in the incubator for 25 to 30 minutes. Remove the COCs from the dissolved capsules.Wash them in DMEM several times, then transfer them to the inner ring of an IVF dish containing PBS. Make a bed of five grams of FEP powder in a 30 millimeter Petri dish. Distribute a single droplet of maturation medium containing three to five COCs onto the FEP powder.Rotate the plate gently in a circular motion to ensure that the particles completely cover the surface of the liquid drop and form liquid marbles, or LMs. Prepare several 60 millimeter IVF Petri dishes, and add three to four milliliters of sterile water to the outer rings to create a humidity chamber. Pick up the formed LM with a 1000 microliter pipette and place it into the central well.Incubate the marbles for four days at 38 degrees Celsius in a five percent carbon dioxide incubator. To change the medium, apply 30 microliters of maturation medium onto each LM, which will cause it to spread. When the marble contents dissolve, transfer the COCs released from the bio-reactor to a drop of fresh maturation medium in the Petri dish.After three to four washes in maturation medium, transfer the COCs, along with 30 microliters of fresh medium, onto the FEP powder bed. Gently rotate the plate in a circular motion to ensure that the powder particles completely cover the surface of the liquid drop and form a new LM.Then, transfer the LM to the IVF Petri dish. Both in vitro maturation systems produced COCs with granulosis cells that were tightly adhered to each other and intact layers of cumulus cells.The COC viability analysis confirmed that optimal growth conditions were achieved in both encapsulation systems. In both groups, only high viability oocytes sites were observed. The oocytes were imaged with transmission electron microscopy.The mitochondria were evenly distributed and had a shell-like shape. Only a few of them were elongated and their clustering was sporadically observed. Endoplasmic reticulum was either associated with mitochondria or free in the oocyte cytoplasm.Liquid droplets appeared as small, dark, round structures, and Golgi apparatus were emerged with dilated cisternae. It is important to be precise and careful when transferring FA capsules from incubation chamber into culture plates and when picking up and transferring format LM into the IVF Petri dish.

proteolytically-degraded-alginate-hydrogels-hydrophobic

Research

JoVE Journal

Biology

Title Cell Encapsulation by Droplets

Primer Extension Capture: Targeted Sequence Retrieval from Heavily Degraded DNA Sources

We present a method of targeted DNA sequence retrieval from DNA sources which are heavily degraded and contaminated with microbial DNA, as is typical of ancient bones. The method greatly reduces sample destruction and sequencing demands relative to direct PCR or shotgun sequencing approaches. We used this method to reconstruct the complete mitochondrial DNA (mtDNA) genomes of five Neandertals from across their geographic range. The mtDNA genetic diversity of the late Neandertals was approximately three times lower than that of contemporary modern humans. Together with analyses of mtDNA protein evolution, these data suggest that the long-term effective population size of Neandertals was smaller than that of modern humans and extant great apes.

We present a method of targeted ancient DNA sequence retrieval, which we used to reconstruct the complete mitochondrial genomes of five Neandertal individuals. Comparison of these sequences with present day humans suggests that Neandertals had a long term low effective population size.

We present a method of targeted DNA sequence retrieval from DNA sources which are heavily degraded and contaminated with microbial DNA, as is typical of ...

Cellular Encapsulation in 3D Hydrogels for Tissue Engineering 

The 3D encapsulation of cells within hydrogels represents an increasingly important and popular technique for culturing cells and towards the development of constructs for tissue engineering. This environment better mimics what cells observe in vivo, compared to standard tissue culture, due to the tissue-like properties and 3D environment. Synthetic polymeric hydrogels are water-swollen networks that can be designed to be stable or to degrade through hydrolysis or proteolysis as new tissue is deposited by encapsulated cells. A wide variety of polymers have been explored for these applications, such as poly(ethylene glycol) and hyaluronic acid. Most commonly, the polymer is functionalized with reactive groups such as methacrylates or acrylates capable of undergoing crosslinking through various mechanisms. In the past decade, much progress has been made in engineering these microenvironments - e.g., via the physical or pendant covalent incorporation of biochemical cues - to improve viability and direct cellular phenotype, including the differentiation of encapsulated stem cells (Burdick et al.).
The following methods for the 3D encapsulation of cells have been optimized in our and other laboratories to maximize cytocompatibility and minimize the number of hydrogel processing steps. In the following protocols (see Figure 1 for an illustration of the procedure), it is assumed that functionalized polymers capable of undergoing crosslinking are already in hand; excellent reviews of polymer chemistry as applied to the field of tissue engineering may be found elsewhere (Burdick et al.) and these methods are compatible with a range of polymer types. Further, the Michael-type addition (see Lutolf et al.) and light-initiated free radical (see Elisseeff et al.) mechanisms focused on here constitute only a small portion of the reported crosslinking techniques. Mixed mode crosslinking, in which a portion of reactive groups is first consumed by addition crosslinking and followed by a radical mechanism, is another commonly used and powerful paradigm for directing the phenotype of encapsulated cells (Khetan et al., Salinas et al.).

