Anat Sci Int DOI 10.1007/s12565-014-0245-y
ORIGINAL ARTICLE
Anatomical study of the arterial blood supply to the thoracolumbar spinal cord in guinea pig David Mazensky • Jan Danko • Eva Petrovova Peter Supuka • Anna Supukova
•
Received: 13 February 2014 / Accepted: 13 June 2014 Ó Japanese Association of Anatomists 2014
Abstract Guinea pigs are frequently used as experimental models in studies of ischemic spinal cord injury. The aim of this study was to describe the arterial blood supply to the thoracolumbar spinal cord in 20 adult English self guinea pigs using the corrosion and dissection techniques. The dorsal intercostal arteries arising from the dorsal surface of the thoracic aorta were found as follows: in eight pairs in 70 % of cases, in seven pairs in 20 % of cases and in nine pairs in 10 % of cases. Paired lumbar arteries were present as seven pairs in all the cases. The occurrence of the ventral and dorsal branches of the spinal rami observed in the thoracic and lumbar region was higher on the left than on the right. The artery of Adamkiewicz was present in 60 % of cases as a single vessel and in 40 % of cases as a double vessel. On the dorsal surface of the spinal cord, we found two dorsal spinal arteries in 60 % of cases and three in 40 % of cases. The presence of the artery of Adamkiewicz and nearly regular segmental blood supplying the thoracolumbar part of the spinal cord in all our studied animals is the reason for using guinea pigs as a
D. Mazensky (&) J. Danko E. Petrovova Department of Anatomy, Histology and Physiology, University of Veterinary Medicine and Pharmacy in Kosice, Komenskeho 73, 041 81 Kosice, Slovak Republic e-mail: [email protected] P. Supuka Institute of Nutrition, Dietetics and Feed Production, University of Veterinary Medicine and Pharmacy in Kosice, Komenskeho 73, 041 81 Kosice, Slovak Republic A. Supukova Faculty of Medicine, Institute of Experimental Medicine, Pavol Jozef Safarik University in Kosice, Tr. SNP 1, 040 66 Kosice-Zapad, Slovak Republic
simple model of ischemic damage to the thoracolumbar part of the spinal cord. Keywords Blood supply Corrosion casting Dissection Guinea pigs Spinal cord
Introduction Laboratory animals have been used in several experimental studies on spinal cord damage. More detailed knowledge of the anatomy of the spinal cord blood supply with a focus on all possible variations can contribute to the protection of the spinal cord. Guinea pigs are frequently used as laboratory animals in studies of ischemic spinal cord injury (Duerstock and Borgens 2002; Luo et al. 2002; McBride et al. 2007). The arterial supply of the thoracolumbar part of the spinal cord in guinea pigs has only been described in a few studies (Knox-Macaulay et al. 1960; Soutoul et al. 1964). The blood supply to the central nervous system has been described in several species of laboratory animals (Tveten 1976; Schievink et al. 1988; Strauch et al. 2003, 2007; Mazensky and Danko, 2010) and in humans (Alleyne et al. 1998; Nijenhuis et al. 2004). The aim of this study was to contribute to the knowledge about the arterial supply of the guinea pig spinal cord, with a focus on the thoracolumbar part of the spinal cord, which is most affected by the risk of serious neurological damage. At the same time, we would like to describe some variations in the segmental arterial supply of the spinal cord in the respective regions. We also focused on spinal arteries supplying blood to the dorsal and ventral part of the spinal cord in the corresponding region.
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Materials and methods The study was carried out on 20 adult (age = 220 days) English self guinea pigs of 0.8–1 kg mean weight in an accredited experimental laboratory at the University of Veterinary Medicine and Pharmacy in Kosice, Slovak Republic. The corrosion technique was used for ten guinea pigs (five females and five males) and the dissection technique for ten (five females and five males). The animals were kept in cages under standard conditions (temperature 15–20 °C, relative humidity 45 %, 12 h light period) and fed granular mixed feed (FANTASIA, Tatrapet, Liptovsky Mikulas, Slovak Republic). Drinking water was provided ad libitum. The animals were injected intravenously with heparin (50 000 IU/kg) 30 min before they were killed by intravenous injection of Embutramide (T-61, 0.3 ml/kg). Immediately after killing the animals, the vascular network was perfused with saline. During the manual injection through an ascending aorta, the right ventricle was opened to lower the pressure in the vessels to ensure good injection. Batson’s corrosion casting kit no. 17 ˇ eske´ Budeˇjovice, Czech Republic) was used as a (Dione, C casting medium in 20-ml quantity. After polymerization of the medium (1 h), the guinea pigs were divided into two groups. In the first group, the maceration technique was carried out in 2–4 % KOH solution for 2 days at 60–70 °C. In the second group (dissection technique), 10 % formaldehyde was injected into the vertebral canal between the last lumbar vertebra and sacrum and between the last cervical and first thoracic vertebra to fix the spinal cord. One week after the fixation, the vertebral canal was opened by removing the vertebral arches in the thoracic, lumbar and sacral spinal regions. The prepared spinal cord was fixed in 10 % formaldehyde. We certify that all applicable institutional and governmental regulations concerning the ethical use of animals were followed during the course of this research.
