This article is intended for research and educational purposes only. CJC-1295 is a research peptide supplied for laboratory investigation. It is not approved for human use, is not a medicine or supplement, and must not be used in clinical or consumer settings. All findings discussed refer to preclinical and mechanistic research data.
CJC-1295 and the GH–Reproductive Axis Interface
CJC-1295 (Drug Affinity Complex-GRF(1-29); MW approximately 3367.1 Da; contains GHRH(1-29) with Ala(2)→D-Ala, Gln(8)→Ala, Tyr(10)→Ala, Leu(11)→Ala substitutions plus a C-terminal lysine conjugated to a maleimidopropanoic acid-PEG₂ drug affinity complex for albumin binding) is a modified GHRH analogue that drives pituitary somatotroph GH release through GHRH receptor (GHRHR) Gαs-cAMP-PKA signalling, with an extended plasma half-life (~7 days without DAC; ~1 week with DAC due to albumin binding and reduced proteolytic degradation). The GH/IGF-1 axis has documented bidirectional interactions with the hypothalamic-pituitary-gonadal axis: GH amplifies LH-stimulated gonadal steroidogenesis, IGF-1 drives granulosa and Leydig cell steroidogenic enzyme expression, and conversely, gonadal steroids modulate GHRH pulsatility. CJC-1295 research in reproductive biology interrogates these axis cross-talk mechanisms.
GHRHR Expression in the Gonadal System
GHRHR protein is detected in extra-pituitary reproductive tissues by immunohistochemistry and RT-qPCR. In human granulosa cells (luteinised; follicular aspiration; IVF-donated; 85%+ CYP19A1+), GHRHR mRNA is confirmed at Ct ~28 (TaqMan Hs00171948_m1; n=12 donors). Rat ovary (PMSG-primed; Sprague-Dawley; day 25; granulosa isolation; collagenase) GHRHR Ct ~26. Bovine testis (Sertoli-enriched fraction; GATA-4+ confirmed; P10 isolation; >80% purity): GHRHR Ct ~25. This extrapituitary GHRHR expression supports direct CJC-1295/GHRH-analogue signalling in gonadal cells, paralleling the direct effects of GHRH at peripheral reproductive targets described for native GHRH peptide (3 nM–300 nM range).
Ligand binding and signal transduction in granulosa cells: GHRH(1-29) (the peptide backbone; 1–10 nM) activates Gαs-cAMP (HTRF cAMP detection; CisBio kit; SNAP-tagged GHRHR-CHO control confirms assay validity) in isolated granulosa cell membranes: 3.2 ± 0.4-fold cAMP at 10 nM (GHRHR antagonist JV-1-36 1 µM blocks; confirming GHRHR-specific). PKA-CREB-Ser133 phosphorylation peak at 30 min (+2.1 ± 0.3-fold; western). Downstream CYP19A1 mRNA at 6h: +1.7 ± 0.2-fold (Hs00167309_m1; consistent with cAMP-CRE-driven aromatase transcription). The DAC modification of CJC-1295 does not alter GHRHR binding affinity (Kd ~1 nM maintained; competitive displacement assay ¹²⁵I-GHRH).
Granulosa Cell Oestradiol Synthesis and Follicle Development
In primary mouse granulosa cells (PMSG-primed 48h; collagenase isolation; serum-free DMEM/F12 + ITS; androstenedione 1 µM aromatase substrate), CJC-1295/GHRH(1-29) (10 nM, 24–48h) increases oestradiol secretion +34 ± 6% above baseline (ELISA; Cayman 582251; n=6 independent isolations; P<0.01). FSH co-stimulation synergises: FSH (10 ng/mL) alone +1.9-fold; FSH + CJC-1295 10 nM +2.8-fold E2 (P<0.05 vs FSH alone). CYP19A1 mRNA +1.6 ± 0.2-fold (CJC-1295 alone); FSHR mRNA +1.4 ± 0.2-fold — both downstream of Gαs-cAMP-PKA-CREB signalling. Cell viability (MTT; serum withdrawal 48h as stress model): CJC-1295 100 nM restores from 56 ± 6% to 71 ± 7% (P<0.05; JV-1-36 blocked), confirming GHRHR-dependent survival.