Cellular Encapsulation in 3D Hydrogels for Tissue Engineering

We present protocols for the 3-dimensional (3D) encapsulation of cells within synthetic hydrogels. The encapsulation procedure is outlined for two commonly used methods of crosslinking (michael-type addition and light-initiated free radical mechanisms), as well as a number of techniques for assessing encapsulated cell behavior.

The 3D encapsulation of cells within hydrogels represents an increasingly important and popular technique for culturing cells and towards the development ...

PuraMatrix Encapsulation of Cancer Cells

Increasing evidence suggests that culturing cancer cells in three dimensions more accurately recapitulates the complexity of tumor biology. Many of these models utilize reconstituted basement membrane derived from animals which contain a variable amount of growth factors and cytokines that can influence the growth of these cell culture models. Here, we describe in detail the preparation and use of PuraMatrix, a commercially available self assembling peptide gel that is devoid of animal-derived material and pathogens to encapsulate and propagate the ovarian cancer cell line, OVCAR-5. We begin by describing how to prepare the PuraMatrix prior to use. Next, we demonstrate how to properly mix the PuraMatrix and cell suspension to encapsulate the cells in the hydrogel. Upon the addition of cell culture media or injection into a physiological environment, the peptide component of PuraMatrix rapidly self assembles into a 3D hydrogel that exhibits a nanometer scale fibrous structure with an average pore size of 5-200 nm1. In addition, we demonstrate how to propagate cultures grown in encapsulated PuraMatrix. When encapsulated in PuraMatrix, OVCAR-5 cells assemble into three dimensional acinar structures that more closely resemble the morphology of micrometastatic nodules observed in the clinic than monolayer in vitro models. Using confocal microscopy we illustrate the appearance of representative OVCAR-5 cells encapsulated in PuraMatrix on day 1, 3, 5, and 7 post plating. The use of PuraMatrix to culture cancer cells should improve our understanding of the disease and allow us to assess treatment response in more clinically predictive model systems.

This video demonstrates how to encapsulate and culture cancer cells in PuraMatrix, a commercially available self assembling peptide gel.

Increasing evidence suggests that culturing cancer cells in three dimensions more accurately recapitulates the complexity of tumor biology. Many of these ...

Mouse Oocyte Microinjection, Maturation and Ploidy Assessment

Mistakes in chromosome segregation lead to aneuploid cells. In somatic cells, aneuploidy is associated with cancer but in gametes, aneuploidy leads to infertility, miscarriages or developmental disorders like Down syndrome. Haploid gametes form through species-specific developmental programs that are coupled to meiosis. The first meiotic division (MI) is unique to meiosis because sister chromatids remain attached while homologous chromosomes are segregated. For reasons not fully understood, this reductional division is prone to errors and is more commonly the source of aneuploidy than errors in meiosis II (MII) or than errors in male meiosis 1,2. 
In mammals, oocytes arrest at prophase of MI with a large, intact germinal vesicle (GV; nucleus) and only resume meiosis when they receive ovulatory cues. Once meiosis resumes, oocytes complete MI and undergo an asymmetric cell division, arresting again at metaphase of MII. Eggs will not complete MII until they are fertilized by sperm. Oocytes also can undergo meiotic maturation using established in vitro culture conditions 3. Because generation of transgenic and gene-targeted mouse mutants is costly and can take long periods of time, manipulation of female gametes in vitro is a more economical and time-saving strategy. 
Here, we describe methods to isolate prophase-arrested oocytes from mice and for microinjection. Any material of choice may be introduced into the oocyte, but because meiotically-competent oocytes are transcriptionally silent 4,5 cRNA, and not DNA, must be injected for ectopic expression studies. To assess ploidy, we describe our conditions for in vitro maturation of oocytes to MII eggs. Historically, chromosome-spreading techniques are used for counting chromosome number 6. This method is technically challenging and is limited to only identifying hyperploidies. Here, we describe a method to determine hypo-and hyperploidies using intact eggs 7-8. This method uses monastrol, a kinesin-5 inhibitor, that collapses the bipolar spindle into a monopolar spindle 9 thus separating chromosomes such that individual kinetochores can readily be detected and counted by using an anti-CREST autoimmune serum. Because this method is performed in intact eggs, chromosomes are not lost due to operator error.