Fig. 1 Origin of the dorsal intercostal artery. 1 Thoracic aorta; 2 independent origin of the dorsal intercostal artery; 3 origin of the dorsal intercostal artery by means of a common trunk with division in the craniocaudal direction; 4 origin of the dorsal intercostal artery by means of a common trunk with division in the right-left direction. Dorsal view. Magnification 95
Results The thoracic part of the spinal cord received the oxygenated blood by means of the spinal rami arising as branches from the dorsal intercostal artery (Fig. 1). Twelve intercostal arteries were present. These branches, arising from the dorsal surface of the thoracic aorta, were found in 8 pairs in 70 % of cases, 7 pairs in 20 % cases and 9 pairs in 10 % of cases. The rest of the dorsal intercostal arteries branched from the supreme intercostal artery. In 70 % of cases, the arteries originated from a common trunk. The common trunk was divided in the right-left direction in 60 % of cases and in the craniocaudal direction in 40 % of cases. The formation of a common trunk showed a high
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Fig. 2 Origin of the lumbar artery. 1 Abdominal aorta; 2 independent origin of the lumbar artery. Dorsal view. Magnification 95
degree of variability. It was formed by two dorsal intercostal arteries in four cases, three arteries in one case, four arteries in one case and five arteries in one case. In 30 % of cases, both the right- and left-sided arteries originated independently from the same level.
Spinal cord arteries in guinea pig
The lumbar part of the spinal cord was supplied by the spinal rami arising from the paired lumbar arteries, which originated from the dorsal surface of the abdominal aorta. They were present in seven pairs in all the cases. The first six pairs arose from the abdominal aorta and the last one from the median sacral artery. In one case, the two last pairs originated from the median sacral artery, and in one case all 7 pairs originated from the abdominal aorta. In 60 % of cases, the lumbar arteries originated from a common trunk with division in the right-left direction. In 40 % of cases, both the right- and left-sided arteries originated independently at the same level (Fig. 2). The spinal rami as branches arising from the dorsal intercostal artery and lumbar artery entered the vertebral canal through the intervertebral foramen. Their entrance was associated with the respective spinal nerve root. The spinal rami were divided after entering the vertebral canal in the dorsal and ventral branch. The ventral branches entered the ventral spinal artery. The occurrence of individual ventral branches is shown in Table 1. The ventral spinal artery ran subdurally in the ventral median fissure of the spinal cord. The presence of branches entering the ventral spinal artery in the thoracic region was observed in 69.5 % of cases on the left side and in 30.5 % on the right Table 1 Occurrence of ventral branches of the arterial spinal branches in the thoracolumbar region of the spinal cord (dissection technique; ten guinea pigs) Occurrence of arterial spinal branches (number of blood vessels) Level
Right
Left
Th1
3
6
Th 2
3
3
Th 3
3
10
Th 4
0
3
Th 5
0
5
Th 6
5
5
Th 7
0
3
Th 8
3
6
Th 9
0
5
Th 10
5
5
Th 11
3
3
Th 12
0
3
L1
0
0
L2 L3
0 3
9 0
L4
6
3
L5
5
5
L6
5
0
L7
3
9
L Lumbar segment of the spinal cord; Th thoracic segment of the spinal cord
side. In the lumbar region, left-sided ventral branches were observed in 54.2 % of cases and right sided in 45.8 % of cases. Along the entire thoracic and lumbar spinal regions, we observed left-sided branches in 63.8 % and right-sided branches in 36.2 % of cases, which was most likely related to left-sided localization of the aorta. Except for relatively small and weak segmental spinal arteries, we found a larger feeding artery arising from the spinal ramus of the left fifth lumbar artery in 60 % of cases (Fig. 3). In 30 % of cases, the artery of Adamkiewicz was doubled with two different levels of origin. The right-sided artery originated from the spinal ramus of the fifth lumbar artery and the left sided from the spinal ramus of the fourth lumbar artery (Fig. 4). In 10 % of cases, the artery of Adamkiewicz originated from the spinal ramus of the right and left fifth lumbar artery. These two arteries continued separately caudally on the ventral surface of the spinal cord. At the level of the sixth lumbar artery, they fused together and continued caudally as the ventral spinal artery. They communicated by means of a communicating branch at the level of the spinal ramus of the fifth lumbar artery and sent weak branches cranially entering the ventral spinal artery (Fig. 5). In all of the cases, the artery of Adamkiewicz entered the ventral spinal artery. On the dorsal surface, we found two irregular longitudinal dorsal spinal arteries lying bilaterally in the lateral dorsal sulcus in 60 % of cases (Fig. 6). They received the dorsal branches of the spinal rami. In 40 % of cases, three irregular longitudinal dorsal spinal arteries receiving the dorsal branches of the spinal rami were present (Fig. 7). The third dorsal spinal artery was located in the dorsal sulcus. The occurrence of individual dorsal branches is
Fig. 3 Left-sided localization of the artery of Adamkiewicz. 1 Ventral spinal artery; 2 artery of Adamkiewicz. Ventral view. Magnification 98