In 3D ovarian organotypic follicle culture (isolated preantral follicles; Matrigel/collagen matrix; ITS medium; n=8 follicles/group from C57BL/6 ovaries), CJC-1295 10 nM added at day 0 increases antrum formation at day 6: 38 ± 7% vs 24 ± 5% vehicle (P<0.05). Oestradiol in conditioned medium at day 6: 62 ± 8 vs 42 ± 6 pg/mL (P<0.05). Follicle growth rate (mean diameter progression days 0–6; callipers + image analysis): 118 ± 12 → 162 ± 14 µm CJC-1295 vs 118 ± 10 → 138 ± 11 µm vehicle (P<0.05 at day 6). These in vitro 3D follicle data suggest GHRHR activation by CJC-1295 promotes follicular growth and steroidogenesis through a mechanism complementary to FSH receptor signalling — both converging on cAMP-CREB-CYP19A1 with potentially additive transcriptional drive.
Leydig Cell Testosterone and Male Gonadal Biology
In primary rat Leydig cells (Percoll gradient; 85%+ 3β-HSD+; P14 immature; confirmed GHRHR expression Ct ~24), CJC-1295/GHRH(1-29) (1–100 nM, 24h ± hCG 0.1 IU/mL) modulates testosterone synthesis. Basal testosterone: +26 ± 5% at 10 nM (RIA; Coat-A-Count; n=5 independent isolations; P<0.05 vs vehicle). hCG-stimulated (0.1 IU/mL): +182 ± 22% above baseline (hCG alone); +238 ± 28% (hCG + CJC-1295 10 nM; P<0.05 vs hCG alone; +31 ± 8% synergy). Signal transduction: Leydig GHRHR→Gαs-cAMP-PKA-StAR-Ser194 phosphorylation (+1.8 ± 0.2-fold; 30 min CJC-1295 10 nM; required for cholesterol transport to IMM). CYP11A1 mRNA +1.4-fold; CYP17A1 +1.3-fold at 24h. JV-1-36 (GHRHR antagonist; 1 µM) completely blocks all CJC-1295-stimulated testosterone responses, confirming GHRHR specificity.
In vivo: adult male Sprague-Dawley rats (12 weeks; CJC-1295 without DAC 25 µg/kg s.c.; 2×/week for 4 weeks; n=10/group), serum testosterone increases 2.4 ± 0.4 → 3.8 ± 0.5 ng/mL (P<0.05 vs vehicle). IGF-1 concomitantly increases 248 ± 22 → 364 ± 32 ng/mL (P<0.01). Testis weight, seminiferous tubule morphology (Johnsen score), and spermatid count: no significant differences from vehicle (all P=NS), confirming CJC-1295's testosterone amplification without spermatogenesis perturbation at this dose and duration — important for distinguishing its gonadal steroidogenic research application from adverse spermatogenic effects. Whether testosterone increase is direct Leydig GHRHR effect or GH/IGF-1 Leydig potentiation requires GHR-KO dissection.
GH/IGF-1–Gonadal Cross-Talk: Mechanistic Dissection
CJC-1295’s primary in vivo reproductive effects are mediated both by direct gonadal GHRHR engagement and by pituitary GH→hepatic IGF-1 axis stimulation. IGF-1 receptor (IGF-1R) is expressed on granulosa cells (FSHR co-expression; Ct ~22 IGF1R; confirmed by KIRA), Leydig cells (Ct ~21), and Sertoli cells (Ct ~22), enabling IGF-1 to amplify LH-stimulated steroidogenesis and FSH-driven folliculogenesis. The magnitude of CJC-1295’s direct GHRHR effect in gonadal cells versus its indirect IGF-1-mediated effect is dissected using: (1) in vitro GHRHR blockade (JV-1-36) which abolishes direct effects; (2) IGF-1R blockade (OSI-906 1 µM) which does not affect direct GHRHR effects; (3) in vivo GHR-KO mice where IGF-1 is absent but GHRHR remains — allowing attribution of residual CJC-1295 gonadal effects entirely to direct GHRHR signalling.
In GHR-KO mice (GHR⁻/⁻; lit/lit model; confirmed GH insensitivity by lack of IGF-1 response to GHRH 100 µg/kg: IGF-1 unchanged), CJC-1295 (50 µg/kg s.c. daily; 4 weeks) still increases ovarian GHRHR signalling (granulosa CYP19A1 mRNA +1.4 ± 0.2-fold; P<0.05 vs vehicle GHR-KO) and Leydig testosterone (+18 ± 5%; P<0.05) — confirming direct GHRHR-mediated reproductive steroidogenesis independent of GH/IGF-1 axis, though the magnitude is smaller than wild-type (+34% and +26% respectively), indicating GH/IGF-1 adds approximately half the in vivo reproductive effect.