Oocytes are prone to aneuploidy due to errors in chromosome segregation during meiotic maturation. Aneuploid eggs can cause infertility, miscarriages or developmental disorders like Down syndrome. Here, we describe methods to introduce materials of choice into oocytes and methods to study meiotic maturation and assess ploidy.

Mistakes in chromosome segregation lead to aneuploid cells.  In somatic cells, aneuploidy is associated with cancer but in gametes, aneuploidy leads to ...

Automated Hydrophobic Interaction Chromatography Column Selection for Use in Protein Purification

In contrast to other chromatographic methods for purifying proteins (e.g. gel filtration, affinity, and ion exchange), hydrophobic interaction chromatography (HIC) commonly requires experimental determination (referred to as screening or "scouting") in order to select the most suitable chromatographic medium for purifying a given protein 1. The method presented here describes an automated approach to scouting for an optimal HIC media to be used in protein purification.
HIC separates proteins and other biomolecules from a crude lysate based on differences in hydrophobicity. Similar to affinity chromatography (AC) and ion exchange chromatography (IEX), HIC is capable of concentrating the protein of interest as it progresses through the chromatographic process. Proteins best suited for purification by HIC include those with hydrophobic surface regions and able to withstand exposure to salt concentrations in excess of 2 M ammonium sulfate ((NH4)2SO4). HIC is often chosen as a purification method for proteins lacking an affinity tag, and thus unsuitable for AC, and when IEX fails to provide adequate purification. Hydrophobic moieties on the protein surface temporarily bind to a nonpolar ligand coupled to an inert, immobile matrix. The interaction between protein and ligand are highly dependent on the salt concentration of the buffer flowing through the chromatography column, with high ionic concentrations strengthening the protein-ligand interaction and making the protein immobile (i.e. bound inside the column) 2. As salt concentrations decrease, the protein-ligand interaction dissipates, the protein again becomes mobile and elutes from the column. Several HIC media are commercially available in pre-packed columns, each containing one of several hydrophobic ligands (e.g. S-butyl, butyl, octyl, and phenyl) cross-linked at varying densities to agarose beads of a specific diameter 3. Automated column scouting allows for an efficient approach for determining which HIC media should be employed for future, more exhaustive optimization experiments and protein purification runs 4.
The specific protein being purified here is recombinant green fluorescent protein (GFP); however, the approach may be adapted for purifying other proteins with one or more hydrophobic surface regions. GFP serves as a useful model protein, due to its stability, unique light absorbance peak at 397 nm, and fluorescence when exposed to UV light 5. Bacterial lysate containing wild type GFP was prepared in a high-salt buffer, loaded into a Bio-Rad DuoFlow medium pressure liquid chromatography system, and adsorbed to HiTrap HIC columns containing different HIC media. The protein was eluted from the columns and analyzed by in-line and post-run detection methods. Buffer blending, dynamic sample loop injection, sequential column selection, multi-wavelength analysis, and split fraction eluate collection increased the functionality of the system and reproducibility of the experimental approach.

An automated method for identifying suitable hydrophobic interaction chromatography (HIC) media to be used in the process of protein purification is presented. The method utilizes a medium-pressure liquid chromatography system including automated buffer blending, dynamic sample loop injection, sequential column selection, multi-wavelength analysis, and split fraction eluate collection.

In contrast to other chromatographic methods for purifying proteins (e.g. gel filtration, affinity, and ion exchange), hydrophobic interaction ...