Fig. 4 Doubled artery of Adamkiewicz. 1 Ventral spinal artery; 2 right-sided artery of Adamkiewicz; 3 left-sided artery of Adamkiewicz. Ventral view. Magnification 98
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D. Mazensky et al. Table 2 Occurrence of dorsal branches of the arterial spinal branches in the thoracolumbar region of the spinal cord (dissection technique; ten guinea pigs) Occurrence of arterial spinal branches (number of blood vessels) Level
Fig. 5 Doubled artery of Adamkiewicz. 1 Ventral spinal artery; 2 right-sided artery of Adamkiewicz; 3 left-sided artery of Adamkiewicz; 4 communicating branch. Ventral view. Magnification 912.5
Fig. 6 Presence of two longitudinal dorsal spinal arteries. 1 Dorsal spinal artery. Dorsal view. Magnification 912.5
Right
Left
Th1
5
5
Th 2
5
6
Th 3
3
3
Th 4
0
3
Th 5
3
5
Th 6
3
3
Th 7
3
5
Th 8
3
0
Th 9
1
3
Th 10
3
5
Th 11
3
9
Th 12
6
3
L1
5
3
L2 L3
3 0
3 3
L4
0
3
L5
0
6
L6
9
10
L7
3
10
L Lumbar segment of the spinal cord; Th thoracic segment of the spinal cord
Fig. 7 Presence of three longitudinal dorsal spinal arteries. 1 Dorsal spinal artery. Dorsal view. Magnification 912.5
shown in Table 2. When two irregular dorsal spinal arteries were present, they were formed only by fusion of the small cranial and caudal branches arising from the dorsal branches. Among the dorsal branches observed in the thoracic region, 51.5 % were left sided and 48.5 % right sided. In the lumbar region, the observed dorsal branches were left sided in 65.5 % of cases and right sided in 34.5 % of cases. Along the entire thoracic and lumbar spinal regions, the branches were left sided in 56.8 % of cases and right sided in 43.2 % of cases. Based on our results, we can conclude that there is high variability in the blood supply in the thoracolumbar part of the spinal cord in guinea pigs.
Discussion In operations on thoracoabdominal aneurysms, the arrangement of the origin of the segmental dorsal
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intercostal and lumbar arteries has a very important role (Etz et al. 2006). The risk of spinal cord ischemia, which can lead to paraplegia, is decreased by performing reimplantation of the segmental arteries correctly (Grabitz et al. 1996). Shively and Stump (1974) found that the number of dorsal intercostal arteries supplied by the costocervical trunk and the highest intercostal artery is not consistent from animal to animal. In this study, it varied from four to seven on each side with only the first and occasionally the second one coming directly from the costocervical trunk and the remainder from the highest intercostal artery. There are typically 12 pairs of dorsal intercostal arteries, and the rest are direct branches from the thoracic aorta. Dorsal intercostal arteries were described as paired segmental branches with an independent origin arising from the thoracic aorta (Nejedly 1965; Popesko 1990). Shively and Stump (1975) described two types of origin of seven pairs of lumbar arteries from the abdominal aorta: an independent origin and one from the common trunk of the arteries at the same level. Other authors found the lumbar arteries as segmental paired branches arising from the dorsal surface of the abdominal aorta (Nejedly 1965; Popesko 1990). Dogs, rats, pigs, rabbits and mice have been used as experimental animals in the study of ischemic spinal cord
Spinal cord arteries in guinea pig
damage. In dogs, high variability was described in the density of the arteries forming the spinal arterial ring and in the frequency of occurrence of the spinal rami arising from the radicular arteries (Pais et al. 2007). Rat is one of the most used experimental animals in the study of spinal cord injury; therefore, the blood supply of the rat spinal cord is probably the most profusely documented, but the results differ (Brightman 1956; Woollam and Millen 1955; Soutoul et al. 1964; Schievink et al. 1988). Commonly two dorsal spinal arteries have been found in the rat (Lazorthes et al. 1971), but in albino Wistar rats, they were less constant (Woollam and Millen 1955). The variations and presence of the extrasegmental arteries of the spinal cord blood supply have been described in the pig (Strauch et al. 2003). In the rabbit, the variability of the spinal cord blood supply was described in all segments of the spinal cord. The presence of ventral and dorsal branches of the spinal arteries in the cervical segment of the spinal cord in rabbits was observed on the right side in 46.2 % of cases and on the left side in 53.8 % of cases. Along the entire thoracolumbar segment of the spinal cord in rabbit, the ventral branches of the spinal arteries were left sided in 62.5 % of cases and right sided in 37.5 % of cases (Mazensky et al. 2011), and the dorsal branches were left sided in 56.5 % of cases and right sided in 43.5 % of cases (Mazensky et al. 2013). In the mouse, the spinal cord blood supply has only been partially described (Lang-Lazdunski et al. 2000). On the dorsal surface of the spinal cord we found two or three irregular longitudinal dorsal spinal arteries (in humans the posterior spinal arteries). In humans, the posterior spinal arteries are normally continuous in the cranial to caudal direction (Cheshire et al. 1996). In dogs, four dorsal spinal arteries were described on the dorsal surface of the spinal cord. These were divided into two pairs. Each pair was formed by a larger caliber lateral dorsal spinal artery and a thinner medial dorsal spinal artery (Pais et al. 2007). Two