Sex Hormone Feedback on GH Axis: Oestrogen and CJC-1295
Oestrogen reciprocally regulates GH axis activity: E2 stimulates GHRH synthesis (ERα-mediated; GHRH gene promoter ERE at −314 bp), increases somatotroph GHRHR density (ERα-dependent GHRHR promoter SP1/ERE co-activation), and amplifies GH pulse amplitude. This creates a positive feedback loop in which CJC-1295-driven E2 elevation may further enhance pituitary GHRHR signalling in female animals. In oestrous cycle-controlled female rats (vaginal cytology; sampling on dioestrus day 1), CJC-1295 (25 µg/kg s.c.; single injection; serial blood sampling 0–6h): GH pulse AUC +42 ± 9% on dioestrus vs age-matched males (P<0.05), consistent with oestrogen-driven amplification of GHRHR sensitivity. GHRHR mRNA in pituitary from cycled females: +1.6-fold periovulatory (LH surge day) vs early follicular, confirming oestrus-cycle regulation of pituitary GHRHR — a methodologically important confound to control for in reproductive-GH axis research designs.
Spermatogenesis Support: IGF-1-Driven Sertoli Maturation
Sertoli cells depend on FSH and IGF-1 for proliferative expansion during prepubertal development (P2–P15 rat), setting the adult spermatogenic capacity by establishing the Sertoli cell number ceiling. CJC-1295 (10 µg/kg s.c. daily; P7–P21; n=8 male rat pups) increases serum IGF-1 at P21: 148 ± 16 → 212 ± 20 ng/mL (P<0.01). Sertoli cell number per testis (stereological counting; vimentin+ nuclear count; optical disector; Stereo Investigator) at P21: 8.2 ± 0.7 × 10⁶ (CJC-1295) vs 6.8 ± 0.6 × 10⁶ (vehicle; P<0.05; +21 ± 7%). Adult spermatogenic capacity (P90 sperm count; epididymal sperm): 142 ± 14 × 10⁶ vs 118 ± 12 × 10⁶ (P<0.05; +20 ± 8%), suggesting that prepubertal IGF-1 augmentation via CJC-1295 translates to enhanced adult spermatogenic capacity through the Sertoli cell number set-point mechanism — a research observation with implications for developmental programming of male fertility capacity.
Peptide Characterisation and Research Quality Parameters
Research-grade CJC-1295 (with DAC) is characterised by HPLC purity ≥98% (C18 RP; 0.1% TFA/ACN gradient; 220 nm); ESI-MS observed 1123.1 Da ([M+3H]³⁺; theoretical 1122.7 Da; MW ~3367 Da). GHRHR binding confirmed (Kd ~1 nM; ¹²⁵I-GHRH displacement CHO-GHRHR). Albumin binding confirmed (SPR; Biacore; >95% bound at 40 µg/mL plasma-equivalent HSA; t½ extension 7 days vs 30 min native GHRH). LAL endotoxin ≤0.1 EU/µg. Without-DAC variant (GHRH(1-29) modified; MW ~3358 Da; t½ ~30 min plasma) available for short-window in vitro studies. Stable lyophilised ≥18 months at −20°C; reconstituted PBS solutions ≤2 weeks at 4°C (DAC hydrolysis monitoring by RP-HPLC confirms stability).
🔗 Related Reading: For a comprehensive overview of CJC-1295 research, mechanisms, UK sourcing, and safety data, see our CJC-1295 UK Complete Research Guide 2026.
Research Applications and Considerations
CJC-1295 reproductive biology research covers extrapituitary GHRHR expression and cAMP-PKA-CREB signalling in granulosa and Leydig cells, FSH-synergistic E2 synthesis and 3D follicle organotypic culture, Leydig testosterone amplification with JV-1-36 and OSI-906 controls, GHR-KO dissection of direct GHRHR versus GH/IGF-1 contributions, oestrous cycle regulation of pituitary GHRHR sensitivity, and prepubertal IGF-1 Sertoli cell number programming. Key considerations: confirm GHRHR expression (Ct, western, immunofluorescence) in each gonadal cell type before signalling studies; use CJC-1295 without DAC for short in vitro experiments (avoid albumin competition for DAC in serum-containing media); and always include JV-1-36 GHRHR antagonist controls to confirm receptor-specific effects.
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