Table 1. Review of select in vivo models of arteriogenesis.

Reported are the methods of inducing arteriogenesis in skeletal muscle, animal used, specific techniques employed relevant to visualization of vasculature and tissue perfusion, spatial resolution of intact vascular network (smallest quantifiable vessel diameter; NA for sectioning techniques because spatial detail is lost), smallest quantifiable vessel diameter, mode of identifying a collateral artery (CA), mode of identifying monocytes/macrophages, and qualitative observation of CA tortuosity. Included also are excerpts from the text on how arteriogenesis was defined. This table reflects the flexibility and strengths of the hindlimb ischemia models for the study of arteriogenesis. They have been instituted in numerous animals, and the severity of the injury can be varied through placement of ligation and/or excision of vessel segments. There are also numerous techniques available for the visualization of the vasculature and for the identification of collateral arteries, as well as infiltrated monocytes/macrophages. This table also highlights potential problems that arise when spatial detail is lost. For example, while arteriogenesis is typically defined as the remodeling of pre-existing arcade arterioles (collateral anastomoses), sectioning eliminates the ability to differentiate between transverse and arcade arterioles, and so this distinction on the microscale is not easily made with these models. Abbreviations are as follows—CA: collateral artery; LDPI: Laser Doppler Perfusion Imaging; MRI: Magnetic Resonance Imaging; Longland’s classification: vessels must show a defined stem, midzone, and re-entry to be classified as collateral arteries.

	Arteriogenesis model	Animal	Dominant techniques	Spatial lower limit of intact network	Vessel diameter lower limit	Identification of CA	Identification of monocytes & macrophage	Tortuosity of CA
Arras et al., 1998	hindlimb; bilateral femoral artery ligation	New Zealand White rabbit	sectioning	NA	capillary	size & morphology	RAM11+ (DAKO A/S)	NA
“in situ proliferation of pre-existing arteriolar connections into true collateral arteries…named arteriogenesis”
Bergmann et al., 2006	hindlimb; femoral artery ligation	op/op mouse	sectioning; angiography; microsphere perfusion	Relative and variable (~100 μm)	~15 μm arterioles	Longland’s classification; αSMA+	MOMA-2+ (BMA Biomedicals); F4/80+ (Caltag labs)	corkscrew appearance
“arteriogenesis is the growth of pre-existent collateral anastomoses into functional conductance arteries”
Brown et al., 2003	hindlimb; common iliac artery ligation	Sprague-Dawley rat	sectioning	NA	< 10 μm arterioles	αSMA+ (included all vessels)	ED1+ & ED2+ (Serotec)	NA
“…development of collateral arteries by enlargement of pre-existing connections, often referred to as arteriogenesis….”
Couffinhal et al., 1999	hindlimb; femoral artery ligation	ApoE−/us;mouse	sectioning; LDPI	NA	capillary	CD31+ capillary	F4/80+ (Caltag Labs)	NA
Not defined. Model of inferential collateral vessel growth via increased capillary density.
Heil et al., 2004	hindlimb; femoral artery ligation	CCR2−/− mouse	LDPI; MRI; sectioning	~100 μm	CA size not explicitly defined	αSMA+	murine MAC-3 (BD Biosciences)	NA
“collateral artery growth (arteriogenesis)”
Hoefer et al., 2004	hindlimb; femoral artery ligation	rabbit; ICAM-1−/− & MAC-1−/− mouse	angiography; sectioning	~100 μm	~15 μm arterioles	Longland’s classification in angiograms; Ki-67+ (proliferating) vessels in sections	MOMA-2+ (BMA Biomedicals)	corkscrew-like collaterals
“In the event of arterial occlusion…a steep pressure gradient develops along the shortest path within the interconnecting network that increases blood flow velocity and hence fluid shear stress in these vessels that now assume their new function as CA. These vessels then grow to provide enhanced perfusion to the jeopardized ischemic regions. This adaptive process is termed arteriogenesis and refers to active proliferation and remodeling rather than passive dilatation.”
Hoefer et al., 2005	hindlimb; femoral artery ligation	New Zealand, White rabbit	sectioning; angiography; microsphere perfusion	~100 μm	~15 μm arterioles	Ki-67+ (proliferating) & αSMA+	CD68+ (DAKO); CD11b+ (Serotec)	not reported
“…large pressure gradient[s] over…pre-existing collateral anastomoses initiate vascular proliferation. The anastomoses with the lowest vascular resistance mature to functional arteries ensuring perfusion of the jeopardized ischemic regions. This process is referred to as arteriogenesis”
Kinnaird et al., 2004	hindlimb; femoral artery ligation	Balb/C mouse	LDPI; sectioning	NA	capillary	Van Gieson solution; continuous internal elastic laminae (morphology)	NA	NA
“…enhanced perfusion of ischemic tissue and collateral remodeling…”
Scholz et al., 1999	hindlimb; femoral artery ligation	New Zealand White rabbit	electron microscopy; sectioning;	NA	capillary	morphology; lower-limit of CA diameter at 100 μm	CD68+ (DAKO)	NA
“…arteriogenesis is the growth of collateral arteries from pre-existing arterioles in adults.”
Song et al., 2002	hindlimb; ultrasound-induced microbubble destruction	Sprague-Dawley rat	sectioning; microsphere perfusion	NA	capillary	αSMA+ & lectin+	NA	NA
“…formation and remodeling of arterioles, the process denoted as arteriogenesis…. This response consists of both the formation of new arterioles, which presumably occurs when preexisting capillaries acquire an SM coating, and an increase in the diameter of these newly formed and/pr preexisting arterioles into channels with larger diameters.”
Stabile et al., 2004	hindlimb; femoral artery ligation	C57/Bl6; CD8a−/− mouse	LDPI; sectioning	NA	capillary	Van Gieson solution; continuous internal elastic laminae + layer of muscle spindles + area > 300μm2	CD4+ (Santa Cruz)	NA
“One of the compensatory mechanisms involved in the response to impaired blood flow secondary to atherosclerotic plaque development is the formation of collateral blood vessels. It has recently been shown that cellular components of the immune and inflammatory systems play a pivotal role in modulating collateral vessel development…[or] collaterogenesis.”
Tang et al., 2004	hindlimb; excision of femoral artery	CCR2−/− mouse	LDPI; angiography; sectioning	~200 μm	capillary	CD31+ & αSMA+	MOMA-2 (Serotec)	not reported
“…collateral artery development, or arteriogenesis….”
Takeshita et al., 1998	hindlimb; excision of femoral artery	Wistar rat	micro-angiography; microsphere perfusion	30 μm	30 μm	morphology & location	NA	tortuous, corkscrew, as well as linear
Inconsistently defined