much less constant dorsal spinal arteries forming irregular connections between each other were described in rats (Woollam and Millen 1955). The dorsal spinal arteries in the cervical segment of the spinal cord in rabbit were present in numbers of two or they were absent (Mazensky et al. 2012), and in the thoracolumbar segment they were present in numbers of two or three or were absent (Mazensky et al. 2013). The number of dorsal spinal arteries in mouse differs from study to study. Lang-Lazdunski et al. (2000) found two dorsal spinal arteries, but Bilgen and Al-Hafez (2006) described only one single artery. Our results indicate high variability in the presence of dorsal and ventral branches supplying blood to the spinal cord. On the left side, they occurred in higher numbers. The segmental arteries of the thoracic and lumbar part of the spinal cord ensured the supply of the respective
segments of the ventral spinal artery and dorsal spinal artery. Segmental arteries in the lumbar part of the spinal cord occurred irregularly, and their absence was noted more frequently than in the thoracic part, which allowed us to assume a higher risk of irreparable ischemic damage to the lumbar part of the spinal cord in the guinea pig. Till now, only sporadic published works have dealt with the study of the spinal cord blood supply in guinea pigs. Soutoul et al. (1964) studied the spinal cord blood supply in several species, but the presence of the artery of Adamkiewicz, its level of origin and the frequency of the occurrence of spinal branches in the guinea pig have not been described. Knox-Macaulay et al. (1960) only described the number of radicular arteries in the thoracic part of the spinal cord as five to seven and in the lumbar part noticed a great variation in the number. The ventral spinal artery was described as a vessel sometimes interrupted in its course. We found this artery to be an uninterrupted trunk. The dorsal spinal arteries were seen as two smaller anastomotic chains of arteries running in the dorsolateral sulcus. In our study, the number of dorsal spinal arteries varied from two to three. In this study, the artery of Adamkiewicz was described as a double artery originating from the spinal branch of the third or fourth lumbar artery. We found the artery of Adamkiewicz as a single or double vessel with different levels of origin. The artery of Adamkiewicz was only present in half of the dog specimens (Pais et al. 2007). In rat, the artery of Adamkiewicz was described in all cases (Brightman 1956; Woollam and Millen 1955; Soutoul et al. 1964; Gouaze´ et al. 1965), but many works doubt the presence of the artery of Adamkiewicz in rat (Tveten 1976; Schievink et al. 1988). In pig, the artery of Adamkiewicz was not recorded (Strauch et al. 2003, 2007). In rabbit, the artery of Adamkiewicz was described as left sided in 50 % of cases and right sided in 50 % of cases (Mazensky et al. 2011). The presence of the artery of Adamkiewicz was also described in the mouse (Lang-Lazdunski et al. 2000). In humans, the artery of Adamkiewicz is always present (Milen et al. 1999). Animal models, especially rodent models, are designed to help predict the functional outcomes of neurological disorders and injuries. Many of the behavioral outcomes appear in parallel to the clinical symptoms observed in human patients to a remarkable degree. Understanding the strengths and limitations of the models will allow more relevant analysis of the injury, behavioral sequelae and therapeutic approaches. Each aspect of a study should be planned before the experiment is begun (Geissler et al. 2013). Understanding the vascular blood supply to the spinal cord is important to avoid spinal cord ischemia or infarction during surgical approaches to the spine (Gao et al. 2013). The presence of the artery of Adamkiewicz
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and nearly regular segmental blood supply of the thoracolumbar part of the spinal cord in all of our studied animals is the reason for using guinea pigs as a simple model of ischemic damage of the thoracolumbar part of the spinal cord. Acknowledgments The present study was carried out within the framework of project VEGA MSˇ SR no. 1/0111/13 of the Slovak Ministry of Education. Conflict of interest The authors have no financial or personal relationships related to the article. The authors declare no conflict of interest.
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of the anastomotic substitution pathways. J Neurosurg 35:253–262 Luo J, Li N, Robinson JP, Shi R (2002) The increase of reactive oxygen species and their inhibition in an isolated guinea pig spinal cord compression model. Spinal Cord 40:656–665 Mazensky D, Danko J (2010) The importance of the origin of vertebral arteries in cerebral ischemia in the rabbit. Anat Sci Int 85:102–104 Mazensky D, Radonak J, Danko J, Petrovova E, Frankovicova M (2011) Anatomical study of blood supply to the spinal cord in the rabbit. Spinal Cord 49:525–528 Mazensky D, Danko J, Petrovova E, Luptakova L, Radonak J, Schusterova´ I (2012) Arterial arrangement of the cervical spinal cord in rabbit. Anat Sci Int 87:155–159 Mazensky D, Danko J, Petrovova E, Mechirova E, Prokes M (2013) Arterial peculiarities of the thoracolumbar spinal cord in rabbit. Anat Histol Embryol. doi:10.1111/ahe.12081 McBride JM, Smith DT, Byrn SR, Borgens RB, Shi R (2007) 4-Aminopyridine derivatives enhance impulse conduction