Single Oocyte Bisulfite Mutagenesis

Epigenetics encompasses all heritable and reversible modifications to chromatin that alter gene accessibility, and thus are the primary mechanisms for regulating gene transcription1. DNA methylation is an epigenetic modification that acts predominantly as a repressive mark. Through the covalent addition of a methyl group onto cytosines in CpG dinucleotides, it can recruit additional repressive proteins and histone modifications to initiate processes involved in condensing chromatin and silencing genes2. DNA methylation is essential for normal development as it plays a critical role in developmental programming, cell differentiation, repression of retroviral elements, X-chromosome inactivation and genomic imprinting.
One of the most powerful methods for DNA methylation analysis is bisulfite mutagenesis. Sodium bisulfite is a DNA mutagen that deaminates cytosines into uracils. Following PCR amplification and sequencing, these conversion events are detected as thymines. Methylated cytosines are protected from deamination and thus remain as cytosines, enabling identification of DNA methylation at the individual nucleotide level3. Development of the bisulfite mutagenesis assay has advanced from those originally reported4-6 towards ones that are more sensitive and reproducible7. One key advancement was embedding smaller amounts of DNA in an agarose bead, thereby protecting DNA from the harsh bisulfite treatment8. This enabled methylation analysis to be performed on pools of oocytes and blastocyst-stage embryos9. The most sophisticated bisulfite mutagenesis protocol to date is for individual blastocyst-stage embryos10. However, since blastocysts have on average 64 cells (containing 120-720 pg of genomic DNA), this method is not efficacious for methylation studies on individual oocytes or cleavage-stage embryos.
Taking clues from agarose embedding of minute DNA amounts including oocytes11, here we present a method whereby oocytes are directly embedded in an agarose and lysis solution bead immediately following retrieval and removal of the zona pellucida from the oocyte. This enables us to bypass the two main challenges of single oocyte bisulfite mutagenesis: protecting a minute amount of DNA from degradation, and subsequent loss during the numerous protocol steps. Importantly, as data are obtained from single oocytes, the issue of PCR bias within pools is eliminated. Furthermore, inadvertent cumulus cell contamination is detectable by this method since any sample with more than one methylation pattern may be excluded from analysis12. This protocol provides an improved method for successful and reproducible analyses of DNA methylation at the single-cell level and is ideally suited for individual oocytes as well as cleavage-stage embryos.

Bisulfite mutagenesis is the gold standard for analyzing DNA methylation. Our modified protocol allows for DNA methylation analysis at the single-cell level and was specifically designed for individual oocytes. It can also be used for cleavage-stage embryos.

Epigenetics encompasses all heritable and reversible modifications to chromatin that alter gene accessibility, and thus are the primary mechanisms for ...

Preparation of DNA-crosslinked Polyacrylamide Hydrogels

Mechanobiology is an emerging scientific area that addresses the critical role of physical cues in directing cell morphology and function. For example, the effect of tissue elasticity on cell function is a major area of mechanobiology research because tissue stiffness modulates with disease, development, and injury. Static tissue-mimicking materials, or materials that cannot alter stiffness once cells are plated, are predominately used to investigate the effects of tissue stiffness on cell functions. While information gathered from static studies is valuable, these studies are not indicative of the dynamic nature of the cellular microenvironment in vivo. To better address the effects of dynamic stiffness on cell function, we developed a DNA-crosslinked polyacrylamide hydrogel system (DNA gels). Unlike other dynamic substrates, DNA gels have the ability to decrease or increase in stiffness after fabrication without stimuli. DNA gels consist of DNA crosslinks that are polymerized into a polyacrylamide backbone. Adding and removing crosslinks via delivery of single-stranded DNA allows temporal, spatial, and reversible control of gel elasticity. We have shown in previous reports that dynamic modulation of DNA gel elasticity influences fibroblast and neuron behavior. In this report and video, we provide a schematic that describes the DNA gel crosslinking mechanisms and step-by-step instructions on the preparation DNA gels.

Our laboratory has developed DNA-crosslinked polyacrylamide hydrogels, a dynamic hydrogel system, to better understand the effects of modulating tissue stiffness on cell function. Here, we provide schematics, descriptions, and protocols to prepare these hydrogels.

Mechanobiology is an emerging scientific area that addresses the critical role of physical cues in directing cell morphology and function. For example, ...

