Table A1.
Histology Grading Rubric.
| Category | Score | Features | Category | Score | Features |
|---|---|---|---|---|---|
| NP Damage |
0 | Physaliferous cells(+), diffuse/nonfibrotic matrix | Induced Bone Extent |
0 | No Induced Bone (IB) |
| 1 | PF(-), NP now smaller rounded cells, matrix fibrous stranding (PSR(+) staining) not prominent | 1 | Sparse IB ventral to AF, ± connection to VB (EP-OP/ALL calcification/ossification) | ||
| 2 | PF(-), small rounded cells, prominent PSR(+) matrix | 2 | Thick IB with organized bone marrow compartment, ventral to AF, but not fused (partially spanning OP) |
||
| AF Damage |
0 | Organized lamellae, no clefts | |||
| 1 | Wavy/bulging lamellae, mild clefts in outer AF | 3 | IB spanning entire IVD and connecting VBs (IVD fusion) | ||
| 2 | Severe lamellae disorganization/bulging, severe clefts | NP Blood Vessel Structure or Staining Observed |
0 | Structures resembling blood vessels ± RBCs, or anti-VEC/anti-CD31+ immunostaining in only non-induced tissues: VBs, EPs, ALL, PLL, or perivertebral muscle. | |
| IVD Interface Damage |
0 | Normal NP/EP & AF/NP | |||
| 1 | Loss of NP/EP interface | ||||
| 2 | Loss of AF/NP interface | ||||
| IVD PG Damage |
0 | Normal Alcian Blue staining | 1 | Collagen-containing (PSR+) structures resembling blood vessels/RBCs, and or (+) vascular immunostaining cells seen in induced tissues (in VBs or EPs but not into the NP | |
| 1 | Reduced AB staining (>50% of control) | ||||
| 2 | Faint blue to no AB staining (<50% of control) |
||||
| 2 | Blood vessels/vascular immunostain observed crossing into the NP |
Histology definitions for assessment of osteogenesis, angiogenesis and IVD damage present in lumbar discs at 12 weeks following intradiscal injection of naïve, or gene-programmed bone marrow stromal cells with or without chABC protein. Lumbar levels L4/5 and L5/6 were considered separately, and scores for osteogenesis, angiogenesis and damage were summed for statistical testing. PF = physaliferous cells in the NP, PSR = picrosirius red staining, AF = annulus fibrosus, NP = nucleus pulposus, EP = endplate, VB = vertebral body, AB = Alcian Blue, PG = proteoglycan, IVD = intervertebral disc, IB = induced bone, OP = osteophyte, ALL = anterior longitudinal ligament, BM = bone marrow, RBCs = red blood cells, VEC = vascular endothelial cadherin, and PLL = posterior longitudinal ligament.