in guinea-pig spinal cord following traumatic injury. Neuroscience 148:44–52 Milen MT, Bloom DA, Culligan J (1999) Albert Adamkiewicz (1850–1921)—his artery and its significance for the retroperitoneal surgeon. World J Urol 17:168–170 Nejedly K (1965) Biology and systematic anatomy of laboratory animals. SPN, Prague Nijenhuis RJ, Leiner T, Cornips EM (2004) Spinal cord feeding arteries at MR angiography for thoracoscopic spinal surgery: feasibility study and implications for surgical approach. Radiology 233:541–547 Pais D, Casal D, Arantes M, Casimiro M, O’Neill JG (2007) Spinal cord arteries in Canis familiaris and their variations: implications in experimental procedures. Braz J Morphol Sci 24:224–228 Popesko P (1990) Anatomic atlas of small laboratory animals. Priroda, Bratislava Schievink WI, Luyendijk W, Los JA (1988) Does the artery of Adamkiewicz exist in the albino rat? J Anat 161:95–101 Shively MJ, Stump JE (1974) The systemic arterial pattern of the guinea pig: the head, thorax, and thoracic limb. Am J Anat 139:269–284 Shively MJ, Stump JE (1975) The systemic arterial pattern of the guinea pig: the abdomen. Anat Rec 182:355–366 Soutoul JH, Gouaz’e A, Castaing J (1964) Les arte`res de la moelle e´pinie`re des animaux d’expe´rimentation. III.—e´tude comparative du rat, cobaye, lapin, chat, chien, orang-outang, chimpnaze´, avec l’homme et le foetus (in French). Path Biol 12:950–962 Strauch JT, Spielvogel D, Lauten A et al (2003) Importance of extrasegmental vessels for spinal cord blood supply in a chronic porcine model. Eur J Cardiothorac Surg 24:817–824 Strauch JT, Lauten A, Zhang N, Wahlers T, Griepp RB (2007) Anatomy of spinal cord blood supply in the pig. Ann Thorac Surg 83:2130–2134 Tveten L (1976) Spinal cord vascularity IV. The spinal cord arteries in the rat. Acta Radiol (diagnosis) 17:385–398 Woollam DHM, Millen JW (1955) The arterial supply of the spinal cord and its significance. J Neurol Neurosurg Psychiatry 18:97–102
ORIGINAL ARTICLE
Anatomical study of the arterial blood supply to the thoracolumbar spinal cord in guinea pig David Mazensky • Jan Danko • Eva Petrovova Peter Supuka • Anna Supukova
•
Received: 13 February 2014 / Accepted: 13 June 2014 Ó Japanese Association of Anatomists 2014
Abstract Guinea pigs are frequently used as experimental models in studies of ischemic spinal cord injury. The aim of this study was to describe the arterial blood supply to the thoracolumbar spinal cord in 20 adult English self guinea pigs using the corrosion and dissection techniques. The dorsal intercostal arteries arising from the dorsal surface of the thoracic aorta were found as follows: in eight pairs in 70 % of cases, in seven pairs in 20 % of cases and in nine pairs in 10 % of cases. Paired lumbar arteries were present as seven pairs in all the cases. The occurrence of the ventral and dorsal branches of the spinal rami observed in the thoracic and lumbar region was higher on the left than on the right. The artery of Adamkiewicz was present in 60 % of cases as a single vessel and in 40 % of cases as a double vessel. On the dorsal surface of the spinal cord, we found two dorsal spinal arteries in 60 % of cases and three in 40 % of cases. The presence of the artery of Adamkiewicz and nearly regular segmental blood supplying the thoracolumbar part of the spinal cord in all our studied animals is the reason for using guinea pigs as a
D. Mazensky (&) J. Danko E. Petrovova Department of Anatomy, Histology and Physiology, University of Veterinary Medicine and Pharmacy in Kosice, Komenskeho 73, 041 81 Kosice, Slovak Republic e-mail: [email protected] P. Supuka Institute of Nutrition, Dietetics and Feed Production, University of Veterinary Medicine and Pharmacy in Kosice, Komenskeho 73, 041 81 Kosice, Slovak Republic A. Supukova Faculty of Medicine, Institute of Experimental Medicine, Pavol Jozef Safarik University in Kosice, Tr. SNP 1, 040 66 Kosice-Zapad, Slovak Republic
simple model of ischemic damage to the thoracolumbar part of the spinal cord. Keywords Blood supply Corrosion casting Dissection Guinea pigs Spinal cord
Introduction Laboratory animals have been used in several experimental studies on spinal cord damage. More detailed knowledge of the anatomy of the spinal cord blood supply with a focus on all possible variations can contribute to the protection of the spinal cord. Guinea pigs are frequently used as laboratory animals in studies of ischemic spinal cord injury (Duerstock and Borgens 2002; Luo et al. 2002; McBride et al. 2007). The arterial supply of the thoracolumbar part of the spinal cord in guinea pigs has only been described in a few studies (Knox-Macaulay et al. 1960; Soutoul et al. 1964). The blood supply to the central nervous system has been described in several species of laboratory animals (Tveten 1976; Schievink et al. 1988; Strauch et al. 2003, 2007; Mazensky and Danko, 2010) and in humans (Alleyne et al. 1998; Nijenhuis et al. 2004). The aim of this study was to contribute to the knowledge about the arterial supply of the guinea pig spinal cord, with a focus on the thoracolumbar part of the spinal cord, which is most affected by the risk of serious neurological damage. At the same time, we would like to describe some variations in the segmental arterial supply of the spinal cord in the respective regions. We also focused on spinal arteries supplying blood to the dorsal and ventral part of the spinal cord in the corresponding region.