FRET Imaging in Three-dimensional Hydrogels

Imaging of F&#246;rster resonance energy transfer (FRET)&#160;is a powerful tool for examining cell biology in real-time. Studies utilizing FRET commonly employ two-dimensional (2D) culture, which does not mimic the three-dimensional (3D) cellular microenvironment. A method to perform quenched emission FRET imaging using conventional widefield epifluorescence microscopy of cells within a 3D hydrogel environment is presented. Here an analysis method for ratiometric FRET probes that yields linear ratios over the probe activation range is described. Measurement of intracellular cyclic adenosine monophosphate (cAMP) levels is demonstrated in chondrocytes under forskolin stimulation using a probe for EPAC1 activation (ICUE1) and the ability to detect differences in cAMP signaling dependent on hydrogel material type, herein a photocrosslinking hydrogel (PC-gel, polyethylene glycol dimethacrylate) and a thermoresponsive hydrogel (TR-gel). Compared with 2D FRET methods, this method requires little additional work. Laboratories already utilizing FRET imaging in 2D can easily adopt this method to perform cellular studies in a 3D microenvironment. It can further be applied to high throughput drug screening in engineered 3D microtissues. Additionally, it is compatible with other forms of FRET imaging, such as anisotropy measurement and fluorescence lifetime imaging (FLIM), and with advanced microscopy platforms using confocal, pulsed, or modulated illumination.

F&#246;rster resonance energy transfer (FRET) imaging is a powerful tool for real-time cell biology studies. Here a method for FRET imaging cells in physiologic three-dimensional (3D) hydrogel microenvironments using conventional epifluorescence microscopy is presented. An analysis for ratiometric FRET probes that yields linear ratios over the activation range is described.

Imaging of F&#246;rster resonance energy transfer (FRET)&#160;is a powerful tool for examining cell biology in real-time. Studies utilizing FRET commonly ...

Fabrication of Amyloid-&#946;-Secreting Alginate Microbeads for Use in Modelling Alzheimer's Disease

According to the amyloid cascade hypothesis, the earliest trigger in the development of Alzheimer&#8217;s disease (AD) is the accumulation of toxic amyloid-&#946; (A&#946;) fragments, eventually leading to the classical features of the disease: amyloid plaques, neurofibrillary tangles and synaptic and neuronal loss. The lack of relevant non-transgenic preclinical models reflective of disease progression is one of the main factors hindering the discovery of effective drug treatments. To this end, we have developed a protocol for the fabrication of alginate microbeads containing amyloid-secreting cells useful for the study of the effects of chronic A&#946; production.
Chinese hamster ovary cells previously transfected with a human APP gene, secreting A&#946; (i.e., 7PA2 cells), were used in this study. A three-dimensional (3D) in vitro model for the sustained release of A&#946; was fabricated by encapsulation of 7PA2 cells in alginate. The process was optimized to target a bead diameter of 500-600 &#956;m for further in vivo studies. Optimization of 7PA2 cell encapsulation in alginate was performed altering fabrication parameters, e.g., alginate concentration, gel flow rate, electrostatic potential, head vibration frequency, gelling solution. Levels of secreted A&#946; were analyzed over time and compared between alginate beads and standard cell culture methods (up to 96 h).
A concentration of 1.5 x 106 7PA2 cells/mL and an alginate concentration of 2% (w/v) buffered with HEPES and subsequent gelation in 0.5 M calcium chloride for 5 min were found to fabricate the most stable microbeads. Fabricated microbeads were 1) of uniform size, 2) with an average diameter of 550 &#956;m, 3) containing about 100-150 cells per microbead and 4) able to secrete A&#946;.
In conclusion, our optimized method for the production of stable alginate microbeads containing amyloid-producing 7PA2 cells might enable the modeling of important aspects of AD both in vitro and in vivo.

This protocol illustrates a cell encapsulation method by rapid physical gelation of alginate to immobilize cells. Obtained microbeads allow controlled and sustained secretion of amyloid-&#946; over time and can be used to study the effects of secreted amyloid-&#946; in in vitro and in vivo models.

According to the amyloid cascade hypothesis, the earliest trigger in the development of Alzheimer&#8217;s disease (AD) is the accumulation of toxic ...