123
D. Mazensky et al.
Materials and methods The study was carried out on 20 adult (age = 220 days) English self guinea pigs of 0.8–1 kg mean weight in an accredited experimental laboratory at the University of Veterinary Medicine and Pharmacy in Kosice, Slovak Republic. The corrosion technique was used for ten guinea pigs (five females and five males) and the dissection technique for ten (five females and five males). The animals were kept in cages under standard conditions (temperature 15–20 °C, relative humidity 45 %, 12 h light period) and fed granular mixed feed (FANTASIA, Tatrapet, Liptovsky Mikulas, Slovak Republic). Drinking water was provided ad libitum. The animals were injected intravenously with heparin (50 000 IU/kg) 30 min before they were killed by intravenous injection of Embutramide (T-61, 0.3 ml/kg). Immediately after killing the animals, the vascular network was perfused with saline. During the manual injection through an ascending aorta, the right ventricle was opened to lower the pressure in the vessels to ensure good injection. Batson’s corrosion casting kit no. 17 ˇ eske´ Budeˇjovice, Czech Republic) was used as a (Dione, C casting medium in 20-ml quantity. After polymerization of the medium (1 h), the guinea pigs were divided into two groups. In the first group, the maceration technique was carried out in 2–4 % KOH solution for 2 days at 60–70 °C. In the second group (dissection technique), 10 % formaldehyde was injected into the vertebral canal between the last lumbar vertebra and sacrum and between the last cervical and first thoracic vertebra to fix the spinal cord. One week after the fixation, the vertebral canal was opened by removing the vertebral arches in the thoracic, lumbar and sacral spinal regions. The prepared spinal cord was fixed in 10 % formaldehyde. We certify that all applicable institutional and governmental regulations concerning the ethical use of animals were followed during the course of this research.
Fig. 1 Origin of the dorsal intercostal artery. 1 Thoracic aorta; 2 independent origin of the dorsal intercostal artery; 3 origin of the dorsal intercostal artery by means of a common trunk with division in the craniocaudal direction; 4 origin of the dorsal intercostal artery by means of a common trunk with division in the right-left direction. Dorsal view. Magnification 95
Results The thoracic part of the spinal cord received the oxygenated blood by means of the spinal rami arising as branches from the dorsal intercostal artery (Fig. 1). Twelve intercostal arteries were present. These branches, arising from the dorsal surface of the thoracic aorta, were found in 8 pairs in 70 % of cases, 7 pairs in 20 % cases and 9 pairs in 10 % of cases. The rest of the dorsal intercostal arteries branched from the supreme intercostal artery. In 70 % of cases, the arteries originated from a common trunk. The common trunk was divided in the right-left direction in 60 % of cases and in the craniocaudal direction in 40 % of cases. The formation of a common trunk showed a high
123
Fig. 2 Origin of the lumbar artery. 1 Abdominal aorta; 2 independent origin of the lumbar artery. Dorsal view. Magnification 95
degree of variability. It was formed by two dorsal intercostal arteries in four cases, three arteries in one case, four arteries in one case and five arteries in one case. In 30 % of cases, both the right- and left-sided arteries originated independently from the same level.
Spinal cord arteries in guinea pig
The lumbar part of the spinal cord was supplied by the spinal rami arising from the paired lumbar arteries, which originated from the dorsal surface of the abdominal aorta. They were present in seven pairs in all the cases. The first six pairs arose from the abdominal aorta and the last one from the median sacral artery. In one case, the two last pairs originated from the median sacral artery, and in one case all 7 pairs originated from the abdominal aorta. In 60 % of cases, the lumbar arteries originated from a common trunk with division in the right-left direction. In 40 % of cases, both the right- and left-sided arteries originated independently at the same level (Fig. 2). The spinal rami as branches arising from the dorsal intercostal artery and lumbar artery entered the vertebral canal through the intervertebral foramen. Their entrance was associated with the respective spinal nerve root. The spinal rami were divided after entering the vertebral canal in the dorsal and ventral branch. The ventral branches entered the ventral spinal artery. The occurrence of individual ventral branches is shown in Table 1. The ventral spinal artery ran subdurally in the ventral median fissure of the spinal cord. The presence of branches entering the ventral spinal artery in the thoracic region was observed in 69.5 % of cases on the left side and in 30.5 % on the right Table 1 Occurrence of ventral branches of the arterial spinal branches in the thoracolumbar region of the spinal cord (dissection technique; ten guinea pigs) Occurrence of arterial spinal branches (number of blood vessels) Level
Right
Left
Th1
3
6
Th 2
3
3
Th 3
3
10
Th 4
0
3
Th 5
0
5
Th 6
5
5
Th 7
0
3
Th 8
3
6
Th 9
0
5
Th 10
5
5
Th 11
3
3
Th 12
0
3
L1
0
0
L2 L3
0 3
9 0
L4
6
3
L5
5
5
L6
5
0
L7
3
9
L Lumbar segment of the spinal cord; Th thoracic segment of the spinal cord
side. In the lumbar region, left-sided ventral branches were observed in 54.2 % of cases and right sided in 45.8 % of cases. Along the entire thoracic and lumbar spinal regions, we observed left-sided branches in 63.8 % and right-sided branches in 36.2 % of cases, which was most likely related to left-sided localization of the aorta. Except for relatively small and weak segmental spinal arteries, we found a larger feeding artery arising from the spinal ramus of the left fifth lumbar artery in 60 % of cases (Fig. 3). In 30 % of cases, the artery of Adamkiewicz was doubled with two different levels of origin. The right-sided artery originated from the spinal ramus of the fifth lumbar artery and the left sided from the spinal ramus of the fourth lumbar artery (Fig. 4). In 10 % of cases, the artery of Adamkiewicz originated from the spinal ramus of the right and left fifth lumbar artery. These two arteries continued separately caudally on the ventral surface of the spinal cord. At the level of the sixth lumbar artery, they fused together and continued caudally as the ventral spinal artery. They communicated by means of a communicating branch at the level of the spinal ramus of the fifth lumbar artery and sent weak branches cranially entering the ventral spinal artery (Fig. 5). In all of the cases, the artery of Adamkiewicz entered the ventral spinal artery. On the dorsal surface, we found two irregular longitudinal dorsal spinal arteries lying bilaterally in the lateral dorsal sulcus in 60 % of cases (Fig. 6). They received the dorsal branches of the spinal rami. In 40 % of cases, three irregular longitudinal dorsal spinal arteries receiving the dorsal branches of the spinal rami were present (Fig. 7). The third dorsal spinal artery was located in the dorsal sulcus. The occurrence of individual dorsal branches is
Fig. 3 Left-sided localization of the artery of Adamkiewicz. 1 Ventral spinal artery; 2 artery of Adamkiewicz. Ventral view. Magnification 98
Fig. 4 Doubled artery of Adamkiewicz. 1 Ventral spinal artery; 2 right-sided artery of Adamkiewicz; 3 left-sided artery of Adamkiewicz. Ventral view. Magnification 98
123
D. Mazensky et al. Table 2 Occurrence of dorsal branches of the arterial spinal branches in the thoracolumbar region of the spinal cord (dissection technique; ten guinea pigs) Occurrence of arterial spinal branches (number of blood vessels) Level
Fig. 5 Doubled artery of Adamkiewicz. 1 Ventral spinal artery; 2 right-sided artery of Adamkiewicz; 3 left-sided artery of Adamkiewicz; 4 communicating branch. Ventral view. Magnification 912.5
Fig. 6 Presence of two longitudinal dorsal spinal arteries. 1 Dorsal spinal artery. Dorsal view. Magnification 912.5
Right
Left
Th1
5
5
Th 2
5
6
Th 3
3
3
Th 4
0
3
Th 5
3
5
Th 6
3
3
Th 7
3
5
Th 8
3
0
Th 9
1
3
Th 10
3
5
Th 11
3
9
Th 12
6
3
L1
5
3
L2 L3
3 0
3 3
L4
0
3
L5
0
6
L6
9
10
L7
3
10
L Lumbar segment of the spinal cord; Th thoracic segment of the spinal cord
Fig. 7 Presence of three longitudinal dorsal spinal arteries. 1 Dorsal spinal artery. Dorsal view. Magnification 912.5
shown in Table 2. When two irregular dorsal spinal arteries were present, they were formed only by fusion of the small cranial and caudal branches arising from the dorsal branches. Among the dorsal branches observed in the thoracic region, 51.5 % were left sided and 48.5 % right sided. In the lumbar region, the observed dorsal branches were left sided in 65.5 % of cases and right sided in 34.5 % of cases. Along the entire thoracic and lumbar spinal regions, the branches were left sided in 56.8 % of cases and right sided in 43.2 % of cases. Based on our results, we can conclude that there is high variability in the blood supply in the thoracolumbar part of the spinal cord in guinea pigs.
Discussion In operations on thoracoabdominal aneurysms, the arrangement of the origin of the segmental dorsal
123
intercostal and lumbar arteries has a very important role (Etz et al. 2006). The risk of spinal cord ischemia, which can lead to paraplegia, is decreased by performing reimplantation of the segmental arteries correctly (Grabitz et al. 1996). Shively and Stump (1974) found that the number of dorsal intercostal arteries supplied by the costocervical trunk and the highest intercostal artery is not consistent from animal to animal. In this study, it varied from four to seven on each side with only the first and occasionally the second one coming directly from the costocervical trunk and the remainder from the highest intercostal artery. There are typically 12 pairs of dorsal intercostal arteries, and the rest are direct branches from the thoracic aorta. Dorsal intercostal arteries were described as paired segmental branches with an independent origin arising from the thoracic aorta (Nejedly 1965; Popesko 1990). Shively and Stump (1975) described two types of origin of seven pairs of lumbar arteries from the abdominal aorta: an independent origin and one from the common trunk of the arteries at the same level. Other authors found the lumbar arteries as segmental paired branches arising from the dorsal surface of the abdominal aorta (Nejedly 1965; Popesko 1990). Dogs, rats, pigs, rabbits and mice have been used as experimental animals in the study of ischemic spinal cord
Spinal cord arteries in guinea pig
damage. In dogs, high variability was described in the density of the arteries forming the spinal arterial ring and in the frequency of occurrence of the spinal rami arising from the radicular arteries (Pais et al. 2007). Rat is one of the most used experimental animals in the study of spinal cord injury; therefore, the blood supply of the rat spinal cord is probably the most profusely documented, but the results differ (Brightman 1956; Woollam and Millen 1955; Soutoul et al. 1964; Schievink et al. 1988). Commonly two dorsal spinal arteries have been found in the rat (Lazorthes et al. 1971), but in albino Wistar rats, they were less constant (Woollam and Millen 1955). The variations and presence of the extrasegmental arteries of the spinal cord blood supply have been described in the pig (Strauch et al. 2003). In the rabbit, the variability of the spinal cord blood supply was described in all segments of the spinal cord. The presence of ventral and dorsal branches of the spinal arteries in the cervical segment of the spinal cord in rabbits was observed on the right side in 46.2 % of cases and on the left side in 53.8 % of cases. Along the entire thoracolumbar segment of the spinal cord in rabbit, the ventral branches of the spinal arteries were left sided in 62.5 % of cases and right sided in 37.5 % of cases (Mazensky et al. 2011), and the dorsal branches were left sided in 56.5 % of cases and right sided in 43.5 % of cases (Mazensky et al. 2013). In the mouse, the spinal cord blood supply has only been partially described (Lang-Lazdunski et al. 2000). On the dorsal surface of the spinal cord we found two or three irregular longitudinal dorsal spinal arteries (in humans the posterior spinal arteries). In humans, the posterior spinal arteries are normally continuous in the cranial to caudal direction (Cheshire et al. 1996). In dogs, four dorsal spinal arteries were described on the dorsal surface of the spinal cord. These were divided into two pairs. Each pair was formed by a larger caliber lateral dorsal spinal artery and a thinner medial dorsal spinal artery (Pais et al. 2007). Two much less constant dorsal spinal arteries forming irregular connections between each other were described in rats (Woollam and Millen 1955). The dorsal spinal arteries in the cervical segment of the spinal cord in rabbit were present in numbers of two or they were absent (Mazensky et al. 2012), and in the thoracolumbar segment they were present in numbers of two or three or were absent (Mazensky et al. 2013). The number of dorsal spinal arteries in mouse differs from study to study. Lang-Lazdunski et al. (2000) found two dorsal spinal arteries, but Bilgen and Al-Hafez (2006) described only one single artery. Our results indicate high variability in the presence of dorsal and ventral branches supplying blood to the spinal cord. On the left side, they occurred in higher numbers. The segmental arteries of the thoracic and lumbar part of the spinal cord ensured the supply of the respective
segments of the ventral spinal artery and dorsal spinal artery. Segmental arteries in the lumbar part of the spinal cord occurred irregularly, and their absence was noted more frequently than in the thoracic part, which allowed us to assume a higher risk of irreparable ischemic damage to the lumbar part of the spinal cord in the guinea pig. Till now, only sporadic published works have dealt with the study of the spinal cord blood supply in guinea pigs. Soutoul et al. (1964) studied the spinal cord blood supply in several species, but the presence of the artery of Adamkiewicz, its level of origin and the frequency of the occurrence of spinal branches in the guinea pig have not been described. Knox-Macaulay et al. (1960) only described the number of radicular arteries in the thoracic part of the spinal cord as five to seven and in the lumbar part noticed a great variation in the number. The ventral spinal artery was described as a vessel sometimes interrupted in its course. We found this artery to be an uninterrupted trunk. The dorsal spinal arteries were seen as two smaller anastomotic chains of arteries running in the dorsolateral sulcus. In our study, the number of dorsal spinal arteries varied from two to three. In this study, the artery of Adamkiewicz was described as a double artery originating from the spinal branch of the third or fourth lumbar artery. We found the artery of Adamkiewicz as a single or double vessel with different levels of origin. The artery of Adamkiewicz was only present in half of the dog specimens (Pais et al. 2007). In rat, the artery of Adamkiewicz was described in all cases (Brightman 1956; Woollam and Millen 1955; Soutoul et al. 1964; Gouaze´ et al. 1965), but many works doubt the presence of the artery of Adamkiewicz in rat (Tveten 1976; Schievink et al. 1988). In pig, the artery of Adamkiewicz was not recorded (Strauch et al. 2003, 2007). In rabbit, the artery of Adamkiewicz was described as left sided in 50 % of cases and right sided in 50 % of cases (Mazensky et al. 2011). The presence of the artery of Adamkiewicz was also described in the mouse (Lang-Lazdunski et al. 2000). In humans, the artery of Adamkiewicz is always present (Milen et al. 1999). Animal models, especially rodent models, are designed to help predict the functional outcomes of neurological disorders and injuries. Many of the behavioral outcomes appear in parallel to the clinical symptoms observed in human patients to a remarkable degree. Understanding the strengths and limitations of the models will allow more relevant analysis of the injury, behavioral sequelae and therapeutic approaches. Each aspect of a study should be planned before the experiment is begun (Geissler et al. 2013). Understanding the vascular blood supply to the spinal cord is important to avoid spinal cord ischemia or infarction during surgical approaches to the spine (Gao et al. 2013). The presence of the artery of Adamkiewicz
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D. Mazensky et al.
and nearly regular segmental blood supply of the thoracolumbar part of the spinal cord in all of our studied animals is the reason for using guinea pigs as a simple model of ischemic damage of the thoracolumbar part of the spinal cord. Acknowledgments The present study was carried out within the framework of project VEGA MSˇ SR no. 1/0111/13 of the Slovak Ministry of Education. Conflict of interest The authors have no financial or personal relationships related to the article. The authors declare no conflict of interest.
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